REVIEW article

Front. Oncol., 29 November 2021

Sec. Molecular and Cellular Oncology

Volume 11 - 2021 | https://doi.org/10.3389/fonc.2021.777849

A Review on the Role of AFAP1-AS1 in the Pathoetiology of Cancer

  • 1. Department of Medical Genetics, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran

  • 2. Phytochemistry Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran

  • 3. Department of Pharmacognosy, College of Pharmacy, Hawler Medical University, Erbil, Iraq

  • 4. Urology and Nephrology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran

  • 5. Institute of Human Genetics, Jena University Hospital, Jena, Germany

  • 6. Skull Base Research Center, Loghman Hakim Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran

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Abstract

AFAP1-AS1 is a long non-coding RNA which partakes in the pathoetiology of several cancers. The sense protein coding gene from this locus partakes in the regulation of cytophagy, cell motility, invasive characteristics of cells and metastatic ability. In addition to acting in concert with AFAP1, AFAP1-AS1 can sequester a number of cancer-related miRNAs, thus affecting activity of signaling pathways involved in cancer progression. Most of animal studies have confirmed that AFAP1-AS1 silencing can reduce tumor volume and invasive behavior of tumor cells in the xenograft models. Moreover, statistical analyses in the human subjects have shown strong correlation between expression levels of this lncRNA and clinical outcomes. In the present work, we review the impact of AFAP1-AS1 in the carcinogenesis.

Introduction

Actin filament-associated protein 1 antisense RNA 1 (AFAP1-AS1, NC_000004.12) is a long non-coding RNA (lncRNA) which contributes in the pathoetiology of several cancers (1). It is transcribed from AFAP1 gene locus on 4p16.1. It has two alternatively spliced variants. Its second exon overlaps with exons 14-16 of AFAP1 gene. The motor fiber-associated protein encoded by AFAP1 has been shown to organize a platform for joining a number of tumor-related proteins such as SRC and protein kinase C (2). This platform can influence the organization and activity of actin filaments, therefore participating in cytophagy, cell motility, invasive characteristics of cells and metastatic ability (3). Both AFAP1 and FAP1-AS1 participate in the carcinogenesis through modulation of related signaling pathways. AFAP1 has acknowledged roles in the pathogenesis of a number of cancers, namely breast (4) and prostate cancer (5), yet its expression has been found to decreased in gastric cancer samples (6). AFAP1-AS1 is mainly regarded as an oncogenic lncRNA (1). However, the oncogenic effect of this lncRNA is not necessarily exerted through AFAP1-dependent routes. A number of deletion type copy-number variants (CNVs) have been identified in AFAP1-AS1 coding gene through application of whole genome sequencing (7). AFAP1-AS1 has been shown to affect several aspects of carcinogenesis through modulation of expression of cancer-related miRNAs. Since it has been shown to be dysregulated in diverse types of cancer, this lncRNA is a putative marker for a wide variety of cancers. Functional impacts of AFAP1-AS1 in the carcinogenesis have been appraised through knock-down and over-expression studies in cell lines and animal models. Moreover, the impact of AFAP1-AS1 deregulation has been assessed in human samples. In the present review, we discuss the role of AFAP1-AS1 in the carcinogenesis based on the evidence from these three types of studies.

Cell Line Studies

Lung Cancer

AFAP1-AS1 has been found to be over-expressed in non-small cell lung cancer (NSCLC) cells H1975, PC-9, A549, and SPCA-1 compared with the human non-tumorigenic lung epithelial cell line BEAS-2B. Functional studies in these cells have confirmed the ability of this lncRNA in binding with and sequestering miR-139-5p, a down-regulated miRNA in NSCLC samples. AFAP1-AS1 silencing and miR-139-5p up-regulation could similarly inhibit proliferation, colony forming ability and chemoresistance of NSCLC cells, while increasing their apoptosis. The sequestering impact of AFAP1-AS1 on miR-139-5p leads to up-regulation of RRM2, a protein which has been demonstrated to increase chemoresistance of NSCLC cells via activation of EGFR/AKT pathway (8). Another study in NSCLC has shown up-regulation of FAP1-AS1 parallel with down-regulation of IL-12 and up-regulation of IL-10 and IFN-γ. Functionally, AFAP1-AS1 has been shown to induce activity of IRF7, RIG-I-like receptor signals and Bcl-2. Cumulatively, AFAP1-AS1 enhances migration and invasive properties of NSCLC cells through activating IRF7 and the RIG-I-like receptor signaling pathway (9). Moreover, the interaction between AFAP1-AS1 and EZH2 and subsequent recruitment of EZH2 to the promoter of p21 has been shown to repress expression of p21 in this type of cancer (10). AFAP1-AS1 has also been shown to enhance expression of AFAP1 in lung cancer cells. Expression of AFAP1-AS1 in lung cancer cells is regulated through CpG methylation marks in its promoter, since the DNA methyltransferase inhibitor agent decitabine has been demonstrated to activate AFAP1-AS1 expression. AFAP1-AS1 has been reported to increase expression levels of pro-invasive genes PPP1R13L, VASP and SPTAN1, while decreasing expression levels of a number of anti-metastatic genes such as STAT1, NF1, and FBN2 (11). Figure 1 summarizes the mentioned routes of participation of AFAP1-As1 in the pathogenesis of lung cancer.

Figure 1

AFAP1-AS1 can also affect lung cancer through a variety of other mechanisms being summarized in Figure 2. For instance, AFAP1-AS1 has been shown to regulate expression of numerous members of the small GTPase proteins as well as those participating in the actin cytokeratin signaling. Thus, the promoting effect of AFAP1-AS1 on cancer metastasis is most probably exerted through modulation of actin filament integrity (12). GTPases harmonize several cellular processes, such as cell polarity, migration, and cell cycle transition, thus they can participate in the pathogenies of cancer (13). Moreover, cytokeratins as members of intermediate filament protein family have been shown to affect carcinogenesis. They can also been used as cancer biomarkers (14).

Figure 2

AFAP1-AS1 can also enhance expression of HDGF through decreasing miR-545-3p levels in lung cancer cells. Thus, AFAP1-AS1 silencing could inhibit progression of lung cancer through influencing activity of miR-545-3p/HDGF axis (15). Finally, AFAP1-AS1 can interact with Smad nuclear interacting protein 1 (SNIP1), a protein which suppresses ubiquitination and subsequent destruction of c-Myc. This function of AFAP1-AS1 leads to over-expression of c-Myc, increase in ZEB1, ZEB2, and SNAIL levels, and enhancement of epithelial to mesenchymal transition (EMT) (16).

Breast Cancer

In breast cancer cells, AFAP1-AS1 silencing could decrease proliferation and migratory potential, and increase cell apoptosis. miR-497-5p has been recognized as a target of AFAP1-AS1 in breast cancer cells. Since this miRNA targets SEPT2, AFAP1-AS1 up-regulation results in up-regulation of SEPT2 (17). miR-145 is another target of AFAP1-AS1 in triple negative breast cancer cells (TNBC) MDA-MB-231 breast cancer cells. According to the results of luciferase reporter assay, miR-145 can directly target MTH1. Thus, the effects of AFAP1-AS1 in enhancement of proliferation and invasiveness of TNBC are exerted through miR-145/MTH1 axis (18). Moreover, in this type of cancer, AFAP1-AS1 can sequester miR-2110 to enhance expression of Sp1 (19). AFAP1-AS1 has also been shown to enhance EMT of TNBC cells via influencing Wnt/β-catenin signaling (20). Finally, AFAP1-AS1 has been found to have significant over-expression in trastuzumab-resistant breast cancer cells versus responsive cells. Expression of this lncRNA has been enhanced by H3K27ac at its promoter. Most notably, trastuzumab resistant cells have been shown to secrete AFAP1-AS1 into exosomes, thus disseminating trastuzumab resistance in other cells. The impact of exosomal AFAP1-AS1 in induction of trastuzumab resistance is exerted via its interaction with AUF1 and subsequent induction of ERBB2 translation (21). Figure 3 depicts the impact of AFAP1-AS1 in carcinogenesis and therapy resistance of breast cancer cells.

Figure 3

Osteosarcoma

In MNNG/HOS and U2OS osteosarcoma cells, AFAP1-AS1 has been found to promote tumorigenesis via influencing RhoC/ROCK1/p38MAPK/Twist1 cascade (22). The AFAP1-AS1-mediated increase in Twist1 can enhance expression of N-cadherin and Vimentin, while diminishing E-cadherin levels, thus promoting EMT of osteosarcoma cells (22). Moreover, AFAP1-AS1 can sequester miR-497 and miR-4695-5p in these cells, therefore increasing expressions of IGF1R and TCF4, respectively (23, 24). The latter can activate Wnt-β catenin pathway and increase both proliferation and invasive abilities of osteosarcoma cells (24). Figure 4 depicts the oncogenic role of AFAP1-AS1 in osteosarcoma.

Figure 4

Gastric Cancer

Similarly, AFAP1-AS1 has an oncogenic role in gastric cancer. AFAP1-AS1 silencing has significantly suppressed proliferation and cell cycle transition in this kind of cancer. Besides, reduction in the levels of this lncRNA can inhibit invasive capacity through affecting EMT (25). Down-regulation of KLF2 is another mechanism by which AFAP1-AS1 enhances proliferative and migratory aptitudes of gastric cancer cells (26). AFAP1-AS1 silencing in gastric cancer cells has led to a significant increase in the levels of Bax, cleaved PARP, Caspase 3, and Caspase 9, while decreasing Bcl-2 level. AFAP1-AS1 silencing has also reduced p-AKT levels and enhanced expression of PTEN in gastric cancer cells. Taken together, AFAP1-AS1 regulates proliferation and apoptotic processes in gastric cancer cell through PTEN/p-AKT cascade (27). AFAP1-AS1 can also promote proliferation and metastatic ability of gastric cancer cell through sequestering miR-155-5p and enhancing expression of FGF7 (28). Figure 5 shows the oncogenic role of AFAP1-AS1 in gastric cancer.

Figure 5

Esophageal Cancer

AFAP1-AS1 have also been shown to bind with miR-26a, therefore influencing expression of its target gene, i.e. ATF2. Exosomes originated from M2 macrophages have higher expression of AFAP1-AS1 and ATF2 and reduced expression of miR-26a, compared with M1 macrophages. These exosomes could transfer AFAP1-AS1 to esophageal cancer cells, thus downregulating miR-26a and enhancing ATF2 levels in the recipeint cells. These expression changes affect phenotype of esophageal cancer cells (29). The regulatory role of AFAP1-AS1 on miR-498/VEGFA axis is another mechanism of participation of this lncRNA in the pathetiology of esophageal cancer (30).

Other Types of Cancers

In prostate cancer cells, AFAP1-AS1 has been shown to promote sequester miR-195-5p (31) and miR-512-3p (32), thus affecting malignnat behavious of these cells.

A number of other miRNAs, namely miR-423-5p (33), miR-320a (34), miR-107 (35) and miR-384 (36) have been found to be sequestered by AFAP1-AS1 in different cancer tissues (Figure 6).

Figure 6

Table 1 summarizes the results of studies which appraised oncogenic roles of AFAP1-AS1 in different tissues.

Table 1

Tumor typeInteractionsCell linesEffectsReference
Non-small Cell Lung CancermiR-139-5p, RRM2, EGFR/AKT signaling pathwayH1975, PC-9, A549, SPCA-1, BEAS-2BΔ AFAP1-AS1: ↓ proliferation, ↓ chemo-resistance, ↑ apoptosis (8)
_A549, H1975, H1650, H1395, H12994 Δ AFAP1-AS1: ↓ proliferation ↑ AFAP1-AS1: ↑ invasion, ↑ migration, ↓ apoptosis (9)
p21, EZH216HBE, A549, SPC-A, H1299Δ AFAP1-AS1: ↓ proliferation, ↑ cell cycle arrest (10)
PPP1R13L, VASP, SPTAN1, STAT1, NF1, FBN2, AFAP1H1299, PC9, H1975, 293TΔ AFAP1-AS1: ↓ invasion, ↓ migration ↑ AFAP1-AS1: ↑ invasion, ↑ migration (11)
HBP116HBE, A549, SPC‐A1, PC‐9, H1299, H1975Δ AFAP1-AS1: ↓ proliferation, ↓ migration, ↑ G0/G1 cell cycle arrest, ↑ apoptosis (37)
Lung cancerAFAP1, KRT1A549, H1299 and H460, 95-D, 16HBEΔ AFAP1-AS1: ↓ proliferation, ↓ migration (38)
RhoA, Rac2, Rab10, Rab11a, Rhogdi proteins, Pfn1, RhoC, Rab11b, LIM, Lasp1A549Δ AFAP1-AS1: ↓ invasion, ↓ migration, ↓ metastasis (12)
miR-545-3p, HDGF_Δ AFAP1-AS1: ↓ proliferation ↓ invasion, ↓ migration, ↑ apoptosis (15)
SNIP1, c-Myc, ZEB1, ZEB2, SNAILA549, PC9Δ AFAP1-AS1: ↓ invasion, ↓ migration, ↓ EMT process (16)
_H1915, HCC827Δ AFAP1-AS1: ↓ invasion, ↓ growth, ↑ apoptosis (39)
Breast cancer (BC)_MCF-10A, MCF-7, SK-RB-3, MDA-MB231, MDA-MB-468Δ AFAP1-AS1: ↓ proliferation, ↓ colony formation, ↓ metastasis ↑ apoptosis, did not affect AFAP1 expression, did not affect actin filament integrity (40)
miR-497-5pHCC70, BT-549, MCF-7, MDA-MB-231, MCF-10AΔ AFAP1-AS1: ↓ proliferation, ↓ migration, ↑ apoptosis (17)
miR-145, MTH1, ATF6 MDA-MB-231, MDA-MB-468, MDA-MB-435S, and HCC1937, MCF-10AΔ AFAP1-AS1: ↓ viability, ↓ colony formation, ↓ invasion (18)
Wnt/β-catenin signaling pathway, C-myc, SLUG, SNAIL, vimentin, fibronectin, N-cadherin, E-cadherin184A1, MCF-10A, BT474, MCF-7, T47D, BT483, BT20, MDA-MB-468, BT549, MDA-MB-231Δ AFAP1-AS1: ↓ proliferation ↓ invasion, ↓ migration, ↓ EMT process, ↑ apoptosis (20)
miR-2110, Sp1MCF-10A, BT-549, MDA–MB-468 Δ AFAP1-AS1: ↓ proliferation ↓ invasion, ↓ migration (19)
ERBB2, AUF1KBR-3, BT474, Δ AFAP1-AS1: ↓ trastuzumab resistance (21)
OsteosarcomaTwist1, N-cadherin and Vimentin, E-cadherin, RhoC/ROCK1/p38MAPK signaling pathwayMNNG/HOS, MG63, SaOS-2, hFOB 1.19Δ AFAP1-AS1: ↓ proliferation, ↓ invasion, ↓ migration, ↓ actin filament integrity, ↓ EMT process, ↓ VM formation capacity, ↑ apoptosis, ↑ G0/G1 cycle arrest (22)
miR-497, IGF1RMG-63, 143B, U2OS, Saos-2, hFOB 1.19Δ AFAP1-AS1: ↓ proliferation ↓ invasion, ↓ migration, ↑ apoptosis, (23)
miR-4695-5p, TCF4, Wnt/β-catenin pathwayhFOB 1.19, Saos-2, U2OS, MG-63, 143BΔ AFAP1-AS1: ↓ proliferation ↓ invasion (24)
Esophageal cancer (EC) miR-26a, ATF2PBMCs, KYSE410Δ AFAP1-AS1 in M2 Macrophage-Derived Exosomes: ↓ invasion, ↓ migration, ↓ metastasis (29)
miR-498, VEGFA HET-1A, Eca109, KYSE-30Δ AFAP1-AS1: ↓ proliferation, ↓ Migration, ↑ apoptosis (30)
_ECA‐109, TE‐1, HEECΔ AFAP1-AS1: ↓ proliferation, ↑ apoptosis  (41)
_OE-33, SK-GT-4, FLO-1, HEEpicΔ AFAP1-AS1: ↓ proliferation, ↓ invasion, ↓ anchorage-dependent growth did not affect the expression level of AFAP1 (42)
Gastric cancer (GC)KLF2, EZH2GES-1, AGS and SGC-7901Δ AFAP1-AS1: ↓ proliferation, ↓ invasion, ↓ viability, ↑ apoptosis  (26)
intrinsic pathway, PTEN/p-AKT PathwayAGS, MGC-803, SGC-7901, BGC-823, GES-1Δ AFAP1-AS1: ↓ proliferation, ↑ apoptosis  (27)
_MKN-45, MGC-803 and AGSΔ AFAP1-AS1: ↓ proliferation, ↓ migration, ↓ invasion, ↑ G0/G1 phase arrest, ↑ apoptosis  (43)
_AGS, BGC823, MGC-803, SGC-7901, GES-1Δ AFAP1-AS1: ↓ proliferation, ↓ invasion, ↓ EMT process, ↓ cell cycle progress (25)
miR-155-5p, FGF7MKN-28, BGC-823, MGC-803, SGC-7901, GES-1Δ AFAP1-AS1: ↓ proliferation, ↓ migration, ↓ invasion (28)
_GES-1, HGC-27, MGC-803, BGC-823, SGC-7901Δ AFAP1-AS1: ↓ proliferation, ↓ migration, ↓ invasion (44)
_GES-1, AGS, BGC-823, MKN-45, SGC-7901Δ AFAP1-AS1: ↓ proliferation, ↓ migration, ↓ invasion, ↓ EMT process (45)
Prostate cancermiR-195-5p, FKBP1APC3, DU145Δ AFAP1-AS1: ↑ PTX sensitivity, ↑ apoptosis, ↓ migration, ↓ invasion (31)
miR-512-3p22RV1Δ AFAP1-AS1: ↓ proliferation, ↓ migration, ↓ invasion, ↑ G0/G1 phase arrest (32)
Nasopharyngeal carcinoma (NPC)YAP, KAT2B, RBM3HNE-1, C666-1, SUNE-1, CNE-1, CNE-2, NP69Δ AFAP1-AS1: ↓ proliferation (46)
miR-423-5p, Rho/Rac signaling, FOSL2, LASP15-8F, HNE2 ↑ AFAP1-AS1: ↑ migration, ↑ invasion (33)
AFAP1, RhoA, Rac2, Rab10, Rab11a, Rhogdi, Pfn1, RhoC, Rab11b, Lasp15-8F, HNE2 and HK-1 Δ AFAP1-AS1: ↓ migration, ↓ invasion, ↓ stress filament integrity (47)
Endometrial carcinoma (EC)miR-545-3p, VEGFAIshikawa, HEC-1-B, HEC1-A, AN3-CA, hEEC,Δ AFAP1-AS1: ↓ proliferation, ↓ migration, ↓ invasion, ↓ angiogenesis (48)
Cholangiocarcinoma (CCA)AFAP1HuCCT1, TFK-1, HIBEpicΔ AFAP1-AS1: ↓ proliferation, ↓ migration, ↓ invasion, ↓ stress filament integrity  (49)
MMP-2, MMP-9QBC939, CCLP1, HuCC-T1 and RBE, BEC, 293TΔ AFAP1-AS1: ↓ proliferation, ↓ migration, ↓ invasion, ↑ G0/G1 phase arrest (50)
Colorectal cancer (CRC)GAS8-AS1CR4 (Sigma-Aldrich, USA), RKO (ATCC, USA)↑ AFAP1-AS1: ↑ proliferation (51)
_HCT116, SW480Δ AFAP1-AS1: ↓ proliferation, ↑ G0/G1 phase arrest (52)
AFAP1HCT116, SW480Δ AFAP1-AS1: ↓ proliferation, ↓ migration, ↓ invasion (53)
EZH2LOVO, SW1116, SW480, HCT116, SW620, HT29Δ AFAP1-AS1: ↓ proliferation, ↑ cell-cycle arrest (54)
Colon canceractin-cytokeratin signaling pathway, E-cadherin, vimentin, MMP9, ZEB1, ZO-1, β-cateninSW480, SW620, HCT116, HT-29Δ AFAP1-AS1: ↓ proliferation, ↓ migration, ↓ invasion (55)
Hepatocellular carcinoma (HCC)N-cadherin, vimentin, E-cadherin, CRKL, Ras, MEK, c-JunHuh7, HepG2, HCCLM3, LO2 Δ AFAP1-AS1: ↓ proliferation, ↓ migration, ↓ invasion, ↓ EMT process (56)
RhoA/Rac2 signalingSMCC7721 and HepG2Δ AFAP1-AS1: ↓ proliferation, ↓ invasion, ↑ S phase arrest, ↑ apoptosis  (57)
_LO2, SMMC-7721, Bel-7402, MHCC-97 L, MHCC-97HΔ AFAP1-AS1: ↓ proliferation, ↓ migration, ↓ invasion (58)
Cervical cancer (CC)RhoA/Rac2 signaling, Vimentin, β-catenin, ZO-1ATCC no. CCL-2,Δ AFAP1-AS1: ↓ migration, ↓ invasion, ↓ EMT process (59)
Laryngeal carcinomamiR‐320a, RBPJ HEp‐2Δ AFAP1-AS1: ↓ stemness, ↓ cisplatin resistance, ↑ apoptosis  (34)
Thyroid cancer_K-1, TPC-1, SW579, FTC133, XTC-1, l Nthy-ori3-1Δ AFAP1-AS1: ↓ proliferation, ↓ migration, ↓ EMT process, ↑ apoptosis  (60)
Glioma_U87MG, U251, SHG-44, A172Δ AFAP1-AS1: ↓ invasion (61)
Ovarian cancer (OC)_SKOV3, OV90, TOV112D, ES2Δ AFAP1-AS1: ↓ proliferation, ↑ apoptosis ↑ AFAP1-AS1: ↑ proliferation (62)
miR-107, PDK4IOSE80, COV504, OVISE, OV90 and SKOV3Δ AFAP1-AS1: ↓ proliferation, ↓ migration, ↓ invasion (35)
Pancreatic cancer (PC)miR-384, ACVR1SW1990, Capan-1, AsPC-1, MIAPaCa-2, PANC-1, HPC-Y5Δ AFAP1-AS1: ↓ stemness (36)
ZEB1, N-cadherin, E-cadherin, MMP-2, MMP-9, Slug, SnailBxPC-3, PANC-1Oridonin-induced Δ AFAP1-AS1: ↓ proliferation, ↓ migration, ↓ EMT process, ↑ apoptosis, ↑ cell cycle arrest (63)
miR-133a, IGF1RAsPC-1, BxPC-3, PANC-1, PaCa-2 and SW1990 Δ AFAP1-AS1: ↓ proliferation, ↓ invasion, ↓ metastasis, ↑ apoptosis  (64)
EGFR/Akt signaling, miR‐146b‐5pASPC‐1, BxPC‐3, HPAC, MiaPaCa‐2, HPDE6‐C7CUB-induced Δ AFAP1-AS1: ↓ proliferation, ↑ cell cycle arrest (65)
Pancreatic ductal adenocarcinoma (PDAC) _Panc1, MIAPaCa-2, Capan2, SW1990, BXPC-3, HPDE6Δ AFAP1-AS1: ↓ proliferation, ↓ migration, ↓ invasion (66)
Renal cell carcinoma (RCC)PTEN/AKT signalingHK2, 786-O, Caki-1, ACHN, A498Δ AFAP1-AS1: ↓ proliferation, ↓ migration, ↓ invasion, ↓ EMT process (67)
Gallbladder cancer (GBC)_NOZ, H69, GBC-SD, SGC-996Δ AFAP1-AS1: ↓ proliferation, ↓ invasion, ↓ epithelial phenotype to mesenchymal phenotype (68)
Pituitary adenomamiR-103a-3p, PI3K/AKT Signaling PathwayGH3 and MMQΔ AFAP1-AS1 + miR-103a-3p inhibitor: ↑ proliferation, ↑ cell cycle progression, ↓ apoptosis (69)
PTEN/PI3K/AKT signaling pathwayGH3, MMQΔ AFAP1-AS1: ↓ proliferation, ↑ cell cycle arrest, ↑ apoptosis (70)
Melanoma miR-653-5p, RAI14, E-cadherin, N-cadherin, Ki67HEMa-LP, A375, M21, B16F10, SK-MEL-2Δ AFAP1-AS1: ↓ proliferation, ↓ migration, ↓ invasion (71)
Retinoblastoma _Weri-Rb1 and Y79, ARPE-19, HRMECsΔ AFAP1-AS1: ↓ proliferation, ↓ migration, ↓ invasion (72)
Tongue squamous cell carcinoma (TSCC)Wnt/β-catenin, SLUG, SNAIL1, VIM, CADN, ZEB1, ZEB2, and TWIST1SCC-15, Tca8113, SCC-4, SCC-9, CAL-27Δ AFAP1-AS1: ↓ proliferation, ↓ migration, ↓ invasion, ↑ G0/G1 cell cycle arrest (73)
Oral squamous cell carcinoma (OSCC) miR-145, HOXA1SCC9, SCC15, SCC25, HOKsΔ AFAP1-AS1: ↓ proliferation, ↓ migration, ↓ invasion (74)

Outlines of papers which judged expression of AFAP1-AS1 in cell lines.

(Δ: knock-down, CuB: Cucurbitacin B).

Animal Studies

Investigations, particularly those conducted in BALB/c nude mice models have verified the oncogenic roles of AFAP1-AS1 in different types of cancers. AFAP1-AS1 knock-down has consistently led to significant reduction in tumor size/weight, attenuation of tumor growth rate and enhancement of response of cancer cells to therapeutic modalities (Table 2). In NSCLC, AFAP1-As1 silencing not only reduces tumorigenicity, but also confers chemosensitivity (8). Moreover, its silencing can affect IRF7 and RIG-I-like receptor signals (9). In breast cancer, AFAP1-AS1 down-regulation can affect trastuzumab resistance (21).

Table 2

Tumor TypeAnimal modelsResultsReference
Non-small Cell Lung Cancermale athymic nude BALB/c mice Δ AFAP1-AS1: ↓ tumorigenicity, ↓ chemo-resistance (8)
_Δ AFAP1-AS1: ↓ mRNA and protein of IRF7 and RIG-I-like receptor signals (9)
↑ AFAP1-AS1: ↑ mRNA and protein of IRF7 and RIG-I-like receptor signals
male BALB/c nude miceΔ AFAP1-AS1: ↓ tumor volume, ↓ tumor weight (10)
BALB/c nude miceΔ AFAP1-AS1: ↓ tumor weight, ↓ tumor size (37)
Lung cancerBALB/c nude miceΔ AFAP1-AS1: ↓ tumor volume, ↓ tumor weight, ↓ tumor growth (38)
murine xenograft miceΔ AFAP1-AS1: ↓ tumor growth (15)
female nude miceΔ AFAP1-AS1: ↓ metastatic nodules (16)
Breast cancer (BC)female nude miceΔ AFAP1-AS1: ↓ tumor growth (17)
Female BALB/c nude miceΔ AFAP1-AS1: ↓ tumor growth (18)
female nude miceΔ AFAP1-AS1: ↓ tumor growth, ↓ tumor weight (20)
BALB/C specific-pathogen-free nude miceΔ AFAP1-AS1: ↓ tumor volume, ↓ tumor weight, ↓ tumor growth (19)
male BALB/c nude mice Δ AFAP1-AS1: ↓ tumor resistance, ↓ metastasis (21)
Osteosarcomafemale BALB/c nude mice Δ AFAP1-AS1: ↓ tumor growth, ↓ invasion (22)
male athymic BALB/c nude miceΔ AFAP1-AS1: ↓ tumor volume, ↓ tumor weight, ↓ tumor growth (23)
female BALB/c nude miceΔ AFAP1-AS1: ↓ tumor size, ↓ tumor weight (24)
Esophageal cancer (EC) _Δ AFAP1-AS1: ↓ATF2, ↑ miR-26a (29)
Gastric cancer (GC)male BALB/c nude miceΔ AFAP1-AS1: ↓ tumor volume, ↓ tumor weight, ↓ tumor growth (44)
Prostate cancernude miceΔ AFAP1-AS1: ↓ tumor volume, ↓ tumor weight, ↑ C-caspase 3 (31)
Nasopharyngeal carcinoma (NPC)male BALB/C nude mice↑ AFAP1-AS1: ↑ metastasis (33)
nude miceΔ AFAP1-AS1: ↓ number and size of the metastatic foci (47)
Endometrial carcinoma (EC)male BALB/c nude miceΔ AFAP1-AS1: ↓ tumor volume, ↓ tumor weight (48)
Cholangiocarcinoma (CCA)female BALB/c/nu nude miceΔ AFAP1-AS1: ↓ tumor volume, ↓ tumor weight, ↓ number and size of the metastatic foci (49)
female BALB/c athymic nude miceΔ AFAP1-AS1: ↓ tumor volume, ↓ tumor weight (50)
Colorectal cancer (CRC)male C57BL/6 nude miceΔ AFAP1-AS1: ↓ tumor volume, ↓ tumor weight (53)
female BALB/c-nude miceΔ AFAP1-AS1: ↓ tumor growth  (54)
Hepatocellular carcinoma (HCC)female immune-deficient BALB/c-nu nude miceΔ AFAP1-AS1: ↓ tumor weight (57)
nude miceΔ AFAP1-AS1: ↓ tumor weight, ↓ tumor growth, ↓ Ki-67 expression (58)
Pancreatic cancer (PC)nude miceΔ AFAP1-AS1: ↓ tumor volume, ↓ tumor weight (36)
male/female BALB/C nude miceΔ AFAP1-AS1: ↓ tumorigenicity, ↓ EMT process (63)
female BALB/c nude miceCUB-induced Δ AFAP1-AS1: ↓ tumor volume, ↓ tumor weight, ↓ tumor growth (65)
Pancreatic ductal adenocarcinoma (PDAC) nude mice Δ AFAP1-AS1: ↓ tumor volume, ↓ tumor weight (66)
Renal cell carcinoma (RCC)female BALB/c athymic nude miceΔ AFAP1-AS1: ↓ tumor volume, ↓ tumor weight (67)
Melanoma male BALB/c nude miceΔ AFAP1-AS1: ↓ tumor volume, ↓ tumor weight, ↓ tumor size (71)
Tongue squamous cell carcinoma (TSCC)female BALB/c athymic nude miceΔ AFAP1-AS1: ↓ tumor growth, ↓ tumor weight, ↓ tumor size (73)
Oral squamous cell carcinoma (OSCC) male BALB/c nude miceΔ AFAP1-AS1: ↓ tumor volume, ↓ tumor weight (74)

Outlines of studies which tested function of AFAP1-AS1 in xenografts.

(Δ: knock down or deletion).

Clinical Studies

Except from a single low-sample size study in gastric cancer which reported down-regulation of AFAP1-AS1 in tumoral tissues versus nearby samples (6), other studies consistently reported over-expression of AFAP1-AS1 in different neoplastic tissues compared with non-neoplastic tissues of the same origin (Table 3). Even in the mentioned study, levels of AFAP1-AS1 were higher in patients who showed lymphatic or vascular invasion in comparison with those without these properties (6). Moreover, different statistical methods have been applied to assess correlations between expression level of AFAP1-AS1 and clinical outcomes, all of them reporting significant impact of up-regulation of this lncRNA on increasing malignant behaviors of tumors and decreasing patients’ survival. In pancreatic cancer, up-regulation of AFAP1-AS1 has been associated with lymph node involvement, perineural invasion, and poor clinical outcome. An in silico analysis of TCGA data of breast cancer patients has revealed AFAP1-AS1, as a differentially expressed lncRNA in basal tumors whose expression levels are associated with poor survival. Expression of this lncRNA has also been associated with hormone receptors status, HER2 expression, and PAM50 classification (81).

Table 3

Tumor typeNumbers of clinical samplesExpression (Tumor vs. Normal)Kaplan-Meier analysisUnivariate cox regressionMultivariate cox regressionClinicopathologic characteristics of patientsReference
Non-small Cell Lung Cancer (NSCLC)44 NSCLC patient tissues and ANCTshigh____ (8)
165 NSCLC patients, 118 benign lung tumor tissues, and 173 healthy sampleshigh___Paired t test: AFAP1- AS1 was correlated with pathological grade, TNM staging and metastatic ability. (9)
GEO analysishigh___
92 pairs of NSCLC tissues and ANCTshighPatients with high levels of AFAP1-AS1 had poorer OS.Histological grade, TNM stage, and AFAP1-AS1 expression were identified as three prognostic factors.Histological grade, TNM stage, and AFAP1-AS1 expression were independent predictors for OS in NSCLC patients.Chi-square test: Relative levels of AFAP1-AS1 were associated with tumor burden. (10)
7 NSCLC tumor tissues and ANCTshigh____ (11)
126 NSCLC patients and 60 healthy controlshigh___Mann–Whitney U test: High serum levels of AFAP1-AS1 were strongly associated with DM, LNM, poor clinical stage, and larger tumor size. (75)
82 pairs of NSCLC tissue and ANCTshigh____ (76)
52 NSCLC patientshighAFAP1-AS1 down-regulation was correlated with improved survival time._High expression level of ASAP1-S1 was an indicator of poor survival._
Non-small Cell Lung Cancer (NSCLC)96 pairs of lung cancer tissues and ANCTshighAFAP1‐AS1 over-expression was related with short OS and PFS.___ (37)
GEO and TCGA analysis: _high____
121 NSCLC patients and 79 healthy controlshighAFAP1‐AS1 over-expression was related with short OS._AFAP1-AS1 was an independent prognostic indicator for NSCLC patients.Chi-square test: AFAP1-AS1 expression was influenced by clinical stage, smoking history, infiltration extent, LNM and distant metastasis. (77)
36 studies: 6267 NSCLC patientshigh____. (78)
TCGA analysis: 465 LUAD patients and 49 ANCTshigh____ (79)
53 newly diagnosed LUAD tissues and ANCTshigh____
20 pairs of LUAD and LUSC tumor tissues and ANCTshigh____ (80)
TCGA analysis: 57 paired LUAD and normal samples and 16 paired LUSC and normal sampleshigh____
Lung cancer98 pairs of lung cancer tissues and ANCTshigh___Patients with high levels of AFAP1-AS1 had poor histology type, great tumor size, LNM, distant metastasis, and advanced TNM stage. (38)
GSE31210 analysis: 226 primary lung cancer samples and 20 normal lung sampleshighHigh levels of were associated with poor OS.___ (12)
GSE19804 analysis: 60 pairs of lung cancer tissues and ANCTshigh____
GSE27262 analysis: 25 pairs of tumor tissues and ANCTshigh____
GSE18842 analysis: 46 pairs of tumor tissues and ANCTshigh____
GSE37745 analysis: 106 lung cancer biopsieshighHigh levels of were associated with poor OS.___
187 paraffin-embedded lung cancer tissues and 36 normal lung specimenshighHigh AFAP1-AS1 expression was tightly correlated with poorer OS.___ (16)
Lung cancer36 lung adenocarcinoma tissue samples and ANCTshighHigh levels of AFAP1-AS1 were associated with shorter DFS.___ (39)
Breast cancer (BC)160 pairs of breast cancer tissues and ANCTshighThe 3-years OS of patients with high AFAP1-AS1 expression was lower.AFAP1-AS1 expression, tumor grade, TNM stage, and LNM were Significant factors.High level of AFAP1-AS1 was correlated with the malignant features._ (40)
20 pairs of breast cancer tissues and ANCTshigh____ (17)
TCGA analysis: _high____ (18)
31 pairs of TNBC tissues and ANCTshighHigh levels of AFAP1-AS1 were correlated with poorer DFS and OS._AFAP1-AS1 could be regarded as an independent prognostic factor in TNBC._ (20)
TCGA analysis: _highHigh expression of AFAP1 was correlated with short surviavl in patients with Luminal B, HER2 +, and basal tumors and worse OS Luminal A and HER2 + tumor subtypes.___ (81)
8 pairs of TNBC tissues and ANCTshigh____ (19)
64 HER-2 positive patients and 40 HER-2 negative patientsHigher in HER-2 positive than HER-2 negative____ (21)
51 pairs of tumor tissues and ANCTshigh___Its expression was low in ki-67 negative tumor tissues. (82)
Osteosarcoma8 pairs of Osteosarcoma tissues and ANCTshigh____ (22)
45 OS tissues and ANCTshighPatients who had high AFAP1-AS1 expression level indicated poor OS rate than those who had low AFAP1-AS1 expression level.___ (23)
49 pairs of OS tissues and ANCTshighPatients with higher expression of AFAP1-AS1 showed lower OS and PFS rates. ___ (24)
Esophageal cancer (EC) 42 ESCC tissues and 35 ANCTshigh____ (30)
65 pairs of tissues and ANCTshigh___Chi‐squared test: high level of AFAP1‐AS1 was correlated with tumor size and advanced TNM stage. (41)
48 pairs of ESCC tissues and ANCTshigh____ (83)
162 pairs of ESCC tissues and ANCTshighHigh levels of AFAP1‐AS1 were strongly associated with shorter PFS.Tumor depth, LNM, TNM stage, dCRT response, and AFAP1‐AS1 expression were associated with PFS and OS.Tumor depth, dCRT response, and AFAP1‐AS1 expression were independent prognostic factors for PFS. Moreover, high levels of AFAP1‐AS1 indicated unfavorable OS.Chi‐squared test: higher expression of AFAP1‐AS1 was strongly correlated with LNM, distant metastasis, advanced clinical stage, and lack of response to dCRT.
Gastric cancer (GC)20 pairs of GC tissues and ANCTshigh____ (27)
52 pairs of GC tissues and ANCTshigh____ (43)
91 pairs of primary gastric cancer tissues and their ANCTshighPatients with high levels of AFAP1-AS1 showed poor OS than those with low levels._Lymph node metastasis, TNM stage, and AFAP1-AS1 expression levels were independent prognostic factors for OS time.X2 test: expression of AFAP1-AS1 was associated with LNM and TNM stage. (25)
52 pairs of GC tissues and ANCTshighPatients with high expression of AFAP1-AS1 had a significantly poorer OS compared to those with low-expression of AFAP1-AS1.___ (28)
30 tumor tissues and ANCTsdown___Levels of AFAP1-AS1 were higher in patients who showed lymphatic or vascular invasion in comparison with those who did not. (6)
66 pairs of GC tissues and ANCTshigh__Expression of AFAP1-AS1, clinical stage, and tumor differentiation could be regarded as the factors that were independently correlated with OS.Higher expression level of AFAP1-AS1 was correlated with tumor mass, clinical stage, and tumor differentiation.  (44)
89 GC patients, 55 benign gastric lesion groups, 73 age-matched healthy volunteershigh___Logistic regression analysis: high level of AFAP1-AS1 was significantly correlated with tumor size, TNM stage and LNM. (45)
80 pairs of GC tissues and ANCTshighPatients with high levels of AFAP1-AS1 had shorter OS than those with low levels of AFAP1-AS1.___ (84)
Prostate cancer30 PCa tissues and corresponding nearby healthy tissueshigh____ (31)
38 pairs of prostate cancer tissues and ANCTshighPatients with high expression of AFAP1-AS1 had lower OS.__Chi-Square test: AFAP1-AS1 expression was associated with histological grade and distant metastasis. (32)
Nasopharyngeal carcinoma (NPC)10 pairs of freshly frozen samples and ANCTshighPatients with high expression of AFAP1-AS1 showed lower OS.___ (46)
100 pairs of paraffin-embedded samples and ANCTs
96 paraffin-embedded NPC sampleshighPatients with high expression of AFAP1-AS1 had a poor prognosis, with shorter OS.__Patients with high expression of AFAP1-AS1 were showed distant metastasis when they relapsed. (85)
32 nasopharyngeal carcinoma samples and 13 non tumor nasopharyngeal epithelium tissueshigh___High expression of AFAP1-AS1 was highly correlated with clinical TNM stages, neck LNM, and T stages of the patients. (33)
101 NPC patients and 101 healthy controlshigh____ (86)
101 NPC patients and 20 chronic nasopharyngitis patients 
101 NPC patients and 20 asymptomatic EBV carriers
23 NPC samples and 7 non-tumor nasopharyngeal epithelium sampleshigh____ (47)
112 paraffin-embedded NPC and 10 NPE tissue sampleshighHigh expression of AFAP1-AS1 was correlated with poor OS and poor RFS.__Expression of AFAP1-AS1 was associated with distant tumor metastasis.
Endometrial carcinoma (EC)73 pairs of EC tissues and ANCTshigh____ (48)
Cholangiocarcinoma (CCA)20 pairs of CCA tissues and ANCTs high____ (49)
56 pairs of tumor tissues and ANCTshighPatients with high expression of AFAP1-AS1showed shorter OS.__High expression of AFAP1-AS1 had positive association with tumor size, vascular invasion, and advance TNM stage. (50)
Colorectal cancer (CRC)68 CRC patients and 60 healthy volunteershigh___Chi-squared test: plasma levels of AFAP1-AS1 were correlated with clinical stage. (51)
52 pairs of CRC tissues and ANCTshighPatients with up-regulation of AFAP1-AS1 had a significantly poorer prognosis.AFAP1-AS1 expression, tumor size, TNM stage, and distant metastasis were significantly correlated with OS and DFS.AFAP1- AS1 expression, TNM stage, and distant metastasis were strongly correlated with OS and DFS.High levels of AFAP1-AS1 were associated with tumor size, TNM stage and remote metastasis. (52)
15 pairs of CRC tissues and ANCTshigh____ (53)
TCGA analysis: 50 pairs of clinical colorectal cancer tumors and the peritumoral tissues
80 CRC tissues and 10 normal colon tissueshigh Patients who had high AFAP1-AS1 mRNA levels indicated worse prognosis compared with those with low.___ (54)
Colon CancerGEO analysis: _high____ (55)
TCGA-COAD analysishighPatients with high expression of AFAP1-AS1 indicated shorter OS and DFS.___
Hepatocellular carcinoma17 pairs of tumor tissues and ANCTshigh____ (56)
17 pairs of HCC tissues and ANCTshighPatients with high levels of AFAP1-AS1 showed a shorter median survival time._AFAP1-AS1 expression could be regarded as an independent prognostic factor for OS in HCC patients.High levels of AFAP1-AS1 were correlated with pathological staging and lymph-vascular space invasion. (57)
156 pairs of HCC tissues and ANCTshighPatients with low levels of AFAP1-AS1 showed better OS and DFS.__High levels of AFAP1-AS1 were correlated with tumor size, vascular invasion, and TNM stage. (58)
Cervical cancer (CC)TCGA analysis: _highPatients with high expression of AFAP1-AS1 expression had a short OS.__High levels of AFAP1-AS1 were correlated with TNM stage. (59)
Laryngeal carcinoma24 pairs of tumor tissues and ANCTshigh____ (34)
Thyroid cancer36 pairs of tumor tissues and ANCTshighPatients with high expression of AFAP1-AS1 expression had a short OS_AFAP1-AS1 expression might be a positive, independent prognostic factor._ (60)
Glioma52 glioma cases and 5 non-tumor control caseshighHigh expression of AFAP1-AS1 predicted worse prognosis in glioma patients.__Expression of AFAP1-AS1 was closely correlated with glioma grading and KPS scores. (61)
Ovarian cancer (OC)65 pairs of OC tissues and ANCTshigh___Upregulation of AFAP1-AS1 was correlated with high FIGO stage and resistance response. (62)
39 pairs of OC tissues and ANCTshighPatients with low expression of AFAP1-AS1 showed greater survival probability.__Chi-square analysis: Upregulation of AFAP1-AS1 was correlated with FIGO stage. (35)
Pancreatic cancer (PC)75 pairs of PC tissues and ANCTshigh___Upregulation of AFAP1-AS1 was positively associated with TNM stage, LNM, and tumor size. (36)
GEO analysis: _high___ (64)
63 pairs of PC tissues and ANCTshighPatients with high AFAP1-AS1 expression showed a shorter 5-year OS rate. __Upregulation of AFAP1-AS1 was positively associated with advanced TNM stage, tumor size and LNM.
Pancreatic ductal adenocarcinoma (PDAC) 8 cases of PDAC tissues and 4 cases of CP tissueshigh____ (66)
90 pairs of PDAC tissues and ANCTshighPatients with high expression of AFAP1-AS1 showed worse OS and PFS.__Upregulation of AFAP1-AS1 was positively associated with LNM and perineural invasion.
Renal cell carcinoma (RCC)60 ccRCC tissues and 20 ANCTshighPatients with high expression of AFAP1-AS1 showed worse OS.__Upregulation of AFAP1-AS1 was positively associated with LNM and TNM stage. (67)
Gallbladder cancer (GBC)40 pairs of GBC tissues and ANCTshighUpregulation of AFAP1-AS1 indicated a poor prognosis in gallbladder cancer.__Upregulation of AFAP1-AS1 was positively associated with tumor size. (68)
Pituitary adenoma60 pairs of pituitary adenomas tissues and ANCTshigh____ (70)
Retinoblastoma58 freshly frozen retinoblastoma tissue samples and 10 non-cancerous retina sampleshighPatients with high expression of AFAP1-AS1 had shorter OS.High-expression of AFAP1-AS1 was found to be an unfavorable prognostic factor. High-expression of AFAP1-AS1 was found to be an independent unfavorable prognostic factor.Upregulation of AFAP1-AS1 was positively associated with tumor bulk as well as choroidal or optic nerve invasion. (72)
Tongue squamous cell carcinoma103 pairs of tumor tissues and ANCTshighHigh AFAP1-AS1 expression was related to poor survival.__Expression level of AFAP1-AS1 was associated with tumor differentiation, T classification, clinical stage, invasion depth, and relapse. (73)
Oral squamous cell carcinoma (OSCC) 48 pairs of OSCC tissues and ANCTshighPatients with high AFAP1-AS1 expression had a poor OS.__Expression level of AFAP1-AS1 was associated with an advanced clinical stage and LNM. (74)

Outlines of studies that appraised levels of AFAP1- AS1 in clinical setting.

(ANCTs, adjacent non-cancerous tissues; OS, Overall survival; DFS, Disease-free survival; PFS, progression free survival; TNM, tumor‐node‐metastasis; dCRT, definitive chemoradiotherapy; DM, distant metastasis; LNM, lymph node metastasis; TCGA, The Cancer Genome Atlas; GEO, Gene Expression Omnibus; KPS, Karnofsky Performance Status; CP, chronic pancreatitis tissues).

Tissue levels of AFAP1-AS1 could be used as a prognostic biomarker with the areas under ROC curves values of 0.86 and 0.93 for forecasting cancer progression in the periods of 6 and 12 months, respectively (66).

The ability of tissue levels of AFAP1-AS1 or its circulatory levels in differentiation of patients’ samples from control samples has been appraised in different types of cancers (Table 4). For instance, Li et al. have shown that over-expression of AFAP1-AS1 in serum samples of patients with NSCLC compared with normal controls can be used to distinguish these two sets of samples with an area under the curve (AUC) of 0.759. Combination of expression levels of this lncRNA with those of cyfra21-1 has increased AUC value to 0.860. Moreover, AFAP1-AS1 over-expression has been more prominent in patients with distant or lymph node metastasis, advanced clinical stage, and greater tumor burden (75). Serum levels of AFAP1-AS1 have also been shown to separate gastric cancer patients from controls with higher AUC value compared with conventional markers, i.e. CEA and CA19-9. Notably, serum levels of AFAP1-AS1 have been shown to be reduced following surgical treatment of patients (45).

Table 4

Tumor TypeNumbers of clinical samplesDistinguish betweenArea Under CurveSensitivitySpecificityAccuracyReference
Non-small Cell Lung Cancer (NSCLC)126 NSCLC patients and 60 healthy controlspatients with NSCLC vs. healthy controls0.7590.6930.8830.759 (75)
Breast cancer160 pairs of breast cancer tissues and ANCTsCancer tissues vs. ANCTs0.73674%69%_ (40)
Esophageal cancer (EC) 162 pairs of ESCC tissues and ANCTsCancer tissues vs. ANCTs0.80273.3%79.4%_ (83)
Gastric cancer (GC)30 tumor tissues and ANCTsCancer tissues vs. ANCTs0.6770%63.3%_ (6)
89 GC patients and 73 healthy controlspatients with GC vs. healthy controls0.82076.4%56.2%67.3% (45)
80 pairs of GC tissues and ANCTsCancer tissues vs. ANCTs0.880281.25%83.75%_ (84)
Nasopharyngeal carcinoma (NPC)101 NPC patients and 101 healthy controlspatients with NPC vs. healthy controls0.6650.6400.838_ (86)
101 NPC patients and 20 chronic nasopharyngitis patients patients with NPC vs. chronic nasopharyngitis patients 0.6250.5900.822_
101 NPC patients and 20 asymptomatic EBV carrierspatients with NPC vs. asymptomatic EBV carriers0.6200.5920.819_

Diagnostic value of AFAP1-AS1 in different cancers.

ANCTs, adjacent non-cancerous tissues; ESCC, esophageal squamous cell carcinoma.

Discussion

AFAP1-AS1 has been found to be up-regulated in almost all kinds of malignant tissues. This lncRNA has multiple effects in the carcinogenesis process, most of them being exerted through AFAP1-independent manners. Most notably, AFAP1-AS1 can sequester a number of tumor suppressor miRNAs, thus releasing the targets of these miRNAs from inhibitory effects of miRNAs. miR-139-5p, miR-545-3p, miR-497-5p, miR-145, miR-2110, miR-4695-5p, miR-26a, miR-498, miR-155-5p, miR-195-5p, miR-512-3p, miR-423-5p, miR-545-3p, miR‐320a, miR-107, miR-384, miR-133a, miR‐146b‐5p, miR-103a-3p and miR-653-5p are among miRNAs which have been found to be sequestered by AFAP1-AS1 through functional studies in different types of cancer cells. Notably, the interaction between AFAP1-AS1 and miR-497 has been verified in breast cancer and osteosarcoma. Moreover, similar interaction has been verified between this lncRNA and miR-145 in breast cancer and oral squamous cell carcinoma.

In fact, AFAP1-AS1 has multiple binding sites for miRNAs, thus regulating expression of a wide array of miRNAs. It is not clear whether binding of this lncRNA with a certain miRNA affects its interactions with other miRNAs. The crosstalk between AFAP1-AS1 and miRNAs can regulate activity of signaling pathways, angiogenic processes as well as EMT.

AFAP1-AS1 can indirectly influence activity of some cancer-related pathways such as EGFR/AKT, Wnt/β-catenin, PTEN/p-AKT, RhoA/Rac2 and PI3K/AKT. The effects of this lncRNA on Wnt/β-catenin, EGF/AKT and PI3K/AKT are mediated through sponging miR-4695-5p, miR-139-5p and miR-103a-3p, respectively. However, its effects on other pathways might be exerted in an independent manner from miRNAs sponging.

Lung cancer, nasopharyngeal carcinoma, colorectal cancer and cholangiocarcinoma are among cancers in which the interaction between AFAP1-AS1 and AFAP1 has been verified. However, the results of these studies are conflicting. For instance, AFAP1-AS1 silencing has been shown to increase expression of AFAP1 in a single study in lung cancer cells (12), while another study in this type of cancer has shown its effect on enhancement of expression of AFAP1 (11). Moreover, in a single study in MCF-7 breast cancer cells, AFAP1-AS1 silencing has not affected AFAP1 levels or actin filament integrity (40). Therefore, future studies are needed to elaborate the mechanistical impacts of AFAP1/AFAP1-AS1 interactions.

AFAP1-AS1 can affect response of cancer cells to a variety of anti-cancer modalities ranging from conventional chemotherapeutics to targeted therapeutics such as trastuzumab. Therefore, measurement of expression levels of this lncRNA can guide clinical oncologists to find the most appropriate therapeutic option for each patient. AFAP1-AS1 can also affect EMT and stemness of cancer cells, thus promoting their metastatic ability and increasing the propensity to tumor recurrence.

From a prognostic point of view, AFAP1-AS1 levels have been associated with tumor depth, tumor differentiation, TNM stage and other determinants of patients’ survival, thus could be used as markers for prediction of clinical outcomes of patients with a variety of malignant conditions. Diagnostic application of AFAP1-AS1 has been appraised in several types of cancers, with the best results being obtained from studies in gastric and esophageal cancers.

Cumulatively, AFAP1-AS1 is a prototype of cancer-related lncRNAs that regulates carcinogenesis not only through modification of expression of its sense transcript, but also through a variety of other methods such as miRNA sequestering and epigenetically affecting expression of tumor suppressor genes.

Publisher’s Note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Statements

Author contributions

SG-F and BH wrote the draft and revised it. MT designed and supervised the study. TK and MM collected the data and designed the figures and tables. All authors contributed to the article and approved the submitted version.

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Summary

Keywords

AFAP1-AS1, cancer, biomarker, expression, ncRNA

Citation

Ghafouri-Fard S, Khoshbakht T, Hussen BM, Taheri M and Mokhtari M (2021) A Review on the Role of AFAP1-AS1 in the Pathoetiology of Cancer. Front. Oncol. 11:777849. doi: 10.3389/fonc.2021.777849

Received

15 September 2021

Accepted

09 November 2021

Published

29 November 2021

Volume

11 - 2021

Edited by

Shiv K. Gupta, Mayo Clinic, United States

Reviewed by

Rezvan Noroozi, Jagiellonian University, Poland; Amin Safa, Complutense University of Madrid, Spain

Updates

Copyright

*Correspondence: Mohammad Taheri, ; Majid Mokhtari,

This article was submitted to Molecular and Cellular Oncology, a section of the journal Frontiers in Oncology

Disclaimer

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

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