AUTHOR=Wang Wei , Xia Xinhang , Chen Kuifei , Chen Meng , Meng Yinnan , Lv Dongqing , Yang Haihua 

TITLE=Reduced PHLPP Expression Leads to EGFR-TKI Resistance in Lung Cancer by Activating PI3K-AKT and MAPK-ERK Dual Signaling

JOURNAL=Frontiers in Oncology

VOLUME=Volume 11 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2021.665045

DOI=10.3389/fonc.2021.665045

ISSN=2234-943X

ABSTRACT=Background:
Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are effective in advanced EGFR-mutate non-small cell lung cancer (NSCLC) but the magnitude of tumor regression varies and drug resistance is unavoidable. The pleckstrin homology domain leucine-rich repeat protein phosphatase (PHLPP) levels are reduced or lost and acts as a tumor suppressor in many cancers. Here, we hypothesize that PHLPP is a key regulator of EGFR-TKI sensitivity and a potential treatment target for overcoming resistance to EGFR-TKI in lung cancer.
Methods:
Growth and inhibition of growth were assessed by MTT and colony formation assay. The lentivirus-mediated delivery of shRNA was used to generated stable knockdown of PHLPP expression, and retrovirus-mediated delivery was used to generated stable overexpression of PHLPP lung cancer cells. Western blotting, RT-PCR were used to determined PHLPP expression in vitro. PHLPP expression in clinical sample was determined by Immunohistochemical (IHC) staining. A transcriptomic of PHLPP in NSCLC according to gefitinib sensitivity obtained from GEO database were analysis. Xenografts bearing PHLPP knockdown and control were evaluated EGFR-TKI induced tumor regression.
Results:
The basal PHLPP expression was higher in gefitinib-sensitive NSCLC cell lines than gefitinib-resistant NSCLC cell lines, and had dramatically reduced expression in gefitinib acquired resistance cell line HCC827. Knockdown of PHLPP decreased cell death induced by the EGFR-TKI, overexpression of PHLPP enhanced or restored EGFR-TKIs sensitivity in gefitinib-resistance NSCLC cells. Mechanistically, PHLPP downregulation attenuates the effect of EGFR-TKI on the both AKT and ERK pathway, thereby decreasing the sensitivity to EGFR inhibitors. In xenograft model, knockdown of PHLPP decreased tumor response to gefitinib and advanced regrowth after gefitinib treatment. In clinical, PHLPP expression were reduced in the post-relapse tumor compared to that of pre-treatment, and low PHLPP in pre-treatment sample is statistically significantly correlated with shorter progression-free survival (PFS) for patients with EGFR-mutant lung adenocarcinoma treated with EGFR-TKI.
Conclusions:
Our data point to activation of PI3K-AKT and MAPK-ERK pathway by PHLPP loss as a potentially mechanism of resistance to EGFR-TKI, nominate PHLPP as a potential biomarker for EGFR-TKIs sensitivity predictors, and imply maintain PHLPP expression during EGFR-TKIs therapy may be valuable strategy for delaying or overcoming drug resistance.