Pan-Cancer Multi-Omics Characterization of Calcyphosine and Its Revealed 1 Links to the Immune Microenvironment and Regulatory Networks in 2 Endometrial Carcinoma

Xi Chen¹Ruiyue Wu¹Zijing Wang²Fengfeng Wang¹Dan Hu¹Xuehan Bi^1*Xiaolei Liang^1*Yongxiu Yang^1*

• ¹First Hospital of Lanzhou University, Lanzhou, China
• ²General Hospital of Ningxia Medical University, Yinchuan, China

Objective: The calcium-dependent activator protein for secretion (CAPS) 19 has emerged as a protein of interest in tumor biology; however, its functional 20 significance in endometrial carcinoma (EC) remains largely unexplored. Methods: We 21 performed an integrative analysis leveraging bulk RNA sequencing data from The 22 Cancer Genome Atlas, GTEx, and publicly available EC datasets, coupled with gene 23 set enrichment analysis (GSEA) and single-cell transcriptomic profiling. The 24 association between CAPS expression and clinicopathological parameters as well as 25 patient prognosis was systematically assessed. In addition, functional enrichment, 26 intercellular communication, and immune infiltration analyses were conducted to 27 elucidate the molecular and microenvironmental roles of CAPS. In vitro assays were 28 employed to validate the biological effects of CAPS knockdown on EC cell 29 proliferation, migration, and invasion. Results: CAPS was significantly upregulated in 30 early-stage, low-grade, and endometrioid endometrial carcinoma, and its elevated 31 expression was associated with improved patient survival. GSEA indicated that high 32 CAPS expression was correlated with enhanced ribosome biogenesis and oxidative 33 phosphorylation, along with suppression of proliferative signaling, reflecting a 34 metabolically differentiated phenotype. Single-cell transcriptomic analysis revealed 35 that CAPS was specifically enriched in terminally differentiated secretory epithelial 36 cells, promoting epithelial maturation and oxidative metabolism. Furthermore, 37 CAPS-positive cells exhibited extensive crosstalk with immune cells, suggesting a 38 potential role in facilitating anti-tumor immune responses. Functional assays 39 confirmed that CAPS knockdown markedly enhanced EC cell proliferation, migration, 40 and invasion. Conclusion: CAPS may act as a tumor suppressor in EC by stabilizing 41 microtubule architecture, reprogramming cellular metabolism, and modulating 42 immune interactions within the tumor microenvironment. These findings highlight 43 CAPS as a promising prognostic biomarker and potential therapeutic target in EC.