# Mesothelin-Associated Anti-Senescence Through P53 in Pancreatic Ductal Adenocarcinoma

## TL;DR

This study shows that the protein mesothelin helps pancreatic cancer cells avoid aging-like states, and targeting it could improve cancer treatments.

## Contribution

The study identifies a novel mesothelin-associated anti-senescence mechanism in pancreatic cancer via P53 pathways.

## Key findings

- MSLN deficiency in PDAC cells leads to senescence features like growth arrest and elevated P53 and P21waf1.
- MSLN expression inversely correlates with DNA damage/repair pathways in PDAC tissue samples.
- IL-8 secretion increases in MSLN-deficient cells, suggesting modulation of the senescence-associated secretory phenotype.

## Abstract

Pancreatic ductal adenocarcinoma (PDAC) is a deadly disease with limited treatment options. This study focuses on the protein mesothelin (MSLN), which is highly expressed in over 89% of clinical PDAC specimens and helps cancer cells grow and avoid death. This study aims to determine how MSLN prevents cancer cells from entering a state called senescence, where they stop growing. The results show that silencing MSLN gene expression in PDAC cells induced senescence phenotypes, including growth arrest and an increased expression of senescence markers (P53, P21waf1, and P16ink4a), along with higher IL-8 production. Mechanically, high DNA damage/DNA repair activities associated with low MSLN expression may activate the senescence pathway in pancreatic cancer cells. Our findings could lead to better treatment options for pancreatic cancer, potentially improving outcomes for patients.

Objectives: Mesothelin (MSLN) is overexpressed in pancreatic ductal adenocarcinoma (PDAC), promoting cell proliferation, migration, and inhibiting apoptosis. While its oncogenic properties have been documented, the role of MSLN in regulating cellular senescence—a tumor-suppressive mechanism—has remained unexplored. This study is the first to identify and characterize a novel mesothelin-associated anti-senescence (MAAS) effect in PDAC. Methods: A proteogenomic analysis of PDAC tissue samples from the Clinical Proteomic Tumor Analysis Consortium (CPTAC) was performed to evaluate MSLN-associated senescence pathways using WebGestalt. Human and murine PDAC cell lines with modified MSLN expression were analyzed for senescence phenotypes via SA-β-gal staining, Western blotting of key regulators (P53, P21waf1, and P16ink4a), γH2AX immunoblotting, and IL-8 quantification using ELISA. Results: The CPTAC analysis revealed an inverse correlation between MSLN expression and DNA damage/repair pathways. MSLN-deficient cells exhibited classic senescence features—growth arrest, an enlarged morphology, and elevated SA-β-gal activity. The expression of P53, P21waf1, and P16ink4a was upregulated, alongside increased γH2AX levels, indicating the activation of the DNA damage response. IL-8 secretion was significantly higher in the MSLN knockdown cells and reduced in the MSLN-overexpressing cells, consistent with the modulation of the SASP. Notably, MSLN deficiency impaired cell viability without inducing overt cytotoxicity, supporting a shift toward senescence. Conclusions: Our findings uncover a previously unrecognized mechanism through which MSLN promotes tumor progression by suppressing senescence via P53-associated pathways. Targeting the MAAS pathway may offer a novel therapeutic strategy to restore tumor-suppressive senescence and enhance treatment efficacy in PDAC.