Role of tumor suppressor genes P53 and PTEN in CD44-mediated gastric adenocarcinoma multidrug resistance

Gastric adenocarcinoma (GAC) is often diagnosed at advanced stages, when curative options are limited and marked chemoresistance is already present. Although tumor suppressor genes (TSGs) are frequently altered in GAC, their impact on chemoresistance is not well understood. Gene expression data from The Cancer Genome Atlas cohort TCGA-STAD were validated by RT-qPCR in a Spanish cohort of GAC. In the human GAC cell line AGS, gene knocking-out was performed using CRISPR/Cas9. Cell viability (MTT-formazan test) and proliferation rate (digital holographic microscopy) were determined. Among the most frequently inactivated TSGs, TP53, PTEN, and ARID1A were selected for further studies. In GAC samples, TP53 was upregulated, whereas PTEN and ARID1A were downregulated. Mutations in these TSGs led to a consistent alteration in the expression of their target genes. AGS cells exhibited TSG expression profiles like those observed in GAC, which supports their suitability as an in vitro model. Knocking-out ARID1A (ARID1A^KO) enhanced cell chemosensitivity. In contrast, silencing TP53 (p53^KO) or PTEN (PTEN^KO) led to increased resistance to platinum-based drugs, doxorubicin, epirubicin, and docetaxel. Characterization of the resistome was performed using TaqMan Low-Density Arrays. In p53^KO and PTEN^KO cells, the expression of UGT1A and CD44 was altered. Additional silencing of CD44 in these cells partially reversed their chemoresistance. Moreover, pharmacological inhibition of CD44 with verbascoside sensitized p53^KO and PTEN^KO cells to anticancer drugs. In conclusion, dysfunctional TP53 and PTEN contribute to altered drug responses of GAC. Moreover, we identified pharmacological vulnerabilities that could be useful to chemosensitize these tumors.