YAP1/MMP7/CXCL16 axis affects efficacy of neoadjuvant chemotherapy via tumor environment immunosuppression in triple-negative breast cancer.

BACKGROUND: To evaluate the association of potential YAP1/MMP7/CXCL16 axis and tumor infiltrating lymphocytes (TILs) related chemo-response in triple-negative breast cancer (TNBC) patients. METHODS: We estimated the messenger RNA (mRNA) expression levels of Yes-associated protein 1 (YAP1), MMP7, and CXCL16 in paired TNBC tumor/para-tumor tissues by quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR), and performed statistical analysis according to neoadjuvant chemotherapy (NAC) response. Based on The Cancer Genome Atlas (TCGA) data, we noticed outstanding expression of MMP7/CXCL16 in TNBC cases, as well as associations between MMP7/CXCL16 and HIPPO-YAP1-relevant kinases. We also performed gene set enrichment analysis (GSEA) between MMP7/CXCL16 and YAP1-associated pathways. Western blotting assay was employed to evaluate YAP1/MMP7/CXCL16 expression in vitro and their modulation sequence. Logistic model stepwise regression analysis was used to assess YAP1, MMP7, CXCL16, and TILs as therapeutic predictors. Residual cancer burden (RCB) score was calculated and statistically analyzed according to intensity of these variables, and receiver operating characteristic (ROC) curve also showed their predictive value in NAC response. Recruitment efficacy for CD4+/CD8+ TIL cells (TCGA data) as well as quantified TIL cells density were both explored according to YAP1, MMP7, and CXCL16 expression level. RESULTS: Up-regulation of YAP1/MMP7 and down-regulation of CXCL16 were both significant in TNBC cases with poor NAC response. Inhibition of YAP1 induced down-regulation of MMP7 and up-regulation of CXCL16, whereas inhibition of MMP7 also induced up-regulation of CXCL16. It was also shown that MMP7/CXCL16 was enriched in the YAP1-related pathway. Activation of the YAP1/MMP7/CXCL16 axis obviously affected RCB of TNBC cases. The ROC curve also supported the predictive value of YAP1/MMP7/CXCL16 axis and TILs density in NAC response prospect. The density of TILs, meanwhile, demonstrated a strong link with the YAP1/MMP7/CXCL16 axis. Over expression of YAP1/MMP7 significantly suppressed recruitment of CD4+/CD8+ TILs, while CXCL16 over expression had a beneficial impact on anti-tumor immune. CONCLUSIONS: Over expression of causes up-regulation of MMP7 and down-regulation of CXCL16, which suppressed CD4+/CD8+ TILs recruitment and indirectly affected NAC response of TNBC patients.