SCCA1/SERPINB3 suppresses anti-tumor immunity and blunts therapy-induced T cell responses via STAT-dependent chemokine production.

Abstract

Cancer patients with high serum squamous cell carcinoma antigen (SCCA1/SERPINB3) are commonly associated with treatment resistance and poor prognosis. Despite being a clinical biomarker, the modulation of SERPINB3 in tumor immunity is poorly understood. We found positive correlations of SERPINB3 with CXCL1/8, S100A8/A9 and myeloid cell infiltration through RNAseq analysis of human primary cervix tumors. Induction of SERPINB3 resulted in increased CXCL1/8 and S100A8/A9, which promoted monocyte and MDSC migration in vitro. In mouse models, Serpinb3a-tumors showed increased MDSC and TAM infiltration contributing to T cell inhibition and this was further augmented upon radiation. Intratumoral knockdown of Serpinb3a demonstrated tumor growth inhibition and reduced CXCL1, S100A8/A9, MDSC, and M2 macrophage infiltration. These changes led to enhanced cytotoxic T cell function and sensitized tumors to radiotherapy. We further revealed SERPINB3 promoted STAT-dependent suppressive chemokine expression, whereby inhibiting STAT activation by ruxolitinib or siRNA abrogated CXCL1/8 and S100A8/A9 in SERPINB3 cells. Patients with elevated pre-treatment SCCA and high pSTAT3 had increased intratumoral CD11b+ myeloid cell compared to patients with low SCCA and pSTAT3 cohort that had overall improved survival after radiotherapy. These findings provide a preclinical rationale for targeting SERPINB3 in tumors to counteract the immunosuppression and improve response to radiation.