Abstract 2680: SERPINB3 promotes myeloid cell chemotaxis and associated chemokine production in cervical cancer

Squamous cell carcinoma antigen (SERPINB3) is a widely used biomarker for epithelial cancers including uterine cervix, head and neck, and esophagus. We have previously shown that SERPINB3 contributes to radiation resistance, mainly due to its predominant function as a protease inhibitor that interfered with lysosomal cell death. In addition, elevated SERPINB3 is also observed in various inflammatory conditions related to increased cytokine expression such as, atopic dermatitis, psoriasis, asthma and chronic obstructive pulmonary disease, indicative of potential immunoregulatory function of SERPINB3. We hypothesized that elevated SERPINB3 may also contribute to altered tumor immunity, leading to reduced sensitivity and therapeutic effects of radiation treatment. Thus, we sought evidence of SERPINB3 expression in relation to immune regulation using RNA sequencing analysis of cervical tumor biopsies from 66 patients, and identified a positive correlation of SERPINB3 with chemokines CXCL1, CXCL8, S100A8, and S100A9. These chemokines are known to induce myeloid cell accumulation in the tumor microenvironment, and the presence of myeloid cells have been shown to reduce the efficacy of radiotherapy in cervical cancer. Indeed we found enrichment of myeloid cell subsets on immune cell prediction analysis with xCell in SERPINB3-high tumors. We then examined expression and secretion of myeloid-attractant chemokines via quantitative PCR and ELISA in SERPINB3-overexpressing cervical cancer cells, and confirmed the upregulation of CXCL1/8 and S100A8/A9. Supernatants collected from SERPINB3-overexpressing cells contained chemoattractant to myeloid cells as evidenced by transwell assay using human peripheral blood mononuclear cells from patients with cervical cancer. In the mouse models, tumors formed by SERPINB3-expressing cells induced an immunosuppressive microenvironment with the increased infiltration of M2 macrophages and MDSCs in tumors and spleens. Furthermore, we observed the elevated phosphorylation of STAT1/3/5 transcription factors, known to regulate inflammatory chemokine expression, in SERPINB3-high cells. In our patient cohort, RNA-seq analysis of biopsies collected from 20 patients both before and 3 weeks into chemoradiation therapy (CRT) were analyzed for changes of SERPINB3 in comparison to chemokine expression. We found that patients with decreased SERPINB3 expression in the mid-CRT biopsy (n=7) showed downregulated S100A8/A9 levels in tumors while patients with increased SERPINB3 (n=13) had upregulated S100A8/A9 expression. Our findings suggest that SERPINB3 promotes chemokine secretion involved in myeloid cell-mediated immune suppression which may contribute to negative impacts on radiation treatment in patients with cervical cancer. Citation Format: Liyun Chen, Songyan Wang, Victoria Shi, Fiona Ruiz, Kay Jayachandran, Jin Zhang, Pippa Cosper, Perry Grigsby, Julie Schwarz, Stephanie Markovina. SERPINB3 promotes myeloid cell chemotaxis and associated chemokine production in cervical cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2680.