Defining the impact of Chromobox 2 on the immune tumor microenvironment of high grade serous ovarian carcinoma (092)

Abstract

Objectives: Chromobox 2 (CBX2), an epigenetic writer and subunit of Polycomb Repressor Complex 1 (PRC1), is associated with poor survival and chemoresistance in high-grade serous ovarian carcinoma (HGSOC). In prostate cancer, PRC1 drives an immunosuppressive tumor microenvironment (TME) via induction of CCL2 and recruitment of tumor-associated macrophages (TAMs). We sought to define the impact of genetic modulation of CBX2 on the immune tumor microenvironment (TME) in HGSOC. Methods: We performed lentiviral transduction of shCBX2 in HGSOC cells (OVCAR4). Knockdown was confirmed using immunoblot and mRNA expression via qPCR. RNA sequencing of shControl and shCBX2 cells was performed. Using an ID8 syngeneic mouse model (Trp53-/-, Brca2-/-), we inoculated five mice with either ID8 shControl, ID8 shCbx2/1, or ID8 shCbx2 and allowed tumors to develop. Tumors and ascites volume were measured. The NanoString Mouse Immune Oncology 360 panel was performed on both shControl and shCbx2 tumors to identify differential immune signatures. Multi-spectral immunohistochemistry (mIHC) was performed on 126 human-derived HGSOC tumors to define the relationship between CBX2 and macrophage infiltration. Using The Cancer Genome Atlas (TCGA) and the TIMERv2 platform, we evaluated correlations among CBX2, CCL2, and TAMs. Statistics were completed with ANOVA with Turkey correlation or Pearson, as indicated. A p-value of < 0.05 deemed significant. Conclusions: CBX2 remodels the TME of HGSOC to a more immunosuppressive state. Our data suggest this may be due to increased CCL2 and CXCL16-mediated macrophage activity in the tumor. Loss of CBX2 is associated with decreased levels of CCL2 and CXCL16, as well as inhibited tumor progression. CBX2 has the potential to serve as a novel therapeutic target and could optimize current immunotherapy. Objectives: Chromobox 2 (CBX2), an epigenetic writer and subunit of Polycomb Repressor Complex 1 (PRC1), is associated with poor survival and chemoresistance in high-grade serous ovarian carcinoma (HGSOC). In prostate cancer, PRC1 drives an immunosuppressive tumor microenvironment (TME) via induction of CCL2 and recruitment of tumor-associated macrophages (TAMs). We sought to define the impact of genetic modulation of CBX2 on the immune tumor microenvironment (TME) in HGSOC. Methods: We performed lentiviral transduction of shCBX2 in HGSOC cells (OVCAR4). Knockdown was confirmed using immunoblot and mRNA expression via qPCR. RNA sequencing of shControl and shCBX2 cells was performed. Using an ID8 syngeneic mouse model (Trp53-/-, Brca2-/-), we inoculated five mice with either ID8 shControl, ID8 shCbx2/1, or ID8 shCbx2 and allowed tumors to develop. Tumors and ascites volume were measured. The NanoString Mouse Immune Oncology 360 panel was performed on both shControl and shCbx2 tumors to identify differential immune signatures. Multi-spectral immunohistochemistry (mIHC) was performed on 126 human-derived HGSOC tumors to define the relationship between CBX2 and macrophage infiltration. Using The Cancer Genome Atlas (TCGA) and the TIMERv2 platform, we evaluated correlations among CBX2, CCL2, and TAMs. Statistics were completed with ANOVA with Turkey correlation or Pearson, as indicated. A p-value of < 0.05 deemed significant. Conclusions: CBX2 remodels the TME of HGSOC to a more immunosuppressive state. Our data suggest this may be due to increased CCL2 and CXCL16-mediated macrophage activity in the tumor. Loss of CBX2 is associated with decreased levels of CCL2 and CXCL16, as well as inhibited tumor progression. CBX2 has the potential to serve as a novel therapeutic target and could optimize current immunotherapy.