Hamade, A. | bioRxiv Science

bioRxiv2022

PTEN and BRCA1 tumor suppressor loss associated tumor immune microenvironment exhibits differential response to therapeutic STING pathway activation in a murine model of ovarian cancer

BackgroundHigh grade serous ovarian carcinoma (HGSC) is the most lethal gynecologic malignancy characterized by chemoresistance and high rates of recurrence. HGSC tumors display a high prevalence of tumor suppressor gene loss. Loss of BRCA1 and PTEN function due to mutations or epigenetic influence have been widely associated with variable clinical outcomes, where tumors with BRCA1 mutations exhibit increased chemosensitivity and those with PTEN mutations have been reported to exhibit chemoresistance. Given the established type 1 interferon regulatory function of BRCA1 and PTEN genes and associated contrasting T cell infiltrated and non-infiltrated tumor immune microenvironment (TIME) states, in this study we investigated the potential of Stimulator of Interferon Genes (STING) pathway activation in improving overall survival via enhancing chemotherapy response, specifically in tumors with PTEN deficiency. MethodsExpression of PTEN protein was evaluated in tissue microarrays generated using pre-treatment tumors collected from a cohort of 110 patients with HGSC. Multiplex immunofluorescence staining was performed to determine spatial profiles and density of selected lymphoid and myeloid cells. In vivo studies using the syngeneic murine HGSC cell lines, ID8-Trp53-/-; Pten-/-and ID8-Trp53-/-; Brca1-/-, were conducted to characterize the TIME and response to carboplatin chemotherapy in combination with exogenous STING activation therapy. ResultsTumors with absence of PTEN protein exhibited a significantly decreased disease specific survival and intra-epithelial CD68+ macrophage infiltration as compared to intact PTEN expression. In vivo studies demonstrated that Pten deficient ovarian cancer cells establish an immunosuppressed TIME characterized by increased proportions of M2-like macrophages, GR1+ MDSCs in the ascites, and reduced effector CD8+ cytotoxic T cell function compared to Brca1 deficient cells; further, tumors from mice injected with Pten deficient ID8 cells exhibited an aggressive behavior due to suppressive macrophage dominance in the malignant ascites. In combination with chemotherapy, exogenous STING activation resulted in longer overall survival in mice injected with Pten deficient ID8 cells, reprogrammed intraperitoneal M2-like macrophages derived from Pten deficient ascites to a M1-like phenotype and rescued CD8+ cytotoxic T cell activation. ConclusionsThis study reveals the importance of considering the influence of cancer cell intrinsic genetic alterations on the TIME for therapeutic selection. We establish the rationale for the optimal incorporation of interferon activating therapies as a novel combination strategy in PTEN deficient HGSC.

immunology↗

bioRxiv2021

The influence of age and sex on the pre-treatment immune microenvironment of a carcinogen induced murine model of bladder cancer

The incidence of urothelial carcinoma of the bladder is four times higher in males than females; however, females tend to present with a more aggressive disease, a poorer response to immunotherapy and suffer worse clinical outcomes. Recent findings have demonstrated sexual dimorphism in the tumor immune microenvironment of non-muscle invasive bladder cancer and associated clinical outcomes. However, a significant gap in knowledge remains with respect to the current pre-clinical modeling approaches and more precisely recapitulating these differences towards improved therapeutic design. Based on the similarities in mucosal immune physiology between humans and mice, we evaluated the sex and age-related immune alterations in healthy murine bladders. Bulk-RNA sequencing and multiplex immunofluorescence based spatial immune profiling of healthy murine bladders from male and female mice of age groups spanning young to old showed a highly altered immune landscape that exhibited sex and age associated differences, particularly in the context of B cell associated responses. Spatial profiling using markers specific to macrophages, T lymphocytes, B lymphocytes, activated dendritic cells, high endothelial venules, myeloid cells and the PD-L1 immune checkpoint showed sex and age associated differences. Bladders from healthy older female mice showed a higher number of tertiary lymphoid structures (TLSs) compared to both young female and male equivalents. Spatial immune profiling of N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) carcinogen exposed male and female bladders from young and old mice revealed a similar frequency of TLS formation, sex differences in the bladder immune microenvironment and, age differences in latency of tumor induction. These findings support the incorporation of sex and age as factors in pre-clinical modeling of NMIBC and will potentially advance the field of immunotherapeutic drug development to improve clinical outcomes in NMIBC.

cancer biology↗