Sunila Pradeep

eIF4E Enriched Extracellular Vesicles Induce Immunosuppressive Macrophages through HMGCR‐Mediated Metabolic Rewiring

Abstract Tumor driven immune suppression poses a significant impediment to the success of immunotherapy in ovarian cancer. Among the various mechanisms contributing to immune suppression, intracellular communication facilitated by tumor‐derived extracellular vesicles (EVs) within the tumor microenvironment emerges as a pivotal factor influencing tumor growth. Here, it is demonstrated that extracellular vesicle‐packaged eIF4E from tumor cells alters protein translation in macrophages, contributing to antitumor immune response. Mechanistically, tumor derived EV‐packaged eIF4E significantly enhances the expression of 3‐hydroxy‐3‐methyl‐glutaryl‐coenzyme A reductase (HMGCR), driving the synthesis and secretion of cholesterol. This, in turn, activates macrophages and causes immunosuppression through the X‐box binding protein 1 and Programmed death‐ligand 1 (XBP1/PD‐L1) axis. Strikingly, both genetic and pharmacological depletion of HMGCR in macrophages effectively restores their antitumor activity. Clinically, elevated HMGCR expression in tumor‐associated macrophages is associated with poor survival outcomes in ovarian cancer patients. The pivotal role of eIF4E is underscored here as a key signaling mediator, facilitating the communication between tumor and immune cells via EVs to promote immune suppression and suggesting HMGCR as a potential therapeutic target for tumor immunotherapy.

Peritoneal Spread of Ovarian Cancer Harbors Therapeutic Vulnerabilities Regulated by FOXM1 and EGFR/ERBB2 Signaling

Abstract Peritoneal spread is the primary mechanism of metastasis of ovarian cancer, and survival of ovarian cancer cells in the peritoneal cavity as nonadherent spheroids and their adherence to the mesothelium of distant organs lead to cancer progression, metastasis, and mortality. However, the mechanisms that govern this metastatic process in ovarian cancer cells remain poorly understood. In this study, we cultured ovarian cancer cell lines in adherent and nonadherent conditions in vitro and analyzed changes in mRNA and protein levels to identify mechanisms of tumor cell survival and proliferation in adherent and nonadherent cells. EGFR or ERBB2 upregulated ZEB1 in nonadherent cells, which caused resistance to cell death and increased tumor-initiating capacity. Conversely, Forkhead box M1 (FOXM1) was required for the induction of integrin β1, integrin-α V, and integrin-α 5 for adhesion of cancer cells. FOXM1 also upregulated ZEB1, which could act as a feedback inhibitor of FOXM1, and caused the transition of adherent cells to nonadherent cells. Strikingly, the combinatorial treatment with lapatinib [dual kinase inhibitor of EGFR (ERBB1) and ERBB2] and thiostrepton (FOXM1 inhibitor) reduced growth and peritoneal spread of ovarian cancer cells more effectively than either single-agent treatment in vivo. In conclusion, these results demonstrate that FOXM1 and EGFR/ERBB2 pathways are key points of vulnerability for therapy to disrupt peritoneal spread and adhesion of ovarian cancer cells. Significance: This study describes the mechanism exhibited by ovarian cancer cells required for adherent cell transition to nonadherent form during peritoneal spread and metastasis.

NRG1/ERBB3 Pathway Activation Induces Acquired Resistance to XPO1 Inhibitors

Abstract XPO1 inhibitors have shown promise in cancer treatment, but mechanisms of resistance to these drugs are not well understood. In this study, we established selective inhibitors of nuclear export (SINE)-resistant ovarian cancer cell lines from in vivo mouse tumors and determined the mechanisms of adaptive XPO1 inhibitor resistance using protein and genomic arrays. Pathway analyses revealed upregulation of the NRG1/ERBB3 pathway in SINE-resistant cells. Depletion of ERBB3 using siRNAs restored the antitumor effect of SINE in vitro and in vivo. Furthermore, exogenous NRG1 decreased the antitumor effect of SINE in ovarian cancer cell lines with high ERBB3 expression, but not in those with low expression. These results suggest that NRG1 and ERBB3 expression is a potential biomarker of response to SINE treatment. The antitumor effect of SINE was reduced by exogenous NRG1 in an ERBB3-dependent manner. These findings suggest that NRG1 and ERBB3 are effective biomarkers that should be evaluated in future clinical trials and are relevant therapeutic targets for the treatment of SINE-resistant cancers.

Oncostatin M Receptor–Targeted Antibodies Suppress STAT3 Signaling and Inhibit Ovarian Cancer Growth

Abstract Although patients with advanced ovarian cancer may respond initially to treatment, disease relapse is common, and nearly 50% of patients do not survive beyond five years, indicating an urgent need for improved therapies. To identify new therapeutic targets, we performed single-cell and nuclear RNA-seq data set analyses on 17 human ovarian cancer specimens, revealing the oncostatin M receptor (OSMR) as highly expressed in ovarian cancer cells. Conversely, oncostatin M (OSM), the ligand of OSMR, was highly expressed by tumor-associated macrophages and promoted proliferation and metastasis in cancer cells. Ovarian cancer cell lines and additional patient samples also exhibited elevated levels of OSMR when compared with other cell types in the tumor microenvironment or to normal ovarian tissue samples. OSMR was found to be important for ovarian cancer cell proliferation and migration. Binding of OSM to OSMR caused OSMR–IL6ST dimerization, which is required to produce oncogenic signaling cues for prolonged STAT3 activation. Human monoclonal antibody clones B14 and B21 directed to the extracellular domain of OSMR abrogated OSM-induced OSMR–IL6ST heterodimerization, promoted the internalization and degradation of OSMR, and effectively blocked OSMR-mediated signaling in vitro. Importantly, these antibody clones inhibited the growth of ovarian cancer cells in vitro and in vivo by suppressing oncogenic signaling through OSMR and STAT3 activation. Collectively, this study provides a proof of principle that anti-OSMR antibody can mediate disruption of OSM-induced OSMR–IL6ST dimerization and oncogenic signaling, thus documenting the preclinical therapeutic efficacy of human OSMR antagonist antibodies for immunotherapy in ovarian cancer. Significance: This study uncovers a role for OSMR in promoting ovarian cancer cell proliferation and metastasis by activating STAT3 signaling and demonstrates the preclinical efficacy of antibody-based OSMR targeting for ovarian cancer treatment.

Tumor Derived Extracellular Vesicles Drive T Cell Exhaustion in Tumor Microenvironment through Sphingosine Mediated Signaling and Impacting Immunotherapy Outcomes in Ovarian Cancer

AbstractSPHK1 (sphingosine kinase‐1) catalyzes the phosphorylation of sphingosine to sphingosine‐1‐phosphate (S1P), is found to be highly expressed in solid tumors. Here, extracellular vesicles (EVs) are identified as the key transporters of SPHK1 to the tumor microenvironment. Consequently, SPHK1‐packaged EVs elevate S1P levels in the tumor microenvironment, where S1P appears as an immunosuppressive agent. However, the exact mechanism of how S1P mediates its immunosuppressive effects in cancer is not understood. It is investigated that S1P can induce T cell exhaustion. S1P can also upregulate programmed death ligand‐1 (PDL‐1) expression through E2F1‐mediated transcription. Notably, an SPHK1 inhibitor PF543 improves T cell‐mediated cytotoxicity. Furthermore, combining PF543 with an anti‐PD‐1 antibody reduces tumor burden and metastasis more effectively than PF543 alone in vivo. These data demonstrate a previously unrecognized mechanism of how SPHK1‐packaged EVs contribute to the progression of ovarian cancer and thus present the potential clinical application of inhibiting SPHK1/S1P signaling to improve immune checkpoint blockage (anti‐PD‐1 antibody) therapy in ovarian cancer.