Background Current cancer immunotherapies have made tremendous impacts but generally lack high response rates, especially in ovarian cancer. New therapies are needed to provide increased benefits. One understudied approach is to target the large population of immunosuppressive tumor-associated macrophages (TAMs). Using inducible transgenic mice, we recently reported that upregulating nuclear factor-kappaB (NF-κB) signaling in TAMs promotes the M1, anti-tumor phenotype and limits ovarian cancer progression. We also developed a mannose-decorated polymeric nanoparticle system (MnNPs) to preferentially deliver siRNA payloads to M2, pro-tumor macrophages in vitro. In this study, we tested a translational strategy to repolarize ovarian TAMs via MnNPs loaded with siRNA targeting the inhibitor of NF-κB alpha (IκBα) using mouse models of ovarian cancer. Methods We evaluated treatment with MnNPs loaded with IκBα siRNA (IκBα-MnNPs) or scrambled siRNA in syngeneic ovarian cancer models. ID8 tumors in C57Bl/6 mice were used to evaluate consecutive-day treatment of late-stage disease while TBR5 tumors in FVB mice were used to evaluate repetitive treatments in a faster-developing disease model. MnNPs were evaluated for biodistribution and therapeutic efficacy in both models. Results Stimulation of NF-κB activity and repolarization to an M1 phenotype via IκBα-MnNP treatment was confirmed using cultured luciferase-reporter macrophages. Delivery of MnNPs with fluorescent payloads (Cy5-MnNPs) to macrophages in the solid tumors and ascites was confirmed in both tumor models. A three consecutive-day treatment of IκBα-MnNPs in the ID8 model validated a shift towards M1 macrophage polarization in vivo. A clear therapeutic effect was observed with biweekly treatments over 2-3 weeks in the TBR5 model where significantly reduced tumor burden was accompanied by changes in immune cell composition, indicative of reduced immunosuppressive tumor microenvironment. No evidence of toxicity associated with MnNP treatment was observed in either model. Conclusions In mouse models of ovarian cancer, MnNPs were preferentially associated with macrophages in ascites fluid and solid tumors. Evidence of macrophage repolarization, increased inflammatory cues, and reduced tumor burden in IκBα-MnNP-treated mice indicate beneficial outcomes in models of established disease. We have provided evidence of a targeted, TAM-directed approach to increase anti-tumor immunity in ovarian cancer with strong translational potential for future clinical studies.

Breast cancer is the most diagnosed cancer in the U.S., with a 5-year survival rate of less than 30% for patients with distant metastases. Bone metastases are present in over 70% of metastatic breast cancer patients, and current treatments treat the symptoms of osteolytic bone metastasis (OBM), but do not improve survival rates. OBM is characterized by an increase in osteoclast proliferation and bone-resorbing activity. Moreover, receptor tyrosine kinase, Ephrin-type-A 2 receptor (EphA2), is highly expressed in bone metastases, and previous evidence suggests its involvement in OBM and anti-tumor immunity. EphA2 participates in both forward and reverse signaling during receptor/ligand engagement and mediates various biological processes such as tissue organization and homeostasis and inflammation, as well as oncogenic processes like epithelial-mesenchymal transition. However, the mechanism by which EphA2 mediates the expansion of osteoclasts is not well understood. Analysis of transcriptomic data of patients with bone metastases in The Metastatic Breast Cancer Project (Provisional, December 2021) resulted in over 3500 genes that significantly correlated with EphA2 expression (Spearman's Correlation ≥ 0.35). Using a publicly available Gene Ontology reference list for myeloid differentiation, we identified 155 genes that have a significant positive correlation with EphA2 expression. To assess the effect of EphA2 expression on genes associated with osteoclasts, we compared the same samples to reference lists for osteoclast differentiation and proliferation. We identified 17 genes of interest that significantly correlate with EphA2 expression, further underscoring the possible involvement of EphA2 in OBM. We then compared the patients without bone metastases to the same osteoclast reference lists and found no significant correlations. We hypothesize that increased expression of EphA2 in breast cancer cells at the site of bone metastasis promotes osteoclast expansion, leading to OBM. We aim to investigate EphA2 reverse signaling in myeloid progenitor cells, osteoclasts, and bone metastasis-associated macrophages. We will utilize breast cancer mouse models to elucidate the effects of EphA2 inhibition on immune cell populations, bone metastasis, and tumor progression. We aim to reduce OBM and tumor burden by reducing the expansion of osteoclasts and shifting the immune cells to an anti-tumorigenic phenotype, which will offer new treatment strategies for osteolytic breast cancer. Citation Format: Dominique Parker, Verra Ngwa, Logan Northcutt, Natalie Bennett, Erik Beadle, Jade Miller, JIn Chen, Julie Rhoades. EphA2 Expression in Breast Cancer Mediates Osteoclast Expansion and Promotes Osteolytic Bone Metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1324.

Background: Ovarian cancer is the most lethal gynecologic malignancy, with a 5-year survival rate of less than 50%. To have a major impact on improving clinical outcomes, a better understanding of the progression of disease and identification of truly novel treatment strategies is critical. Canonical nuclear factor-kappaB (NF-κB) signaling has been extensively studied in preclinical ovarian cancer models; however, systemic NF-κB inhibitors have had disappointing results in early clinical trials. Whether the alternative, non-canonical NF-κB signaling pathway (nc-NF-κB) represents a distinct and improved target for therapy in ovarian cancer is unknown. Here, we aim to investigate the role played by nc-NF-κB signaling both in malignant epithelial cells and in macrophages, a key immune cell component in the tumor microenvironment. Repolarizing tumor-associated macrophages (TAMs) away from pro-tumor M2-like functions towards an anti-tumor M1-like phenotype is a critical priority in macrophage-directed therapies. Methods: In ovarian cancer cell lines, mouse ovarian TAMs cultured ex vivo, and immortalized bone marrow-derived macrophages (BMDMs), nuclear levels of p52 were measured by western blot as a read-out of active nc-NF-κB signaling. Effects of macrophage polarization on nc-NF-κB signaling were determined in unpolarized (M0), M1 polarized (LPS/IFNγ treated) or M2 polarized (IL-4 treated) BMDMs. Finally, effects of inhibiting nc-NF-κB using a specific peptide inhibitor of p52 nuclear import (SN52) on cancer cell growth and macrophage phenotype were determined in sulforhodamine B growth assays and by western blot analysis of PCNA (proliferation marker) and arginase-1 (M2 macrophage marker). Results: We observed high levels of p52 expression in the majority of ovarian cancer cell lines, and in our cultured macrophage models. The functional relevance of these observations was confirmed by experiments showing reduced growth in ovarian cancer cells treated with SN52 and reduced expression of arginase-1 in SN52-treated macrophages. We saw similar results in breast cancer cells and mouse mammary TAMs, showing that nc-NF-κB signaling may also have pro-tumor effects in other cancer types. Complementary studies showed that M2 polarized macrophages expressed markedly higher levels of nuclear p52 than observed in M0 or M1 cells. Based on these promising results, experiments (i) using transgenic mice to allow targeted, inducible activation of nc-NF-κB in macrophages during ovarian cancer progression and (ii) testing the therapeutic effects of SN52 in these cancer models are underway. Conclusions: Although further studies are required to establish the translational relevance of our findings, we hope to identify non-canonical NF-κB signaling as a new therapeutic target in malignant epithelium and macrophages in ovarian cancer and potentially other cancer types. Citation Format: Andrew J. Wilson, Dominique Parker, Robert Cheng, Todd Giorgio, Marta Crispens, Fiona Yull. Investigating the role of non-canonical NF-kappaB signaling in tumor cells and macrophages in ovarian cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4973.

Tumor associated macrophages (TAMs) often exist in high densities in breast tumors and are associated with adverse clinical outcomes. TAM repolarization as a strategy to shift the breast cancer microenvironment from immunosuppressive to immunostimulatory is an active area of research. The canonical and non-canonical NfkappaB (NFkB) signaling pathways represent potential points of intervention to influence TAM phenotypes. We have found that upregulation of the canonical NFkB signaling pathway specifically in macrophages can be used to repolarize TAMs toward an M1, anti-tumor phenotype. Using our doxycycline inducible mouse model termed IKFM, we are exploring the effects of macrophage specific upregulation of NFkB signaling on different stages of tumor growth and metastasis. In studies using the IKFM mouse model, we found that doxycycline-induced NFkB activation in macrophages in established orthotopic mammary tumors has therapeutic effects on tumor outcomes. Compared to control mice, we found that IKFM mice have reduced tumor burden in the lung, indicating prevention of metastasis. Ongoing studies are focused on understanding how macrophage specific activation of NFkB influences the metastatic niches of lung and bone; two of the most common sites of breast cancer metastasis. To move our findings towards clinical translation, we have developed an M2-macrophage targeted nanoparticle that activates NFkB signaling by delivering an siRNA against IkappaBalpha, an inhibitor of the pathway. The M2 targeted nanoparticle is currently being tested in murine models of breast cancer metastasis to both lung and bone to translate our findings from the IKFM mouse model to a pharmacological manipulation. Citation Format: Kennady K. Bullock, Dominique Parker, Evan B. Glass, Alyssa Hoover, Alyssa Merkel, Richard Maynard, Andrew Wilson, Todd Giorgio, Julie A. Rhoades, Fiona E. Yull. Modulation of NFkappaB signaling influences tumor associated macrophage phenotypes in murine models of breast 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 2728.