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Supplementary Data from B7-H3 Suppresses Antitumor Immunity via the CCL2–CCR2–M2 Macrophage Axis and Contributes to Ovarian Cancer Progression

New approaches beyond PD-1/PD-L1 inhibition are required to target the immunologically diverse tumor microenvironment (TME) in high-grade serous ovarian cancer (HGSOC). In this study, we explored the immunosuppressive effect of B7-H3 (CD276) via the CCL2–CCR2–M2 macrophage axis and its potential as a therapeutic target. Transcriptome analysis revealed that B7-H3 is highly expressed in PD-L1–low, nonimmunoreactive HGSOC tumors, and its expression negatively correlated with an IFNγ signature, which reflects the tumor immune reactivity. In syngeneic mouse models, B7-H3 (Cd276) knockout (KO) in tumor cells, but not in stromal cells, suppressed tumor progression, with a reduced number of M2 macrophages and an increased number of IFNγ+CD8+ T cells. CCL2 expression was downregulated in the B7-H3 KO tumor cell lines. Inhibition of the CCL2–CCR2 axis partly negated the effects of B7-H3 suppression on M2 macrophage migration and differentiation, and tumor progression. In patients with HGSOC, B7-H3 expression positively correlated with CCL2 expression and M2 macrophage abundance, and patients with B7-H3–high tumors had fewer tumoral IFNγ+CD8+ T cells and poorer prognosis than patients with B7-H3–low tumors. Thus, B7-H3 expression in tumor cells contributes to CCL2–CCR2–M2 macrophage axis–mediated immunosuppression and tumor progression. These findings provide new insights into the immunologic TME and could aid the development of new therapeutic approaches against the unfavorable HGSOC phenotype.

Serous carcinoma of the uterus (USC) is a pathological subtype of high-grade endometrial cancers, with no effective treatment for advanced cases. Since such refractory tumors frequently harbor antitumor immune tolerance, many immunotherapies have been investigated for various malignant tumors using immuno-competent animal models mimicking their local immunities. In this study, we established an orthotopic mouse model of high-grade endometrial cancer and evaluated the local tumor immunity to explore the efficacy of immunotherapies against USC. A multivariate analysis of 62 human USC cases revealed that the tumor-infiltrating cell status, few CD8+ cells and abundant myeloid-derived suppressor cells (MDSCs), was an independent prognostic factor (P < 0.005). A murine endometrial cancer cell (mECC) was obtained from C57BL/6 mice via endometrium-specific deletion of Pten and Tp53, and another high-grade cell (HPmECC) was established by further overexpressing Myc in mECCs. HPmECCs exhibited higher capacities of migration and anchorage-independent proliferation than mECCs (P < 0.01, P < 0.0001), and when both types of cells were inoculated into the uterus of C57BL/6 mice, the prognosis of mice bearing HPmECC-derived tumors was significantly poorer (P < 0.001). Histopathological analysis of HPmECC orthotopic tumors showed serous carcinoma-like features with prominent tumor infiltration of MDSCs (P < 0.05), and anti-Gr-1 antibody treatment significantly prolonged the prognosis of HPmECC-derived tumor-bearing mice (P < 0.05). High CCL7 expression was observed in human USC and HPmECC, and MDSCs migration was promoted in a CCL7 concentration-dependent manner. These results indicate that antitumor immunity is suppressed in USC due to increased number of tumor-infiltrating MDSCs via CCL signal.

New approaches beyond PD-1/PD-L1 inhibition are required to target the immunologically diverse tumor microenvironment (TME) in high-grade serous ovarian cancer (HGSOC). In this study, we explored the immunosuppressive effect of B7-H3 (CD276) via the CCL2–CCR2–M2 macrophage axis and its potential as a therapeutic target. Transcriptome analysis revealed that B7-H3 is highly expressed in PD-L1–low, nonimmunoreactive HGSOC tumors, and its expression negatively correlated with an IFNγ signature, which reflects the tumor immune reactivity. In syngeneic mouse models, B7-H3 (Cd276) knockout (KO) in tumor cells, but not in stromal cells, suppressed tumor progression, with a reduced number of M2 macrophages and an increased number of IFNγ+CD8+ T cells. CCL2 expression was downregulated in the B7-H3 KO tumor cell lines. Inhibition of the CCL2–CCR2 axis partly negated the effects of B7-H3 suppression on M2 macrophage migration and differentiation, and tumor progression. In patients with HGSOC, B7-H3 expression positively correlated with CCL2 expression and M2 macrophage abundance, and patients with B7-H3–high tumors had fewer tumoral IFNγ+CD8+ T cells and poorer prognosis than patients with B7-H3–low tumors. Thus, B7-H3 expression in tumor cells contributes to CCL2–CCR2–M2 macrophage axis–mediated immunosuppression and tumor progression. These findings provide new insights into the immunologic TME and could aid the development of new therapeutic approaches against the unfavorable HGSOC phenotype.

Uterine serous carcinoma (USC) is a highly aggressive histological subtype of endometrial cancers harboring highly metastatic and chemoresistant features. Our previous study showed that STAT1 is highly expressed in USC and acts as a key molecule that is positively correlated with tumor progression, but it remains unclear whether STAT1 is relevant to the malicious chemorefractory nature of USC. In the present study, we investigated the regulatory role of STAT1 toward platinum-cytotoxicity in USC. STAT1 suppression sensitized USC cells to increase cisplatin-mediated apoptosis (p < 0.001). Furthermore, phosphorylation of STAT1 was prominently observed on serine-727 (pSTAT1-Ser727), but not on tyrosine-701, in the nucleus of USC cells treated with cisplatin. Mechanistically, the inhibition of pSTAT1-Ser727 by dominant-negative plasmid elevated cisplatin-mediated apoptosis by increasing intracellular accumulation of cisplatin through upregulation of CTR1 expression. TBB has an inhibitory effect on casein kinase 2 (CK2), which phosphorylate STAT1 at serine residues. Sequential treatment with TBB and cisplatin on USC cells greatly reduced nuclear pSTAT1-Ser727, enhanced intracellular accumulation of cisplatin, and subsequently increased apoptosis. Tumor load was significantly reduced by combination therapy of TBB and cisplatin in in vivo xenograft models (p < 0.001). Our results collectively suggest that pSTAT1-Ser727 may play a key role in platinum resistance as well as tumor progression in USC. Thus, targeting the STAT1 pathway via CK2 inhibitor can be a novel method for attenuating the chemorefractory nature of USC.

Reported here is a case of Mullerian adenosarcoma of the ovary which contained a primitive neuroectodermal tissue component within the stroma. The adenosarcoma coexisted with clear cell adenocarcinoma in an endometriotic cyst. The patient was a 33-year-old woman with a large unilocular endometriotic cyst of the right ovary. On the internal wall of the cyst, both a plaque-like protrusion with a papillary surface and a dome-like mural nodule were noted. The former exhibited features of Mullerian adenosarcoma, and the latter showed those of clear cell adenocarcinoma. In the deeper portion of adenosarcoma, teratoma-like tissue which contained various tissue components including primitive neuroectodermal tissue was found. The presence of primitive neuroectodermal tissue in the stroma of adenosarcoma suggested the diagnosis of 'adenosarcoma with neuroectodermal differentiation' ('teratoid adenosarcoma'), although the possibility of the incidental occurrence of an immature teratoma could not be completely excluded.

Reported here is a case of Müllerian adenosarcoma of the ovary which contained a primitive neuroectodermal tissue component within the stroma. The adenosarcoma coexisted with clear cell adenocarcinoma in an endometriotic cyst. The patient was a 33-year-old woman with a large unilocular endometriotic cyst of the right ovary. On the internal wall of the cyst, both a plaque-like protrusion with a papillary surface and a dome-like mural nodule were noted. The former exhibited features of Müllerian adenosarcoma, and the latter showed those of clear cell adenocarcinoma. In the deeper portion of adenosarcoma, teratoma-like tissue which contained various tissue components including primitive neuroectodermal tissue was found. The presence of primitive neuroectodermal tissue in the stroma of adenosarcoma suggested the diagnosis of 'adenosarcoma with neuroectodermal differentiation' ('teratoid adenosarcoma'), although the possibility of the incidental occurrence of an immature teratoma could not be completely excluded.