Yoshinao Oda

Tumor Microenvironments in Malignant Ovarian Germ Cell Tumors: MHC Class I Loss and T‐Cell Exhaustion in Dysgerminoma

ABSTRACT Malignant ovarian germ cell tumors are rare neoplasms primarily affecting young women. Although generally responsive to chemotherapy, long‐term adverse effects remain a concern. Improved understanding of the tumor microenvironment may reveal alternative therapeutic strategies; however, comprehensive analyses in malignant ovarian germ cell tumors remain limited. We analyzed 56 malignant ovarian germ cell tumor samples: 23 dysgerminomas, 14 yolk sac tumors, and 19 immature teratomas. Immune cell infiltration and immune checkpoint molecule expression were evaluated via immunohistochemistry, while immune‐related gene expression was assessed using transcriptomic profiling. In dysgerminoma, T‐cell exhaustion was characterized through multiplex immunofluorescence. Major histocompatibility complex class I expression was assessed across all subtypes. Dysgerminomas showed abundant CD4 + and CD8 + T‐cell, B‐cell, and M1 macrophage infiltration, with the presence of tertiary lymphoid structures, indicating an immunologically active “hot tumor” phenotype. Immune checkpoint molecules were upregulated, and transcriptomic analysis revealed enrichment of immunostimulatory and immunosuppressive pathways. Conversely, yolk sac tumors were dominated by M2 macrophages, while immature teratomas exhibited minimal immune cell infiltration, a “cold tumor” feature. In dysgerminomas with high programmed cell death protein 1 levels, most CD8 + T cells exhibited a nonexhausted phenotype. All tumor subtypes showed loss of major histocompatibility complex class I expression. These findings indicate that malignant ovarian germ cell tumor subtypes harbor distinct tumor microenvironments, with dysgerminoma characterized by abundant but potentially ineffective T‐cell responses owing to absent major histocompatibility complex class I–mediated antigen presentation. Therapeutic strategies restoring major histocompatibility complex class I expression may enhance T cell–based immunotherapy efficacy in dysgerminomas.

Loss of SMARCA4 induces sarcomatogenesis through epithelial–mesenchymal transition in ovarian carcinosarcoma

AbstractOvarian carcinosarcoma (OCS) is a rare and aggressive tumor, and the development of its sarcomatous component is believed to be due to epithelial–mesenchymal transition (EMT). The SWIch/sucrose nonfermentable chromatin remodeling factor (CRF) is closely related to EMT; however, the relationship between CRF and EMT in OCS remains unclear. In this study, we analyzed the protein expression of CRFs, including ARID1A and SMARCA4, and their downstream mRNA expression in 28 OCS cases, two fallopian tube CS cases, and one peritoneal CS case. ARID1A and SMARCA4 exhibited a histological type‐specific loss of protein expression in 5 of 11 (45%) endometrioid cases and all 5 serous/homologous OCS cases, respectively. The mRNA analysis suggested that sarcomatogenesis is induced by the transforming growth factor‐β and Hippo signaling pathways, both of which regulate YAP1. Immunostaining for YAP1 suggested YAP1‐associated sarcomatogenesis in the CRF‐retained group, whereas YAP1‐unassociated sarcomatogenesis was suggested in the CRF‐reduced group. High‐grade serous carcinoma cell line experiments showed that the transcriptome of the SMARCA4‐knockdown group showed lower expression of the epithelial gene CDH1 and higher expression of mesenchymal genes such as VIM, ZEB1, and SNAI1 than the control group. Moreover, cell adhesion disappeared and cell morphology changed to a spindle shape, indicating sarcomatogenesis. In conclusion, this study reveals a mechanism for sarcoma development in OCS and provides novel therapeutic possibilities.

Endometrial endometrioid carcinoma, grade 1, is more aggressive in the elderly than in the young

AimsThe aim of this study was to characterise grade 1 (G1) endometrioid carcinoma in the elderly, by using clinicopathological features and immunohistochemical features of surrogate markers of molecular subtypes.Methods and resultsWe retrospectively analysed tumour samples from 268 patients with G1 endometrioid carcinoma (<40 years, n = 24; 40–59 years, n = 169; ≥60 years, n = 75) for whom long‐term clinical follow‐up data were available. G1 endometrioid carcinoma in the elderly (≥60 years) was characterised by frequent deep myometrial invasion, less frequent endometrioid intraepithelial neoplasia (EIN), lack of benign hyperplasia (BH), less frequent squamous differentiation, and occasional aberrant p53 expression. In contrast, this condition in the young (<40 years) was characterised by frequent EIN, BH, and squamous differentiation. Univariate analysis revealed that elderly status (≥60 years), International Federation of Obstetrics and Gynecology (FIGO) 2009 stage and aberrant p53 expression were significantly associated with shorter progression‐free survival, and multivariate analysis revealed that elderly status and FIGO 2009 stage were independently associated with a poor prognosis.ConclusionsG1 endometrioid carcinoma in the elderly is more aggressive than that in the young, and elderly status is an independent predictor of shorter progression‐free survival in this condition. We propose that type 1 tumours can be subdivided into type 1a (young age at onset and indolent) and type 1b (old age at onset and relatively aggressive).

Claudin‐18 expression in gastric type adenocarcinoma and HPV ‐associated adenocarcinoma of the uterine cervix

Aims Claudin‐18 (CLDN18) is both a marker for the gastric phenotype and a therapeutic target. However, little is known about its immunoexpression in endocervical adenocarcinomas (ECAs), particularly as detected using the clone 43‐14A antibody, or about the gene expression of its isoforms in ECAs. Methods and results We examined CLDN18, HIK1083, p16 and Rb expression by immunohistochemistry and high‐risk human papillomavirus (HR‐HPV) mRNA by in situ hybridization (ISH) in 121 ECAs, including 35 HPV‐independent adenocarcinomas (gastric type [GAS], n  = 24; non‐GAS, n  = 11) and 86 HPV‐associated ECAs. We also analysed mRNA expression of the CLDN18.1 (lung type) and CLDN18.2 (gastric type) isoforms by quantitative polymerase chain reaction (qPCR) in selected cases. CLDN18 positivity was detected in 8/24 (33%) GASs, 0/11 (0%) non‐GASs and 2/86 (2%) HPV‐associated ECAs, with positivity defined as staining in ≥75% of tumour cells, as in gastric cancer. When a 5% cut‐off was used, CLDN18 positivity was detected in 22/24 (92%) GASs, 0/11 (0%) non‐GASs and 6/86 (7%) HPV‐associated ECAs; CLDN18 expression was thus significantly associated with GAS histology ( P  < 0.0001). Among the 6 cases of HPV‐associated ECAs with CLDN18 expression (ranging from 5% to 80%), the histological patterns included a mix of usual and mucinous features in 4 cases, pure usual type in 1 and villoglandular variant in 1. Otherwise features such as p16 overexpression and the Rb partial loss pattern were consistent with those of HPV‐associated ECAs. Six of 22 (27%) CLDN18‐positive GASs were also positive for p16, but their other features—such as CLDN18 expression and the Rb preserved pattern—were the same as in p16 negative GASs. Expression of CLDN18.2 mRNA but not CLDN18.1 mRNA was confirmed in both GASs and HPV‐associated ECAs. Conclusions CLDN18 (43‐14A) emerged as a potential diagnostic and therapeutic marker for GAS. A minor subset of HPV‐associated ECAs also can be immunoreactive for CLDN18 and express CLDN18.2 mRNA, suggesting divergent gastric phenotypic differentiation. The caution is that GAS and HPV‐associated ECAs can share overlapping histological features and similar expression of CLDN18 and p16.

Immunohistochemical p16 overexpression and Rb loss correlate with high‐risk human papillomavirus infection in endocervical adenocarcinomas

Aimsp16 is a sensitive surrogate marker for transcriptionally active high‐risk human papillomavirus (HR‐HPV) infection in endocervical adenocarcinoma (ECA); however, its specificity is not perfect.Methods and resultsWe examined p16 and Rb expressions by immunohistochemistry (IHC) and the transcriptionally active HR‐HPV infection by mRNA in‐situ hybridisation (ISH) with histological review in 108 ECA cases. Thirteen adenocarcinomas of endometrial or equivocal origin (six endometrioid and seven serous carcinomas) were compared as the control group. HR‐HPV was detected in 83 of 108 ECA cases (77%), including five HPV‐associated adenocarcinomas in situ and 78 invasive HPV‐associated adenocarcinomas. All 83 HPV‐positive cases showed consistent morphology, p16 positivity and partial loss pattern of Rb. Among the 25 cases of HPV‐independent adenocarcinoma, four (16%) were positive for p16, and of these four cases, three of 14 (21%) were gastric type adenocarcinomas and one of 10 (10%) was a clear cell type adenocarcinoma. All 25 HPV‐independent adenocarcinomas showed preserved expression of Rb irrespective of the p16 status. Similarly, all 13 cases of the control group were negative for HR‐HPV with preserved expression of Rb, even though six of 13 (46%) cases were positive for p16. Compared with p16 alone, the combination of p16 overexpression and Rb partial loss pattern showed equally excellent sensitivity (each 100%) and improved specificity (100 versus 73.6%) and positive predictive values (100 versus 89.2%) in the ECA and control groups. Furthermore, HR‐HPV infection correlated with better prognosis among invasive ECAs.ConclusionsThe results suggest that the combined use of p16 and Rb IHC could be a reliable method to predict HR‐HPV infection in primary ECAs and mimics. This finding may contribute to prognostic prediction and therapeutic strategy.