Katsutoshi Oda

PLK1 or WEE1 inhibition targets homologous recombination repair proficiency in BRCA1/2 wild-type high-grade serous ovarian cancer

Abstract High-grade serous ovarian cancer (HGSOC) is a poor prognostic disease, especially in BRCA1 / 2 wild-type (BRCA-WT) patients with homologous recombination (HR) proficiency. These patients often show limited response to both platinum-based chemotherapy and PARP inhibitors. HR and non-homologous end joining (NHEJ) are the two major DNA double-strand break (DSB) repair pathways. HR is a precise repair mechanism for DSBs but is limited to S and G2 phases. In contrast, NHEJ functions more broadly throughout the cell cycle, including G1. We investigated whether inhibiting the G2/M checkpoint kinases PLK1 or WEE1 individually could disrupt mitotic control and expose therapeutic vulnerabilities in BRCA-WT/HR-proficient HGSOC cells. We evaluated cell cycle–targeted strategies to overcome HR-proficient chemoresistance using either volasertib (a selective PLK1 inhibitor) or adavosertib (a potent WEE1 inhibitor) in BRCA-WT/HR-proficient and BRCA-mutant/HR-deficient HGSOC models. Both agents induced DNA damage, impaired HR repair (reduced RAD51 foci), and triggered mitotic catastrophe—a form of cell death caused by defective mitosis and unresolved DNA damage—in BRCA-WT cells. Volasertib caused polyploidy and abnormal spindle formation, indicating mitotic slippage and cytokinesis failure, whereas adavosertib abrogated the G2/M checkpoint, forcing premature mitotic entry. In contrast, BRCA-mutant cells were resistant to either volasertib or adavosertib, consistent with sustained and functional NHEJ activity. This resistance was restored by the pharmacological or genetic inhibition of DNA-PKcs (DNA-dependent protein kinase, catalytic subunit), a prominent component of NHEJ. Functional and xenograft models confirmed selective vulnerability of BRCA-WT tumors to either PLK1 or WEE1 inhibition. Our work highlights a mechanistic framework linking cell cycle checkpoint inhibition to DNA repair pathway selectivity, providing a rationale for targeting mitotic regulators in HR-proficient ovarian cancer—a subgroup with high clinical unmet need.

DNA Methylation in Ovarian and Endometrial Cancers: Predictive and Mechanistic Roles in PARP Inhibitor and ICI Response

ABSTRACT Cancer treatment is shifting from an organ‐based approach to one driven by biological phenotypes, emphasizing the need to understand molecular mechanisms. DNA methylation plays a pivotal role in tumor biology, not only through gene silencing but also by inducing distinct behaviors beyond genetic mutations. In gynecologic cancers, molecular diagnostics, such as homologous recombination deficiency status guiding poly(ADP‐ribose) polymerase (PARP) inhibitor therapy in ovarian cancer and deficient mismatch repair/microsatellite instability‐high status informing immune checkpoint inhibitor (ICI) therapy in endometrial cancer have already been used in clinical practice. However, tumors with epigenetically driven functional deficiencies, such as BRCA1 promoter methylation in homologous recombination‐deficient ovarian cancers or MLH1 promoter methylation in deficient mismatch repair/microsatellite instability‐high endometrial cancers, often exhibit poorer prognoses and reduced therapeutic responses compared to their genetically mutated counterparts. Given the unique impact of DNA methylation, precise detection is crucial. Integrating methylation analysis into molecular classification could refine diagnostics—both by identifying mechanistic contributors to treatment response and by serving as predictive biomarkers for therapy selection—thereby optimizing patient management. This review explores the role of DNA methylation in modulating responses to PARP inhibitors and ICIs, highlights its promise as a biomarker in precision oncology, and outlines current developments and clinical challenges in BRCA1 and MLH1 methylation assays.

Cyclin E1 overexpression sensitizes ovarian cancer cells to WEE1 and PLK1 inhibition

Abstract Cyclin E1 (CCNE1) amplification is associated with poor prognosis of ovarian carcinomas across histological subtypes. Inhibitors targeting PLK1 or WEE1 are emerging as promising therapeutic agents for cancer treatment that disrupt the critical G2/M checkpoint, leading to cancer cell death. However, biomarkers that predict the response to these inhibitors are not well defined. Here, we evaluated the efficacy of the PLK1 inhibitor, volasertib, and the WEE1 inhibitor, adavosertib, along with the biomarker potential of cyclin E1 in ovarian cancer cells. Both inhibitors suppressed the proliferation of cyclin E1-overexpressing cells to a greater extent than that of cells exhibiting low cyclin E1 expression. TP53 silencing did not increase the sensitivity to these inhibitors. In cyclin E1-overexpressing cells, PLK1 inhibition reduced the proportion of cells in the G1 phase and increased those in the G2/M and sub-G1 phases. WEE1 inhibition reduced G1 phase cells without a clear peak in the S-G2/M phase and increased the sub-G1 phase cells. Both inhibitors suppressed the growth of cyclin E1-overexpressing tumors in vivo. Taken together, cyclin E1 overexpression, regardless of TP53 status, may serve as a predictive biomarker for the efficacy of these inhibitors, offering potential personalized treatment strategies for ovarian cancer.

Molecular classification of ovarian high-grade serous/endometrioid carcinomas through multi-omics analysis: JGOG3025-TR2 study

Considerable interobserver variability exists in diagnosis of ovarian high-grade endometrioid carcinoma (HGEC) and high-grade serous carcinoma (HGSC) due to histopathological similarities. While homologous recombination deficiency (HRD) correlates with drug sensitivity in HGSC, the molecular features of HGEC are unclear. Fresh-frozen samples from 15 ovarian HGECs and 274 ovarian HGSCs in the JGOG-TR2 cohort were submitted to targeted DNA sequencing, RNA sequencing, DNA methylation array, and SNP array. We additionally analyzed 555 ovarian HGSCs from TCGA-OV and 287 endometrial high-grade carcinomas from TCGA-UCEC. Unsupervised clustering using copy number signatures identified four distinct tumor groups (C1, C2, C3 and C4). C1 (n = 41) showed CCNE1 amplification and poor survival. C2 (n = 160) and C3 (n = 59) showed high BRCA1/2 alteration frequency with low and moderate ploidy, respectively. C4 (n = 22) was characterized by favorable outcome, higher HGEC proportion, no BRCA1/2 alteration or CCNE1 amplification, and low levels of HRD score, ploidy, intra-tumoral heterogeneity, cell proliferation rate, and WT1 gene expression. Notably, C4 exhibited a normal endometrium-like DNA methylation profile, thus, defined as "HGEC-type" tumors, which were also identified in TCGA-OV and TCGA-UCEC. Ovarian "HGEC-type" tumors present a non-HRD status, favorable prognosis, and endometrial differentiation, possibly constituting a subset of clinically diagnosed HGSCs.

Current status of hereditary breast and ovarian cancer practice among gynecologic oncologists in Japan: a nationwide survey by the Japan Society of Gynecologic Oncology (JSGO)

The practices pertaining to hereditary breast and ovarian cancer (HBOC) in Japan have been rapidly changing owing to the clinical development of poly(ADP-ribose) polymerase inhibitors, the increasing availability of companion diagnostics, and the broadened insurance coverage of HBOC management from April 2020. A questionnaire of gynecologic oncologists was conducted to understand the current status and to promote the widespread standardization of future HBOC management. A Google Form questionnaire was administered to the members of the Japan Society of Gynecologic Oncology. The survey consisted of 25 questions in 4 categories: respondent demographics, HBOC management experience, insurance coverage of HBOC management, and educational opportunities related to HBOC. A total of 666 valid responses were received. Regarding the prevalence of HBOC practice, the majority of physicians responded in the negative and required human resources, information sharing and educational opportunities, and expanded insurance coverage to adopt and improve HBOC practice. Most physicians were not satisfied with the educational opportunities provided so far, and further expansion was desired. They remarked on the psychological burdens of many HBOC managements. Physicians reported these burdens could be alleviated by securing sufficient time to engage in HBOC management, creating easy-to-understand explanatory material for patients, collaboration with specialists in genetic medicine, and educational opportunities. Gynecologic oncologists in Japan are struggling to deal with psychological burdens in HBOC practice. To promote the clinical practice of HBOC management, there is an urgent need to strengthen human resources and improve educational opportunities, and expand insurance coverage for HBOC management.

Phase II study of niraparib in recurrent or persistent rare fraction of gynecologic malignancies with homologous recombination deficiency (JGOG2052)

Poly (adenosine diphosphate)-ribose polymerase (PARP) inhibitors for tumors with homologous recombination deficiency (HRD), including pathogenic mutations in JGOG2052 is a single-arm, open-label, multi-center, phase 2 clinical trial to evaluate the efficacy and safety of niraparib monotherapy for a recurrent or persistent rare fraction of gynecologic malignancies with Japan Primary Registries Network (JPRN) Identifier: jRCT2031210264.

Genetic diagnosis of pseudomyxoma peritonei originating from mucinous borderline tumor inside an ovarian teratoma

Abstract Background Pseudomyxoma peritonei is a rare disease condition mainly caused by primary mucinous tumors from the appendix and rarely from the ovary, such as when mucinous ovarian tumors arise from within a teratoma. Molecular analyses of pseudomyxoma from the appendix showed that KRAS and GNAS pathogenic variants are common genetic features of pseudomyxoma peritonei. However, the origin of the tumors is difficult to be identified via genetic variants alone. This study presents a case of pseudomyxoma peritonei of ovarian origin, which was diagnosed by comprehensive genomic profiling with ploidy analysis in a series of primary, recurrent, and autopsy tumor specimens. Case presentation A 40-year-old woman was diagnosed with Stage IC2 mucinous ovarian tumor of borderline malignancy with mature cystic teratoma, upon clinical pathology. Immunohistochemical analysis suggested that the mucinous tumor was derived from the intestinal component of an ovarian teratoma. Three years later, intraperitoneal recurrence was detected, which subsequently progressed to pseudomyxoma peritonei. Genomic analysis detected KRAS (G12D), GNAS (R201C), and FBXW7 (R367*) variants in the primary tumor. In addition, the tumor showed aneuploidy with loss of heterozygosity (LOH) in all its chromosomes, which suggested that the primary ovarian tumor was derived from germ cells. Existence of one Barr body suggested the existence of uniparental disomy of the tumors throughout the genome, instead of a haploid genotype. All three pathogenic variants remained positive in the initial recurrent tumor, as well as in the paired DNA from the whole blood in pseudomyxoma peritonei. The pathogenic variant of KRAS (G12D) was also identified in the autopsy specimen of the appendix by droplet digital polymerase chain reaction. Conclusions This study pathologically and genetically confirmed that the primary ovarian borderline tumor was derived from the intestinal component of an ovarian teratoma, and that the subsequent pseudomyxoma peritonei progressed from the primary ovarian tumor. Integrative genomic analysis was useful to identify cellular origin of tumors, as well as to precisely interpret the process of disease progression.

Downregulation of HLA Class I Expression through HLA-A DNA Methylation Is Associated with Reduced CD8+ T-cell Infiltration in Cervical Cancer

Abstract Human leukocyte antigen class I (HLA-I) is central to tumor immune recognition, but its regulatory mechanisms in cervical cancer remain poorly understood. This study aimed to elucidate the impact of HLA-I regulatory mechanisms on CD8+ T-cell infiltration and identify distinct histotype-specific immune escape strategies across cervical cancer subtypes. Using 98 cervical cancer cases, including squamous cell carcinoma (SCC; n = 53), adenocarcinoma (n = 32), gastric-type adenocarcinoma (GAS; n = 5), small cell carcinoma (Small, n = 4), and mixed histologic types (n = 4), we examined the relationship between CD8+ T-cell infiltration patterns (categorized as infiltrated, excluded, or absent) and HLA-I expression, HLA-A DNA methylation, and HLA-I loss of heterozygosity (LOH). CD8+ T-cell infiltration patterns varied significantly by histologic subtype (P < 0.0001). SCC showed the highest frequency of the infiltrated pattern (73.6%), whereas GAS and Small predominantly displayed an absent pattern. Reduced CD8+ T-cell infiltration correlated with poor survival (P < 0.0001). HLA-I expression mirrored these trends being highest in SCC and lowest in Small and GAS. HLA-A DNA methylation emerged as a key driver of HLA-I downregulation, leading to reduced CD8+ infiltration (P < 0.05). In SCC, both HLA-A methylation and HLA-I LOH contributed to immune evasion; cases lacking these alterations exhibited the highest CD8+ T-cell infiltration levels (P < 0.01). This study identifies distinct HLA-I regulatory mechanisms in cervical cancer, highlighting HLA-A methylation—and particularly HLA-I LOH in SCC—as key drivers of immune evasion. These findings provide a foundation for developing predictive biomarkers and suggest that targeting these specific HLA-I regulatory mechanisms could enhance immunotherapy efficacy.