Ryo Tamura

Genomic profiling of meiotic errors and early malignant transformation events in ovarian mature teratoma

Abstract Ovarian mature teratoma (OMT) exhibits copy-neutral loss of heterozygosity (CN-LOH) derived from meiotic errors. Studies have classified OMT into five types using these CN-LOH patterns. However, tumor purity issues have hindered accurate classification and molecular characterization. Moreover, the relationship between OMT genomic abnormalities and malignant transformation remains unclear. Here, we used laser microdissection to selectively collect 29 epithelial regions from 22 OMT cases and 1 carcinoma in situ (CIS) region from a squamous cell carcinoma case arising from OMT. We then conducted whole-exome sequencing. Copy number analysis enabled classification according to the established system. In cases with multi-regional sampling, the CN-LOH patterns were identical within the same tumor, while bilateral tumors showed distinct patterns, indicating that each tumor originated independently. Among the type II OMTs, which are believed to result from meiosis II error, 2 cases exhibited a chromosomal gain. Assessment of heterozygosity suggested that these cases had meiosis I error before meiosis II error. Somatic mutation analysis revealed an extremely low mutation burden, with 1 case harboring a PIK3CA mutation. In the CIS region, additional copy number alterations were present alongside the underlying CN-LOH pattern. TP53 mutations and loss of the wild-type allele were detected. The tumor mutation burden of CIS was 6.2 mutations per megabase. Mutational signature analysis showed enrichment of apolipoprotein B mRNA editing enzyme catalytic subunit-associated signatures. This study suggests novel perspectives on the mechanisms of OMT tumor development and malignant transformation.

A retrospective study of Pipelle endometrial biopsy for ovarian, fallopian tube, and peritoneal cancers

Although the Pipelle endometrial biopsy is widely performed as a practical and minimally invasive test for endometrial disease(s), its effectiveness in ovarian cancer has not been explored. The aim of the present study was to evaluate the results of Pipelle endometrial biopsy for ovarian, fallopian tube, and peritoneal cancers. A pre-treatment Pipelle-endometrial biopsy was performed in 90 patients with ovarian, fallopian tube, or peritoneal cancers between January 2014 and November 2021. We retrospectively analysed the association between the results of Pipelle endometrial biopsy and clinicopathological data. Moreover, we evaluated their impact on the following treatment in advanced cases initially treated with chemotherapy. The sensitivity and false-negative rates for Pipelle endometrial biopsy were 25/90 (27.8%) and 65/90 (72.2%) in all patients, respectively, and 23/56 (41.0%) and 33/56 (58.9%) in cases with advanced disease (stages III and IV), respectively. Pipelle-positive endometrial biopsy-positive (Pipelle-positive) was not observed in 29 patients with clinical stage I disease, and Pipelle-positive patients exhibited significantly more high-grade serous carcinomas, and positive peritoneal, endometrial, and cervical cytologies than Pipelle-endometrial biopsy-negative cases. Surgical pathology was confirmed in 23 Pipelle-positive patients, and 17/23 (74.0%) had the same diagnosis as that for Pipelle endometrial biopsy. Conversely, 6/23 (26.0%) patients exhibited a minor diagnostic discrepancy between Pipelle endometrial biopsy and surgical pathology. Nineteen of the 38 (50.0%) patients initially treated with chemotherapy were identified as Pipelle-positive, contributing to a prompt histological diagnosis and pre-treatment tumour sampling. Companion diagnostic tests were performed using Pipelle endometrial biopsy samples from 4 inoperable patients. Although the positive rate of Pipelle endometrial biopsy in ovarian, fallopian tube, and peritoneal cancers is low, Pipelle endometrial biopsy may enable prompt histological diagnosis and initiation of chemotherapy while collecting tumour tissue for genetic testing in some cases with advanced disease.

Spatial genomic diversity associated with APOBEC mutagenesis in squamous cell carcinoma arising from ovarian teratoma

AbstractAlthough the gross and microscopic features of squamous cell carcinoma arising from ovarian mature cystic teratoma (MCT‐SCC) vary from case to case, the spatial spreading of genomic alterations within the tumor remains unclear. To clarify the spatial genomic diversity in MCT‐SCCs, we performed whole‐exome sequencing by collecting 16 samples from histologically different parts of two MCT‐SCCs. Both cases showed histological diversity within the tumors (case 1: nonkeratinizing and keratinizing SCC and case 2: nonkeratinizing SCC and anaplastic carcinoma) and had different somatic mutation profiles by histological findings. Mutation signature analysis revealed a significantly enriched apolipoprotein B mRNA editing enzyme catalytic subunit (APOBEC) signature at all sites. Intriguingly, the spread of genomic alterations within the tumor and the clonal evolution patterns from nonmalignant epithelium to cancer sites differed between cases. TP53 mutation and copy number alterations were widespread at all sites, including the nonmalignant epithelium, in case 1. Keratinizing and nonkeratinizing SCCs were differentiated by the occurrence of unique somatic mutations from a common ancestral clone. In contrast, the nonmalignant epithelium showed almost no somatic mutations in case 2. TP53 mutation and the copy number alteration similarities were observed only in nonkeratinizing SCC samples. Nonkeratinizing SCC and anaplastic carcinoma shared almost no somatic mutations, suggesting that each locally and independently arose in the MCT. We demonstrated that two MCT‐SCCs with different histologic findings were highly heterogeneous tumors with clearly different clones associated with APOBEC‐mediated mutagenesis, suggesting the importance of evaluating intratumor histological and genetic heterogeneity among multiple sites of MCT‐SCC.

SLFN11 is a BRCA Independent Biomarker for the Response to Platinum-Based Chemotherapy in High-Grade Serous Ovarian Cancer and Clear Cell Ovarian Carcinoma

Abstract BRCA1/2 mutations are robust biomarkers for platinum-based chemotherapy in epithelial ovarian cancers. However, BRCA1/2 mutations in clear cell ovarian carcinoma (CCC) are less frequent compared with high-grade serous ovarian cancer (HGSC). The discovery of biomarkers that can be applied to CCC is an unmet need in chemotherapy. Schlafen 11 (SLFN11) has attracted attention as a novel sensitizer for DNA-damaging agents including platinum. In this study, we investigated the utility of SLFN11 in HGSC and CCC for platinum-based chemotherapy. SLFN11 expression was analyzed retrospectively by IHC across 326 ovarian cancer samples. The clinicopathologic significance of SLFN11 expression was analyzed across 57 advanced HGSC as a discovery set, 96 advanced HGSC as a validation set, and 57 advanced CCC cases, all of whom received platinum-based chemotherapy. BRCA1/2 mutation was analyzed using targeted-gene sequencing. In the HGSC cohort, the SLFN11-positive and BRCA mutation group showed significantly longer whereas the SLFN11-negative and BRCA wild-type group showed significantly shorter progression-free survival and overall survival. Moreover, SLFN11-positive HGSC shrunk significantly better than SLFN11-negative HGSC after neoadjuvant chemotherapy. Comparable results were obtained with CCC but without consideration of BRCA1/2 mutation due to a small population. Multivariate analysis identified SLFN11 as an independent factor for better survival in HGSC and CCC. The SLFN11-dependent sensitivity to platinum and PARP inhibitors were validated with genetically modified non-HGSC ovarian cancer cell lines. Our study reveals that SLFN11 predicts platinum sensitivity in HGSC and CCC independently of BRCA1/2 mutation status, indicating that SLFN11 assessment can guide treatment selection in HGSC and CCC.