Association of somatic mutations in BRCA2 BRC domain with chemotherapy sensitivity and survival in high grade serous ovarian cancer

Effective sequential combined therapy with carboplatin and a CDC7 inhibitor in ovarian cancer

BACKGROUND

The enhancement of DNA damage repair is one of the important mechanisms of platinum resistance. Protein cell division cycle 7 (CDC7) is a conserved serine/threonine kinase that plays important roles in the initiation of DNA replication and is associated with chemotherapy resistance in ovarian cancer. However, whether the CDC7 inhibitor XL413 has antitumor activity against ovarian cancer and its relationship with chemosensitivity remain poorly elucidated.

METHODS

We evaluated the antitumor effects of carboplatin combined with XL413 for ovarian cancer in vitro and in vivo. Cell viability inhibition, colony formation and apoptosis were assessed. The molecules related to DNA repair and damage were investigated. The antitumor effects of carboplatin combined with XL413 were also evaluated in SKOV-3 and OVCAR-3 xenografts in subcutaneous and intraperitoneal tumor models.

RESULTS

Sequential administration of XL413 after carboplatin (CBP) prevented cellular proliferation and promoted apoptosis in ovarian cancer (OC) cells. Compared with the CBP group, the expression level of RAD51 was significantly decreased and the expression level of γH2AX was significantly increased in the sequential combination treatment group. The equential combination treatment could significantly inhibit tumor growth in the subcutaneous and intraperitoneal tumor models, with the expression of RAD51 and Ki67 significantly decreased and the expression of γH2AX increased.

CONCLUSIONS

Sequential administration of CDC7 inhibitor XL413 after carboplatin can enhance the chemotherapeutic effect of carboplatin on ovarian cancer cells. The mechanism may be that CDC7 inhibitor XL413 increases the accumulation of chemotherapy-induced DNA damage by inhibiting homologous recombination repair activity.

BRCA2 C-Terminal RAD51-Binding Domain Confers Resistance to DNA-Damaging Agents

Breast cancer type 2 susceptibility (BRCA2) protein is crucial for initiating DNA damage repair after chemotherapy with DNA interstrand crosslinking agents or X-ray irradiation, which induces DNA double-strand breaks. BRCA2 contains a C-terminal RAD51-binding domain (CTRBD) that interacts with RAD51 oligomer-containing nucleofilaments. In this study, we investigated CTRBD expression in cells exposed to X-ray irradiation and mitomycin C treatment. Surprisingly, BRCA2 CTRBD expression in HeLa cells increased their resistance to X-ray irradiation and mitomycin C. Under endogenous BRCA2 depletion using shRNA, the sensitivities of the BRCA2-depleted cells with and without the CTRBD did not significantly differ. Thus, the resistance to X-ray irradiation conferred by an exogenous CTRBD required endogenous BRCA2 expression. BRCA2 CTRBD-expressing cells demonstrated effective RAD51 foci formation and increased homologous recombination efficiency, but not nonhomologous end-joining efficiency. To the best of our knowledge, our study is the first to report the ability of the BRCA2 functional domain to confer resistance to X-ray irradiation and mitomycin C treatment by increased homologous recombination efficiency. Thus, this peptide may be useful for protecting cells against X-ray irradiation or chemotherapeutic agents.

Predicting Response to Anthracyclines in Ovarian Cancer

(1) Background: Anthracyclines are intriguing drugs, representing one of the cornerstones of both first and subsequent-lines of chemotherapy in ovarian cancer (OC). Their efficacy and mechanisms of action are related to the hot topics of OC clinical research, such as BRCA status and immunotherapy. Prediction of response to anthracyclines is challenging and no markers can predict certain therapeutic success. The current narrative review provides a summary of the clinical and biological mechanisms involved in the response to anthracyclines. (2) Methods: A MEDLINE search of the literature was performed, focusing on papers published in the last two decades. (3) Results and Conclusions: BRCA mutated tumors seem to show a higher response to anthracyclines compared to sporadic tumors and the severity of hand–foot syndrome and mucositis may be a predictive marker of PLD efficacy. CA125 can be a misleading marker of clinical response during treatment with anthracyclines, the response of which also appears to depend on OC histology. Immunochemistry, in particular HER-2 expression, could be of some help in predicting the response to such drugs, and high levels of mutated p53 appear after exposure to anthracyclines and impair their antitumor effect. Finally, organoids from OC are promising for drug testing and prediction of response to chemotherapy.

Clinical significance of metabolism-related genes and FAK activity in ovarian high-grade serous carcinoma

BACKGROUND

Administration of poly (ADP-ribose) polymerase (PARP) inhibitors after achieving a response to platinum-containing drugs significantly prolonged relapse-free survival compared to placebo administration. PARP inhibitors have been used in clinical practice. However, patients with platinum-resistant relapsed ovarian cancer still have a poor prognosis and there is an unmet need. The purpose of this study was to examine the clinical significance of metabolic genes and focal adhesion kinase (FAK) activity in advanced ovarian high-grade serous carcinoma (HGSC).

METHODS

The RNA sequencing (RNA-seq) data and clinical data of HGSC patients were obtained from the Genomic Data Commons (GDC) Data Portal and analysed ( https://portal.gdc.cancer.gov/ ). In addition, tumour tissue was sampled by laparotomy or screening laparoscopy prior to treatment initiation from patients diagnosed with stage IIIC ovarian cancer (International Federation of Gynecology and Obstetrics (FIGO) classification, 2014) at the Saitama Medical University International Medical Center, and among the patients diagnosed with HGSC, 16 cases of available cryopreserved specimens were included in this study. The present study was reviewed and approved by the Institutional Review Board of Saitama Medical University International Medical Center (Saitama, Japan). Among the 6307 variable genes detected in both The Cancer Genome Atlas-Ovarian (TCGA-OV) data and clinical specimen data, 35 genes related to metabolism and FAK activity were applied. RNA-seq data were analysed using the Subio Platform (Subio Inc, Japan). JMP 15 (SAS, USA) was used for statistical analysis and various types of machine learning. The Kaplan-Meier method was used for survival analysis, and the Wilcoxon test was used to analyse significant differences. P < 0.05 was considered significant.

RESULTS

In the TCGA-OV data, patients with stage IIIC with a residual tumour diameter of 1-10 mm were selected for K means clustering and classified into groups with significant prognostic correlations (p = 0.0444). These groups were significantly associated with platinum sensitivity/resistance in clinical cases (χ2 test, p = 0.0408) and showed significant relationships with progression-free survival (p = 0.0307).

CONCLUSION

In the TCGA-OV data, 2 groups classified by clustering focusing on metabolism-related genes and FAK activity were shown to be associated with platinum resistance and a poor prognosis.