MUS81 Participates in the Progression of Serous Ovarian Cancer Associated With Dysfunctional DNA Repair System

Breast cancer is the primary problem threatening women’s health. The combined application of valproic acid (VPA) and hydroxyurea (HU) has a synergistic effect on killing breast cancer cells, but the molecular mechanism remains elusive. Replication protein A2 phosphorylation (pRPA2), is essential for homologous recombination (HR) repair and cell cycle. Here we showed that in response to HU, the VPA significantly decreased the tumor cells survival, and promoted S-phase slippage, which was associated with the decrease of pCHK1 and WEE1/pCDK1-mediated checkpoint kinases phosphorylation pathway and inhibited pRPA2/Rad51-mediated HR repair pathway; the mutation of pRPA2 significantly diminished the above effect, indicating that VPA-caused HU sensitization was pRPA2 dependent. It was further found that VPA and HU combination treatment also resulted in the decrease of endonuclease MUS81. After MUS81 elimination, not only the level of pRPA2 was abolished in response to HU treatment, but also VPA-caused HU sensitization was significantly down-regulated through pRPA2-mediated checkpoint kinases phosphorylation and HR repair pathways. In addition, the VPA altered the tumor microenvironment and reduced tumor burden by recruiting macrophages to tumor sites; the Kaplan-Meier analysis showed that patients with high pRPA2 expression had significantly worse survival. Overall, our findings demonstrated that VPA influences HR repair and cell cycle through down-regulating MUS81-pRPA2 pathway in response to HU treatment.

Section: Vpa-caused Hu Sensitization Is Associated With Endonuclease Mus81mentioning

confidence: 99%

Valproic Acid Regulates HR and Cell Cycle Through MUS81-pRPA2 Pathway in Response to Hydroxyurea

Lim

Tian

et al. 2021

“…In a study by Pennington et al (28) compared to germline BRCA1/2 mutations, somatic BRCA1/2 mutations had a similar positive impact on overall survival (OS) and platinum responsiveness. On the other hand, in recent reports, homologous recombination deficiency has gained in importance, in addition to the BRCA mutations, on the targeted treatment (23,29), chemotherapy (30,31), and prognosis (32,33) in EOC patients.…”

Section: Introductionmentioning

confidence: 99%

Germline and Somatic BRCA1/2 Mutations in 172 Chinese Women With Epithelial Ovarian Cancer

You

et al. 2020

Objective: Despite several nationwide cohort studies of germline BRCA1/2 mutations and several small cohort studies of somatic BRCA1/2 mutations in Chinese epithelial ovarian cancer (EOC) patients, little is known about the impact of these findings on survival outcomes in this population. In this study of 172 retrospectively recruited Chinese EOC patients, germline and somatic BRCA1/2 mutations and their value for predicting survival outcomes were evaluated. Methods: Unselected patients who visited the study center from January 1, 2011, to January 1, 2015, were recruited and asked to provide peripheral blood samples for this study if they were pathologically confirmed to have primary EOC. All patients received staging surgeries or debulking surgeries involving systemic platinum-based chemotherapy, and the patients were then followed up to December 1, 2017. DNA was extracted from formalin-fixed, paraffin-embedded (FFPE) sections and peripheral blood and sequenced for somatic and germline testing, respectively. The demographic and clinicopathological characteristics of the patients were collected to analyze the distribution of BRCA mutations in subgroups. Survival outcomes were compared among various BRCA mutation statuses using univariate and multivariate models. Results: In 58 (33.7%) patients, 63 variants were identified, including variants of unknown significance (VUS) in 18 patients (10.5%) and pathogenic or likely pathogenic variants in a partially overlapping set of 41 patients (23.8%). Germline BRCA mutations, somatic BRCA mutations, BRCA1 mutations in general, and BRCA2 mutations in general were found in 35 (20.3%), 7 (4.1%), 28 (16.3%), and 13 (7.6%) patients, respectively. Five recurrent mutations were identified. Personal and family cancer histories as well as hereditary breast and ovarian cancer (HBOC) criteria were associated with deleterious BRCA mutations both overall and in the germline specifically, whereas only age at diagnosis of EOC was associated with somatic BRCA mutations. In univariate and Cox regression analyses, patients with BRCA1/2 mutations in general had significant improvements in progression-free survival (PFS) and overall survival (OS). You et al. Germline and Somatic BRCA1/2 Mutations in EOC Conclusions: In Chinese EOC patients, the distributions and risk factors associated with germline and somatic BRCA1/2 mutations were similar to those previously reported in international studies. Deleterious BRCA mutations in general were associated with improved survival outcomes in this cohort.

“…It acts as a DNA replication pressure sensor, regulating the DNA replication forks reactivation, further affecting important DNA damage repair pathways, such as cell non-homologous end joining and homologous recombination repair (HR) ( 6 , 7 ). Inhibition of MUS81 expression in ovarian cancer, significantly impairs cell HR activity ( 8 , 9 ). Our previous research showed that MUS81 was overexpressed in gastric cancer cells and might promote gastric cancer cell invasion and metastasis ( 10 ).…”

Section: Introductionmentioning

confidence: 99%

MUS81 Inhibition Enhances the Anticancer Efficacy of Talazoparib by Impairing ATR/CHK1 Signaling Pathway in Gastric Cancer

Wang

Zhang

et al. 2022

MUS81 is a critical endonuclease involved in heterodimer formation with Eme1/Mms4 and an important DNA damage repair regulatory molecule. Our previous study suggested that MUS81 was overexpressed and its high expression was positively correlated with gastric cancer metastasis. However, the therapeutic potential of targeting MUS81 in gastric cancer requires further exploration. Therefore, in this study, the Cancer Genome Atlas (TCGA) data were analyzed and showed that MUS81 is a key regulator of cell cycle distribution and DNA damage repair in gastric cancer. In vitro and in vivo, MUS81 knockdown significantly enhanced the anticancer effect of the PARP inhibitor talazoparib. Mechanistically, MUS81 inhibition impaired the activation of the ATR/CHK1 cell cycle signaling pathway and promoted gastric cancer cells with talazoparib-induced DNA damage to continue mitosis. Moreover, addition of the bromodomain-containing protein 4 inhibitor AZD5153 increased the anticancer effect of talazoparib via MUS81 inhibition in gastric cancer cells, and this combination effect was largely impaired when MUS81 was knocked down. In conclusion, these data suggested that MUS81 regulated ATR/CHK1 activation, a key signaling pathway in the G2M checkpoint, and targeting MUS81 enhanced the antitumor efficacy of talazoparib. Therefore, AZD5153 combined with talazoparib may represent a promising therapeutic strategy for patients with MUS81 proficient gastric cancer.