Ovarian cancer (OC) is the seventh commonest cancer in women, with a global morbidity and mortality rate of 6.6 and 3.9 per 100,000 population respectively, and the incidence has been increasing moderately over the last decade (1, 2). OC usually doesn’t cause noticeable symptoms and there’s no effective screening method; therefore, many patients are not diagnosed until the late stage of the disease, resulting in a relatively high mortality rate (3, 4). Several factors have been associated with the risk of developing OC, e.g., endometriosis, family history, inherited genetic aberrations, etc.; particularly, 39–44% of women who inherited a pathogenic mutation in Breast Cancer 1 (BRCA1) and 11–17% of women with a pathogenic mutation in Breast Cancer 2 (BRCA2) will develop OC by 70–80 years of age (5, 6). BRCA1 and BRCA2, located on 17q21 and 13q13 respectively, are well-established tumor suppressor genes that their protein products are of paramount importance in maintaining the genomic stability and integrity by facilitating error-free homologous recombination repair (HRR) of DNA double strand breaks (DSBs). Multiple studies have revealed that mutations in BRCA1 and BRCA2 are prevalent throughout the whole coding region and the flanking splice sites without any hot spots (7, 8); meanwhile, some mutations have been reported in specific populations with relatively high frequencies as a consequence of founder effect, i.e., the 185delAG in Ashkenazi Jews (9), the 2804delAA in Dutch (10), and E881X in south Africans (11) etc. Khoo et al. first reported the BRCA1:c.1081del as a founder mutation in southern Chinese OC patients in 2002 (12). However, other groups to investigate the prevalence of germline BRCA1/2 mutations (gBRCA1/2^MUT ) in Chinese OC patients revealed different mutations, i.e., BRCA1:c.5470_5477del and c.981_982del etc. (7, 13) Previous dispute, probably caused by different places of origin of the patients, inspired us to identify the BRCA1/2 founder mutations in Henan OC patients; this is because Henan, located in the middle of China with over 100 million population mainly composed of Han Chinese, is the origin of Chinese civilization.

In this study, we identified 28.3% (150/530) of the OC patients in this Henan cohort as gBRCA^MUT carriers, including one with concurrent mutations in both BRCA1 and BRCA2. Haplotype analysis revealed a region of 0.6 MB genomic length spanning BRCA1 highly conserved across all the independent carriers of BRCA1:c.5470_5477del, supporting it as a founder mutation in Henan population. Survival analysis showed the gBRCA^MUT status of the serous OC patients was not associated with their PFS; instead, a nuclear expression of Ki-67% over 50% of the malignant cells appeared to be an independent predictor for a shorter PFS.

Mounting studies have shown that the prevalence of gBRCA^MUT in ovarian cancer patients varies across different populations, ranging from 13.8% in Americans to 40% in Ashkenazi Jews (16–18). A nationwide multi-center study carried out by Wu et al. revealed the prevalence of gBRCA^MUT in Chinese OC patients was 28.5% (7), which is comparable to our result. Interestingly, the top recurrently detected mutations varies between different studies, including the BRCA1:c.1081del, c.964del, c.3770_3771del, c.2371_2372del and c.5470_5477del etc. (12, 19–21); this is probably caused by the different ethnic origins and geographic locations of the included patients. Several studies have reported the BRCA1:c.5470_5477del as the most frequently detected mutation in Chinese OC patients; of note, the patients enrolled in these studies were mainly from northern China (13, 20, 22), and studies on the southern Chinese revealed different top mutations (12, 19, 21). In this study, almost all the patients are from Henan, the central region of China and the origin of Chinese civilization.

Predisposition of gBRCA^MUT is known to promote the early-onset of breast and ovarian cancer (23). In our cohort, this phenomenon is more evident in the gBRCA1^MUT carriers but not the gBRCA2^MUT carriers of serous OC patients (median age: 51 vs 55; p = 0.0055) and to a much less extent in the BRCA^MUT carriers in general as compared to the BRCA^WT patients (median age: 52 vs 54; p = 0.0252). To our surprise, about 6.6% (35/530) of BRCA^WT patients developed the disease before 40, in which only one presents with a clear family history, suggesting other unclarified risk factors contributing to their early disease on-set. In addition, the BRCA^MUT carriers appeared to have the first peak of incidence from 40 to 44 years old, suggesting the BRCA^MUT carriers should carry out preventative screening from 40.

STR analysis supports BRCA1:c.5470_5477del as the founder mutation in our OC cohort, but a validation of this finding in a larger cohort, maybe a nation-wide multi-centered study, could make the conclusion more solid. The conserved region from chr17:42627978 to 43223568 was only partially shared by BRCA1:c.981_982del carriers, which is probably caused by genomic rearrangement or other aberrations that occurred during the course of heredity. Recently, BRCA1:c.5470_5477del was also revealed as a founder mutation in a cohort of 9505 Han breast cancer patients, which made our conclusion more solid (24). Of note, studies carried out in the southern part of China identified different founder mutations, i.e., BRCA1:1081del (12). A non-negligible limitation in all these studies, including this one, could be that only the coding regions of BRCA1/2 and the flanking splice sites were sequenced, which missed the pathogenic aberrations in introns. For example, BRCA1:c.442-22_442-13del has been identified as an ancient founder mutation in the patients from the southern part of China (25).

Currently the first-line therapy against advanced ovarian cancer is maximal cytoreductive surgical debulking followed by chemotherapy with carboplatin–paclitaxel regimen (26). In this study, no difference in PFS was observed if the patients received adjuvant chemotherapy before surgery. Two independent studies showed neoadjuvant chemotherapy followed by surgery was not inferior to surgery followed by chemotherapy and with less postoperative adverse events (27, 28); however, a national cancer database study showed a superior overall survival in patients with primary surgery versus neoadjuvant chemotherapy (29). Surgery first or chemo first? There’s still not a conclusive answer at this point.

The prognosis of BRCA^MUT carriers was shown better than BRCA^WT carriers (30, 31), but we didn’t observe significant PFS benefit in gBRCA^MUT carriers. This result is consistent with a recent study performed by You et al. that the benefit in PFS was only observed when the somatic BRCA^MUT was also included into the analysis (22). Ki-67, a well-established biomarker of cellular proliferation, is frequently used in routine clinical workflow (32). Previous study showed Ki-67 expression was related to the overall survival of OC patients (33); here, our results confirmed that an expression of Ki-67 ≥50% indicated a shorter PFS. The efficiency of Ki-67 expression in predicting the prognostics of OC patients still needs improvement, and this could be addressed as the implication of high throughput sequencing based clinical tests are becoming increasingly prevalent.

In conclusion, our study reveals 28.3% of Henan OC patients are gBRCA^MUT carriers, and BRCA1:c.5470_5477del is a founder mutation in Henan population. A nation-wide large cohort study may help us to understand the founder effect of BRCA mutations in Chinese and design a cost-effective screening test for the high-risk population.

The data presented in the study are deposited in the Genome Sequence Archive repository (https://bigd.big.ac.cn/gsa/), accession number PRJCA004762.

The studies involving human participants were reviewed and approved by the ethics committee of Henan Cancer Hospital. The patients provided their written informed consent to participate in this study.

JL and YG conceived and designed the study. SH and JL analyzed the data and drafted the manuscript with the support from YG and HL. XW and CZ performed NGS test and bioinformatic analysis. YL and LW evaluated the clinical outcome of the patients. JM, BW, YW, and QX analyzed the IHC staining and were responsible for the pathological diagnosis. YG and HL supervised the project. All authors read and approved the submitted manuscript. All authors contributed to the article and approved the submitted version.

This work was financially supported by the funding from Major public welfare projects in Henan Province (grant number: 201300310400) and Henan science and technology project (grant number: 212102310675). JL was also supported by the Henan provincial young researcher program. National Natural Science Foundation of China, 81802779 to JL; Henan Provincial Health Commission, SBGJ202002020 to JL; and Henan Science and Technology Project, 212102310675 to JL.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.