Aberrant Promoter Hypermethylation of RASSF1a and BRCA1 in Circulating Cell-Free Tumor DNA Serves as a Biomarker of Ovarian Carcinoma.

Sandeep Kumar S,C S Premalatha,V R Pallavi,Ramesh Gawari,Shalini N Swamy

doi:10.31557/apjcp.2019.20.10.3001

Abstract

Objective:Ovarian cancer is one of the leading causes of cancer deaths in women. Ovarian cancer is diagnosed at the late stages and generally relapses within 12-14 months of cytoreductive surgery. This is attributed to lack of precise molecular detection methodologies to detect and track the disease. Epigenetic alteration such as aberrant promoter hypermethylation is an important early event that occurs during cancer development and progression. This study focuses on development of a minimally invasive methylation marker that could be used for detection and prognosis of ovarian cancer patients. Methods:Aberrant promoter hypermethylation of RASSF1a and BRCA1 was assessed in circulating DNA of 72 EOC patients using methylation-specific PCR. The findings were correlated with various clinicopathological parameters. Statistical analysis was done using the Fisher exact test and chi-square test. Results:The aberrant methylation patterns of RASSF1a and BRCA1 was identified to be present in the cancerous samples. A total of 31.9 % and 56.9% methylation was observed for RASSF1a and BRCA1 respectively. A striking 50% methylation of BRCA1 was identified in the benign sample cohort, which marks the significance of assessing the hypermethylation pattern to detect cancer at its early stages. Methylation of the two tumor suppressor genes was evident across various stages and grades of ovarian tumors suggesting that this could also help as a prognostic marker. Conclusion:The results of the current study hold significance since the hypermethylation patterns can be identified in the cell-free circulating tumor DNA from a small volume of blood plasma and is a simple and minimally-invasive method. Assessment of hypermethylation patterns of a panel of TSG along with the existing screening markers could aid in better diagnosis and management of the disease. It could also aid in designing specifically tailored treatment strategies to fight the disease.

Highlights

Ovarian cancer is the third leading gynecological cancer in India and has a very high mortality rate compared to other cancers (Globacon., 2018)
This study focuses on development of a minimally invasive methylation marker that could be used for detection and prognosis of ovarian cancer patients
A striking 50% methylation of Breast cancer susceptibility gene 1 (BRCA1) was identified in the benign sample cohort, which marks the significance of assessing the hypermethylation pattern to detect cancer at its early stages

Summary

Introduction

Ovarian cancer is the third leading gynecological cancer in India and has a very high mortality rate compared to other cancers (Globacon., 2018). Ovarian cancer is mostly asymptomatic at the early stages and the patients do not report with any major clinical symptoms. The high mortality rate of ovarian cancer is attributed to the diagnosis of the disease at stage III or IV, where the cancer would have already metastasized to distant sites. The five-year survival rate of ovarian cancers diagnosed at stage III and IV is about 42% and 26% as against 93% when it is diagnosed at the early stages (Torre et al, 2018). It has not been possible to detect the disease at the early stage. There is an increasing need to develop new and novel detection methodologies to identify the disease at the early stages

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Conclusion