Detection of TP53 mutations in plasma of ovarian cancer and breast cancer patients

Abstract

Background. The analysis of circulating tumor DNA provides wide opportunities for monitoring the results of cancer treatment. Somatic mutations in TP53 gene are present in almost all breast carcinomas developing in hereditary BRCA1 mutation carriers, as well as in the majority of high-grade serous ovarian tumors, which makes it possible to use them for effective monitoring of these diseases.
 The aim of the study was to analyze the content of tumor-specific TP53 mutations in plasma of patients with high-grade serous ovarian cancer (OC) and BRCA1-associated breast cancer (BC).
 Materials and methods. At least one plasma sample was obtained from 10 patients with OC and 7 patients with BRCA1-associated BC. The primary intratumoral status of TP53 gene was determined in the archival tumor material by targeted next generation sequencing. Digital droplet PCR was applied for testing of plasma samples for the presence of tumor-specific TP53 mutations, and in one case, BRAF V600E mutation.
 Results. All 8 plasma samples obtained from OC patients at the time of disease progression, before or during neoadjuvant chemotherapy, were positive for TP53 mutations. In contrast, 8 OC plasma samples obtained during remission, after surgery, or after neoadjuvant chemotherapy did not contain tumor-specific mutations. In breast cancer, circulating tumor DNA was detected in 2 of 4 samples obtained before treatment, and was not detected after the end of therapy or in remission.
 Conclusion. There is a good correlation between the presence of tumor-specific TP53 mutations in circulating DNA and the disease status in OC patients, therefore TP53 is a promising marker for clinical monitoring of ovarian cancer. In breast cancer, circulating tumor DNA is less abundant, therefore TP53 mutations cannot be reliably detected by digital droplet PCR in the plasma of patients with moderate disease burden.