Circulating cell-free DNA: A novel biomarker for response to therapy in ovarian carcinoma

Abstract

Introduction: Cell-free DNA (CFDNA) is a reflection of both normal and tumor-derived DNA released into the circulation through cellular necrosis and apoptosis. We sought to determine whether tumor-specific plasma DNA could be used as a biomarker for tumor burden and response to therapy in an orthotopic ovarian cancer model.Methods: Female nude mice injected intraperitoneally with HeyA8 ovarian cancer cells were treated with either docetaxel alone or in combination with anti-angiogenic agents (AEE788-dual VEGFR and EGFR antagonist or EA5-monoclonal antibody against ephrin A2). Following DNA extraction from plasma, quantification of tumor-specific DNA was performed by real-time PCR using human specific beta-actin primers. The number of genome equivalents (GE/ml) were determined from a standard curve. Apoptosis was assessed by TUNEL staining of treated tumors.Results: The levels of tumor-specific DNA in plasma increased progressively with increasing tumor burden (R 2 = 0.8, p < 0.01). Additionally, tumor-specific plasma DNA levels varied following treatment with chemotherapy. In mice with established tumors (19 days following tumor injection), tumor-specific plasma DNA levels increased by 63% at 24 hours following a single dose of docetaxel (15mg/kg), and then declined to 20% below baseline at 72 hours and were 83% lower than baseline 10 days following therapy. In addition, docetaxel treatment resulted in a significant increase in the apoptotic index at 24 hours (p < 0.01). Moreover, in two separate therapy experiments using a combination of cytotoxic chemotherapy with anti-angiogenic agents, tumor-specific plasma DNA levels were significantly higher in mice treated with vehicle compared to the treatment groups. The correlation between tumor weight and tumor-specific DNA in these experiments was 0.71-0.76 (p < 0.01).Conclusions: Our results indicate that tumor-specific CFDNA levels correlate with increasing tumor burden and decline following therapy. Thus, tumor-specific DNA may be a useful surrogate biomarker of therapeutic response and should be evaluated in future clinical trials.

Plasma DNA level in predicting therapeutic efficacy in advanced nonsmall cell lung cancer

“…This suggests that the increased presence of cfDNA in the plasma of lung cancer patients might be due to apoptosis, necrosis, tumour cell lysis or the excessive turnover rate of tumour cells. Further, findings in mice bearing human tumours and undergoing chemotherapy or surgery suggested that cfDNA can be used for monitoring the effect of therapy [16,17]. In mice bearing human tumours, a marked transient rise in the levels of human-specific cfDNA (tumour-specific DNA) occurred immediately after chemotherapy or surgery, followed by a rapid decrease [16,17].…”

Differential Methylation Profile of Ovarian Cancer in Tissues and Plasma

“…Such DNA is present in blood of ovarian cancer patients, 11 so we have analyzed cell-free circulating DNA from ovarian cancer patients and healthy gender-and age-matched controls with the MethDet test. To exclude treatmentrelated changes in methylation, plasma samples have been obtained either before or during surgery and before initiation of therapy.…”

“…10 The paradigm involves combinations of blood-based markers as the first line followed by confirmatory transvaginal ultrasonography. 4 Among other analytes, DNA has certain advantages-it is a relatively stable molecule that can be amplified in polymerase chain reaction providing high analytical sensitivity; it can be recovered from the blood (eg, 11 ) and can be used as a biomarker either directly 11 or as a substrate for genetic testing. It can also be used to test for abnormal DNA methylation, which has been found in ovarian tumors.…”

Liquid biopsy in ovarian cancer: recent advances on circulating tumor cells and circulating tumor DNA

“…Ten years ago, Kamat et al [71] proposed the potential use of tumor-specific cfDNA levels in predicting tumor response to chemotherapy, by using an orthotopic mouse model. Capizzi et al further investigated the predictive value of cfDNA in ovarian cancer patients.…”