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

Cancer Biol Ther. 2006 Oct;5(10):1369-74. doi: 10.4161/cbt.5.10.3240. Epub 2006 Oct 26.


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 (R2=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 (15 mg/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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Antineoplastic Agents / pharmacology
  • Biomarkers, Tumor / analysis
  • Cell-Free System
  • DNA, Neoplasm / analysis*
  • Drug Design
  • Female
  • Humans
  • Mice
  • Mice, Nude
  • Ovarian Neoplasms / drug therapy*
  • Ovarian Neoplasms / genetics*
  • Transplantation, Heterologous


  • Antineoplastic Agents
  • Biomarkers, Tumor
  • DNA, Neoplasm