Received on April 9, 2008
Accepted on December 17, 2008

Molecular Diagnostics and Genetics

Multimarker Circulating DNA Assay for Assessing Blood of Prostate Cancer Patients

¹ Department of Molecular Oncology, John Wayne Cancer Institute, Saint John's Health Center, Santa Monica, CA
² Department of Medicine, Division of Oncology, University of Washington and Seattle Cancer Care Alliance, Seattle, WA
³ Department of Radiation Oncology, Saint John's Health Center, Santa Monica, CA
⁴ The Angeles Clinic and Research Institute, Santa Monica, CA
⁵ Singapore Clinic
⁶ Breast and Endocrine Program, John Wayne Cancer Institute, Saint John's Health Center, Santa Monica, CA

^* To whom correspondence should be addressed. E-mail: hoon{at}jwci.org.

BACKGROUND: Prostate cancer (PCa) detection using serum-based prostate specific antigen (PSA) is limited by frequent false-positive and -negative results. Genetic aberrations such as allelic imbalance (AI) and epigenetic changes such as promoter hypermethylation have been detected in circulating DNA of cancer patients. We hypothesized that circulating multimarker DNA assays detecting both genetic and epigenetic markers in serum would be useful in assessing PCa patients.

METHODS: We assayed blood from healthy male donors (n = 40) and 83 patients with American Joint Cancer Committee (AJCC) stage I–IV PCa. DNA was assayed for AI of 6 genome microsatellites. We assessed methylation of RASSF1, RARB2, and GSTP1 using a methylation-specific PCR assay and analyzed the sensitivity of each assay for the detection of genetic or epigenetic changes in circulating DNA. We investigated the relation between circulating tumor-related DNA detection and prognostic factors.

RESULTS: The proportion of patients demonstrating AI for 1 marker was 47% (38 of 81 patients). Methylation biomarkers were detected in 24 of 83 patients (28%). By combining 2 DNA assays, the number of PCa patients positive for 1 methylated or LOH marker increased (52 of 83; 63%). The combined assays detected PCa in 15 of 24 patients (63%) with normal PSA concentrations. The combination of the DNA assays detected the presence of PCa regardless of AJCC stage or PSA concentration. Combination of the DNA and PSA assays gave 89% sensitivity.

CONCLUSIONS: This pilot study demonstrates that the combined circulating DNA multimarker assay identifies patients with PCa and may yield information independent of AJCC stage or PSA concentration.