Microsatellite analysis of allelic imbalance in tumour and blood from patients with prostate cancer.

OBJECTIVE: To investigate whether a high frequency of allelic imbalance (AI) is associated with clinicopathological variables of patients with prostate cancer. PATIENTS AND METHODS: We analysed loss of heterozygosity (LOH) and microsatellite (MS) instability (MSI) on circulating plasma DNA in a polymerase chain reaction (PCR)-based MS study of 230 patients with prostate cancer and 43 with benign prostatic hyperplasia (BPH) using a panel of 13 polymorphic MS markers. RESULTS: The overall incidence of AI was significantly higher in primary tumours (34%) than in blood plasma samples from patients with prostate cancer (11%). Although LOH (2.0%) and MSI (1.5%) were also found in BPH plasma samples, their frequencies were low. AI identified in plasma samples from patients with prostate cancer could be retrieved in 63% of the paired tumour samples. The highest concordance of AI and retention of heterozygosity between tumour and plasma samples was 83% at the marker D8S360. There were high frequencies of LOH at the markers THRB, D7S522 and D8S137 in both types of specimens. The markers D11S898 and D11S1313 on the chromosome arm 11q showed frequent MSI. The comparison with established risk factors showed significant associations of an increase in prostate volume with AI at the combined markers D6S474/D7S522 in tumour tissues and at D7S522 in plasma samples (P < 0.04). In the primary tumours there was a further correlation of LOH at D11S1313 with increasing tPSA value (P = 0.005). The combination of total prostate-specific antigen (PSA) and % free PSA was associated with LOH at THRB in plasma samples. CONCLUSIONS: Plasma-based MS analysis may have clinical value for the molecular staging of prostate cancer.

Comparison of genetic alterations detected in circulating microsatellite DNA in blood plasma samples of patients with prostate cancer and benign prostatic hyperplasia.

Prostate cancer is the most frequent malignant disease and the second most frequent cause of death due to cancer in men in the Western world. Since serum prostate-specific antigen (PSA) and its subforms show poor specificity in clinical practice, a molecular marker for the detection and discrimination of prostate cancer (PCa) could be of great interest. To investigate the potential significance of genetic aberrations, such as loss of heterozygosity (LOH), in PCa we identified and characterized allelic losses in circulating tumor-associated DNA in blood from patients with localized PCa. Genomic DNA extracted from cell-free plasma of blood samples drawn from 65 PCa patients was analyzed using a panel of 15 polymorphic microsatellite markers mapping to known tumor-suppressor genes. Comparative analyses were performed with a control group of 36 patients with benign prostatic hyperplasia (BPH). In the current study, we demonstrate that PCa patients had higher DNA concentrations in their blood circulation than BPH patients. In the marker panel studied, LOH was more frequently detected in PCa patients (34%) than in BPH patients (22%). The incidence of LOH in the plasma DNA of PCa patients was highest at chromosomal regions 3p24 (THRB, 22%) and 8p21 (D8S360, 22%) in comparison to the BPH control cohort, which frequently showed LOH at loci 8q21, 8p21, 9p21, and 11q22 (D8S286, D8S360, D9S1748, and D11S898, each 6%). These results indicate that microsatellite analysis using plasma DNA may be an interesting tool for molecular screening of PCa patients.