Cytogenetic and molecular genetic aspects of human prostate cancer: primary and metastatic

Allelic imbalance and biochemical outcome after radical prostatectomy

OBJECTIVE

To compare the incidence of allelic imbalance (AI) in men with rapid disease progression with those who remained disease free after radical prostatectomy, with the aim of identifying genetic markers to predict prognosis and guide further treatment.

PATIENTS AND METHODS

Tumour and normal DNA were extracted from two matched groups of 31 men with extracapsular node-negative (pT3N0) prostate cancer who had undergone radical prostatectomy. One group comprised men who developed biochemical recurrence within 2 years of surgery and one group were prostate-specific antigen (PSA) free for at least 3 years. Men were matched for Gleason grade, preoperative PSA and pathological stage. Analysis was performed by genotyping.

RESULTS

Allelic imbalance was analysed using 30 markers, and was seen in at least one marker in 57 (92%) of the cases. Deletion at marker D10S211 (10p12.1) was significantly more common in the relapse group than the non-relapse group (35 vs 5%, P=0.03).

CONCLUSIONS

This study demonstrates significant association between AI on chromosome 10 and biochemical progression after radical prostatectomy.

Loss of heterozygosity (LOH), malignancy grade and clonality in microdissected prostate cancer

The aim of the present study was to find out whether increasing malignancy of prostate carcinoma correlates with an overall increase of loss of heterozygosity (LOH), and whether LOH typing of microdissected tumour areas can help to distinguish between multifocal or clonal tumour development. In 47 carcinomas analysed at 25 chromosomal loci, the overall LOH rate was found to be significantly lower in grade 1 areas (2.2%) compared with grade 2 (9.4%) and grade 3 areas (8.3%, P = 0.007). A similar tendency was found for the mean fractional allele loss (FAL, 0.043 for grade 1, 0.2 for grade 2 and 0.23 for grade 3, P = 0.0004). Of 20 tumours (65%) with LOH in several microdissected areas, 13 had identical losses at 1-4 loci within two or three areas, suggesting clonal development of these areas. Markers near RB, DCC, BBC1, TP53 and at D13S325 (13q21-22) showed higher loss rates in grades 2 and 3 (between 25% and 44.4%) compared with grade 1 (0-6.6%). Tumour-suppressor genes (TSGs) near these loci might, thus, be important for tumour progression. TP53 mutations were detected in 27%, but BBC1 mutations in only 7%, of samples with LOH. Evaluation of all 25 loci in every tumour made evident that each prostate cancer has its own pattern of allelic losses.

Highly complex chromosomal aberrations in bone marrow of a patient with metastatic prostate neoplasm

Prostate cancer is the single most common malignancy among men in North America. Nevertheless, cytogenetic evaluation of bone marrow in patients with metastatic prostate neoplasm has been rare and, to date, only five such patients have been reported. We report an additional case where chromosomal abnormalities of a bizarre nature were found in the bone marrow. Though cytogenetic findings in prostate cancer are heterogeneously complex, the chromosome regions involved include 1p, 1q, 7q, 8p, 10q, 12p, and 17q and are considered hot spots. What is the significance of these so-called hot spots in metastasis of prostatic cancer to the bone marrow? At present, no meaningful conclusion can be drawn, as data are limited, but accumulation of such cases may provide valuable information concerning the role of chromosomal abnormalities in patients--specifically with metastatic stage--and may help urologists during therapeutic decision making, particularly if a genetic marker for aggressiveness can be determined.