ABSTRACT
Gain at chromosome 3q25-q26 has been reported to commonly occur in prostate cancer. To map the 3q25-q26 amplification unit and to identify the candidate genes of amplification, we did fluorescence in situ hybridization and quantitative real-time PCR for gene copy number and mRNA expression measurements in prostate cancer cell lines and prostate cancer samples from radical prostatectomy specimens. The minimal overlapping region of DNA copy number gains in the cell lines could be narrowed down to 700 kb at 3q26.2. Of all positional and functional candidates in this region, the gene TLOC1/SEC62 revealed the highest frequency (50%) of copy number gains in the prostate cancer samples and was found to be up-regulated at the mRNA level in all samples analyzed. TLOC1/Sec62 protein was also shown to be overexpressed by Western blot analysis. Intriguingly, the TLOC1/SEC62 gene copy number was increased in prostate tumors from patients who had a lower risk of and a longer time to progression following radical prostatectomy. These findings make TLOC1/SEC62 the best candidate within the 3q amplification unit in prostate cancer. TLOC1/Sec62 protein is a component of the endoplasmic reticulum protein translocation machinery, whose function during prostate carcinogenesis remains to be determined.
Subject(s)
Chromosomes, Human, Pair 3/genetics , Gene Amplification , Gene Dosage , Membrane Transport Proteins/genetics , Prostatic Neoplasms/genetics , Cell Line, Tumor , Chromosome Mapping , Genomics , Humans , In Situ Hybridization, Fluorescence , Male , Membrane Transport Proteins/analysis , Membrane Transport Proteins/metabolism , Prostatic Neoplasms/chemistry , Prostatic Neoplasms/metabolism , RNA, Messenger/analysis , RNA, Messenger/metabolism , Up-RegulationABSTRACT
OBJECTIVE: High stage prostate cancers have been reported to frequently harbor chromosome 8 alterations and hypomethylation of LINE-1 retrotransposons. The potential of these parameters for molecular staging of prostate carcinoma was investigated. METHODS: High molecular weight DNA was extracted from 63 carcinoma tissues (22 pT2, 38 pT3, 3 pT4). Chromosome 8 alterations were followed by determining the ratio of NKX3.1 (at 8p21) to MYC (at 8q24) gene copy numbers (NKX3.1:MYC ratio) using a new real-time PCR technique. LINE-1 hypomethylation was quantified by Southern blot analysis. RESULTS: In 42 carcinomas NKX3.1 copy numbers were altered, with decreases in 32 cases. Copy numbers of MYC were increased in 38 cases and diminished in four. The NKX3.1:MYC ratio was altered in 45 specimens, with a decrease in all but two. NKX3.1 loss was associated with tumor stage (p<0.03) and MYC gain with Gleason score (p<0.03). The NKX3.1:MYC ratio was highly significantly associated with tumor stage (p<0.002), displaying 66% sensitivity and 87% specificity. LINE-1 hypomethylation was related (p<0.004) to tumor stage, but exhibited lower sensitivity (59%) and specificity (77%). CONCLUSION: A straightforward PCR technique detecting chromosome 8 alterations might be useful to predict which prostate cancers are organ-confined while determination of hypomethylation appears to be somewhat less well suited.
