Human Prostatic Carcinoma Oncogene PTI-1 is Expressed in Human Tumor Cell Lines and Prostate Carcinoma Patient Blood Samples

Rapid expression cloning and differential RNA display identifies a gene, named prostate tumor inducing gene-1 (PTI-1), that is differentially expressed in prostate cancer versus normal prostate and benign prostatic hypertrophy. PTI-1 encodes a truncated and mutated human elongation factor 1 alpha, and its 5' untranslated region (UTR) shares significant homology with the 23S rRNA gene of Mycoplasma hyopneumoniae. PCR with human genomic DNAs, using PTI-1 5' UTR-specific primers, suggests that this sequence is part of the human genome. Furthermore, reverse transcription (RT)-PCR, with one primer specific to the 5' UTR region and the other to the elongation factor 1 alpha coding region, amplifies PTI-1 transcripts from total RNA of various human tumor cell lines and blood samples from prostate carcinoma patients. RT-PCR products with the predicted size and sequence of PTI-1 are detected in RNAs from cell lines of human prostate, breast, and colon carcinomas. This RT-PCR product is shown by Southern blotting and sequence analyses to contain the junction sequence between the 5' UTR and the coding region of the PTI-1 gene. Furthermore, RT-PCR analysis indicates that the PTI-1 gene is also expressed in prostate carcinoma patient-derived blood samples. On the basis of serial dilution experiments, PTI-1 can detect 1 prostate carcinoma cell in 10(8) cells not expressing PTI-1. In this context, PTI-1 represents a sensitive marker for detecting human prostate cancer in the bloodstream. This study confirms the authenticity of the PTI-1 gene and documents its potential clinical utility as a sensitive and specific indicator of prostate cancer progression.