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Expression of the prostate-specific membrane antigen
R S Israeli1, C T Powell, J G Corr
1Urologic Oncology Research Laboratory, Memorial Sloan-Kettering Cancer Center, New York, New York 10021.
Abstract:
We have recently cloned a 2.65-kilobase complementary DNA (cDNA) encoding the prostate-specific membrane antigen (PSM) recognized by the 7E11-C5.3 anti-prostate monoclonal antibody. Immunohistochemical analysis of the LNCaP, DU-145, and PC-3 prostate cancer cell lines for PSM expression using the 7E11-C5.3 antibody reveals intense staining in the LNCaP cells with no detectable expression in both the DU-145 and PC-3 cells. Coupled in vitro transcription/translation of the 2.65-kilobase full-length PSM cDNA yields an M(r) 84,000 protein corresponding to the predicted polypeptide molecular weight of PSM. Posttranslational modification of this protein with pancreatic canine microsomes yields the expected M(r) 100,000 PSM antigen. Following transfection of PC-3 cells with the full-length PSM cDNA in a eukaryotic expression vector, we detect expression of the PSM glycoprotein by Western analysis using the 7E11-C5.3 monoclonal antibody. Ribonuclease protection analysis demonstrates that the expression of PSM mRNA is almost entirely prostate specific in human tissues. PSM expression appears to be highest in hormone-deprived states and is hormonally modulated by steroids, with 5-alpha-dihydrotestosterone down-regulating PSM expression in the human prostate cancer cell line LNCaP by 8-10-fold, testosterone down-regulating PSM by 3-4-fold, and corticosteroids showing no significant effect. Normal and malignant prostatic tissues consistently show high PSM expression, whereas we have noted heterogeneous, and at times absent, expression of PSM in benign prostatic hyperplasia. LNCaP tumors implanted and grown both orthotopically and s.c. in nude mice abundantly express PSM, providing an excellent in vivo model system to study the regulation and modulation of PSM expression.
Insights
Researchers cloned the prostate-specific membrane antigen (PSM) gene. PSM is highly expressed in prostate cancer and normal tissues, with expression modulated by hormones.
Area of Science:
- Oncology
- Molecular Biology
- Biochemistry
Background:
- The prostate-specific membrane antigen (PSM) is a target recognized by the 7E11-C5.3 anti-prostate monoclonal antibody.
- Understanding PSM expression is crucial for prostate cancer research and diagnostics.
Purpose of the Study:
- To clone and characterize the complementary DNA (cDNA) encoding PSM.
- To investigate PSM expression in various prostate cancer cell lines and human tissues.
- To explore the hormonal regulation of PSM expression.
Main Methods:
- Complementary DNA (cDNA) cloning and in vitro transcription/translation.
- Immunohistochemical analysis and Western blotting for PSM detection.
- Ribonuclease protection assays for PSM mRNA expression.
- Hormonal modulation studies using steroids in cell lines and xenograft models.
Main Results:
- The full-length PSM cDNA was cloned, encoding an M(r) 84,000 precursor protein that is post-translationally modified to an M(r) 100,000 glycoprotein.
- PSM was intensely expressed in LNCaP cells but not in DU-145 or PC-3 cells; expression was confirmed in transfected PC-3 cells.
- PSM mRNA expression is prostate-specific, with highest levels in hormone-deprived states.
- Steroids, including 5-alpha-dihydrotestosterone and testosterone, significantly down-regulated PSM expression in LNCaP cells.
- Normal and malignant prostatic tissues showed high PSM expression, while benign prostatic hyperplasia exhibited heterogeneous or absent expression.
- LNCaP tumors in nude mice models demonstrated abundant PSM expression.
Conclusions:
- The cloned PSM cDNA provides a tool to study PSM expression and regulation.
- PSM is a prostate-specific antigen with expression modulated by hormones, making it a potential therapeutic and diagnostic target.
- The characterized PSM expression patterns in cell lines and tissues, along with the in vivo model, offer valuable insights for future research.