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Pituitary-like proopiomelanocortin transcripts in human Leydig cell tumors
Y de Keyzer1, F Lenne, J F Massias
1Centre de Recherche sur les Maladies Endocriniennes, Hôpital Cochin, Paris, France.
The Journal of Clinical Investigation
|September 1, 1990
Summary
Proopiomelanocortin (POMP) gene expression in human Leydig cell tumors can produce a full-length precursor molecule, unlike normal testicular tissue. This leads to significantly increased POMP peptide levels and ACTH production in some tumors.
Area of Science:
- Molecular endocrinology
- Oncology
- Gene expression
Background:
- Proopiomelanocortin (POMP) is a precursor protein processed into various peptides, including ACTH.
- Anterior pituitary corticotrophs are the primary site of POMP gene expression and ACTH production.
- POMP gene expression also occurs in nonpituitary tissues like the testis, typically producing shorter transcripts.
Purpose of the Study:
- To investigate the mode of POMP gene expression in human Leydig cell tumors.
- To determine if Leydig cell tumors produce full-length POMP mRNA and peptides.
- To understand the implications for ectopic hormone secretion.
Main Methods:
- Analysis of POMP mRNA species in human Leydig cell tumors.
- Comparison of POMP gene expression between tumors and normal/peritumoral testicular tissue.
- Quantification of POMP peptide concentrations.
Main Results:
- Human Leydig cell tumors can express a 1,200-nucleotide POMP mRNA, identical to pituitary transcripts.
- This full-length mRNA allows for the production of complete POMP molecules.
- Two out of six tumors showed a ~1,000-fold increase in POMP peptide concentrations, including ACTH.
Conclusions:
- Leydig cell tumors can exhibit altered POMP gene expression, producing full-length POMP.
- This aberrant expression leads to significantly elevated POMP peptides and ACTH.
- Findings offer insights into POMP expression in nonpituitary tumors and ectopic hormone secretion.