Developmental and Hormonal Regulation of Transforming Growth Factor-α and Epidermal Growth Factor Receptor Gene Expression in Isolated Prostatic Epithelial and Stromal Cells

Naoki Itoh; Urvashi Patel; Michael K. Skinner

doi:10.1210/endo.139.3.5821

Androgen has an important role in development of the prostate, and the actions of androgen are mediated, in part, by locally produced growth factors. These growth factors are postulated to mediate stromal-epithelial interaction in the prostate to maintain normal tissue physiology. Transforming growth factor-α (TGF-α) is one of the growth factors that can stimulate prostatic growth. The expression of TGF-α is thought to be regulated by androgen. The expression of epidermal growth factor receptor (EGFR), which is the receptor of TGF-α and EGF, also may be regulated by androgen. The hormonal and developmental regulation of TGF-α and EGFR messenger RNA (mRNA) levels in isolated epithelial and stromal cells from rat ventral prostate was investigated. The expression of mRNA for TGF-α and EGFR was analyzed by a quantitative RT-PCR (QRT-PCR) procedure developed. Observations from this assay demonstrated that both epithelial and stromal cells expressed the mRNA for TGF-α and EGFR. TGF-α mRNA expression was constant during postnatal, pubertal, and adult development of the prostate. EGFR mRNA expression was elevated at the midpubertal period and decreased with age. After castration of 60-day-old adult rats, both TGF-α and EGFR mRNA were significantly enhanced. TGF-α mRNA expression was stimulated by EGF in stromal cells (4.5-fold increase) but was not changed by any treatment in epithelial cells. EGFR mRNA levels were stimulated by EGF and keratinocyte growth factor treatment and inhibited by testosterone treatment in epithelial cells. Stromal cell EGFR mRNA levels were not affected by any treatment. Both testosterone and EGF stimulated incorporation of 3H-thymidine into prostatic stromal and epithelial cells. Anti-TGF-α antibody significantly inhibited testosterone-stimulated 3H-thymidine incorporation into stromal cells and epithelial cells. Immunocytochemical localization of TGF-α and EGFR demonstrated expression on the luminal surface of epithelial cells within prostatic ducts, and minimal expression was observed in stromal cells. Results indicate that testosterone does not directly regulate TGF-α mRNA levels but does inhibit EGFR mRNA levels. Interestingly, anti TGF-α antibody suppressed the effect of testosterone on 3H-thymidine incorporation into prostatic stromal and epithelial cells. This finding suggests that testosterone may act indirectly on prostatic cells to influence TGF-α actions. TGF-α mRNA levels were influenced by EGF in stromal cells only, and EGFR mRNA levels were influenced by testosterone, EGF, and keratinocyte growth factor in epithelial cells. These observations suggest that regulation of TGF-α and EGFR is distinct between the cell types. In conclusion, a network of hormonally controlled growth factor-mediated stromal-epithelial interactions is needed to maintain prostate development and function.

Developmental and Hormonal Regulation of Transforming Growth Factor-α and Epidermal Growth Factor Receptor Gene Expression in Isolated Prostatic Epithelial and Stromal Cells

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