Hsiang-Lin Chang

Involvement of breast epithelial-stromal interactions in the regulation of protein tyrosine phosphatase-γ (PTPγ) mRNA expression by estrogenically active agents

AbstractBackground. Protein tyrosine phosphatase γ (PTPγ) has been implicated as a tumor suppressor gene in kidney and lung cancers. Our previous results indicate that estradiol-17β (E2)-induced suppression of PTPγ may play a role in mammary tumorigenesis. Zeranol (Z), a nonsteroidal growth promoter with estrogenic activity that is used by the US meat industry, induces estrogenic responses in primary cultured breast cells and breast cancer cell lines. Methods. PTPγ mRNA expression in human breast tissues and cells isolated from surgical specimens of mammoplasty and breast cancer patients were detected and quantified by RT-PCR. Immunohistochemical staining was used to localize PTPγ in human breast tissues. Breast epithelial and stromal cells were isolated and co-cultured to determine the involvement of cell–cell interaction in the regulation of PTPγ mRNA expression by E2 and Z. Results. PTPγ mRNA expression was lower in cancerous than in normal breast tissues. Both E2 and Z suppressed PTPγ mRNA levels in cultured normal breast tissues by ∼80%, but had a lesser effect in cultured epithelial cells isolated from normal breast tissues. In the co-culture system, both E2 and Z suppressed PTPγ mRNA to a greater degree in epithelial cells than in stromal cells. In whole breast tissues, PTPγ was immunolocalized to the epithelium. Treatment with E2 or Z diminished PTPγ staining indicating reductions in PTPγ at the protein level. Conclusions. The results indicate that both E2 and Z regulate PTPγ expression in human breast and that epithelial–stromal cells interaction is important in the regulation of PTPγ expression by estrogenically active agents.

Effect of keratinocyte growth factor on cell viability in primary cultured human prostate cancer stromal cells

In normal prostate, keratinocyte growth factor (KGF), also known as fibroblast growth factor-7 (FGF-7) serves as a paracrine growth factor synthesized in stromal cells that acts on epithelial cells through its receptor, KGFR. KGF and KGFR were found in human cancer epithelial cells as well as stromal cells. Since KGF expressed in epithelial cells of benign prostatic hyperplasia (BPH) and in prostate cancer, it has been suggested that KGF might act as an autocrine factor in BPH and prostate cancer. To investigate the roles of KGF in cancerous stroma, primary cultured human prostate cancer stromal cells (PCSCs) were isolated and evaluated. These PCSCs possessed estrogen receptors and KGFR, but not androgen receptor as determined by RT-PCR and Western blot, respectively. KGF exhibited mitogenic and anti-apoptotic effects that correlated with induction of cyclin-D1, Bcl-2, Bcl-xL and phospho-Akt expression in PCSCs, where treatment with KGF antiserum abolished cell proliferation and anti-apoptotic protein expression. PCSCs exposed to KGF for various time periods resulted in phosphorylation of Akt and subsequent up-regulation of Bcl-2. KGF modulated dynamic protein expression indicated that KGF triggered cell cycle machinery and then activated anti-apoptotic actions in PCSCs. Cell proliferation analysis indicated that tamoxifen or ICI 182,780 reduced cell viability in a dose-dependent manner; however, KGF prevented this inhibition, which further demonstrated KGF triggered anti-apoptotic machinery through activating Bcl-2 and phospho-Akt expression. In summary, KGF has an autocrine effect and serves as a survival factor in primary cultured human prostate cancer stromal cells.