RESUMO
TGF beta can promote and/or suppress prostate tumor growth through multiple and opposing actions. Alterations of its expression, secretion, regulation or of the sensitivity of target cells can lead to a favorable environment for tumor development. To gain a better insight in TGF beta function during cancer progression, we have used different cultured human prostate cells: preneoplastic PNT2 cells, the androgen-dependent LNCaP and the androgen-independent PC3 and DU145 prostate cancer cell lines. We have studied by specific ELISA assays in conditioned media (CM), the secretion of TGF beta 1 and TGF beta 2 in basal conditions and after hormonal treatment (DHT or E2) and the expression of TGF beta 1 mRNA by Northern blot. We have also compared the effect of fibroblast CM on TGF beta secretion by the different cell types. Compared to PNT2 cells, cancer cell lines secrete lower levels of active TGF beta which are not increased in the presence of fibroblast CM. LNCaP cells respond to androgen or estrogen treatment by a 10-fold increase of active TGF beta secretion while PC3 and DU145 are unresponsive. In conclusion, prostate cancer cell lines have lost part of their ability to secrete and activate TGF beta, and to regulate this secretion through stromal-epithelial interactions. Androgen-sensitive cancer cells may compensate this loss by hormonal regulation.
Assuntos
Regulação da Expressão Gênica/efeitos dos fármacos , Neoplasias da Próstata/metabolismo , Fator de Crescimento Transformador beta/genética , Northern Blotting , Meios de Cultivo Condicionados/farmacologia , Di-Hidrotestosterona/farmacologia , Ensaio de Imunoadsorção Enzimática , Estradiol/farmacologia , Fibroblastos/metabolismo , Humanos , Masculino , Neoplasias da Próstata/patologia , RNA Mensageiro/metabolismo , Fator de Crescimento Transformador beta/metabolismo , Fator de Crescimento Transformador beta1 , Fator de Crescimento Transformador beta2 , Células Tumorais CultivadasRESUMO
Inhibition of PRL hormone signaling by suppressor of cytokine signaling (SOCS)/cytokine-inducible SH2-containing protein (CIS) was investigated in transfected HEK 293 cells. We used the physiologically relevant wild-type beta-casein promoter as a target gene for PRL action. We demonstrate that CIS produces a 70% inhibition of PRL signaling by a mechanism distinct from, and downstream of, the effect of SOCS-1 on JAK2. This inhibition involves association with the PRL receptor (PRLR), resulting in the inhibition of signal transducer and activator of transcription 5 (STAT5) activation. Further, we show that SOCS-3 coimmunoprecipitates with the PRLR. These data suggest that SOCS-3 involves a second pathway for the inhibition of PRL signaling other than JAK2 inhibition. Additional results indicate that SOCS-2 can play a more important potentiator role on PRL signaling, resulting in a restoration of 50% of transcriptional inhibition induced by SOCS-3 and a restoration of 100% of transcriptional inhibition induced by CIS. SOCS-2 was able to block the inhibitory effect of SOCS-1. These results indicate that SOCS-2 seems to be an antagonist of the other SOCS. SOCS-1 binds JAK2 and inhibits its phosphorylation; SOCS-3 does not bind JAK2 but binds the PRLR that may mediate its inhibition of JAK2; and finally, CIS binds the PRLR but inhibits signal transducer and activator of transcription 5 rather than JAK2.
Assuntos
Proteínas Imediatamente Precoces/fisiologia , Peptídeos e Proteínas de Sinalização Intracelular , Proteínas do Leite , Prolactina/fisiologia , Proteínas Proto-Oncogênicas , Receptores da Prolactina/metabolismo , Proteínas Repressoras , Transdução de Sinais/fisiologia , Fatores de Transcrição , Proteínas de Transporte/farmacologia , Caseínas/genética , Linhagem Celular , Proteínas de Ligação a DNA/metabolismo , Humanos , Proteínas Imediatamente Precoces/farmacologia , Janus Quinase 2 , Fosforilação/efeitos dos fármacos , Regiões Promotoras Genéticas/efeitos dos fármacos , Proteínas Tirosina Quinases/metabolismo , Proteínas/farmacologia , Fator de Transcrição STAT5 , Proteína 1 Supressora da Sinalização de Citocina , Proteína 3 Supressora da Sinalização de Citocinas , Proteínas Supressoras da Sinalização de Citocina , Transativadores/metabolismo , Tirosina/metabolismoRESUMO
BACKGROUND: Stromal-epithelial interactions play a critical role in prostate development, but the precise mechanisms are still unknown. Transforming growth factor-beta (TGFbeta) could be a potential mediator of these interactions, but there is as yet no clear demonstration of its role. METHODS: Separate cultures and co-cultures of fibroblasts and epithelial human prostate cells were performed. We measured TGFbeta1 and TGFbeta2 secretion by specific ELISA assay, cell growth by DNA assay, and TGFbeta type II receptor expression by RT-PCR. RESULTS: Co-culture resulted in a 20% inhibition of epithelial cell growth, similar to that obtained after TGFbeta treatment (2 ng/ml for 48 hr), but without affecting fibroblast proliferation. This was accompanied by a five- to six-fold increase in epithelial TGFbeta2 secretion. CONCLUSIONS: These results demonstrate for the first time that TGFbeta2 secretion by prostate epithelial cells is under the direct control of a diffusible factor secreted by fibroblasts. They emphasize the role of TGFbeta in stromal-epithelial interactions.