RESUMO
Levels of the proinflammatory cytokine interleukin-6 (IL-6) are increased in therapy-resistant prostate cancer. IL-6 has been considered a positive growth factor in late-stage prostate cancer cells and a potential target for therapeutic interference. Effects of inhibition of IL-6 on cell survival were studied in LNCaP-IL6+ cells, a model system for advanced prostate cancer, which produce IL-6. We show that the autocrine IL-6 loop is responsible for resistance to apoptosis and increased cellular levels of myeloid cell leukemia-1 (Mcl-1) protein, an antiapoptotic member of the Bcl-2 family. Treatment of cells with a chimeric anti-IL-6 antibody (CNTO 328) led to the induction of apoptosis and downregulation of Mcl-1 protein levels. Specific knockdown of Mcl-1 gene expression by small interfering RNA also yielded an increase in apoptosis of LNCaP-IL-6+ cells. Vice versa, inactivation of IL-6 autocrine loop had no influence on apoptosis levels in the absence of Mcl-1, thus suggesting this molecule as a mediator of the survival action of IL-6. Mcl-1 protein regulation by the endogenous cytokine directly involved the extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase pathway. Our data support the concept of anti-IL-6 targeted therapy in therapy-resistant prostate cancer.
Assuntos
Apoptose/efeitos dos fármacos , Comunicação Autócrina , Interleucina-6/farmacologia , Proteínas de Neoplasias/fisiologia , Neoplasias da Próstata/patologia , Proteínas Proto-Oncogênicas c-bcl-2/fisiologia , Anticorpos Monoclonais/farmacologia , Apoptose/genética , Progressão da Doença , Flavonoides/farmacologia , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Humanos , Interleucina-6/imunologia , Interleucina-6/metabolismo , Masculino , Proteína Quinase 1 Ativada por Mitógeno/antagonistas & inibidores , Proteína Quinase 3 Ativada por Mitógeno/antagonistas & inibidores , Proteína de Sequência 1 de Leucemia de Células Mieloides , Proteínas de Neoplasias/genética , Neoplasias da Próstata/genética , Neoplasias da Próstata/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2/genética , RNA Interferente Pequeno/farmacologia , Células Tumorais CultivadasRESUMO
PURPOSE: Suppressors of cytokine signalling (SOCS) are induced by interleukins and peptide hormones. These molecules prevent the activation of diverse signalling pathways in benign and malignant cells. In previous studies, we showed that SOCS-3 is expressed in most prostate cancer cell lines and tissue specimens. In the present study we investigated the effects of androgen on the regulation of SOCS-3 in prostate cancer cell lines. MATERIALS AND METHODS: SOCS-3 expression was determined with PCR and Western blot techniques. The activity of the SOCS-3 promoter was measured with the luciferase test. We measured proliferation with (3)H-thymidine assay. RESULTS: We show that androgen induces the expression of SOCS-3 in two prostate cancer cell lines. The non-steroidal anti-androgen bicalutamide is able to block the induction of SOCS-3 -expression. Androgenic hormones did not induce the expression of SOCS-3 mRNA or its promoter activity. In LNCaP-IL-6- cells transfected with the inducible Tet-On construct SOCS-3 expression was induced. The effects of androgenic hormones on the proliferation and induction of PSA were -diminished in the presence of SOCS-3. CONCLUSIONS: Our results show that androgenic -regulation of SOCS-3 leads to inhibition of prolif-eration and secretion in human prostate cancer.