RESUMO
Inhibitors of histone deacetylases have been approved for clinical application in cancer treatment. On the other hand, histone acetyltransferase (HAT) inhibitors have been less extensively investigated for their potential use in cancer therapy. In prostate cancer, the HATs and coactivators p300 and CBP are upregulated and may induce transcription of androgen receptor (AR)-responsive genes, even in the absence or presence of low levels of AR. To discover a potential anticancer effect of p300/CBP inhibition, we used two different approaches: (i) downregulation of p300 and CBP by specific short interfering RNA (siRNA) and (ii) chemical inhibition of the acetyltransferase activity by a newly developed small molecule, C646. Knockdown of p300 by specific siRNA, but surprisingly not of CBP, led to an increase of caspase-dependent apoptosis involving both extrinsic and intrinsic cell death pathways in androgen-dependent and castration-resistant prostate cancer cells. Induction of apoptosis was mediated by several pathways including inhibition of AR function and decrease of the nuclear factor kappa B (NF-κB) subunit p65. Furthermore, cell invasion was decreased upon p300, but not CBP, depletion and was accompanied by lower matrix metalloproteinase (MMP)-2 and MMP-9 transcriptions. Thus, p300 and CBP have differential roles in the processes of survival and invasion of prostate cancer cells. Induction of apoptosis in prostate cancer cells was confirmed by the use of C646. This was substantiated by a decrease of AR function and downregulation of p65 impairing several NF-κB target genes. Taken together, these results suggest that p300 inhibition may be a promising approach for the development of new anticancer therapies.
Assuntos
Proteína de Ligação a CREB/antagonistas & inibidores , Neoplasias da Próstata/metabolismo , Fatores de Transcrição de p300-CBP/antagonistas & inibidores , Androgênios/metabolismo , Apoptose/efeitos dos fármacos , Apoptose/genética , Proteína de Ligação a CREB/genética , Proteína de Ligação a CREB/metabolismo , Proliferação de Células , Sobrevivência Celular/genética , Regulação para Baixo/genética , Inibidores Enzimáticos/farmacologia , Humanos , Masculino , Metaloproteinase 2 da Matriz/metabolismo , Metaloproteinase 9 da Matriz/metabolismo , Invasividade Neoplásica/genética , Neoplasias da Próstata/genética , RNA Interferente Pequeno , Receptores Androgênicos/metabolismo , Transdução de Sinais/efeitos dos fármacos , Fator de Transcrição RelA/metabolismo , Fatores de Transcrição de p300-CBP/genética , Fatores de Transcrição de p300-CBP/metabolismoRESUMO
BACKGROUND: Steroid receptor coactivators p300 and CBP are highly expressed in advanced prostate cancer. They potentiate activation of androgen receptor by androgens and anti-androgens. In the present study, we have addressed the question whether these coactivators enhance activity of estrogen receptor-beta (ER-ß), which is variably expressed in prostate cancers. METHODS: Expression levels of the coactivators p300 and CBP were manipulated by plasmid or siRNA transfections and activity of ER-ß was measured by luciferase assays. Viability was measured by MTT assays and cellular migration was determined by wound-healing and Boyden chamber assays. RESULTS: High expression of ER-ß was found in PC3 cells which were used for the experiments. p300 or CBP enhanced activation of ER-ß by genistein. Antiestrogens did not acquire agonistic properties in the presence of increased concentrations of either coactivator. Inhibition of p300 or CBP decreased genistein stimulation of ER-ß. Genistein reduced migration of PC3 prostate cancer cells and down-regulation of p300 potentiated this effect. CONCLUSIONS: p300 and CBP are implicated in regulation of ER-ß activity and cellular migration in prostate cancer. These findings are important for understanding of action of ER-ß in carcinoma of the prostate.
