RESUMO
One major clinical problem with prostate cancer is the cells' ability to survive and proliferate upon androgen withdrawal. Because Ca2+ is central to growth control, understanding the mechanisms of Ca2+ homeostasis involved in prostate cancer cell proliferation is imperative for new therapeutic strategies. Here, we show that agonist-mediated stimulation of alpha1-adrenergic receptors (alpha1-AR) promotes proliferation of the primary human prostate cancer epithelial (hPCE) cells by inducing store-independent Ca2+ entry and subsequent activation of nuclear factor of activated T cells (NFAT) transcription factor. Such an agonist-induced Ca2+ entry (ACE) relied mostly on transient receptor potential canonical 6 (TRPC6) channels, whose silencing by antisense hybrid depletion decreased both hPCE cell proliferation and ACE. In contrast, ACE and related growth arrest associated with purinergic receptors (P2Y-R) stimulation involved neither TRPC6 nor NFAT. Our findings show that alpha1-AR signaling requires the coupled activation of TRPC6 channels and NFAT to promote proliferation of hPCE cells and thereby suggest TRPC6 as a novel potential therapeutic target.
Assuntos
Cálcio/metabolismo , Neoplasias da Próstata/metabolismo , Neoplasias da Próstata/patologia , Canais de Potencial de Receptor Transitório/metabolismo , Trifosfato de Adenosina/farmacologia , Agonistas de Receptores Adrenérgicos alfa 1 , Agonistas alfa-Adrenérgicos/farmacologia , Sinalização do Cálcio/fisiologia , Processos de Crescimento Celular/fisiologia , Células Epiteliais/metabolismo , Células Epiteliais/patologia , Humanos , Masculino , NF-kappa B/metabolismo , Fatores de Transcrição NFATC/metabolismo , Fenilefrina/farmacologia , Receptores Purinérgicos/metabolismo , Canais de Cátion TRPC/metabolismo , Canal de Cátion TRPC6 , Regulação para CimaRESUMO
Neuroendocrine differentiation (NED) is a hallmark of advanced androgen-independent prostate cancer, for which no successful therapy exists. NED tumour cells escape apoptotic cell death by alterations of Ca(2+) homeostasis where the store-operated Ca(2+) entry (SOCE) is known to be a key event. We have previously shown that the downregulation of Orai1 protein representing the major molecular component of endogenous SOCE in human prostate cancer cells, and constituting the principal source of Ca(2+) influx used by the cell to trigger apoptosis, contributes to the establishment of an apoptosis-resistant phenotype (Cell Death Dis. 2010 Sep 16;1:e75.). Here, we report for the first time that the decrease of SOCE during NED may be caused by alternative NED-induced mechanism involving cytoskeleton reorganisation. NED induced by androgen deprivation resulted in a decrease of SOCE due to cortical F-actin over-polymerization which inhibits thapsigargin-induced SOCE. The disruption of F-actin polymerization by Cytochalasin D in NED cells restored SOCE, while the induction of F-actin polymerization by jasplakinolide or calyculin A diminished SOCE without changing the expression of key SOCE players: Orai1, STIM1, and TRPC1. Our data suggest that targeting cytoskeleton-induced pathways of malignant cells together with SOCE-involved channels may prove a useful strategy in the treatment of advanced prostate cancer.
Assuntos
Canais de Cálcio/metabolismo , Cálcio/metabolismo , Citoesqueleto/metabolismo , Células Neuroendócrinas/citologia , Actinas/metabolismo , Androgênios/metabolismo , Apoptose , Diferenciação Celular , Linhagem Celular Tumoral , Citocalasina D/farmacologia , Primers do DNA/genética , Eletrofisiologia/métodos , Humanos , Masculino , Toxinas Marinhas , Proteínas de Membrana/metabolismo , Proteínas de Neoplasias/metabolismo , Proteína ORAI1 , Oxazóis/farmacologia , Fenótipo , Neoplasias da Próstata/terapia , Molécula 1 de Interação Estromal , Canais de Cátion TRPC/metabolismoRESUMO
Neuroendocrine differentiation of prostate epithelial cells is usually associated with an increased aggressivity and invasiveness of prostate tumors and a poor prognosis. However, the molecular mechanisms involved in this process remain poorly understood. We have investigated the possible expression of voltage-gated calcium channels in human prostate cancer epithelial LNCaP cells and their modulation during neuroendocrine differentiation. A small proportion of undifferentiated LNCaP cells displayed a voltage-dependent calcium current. This proportion and the calcium current density were significantly increased during neuroendocrine differentiation induced by long-term treatments with cyclic AMP permeant analogs or with a steroid-reduced culture medium. Biophysical and pharmacological properties of this calcium current suggest that it is carried by low-voltage activated T-type calcium channels. Reverse transcriptase-PCR experiments demonstrated that only a single type of LVA calcium channel mRNA, an alpha(1H) calcium channel mRNA, is expressed in LNCaP cells. Quantitative real-time reverse transcriptase-PCR revealed that alpha(1H) mRNA was overexpressed during neuroendocrine differentiation. Finally, we show that this calcium channel promotes basal calcium entry at resting membrane potential and may facilitate neurite lengthening. This voltage-dependent calcium channel could be involved in the stimulation of mitogenic factor secretion and could therefore be a target for future therapeutic strategies.