RESUMO
In the early stages, prostate cancer is androgen dependent; therefore, medical castration has shown significant results during the initial stages of this pathology. Despite this early effect, advanced prostate cancer is resilient to such treatment. Recent evidence shows that derivatives of Cannabis sativa and its analogs may exert a protective effect against different types of oncologic pathologies. The purpose of the present study was to detect the presence of cannabinoid receptors (CB1 and CB2) on cancer cells with a prostatic origin and to evaluate the effect of the in vitro use of synthetic analogs. In order to do this, we used a commercial cell line and primary cultures derived from prostate cancer and benign prostatic hyperplasia. The presence of the CB1 and CB2 receptors was determined by immunohistochemistry where we showed a higher expression of these receptors in later stages of the disease (samples with a high Gleason score). Later, treatments were conducted using anandamide, 2-arachidonoyl glycerol and a synthetic analog of anandamide, methanandamide. Using the MTT assay, we proved that the treatments produced a cell growth inhibitory effect on all the different prostate cancer cultures. This effect was demonstrated to be dose-dependent. The use of a specific CB1 receptor blocker (SR141716) confirmed that this effect was produced primarily from the activation of the CB1 receptor. In order to understand the MTT assay results, we determined cell cycle distribution by flow cytometry, which showed no variation at the different cell cycle stages in all the cultures after treatment. Treatment with endocannabinoids resulted in an increase in the percentage of apoptotic cells as determined by Annexin V assays and caused an increase in the levels of activated caspase-3 and a reduction in the levels of Bcl-2 confirming that the reduction in cell viability noted in the MTT assay was caused by the activation of the apoptotic pathway. Finally, we observed that endocannabinoid treatment activated the Erk pathway and at the same time, produced a decrease in the activation levels of the Akt pathway. Based on these results, we suggest that endocannabinoids may be a beneficial option for the treatment of prostate cancer that has become nonresponsive to common therapies.
Assuntos
Adenocarcinoma/patologia , Endocanabinoides/farmacologia , Proteínas de Neoplasias/efeitos dos fármacos , Neoplasias da Próstata/patologia , Receptor CB1 de Canabinoide/efeitos dos fármacos , Receptor CB2 de Canabinoide/efeitos dos fármacos , Apoptose/efeitos dos fármacos , Ácidos Araquidônicos/farmacologia , Ciclo Celular/efeitos dos fármacos , Ensaios de Seleção de Medicamentos Antitumorais , Glicerídeos/farmacologia , Humanos , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Masculino , Proteínas de Neoplasias/análise , Proteínas de Neoplasias/antagonistas & inibidores , Piperidinas/farmacologia , Alcamidas Poli-Insaturadas/farmacologia , Hiperplasia Prostática/patologia , Proteínas Proto-Oncogênicas c-akt/antagonistas & inibidores , Pirazóis/farmacologia , Receptor CB1 de Canabinoide/análise , Receptor CB2 de Canabinoide/análise , Rimonabanto , Transdução de Sinais/efeitos dos fármacos , Células Tumorais CultivadasRESUMO
The functional expression of neuronal CB2 cannabinoid receptors (CB2-Rs) in the brain has been controversial. We and others have now demonstrated that CB2-Rs are expressed in neurons and glial cells in the brain. However, the subcellular localization of these receptors has not been characterized. In this study we used immunohistochemical electron microscopy to determine the subcellular distribution of CB2-Rs in two brain regions. Brain sections from the CA1 hippocampal area and substantia nigra were immunostained for CB2-Rs and analyzed by electron microscopy. In each region immunoperoxidase labeling for CB2-Rs was detected in neurons as well as in glial and endothelial cells. In neuronal cells, CB2-R immunoreactivity was observed in somata and large and medium-sized dendrites. In the soma, the CB2-R labeling was mainly associated with the rough endoplasmic reticulum and Golgi apparatus, suggesting its endogenous synthesis. In the dendrites, the CB2-R labeling was observed in the cytoplasm and was associated with the plasma membrane near the area of synaptic contact with axon terminals, indicating a postsynaptic distribution of these receptors. In CB2-Rs in immunoreactive glial and endothelial cells, the labeling was also found to be associated with the plasma membrane. In the substantia nigra, some unmyelinated axons were immunoreactive for CB2-Rs, but we rarely found CB2-R-labeled axon terminals. These results extend our previous detection of postsynaptic cortical CB2-Rs and provide additional ultrastructural evidence that CB2-Rs are mainly postsynaptic in the CA1 area of the hippocampus and substantia nigra. The functional implication of pre- and/or postsynaptic localization of CB2-Rs remains to be determined.