ABSTRACT
The aim of the work was to investigate the effect and possible mechanism of MENK on the growth of rat C6 glioma in vivo or in vitro. Our findings showed that MENK could inhibit the growth of rat C6 glioma, prolong median survival times in tumor-bearing rats, and induce glioma cell apoptosis. Moreover, MENK could increase the activities of caspase-3, caspase-8 and caspase-9. It also increased the expression of Fas, FasL, Bax, while decreased the expression of Bcl-2. We further confirmed that MENK could increase opioid receptors MOR and DOR expressions, Ca2+ influx into the cytoplasm, and a substantial increase of NFAT1accumulation in the nuclei in C6 glioma cell. When we specifically knocked down NFAT1, there was no effect of MENK on the cell viability and FasL up-regulation in NFAT1 knocked-down cell. These results demonstrate that MENK could bind to opioid receptors MOR and DOR on C6 glioma cells and trigger a Ca2+ influx into the cytoplasm, resulting in translocation of NFAT1 into the nucleus. The hyper-activation of NFAT1 may regulate transcription of downstream gene, such as FasL, and induce apoptosis of rat C6 glioma cells.
Subject(s)
Brain Neoplasms/metabolism , Enkephalin, Methionine/metabolism , Glioma/metabolism , NFATC Transcription Factors/metabolism , Animals , Apoptosis , Brain Neoplasms/genetics , Calcium Signaling , Caspases/metabolism , Cell Line, Tumor , Fas Ligand Protein/metabolism , Glioma/genetics , NFATC Transcription Factors/genetics , Neoplasm Transplantation , RNA, Small Interfering/genetics , Rats , Rats, Wistar , Transcriptional Activation , Up-Regulation , bcl-2-Associated X Protein/metabolismABSTRACT
Melanoma is a common cutaneous malignancy, that is also found in specific mucosal sites, and is associated with a poor prognosis. The aim of the present study was to investigate the cytotoxicity of methionine enkephalin (MENK) for B16 melanoma cells in vivo and in vitro. The results of the present study allowed our conclusion that MENK regulates the proliferation of B16 cells, causing cell cycle arrest in the G0/G1 phase and a decrease in the percentage of cells in the S and G2/M phases. Reverse transcription-quantitative polymerase chain reaction demonstrated that MENK increased opioid receptor expression in the B16 cells. Furthermore, the tumor volume and weight in the MENK-treated group were lower than those in the control group (NS) and MENK and naltrexone (NTX)-treated groups. MENK exerted both significant antitumor activity on the growth of B16 cells and a longer survival time in mice. The mice treated with MENK exhibited an increased ratio of CD4+ to CD8+ T cells as tested by flow cytometry (FCM), resulting in a ratio of 2.03 in the control group, 3.69 in the MENK-treated group, and 2.65 in the MENK and NTX group. Furthermore, a significant increase in plasma levels of IL-2, IFN-γ and TNF-α was revealed as assessed by ELISA. In conclusion, the results of the present study indicate that MENK has a cytotoxic effect on B16 melanoma cells in vitro and in vivo, and suggest a potential mechanism for these bioactivities. Therefore, we posit that MENK should be investigated, not only as a primary therapy for melanoma, but also as an adjuvant therapy in combination with chemotherapies.
Subject(s)
Enkephalin, Methionine/administration & dosage , Interferon-gamma/genetics , Interleukin-2/genetics , Melanoma, Experimental/drug therapy , Tumor Necrosis Factor-alpha/genetics , Animals , Cell Cycle Checkpoints/drug effects , Cell Proliferation/drug effects , Dendritic Cells/drug effects , Enzyme-Linked Immunosorbent Assay , Flow Cytometry , Gene Expression Regulation, Neoplastic/drug effects , Humans , Melanoma, Experimental/genetics , Melanoma, Experimental/pathology , Mice , Naltrexone/administration & dosage , Tumor Burden/drug effectsABSTRACT
Melanoma is an aggressive cancer, the incidence of which is increasing worldwide. Limited therapies are currently available, particularly following metastasis. The aim of the present study was to investigate the inhibiting effect of methionine enkephalin (MENK) on human melanoma via opioid receptors. The results of the present study revealed that MENK markedly regulates the proliferation of A375 cells, causing cell cycle arrest in G0/G1 phase and a decrease in the percentage of cells in S and G2/M phases. Reverse transcriptionquantitative polymerase chain reaction demonstrated that MENK treatment increased opioid receptor expression in A375 cells. Furthermore, the expression level of survivin, an inhibitory apoptotic protein, was 1.1% of the level in the control group in the MENK group following 48 h of treatment. In conclusion, the results of the present study revealed, to the best of our knowledge for the first time, that MENK may inhibit growth and induce apoptosis of A375 cells, and describes a potential mechanism underlying these effects. Therefore, MENK should be investigated as a primary therapy for human melanoma cancer and as an adjuvant to other chemotherapies. Further studies are required to develop an optimal strategy for the use of MENK for the treatment of human cancers.
