Radiosensitivity Of Melanoma Cells Research Articles

Overexpression of Ras-Related C3 Botulinum Toxin Substrate 2 Radiosensitizes Melanoma Cells In Vitro and In Vivo.

Radioresistance is the major obstacle in the radiotherapy of the malignant melanoma. Thus, it is of importance to increase the radiosensitivity of melanoma cells. In the present study, the radioresistant melanoma cell line OCM-1 with inducible overexpression of Ras-related C3 botulinum toxin substrate 2 was established based on a radiation-inducible early growth response gene (Egr-1) promoter. The effects of Ras-related C3 botulinum toxin substrate 2 overexpression on the radiosensitivity of melanoma cells exposed to either X-rays or carbon ion beams were evaluated in cultured cells as well as xenograft tumor models. In addition, both reactive oxygen species yield and the NADPH oxidase activity were measured in the irradiated melanoma cells. It was found that the radiation-inducible overexpression of Ras-related C3 botulinum toxin substrate 2 sensitized the melanoma cells to both X-rays and carbon ion irradiation by enhancing the NADPH oxidase activity and the subsequent reactive oxygen species production. Besides, the overexpression of Ras-related C3 botulinum toxin substrate 2 enhanced the tumor-killing effect of radiotherapy in xenograft tumors significantly. The results of this study indicate that Ras-related C3 botulinum toxin substrate 2 is promising in increasing the radiosensitivity of melanoma cells, which provides experimental evidence and theoretical basis for clinical radiosensitization of the malignant melanoma.

Changes of Cancer Stem Cell Markers in Human Ependymoblastoma Following Carbon Ion Beam Irradiation

MTT assay were used to investigate mitochondrial respiration, cell proliferation and radio-resistant cell morphology. Genes involved in mitochondrial respiration, apoptosis, cell division and signaling were quantitatively analyzed by qRT-PCR. Mitochondrial inhibitors were used to block mitochondrial respiration in cells. Results: The apoptosis in melanoma cells were 30% higher and normal melanocyte survival was preserved 80 % with 50cGy delivered at 2400 MU/min than 50cGy delivered at a dose rate of 400MU/min in vitro setting (p<0.005). qRT-PCR data confirmed significant upregulation of apoptosis genes (AIF, FAS, FASL, Casp 3, Casp8, Casp9, TP53) in cancer cells and DNA repair and cell proliferation genes (MSH2, CCND1,CCND2, MDM2, MDM4) in HEM, HEK and HEF. Cell counts showed 60% and 68% reduction at 7 days post-radiation for the aggressive metastatic cells (p<.0.001) and for sensitive cells, respectively. Colony assays demonstrated 30% more cell killing with 2400MU/min than 400 MU/min and preserved 75% normal primary cells. Dose rate 2400 MU/min caused higher mitochondrial respiration than 400 MU/min which was directly related to total dose of radiation delivered to cells. However, the respiratory chain genes (NDUFS2, UCRC, SDHC, ATPAF2) were down regulated, suggesting that the increased respiration activity after radiation was related to post-translational activation. Mitochondrial inhibition increased cell kill to 74% (p<0.005) with inhibitor O and to 83% with inhibitor R while HEM maintained 60% survival. Conclusions: 10 MV x-rays at high dose rate with low total dose (2400 MU/minj50cGy) significantly enhances radio-sensitivity of melanoma cells while reducing radio-toxicity on normal cells. Additionally, blocking mitochondrial respiration proportionately increases melanoma cell kill with this dose rate. Our model implicates potential novel radio therapeutic options and opens untested field of radiation therapy research. Author Disclosure: S. Sarojini: None. N. Milinovikj: None. A. Pecora: None. J. Barbiere: None. M. Tuna: None. S. Jeong: None. J. Jun: None. L. Catello: None. J. Jiang: None. A. Ndlovu: None. A. Ingenito: None. K.S. Suh: None.

The status of microRNA-21 expression and its clinical significance in human cutaneous malignant melanoma

Dysregulation of microRNA-21 plays critical roles in tumor initiation and progression. The purpose of this study was to investigate the status of microRNA-21 expression in human cutaneous malignant melanoma and determine its clinical significance. TaqMan® real-time RT-PCR assay was performed to examine the expression of microRNA-21 in 10 cases of dysplastic nevi, 86 cases of primary cutaneous melanomas, 10 cases of melanoma metastases. The correlation of microRNA-21 expression with clinicopathological factors or prognosis of patients with cutaneous melanoma was statistically analyzed. Additionally, the effects of microRNA-21 expression on growth, apoptosis and chemo- or radiosensitivity of melanoma cells were also investigated by transfection of microRNA-21 inhibitor. We firstly showed that increased levels of microRNA-21 expression were shown from dysplastic nevi to primary cutaneous melanomas to melanoma metastases. Moreover, high miR-21 expression was found to be correlated with Breslow thickness and advanced clinical stage. Patients with high microRNA-21 expression showed shorter 5-year disease-free or overall survival than those with low microRNA-21 expression. Furthermore, multivariate regression analysis showed that the status of microRNA-21 expression was an independent prognostic factor for overall survival of patients. Antisense-mediated microRNA-21 inhibition could significantly suppress growth, increase apoptosis and enhance chemo- or radiosensitivity of human cutaneous melanoma cells by inducing the increased Bax/Bcl-2 ratio. Thus, the status of microRNA-21 might be an independent prognostic factor for patients with cutaneous melanoma, and microRNA-21 has the potential of being a novel molecular target for the treatment of human cutaneous melanoma.

The Effect of Paraquat on the Radiosensitivity of Melanoma Cells: the Role of Superoxide Dismutase &amp; CATALASE

The activities of reactive oxygen species scavenging enzymes, superoxide dismutases (SODs) and catalase (in cells of two melanomas (mouse B16 and human SK23) and in Chinese hamster ovary (CHO) cells were examined. Melanoma cells are relatively depleted in activities of superoxide dismutases and catalase as compared to CHO cells. Short equitoxic (500 microM for CHO and B16 cells and 5 microM for SK23 cells) paraquat treatment (15 min before the X-irradiation, 45 min in postirradiation period--the total time of treatment was 1 h) caused an increase in radiation resistance, measured as colony forming ability, in two of the three lines examined. It is proposed that PQ may exert its radioprotective effect by induction of antioxidant enzymes.

The radiosensitivity of melanoma cells in culture.

There is frequently a poor response to the clinical treatment of malignant melanomas by radiotherapy and it is often stated that many melanomas are resistant to radiation Cade, 1948; Rock Carling, Windeyer and Smithers, 1955). In fact, Paterson (1948) states that if radiation cures the tumour, it was probably not the ordinary malignant melanoma. It does not yet seem clear whether the radio-resistance is due to an intrinsic property of the melanoma cells, such as a high D0, or a large extrapolation number; or whether mechanical or environmental factors, such as depletion of oxygen, are responsible. In an attempt to answer some of these questions, the Harding-Passey melanoma has been trained to grow in single-cell culture and its radiation resistance measured by the traditional Puck cloning technique (Puck, Marcus and Cieciura, 1955).