Effects of Radiotherapy in Combination With Irinotecan and 17-AAG on Bcl-2 and Caspase 3 Gene Expression in Colorectal Cancer Cells

Abstract

Introduction: In this study, the cytotoxic and anti-cancer effects of Irinotecan as a conventional chemotherapeutic agent compared to 17-(allyl amino)-17-demethoxygeldanamycin (17-AAG) as possible radiosensitizers in the HCT-116 cell line were investigated. Methods: HCT-116 cells were treated with various concentrations of irinotecan and 17-AAG and also irradiated with a 2-Gy of X-ray radiation. Then, the cell viability was examined by a water-soluble tetrazolium-1 assay after 24 hours. For single therapies and double and triple combination cases, IC50, 0.5×IC50 and 0.25×IC50 concentrations of each drug were selected respectively for a terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL) assay and other tests. In treated and untreated cells, the caspase 3 and Bcl-2 gene expression ratios were evaluated by the real-time PCR method. Likewise, caspase 3 activity was detected with a colorimetric assay. Results: In all combined treatments, including 17-AAG- radiation, irinotecan - radiation, irinotecan -17-AAG, and irinotecan-17-AAG-radiation, decreased cellular viability and increased TUNEL positive cells were presented versus the control group (P<0.05). There were increased TUNEL positive cells in the triple combination, in concentrations of 0.25×IC50 of each drug, in comparison with single and double agent treatments. Moreover, in triple combination, the caspase 3 mRNA level and caspase 3 activity increased versus related single treatments. Likewise, in the irinotecan-17-AAG-radiation combined treatment and the 17-AAG-radiation double treatment, the Bcl-2 gene expression level decreased in comparison with single therapies. Conclusion: It can be indicated that the combination of chemo-radiotherapy versus single treatments has significant anti-cancer effects.

Radiosensitizing Effects of Irinotecan versus Oxaliplatin Alone and in Combination with 5-Fluorouracil on Human Colorectal Cancer Cells

“…The HT-29 chells we used are also characterized by a p53 mutation. Since we found no effect in irradiated cells treated with oxaliplatin and 5-FU, our results correspond to those of Magné et al With regard to irinotecan, Ebrahimpour [59] demonstrated a significant reduction in the MTT-assay in HCT-116 cells 24 h after the treatment with irradiation or irinotecan. In our study, there was no difference at this time point, possibly due to different cell lines.…”

“…The radiosensitive activity of oxaliplatin was first described by Blackstock et al in 1999 [ 43 ] in an abstract of the 41st annual ASTRO meeting, and, in the last two decades that followed, several preclinical studies investigated its cytotoxic effects in combination with irradiation but not on human colorectal cancer cells [ 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 ]. Similar, preclinical studies reported on the cytotoxic effects of irinotecan [ 17 ] on colorectal cancer [ 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 ] or non-colorectal [ 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 ] cancer cells. The aim of these studies was to determine the influence of oxaliplatin [ 44 , 46 , 47 , 51 , 52 , 53 , 54 , 55 , 57 ] and irinotecan [ 63 , 64 , 65 , 66 ] on cellular pathways, cell cycle and mechanisms of drug resistance or to describe mechanisms of radiosensitization and radioresistance with oxaliplatin [ 45 , 48 , …”

“…Similar, preclinical studies reported on the cytotoxic effects of irinotecan [17] on colorectal cancer [59][60][61][62][63][64][65][66][67] or non-colorectal [68][69][70][71][72][73][74][75][76] cancer cells. The aim of these studies was to determine the influence of oxaliplatin [44,46,47,[51][52][53][54][55]57] and irinotecan [63][64][65][66] on cellular pathways, cell cycle and mechanisms of drug resistance or to describe mechanisms of radiosensitization and radioresistance with oxaliplatin [45,[48][49][50]56,58] and irinotecan [59][60][61][62]67]. Other preclinical studies compared the effects of oxaliplatin with those of irinotecan [77][78][79][80]…”

“…The radiosensitive activity of oxaliplatin was first described by Blackstock et al in 1999 [43] in an abstract of the 41st annual ASTRO meeting, and, in the last two decades that followed, several preclinical studies investigated its cytotoxic effects in combination with irradiation but not on human colorectal cancer cells [44][45][46][47][48][49][50][51][52][53][54][55][56][57][58]. Similar, preclinical studies reported on the cytotoxic effects of irinotecan [17] on colorectal cancer [59][60][61][62][63][64][65][66][67] or non-colorectal [68][69][70][71][72][73][74][75][76] cancer cells. The aim of these studies was to determine the influence of oxaliplatin [44,46,47,[51][52][53][54][55]57] and irinotecan [63][64]…”