Abstract 308: In-vitro combination analysis for colossolactone-G with gemcitabine and 5-fluoruracil against colorectal cancer cells
Authors: Rinad A. Aljohani, Riham S. Eldine, Gehan A. Hegazy, Aliaa A. Alamoudi, Ghada A. Agabnoor, Ali M. El-Halawany, Ahmed M. Al-Abd
Journal: Cancer Research (2019)

Abstract Naturally occurring terpenoids isolated from Ganoderma colossum showed potential chemotherapeutic properties. In the current work, we assessed the potential chemomodulatory effects of colossolactone-G to gemcitabine (GCB) and 5-fluorouracil (5FU) against colorectal cancer cells. Colossolactone-G induced moderate cell killing effects against both HT29 and HCT116 cells with IC50’s of 90.5±1.7 µM and 22.3±3.9 µM, respectively. By equitoxic combination, colossolactone-G synergized the cytotoxic effects of GCB and 5FU against both HT29 and HCT116 cells resulting in combination index ranging from 0.22 to 0.67. By assessing cell cycle distribution, both GCB and 5FU induced moderate cell cycle arrest at G0/G1-phase and S-phase. Despite colossolactone-G lacks any influence on cell cycle distribution, it significantly potentiated GCB and 5FU induced cell cycle arrest in S-phase and G2/M-phase. Longer exposure (48 h) of cells to colossolactone-G alone induced antiproliferative effect and accumulation of cells at G0/G1-phase. In addition, cell cycle arrest attributed to GCB, 5FU, colossolactone-G and their combinations was accompanied by significant accumulation of cells at Pre-G phase which is indicative of cell death. Further assessment for cells undergoing apoptosis was measured using annexin-V/FITC and PI staining coupled with flowcytometric analysis. Similarly, colossolactone-G treatment alone did not induce any significant apoptosis in both cell lines. However, 5FU and GCB induced significant apoptosis which was further potentiated by colossolactone-G combination. Besides, autophagic death within HCT116 and HT29 cells was assessed using acridine orange lysosomal stain coupled with flow-cytometric analysis in response to single and combination treatments of 5FU, GCB, colossolactone-G. In HCT116, colossolactone-G significantly suppressed the process of autophagy and decreased acridine orange lysosomal fluorescence signal to 52.7% of control cells. On the other hand, colossolactone-G significantly increased autophagic response in HT29 cells. GCB treatment alone decreased autophagic signal within HT29 cells. However, colossolactone-G combination with 5FU or GCB resulted in significant increase in autophagy by 8.7% and 82.7% of control cells, respectively. In conclusion, colossolactone-G represents promising chemomodulatory adjuvent to GCB and 5FU via potentiating their apoptotic, autophagic and cell cycle interference properties. Citation Format: Rinad A. Aljohani, Riham S. Eldine, Gehan A. Hegazy, Aliaa A. Alamoudi, Ghada A. Agabnoor, Ali M. El-Halawany, Ahmed M. Al-Abd. In-vitro combination analysis for colossolactone-G with gemcitabine and 5-fluoruracil against colorectal cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 308.