Low-dose Orlistat Promotes The Therapeutic Effect Of Oxaliplatin In Colorectal Cancer

The failure of and resistance to oxaliplatin(OXA)-based chemotherapies may lead to poor prognosis in colorectal cancer(CRC)patients.It has been reported that orlistat(Orli)exhibits potent antitumor effects in several malignant tumors.Here,we identified that OXA in combination with low-dose Orli could sensitize CRC cells to OXA and induce marked synergistic apoptosis in vitro and in vivo.The potential synergistic effects were confirmed and quantified by in silico analysis.Furthermore,we validated the synergistic anti-tumor effects in CRC PDX mice model.A qPCR array was performed to evaluate the changes in 85 apoptosis-related genes to elucidate the possible molecular mechanisms in combination-induced cytotoxicity.To conclude,the antitumor synergistic effects of OXA and Orli make them effective and promising candidates for cancer treatment.Background and Purpose:CRC is the second most common cancer in the world and carries a high risk of cancer-related death.Currently,surgery,chemotherapy,radiotherapy,and immunotherapy are important strategies for the treatment of colorectal cancer.OXAbased chemotherapy regimens are first-line treatments for advanced colorectal cancer,but long-term repeated use may lead to chemotherapy failure or resistance,severely hampering outcomes in patients with CRC.In addition,the toxic side effects of chemotherapy regimens(FOLFOX or CapeOx),including hematologic,gastrointestinal,and neurotoxicity,limit the continuity of treatment application and hinder clinical treatment.Therefore,there is an urgent need to study a novel chemosensitizer as a new combination of OXA to improve the efficacy and safety of clinical treatment.Orli is a potent and irreversible fatty acid synthase(FASN)inhibitor whose primary function is to block fat absorption in the human diet.Due to its effects on lipid metabolism,Orli has been shown to exhibit potent antitumor effects in a variety of malignancies,including gastrointestinal cancer,but the efficacy of its combination with oxaliplatin in the treatment of CRC and its intrinsic molecular mechanism have not been reported.Methods and materials:In vitro experiments,the human colorectal cancer cell lines HCT116 and LOVO were selected as the research objects,and the optimal dose of Orli and OXA was determined according to the results of drug combination response,cell viability determination,scratch experiment,and clone formation under different treatment regimens.The synergistic therapeutic effects of low-dose Orli and OXA were explored by plotting growth curves,measuring apoptosis ratios and cell cycle by flow cytometry.In vivo experiments,the synergistic therapeutic effect of low-dose Orli and OXA was verified by constructing a subcutaneous tumor model(CDX)and a human-derived tumor tissue xenograft(PDX)model for colorectal cancer,and the systemic toxicity and side effects of the combined drug regimen were evaluated by mouse organ indices and HE assay of tissue section.Further microarray assessment of changes in 85 apoptosis-related genes was performed to elucidate possible molecular mechanisms in combination-induced cytotoxicity.Results:1.In vitro experiments,Orli was administered at 31.25 μM,which was the lowest concentration of the combination drug(OXA and Orli)for 72 h to produce the strongest synergistic effect,and the growth rate of HCT116 and LOVO cells decreased significantly.2.OXA and low-dose Orli treated CRC cells increased apoptosis rate,especially late apoptosis increased.OXA and low-dose Orli treated CRC cells stagnated in G1 phase.3.In CDX model,low-dose orlistat(50 mg/kg)enhanced oxaliplatin induced apoptosis and cytotoxicity in colorectal cancer,and TUNEL staining observed the highest apoptosis rate in the OXA combined Orli treatment group.4.In vivo toxicity analysis showed no statistical difference in organ indexes,and no significant damage was observed in HE sections.5.In PDX model,low-dose orlistat(50 mg/kg)enhanced oxaliplatin induced apoptosis and cytotoxicity in colorectal cancer6.A microarray was used to evaluate 85 apoptosis-related genes in tumor tissues in PDX model.In the OXA combined with Orli treatment group,21 specific apoptosisrelated genes were obtained.13 genes were up-regulated and eight genes were downregulated.Furthermore,we further verified these results in HCT116 and LOVO cell linesConclusion:1.Orlistat at concentrations much lower than IC50 can still synergistically enhance the cytotoxicity of oxaliplatin to CRC cells.2.Low-dose orlistat can enhance the synergistic cytotoxicity of oxaliplatin by inducing and increasing apoptosis,which can effectively improve the therapeutic efficiency of CRC in vitro and in vitro,and has safe and mild side effects.3.The combination of OXA and Orli significantly enhances the apoptosis pathway.4.These results suggest that OXA in combination with low-dose Orli is a promising clinical treatment strategy.