Antmumor Effects And Mechinism Of Sinoporphyrin Sodium Mediated Photodynamic Therapy In Colorectal Cancer

Background and AimsColorectal cancer is one of the commonest malignant tumors,and the National Central Cancer Registry of China reported that the estimated cancer cases and cancer deaths of CRC ranked fifth among all the cancers.Most patients were diagnosed with advanced tumors.For patients with metastatic CRC,severe side effects were observed when the clinically available treatments(surgical resection,radiation and chemotherapy)were employed,their life quality was poor and the overall 5-year survival dropped dramatically to 5%.Thus,there is urgent need for novel modalities clinically.Photodynamic therapy(PDT)is a promising topical treatment for tumor ablation therapy,with advantages such as: high-efficiency,small side effects,combined with other therapeutic approaches,repeatable,which can greatly improve survival quality and prolong life survival.PDT is considered promising in the treatment of advanced CRC cancers.PDT is based on a photochemical reaction among photosensitizer(PS),exciting light and molecular oxygen,and the research and development of PS is the hot area.Photofrin(PF)was approved as the first PS for tumor therapy by FDA in 1996,and thousands of cancer patients has obtained good therapeutic effect in esophagus,lung,breast and skin cancers,which provided a feasible strategy for patients with advanced cancers,especially for those who were not suitable or refused to accept the traditional therapies.However,high phototoxicity,unknown active ingredients and unaffordable price limited its application in China.Therefore,it was of great importance to develop novel PS with high efficiency and low toxicity and with intellectual property in China.Chinese team carried out systematic research,and found sinoporphyrin sodium(DVDMS),which is suited for industrialization production,easy to be purified and easily soluble in water.DVDMS,compared with PF,possesses remarkable advantages: definite functional component with a purity of up to 98%,controllable quality standard,one-tenth of the dosage,and thus reduced the time period avoiding light.And the discovery was granted intellectual property rights in China,and DVDMS was approved to conduct phase I clinical trial in patients with advanced esophageal cancer.Autophagy,as a built-in cytoprotective mechanism,is widely involved in physiological and pathological processes.Studies have reported that autophagy can help tumor cells,especially the tumor stem cells escape negative stimulation,and resulted in undesirable therapeutic effects and drug resistance of tumor cells.Autophagy inhibitor combine with chemotherapy could overcome tumor resistance to some extent,and enhance the anti-tumor effects,some of the clinical trials have achieved substantial progress.And some studies indicated that PDT could induce apoptosis and autophagy in treated cells,and the functions of autophagy in the anti-tumor process is strongly dependent on multiple factors,such as the type of cells and PS,the dosage of PS.DVDMS is a novel PS,to our best known,related research was rarely reported and no publication was available on induction of autophagy during DVDMS-PDT cancer therapy.Here,we intents to study the impacts of the induction of apoptosis and autophagy in CRC by DVDMS-PDT,and the effects of autophagy to the antitumor efficiency of DVDMS-PDT,in order to explore the antitumor efficiency of DVDMS-PDT and the role of autophagy in the process,so as to provide implications for the clinical treatment of CRC.Methods and ResultsPart 1: CCK-8 assay,morphological observation,colony formation assay,flow cytometry were used to investigate the antitumor efficiency of DVDMS-PDT to HCT116 cells.Further,HCT116 tumor-bearing mice model was established and methods such as HE staining,immunohistochemistry detection were applied to confirm the results of in vitro studies.The experimental results showed that DVDMS-PDT showed good anti-tumor effects in HCT116 cells,and compared to PF-PDT,DVDMS-PDT showed better antitumor efficiency both in vitro and in vivo under the same conditions.What's more,morphological observation,flow cytometry,Western blot,MDC staining,transmission electron microscope,TUNEL and immunohistochemistry detection were applied to explore the mechanism of anti-tumor effects of DVDMS-PDT with respects to apoptosis and autophagy.The results showed that DVDMS-PDT exerted anti-tumor effects by inducing apoptosis,and autophagy was induced in the process.Part 2: On the baisis of the results of mechanism study,we investigaed the role of autophagy and the impacts of autophagy inhibition to the apoptosis of DVDMS-PDT treated HCT116 cells,and the in vivo tests were carried out to confirm the in vitro results.The results suggested that the induced autophagy played an cytoprotective role to the HCT116 cells.Moreover,the pretreatment with chloroquine successfully inhibited autophagy and enhanced the antitumor efficiency of DVDMS-PDT.Interestingly,we found that CQ enhanced the anti-tumor effects of DVDMS-PDT to CD133+ stem cells of HCT116,which might be one of the reasons for the remarkable anti-tumor effects of combined group,related results should be confirmed in the further researches.In this study,CQ was chosen as the only autophagy inhibitor,and the usage and dosage were note explored systematically,detailed study is necessary to be conducted about other kinds of autophagy inhibitors and their usages and dosages for higher efficiency and lower toxicity.ConclusionIn summary,the results suggested that DVDMS-PDT displayed good antitumor effects,DVDMS-PDT was more effective than PF-PDT under the same conditions.DVDMS-PDT exerted anti-tumor effects by inducing apoptosis,however,the induced autophagy played a cytoprotective role to the CRC cells.What's more,inhibition of autophagy with chloroquine enhanced the antitumor efficiency of DVDMS-PDT in HCT116 cells,which may be related to the injury effects on CD133+ CRC stem cells.