Study On The Mechanism Of Cantharidin On Pancreatic Cancer Radiosensitization

Objective:Pancreatic cancer is highly malignant,80%of patients in the diagnosis has been in the late,can not be radical surgery.For these patients,palliative radiotherapy and chemotherapy is the main treatment is one of the most fatal of human tumors,is the sixth leading cause of malignant tumors in China.Radiation therapy is gradually becoming an important palliative treatment for pancreatic cancer.However,endogenous and acquired radiological resistance is a major obstacle to the current treatment of pancreatic cancer.Previous studies have suggested that the active ingredient of cantharides,Cantharidin?Cantharidin,the active ingredient of cantharides in Chinese medicine?can inhibit the growth of pancreatic cancer and other tumor cells.Cantharidin can block pancreatic cancer cell cycle in G2/M phase.Since G2/M phase cells are sensitive to radiation,cantharidin may have radiosensitizing effects.Methods:1.Cell cycle distribution was analysed by using PI staining and flow cytometry.2.Irradiation-induced DNA damage was evaluated by using?-H₂A.X analysis.3.RT-PCR was performed to estimate the mRNA expressions of genes associated with DNA repair and damage.4.For cell signaling transduction investigation,JNK pathway inhibitor SP600125,ERK pathway inhibitor PD98059,PKC pathway inhibitor GF109203X,p38 MAPK pathway inhibitor Birb 796,NF-k B pathway inhibitor Bay11-7082 were used.5.Correlation analysis validates the correlation between gene chips and Real-tme PCR.6.Cellular growth was evaluated by MTT assay.Results:1.Cell cycle distribution was analysed by using PI staining and flow cytometry.Cantharidin drove pancreatic cancer cells out of G0/G1 phase and arrested cell cycle in G2/M phase.2.we evaluated irradiation-induced DNA damage upon co-treatment with cantharidin by using?-H2A.X analysis.Cantharidin strengthened DNA damage induced by irradiation.3.By using microarray assay,we identified that cantharidin repressed expressions of genes participating in DNA damage repair.By using Real-Time PCR,we found that blocking certain specific pathway inhibitors attenuates the inhibitory effect of cantharidin on the expression of DNA damage repair genes.4.SP600125,PD98059,GF109203X,Birb 796,Bay11-7082could attenuate the repression on DNA damage repair genes by cantharidin.5.Correlation analysis showed that the correlation between the gene chip and Real-tme PCR was similar to that of Real-tme PCR.6.Inhibitory effect of cantharidin on pancreatic cancer cell growth by MTT assay.Conclusion:Cantharidin can drive cells out of the radiation relative to the CAN can drive cells out of the radiation is relatively insensitive to the resting G0/G1 phase and block the radiation-sensitive G2/M phase,and thus enhance the radiation-induced DNA damage.On the other hand,cantharidin inhibits the expression of genes involved in DNA damage repair by JNK,ERK,PKC,p38 MAPK,NF-?B pathway,thereby further enhancing radiation-induced DNA damage.In addition,blocking JNK,ERK,PKC,p38 MAPK,NF-?B pathway attenuated the inhibitory effect of cantharidin on DNA damage repair gene expression,and cantharidin itself inhibited the growth of pancreatic cancer cells,suggesting that Pancreatic cancer cells have a radiosensitizing effect on radiation therapy and are expected to be used as a sensitizer for radiotherapy for the treatment of pancreatic cancer.