Effect Of Metformin In Combination With Gemcitabine On The Growth Of Human Pancreatic Cancer(CFPAC-1) Xenograft In Nude Mice

Objective: To evaluate the effect of metformin(MET) combined with gemcitabine(GEM) on the growth of subcutaneous human pancreatic cancer(CFPAC-1)xenografts in nude mice.Methods: The CFPAC-1 cell line in log phase was implanted subcutaneously into Balb/c-nu/nu nude mice to develop xenografts. Twenty mice were randomly divided into four groups: control group(A): inject saline IP; MET group(B): inject MET 200mg/(kg·d) IP daily; GEM group(C): inject GEM 50mg/(kg·d) IP biw; combined group(D): inject MET 200mg/(kg·d) IP daily and GEM 50mg/(kg·d) IP biw. Tumor growth and mouse weight were recorded regularly and cancer inhibition rates were evaluated. 28 days later, the mice were killed and the tumors were weighted and immediately removed for further studies. The m RN A and protein expression level of Bcl- xl, Bax, Survivin, Caspase-3, and Cyclin D1 were detected by RT-PCR and Western Blot, respectively. Simultaneously, the method of immunohistochemistry was used to estimate the protein expression of caspase-3 and PCNA.Results: All the mice formed xenografts and none of them died. The tumor volumes of control group, MET group, GEM group and combined group were(0.840±0.082) cm3,(0.583±0.029) cm3,(0.407±0.029) cm3, and(0.224±0.044)cm3. The tumor weights were(0.910±0.100)g,(0.647±0.044)g,(0.494±0.118)g, and(0.256±0.040)g, respectively. Compared with the control group, tumor growth was significantly inhibited in mice treated with MET, GEM, and combined treatment(P<0.05), especially the combined group. The inhibition rate of MET group, GEM group, and combined group were 28.90±2.23%, 45.71±3.20%, and 71.87±5.04%, respectively. Compared with the control group, the levels of C yclin D1 m RNA, Bcl-xl m RNA, and Survivin m RNA were downregulated in MET group, GEM group, and combined group, whereas the expression of Bax m RN A and Caspase-3 m RNA were upregulated. Compared with MET or GEM monotherapy group, significant difference(P<0.05) was observed in combined group. Compared with the control group, the protein level of C yclin D1, Bcl- xl, and Survivin were downregulated, while the level of Bax and Caspase-3 were upregulated, all mentioned above showed significant difference in combined group when compared with MET or GEM monotherapy group(P<0.05). Immunohistochemistry showed that PCNA and Caspase-3 protein have significant difference in combined group compared with control, MET or GEM group(P<0.05).Conclusions: Metformin could inhibit the growth of pancreatic cancer, and the anti-tumor effect is more obvious when combined with gemcitabine. The mechanism may be related to the inhibition of cell proliferation and induction of apoptosis pathway.