Inhibitory effect of down-regulation of focal adhesion kinase on human colon carcinoma subcutaneous xenograft in nude mice

Objective To investigate the inhibitory effect of suppressing the expression of focal adhesion kinase(FAK) on the growth of xenograft in nude mouse,and explore the possible molecular mechanisms.Methods The colon carcinoma HT29 cells were treated with three methods as follows: conventional culture,transfection with control short hairpin RNA(shRNA),and transfection with FAK shRNA.The cells,after being cultured into multicellular spheroids(MCSs),were respectively transplanted into group A,B and C(5 each),and each animal was given intraperitoneal injection of 200μl saline subsequently.In groups D,E and F(5 each),5-FU(2.5mg/ml) was given instead of saline,and they received the same treatment as group A,B and C.The effects of suppressing FAK expression on the growth of colon carcinoma xenograft and the sensitivity of xenograft to 5-FU were observed.The protein expressions of FAK,p-FAK,Akt,NF-κB,Caspase-3 and Bcl-2 in xenografts were detected by Western blotting.Results The mean weight of tumors were heavier in group A and B than in group D and E(P0.05).Compared with group A,the weight of tumors in group C,D,E and F were significantly lighter(P0.05),and significant difference existed between group F and group C(P0.05).The inhibition of FAK shRNA down-regulated the expressions of p-FAK,Akt,NF-κB and Bcl-2,but up-regulated the expression of Caspase-3 no matter whether 5-FU was added or not.Conclusions Inhibition of FAK expression by FAK shRNA results in decrease in the growth and increase in sensitivity to 5-FU of the xenograft of HT29 in nude mice.The FAK-induced multicellular resistance of colon carcinoma cells is possibly associated with activation of the signal pathway of FAK-Akt-NF-κB.