Objective To determine whether suppressing the expression of focal adhesion kinase (FAK) in colon carcinoma cell line HT29 will reverse colon carcinoma multicellular resistance. Methods The cells were divided into untreat HT29 cells

control shRNA cells

and FAK shRNA cells. The suppression of FAK and FAKp expression in monolayer culture cells of the above 3 groups were detected by immunocytochemistry and Western blotting analysis. Effects o

f suppressing FAK on the drug sensitivity to 5 - FU of monolayer and multicellular spheroid culture cells were quantified by MTT assay. Effects of suppressing FAK on 5 - FU - induced apoptosis and natural apoptosis of multicellular spheroids were determined by flow cytometry (FCM). Effects of FAK shRNA interference on protein expressions of Akt

NF - κ B

Bcl - 2

and Caspase - 3 of monolayer culured cells were detected by immunocytochemistry

and their protein expressions in multicellular spheroid culture cells were detected by Western blotting. Results RNA interference targeting FAK markedly suppressed FAK and FAKp protein expressions in monolayer culture cells. MTT assay indicated that FAK shRNA interference enhanced the drug sensitivity to 5 - FU of monolayer and multicellular spheroid culture cells evidently

especial the latter

but the difference between the 2 was not markedly (

P

0 . 05). FCM manifested that FAK shRNA interference stimulated natural apoptosis and 5 - FU - induced apoptosis markedly in multicellular spheroid cells (

P

=0 . 001

P

=0 . 000)

and the difference between the 2 was markedly (

P

=0.003 ） . Following FAK shRNA treatment

Akt

NF - κ B and Bcl - 2 levels were obviously suppressed

but the Caspase - 3 level was obviously upregulated both in monolayer and in multicellular spheroid cells. Conclusion Suppressing FAK enhances the drug sensitivity of colon carcinoma multicellular spheroid cells to 5 - FU through a FAK/Akt/NF - κ B signaling pathway

and reverses multicellular resistance at the same tme.