The Effect Of 5-AIQ-Induced PARP Inhibition On The Proliferation Of Murine Colon Carcinoma CT26 Cell Lines And Its Mechanism

Objective: The aim is to investigate the effect of 5-AIQ-induced poly(ADP-ribose)polymerase(PARP) inhibition on the proliferation of murine colon carcinoma CT26 cell lines in vitro,and how it plays its role.Methods: The murine colon carcinoma CT26 cell lines were treated with various concentrations of 5-AIQ in vitro.MTT assay and flow cytometry(FCM) were used to determine the proliferation and Cell cycle of CT26 cells,separately.The expressions of PARP and NF-κBp65 were investigated by laser scanning cofocal microscope and Western Blot. The NF-κB DNA binding activity was detected by electrophoretic mobility shift assay(EMSA). And the forming of PARP～NF-κBp65 complex was analysed by co-immunoprecipitation.Results: 1. The inhibitory ratio of the proliferation in 5-AIQ-treated colon carcinoma CT26 cell groups was respectively 17.52%,27.63% and 39.93%. The inhibitory ratio increased with the raising of the concentration of 5-AIQ(100μM,500μM,1000μM)(P<0.05).After treatment with 5-AIQ , the proportion of cells in G₀/G₁ phases increased,and the proportion of cells in S phase decreased.The proportion of cells in G₀/G₁ phases in the high concentration 5-AIQ-treated group was more than that in the low concentration 5-AIQ-treated group.2. There is a co-expression and positive correlation of PARP and NF-κBp65 in colon carcinoma CT26 cells(P<0.05). The expressions of PARP and NF-κBp65 were attenuated in 5-AIQ-treated CT26 cell groups, and the correlation of PARP and NF-κBp65 was also positive(P<0.05).The NF-κB DNA binding activity was reduced in 5-AIQ-treated CT26 cell groups(P<0.05). Both PARP and NF-κBp65 were detected when immunoprecipitated with an antibody against NF-κBp65 or PARP.And the PARP～NF-κBp65 complex was less in 5-AIQ-treated colon carcinoma CT26 cell group than that in 5-AIQ-untreated group (P<0.05).Conclusion:1. The inhibitory ratio of the proliferation was different in different concentration of 5-AIQ-treated colon carcinoma CT26 cell groups. And it increased as the concentration of 5-AIQ increased(P<0.05).The proportion of cells in G₀/G₁ phases also increased in 5-AIQ-treated groups.These results suggest that 5-AIQ can inhibit the proliferation of CT26 cells in vitro and influence the cell cycle.2. The expressions of PARP and NF-κBp65 were reduced in 5-AIQ-treated colon carcinoma CT26 cell groups.The NF-κB activity was inhibited by 5-AIQ. The PARP～NF-κBp65 complex also decreased in 5-AIQ-treated CT26 cells.These results suggest that the proliferation of CT26 cells was inhibited by 5-AIQ in vitro is probably through inhibiting PARP, then inhibiting the forming of PARP～NF-κBp65 complex and NF-κB activity. PARP may play a role in the proliferation of colon carcinoma.