The Effect Of Proteasome Inhibitor MG132on Growth, Metastasis, Radiotherapeutic Efficacy In Hunman Non-small Cell Lung Cancer

Objective In this study, the effect of proteasome inhibitor MG132at a low doseon growth, metastasis, apoptosis, cell cycle distribution, radiotherapeutic efficacy, andits accurate mechanism of radiosensitization were investigated in human non-small celllung cancer, in vitro and in vivo.Methods In vitro, after A549and H1299cells were treated with MG132and/orIR，the cell viability was detected by MTT assay; Scratch migration assay and transwellmigration assay were used to determine the migration and invasion ability of A549andH1299cells; Clonogenic survival data was obtained to assess effects of treatment onradiosensitization; Changes of cell apoptosis and cell cycle distribution were analyzedby flow cytometry assay; The protein expression modulated by MG132and IR wereinspected by Western blot analysis. To determine in vivo radiotherapeutic efficacy,tumor growth delay was analyzed in a H1299tumor-bearing xenograft mouse modelafter repeated treatment of MG132and/or IR.Results MG132alone inhibited cell growth in A549and H1299cells, in a dose-and time-dependent manner (P<0.01); MG132at a non-toxic dose enhanced theradiation-induced cytotoxicity of A549and H1299cells, in a radiation dose-andpretreatment time-dependent manner (P<0.01); MG132in combination with radiationsignificantly suppressed the migration and invasion of A549and H1299cells comparedto control (P<0.05); MG132at a non-toxic dose in combination with radiation resultedin decreased clonogenic survival and increased radiosensitivity of A549and H1299cells; MG132enhanced radiation-induced apoptosis in A549and H1299cells (P<0.01);MG132enhanced radiation-induced cell cycle arrest of G1in A549cells, and G2/M inH1299cells (P<0.05); The expression of MMP-2.-9, Bcl-2was significantly suppressedby MG132in combination with radiation both in A549and H1299cells, while the expression of Bax was up-regulated relatively. In A549cells, the expression of cyclinD1was significantly decreased by MG132in combination with radiation, accompanying asignificant increased of P53expression. In H1299cells, MG132in combination withradiation resulted in increased expression of wee1. Otherwise, NF-κB activationinduced by radiation was markedly inhibited by pretreatment with MG132, as well asthe degradation of IκB; Tumor growth in H1299xenograft mice was markedly delayedby systemic administration of MG132combined with IR (P<0.05).Conclusions The present findings have demonstrated that MG132alone inhibitsthe cell growth in human non-small cell lung cancer cell line A549and H1299. MG132at a non-toxic dose enhanced the radiation-induced cytotoxicity of A549and H1299cells, in a radiation dose-and pretreatment time-dependent manner. The migration andinvasion ability of A549and H1299cells treated by MG132in combination withradiation was significantly suppressed, accompanying a significant decrease ofMMP-2,-9expression. MG132at a non-toxic dose in combination with radiationresulted in decreased clonogenic survival and increased radiosensitivity of A549andH1299cells. MG132enhances radiation-induced apoptosis in vitro and in vivo, with amarkedly decrease of Bcl-2expression and increase of Bax expression. MG132enhances radiation-induced cell cycle arrest of G1in A549cells, and G2/M in H1299cells, accompanying changes of cell cycle relative proteins expression. MG132enhanced radiosensitivity of human non-small cell lung cancer in vivo too. Tumorgrowth in H1299xenograft mice was markedly delayed by systemic administration ofMG132combined with IR. Otherwise, the results reveal a novel mechanism forproteasome inhibition MG132mediated radiosensitization, in which inhibition ofNF-κB activation is involved. Results are encouraging for the use of MG132as aradiosensitizing agent in the treatment of human non-small lung cancer.