Study On The Function Of HIF-1 And ASK1 In The Formation Of Chemotherapy Resistance Of Hepatoma Cell Line SMMC-7721 During Hypoxia

[Objective]To investigate the difference of the oxaliplatin therapy effect to human hepatoma cells SMMC-7721 between the condition of hypoxia and normoxia. And to explore the chemotherapy resistance mechanism through the study of transcription and expression level of HIF-1α and ASK1 on an apoptosis hypothesis.[Methods]After 24h growth under normoxia or hypoxia condition with different oxaliplatin ultimate concentrations (16umol/L,32 umol/L, 64 umol/L, 128 umol/L and 256 umol/L), human hepatoma cells SMMC-7721 proliferation was determined by MTT assay and the 50% cell-inhibition concentrations were measured for different culture conditions. The transcription and translation levels of HIF-1α and ASK1 were measured after different oxygen conditions for different time. Among the control group, oxaliplatin-normoxia 24h group and oxaliplatin-hypoxia 24h group, the expression level difference was compared as to these two genes.[Results]After MTT tests, the inhibitor roles were observed at different drug concentrationsfor the SMMC-7721 cells, which got much more significant as the drug concentration elevated. As far as any concentration was concerned, oxaliplatin played a more significant suppressive role under normoxia condition. The 50% cell-inhibition concentrations for normoxia and hypoxia condition were 85.9 umol/L and 226.1 umol/L, respectively. The transcription levels of HIF-1 a and ASK1 elevated as the hypoxia condition lasted, which amounted to the peak level at 24h. The expression level of HIF-1 a acted as its transcription level during hypoxia, but ASK1 expression increased as hypoxia culture continued and it got to the peak at 12h. when it became to decrease. Under the treatment with oxaliplatin of normoxia 50% cell-inhibition condition, HIF-1 a over-expressed in the oxaliplatin-hypoxia 24h group, but it expressed at a very low level in other two groups. However, ASK1 expressed highest in the oxaliplatin-normoxia 24h group and higher in the oxaliplatin-hypoxia 24h group compared by the control group.[Conclusions)1. Hypoxia condition helps to form the chemotherapy resistance effect.2. HIF-1 a suppresses the ASK1 at the level of translation not at the level of transcription.3. ASK1 is related with oxaliplatin in the treatment of liver carcinoma through apoptosis mechanism, which may be interfered with by HIF-1. And HIF-1 gene participates the apoptosis process indirectly.