Effects of lentivirus-mediated HIF-1α knockdown on hypoxia-related cisplatin resistance and their dependence on p53 status in fibrosarcoma cells

Abstract

Therapy targeting hypoxia-inducible factor-1 (HIF-1) to reverse the hypoxia-related drug resistance has received much interest. Despite a close interaction between HIF-1 and p53 and that p53 mutation is seen in 450% of tumors, whether HIF-1 silencing by targeted therapy depends on tumor p53 status remains unknown. Two isogenic fibrosarcoma cells HT1080 (wild-type p53) and HT1080-6TG (mutant p53) were transduced with HIF-1a-specific RNAi lentiviral vectors and selected with blasticidin. Real-time PCR and western blot analysis of HIF-1a mRNA and protein respectively validated the silencing effects. Cells were first preconditioned under hypoxia (0.5% O 2 ) for 4 h and then co-treated with cisplatin for another 24 h. MTT was used for assessment of chemosensitivity to cisplatin. Moreover, annexin V and propidium iodide staining was detected on flow cytometry for analysis of cisplatin-induced apoptosis. Furthermore, changes of some Bcl-2 family members were detected on western blotting. Exposure to hypoxia significantly increased resistance to cisplatin than exposure to normoxia. HIF-1a knockdown could reverse hypoxia-related resistance to cisplatin and apoptotic resistance only in HT1080 cells, but had little effect on HT1080-6TG cells. With HIF-1a knockdown, Bid expression was higher in HT1080 than in HT1080-6TG under hypoxia. In summary, HIF-1 targeted therapy to reverse hypoxia-related cisplatin resistance depends on normal p53 status. Changes of Bid expression levels under hypoxia might contribute in part to the differential response to HIF-1a silencing in cells with different p53 status.

Contribution of HIF-1 and drug penetrance to oxaliplatin resistance in hypoxic colorectal cancer cells

“…The mechanisms by which HIF-1 contributes to resistance are likely to be complex and varied depending on cell genotype. Indeed, recent data observing sensitisation to cisplatin using HIF-targeting RNAi suggest that reversal of hypoxic resistance is p53 dependent (Hao et al, 2008). We previously reported that HIF-1 can alter the balance of pro-and antiapoptotic proteins under hypoxic conditions (Erler et al, 2004).…”

Targeting the translational apparatus to improve leukemia therapy: roles of the PI3K/PTEN/Akt/mTOR pathway

“…173 This may occur in part by suppressing glucose transporter-1 and vascular endothelial growth factor expression, 173 although other investigators have observed that suppression of HIF-1a will also affect the expression of Bcl-2 family members such as Bid. 174 Thus, targeting mTOR expression would influence the expression of HIF-1a and may prevent drug resistance.…”

HIF mediated and DNA damage independent histone H2AX phosphorylation in chronic hypoxia

“…For example, Li et al (2006a,b) showed that the knockdown of HIF-1 α in breast carcinoma cells repressed G 0 /G 1 -phase accumulation and relieved S-phase block, thereby increasing sensitivity to chemotherapy and attenuating tumor growth (Li et al , 2006a,b ). Functional interference with HIF-1 α in various tumor cells has been shown to result in enhanced cell death upon treatment with chemotherapeutic agents (Ricker et al , 2004 ;Peng et al , 2006 ;Hao et al , 2008 ;Sermeus et al , 2008 ;Flamant et al , 2010 ). However, experimentally increasing HIF-1 α enhanced therapy resistance (Ji et al , 2006 ;Martinive et al , 2006 ).…”