Enhancement of Hypoxia-Induced Tumor Cell Death In vitro and Radiation Therapy In vivo by Use of Small Interfering RNA Targeted to Hypoxia-Inducible Factor-1α

Abstract

Hypoxia-inducible factor-1␣ (HIF-1␣) is an important transcriptional factor that is activated when mammalian cells experience hypoxia, a tumor microenvironmental condition that plays pivotal roles in tumor progression and treatment. In this study, we examined the idea of downregulating HIF-1␣ in tumor cells for therapeutic gain. We show that the expression levels of HIF-1␣ can be significantly attenuated by use of the recently established small interfering RNA technology in combination with adenovirus-mediated gene transfer. Down-regulation of the HIF-1␣ protein enhanced hypoxia-mediated tumor cell apoptosis in vitro. Subcutaneous tumor growth was also prevented from cells with attenuated HIF-1␣ expression. In addition, intratumoral injection of adenovirus encoding the HIF-1␣-targeted small interfering RNA had a small but significant effect on tumor growth when combined with ionizing radiation. Therefore, our results provide proof of HIF-1␣ as an effective target for anticancer therapy. They also suggest that an adenovirus-based small interfering RNA gene transfer approach may be a potentially effective adjuvant strategy for cancer treatment.

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

“…The underlying molecular mechanism involves markedly reduced expression of DNA-PKcs, Ku80 and Ku70, three members of the DNA-dependent protein kinases (DNA-PK), in HIF-1 α -deficient MEFs. Our data were supported by a large number of studies that demonstrated reversal of radio-and chemoresistance by targeting HIF-1 α in various tumor types (Zhang et al , 2004 ;Moeller et al , 2005 ;Williams et al , 2005 ;Brown et al , 2006 ;Li et al , 2006a,b ;Song et al , 2006 ;Sasabe et al , 2007 ). 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 ).…”

Dauricine inhibits insulin-like growth factor-I-induced hypoxia inducible factor 1α protein accumulation and vascular endothelial growth factor expression in human breast cancer cells

“…Real-time PCR analysis of HIF-1α and VEGF mRNA levels was performed using the iScript TM One-step RT-PCR Kit with SYBR® Green, according to the manufacturer's instructions. The following primers were designed for real-time PCR: HIF-1α, forward 5′-GTTTACTAAAGGACAAGTCACC-3′ and reverse 5′-TTCTGTTTGTTGAAGGGAG-3′ [19] ; VEGF, forward 5′-TCTACCTCCACCATGCCA AGT-3′ and reverse 5′-GATGATTCTGCCCTCCTCCTT-3′ [20] ; β-actin, forward 5′-TCAAGATCATTGCTCCTCCTG-3′ and reverse 5′-CTGCTTGCTGATCCACATCTG-3′ [21] . All the primers were synthesized by Shanghai Sangon Biological Engineering Technology and Services Co, Ltd (Shanghai, China).…”

Inhibition of HIF-1α by the anticancer drug TAS106 enhances X-ray-induced apoptosis in vitro and in vivo

“…The adaptational response of tumour cells against hypoxia is thought to be mainly mediated by HIF-1a, which transactivates a number of target genes leading to metabolic adaptation, angiogenesis, invasion/metastasis and apoptosis resistance (Semenza, 2003). Recent studies reported that interfering treatments targeting HIF-1a, such as antisense or siRNA, induced apoptosis of human tongue squamous carcinoma cells in vitro (Zhang et al, 2004a) and inhibited tumour growth in human cervical and colon adenocarcinoma cells in vivo (Zhang et al, 2004b). In this experiment, we demonstrated that the reduction of the constitutive level of HIF-1a by an antisense HIF-1a oligonucleotide markedly increased the number of apoptotic cells ( Figure 6C).…”