Hypoxia inducible factor-1 alpha as a therapeutic target in multiple myeloma

Abstract

The increasing importance of hypoxia-inducible factor-1α (HIF-1α) in tumorigenesis raises the possibility that agents which specifically inhibit this transcription factor, would provide significant therapeutic benefit. The constitutive expression of HIF-1α in about 35% of Multiple Myeloma (MM) patients suggests HIF-1α suppression might be part of a therapeutic strategy. Accordingly, we explored the effect of EZN-2968, a small 3rd generation antisense oligonucleotide against HIF-1α, in a panel of MM cell lines and primary patients samples. Here, we demonstrated that EZN-2968 is highly specific for HIF-1α mRNA and that exposure of MM cells to EZN-2968 resulted in an efficient and homogeneous loading of the cells showing a long lasting low HIF-1α protein level. In MM cells, HIF-1α suppression induced a permanent cell cycle arrest by prolonging S-phase through cyclin A modulation and in addition it induced a mild apoptotic cell death. Moreover, HIF-1α suppression caused a metabolic shift that leaded to increased production of ATP by oxidative phosphorylation (i.e. Warburg effect reversion), that was confirmed by the observed mitochondrial membrane potential decrease. These results show that HIF-1α is an important player in MM homeostasis and that its inhibition by small antisense oligonucleotides provides a rationale for novel therapeutic strategy to improving MM treatment.

The Inhibitor Protein (IF1) of the F1F0-ATPase Modulates Human Osteosarcoma Cell Bioenergetics

“…The inner mitochondrial membrane potential was measured by staining cells with 20 nM tetramethylrhodamine methyl ester (TMRM) (Molecular Probes, Eugene, OR), a lipophilic probe that enters mitochondria in a ⌬ m -dependent manner (25). The cells were incubated with the probe for 30 min at 37°C in the absence or presence of 0.6 M oligomycin and wells were then washed twice with Hanks' balanced salt solution to remove any remaining unincorporated dye.…”

Therapeutic targeting of hypoxia and hypoxia-inducible factor 1 alpha in multiple myeloma

“…61,62 Recently, our group have tested the efficacy of EZN-2968 oligonucleotide in a panel of human MM cell lines and primary samples. 12,13 In these studies we showed that HIF-1α mRNA and protein are constitutively present in MM cells and are further inducible by BM milieu stimuli (such as IL-6 and IGF-1) even in normoxic culture conditions. In MM cells, HIF-1α suppression induced a permanent cell cycle arrest by prolonging S-phase through cyclin A modulation and in addition it induced a mild apoptotic cell death.…”

“…7 In the past few years, a growing number of studies have provided valuable insight into the important role of HIF-1α in the pathophysiology of MM. [8][9][10][11][12][13] Treatments targeting both HIF-1α and hypoxic microenvironments represent novel strategies to improve treatment outcomes for MM.…”

“…12 Additionally, several transcription factors that play important roles in the pathophysiology of MM regulate HIF-1α expression and function. 46,47 Different studies have shown that nuclear factor κB (NFκB) regulates HIF-1α transcription.…”

“…In preclinical studies, blockage of HIF-1α activity via either RNA silencing or small molecules inhibitors resulted in effective antimyeloma activity and provides the rational for clinical validation of this novel target. 7,8,11,12,13,56 Abolishing expression of HIF-1α has been shown to be an effective way to inhibit tumor growth, inspiring the development of methods to target mRNA expression of HIF-1α as an alternative to targeting HIF-1α stability. An antisense oligonucleotide designed to inhibit HIF-1α expression has moved into clinical trials.…”