Requirement of hypoxia-inducible factor-1α down-regulation in mediating the antitumor activity of the anti–epidermal growth factor receptor monoclonal antibody cetuximab

Abstract

We tested our novel hypothesis that down-regulation of hypoxia-inducible factor-1A (HIF-1A), the regulated subunit of HIF-1 transcription factor that controls gene expression involved in key functional properties of cancer cells (including metabolism, survival, proliferation, invasion, angiogenesis, and metastasis), contributes to a major antitumor mechanism of cetuximab, an approved therapeutic monoclonal antibody that blocks activation of the epidermal growth factor receptor. We showed that cetuximab treatment down-regulates HIF-1A levels by inhibiting synthesis of HIF-1A rather than by enhancing degradation of the protein. Inhibition of HIF-1A protein synthesis was dependent on effective inhibition of the phosphoinositide-3 kinase (PI3K)/Akt pathway by cetuximab, because the inhibition was prevented in cells transfected with a constitutively active PI3K or a constitutively active Akt but not in cells with a constitutively active MEK. Overexpression of HIF-1A conferred cellular resistance to cetuximab-induced apoptosis and inhibition of vascular endothelial growth factor production in sensitive cancer cell models, and expression knockdown of HIF-1A by RNA interference substantially restored cellular sensitivity to the cetuximab-mediated antitumor activities in experimental resistant cell models created by transfection of an oncogenic Ras gene (G12V) or by concurrent treatment of the cells with insulin-like growth factor-I. In summary, our data show that cetuximab decreases HIF-1A protein synthesis through inhibition of a PI3K-dependent pathway and that an effective down-regulation of HIF-1A is required for maximal therapeutic effects of cetuximab in cancer cells.

Interferon/STAT1 and neuregulin signaling pathways are exploratory biomarkers of cetuximab (Erbitux�) efficacy in KRAS wild-type squamous carcinomas: A pathway-based analysis of whole human-genome microarray data from cetuximab-adapted tumor cell-line models

“…We established pre-clinical models of EGFR-positive A431 vulvar squamous carcinoma cells chronically adapted to grow in the continuous presence of cetuximab. A431 epidermoid carcinoma cells were chosen based on three primary criteria: a) these EGFR-overexpressing cells are exquisitely sensitive to cetuximab; b) A431 cells has not either EGFR tyrosine kinase domain or KRAS mutations, and c) apoptotic cell death is usually weak or sometimes not observed after cetuximab treatment (i.e., cetuximab-induced EGFR down-regulation effectively abrogates mitogenic signals from autocrine or paracrine growth factors, thus resulting in arrest of cell cycle progression but nor active cell killing) (18)(19)(20). In this scenario, we aimed to minimize the detection of gene expression changes related to general alterations in the apoptotic cell machinery among the transcriptional events induced by chronic cetuximab-induced EGFR inhibition.…”

The impact of Survivin, WRAP53β, and Hypoxia on treatment response in Head and Neck Cancer

“…However, a similar pattern was found for LK0412 which becomes more sensitive to cetuximab in hypoxia, emphasizing our assumption that other mechanisms to hypoxia-related resistance to cetuximab have to be considered, e.g. tumorspecific mutations within the K-ras gene (88).…”

“…However, the role of HIF-1α in their observations was not tested. As HIF-1α overexpression has been correlated with poor prognosis and outcome, the combination of drugs targeting HIF-1α and cetuximab has been suggested in order to gain maximal therapeutic effect (88). Thus, it appears crucial to identify patients whose tumors become more sensitive in the presence of HIF-1α, as anti-HIF-1α therapeutics may actually worsen the treatment response to cetuximab and potentially the patient's outcome.…”

“…Interestingly, HIF-1α depletion revoked the inactivation of Akt induced by cetuximab in hypoxia, suggesting that the suspected sensitizing effect of HIF-1α that we have observed might be related to this EGFR downstream molecule. Li et al showed that inhibition of PI3K by cetuximab is imperative for downregulation of HIF-1α synthesis, and that this downregulation is required for maximum effect of cetuximab (88). It would be interesting to see how PI3K is affected in the LK0412 cell line, to see if an explanation for its sensitization to cetuximab can be found.…”

Cetuximab enhances the effect of oxaliplatin on hypoxic gastric cancer cell lines

“…Cetuximab (C225, Erbitux) is a chimeric monoclonal antibody directed to the extracellular domain of EGFR. Numerous studies have shown that cetuximab inhibited the production of vascular endothelial growth factor (VEGF) in vitro and in vivo by inhibiting HIF-1· expression levels (24)(25)(26)(27)(28).…”