Hypoxia-Inducible Factor-1α, a Novel Molecular Target for a 2-Aminopyrrole Derivative: Biological and Molecular...

Background: Hypoxia-inducible factor-1α (HIF-1α) is a well-known transcriptional regulator that mediates a broad spectrum of cellular responses to hypoxia, including angiogenesis, extracellular matrix remodeling, and metabolic reprogramming. These activities can be achieved by upregulation of numerous genes, such as vascular endothelial growth factors, fibroblast growth factors, and platelet-derived growth factors, which are involved in the growth regulation of normal tissues and solid tumors. Notably, HIF-1α-mediated regulation of the solid tumor's microenvironment effectively modulates tumor sensitivity to anticancer therapies and thereby can contribute to disease progression. Methods: The study was performed on breast, lung and prostate cancer cell lines. Protein expression was examined by western blotting. Antitumor activity of 2-ANPC was measured by syngeneic 4T1 breast cancer mouse model. Results: We show here that a 2-aminopyrrole derivative (2-amino-1-benzamido-5-(2-(naphthalene-2-yl)-2-oxoethylidene)-4-oxo-4,5-dihydro-1-H-pyrrole-3-carboxamide-2-ANPC), previously shown as a potent microtubule-targeting agent, effectively downregulates HIF-1α expression in a broad spectrum of cancer cell lines, including breast, lung, and prostate cancer. The downregulation of HIF-1α expression in 2-ANPC-treated cancer cells was due to enhanced proteasome-mediated degradation, whereas the proteasome inhibitor MG-132 effectively reversed this downregulation. 2-ANPC's potency in downregulating HIF-1α was also shown in vivo by using the 4T1 breast cancer syngraft model. Importantly, this 2-aminopyrrole derivative also downregulated the expression of vascular endothelial growth factor receptors 1 and 3 (VEGFR1 and 3) in 4T1 tumors, which correlated with decreased tumor weight and size. As expected, an increase in apoptotic (i.e., cleaved caspase-3-positive) cells was detected in 4T1 tumors treated with 2-aminopyrrole derivative. Lastly, using various computational tools, we identified four potential binding sites for 2-ANPC to interact with HIF-1α, HIF-1β, and the p300 complex. Conclusions: Collectively, we show here, for the first time, that HIF-1α is a novel molecular target for the 2-aminopyrrole derivative (2-ANPC), thereby illustrating it as a potential scaffold for the development of potent chemotherapeutic agents with anti-angiogenic activity.