HIF1A and neoplasm: The antitumor effects of metronomic chemotherapy can be achieved through several mechanisms, including inhibition of angiogenesis and vasculogenesis, blockade of circulating endothelial progenitor cells (CEPs) [3], suppression of HIF-1α expression [4, 5] and, depending on the administered drug and tumor cells being treated, cytotoxic action on tumor cells and stimulation of the immune system [6].