HIF-1 consists of two subunits, that is, α and β.18 HIF-1α subunit can be regulated by O concentration, and its expression is positively correlated with the degree of hypoxia.19,20 HIF-1α also plays a vital role in tumour metastasis, proliferation, and angiogenesis.21–23 The hypoxic state of solid tumours becomes serious as malignant tumours continue to grow, which increases HIF-1α expression. The gene discussed is HIF1A; the disease is cancer.