Noman et al. previously confirmed that HIF-1α could regulate both the mRNA and protein expression of PD-L1 by directly acting on hypoxia response element 4 (HRE-4) in the proximal promoter of PD-L1 in tumour models [30]; it was shown that inhibition of HIF-1α activity under hypoxic conditions significantly decreased PD-L1 mRNA and protein levels. The gene discussed is HIF1A; the disease is neoplasm.