P4HA1 encodes a component of prolyl 4-hydroxylase, a key enzyme in collagen synthesis; it was shown to be an activator of the HIF-1 pathway in breast cancer and biomarker of poor prognosis in various types of cancers including melanomas49, pancreatic cancer50 and head and neck squamous cell carcinomas51. This evidence concerns the gene P4HA1 and breast cancer.