Because Parkin negatively regulates HIF-1α, the expression levels of Parkin and HIF-1α are inversely correlated in human breast cancer tissues, and lower Parkin expression is correlated with poor metastasis-free survival in breast cancer patients38; as shown in the present study, a similar relationship holds for Parkin and BRCA1 (Fig. 4). This evidence concerns the gene PRKN and breast cancer.