EGLN2 and breast carcinoma: Although, endogenous PHD1 levels are difficult to detect in cell lines other than breast cancer lines (Moser et al., 2013; Zheng et al., 2014), we used an immunofluorescence approach in U2OS cells to determine whether the antibody against phospho-S130 PHD1 was able to detect endogenous protein (Fig. 1F).