The investigation of possible associations between the mRNA expression of PHD genes in primary tumours showed that PHD1 and PHD2 mRNA expression was positively correlated (rs = 0.82; p < 0.0001), whereas we did not observe any association between PHD1 and PHD3 (rs = 0.10; p = 0.428) or PHD2 and PHD3 (rs = 0.21; p = 0.112) mRNA expression (Figure 2). Here, PDC is linked to neoplasm.