EPO and neoplasm: Importantly, as the knockdown of HIF-1α dismissed the growth of colon cancer cells in mice, the knockdown of HIF-1α was able to block ZFP91-triggered growth rate increase of colon cancer cells in mice (Figure 5A–5D) and the mean expression levels of HIF-1α, VEGF and EPO protein and mRNA levels in each group of tumor tissue samples from mice (Figure 5E and 5F) were correlated well with the tumor volume of corresponding animal group.