ELK4 and neoplasm: Notably, the protein level of the tumor hypoxia marker HIF1A in control xenograft tumors was higher than that in ELK4 knockdown xenograft tumors (Figure 2D), which could be due to the downregulation of HIF1A transcription by decreased expression of LRG1.[14, 15, 16] This reflected the decreased tumor growth of ELK4 knockdown xenograft tumors, which could be due to attenuated tumor angiogenesis.