SPP1 and hepatocellular carcinoma: Considering transcription factors including AP-1, Sp-1, v-Src, Runx and Tcf-4 participating in the transcription regulation of OPN in other types of cancers [20,29], and transcription factor along with co-activators or co-repressors strategically binding to specific sites of target gene promoters [30], it is possible that c-Myb interacts with other transcription factors to modulate the OPN expression in HCC cells.