More importantly, they are remarkably related to the pathogenesis of NHL as previously reported. However, the e pression of CyclinD1 and BCL 6 did not show a predicted correlation with ISL 1 in NHL cells. Therefore, we focused on c Myc in the rest investigations. Western blot results showed that the basal e pression level of c Myc was positively correlated with the e pression level of ISL 1 in NHL cell lines. Moreover, further results indicated that the overe pression of ISL 1 increased the e pression of c Myc at both mRNA and protein levels in Raji cells. Whereas, the significant decrease of c Myc e pression was associated with the knockdown of ISL 1 as compared with those in the control Ly3 cells. These results show that ISL 1 could act as a transcriptional activator of c Myc.

Furthermore, we uncovered that c Myc is a direct tran scriptional target of ISL 1. Bioinformatic analysis revealed a conserved ISL 1 binding site at ?1856 ?1852 bp upstream of the ATG translation start site on the c Myc enhancer region. Luciferase assay with c Myc luc showed the stimulated c Myc luc activity in ISL 1 overe pressing cells in a dose dependent manner, whereas a significant decrease of c Myc luc activity was seen in ISL 1 knockdown cells. The constructs containing the mutant or de leted ISL 1 binding site on the c Myc enhancer, c Myc luc M1, c Myc luc M2, c Myc luc D1 and c Myc luc D2, e hibited a significant decrease of luciferase activity compared to the wild type c Myc luc.

To determine if ISL 1 could occupy the c Myc enhancer region in vivo, a specific primer covering the potential ISL 1 binding site located between ?1935 and ?1744 bp of c Myc enhancer were designed and used for chromatin immunoprecipitation assay in Ly3 cells. As shown in Figure 5F, Dacomitinib ISL 1 was recruited to the c Myc enhancer about four folds as compared with IgG, suggesting that ISL 1 could bind on the c Myc enhancer in vivo. These results indicate that ISL 1 is a direct regulator of c Myc transcription in NHL cells. Taken together, ISL 1 promotes NHL cells proliferation possibly via the activation of the c Myc enhancer and thus increasing its e pression. p c Jun and p STAT3 contribute to the up regulation of ISL 1 e pression in NHL cells To e plore the molecular regulatory mechanism for ISL 1 up regulation, bioinformatic analysis was used to identify the potential regulatory factors that could bind on the transcriptional regulatory region of ISL 1. Relevant con served binding sites of symbolic transcriptional factors, specifically pointing to major pathways such as WNT, MAPK ERK, p38 MAPK, SAPK JNK and JAK STAT, were identified on the ISL 1 transcriptional regulatory region.