Panoply™ Human FAS Knockdown Stable Cell Line

QKI-5 regulates the miR-196b-5p, which functions as an oncogenic microRNA in non-small cell lung cancer (NSCLC) by directly targeting GATA6 and TSPAN12. However, the role of miR-196b-5p in NSCLC progression and metastasis remains unclear. Here, researchers found that miR-196b-5p promoted lung cancer cell proliferation and clonogenicity by directly targeting the tumor suppressor gene FAS. In NSCLC tissue samples, FAS expression was significantly downregulated and negatively correlated with miR-196b-5p expression. Knockdown of FAS activated NFkB signaling and subsequent IL-6 secretion, leading to phosphorylation of signal transducer and activator of transcription 3 (STAT3), thereby promoting lung cancer cell growth. These findings suggest that miR-196b-5p may exhibit novel oncogenic functions in NSCLC through FAS-mediated STAT3 activation and indicate that targeting the miR-196b-5p/FAS/NFkB/IL6/STAT3 pathway may be a promising therapeutic strategy for the treatment of NSCLC.

Because both FAS and IL6 are closely linked to cancer pathogenesis and STAT3 activation, the researchers investigated IL6 mRNA and protein levels following FAS knockdown. Compared with control cells, IL6 mRNA and protein expression was significantly increased in FAS-knockdown A549 cells (Figures 1a and b). As expected, FAS knockdown in H520 cells significantly enhanced IL6 protein secretion compared with control cells. Based on these results, the researchers hypothesized that FAS knockdown might promote IL6 secretion in NSCLC cells. To test this hypothesis, cell proliferation and colony formation assays were performed using conditioned medium from FAS-knockdown and control cells. Compared with conditioned medium from control cells, conditioned medium from FAS-knockdown cells significantly enhanced cell proliferation and colony formation (Figure 1c). Interestingly, conditioned medium from FAS-knockdown cells significantly increased STAT3 phosphorylation (Figure 1d), suggesting that the increased IL6 expression caused by FAS knockdown is mediated by STAT3 activation in lung cancer cells. p65, a member of the NFkB family, is a well-known transcription factor that has been reported to enhance IL6 transcription by binding to the IL6 promoter region. Therefore, the researchers examined whether p65 was activated after FAS knockdown. Indeed, FAS knockdown promoted nuclear translocation of p65 protein compared to control cells, indicating that NFkB activation caused by FAS knockdown is the primary cause of the increased IL6 expression in lung cancer cells (Figure 1e).

Figure 1. FAS knockdown enhances IL6 expression. (Huang X, et al., 2020)