We discovered a positive feedback loop, in which the activation of p38 and AKT downstream from the altered FGFR3 upregulates <i>MYC</i> mRNA levels and stabilizes MYC protein, respectively, leading to the accumulation of MYC, which directly upregulates <i>FGFR3</i> expression by binding to active enhancers upstream from <i>FGFR3</i> Disruption of this FGFR3/MYC loop in bladder cancer cell lines by treatment with FGFR3, p38, AKT, or BET bromodomain inhibitors (JQ1) preventing <i>MYC</i> transcription decreased cell viability <i>in vitro</i> and tumor growth <i>in vivo</i> A relevance of this loop to human bladder tumors was supported by the positive correlation between <i>FGFR3</i> and <i>MYC</i> levels in tumors bearing <i>FGFR3</i> mutations, and the decrease in FGFR3 and MYC levels following anti-FGFR treatment in a PDX model bearing an <i>FGFR3</i> mutation.
Signaling mediated by p38 and JNK has well-established importance in cancer, yet the contribution of this pathway in urothelial bladder cancer is not understood.
The present study suggests that VEGF-C can enhance the proliferation and invasiveness of bladder cancer T24 cells, which is due to suppression of apoptosis and facilitation of migration, accompanied with upregulation of p38 MAPK and Akt phosphorylation.
In examining the role and function of ALKBH8 in human bladder cancer development in vitro, we found that silencing of ALKBH8 through small interfering RNA transfection reduced reactive oxygen species (ROS) production via down-regulation of NAD(P)H oxidase-1 (NOX-1) and induced apoptosis through subsequent activation of c-jun NH(2)-terminal kinase (JNK) and p38.