Wnt/β-catenin pathway
Wnt pathway in essence comprises of canonical (β-catenin dependent) and noncanonical (β-catenin-independent) signaling pathway. Here, we focus on canonical pathway which is found to be implicated in survival of most of the CSCs. In canonical Wnt signaling pathway, in the absence of Wnt ligands (Wnt3a and Wnt1), β-catenin is phosphorylated due to its interaction with the destruction complex, which consists of the scaffold protein Axin, APC and GSK3β kinase and casein kinase (CK1α). This phosphorylation brings about ubiquitination and degradation of β-catenin. On the other hand, the pathway is activated when Wnt ligands bind to Frizzled (Fzd) receptors and/or the low-density lipoprotein-related protein (LRP) co-receptors. As a result, Dishevelled (Dvl) proteins are recruited and Dvl polymers inactivate the destruction complex. This results in stabilization and accumulation of β-catenin which then translocates into the nucleus, binds to lymphoid enhancer factor (LEF)/T-cell factor (TCF) transcription factors, and facilitates transcription of various target genes (Zhan et al., 2017) .