Clinical correlations between CLK3, p-USP13–Y708, c-Myc, and ATIC in CCA patients’ samples.(A) The pictures show CLK3, p-USP13–Y708, c-Myc, and ATIC protein expression in two human CCA specimens. Bars, 100 µm. (B) Pearson correlation coefficient analysis about the expression of CLK3, p-USP13–Y708, c-Myc, and ATIC protein in patients with CCA (n = 103) by IHC. ***, P < 0.001. (C) OS data from CCA patients stratified by the level of CLK3 with p-USP13–Y708 or c-Myc. ***, P < 0.001; Kaplan-Meier analysis. (D) EGF or TGFβ1 or human CCA-associated CLK3 mutant activates CLK3 and thereby enhances p-Y708 levels of USP13; this event significantly increases the association of USP13 with c-Myc and disrupts Fbxl14-mediated c-Myc ubiquitination, which activated the de novo purine biosynthesis pathway and promoted the development of CCA. Interestingly, activated c-Myc transcriptionally up-regulated CLK3 expression. Finally, tacrine hydrochloride inhibits aberrant CLK3-induced CCA. H, high; L, low.