CLK1 (CDC-like kinase 1) is a dual-specificity kinase that phosphorylates both serine/threonine and tyrosine residues on target proteins. Its primary function involves regulating RNA splicing through phosphorylation of SR (serine/arginine-rich) proteins in the spliceosomal complex, including SRSF1, SRSF3, and PTPN1 12. CLK1 also regulates alternative splicing of tissue factor (F3) pre-mRNA in endothelial cells 2. Beyond splicing, CLK1 activates the Hippo-YAP signaling pathway through a WWC2-mediated mechanism 3. In pancreatic cancer, CLK1 phosphorylates SRSF5 to drive aberrant exon skipping of METTL14 and Cyclin L2, promoting proliferation and metastasis while regulating m6A methylation 4. CLK1 is significantly elevated in multiple cancers including intrahepatic cholangiocarcinoma, pancreatic cancer, and osteosarcoma, correlating with poor prognosis and enhanced tumor growth 345. High CLK1 expression promotes cancer cell proliferation and migration while facilitating resistance to conventional therapies 65. These findings identify CLK1 as an oncogenic driver across multiple cancer types, suggesting CLK1 and downstream pathways (YAP, SRSF5) represent promising therapeutic targets for cancer treatment.