SPF45 was identified to be a cellular target of CLK1 in ovarian cancer.46,115 (LC)-electrospray ionization-tandem mass spectrometry (MS/MS) experiments showed that CLK1 is able to phosphorylate SPF45 at eight serine residues (Ser 48, 62, 202, 204, 222, 266, 288, and 291).46 Furthermore, CLK1 overexpression increased SPF45 protein levels and promoted SPF45-induced exon 6 exclusion of Fas mRNA in SKOV3 breast cancer cells. The gene discussed is CLK1; the disease is breast cancer.