CCDC15 and cancer: Two cassette exon targets, CCDC15 (coiled-coil domain containing 15) exon 9 (CCDC15-ex9) and RELL2 (receptor expressed in lymphoid tissues-like 2) exon 3 (RELL2-ex3) are chosen as exemplary targets to decipher the interplay between editing enzymes and splicing machineries, and their biological importance in cancer.