CDKN2B-AS1 and melanoma: When we compared these data to circANRIL isoforms from both of our examined melanoma cell lines, we noted that the pairing of inverted Alu elements and the length of introns were not the only determining factors causing circularization of ANRIL. Alu repetitive sequences were present in introns 1, 5, 6, 7, 11, 12 and 14 of ANRIL (Figure 3A).