CLSTN1 and breast cancer: Here, we found that splicing of exon 11 in Calsyntenin 1 (CLSTN1) negatively correlated with TLN1 exon 17b splicing in lung and breast cancer patients and cell lines (Fig. S1 D and Fig. S2 A), suggesting that these two splice events might be “trans-mutually exclusive.” This exclusivity was also reflected by RT-PCR analysis of breast cancer cell lines where cell lines with TLN1 exon 17b inclusion exhibited CLSTN1 exon 11 skipping and vice versa (Fig. S1 D and Fig. S2 B).