CD9 and cancer: Interestingly, 31 (25%) of the 124 highly expressed isoforms correspond to 18 genes currently under active investigation as drug targets for numerous cancers (specifically ABCG2 [37], ADAM10 [38], ALCAM [39], [40], BSG [41], CD151 [42], CD44 [43], CD47 [44], [45], CD9 [46]–[50], CEACAM5 [51], [52], CEACAM6 [52], CXCR4 [53], EPCAM [54], ERBB2 [55], ICAM1 [56], IGF1R [57], NRP1 [58], NT5E [59], TRPM7 [60].