PIK3CA and breast cancer: In addition to the results of five significantly altered genes (ARID1A, CCNE1, EZH2, FBXW7, and TSC2) identified in the present study, Figure 2 also shows the sequencing results of paired samples for the other nine mutated genes (CDK4, CDK6, CDKN2A, FGFR1, FGFR2, FGFR3, PIK3CA, PTEN, and RB1) which were associated with resistance to CDK4/6 inhibitors in previous clinical or preclinical studies of breast cancer [11,25,26,27].