Likewise, the expression of PTK2 mRNA was also significantly increased (Fig. 4H), whereas the expression of pre-mRNA decreased (Fig. 4J) in BC cell lines (MCF-7, MDA-MB-231, and BT-549) compared with that in MCF-10 A. What’s more, the expression level of PTK2 mRNA was negatively linearly correlated with that of circRPAP2 (Fig. 4K), whereas the expression level of PTK2 pre-mRNA was positively linearly correlated with that of circRPAP2 (Fig. 4L) in 102 BC tissue samples. Here, PTK2 is linked to breast cancer.