HECTD4 and breast carcinoma: To further validate the inverse correlation between HECTD4 and COX-2 proteins, we analyzed a previously published proteomic dataset from 21 different human breast cancer cell lines (19), which confirmed the negative correlation between HECTD4 and COX-2 protein levels (N = 21, r = −0.426, P = 0.0541; SI Appendix, Fig. S4J).