CD274 and breast cancer: Moreover, in a panel of breast cancer cell lines that contained five TNBC cell lines (MDA-MB-231, HCC1937, BT20, HCC1806, and HS578T) and three non-TNBC cell lines (MCF-7, T47D and SKBR3), PD-L1 was found to have higher protein and mRNA levels in TNBC cell lines (Fig. 1e, f).