CD274 and breast carcinoma: We screened a series of cell lines with established positive or negative PD-L1 protein status by flow cytometry and western blot analysis, including lymphomas [HDLM-2(+) and OC1-LY1(−)] [12], renal cell carcinoma [Caki-2(+), UMRC6(−)] [23], and breast cancer cell lines [MDA231(+), SKBR3(+), and BT474(-)] [28] to determine whether the secPD-L1 variant mRNA expression was associated with expression of the full-length PD-L1 by RT-PCR analysis.