ERBB2 and breast cancer: In contrast, palbociclib had a minimal effect on gPD-L1 in the TNBC cell line, MDA-MB-468, and the trastuzumab-resistant HER2+ breast cancer cell line, JIMT1, whereas in the HER2-enriched cell line, HCC1954, gPD-L1 was slightly induced (Supplementary Fig. S5B).