ERBB2 and breast cancer: PMCA2 levels were, however, significantly enriched in the Basal molecular phenotype compared to HER2, Luminal A and Luminal B. Assessment of PMCA2 levels in Basal breast cancer cell lines identified PMCA2 as the minor isoform at the mRNA level in all basal breast cancer cell lines, with a trend for cell lines with higher levels of PMCA2 to be identified as Basal B (Fig. 3A).