ATP2B1 and breast cancer: This proposal is supported by prior studies in which PMCA1/PMCA4 inhibition using specific small molecules was shown to impair calcium extrusion, sensitize breast cancer cells to apoptosis, and reduce tumor cell viability [50,51]; these findings highlight PMCA as a promising therapeutic target, and their inhibition may serve as a viable strategy to overcome calcium-dependent lapatinib resistance in HER2+ breast cancer; however, further research is needed to validate their efficacy.