A trastuzumab-tolerant breast cancer model was constructed by knocking out the PTEN gene in HER2 overexpressing breast cancer cell lines to simulate the environment of long-term trastuzumab administration, demonstrating upregulation of proinflammatory factor expression in the context of PTEN deletion and eventual expansion of the CSCs population through the IL-6 inflammatory loop [124]. Here, ERBB2 is linked to breast cancer.