A recent study has shown that the expression of collagen XVIII (ColXVIII), a basement membrane component, is significantly upregulated in BC, and ColXVIII, as a regulator of epidermal growth factor receptor tyrosine kinase (ErbB) signaling, can interact with ErbB1 and ErbB2 (also known as EGFR and human epidermal growth factor receptor 2 [HER2]) and α 6-integrin forms complexes to promote BC cell proliferation, involving a cascade reaction of its N-terminus and MAPK/ERK1/2 and PI3K/AKT [171]. The gene discussed is PIK3CA; the disease is breast cancer.