Final answer:
Over-expression of HER2 by breast cancer cells results in enhanced cell proliferation. Lapatinib, a drug for breast cancer, inhibits the autophosphorylation of HER2, thereby also affecting dimerization and the downstream cellular response, ultimately reducing tumor growth.
Step-by-step explanation:
The effect that occurs due to over-expression of Human EGF Receptor 2 (HER2) by breast cancer cells is enhanced cell proliferation. This is because HER2 is a receptor tyrosine kinase that plays a key role in the growth and division of cells. In approximately 20-30 percent of human breast cancer cases, HER2 is overexpressed, which results in unregulated cell division and contributes to the development of breast cancer.
Lapatinib is a drug that has been used to treat breast cancer by inhibiting the autophosphorylation of HER2, thereby reducing tumor growth by 50 percent. Consequently, besides autophosphorylation, Lapatinib would inhibit dimerization and the downstream cellular response. As HER2 is involved in signal transduction pathways that promote growth and division of cells, inhibiting these processes helps in controlling tumor proliferation.