Lapatinib: an oral dual tyrosine kinase inhibitor for HER-2-positive breast cancer

Recent Advancements in the Development of Anti-Breast Cancer Synthetic Small Molecules

Among all cancer types, breast cancer (BC) still stands as one of the most serious diseases responsible for a large number of cancer-associated deaths among women worldwide, and diagnosed cases are increasing year by year worldwide. For a very long time, hormonal therapy, surgery, chemotherapy, and radiotherapy were used for breast cancer treatment. However, these treatment approaches are becoming progressively futile because of multidrug resistance and serious side effects. Consequently, there is a pressing demand to develop more efficient and safer agents that can fight breast cancer belligerence and inhibit cancer cell proliferation, invasion and metastasis. Currently, there is an avalanche of newly designed and synthesized molecular entities targeting multiple types of breast cancer. This review highlights several important synthesized compounds with promising anti-BC activity that are categorized according to their chemical structures.

Cytotoxic Effects of the Dual ErbB Tyrosine Kinase Inhibitor, Lapatinib, on Walker 256 Rat Breast Tumour and IEC-6 Rat Normal Small Intestinal Cell Lines

Lapatinib is an orally administered, dual ErbB1/ErbB2 tyrosine kinase inhibitor (TKI). It is effective in ErbB2 + ve breast cancer treatment. However, lapatinib is associated with diarrhoea with an incidence of 47–75%. The mechanism of ErbB1 TKI-induced diarrhoea remains unclear. ErbB1 or epidermal growth factor receptor (EGFR) is expressed in gastrointestinal mucosa whereby the primary site for drug absorption is intestine. Thus, administration of ErbB1 oral TKI may disrupt gut homeostasis, leading to diarrhoea. Nevertheless, further investigations are required. We observed that lapatinib inhibited 50% Walker 256 breast tumour cells and IEC-6 small intestinal cell growth. Higher percentage of necrosis was observed in lapatinib-treated Walker 256. Lapatinib-treated IEC-6 showed higher percentage of late apoptosis. Only ErbB2 mRNA was detected in Walker 256 but both ErbB1 and ErbB2 mRNAs were detected in IEC-6, yet both protein staining were detected in both cells. Lapatinib exhibited cytotoxic properties on ErbB1/ErbB2 expressing cell lines, with intestinal cells being more sensitive to lapatinib compared to tumour cells. Lapatinib induced necrosis in tumour cells, while inducing late apoptosis in intestinal cells may explain lapatinib-induced diarrhoea in patients administered with the drug which could be due to apoptosis of intestinal epithelial cells leading to barrier disruption and consequently diarrhoea.