The erbB3- and IGF-1 receptor-initiated signaling pathways exhibit distinct effects on lapatinib sensitivity against trastuzumab-resistant breast cancer cells
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Hui Lyu1,2, Xiao He Yang3, Susan M. Edgerton2, Ann D. Thor2, Xiaoying Wu4, Zhimin He1, Bolin Liu1,2
1Cancer Research Institute and Affiliated Cancer Hospital, Guangzhou Medical University, Guangzhou, Guangdong, China
2Department of Pathology, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
3Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Kannapolis, NC, USA
4Department of Pathology, Xiangya Hospital, School of Basic Medical Science, Central South University, Changsha, China
Bolin Liu, e-mail: firstname.lastname@example.org
Keywords: ErbB3, IGF-1R, lapatinib, trastuzumab, resistance
Received: June 20, 2015 Accepted: November 16, 2015 Published: November 26, 2015
Both erbB3 and IGF-1 receptor (IGF-1R) have been shown to play an important role in trastuzumab resistance. However, it remains unclear whether erbB3- and IGF-1R-initiated signaling pathways possess distinct effects on the sensitivity of lapatinib, a dual tyrosine kinase inhibitor against both EGFR and erbB2, in trastuzumab-resistant breast cancer. Here, we show that the trastuzumab-resistant SKBR3-pool2 and BT474-HR20 breast cancer sublines, as compared the parental SKBR3 and BT474 cells, respectively, exhibit refractoriness to lapatinib. Knockdown of erbB3 inhibited Akt in SKBR3-pool2 and BT474-HR20 cells, significantly increased lapatinib efficacy, and dramatically re-sensitized the cells to lapatinib-induced apoptosis. In contrast, specific knockdown of IGF-1R did not alter the cells’ responsiveness to lapatinib. While the levels of phosphorylated Src (P-Src) were reduced upon IGF-1R downregulation, the P-Akt levels remained unchanged. Furthermore, a specific inhibitor of Akt, but not Src, significantly enhanced lapatinib-mediated anti-proliferative/anti-survival effects on SKBR3-pool2 and BT474-HR20 cells. These data indicate that erbB3 signaling is critical for both trastuzumab and lapatinib resistances mainly through the PI-3K/Akt pathway, whereas IGF-1R-initiated Src activation results in trastuzumab resistance without affecting lapatinib sensitivity. Our findings may facilitate the development of precision therapeutic regimens for erbB2-positive breast cancer patients who become resistant to erbB2-targeted therapy.
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