Heterotrimerization of the Growth Factor Receptors erbB2, erbB3, and Insulin-like Growth Factor-I Receptor in Breast Cancer Cells Resistant to Herceptin

Abstract

Primary and acquired resistance to the breast cancer drug trastuzumab (Herceptin) is a significant clinical problem. Here, we report enhanced activation of downstream signaling pathways emanating from the growth factor receptors erbB2, erbB3, and insulin-like growth factor-I receptor (IGF-IR) in trastuzumab-resistant breast cancer cells. Interactions between IGF-IR and erbB2 or erbB3 occur exclusively in trastuzumab-resistant cells, where enhanced erbB2-erbB3 interactions are also observed. Moreover, these three receptors form a heterotrimeric complex in resistant cells. erbB3 or IGF-IR knockdown by short hairpin RNA-mediated strategies upregulates p27 kip1 , inactivates downstream receptor signaling, and resensitizes resistant cells to trastuzumab. Our findings reveal a heterotrimer complex with a key role in trastuzumab resistance. On the basis of our results, we propose that trastuzumab resistance in breast cancer might be overcome by therapeutic strategies that jointly target erbB3, erbB2, and IGF-IR.

Elevated expression of erbB3 confers paclitaxel resistance in erbB2-overexpressing breast cancer cells via upregulation of Survivin

“…Thus, it will be very interesting to explore whether elevated expression of erbB3 may modulate certain miRNAs that specifically target Survivin mRNA in erbB2-overexpressing breast cancer cells. As the interactions of EGFR and IGF-1R induce Survivin expression and counteract erlotinib's antitumor activity in non-small cell lung carcinoma (Morgillo et al, 2006), we are currently testing whether the heterotrimerization of erbB3/erbB2/IGF-1R, which we have observed in Herceptin-resistant breast cancer cells (Huang et al, 2010), may also regulate Survivin expression. Such studies may shed new lights on identifying Survivin as a molecular linker of cross-resistance to paclitaxel and Herceptin treatment of breast cancer patients whose tumors overexpress erbB2.…”

“…Lentiviral production was carried out as described previously (Huang et al, , 2010. In brief, the lentiviral expression vector pLKO.1-ConshRNA or pLKO.1-SurshRNA and lentivirus packaging plasmids pCMV-VSVG and pCMV-DA.9…”

“…The CellTiter96 AQ non-radioactive cell proliferation kit (Thermo Fisher Scientific, Waltham, MA, USA) was used to determine cell viability (Huang et al, , 2010. In brief, cells were plated onto 96-well plates with complete medium for 24 h. Cells were then grown in either control medium or the same medium containing a series of doses of paclitaxel for another 72 h. After reading all wells at 490 nm with a micro-plate reader, the percentages of surviving cells from each group relative to controls, defined as 100%, were determined by reduction of MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium,inner salt).…”

“…Immunoprecipitation and western blot assays were performed as described (Huang et al, 2010). Briefly, equal amounts of cell lysates were incubated with specific antibody for 2 h at 4 1C, followed by incubation with protein A-agarose or protein G-agarose (Roche) at 4 1C overnight.…”

Superior Antitumor Activity of a Novel Bispecific Antibody Cotargeting Human Epidermal Growth Factor Receptor 2 and Type I Insulin-like Growth Factor Receptor

“…Various mechanisms may account for this resistance, which likely involve the PI3K/Akt pathway, including elevated HER2-associated receptors and other receptors (28,29), cross activation between HER2 and other receptors (30)(31)(32), blockage of trastuzumab by membrane-associated glycoproteins such as mucin-4, removal of the trastuzumab epitope by cleavage or loss of HER2 expression, and increased HER2 expression. Accumulating evidence shows that cross-talk between HER2 and IGF-IR, including receptor heterodimerization and transactivation, and elevated IGF-IR signaling are associated with trastuzumab resistance (31,(33)(34)(35). Overexpression of IGF-IR in HER2-overexpressing breast cancer cell lines results in trastuzumab resistance in vitro (36).…”