The erbB3- and IGF-1 receptor-initiated signaling pathways exhibit distinct effects on lapatinib sensitivity against trastuzumab-resistant breast cancer cells

Abstract

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.

Targeting of HER3 with Functional Cooperative miRNAs Enhances Therapeutic Activity in HER2-Overexpressing Breast Cancer Cells

“…Protein expression levels were determined by western blot analysis as described previously [ 19 , 28 ]. Equal amounts of total cell lysates were boiled in Laemmli SDS-sample buffer, resolved by SDS-PAGE, transferred to nitrocellulose membrane (Bio-Rad Laboratories, Hercules, CA, USA), and probed with the primary antibodies described in the figure legends.…”

“…An apoptotic ELISA kit (Roche Diagnostics Corp.) was used to quantitatively measure cytoplasmic histone-associated DNA fragments (mononucleosomes and oligonucleosomes) as previously reported [ 19 , 23 ]. This enzyme immunoassay was performed according to the manufacturer’s instructions.…”

“…Especially in breast cancer, HER3 serves as a vital co-receptor of HER2, and its expression is a rate-limiting factor for HER2-induced breast cancer cell survival, proliferation, and progression [ 9 , 10 , 15 ]. We have shown that elevated expression of HER3 renders HER2-overexpressing breast cancer cells resistant to tamoxifen [ 17 ], HER2-targeted therapy (trastuzumab/Herceptin and lapatinib) [ 18 , 19 ], and the chemotherapeutic agent paclitaxel [ 20 ]. It is believed that inhibition of HER3 signaling is required to overcome drug resistance and effectively treat the breast cancer patients with HER2-overexpressing tumors.…”

Downregulation of the long noncoding RNA GAS5-AS1 contributes to tumor metastasis in non-small cell lung cancer

“…Protein expression was determined by western blots as previously described 44 45 46 . In brief, equal amounts of total cell lysates were boiled in SDS-sample buffer, resolved by SDS–PAGE, transferred onto nitrocellulose membrane (Bio-Rad Laboratories, Hercules, CA), and then incubated with the primary antibody.…”

MicroRNA-mediated epigenetic targeting of Survivin significantly enhances the antitumor activity of paclitaxel against non-small cell lung cancer

“…Clonogenic assays were performed as described previously [49, 50]. The colony was defined to consisting of at least 50 cells.…”