Inactivation of ErbB3 by siRNA promotes apoptosis and attenuates growth and invasiveness of human lung adenocarcinoma cell line A549

Abstract

The ErbB3 receptor and the downstream signaling kinase Akt are implicated in proliferation of lung adenocarcinoma cells. Inhibition by siRNAs to ErbB3 and Akt isoforms 1, 2 and 3 was utilized to investigate the contribution of these molecules to tumor survival, spreading and invasiveness, and the roles of specific Akt isoforms. ErbB3 siRNA stably and dose-dependently suppressed ErbB3 protein for 2 days or more, and reduced cell numbers, by both suppressing cell cycle and causing apoptosis and necrosis. It also inhibited soft agar growth, cell motility and migration, and invasiveness. Akt1, 2 and 3 siRNAs had similar suppressive effects on cell number, apoptosis/ necrosis and soft agar growth. However, although Akt1 siRNA had no effect on cell migration or invasion, Akt2 siRNA effectively suppressed both activities, and Akt3 siRNA had moderate effectiveness. In A549 cells, ErbB3 is indicated as having major effects on cell division, survival, motility, migration and invasiveness. All three Akt isoforms are to varying degrees involved in these cell behaviors, with Akt2 especially implicated in migration and invasion. ErbB3 and the Akts are promising targets for therapy, and siRNAs may be useful for this purpose.

The ERBB3 receptor in cancer and cancer gene therapy

“…ERBB3/PI3K/AKT-induced survival and proliferation pathways have been implicated in the malignancy of breast, ovarian, colon, gastric and lung cancer cells. Various approaches using ERBB3 mutants, 136,138 immunoprecipitations with antibody against ERBB3 139,140 or NRG, 141 ERBB3 antisense, 139 ERBB3 small interfering RNA (siRNA), 142 and use of the designer ERBB3 transcription inhibitor E3 in a variety of cells 143 have established the importance of this pathway. GRB7/GRB2-GRB7 was notable for its uniquely high-affinity binding with pY1197 in ERBB3 (Table 3).…”

Downregulation of HER3 by a Novel Antisense Oligonucleotide, EZN-3920, Improves the Antitumor Activity of EGFR and HER2 Tyrosine Kinase Inhibitors in Animal Models

“…Consistent with this, reduced HER3 expression by conditional knockout or LNA-based antisense molecule, designated as EZN-3920, in a polyoma-T model of breast cancer inhibits PI3K activation and tumor formation in this genetically engineered mouse model (21). In addition, siRNA and short hairpin RNA (shRNA)-directed downmodulation of HER3 resulted in tumor growth inhibition in lung adenocarcinoma (22) and decreased disease progression as well as prolonged survival in xenograft mouse models of ovarian cancer (13) or of HER2-overexpressing breast cancer (5). Furthermore, a recent study showed the sensitivity of a subset of head and neck cancers to HER2 kinase inhibitor is dependent on the co-expression of HER3 and its ligand neuregulin-1 (14).…”

“…Furthermore, a recent study showed the sensitivity of a subset of head and neck cancers to HER2 kinase inhibitor is dependent on the co-expression of HER3 and its ligand neuregulin-1 (14). In vitro, targeting HER3 using siRNAs and antisense deoxyoligonucleotides (AS-ODNs) potently inhibits proliferation and promotes apoptosis in cells sensitive and insensitive to EGFR and HER2 inhibitors (5,13,17,22,23). Finally, a monoclonal antibody to HER3 inhibited tumor growth, especially in cell lines that secrete heregulin, a ligand for HER3 (12).…”

The Akt isoforms, their unique functions and potential as anticancer therapeutic targets

“…Similarly, the ablation of Akt2 in lung adenocarcinoma cells with siRNA resulted in a decrease in both cell migration and invasion. By contrast, the downregulation of Akt1 with siRNA did not show a notable effect on lung cancer cells (101). Interestingly, cell migration and invasion were partially inhibited by Akt3 ablation; however, the degree of inhibition was much lower than that caused by Akt2 ablation (101).…”