Silencing of the HER2/neu Gene by siRNA Inhibits Proliferation and Induces Apoptosis in HER2/neu-Overexpressing Breast Cancer Cells

Abstract

In eukaryotes, double-stranded (ds) RNA induces sequence-specific inhibition of gene expression referred to as RNA interference (RNAi). We exploited RNAi to define the role of HER2/neu in the neoplastic proliferation of human breast cancer cells. We transfected SK-BR-3, BT-474, MCF-7, and MDA-MB-468 breast cancer cells with short interfering RNA (siRNA) targeted against human HER2/neu and analyzed the specific inhibition of HER2/neu expression by Northern and Western blots. Transfection with HER2/neu-specific siRNA resulted in a sequence-specific decrease in HER2/neu mRNA and protein levels. Moreover, transfection with HER2/neu siRNA caused cell cycle arrest at G0/G1 in the breast cancer cell lines SK-BR-3 and BT-474, consistent with a powerful RNA silencing effect. siRNA treatment resulted in an antiproliferative and apoptotic response in cells overexpressing HER2/neu, but had no influence in cells with almost no expression of HER2/neu proteins like MDA-MB-468 cells. These data indicate that HER2/neu function is essential for the proliferation of HER2/neu-overexpressing breast cancer cells. Our observations suggest that siRNA targeted against human HER2/neu may be valuable tools as antiproliferative agents that display activity against neoplastic cells at very low doses.

Targeting the function of the HER2 oncogene in human cancer therapeutics

“…Experimental models of HER2-overexpressing cancer cells using antisense, ribozyme or short interfering RNA (siRNA) methodologies consistently show that HER2 knockdown induces apoptosis in cell culture, or tumor regression in vivo, in the absence of HER2 expression, while tumor types that do not overexpress HER2 are not sensitive to HER2 knockdown (Colomer et al, 1994;Juhl et al, 1997;Roh et al, 2000;Choudhury et al, 2004;Faltus et al, 2004). Similar results are seen with kinase-dead HER2 and intracellular single-chain anti-HER2 antibodies (Beerli et al, 1994;Messerle et al, 1994;Deshane et al, 1996).…”

Protein 4.1B expression is induced in mammary epithelial cells during pregnancy and regulates their proliferation

“…Note that pRb hyperphosphorylation and cyclin A levels were decreased in cells induced to overexpress DAL-1 (a), while no change was seen in cyclin D (a), phospho-Akt, Akt, phospho-p44/42, p44/42 (b), phospho-JNK or total JNK levels (c) in DAL-1-overexpressing cells 4.1B regulates mammary epithelial proliferation R Kuns et al with erbB2 and EGFR in mammary carcinoma cells (Wobus et al, 2002;Ghatak et al, 2005) and with 4.1 proteins through its C-terminal domain (Ponta et al, 2003). As loss of erbB2 expression or activity can inhibit proliferation of mammary carcinoma cells (JhabvalaRomero et al, 2003;Faltus et al, 2004;Chu et al, 2005), including the MCF-7 cell line, we tested the possibility that 4.1B regulates mammary epithelial cell proliferation at least in part by regulating erbB2 activity. Compared to controls, MCF-7 cells induced to express DAL-1 demonstrated a nearly total reduction in erbB2 phosphorylation without any decrease in the total levels of erbB2 (Figure 7a).…”

Comparative study of Her-2, p53, Ki-67 expression and clinicopathological characteristics of breast cancer in a cohort of northern China female patients

“…Her-2 has been used as a predictive and prognostic biomarker of breast cancer. [12][13][14] P53, encoded by gene Tp53, is a transcription factor that as a tumor suppressor regulates the cell cycle. Mutation in the p53 genes causes the formation of proteins that are more stable than the wild type protein; the mutant proteins accumulate and can be analyzed by immunohistochemistry.…”