tyrphostin-ag825 and Breast-Neoplasms

Activation of the epidermal growth receptor (ErbB1) occurs within minutes of a radiation exposure. Immediate downstream consequences of this activation are currently indistinguishable from those obtained with growth factors (GF), e.g. stimulation of the pro-proliferative mitogen-activated protein kinase (MAPK). To identify potential differences, the effects of GFs and radiation on other members of the ErbB family have been compared in mammary carcinoma cell lines differing in their ErbB expression profiles. Treatment of cells with EGF (ErbB1-specific) or heregulin (ErbB4-specific) resulted in a hierarchic transactivations of ErbB2 and ErbB3 dependent on GF binding specificity. In contrast, radiation indiscriminately activated all ErbB species with the activation profile reflecting that cell's ErbB expression profile. Downstream consequences of these ErbB interactions were examined with MAPK after specifically inhibiting ErbB1 (or 4) with tyrphostin AG1478 or ErbB2 with tyrphostin AG825. MAPK activation by GFs or radiation was completely inhibited by AG1478 indicating total dependance on ErbB1 (or 4) depending on which ErbB is expressed. Inhibiting ErbB2 caused an enhanced MAPK response simulating an amplified ErbB1 (or 4) response. Thus ErbB2 is a modulator of ErbB1 (or 4) function leading to different MAPK response profiles to GF or radiation exposure.

Topics: Autocrine Communication; Benzothiazoles; Breast Neoplasms; Carcinoma; Epidermal Growth Factor; ErbB Receptors; Female; Genes, erbB; Growth Substances; Humans; Neuregulin-1; Quinazolines; Radiation, Ionizing; Receptor Protein-Tyrosine Kinases; Receptor, ErbB-2; Receptor, ErbB-3; Receptor, ErbB-4; Signal Transduction; Tumor Cells, Cultured; Tyrphostins

Topics: Acylation; Antineoplastic Agents; Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Crystallography, X-Ray; Dose-Response Relationship, Drug; Drug Screening Assays, Antitumor; Female; HSP90 Heat-Shock Proteins; Humans; Models, Molecular; Molecular Structure; Oxazoles; Oximes; Structure-Activity Relationship

ErbB2, a member of the ErbB family of receptor tyrosine kinases, is an essential player in the cell's growth and proliferation signaling pathways. Amplification or overexpression of ErbB2 is observed in ∼30% of breast cancer patients, and often drives cellular transformation and cancer development. Recently, we have shown that ErbB2 interacts with the nuclear-cytoplasmic shuttling protein nucleolin, an interaction which enhances cell transformation in vitro, and increases mortality risk and disease progression rate in human breast cancer patients. Given these results, and since acquired resistance to anti-ErbB2-targeted therapy is a major obstacle in treatment of breast cancer, we have examined the therapeutic potential of targeting the ErbB2-nucleolin complex. The effect of the nucleolin-specific inhibitor GroA (AS1411) on ErbB2-positive breast cancer was tested in vivo, in a mouse xenograft model for breast cancer; as well as in vitro, alone and in combination with the ErbB2 kinase-inhibitor tyrphostin AG-825. Here, we show that in vivo treatment of ErbB2-positive breast tumor xenografts with GroA reduces tumor size and leads to decreased ErbB2-mediated signaling. Moreover, we found that co-treatment of breast cancer cell lines with GroA and the ErbB2 kinase-inhibitor tyrphostin AG-825 enhances the anti-cancer effects exerted by GroA alone in terms of cell viability, mortality, migration, and invasiveness. We, therefore, suggest a novel therapeutic approach, consisting of combined inhibition of ErbB2 and nucleolin, which has the potential to improve breast cancer treatment efficacy.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Aptamers, Nucleotide; Benzothiazoles; Breast Neoplasms; Cell Line, Tumor; Disease Models, Animal; Drug Synergism; Female; Humans; MCF-7 Cells; Mice; Mice, Nude; Nucleolin; Oligodeoxyribonucleotides; Phosphoproteins; Receptor, ErbB-2; RNA-Binding Proteins; Signal Transduction; Tyrphostins; Xenograft Model Antitumor Assays

The ERBB2 nuclear transport in breast cancer cell lines after radiation and its possible role in radiation tolerance were observed. Confocal microscopy and Western blotting were applied to detect the nuclear ERBB2 expression after radiation in breast carcinomas cells. And the effects of Herceptin, AG825 and Cisplatin on the expression of nuclear ERBB2 were investigated. Survival fractions were also observed. After radiation, compared with control group, confocal microscopy and Western blot revealed that the expression of nuclear ERBB2 was increased in breast cancer cells time-dependently. Herceptin, and AG825 could significantly inhibit the radiation-induced nuclear ERBB2 expression, and decrease survival fractions. Cisplatin also induced the nuclear ERBB2 expression in breast cancer cells with high ERBB2 expression. It was concluded that radiation could induce ERBB2 nuclear transport, and nuclear ERBB2 may correlate with radiation resistance in breast cancer cells with high ERBB2 expression.

Topics: Active Transport, Cell Nucleus; Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Benzothiazoles; Breast Neoplasms; Cell Line, Tumor; Cell Nucleus; Cisplatin; Female; Humans; Nuclear Pore; Protein Transport; Radiation Tolerance; Receptor, ErbB-2; Trastuzumab; Tyrphostins