tyrphostin-ag825 and Lung-Neoplasms

It has previously been demonstrated that 17-allylamino geldanamycin (17-AAG) enhances paclitaxel-mediated cytotoxicity and downregulates vascular endothelial factor expression in non-small cell lung cancer. This project was designed to evaluate the tumoricidal and antiangiogeneic effects of 17-AAG and paclitaxel in H358 non-small cell lung cancer cells grown as xenografts in nude mice.. In vitro cytotoxic drug combination effects were evaluated by (4, 5-dimethylthiazo-2-yl)-2, 5-diphenyl tetrazolium bromide-based proliferation assays. The combinations of 17-AAG and paclitaxel were administered intraperitoneally in nude mice bearing H358 tumor xenografts. Tumor volumes were measured weekly. Tumor expression of erbB2, vascular endothelial cell growth factor, von Willebrand factor (tumor microvasculature), and activated caspase 3 (apoptosis) were determined by immunohistochemistry.. Five- to 22-fold enhancement of paclitaxel cytotoxicity was achieved by paclitaxel + 17-AAG combination that was paralleled with marked induction of apoptosis. This combination treatment profoundly suppressed tumor growth and significantly prolonged survival of mice bearing H358 xenografts. Immunohistochemical staining of tumor tissues indicated profound reduction of vascular endothelial cell growth factor expression associated with reduction of microvasculature in tumors treated with 17-AAG. Apoptotic cells were more abundant in tumors treated with 17-AAG + paclitaxel than in those treated with 17-AAG or paclitaxel alone.. Concurrent exposure of H358 cells to 17-AAG and paclitaxel resulted in supraadditive growth inhibition effects in vitro and in vivo. Analysis of molecular markers of tumor tissues indicated that therapeutic drug levels could be achieved with this chemotherapy regimen leading to significant biological responses. Moreover, 17-AAG-mediated suppression of vascular endothelial cell growth factor production by tumor cells may contribute to the antitumor effects of this drug combination in vivo.

Topics: Allylamine; Animals; Antibiotics, Antineoplastic; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Benzoquinones; Benzothiazoles; Carcinoma, Non-Small-Cell Lung; Cell Survival; Drug Synergism; Drug Therapy, Combination; Endothelial Growth Factors; Humans; Lactams, Macrocyclic; Lung Neoplasms; Lymphokines; Mice; Mice, Nude; Neoplasm Transplantation; Neovascularization, Pathologic; Paclitaxel; Quinones; Tumor Cells, Cultured; Tyrphostins; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors

Overexpression of the growth factor receptor ErbB-2/Her2/Neu has been implicated in the development of non-small-cell lung cancer. We have reported that the transformation of human lung epithelial cells by c-erbB-2 also requires an active ErbB-1 (EGF receptor) and the autocrine production of its ligand, TGF-alpha. In this report, we demonstrate that STAT 3 is constitutively activated in these cells by the TGF-alpha-stimulated ErbB-1/-2 heterodimer complex. STAT 3 activation was confirmed by mobility shift assays and nuclear localization. ErbB-1 was required, but not sufficient for the TGF-alpha-induced activation of STATs. Inhibition of ErbB-2 kinase activity by tyrphostin AG825 prevented the constitutive activation of STAT 3 in the TGF-alpha-producing, ErbB-1 expressing cell line. Our results demonstrate a requirement for ErbB-2 kinase activity to establish constitutive STAT 3 activation resulting from an autocrine ErbB-1/ TGF-alpha loop. Int. J. Cancer 83:564-570, 1999. Published 1999 Wiley-Liss, Inc.

Topics: Benzothiazoles; Cell Line; Cell Nucleus; Dimerization; DNA-Binding Proteins; Electrophoresis, Polyacrylamide Gel; Enzyme Activation; Enzyme Inhibitors; Epithelial Cells; ErbB Receptors; Humans; Immunoblotting; Lung Neoplasms; Milk Proteins; Precipitin Tests; Receptor, ErbB-2; STAT1 Transcription Factor; STAT3 Transcription Factor; STAT5 Transcription Factor; Trans-Activators; Transfection; Transforming Growth Factor alpha; Tyrphostins

The HER-2/neu gene product, p185(neu), is a membrane-bound receptor with tyrosine kinase activity. High levels of p185(neu) is correlated with intrinsic chemoresistance of non-small cell lung cancer (NSCLC) cell lines. We investigated the effects of tyrphostin AG825, a selective tyrosine kinase inhibitor preferentially inhibiting HER-2/neu kinase, on the chemosensitivities and on the drug-induced cell cycle changes of NSCLC cell lines that expressed different levels of p185(neu). Compared to the low-p185(neu) expressing cell lines, we found that the high-p185(neu) expressing cell lines were more resistant to doxorubicin, etoposide, and cis-diamminedichloroplatinum(II) but more sensitive to AG825. AG825 was able to significantly enhance the chemosensitivities of the high-p185(neu) expressing cell lines, whereas it had little effect on the chemosensitivities of the low-p185(neu) expressing cells, with a few exceptions in which minor antagonistic effects were observed. Although high concentrations of AG825 could reduce the drug-induced G(2) arrest that was accompanied by the activation of phosphorylated p34(cdc2), we failed to find any remarkably differential effects of AG825 on drug-induced G(2), arrest and the accompanying phosphorylation status of p34(cdc2) of the high- and and the low-p185(neu) expressing cell lines. In summary, tyrphostin AG825 can enhance chemosensitivity in high- but not in low-p185(neu) expressing NSCLC cell lines. This differential effect cannot be explained by the alterations of drug-induced cell cycle changes by AG825. Our results provide a rationale to develop p185(neu)- specific tyrphostin and to test them in combination with anticancer agents in vivo and in clinical trials.

Topics: Benzothiazoles; Benzylidene Compounds; Carcinoma, Non-Small-Cell Lung; Cell Division; Drug Resistance; Humans; Lung Neoplasms; Nitriles; Protein-Tyrosine Kinases; Receptor, ErbB-2; Tumor Cells, Cultured; Tyrphostins