Development of Anti-pp60 ^<i>src</i> Serum with Antigen Produced in <i>Escherichia coli</i>

We have purified p60 src from bacterial recombinants which direct the synthesis of the Rous sarcoma virus transforming gene ( src ) product. This protein was injected into rabbits, and they produced a highly cross-reactive serum which can recognize the src protein from many different strains of Rous sarcoma virus. </jats:p

Abstract 3627: Inhibition of HER family kinase signaling and tumor cell proliferation in non-EGFR and non-HER2 positive cell lines by lapatinib

Abstract Deregulation of HER family receptor tyrosine kinases by gene amplification, mutation, protein overexpression or ligand activation promotes oncogenesis. Lapatinib is an oral, selective, potent, dual inhibitor of EGFR and HER2 kinases that is approved in combination with capecitabine for the treatment of patients with advanced or metastatic breast cancer whose tumors overexpress HER2 and who have received prior therapy including an anthracycline, a taxane and trastuzumab. We have identified a panel of tumor cell lines, including breast, colon and melanoma, with normal levels of expression of EGFR, HER2 and low to non-detectable levels of HER4 as determined by RT-PCR and western blotting that are sensitive to cell growth inhibition by lapatinib (IC50s = 90 to 540 nanomolar), but not by trastuzumab (IC50&amp;gt;100 micrograms/mL). High levels of HER3 determined by RT-PCR and western blot, phosphorylated HER3 determined by western blot, and at least one ligand of the HER family determined by RT-PCR are also detected in three cell lines, whereas no mutations of EGFR or HER2 are present. MDA-MB-175VIII, a breast cancer cell line, has a translocation and coamplification of the 8p12 and 11q13 regions and expresses a secreted fusion protein of neuregulin-1 (NRG1), which is a ligand of HER3. HCC2157, a breast cancer cell line, and CHL-1, a melanoma cell line, have high levels of neuregulin-2 (NRG2), another ligand of HER3, and NRG1 RNA, respectively. Sequencing of HER4 genomic DNA in CHL-1 revealed two mutations (2834G&amp;gt;T and 3248C&amp;gt;T) in exons 23 and 27. All three cell lines are also inhibited by an antibody directed against the HER2 dimerization domain. Lapatinib inhibited the phosphorylation of HER2 and HER3, and decreased AKT phosphorylation (Ser 473 and Thr 308) and cyclin D expression in the three cell lines. Small interfering RNA to HER2, HER3 or NRG1, but not EGFR, reduced cell proliferation of CHL-1 cells. NCI-H508, a colon cancer cell line, displayed phosphorylation of EGFR and HER2, but not phosphorylated HER3 and AKT, and had high levels of amphiregulin (AREG) RNA, an EGFR ligand. Lapatinib inhibited the phosphorylation of EGFR and HER2 and decreased ERK phosphorylation in NCI-H508. Small interfering RNA to EGFR or HER2, but not HER3, effectively inhibited cell proliferation of NCI-H508. These results demonstrate that lapatinib can inhibit EGFR and/or HER2 kinase activity and cell proliferation in non-EGFR or non-HER2 amplified or overexpressed tumor cell lines that express a HER ligand in an autocrine manner. Tumors from non-HER2 overexpressing patients who have benefited from lapatinib should be assessed for the expression of HER family kinases, their phosphorylation state and their ligands to determine whether these markers can be used to select patients for future studies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3627.</jats:p

Synergistic Effects of Foretinib with HER-Targeted Agents in MET and HER1- or HER2-Coactivated Tumor Cells

Abstract The HER and MET receptor tyrosine kinases (RTK) are coactivated in a subset of human tumors. This study characterizes MET and HER expression and signaling in a panel of human tumor cell lines and the differential susceptibility of these cell lines to single agents or combinations of foretinib, a multikinase MET inhibitor, with HER-targeted agents, erlotinib or lapatinib. Most MET-amplified tumor lines without HER1 or HER2 amplification are sensitive to foretinib, whereas MET-amplified lines with HER1 or HER2 amplification are more sensitive to the combination of foretinib with lapatinib or erlotinib. Interestingly, MET-overexpressing tumor cell lines with HER1 or HER2 amplification also exhibited reduced sensitivity to lapatinib or erlotinib in the presence of hepatocyte growth factor (HGF), indicating MET activation can decrease the effectiveness of HER1/2 inhibitors in some cell lines. Consistent with this observation, the effect of HGF on lapatinib or erlotinib sensitivity in these cells was reversed by foretinib, other MET inhibitors, or siRNA to MET. Western blot analyses showed that combining foretinib with erlotinib or lapatinib effectively decreased the phosphorylation of MET, HER1, HER2, HER3, AKT, and ERK in these cells. Furthermore, HER2-positive advanced or metastatic breast cancer patients treated with lapatinib who had higher tumor MET expression showed shorter progression-free survival (19.29 weeks in MET-high patients vs. 28.14 weeks in MET-low patients, P &amp;lt; 0.0225). These data suggest that combination therapy with foretinib and HER-targeted agents should be tested as a treatment option for HER1- or HER2-positive patients with MET-amplified or -overexpressing tumors. Mol Cancer Ther; 10(3); 518–30. ©2011 AACR.</jats:p