5 results on '"Brent N. Rexer"'
Search Results
2. Phosphoproteomic mass spectrometry profiling links Src family kinases to escape from HER2 tyrosine kinase inhibition
- Author
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Carlos L. Arteaga, Jenny C. Chang, Daniel C. Liebler, Ana M. Gonzalez-Angulo, Amy-Joan L. Ham, N. De Matos Granja-Ingram, Cammie Rinehart, Gordon B. Mills, Bhuvanesh Dave, Brent N. Rexer, and Salisha Hill
- Subjects
Proteomics ,Cancer Research ,Receptor, ErbB-2 ,medicine.drug_class ,Molecular Sequence Data ,Breast Neoplasms ,Biology ,Lapatinib ,Mass Spectrometry ,Article ,Tyrosine-kinase inhibitor ,03 medical and health sciences ,chemistry.chemical_compound ,breast cancer ,0302 clinical medicine ,Cell Line, Tumor ,HER2 ,Genetics ,medicine ,Humans ,Amino Acid Sequence ,Phosphorylation ,lapatinib ,skin and connective tissue diseases ,Protein kinase A ,Protein Kinase Inhibitors ,Molecular Biology ,030304 developmental biology ,0303 health sciences ,Tyrosine-protein kinase CSK ,tyrosine phosphorylation ,Autophosphorylation ,Tyrosine phosphorylation ,Phosphoproteins ,3. Good health ,src-Family Kinases ,chemistry ,030220 oncology & carcinogenesis ,Cancer research ,Female ,Src kinases ,Tyrosine kinase ,medicine.drug ,Proto-oncogene tyrosine-protein kinase Src - Abstract
Despite the initial effectiveness of the tyrosine kinase inhibitor lapatinib against HER2 gene-amplified breast cancers, most patients eventually relapse after treatment, implying that tumors acquire mechanisms of drug resistance. To discover these mechanisms, we generated six lapatinib-resistant HER2-overexpressing human breast cancer cell lines. In cells that grew in the presence of lapatinib, HER2 autophosphorylation was undetectable, whereas active phosphoinositide-3 kinase (PI3K)-Akt and mitogen-activated protein kinase (MAPK) were maintained. To identify networks maintaining these signaling pathways, we profiled the tyrosine phosphoproteome of sensitive and resistant cells using an immunoaffinity-enriched mass spectrometry method. We found increased phosphorylation of Src family kinases (SFKs) and putative Src substrates in several resistant cell lines. Treatment of these resistant cells with Src kinase inhibitors partially blocked PI3K-Akt signaling and restored lapatinib sensitivity. Further, SFK mRNA expression was upregulated in primary HER2+ tumors treated with lapatinib. Finally, the combination of lapatinib and the Src inhibitor AZD0530 was more effective than lapatinib alone at inhibiting pAkt and growth of established HER2-positive BT-474 xenografts in athymic mice. These data suggest that increased Src kinase activity is a mechanism of lapatinib resistance and support the combination of HER2 antagonists with Src inhibitors early in the treatment of HER2+ breast cancers in order to prevent or overcome resistance to HER2 inhibitors.
- Published
- 2011
3. H1047R phosphatidylinositol 3-kinase mutant enhances HER2-mediated transformation by heregulin production and activation of HER3
- Author
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Anindita Chakrabarty, Carlos L. Arteaga, Brent N. Rexer, Jeffrey A. Engelman, Shizhen Emily Wang, and Rebecca S. Cook
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Cancer Research ,Receptor, ErbB-3 ,Neuregulin-1 ,Mutant ,P110α ,Biology ,Ligands ,medicine.disease_cause ,Lapatinib ,Article ,HER2 overexpression ,Cell Line ,Phosphatidylinositol 3-Kinases ,03 medical and health sciences ,Breast cancer ,0302 clinical medicine ,Growth factor receptor ,HER3 ,ErbB ,Genetics ,medicine ,Humans ,skin and connective tissue diseases ,neoplasms ,Molecular Biology ,030304 developmental biology ,Heregulin ,0303 health sciences ,Mutation ,Kinase ,Genes, erbB-2 ,3. Good health ,Gene Knockdown Techniques ,030220 oncology & carcinogenesis ,Cancer research ,RNA Interference ,PIK3CA mutations ,Carcinogenesis ,Cell Division ,medicine.drug - Abstract
Hyperactivation of phosphatidylinositol-3 kinase (PI3K) can occur as a result of somatic mutations in PIK3CA, the gene encoding the p110α subunit of PI3K. The HER2 oncogene is amplified in 25% of all breast cancers and some of these tumors also harbor PIK3CA mutations. We examined mechanisms by which mutant PI3K can enhance transformation and confer resistance to HER2-directed therapies. We introduced the PI3K mutations E545K and H1047R in MCF10A human mammary epithelial cells that also overexpress HER2. Both mutants conferred a gain of function to MCF10A/HER2 cells. Expression of H1047R PI3K, but not E545K PI3K, markedly upregulated the HER3/HER4 ligand heregulin (HRG). HRG siRNA inhibited growth of H1047R but not E545K-expressing cells and synergized with the HER2 inhibitors trastuzumab and lapatinib. The PI3K inhibitor BEZ235 markedly inhibited HRG and pAKT levels and, in combination with lapatinib, completely inhibited growth of cells expressing H1047R PI3K. These observations suggest that PI3K mutants enhance HER2-mediated transformation by amplifying the ligand-induced signaling output of the ErbB network. This also counteracts the full effect of therapeutic inhibitors of HER2. These data also suggest that mammary tumors that contain both HER2 gene amplification and PIK3CA mutations should be treated with a combination of HER2 and PI3K inhibitors.
- Published
- 2010
4. Direct inhibition of PI3K in combination with dual HER2 inhibitors is required for optimal antitumor activity in HER2+ breast cancer cells
- Author
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Siprachanh Chanthaphaychith, Kimberly B. Dahlman, Carlos L. Arteaga, and Brent N. Rexer
- Subjects
Class I Phosphatidylinositol 3-Kinases ,Receptor, ErbB-2 ,medicine.drug_class ,Morpholines ,Mutant ,Aminopyridines ,Mice, Nude ,Antineoplastic Agents ,Breast Neoplasms ,Drug resistance ,Biology ,Pharmacology ,Antibodies, Monoclonal, Humanized ,Lapatinib ,Tyrosine-kinase inhibitor ,Mice ,Phosphatidylinositol 3-Kinases ,03 medical and health sciences ,0302 clinical medicine ,Trastuzumab ,Cell Line, Tumor ,Biomarkers, Tumor ,medicine ,Animals ,Humans ,skin and connective tissue diseases ,Protein Kinase Inhibitors ,neoplasms ,PI3K/AKT/mTOR pathway ,Cell Proliferation ,Phosphoinositide-3 Kinase Inhibitors ,030304 developmental biology ,Medicine(all) ,0303 health sciences ,Xenograft Model Antitumor Assays ,3. Good health ,Drug Resistance, Neoplasm ,Apoptosis ,030220 oncology & carcinogenesis ,Mutation ,Monoclonal ,Quinazolines ,Female ,Research Article ,medicine.drug - Abstract
Introduction: Despite multiple advances in the treatment of HER2+ breast cancers, resistance develops even to combinations of HER2 targeting agents. Inhibition of PI3K pathway signaling is critical for the efficacy of HER2 inhibitors. Activating mutations in PIK3CA can overlap with HER2 amplification and have been shown to confer resistance to HER2 inhibitors in preclinical studies. Methods: Lapatinib-resistant cells were profiled for mutations in the PI3K pathway with the SNaPshot assay. Hotspot PIK3CA mutations were retrovirally transduced into HER2-amplified cells. The impact of PIK3CA mutations on the effect of HER2 and PI3K inhibitors was assayed by immunoblot, proliferation and apoptosis assays. Uncoupling of PI3K signaling from HER2 was investigated by ELISA for phosphoproteins in the HER2-PI3K signaling cascade. The combination of HER2 inhibitors with PI3K inhibition was studied in HER2-amplified xenograft models with wild-type or mutant PIK3CA. Results: Here we describe the acquisition of a hotspot PIK3CA mutation in cells selected for resistance to the HER2 tyrosine kinase inhibitor lapatinib. We also show that the gain of function conferred by these PIK3CA mutations partially uncouples PI3K signaling from the HER2 receptor upstream. Drug resistance conferred by this uncoupling was overcome by blockade of PI3K with the pan-p110 inhibitor BKM120. In mice bearing HER2-amplified wild-type PIK3CA xenografts, dual HER2 targeting with trastuzumab and lapatinib resulted in tumor regression. The addition of a PI3K inhibitor further improved tumor regression and decreased tumor relapse after discontinuation of treatment. In a PIK3CA-mutant HER2+ xenograft, PI3K inhibition with BKM120 in combination with lapatinib and trastuzumab was required to achieve tumor regression. Conclusion: These results suggest that the combination of PI3K inhibition with dual HER2 blockade is necessary to circumvent the resistance to HER2 inhibitors conferred by PIK3CA mutation and also provides benefit to HER2+ tumors with wild-type PIK3CA tumors.
- Published
- 2014
5. CRBP suppresses breast cancer cell survival and anchorage-independent growth
- Author
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Kazuyasu Nakaya, Rafael Mira-y-Lopez, Brent N. Rexer, Shigeo Nakajo, and Yuvarani S. Kuppumbatti
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Cancer Research ,Receptors, Retinoic Acid ,Cell ,Retinoic acid ,Apoptosis ,Simian virus 40 ,Phosphatidylinositol 3-Kinases ,chemistry.chemical_compound ,Breast ,Enzyme Inhibitors ,Vitamin A ,Tumor Stem Cell Assay ,Cell Line, Transformed ,Phosphoinositide-3 Kinase Inhibitors ,Contact Inhibition ,Kinase ,Neoplasm Proteins ,medicine.anatomical_structure ,Female ,Fatty Acid-Binding Protein 7 ,Cell Division ,Signal Transduction ,Morpholines ,Breast Neoplasms ,Tretinoin ,Protein Serine-Threonine Kinases ,Biology ,Fatty Acid-Binding Proteins ,Retinoic acid receptor activity ,Proto-Oncogene Proteins ,Cell Adhesion ,Genetics ,medicine ,Humans ,Molecular Biology ,Protein kinase B ,PI3K/AKT/mTOR pathway ,Cell growth ,Tumor Suppressor Proteins ,Retinol-Binding Proteins, Cellular ,Cell Transformation, Viral ,Enzyme Activation ,Retinol-Binding Proteins ,Agar ,chemistry ,Chromones ,Cancer cell ,Cancer research ,Carrier Proteins ,Proto-Oncogene Proteins c-akt - Abstract
We showed earlier that cellular retinol-binding protein (CRBP) expression is downregulated in a subset of human breast cancers. We have now investigated the outcome of ectopic CRBP expression in MTSV1-7 cells, a SV40 T antigen-transformed human breast epithelial cell line devoid of endogenous CRBP expression. We found that: (i) CRBP did not inhibit adherent cell growth but suppressed foci formation in post-confluent cultures and colony formation in soft agar; (ii) this effect was due to CRBP inhibition of cell survival, as demonstrated by viability and TUNEL assays of cells in soft-agar or plated on polyHEMA-coated dishes; (iii) CRBP inhibited protein kinase B/Akt activation in cells in suspension but not in adherent cells and the CRBP suppression of anchorage-independent growth was mimicked by cell treatment with the phosphatidylinositol-3 kinase (PI3K) inhibitor LY294002; (iv) CRBP enhanced retinyl ester formation and storage but did not regulate retinoic acid synthesis or retinoic acid receptor activity. Ectopic CRBP-mediated inhibition of anchorage-independent cell survival and colony formation in the absence of significantly altered responses to either retinol or retinoic acid was also documented in T47D human breast cancer cells. In conclusion, the data suggest two novel and linked CRBP functions in mammary epithelial cells: inhibition of the PI3K/Akt survival pathway and suppression of anchorage-independent growth.
- Published
- 2001
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