PMID- 18283037 OWN - NLM STAT- MEDLINE DCOM- 20080721 LR - 20211203 IS - 1569-8041 (Electronic) IS - 0923-7534 (Linking) VI - 19 IP - 6 DP - 2008 Jun TI - Low-scale phosphoproteome analyses identify the mTOR effector p70 S6 kinase 1 as a specific biomarker of the dual-HER1/HER2 tyrosine kinase inhibitor lapatinib (Tykerb) in human breast carcinoma cells. PG - 1097-109 LID - 10.1093/annonc/mdm589 [doi] AB - BACKGROUND: Discovery of key proliferative and/or survival cascades closely linked to the biological effects of human epidermal growth factor receptor (HER) 1 (erbB-1) and/or HER2 (erbB-2) inhibitors may identify a priori mechanisms responsible for the development of acquired resistance in breast cancer disease. Here, we took advantage of a semiquantitative protein array technology to identify intracellular oncogenic kinases that distinctively correlate with breast cancer cell sensitivity/resistance to the dual-HER1/HER2 tyrosine kinase inhibitor lapatinib (Tykerb(R)). MATERIALS AND METHODS: MCF-7 cells were forced to overexpress HER2 following stable transduction with pBABE-HER2 retroviruses. The Human Phospho-MAPK Array Proteome Profilertrade mark (R&D Systems) was used to molecularly assess the effects of both the mono-HER2 inhibitor trastuzumab (Herceptintrade mark) and the dual-HER1/HER2 inhibitor lapatinib on 21 different oncogenic kinases. A model of acquired resistance to lapatinib (MCF-7/HER2-Lap10 cells) was established by chronically exposing MCF-7/HER2 cells to increasing concentrations of lapatinib for >10 months. RESULTS: Treatment of MCF-7/HER2 cells with either trastuzumab or lapatinib similarly impaired HER2-enhanced activation status (i.e. phosphorylation) of the mitogen-activated protein kinases, c-Jun N-terminal kinases 1-3 and p38alpha/beta/gamma/delta and of the serine/threonine kinases AKT, glycogen synthase kinase-3, p90 ribosomal s6 kinase1/2, and mitogen- and stress-activated protein kinase1/2. Trastuzumab was less effective than lapatinib at blocking extracellular-signal regulated kinase (ERK) 1/2 and, notably, it failed to deactivate the mammalian target of rapamycin (mTOR) effector p70S6K1. Conversely, lapatinib treatment caused a drastic decrease in the phosphorylation of p70S6K1 at ERK1/2-regulated sites (Thr(421)/Ser(424)) and, as a consequence, p70S6K1 activity measured by its phospho-Thr(389) levels was abolished. The mTOR inhibitor rapamycin was found to supraadditively increase lapatinib efficacy in MCF-7/HER2 cells [ approximately 10-fold enhancement; combination index (CI(50)) = 0.243 < 1.0 = additivity, P < 0.001] but not in p70S6K1 gene-amplified MCF-7 parental cells ( approximately 1.3-fold enhancement; CI(50) = 0.920 congruent with 1.0 = additivity). Lapatinib-resistant MCF-7/HER2-Lap10 cells, which are capable of growing in the continuous presence of 10 microM lapatinib without significant effects on cell viability, notably exhibited a lapatinib-insensitive hyperphosphorylation of p70S6K1. Rapamycin cotreatment suppressed p70S6K1 hyperactivation and synergistically resensitized MCF-7/HER2-Lap10 cells to lapatinib (>20-fold increase in lapatinib-induced cytotoxicity; CI(50) = 0.175 < 1.0 = additivity). CONCLUSIONS: Serine-threonine kinase p70S6K1, a marker for mTOR activity that regulates protein translation, constitutes a specific biomarker for the biological effects of the dual-HER1/HER2 inhibitor lapatinib. The clinical implications of our data are that the efficacy of lapatinib might be enhanced with therapies that target the mTOR pathway. Rapamycin analogues such as CCI-779 (Temsirolimus) and RAD001 (Everolimus) may warrant further clinical evaluation to effectively delay or prevent the development of acquired resistance to lapatinib in HER2-positive breast cancer patients. FAU - Vazquez-Martin, A AU - Vazquez-Martin A AD - Catalan Institute of Oncology, Girona, Catalonia, Spain. FAU - Oliveras-Ferraros, C AU - Oliveras-Ferraros C FAU - Colomer, R AU - Colomer R FAU - Brunet, J AU - Brunet J FAU - Menendez, J A AU - Menendez JA LA - eng PT - Journal Article PT - Research Support, Non-U.S. Gov't DEP - 20080217 PL - England TA - Ann Oncol JT - Annals of oncology : official journal of the European Society for Medical Oncology JID - 9007735 RN - 0 (Antineoplastic Agents) RN - 0 (Biomarkers, Tumor) RN - 0 (Protein Kinase Inhibitors) RN - 0 (Proteome) RN - 0 (Quinazolines) RN - 0VUA21238F (Lapatinib) RN - EC 2.7.- (Protein Kinases) RN - EC 2.7.1.1 (MTOR protein, human) RN - EC 2.7.10.1 (Receptor, ErbB-2) RN - EC 2.7.11.1 (Ribosomal Protein S6 Kinases, 70-kDa) RN - EC 2.7.11.1 (TOR Serine-Threonine Kinases) RN - EC 2.7.11.1 (ribosomal protein S6 kinase, 70kD, polypeptide 1) SB - IM MH - Antineoplastic Agents/therapeutic use MH - Biomarkers, Tumor/*metabolism MH - Breast Neoplasms/*drug therapy MH - Cell Line, Tumor MH - Drug Resistance/*physiology MH - Female MH - Humans MH - Lapatinib MH - Protein Kinase Inhibitors/*therapeutic use MH - Protein Kinases/metabolism MH - Proteome MH - Proteomics MH - Quinazolines/*therapeutic use MH - Receptor, ErbB-2/metabolism MH - Ribosomal Protein S6 Kinases, 70-kDa/*metabolism MH - TOR Serine-Threonine Kinases EDAT- 2008/02/20 09:00 MHDA- 2008/07/22 09:00 CRDT- 2008/02/20 09:00 PHST- 2008/02/20 09:00 [pubmed] PHST- 2008/07/22 09:00 [medline] PHST- 2008/02/20 09:00 [entrez] AID - S0923-7534(19)41586-X [pii] AID - 10.1093/annonc/mdm589 [doi] PST - ppublish SO - Ann Oncol. 2008 Jun;19(6):1097-109. doi: 10.1093/annonc/mdm589. Epub 2008 Feb 17.