title: Chemical probing of HER2-amplified cancer cells identifies TORC2 as a particularly effective secondary target for combination with lapatinib.
abstract: The clinical impact of HER2 inhibitors in the treatment of HER2-amplified breast cancers has been largely confined to chemotherapy combination regimens, since HER2 inhibitors appear to have very modest efficacies by themselves. This is due to the resilient nature of the functionally relevant HER2-HER3 tumor driver, bidirectionally linked with downstream PI3K/Akt pathway signaling, which can break through the inhibitory effects of most current HER2 or HER3 targeting therapies. A vertical combination approach targeting HER2 and a downstream pathway is a highly rational strategy for much more effective targeted therapy of this disease. However the importance of these downstream pathways in many human tissues and cells significant limits their usefulness as secondary targets by narrowing the therapeutic index of such combination therapies. The secondary target that can afford the highest potential for clinical translation is the one with the highest synergy against tumor cells in combination with HER2-inhibition, allowing the widest therapeutic index for clinical translation. We conducted a comparative analysis of such secondary targets in combination with the HER2 inhibitor lapatinib and find that the inhibition of mTor affords the highest degree of synergy. In further dissecting the individual roles of TORC1 and TORC2 complexes using pharmacologic and genetic tools, we find that it is specifically the inactivation of TORC2 that most synergistically enhances the efficacy of lapatinib. Although inhibitors that selectively target TORC2 are not currently available, these data make a compelling case for their development.
authors.affiliation: Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA 94143, USA.
authors.forename: Dhara N
authors.initials: DN
authors.lastname: Amin
authors.affiliation: Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA 94143, USA.
authors.forename: Ana
authors.initials: A
authors.lastname: Ruiz-Saenz
authors.affiliation: Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA 94143, USA.
authors.forename: Nathaniel
authors.initials: N
authors.lastname: Gulizia
authors.affiliation: Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA 94143, USA.
authors.forename: Mark M
authors.initials: MM
authors.lastname: Moasser
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004357:Drug Synergism; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D000077341:Lapatinib; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D046912:Multiprotein Complexes / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D009287:Naphthyridines / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism; D011687:Purines / Q000494:pharmacology; D011799:Quinazolines / Q000494:pharmacology*; D011804:Quinolines / Q000494:pharmacology; D034622:RNA Interference; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D020893:Receptor, ErbB-3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D007093:Imidazoles; D007211:Indoles; D000077341:Lapatinib; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D046912:Multiprotein Complexes; D009287:Naphthyridines; D047428:Protein Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D011687:Purines; D011799:Quinazolines; D011804:Quinolines; D018719:Erb-b2 Receptor Tyrosine Kinases; D020893:Receptor, ErbB-3; D020123:Sirolimus; D058570:TOR Serine-Threonine Kinases; C553294:1-(4-(4-propionylpiperazin-1-yl)-3-(trifluoromethyl)phenyl)-9-(quinolin-3-yl)benzo(h)(1,6)naphthyridin-2(1H)-one; C581292:ERBB3 protein, human; C572919:PP242; C531198:dactolisib
keywords: HER2; HER3; TORC2; lapatinib; mTOR