title: Inhibition of class IA PI3K enzymes in non-small cell lung cancer cells uncovers functional compensation among isoforms.
abstract: Deregulation of the phosphatidylinositol 3-kinase (PI3K) pathway is central to many human malignancies while normal cell proliferation requires pathway functionality. Although inhibitors of the PI3K pathway are in clinical trials or approved for therapy, an understanding of the functional activities of pathway members in specific malignancies is needed. In lung cancers, the PI3K pathway is often aberrantly activated by mutation of genes encoding EGFR, KRAS, and PIK3CA proteins. We sought to understand whether class IA PI3K enzymes represent rational therapeutic targets in cells of non-squamous lung cancers by exploring pharmacological and genetic inhibitors of PI3K enzymes in a non-small cell lung cancer (NSCLC) cell line system. We found that class IA PI3K enzymes were expressed in all cell lines tested, but treatment of NSCLC lines with isoform-selective inhibitors (A66, TGX-221, CAL-101 and IC488743) had little effect on cell proliferation or prolonged inhibition of AKT activity. Inhibitory pharmacokinetic and pharmacodynamic responses were observed using these agents at non-isoform selective concentrations and with the pan-class I (ZSTK474) agent. Response to pharmacological inhibition suggested that PI3K isoforms may functionally compensate for one another thus limiting efficacy of single agent treatment. However, combination of ZSTK474 and an EGFR inhibitor (erlotinib) in NSCLC resistant to each single agent reduced cellular proliferation. These studies uncovered unanticipated cellular responses to PI3K isoform inhibition in NSCLC that does not correlate with PI3K mutations, suggesting that patients bearing tumors with wildtype EGFR and KRAS are unlikely to benefit from inhibitors of single isoforms but may respond to pan-isoform inhibition.
authors.affiliation: a University of Kentucky; College of Pharmacy; Department of Pharmaceutical Sciences and Lucille P Markey Cancer Center Lexington ; Lexington , KY USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Stamatkin
authors.affiliation: a University of Kentucky; College of Pharmacy; Department of Pharmaceutical Sciences and Lucille P Markey Cancer Center Lexington ; Lexington , KY USA.
authors.forename: Kelley L
authors.initials: KL
authors.lastname: Ratermann
authors.affiliation: a University of Kentucky; College of Pharmacy; Department of Pharmaceutical Sciences and Lucille P Markey Cancer Center Lexington ; Lexington , KY USA.
authors.forename: Colleen W
authors.initials: CW
authors.lastname: Overley
authors.affiliation: a University of Kentucky; College of Pharmacy; Department of Pharmaceutical Sciences and Lucille P Markey Cancer Center Lexington ; Lexington , KY USA.
authors.forename: Esther P
authors.initials: EP
authors.lastname: Black
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy / Q000201:enzymology*; D059447:Cell Cycle Checkpoints; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival / Q000187:drug effects; D058543:Class Ia Phosphatidylinositol 3-Kinase / Q000235:genetics / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D004354:Drug Screening Assays, Antitumor; D004357:Drug Synergism; D000069347:Erlotinib Hydrochloride / Q000494:pharmacology; D015870:Gene Expression; D006801:Humans; D020128:Inhibitory Concentration 50; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D008175:Lung Neoplasms / Q000188:drug therapy / Q000201:enzymology*; D009025:Morpholines / Q000494:pharmacology; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011687:Purines / Q000494:pharmacology; D011744:Pyrimidinones / Q000494:pharmacology; D052999:Quinazolinones / Q000494:pharmacology; D014227:Triazines / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D007527:Isoenzymes; D009025:Morpholines; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011687:Purines; D011744:Pyrimidinones; D052999:Quinazolinones; C504718:TGX 221; D014227:Triazines; C510150:ZSTK474; D000069347:Erlotinib Hydrochloride; D058543:Class Ia Phosphatidylinositol 3-Kinase; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; C552946:idelalisib
keywords: PI3K, AKT, mTOR, KRAS, EGFR, drug-resistant, non-squamous