Inhibition of class IA PI3K enzymes in non-small cell lung cancer cells uncovers functional compensation among isoforms.
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.
['Stamatkin|Christopher|C|', 'Ratermann|Kelley L|KL|', 'Overley|Colleen W|CW|', 'Black|Esther P|EP|']
D000970:Antineoplastic Agents D017209:Apoptosis D002289:Carcinoma, Non-Small-Cell Lung D059447:Cell Cycle Checkpoints D045744:Cell Line, Tumor D049109:Cell Proliferation D002470:Cell Survival D058543:Class Ia Phosphatidylinositol 3-Kinase D019008:Drug Resistance, Neoplasm D004354:Drug Screening Assays, Antitumor D004357:Drug Synergism D000069347:Erlotinib Hydrochloride D015870:Gene Expression D006801:Humans D020128:Inhibitory Concentration 50 D007527:Isoenzymes D008175:Lung Neoplasms D009025:Morpholines D051059:PTEN Phosphohydrolase D000081082:Phosphoinositide-3 Kinase Inhibitors D011687:Purines D011744:Pyrimidinones D052999:Quinazolinones D014227:Triazines
PI3K, AKT, mTOR, KRAS, EGFR, drug-resistant, non-squamous