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Inhibition of class IA PI3K enzymes in non-small cell lung cancer cells uncovers functional compensation among
Christopher Stamatkin1, Kelley L Ratermann1, Colleen W Overley1
1a University of Kentucky; College of Pharmacy; Department of Pharmaceutical Sciences and Lucille P Markey Cancer Center Lexington ; Lexington , KY USA.
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.
Insights
Targeting the phosphatidylinositol 3-kinase (PI3K) pathway in non-small cell lung cancer (NSCLC) is complex. Isoform-selective inhibitors showed limited efficacy, but combined pan-class I PI3K and EGFR inhibition reduced proliferation.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Aberrant activation of the phosphatidylinositol 3-kinase (PI3K) pathway is a hallmark of many cancers, including lung cancer.
- Mutations in EGFR, KRAS, and PIK3CA frequently drive PI3K pathway activation in non-small cell lung cancer (NSCLC).
- Understanding the functional roles of PI3K pathway members is crucial for developing effective targeted therapies.
Purpose of the Study:
- To investigate whether class IA PI3K enzymes are viable therapeutic targets in non-squamous NSCLC.
- To explore the efficacy of pharmacological and genetic PI3K inhibitors in NSCLC cell lines.
- To determine the potential for isoform-specific versus pan-isoform PI3K inhibition in NSCLC treatment.
Main Methods:
- Utilized a non-small cell lung cancer (NSCLC) cell line system.
- Administered isoform-selective PI3K inhibitors (A66, TGX-221, CAL-101, IC488743) and a pan-class I PI3K inhibitor (ZSTK474).
- Investigated the effects of single-agent and combination therapies, including ZSTK474 with an EGFR inhibitor (erlotinib).
Main Results:
- Class IA PI3K enzymes were expressed in all tested NSCLC lines.
- Isoform-selective PI3K inhibitors had minimal impact on cell proliferation or AKT activity.
- Pharmacological inhibition revealed functional compensation among PI3K isoforms, limiting single-agent efficacy.
- Combination therapy with ZSTK474 and erlotinib reduced proliferation in resistant NSCLC cells.
- Observed unanticipated cellular responses to PI3K inhibition, independent of PI3K mutations.
Conclusions:
- Single-isoform PI3K inhibition is unlikely to be effective in NSCLC patients with wildtype EGFR and KRAS.
- Functional redundancy among PI3K isoforms necessitates pan-isoform inhibition strategies.
- Combination therapy targeting both PI3K and EGFR pathways shows promise for NSCLC treatment.
- These findings highlight the complex PI3K pathway dynamics in NSCLC and inform future therapeutic strategies.
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