Cellular responses after (neratinib plus pemetrexed) exposure in NSCLC cells

Area of Science:

• Oncology
• Molecular Biology
• Pharmacology

Background:

• Neratinib and pemetrexed previously showed efficacy in killing non-small cell lung cancer (NSCLC) cells.
• Cells can activate survival mechanisms to counteract drug toxicity after exposure.
• Understanding resistance mechanisms is crucial for optimizing cancer therapy.

Purpose of the Study:

• To define the mechanisms that reduce the efficacy of neratinib and pemetrexed in NSCLC cells.
• To investigate the role of RAS mutations in drug response and resistance.
• To identify potential early resistance pathways to the drug combination.

Main Methods:

• Synergistic killing assays with neratinib and pemetrexed in NSCLC cells with various mutations.
• Assessment of cell survival mechanisms, including RAS, MEK, AKT, ERBB receptors, and mTOR pathways.
• Analysis of protein expression and activity at different time points post-drug exposure.
• Gene knockdown experiments to evaluate the role of specific mutations, such as KRAS.

Main Results:

• Neratinib and pemetrexed synergized to kill NSCLC cells with wild-type RAS, mutant KRAS (G12S, Q61H, G12A, G12C), mutant NRAS (Q61K), and mutant ERBB1 (L858R, L858R T790M, exon 19 deletion).
• Mutant KRAS G12V exhibited greater cytoprotective effects than activated MEK1 or AKT.
• Knockdown of mutant KRAS reduced the combination's killing efficacy at 48 hours.
• While RAS levels normalized by 48 hours in the absence of drugs, ERBB1, ERBB2, ERBB4, mTORC1, and mTORC2 activities remained low.
• Expression of Beclin1 and ATG5 remained elevated, while MCL1 and BCL-XL were lower.
• No evidence of 'early' resistance via activation of ERBB3, c-KIT, c-MET, PDGFRβ, or other intracellular signaling pathways was observed.

Conclusions:

• The drug combination of neratinib and pemetrexed demonstrates synergistic efficacy against a range of NSCLC mutations.
• Mutant KRAS appears to play a significant role in cytoprotection against this drug combination.
• Findings suggest that early resistance mechanisms do not readily develop following neratinib and pemetrexed exposure.
• Further investigation is warranted to elucidate the mechanisms underlying eventual resistance to neratinib and pemetrexed in NSCLC.