Biological insights in non-small cell lung cancer

Lung oncogenesis relies on intracellular cysteine to overcome oxidative stress.Several tumor types,including non-small cell lung cancer(NSCLC),upregulate the system x-c cystine/glutamate antiporter(xCT)through overexpression of the cystine transporter SLC7A11,thus sustaining intracellular cysteine levels to support glutathione synthesis.Nuclear factor erythroid 2-related factor 2(NRF2)serves as a master regulator of oxidative stress resistance by regulating SLC7A11,whereas Kelch-like ECH-associated protein(KEAP1)acts as a cytoplasmic repressor of the oxidative responsive transcription factor NRF2.Mutations in KEAP1/NRF2 and p53 induce SLC7A11 activation in NSCLC.Extracellular cystine is crucial in supplying the intracellular cysteine levels necessary to combat oxidative stress.Disruptions in cystine availability lead to iron-dependent lipid peroxidation,thus resulting in a type of cell death called ferroptosis.Pharmacologic inhibitors of xCT(either SLC7A11 or GPX4)induce ferroptosis of NSCLC cells and other tumor types.When cystine uptake is impaired,the intracellular cysteine pool can be sustained by the transsulfuration pathway,which is catalyzed by cystathionine-B-synthase(CBS)and cystathionine g-lyase(CSE).The involvement of exogenous cysteine/cystine and the transsulfuration pathway in the cysteine pool and downstream metabolites results in compromised CD8^(+)T cell function and evasion of immunotherapy,diminishing immune response and potentially reducing the effectiveness of immunotherapeutic interventions.Pyroptosis is a previously unrecognized form of regulated cell death.In NSCLCs driven by EGFR,ALK,or KRAS,selective inhibitors induce pyroptotic cell death as well as apoptosis.After targeted therapy,the mitochondrial intrinsic apoptotic pathway is activated,thus leading to the cleavage and activation of caspase-3.Consequently,gasdermin E is activated,thus leading to permeabilization of the cytoplasmic membrane and cell-lytic pyroptosis(indicated by characteristic cell membrane ballooning).Breakthroughs in KRAS G12C allele-specific inhibitors and potential mechanisms of resistance are also discussed herein.

PIM-1 inhibition with AZD1208 to prevent osimertinib- induced resistance in EGFR-mutation positive non-small cell lung cancer

Aim: The progression free survival of non-small cell lung cancer (NSCLC) patients has been doubled over the last years, but still single epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) lead to incomplete responses. Compensatory signaling pathways are activated upon single EGFR TKIs. We have shown that compounds, which inhibit these pathways, are synergistic with EGFR TKIs. Proviral integration site for Moloney murine leukemia virus (PIM) has been connected to cancer therapy resistance, being involved in receptor tyrosine kinase, signal transducer and activator of transcription 3 (STAT3) and interleukin-6 signaling. We hypothesized that combined PIM and EGFR inhibition may improve the upfront therapy of EGFR-mutation positive NSCLC. Methods: We reviewed the literature on PIM kinases, and performed cell viability assays, gene expression analyses, and immunoblotting experiments to reveal the mechanisms of action of the PIM inhibitor (AZD1208) alone and combined with osimertinib in five EGFR-mutation positive NSCLC cell lines. Results: Osimertinib alone induced the activation of signal transducer and activator of transcription 3 (STAT3) as well as other signaling nodes. Combined osimertinib and AZD1208 yielded moderate synergistic effects in all ;NSCLC cell lines investigated. Among the EGFR-mutation positive cell lines examined, the H1975 and PC9 cell lines had the highest PIM1 and STAT3 mRNA expression. The combination decreased the osimertinib-induced STAT3 phosphorylation. Conclusion: This study provides a short review on PIM kinases, and shows our results of combined PIM and EGFR inhibition in EGFR-mutation positive NSCLC cell lines. The combination was moderately synergistic but decreased STAT3 phosphorylation, an important signaling node in therapy resistance.