Oxaliplatin and cisplatin are widely used in cancer chemotherapy, however, their clinical efficiency is often limited by the development of resistance.We examined different mechanisms of resistance in the human teratocarcinoma cell line 2102EP following exposure to cisplatin or oxaliplatin. Cells were exposed ten times with IC90-doses of 30 microM cisplatin and 50 microM oxaliplatin, respectively. Different cell clones were tested for expression of resistance using the SRB-assay. Moreover, resistance mechanisms in terms of drug uptake, platinum-adduct formation, GSH metabolism, DNA mismatch repair and p53 protein function were investigated.Three cisplatin cell clones with significant resistance factors of 2.0 to 2.6 were found. Two oxaliplatin cell clones showed only weak resistance, with resistance factors of 1.6 and 1.7, respectively. In all three cisplatin-exposed cell clones a decreased cellular uptake of cisplatin was found. Furthermore, mechanisms of DNA damage tolerance may also play a role in the development of cisplatin-resistance in these cells. However, only two cell clones showed a decreased level of platinum-DNA-adducts. An increased DNA-repair of platinum-DNA adducts was not seen. In addition, no differences in expression of mismatch-repair proteins MSH2 and MLH1, tumor suppressor protein p53, or glutathione metabolism were found. However, significant resistance mechanisms for the observed oxaliplatin resistance could not be identified, although in one oxaliplatin-exposed cell clone, there was some evidence that a decreased cellular uptake of oxaliplatin may contribute to the observed low level resistance.The data add weight to the hypothesis that resistance mechanisms following oxaliplatin exposure may be similar to cisplatin. The precise mechanisms of resistance in the oxaliplatin-resistant cell clones are still not fully understood and current studies are underway to further eluciate this finding.
Non-small cell lung cancer (NSCLC) represents over 80% of lung cancer cases and has a high mortality worldwide, however, targeting common epidermal growth-factor receptor (EGFR) alterations (i.e., del19, L858R) has provided a paradigm shift in the treatment of NSCLC. Uncommon EGFR mutations, however, show variable efficacy to EGFR-targeted drugs depending on the molecular alterations within exons 18-21 which underlying biological mechanism are far from being clear. The substitution mutations of G719X in exon 18, L861Q in exon 21, S768I in exon 20, and exon 20 insertions are the most frequent mutations among the uncommon mutations. The development of fourth-generation EGFR-tyrosine kinase inhibitor (TKIs) has gained increased interest as these drugs are able to inhibit resistance mutations (e.g., C797S) often detected in NSCLC patients' resistance to third-generation EGFR TKIs. BDTX-1535 is an orally bioavailable, brain-penetrating, mutation-selective, irreversible EGFR inhibitor with significant antitumour activity in NSCLCs and glioblastomas (phase I/II trials ongoing). It is a fourth-generation EGFR inhibitor that was found to overcome resistance to osimertinib in preclinical models and has shown promising activity in NSCLC patients harbouring C797S mutations. In experimental models BDTX-1535 was found to inhibit all common EGFR mutations and more than 50 of uncommon mutations including T790M, C797S, L718X, E709X, S784F, V834L and A289V, however, exon 20 insertions are inhibited to a much lesser extent. In addition, mutations in the extracellular domain of the EGF receptor (e.g., EGFRvII, III, IV) can be blocked as well. It should be noted that in up to 50% of all NSCLC patients who progress following osimertinib or other EGFR TKI therapy no underlying resistance mechanism can be identified suggesting that non-mutational signal transduction pathways may also be operative, and intratumoural heterogeneity has been found to be a major contributor to resistance and it consists of three main mechanisms: (I) drug-tolerant persister (DTP) cells, (II) chromosomal instability, and (III) extrachromosomal extracellular DNA (ecDNA) (seen in over 50% of NSCLCs) suggesting that novel EGFR TKIs will include many challenges in sufficiently targeting on-target resistance mechanisms. The development of novel drugs that can overcome TKI resistance in NSCLC patients harbouring the C797S mutation and beyond is, therefore, eagerly warranted.
The significant progress has been made in targeted therapy for lung adenocarcinoma (LUAD) in the past decade. Only few targeted therapeutics have yet been approved for the treatment of lung squamous cell carcinoma (LUSC). Several higher frequency of gene alterations are identified as potentially actionable in LUSC. Our work aimed to explore the complex interplay of multiple genetic alterations and pathways contributing to the pathogenesis of LUSC, with a very low frequency of a single driver molecular alterations to develop more effective therapeutic strategies in the future.
Metabolic reprogramming is a major feature of many tumors including non-small cell lung cancer (NSCLC). Branched-chain α-keto acid dehydrogenase kinase (BCKDK) plays an important role in diabetes, obesity, and other diseases. However, the function of BCKDK in NSCLC is unclear. This study aimed to explore the function of BCKDK in NSCLC.Metabolites in the serum of patients with NSCLC and the supernatant of NSCLC cell cultures were detected using nuclear magnetic resonance (NMR) spectroscopy. Colony formation, cell proliferation, and cell apoptosis were assessed to investigate the function of BCKDK in the progression of NSCLC. Glucose uptake, lactate production, cellular oxygen consumption rate, extracellular acidification rate, and reactive oxygen species (ROS) were measured to examine the function of BCKDK in glucose metabolism. The expression of BCKDK was measured using reverse transcriptase-polymerase chain reaction, western blot, and immunohistochemical assay.Compared with healthy controls and postoperative NSCLC patients, increased branched-chain amino acid (BCAA) and decreased citrate were identified in the serum of preoperative NSCLC patients. Upregulation of BCKDK affected the metabolism of BCAAs and citrate in NSCLC cells. Knockout of BCKDK decreased the proliferation and exacerbated apoptosis of NSCLC cells ex vivo, while increased oxidative phosphorylation and, ROS levels, and inhibited glycolysis.BCKDK may influence glycolysis and oxidative phosphorylation by regulating the degradation of BCAA and citrate, thereby affecting the progression of NSCLC.
