Salinomycin acts through reducing AKT-dependent thymidylate synthase expression to enhance erlotinib-induced cytotoxicity in human lung cancer cells

The cell line models to study tyrosine kinase inhibitors in non-small cell lung cancer with mutations in the epidermal growth factor receptor: A scoping review

Non-Small Cell Lung Cancer (NSCLC) represents ∼85% of all lung cancers and ∼15-20% of them are characterized by mutations affecting the Epidermal Growth Factor Receptor (EGFR). For several years now, a class of tyrosine kinase inhibitors was developed, targeting sensitive mutations affecting the EGFR (EGFR-TKIs). To date, the main burden of the TKIs employment is due to the onset of resistance mutations. This scoping review aims to resume the current situation about the cell line models employed for the in vitro evaluation of resistance mechanisms induced by EGFR-TKIs in oncogene-addicted NSCLC. Adenocarcinoma results the most studied NSCLC histotype with the H1650, H1975, HCC827 and PC9 mutated cell lines, while Gefitinib and Osimertinib the most investigated inhibitors. Overall, data collected frame the current advancement of this topic, showing a plethora of approaches pursued to overcome the TKIs resistance, from RNA-mediated strategies to the innovative combination therapies.

Pre-clinical evidence that salinomycin is active against retinoblastoma via inducing mitochondrial dysfunction, oxidative damage and AMPK activation

The poor outcomes in retinoblastoma necessitate new treatments. Salinomycin is an attractive candidate, and has demonstrated selective anti-cancer properties in different cancer types. This work addressed the efficacy of salinomycin in retinoblastoma models and probe the associated mechanisms. Cellular functional assays were conducted to determine the effects salinomycin in vitro. Xenograft retinoblastoma mouse model was established to investigate the efficacy of salinomycin in vivo. Biochemical assays were conducted to analyze the mechanism of salinomycin's action focusing on mitochondrial functions, energy reduction-related signaling pathways. Salinomycin has positive effects towards retinoblastoma cells regardless of heterogeneity through suppressing growth and inducing apoptosis. Salinomycin also specifically inhibits cells displaying stemness and highly invasive phenotypes. Using retinoblastoma xenograft mouse model, we show that salinomycin at non-toxic dose effectively inhibits growth and induces apoptosis. Mechanistic studies show that salinomycin inhibits mitochondrial respiration via specifically suppressing complex I and II activities, reduces mitochondrial membrane potential and decreases energy reduction, followed by induction of oxidative stress and damage, AMPK activation and mTOR inhibition. Our study highlights that adding salinomycin to the existing treatment armamentarium for retinoblastoma is beneficial.

Salinomycin-Loaded Iron Oxide Nanoparticles for Glioblastoma Therapy

Salinomycin is an antibiotic introduced recently as a new and effective anticancer drug. In this study, magnetic iron oxide nanoparticles (IONPs) were utilized as a drug carrier for salinomycin for potential use in glioblastoma (GBM) chemotherapy. The biocompatible polyethylenimine (PEI)-polyethylene glycol (PEG)-IONPs (PEI-PEG-IONPs) exhibited an efficient uptake in both mouse brain-derived microvessel endothelial (bEnd.3) and human U251 GBM cell lines. The salinomycin (Sali)-loaded PEI-PEG-IONPs (Sali-PEI-PEG-IONPs) released salinomycin over 4 days, with an initial release of 44% ± 3% that increased to 66% ± 5% in acidic pH. The Sali-IONPs inhibited U251 cell proliferation and decreased their viability (by approximately 70% within 48 h), and the nanoparticles were found to be effective in reactive oxygen species-mediated GBM cell death. Gene studies revealed significant activation of caspases in U251 cells upon treatment with Sali-IONPs. Furthermore, the upregulation of tumor suppressors (i.e., p53, Rbl2, Gas5) was observed, while TopII, Ku70, CyclinD1, and Wnt1 were concomitantly downregulated. When examined in an in vitro blood–brain barrier (BBB)-GBM co-culture model, Sali-IONPs had limited penetration (1.0% ± 0.08%) through the bEnd.3 monolayer and resulted in 60% viability of U251 cells. However, hyperosmotic disruption coupled with an applied external magnetic field significantly enhanced the permeability of Sali-IONPs across bEnd.3 monolayers (3.2% ± 0.1%) and reduced the viability of U251 cells to 38%. These findings suggest that Sali-IONPs combined with penetration enhancers, such as hyperosmotic mannitol and external magnetic fields, can potentially provide effective and site-specific magnetic targeting for GBM chemotherapy.

Targeting Autophagy for Overcoming Resistance to Anti-EGFR Treatments

Epidermal growth factor receptor (EGFR) plays critical roles in cell proliferation, tumorigenesis, and anti-cancer drug resistance. Overexpression and somatic mutations of EGFR result in enhanced cancer cell survival. Therefore, EGFR can be a target for the development of anti-cancer therapy. Patients with cancers, including non-small cell lung cancers (NSCLC), have been shown to response to EGFR-tyrosine kinase inhibitors (EGFR-TKIs) and anti-EGFR antibodies. However, resistance to these anti-EGFR treatments has developed. Autophagy has emerged as a potential mechanism involved in the acquired resistance to anti-EGFR treatments. Anti-EGFR treatments can induce autophagy and result in resistance to anti-EGFR treatments. Autophagy is a programmed catabolic process stimulated by various stimuli. It promotes cellular survival under these stress conditions. Under normal conditions, EGFR-activated phosphoinositide 3-kinase (PI3K)/AKT serine/threonine kinase (AKT)/mammalian target of rapamycin (mTOR) signaling inhibits autophagy while EGFR/rat sarcoma viral oncogene homolog (RAS)/mitogen-activated protein kinase kinase (MEK)/mitogen-activated protein kinase (MAPK) signaling promotes autophagy. Thus, targeting autophagy may overcome resistance to anti-EGFR treatments. Inhibitors targeting autophagy and EGFR signaling have been under development. In this review, we discuss crosstalk between EGFR signaling and autophagy. We also assess whether autophagy inhibition, along with anti-EGFR treatments, might represent a promising approach to overcome resistance to anti-EGFR treatments in various cancers. In addition, we discuss new developments concerning anti-autophagy therapeutics for overcoming resistance to anti-EGFR treatments in various cancers.

Astaxanthin enhances erlotinib-induced cytotoxicity by p38 MAPK mediated xeroderma pigmentosum complementation group C (XPC) down-regulation in human lung cancer cells

Astaxanthin has been demonstrated to exhibit a wide range of beneficial effects that include anti-cancer and anti-inflammatory properties. Xeroderma pigmentosum complementation group C (XPC) protein is an important DNA damage recognition factor in nucleotide excision repair and is involved in regulating non-small cell lung cancer (NSCLC) cell proliferation and viability. Erlotinib (Tarceva^R) is a selective epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor that has demonstrated clinical activity in NSCLC cells. However, whether astaxanthin and erlotinib could induce synergistic cytotoxicity in NSCLC cells through modulating XPC expression is unknown. In this study, we found that p38 MAPK activation by astaxanthin decreased XPC expression in two human lung adenocarcinoma A549 and H1975 cells. Inactivation of p38 MAPK by pharmacological inhibitor SB203580 or the specific small interfering RNA (siRNA) rescued the astaxanthin-reduced XPC mRNA and protein levels. Enforced expression of XPC cDNA or inhibiting the p38 MAPK activity reduced the cytotoxicity and cell growth inhibition of astaxanthin. In contrast, knockdown of XPC using siRNA enhanced the cytotoxic effects of astaxanthin. Moreover, astaxanthin synergistically enhanced cytotoxicity and cell growth inhibition of erlotinib in NSCLC cells, which were associated with the down-regulation of XPC expression and activation of p38 MAPK. Our findings suggested that the astaxanthin induced p38 MAPK mediated XPC down-regulation enhanced the erlotinib-induced cytotoxicity in A549 and H1975 cells.