Contribution of p53 in sensitivity to EGFR tyrosine kinase inhibitors in non-small cell lung cancer.

The emergence of resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in non-small cell lung cancer (NSCLC) with activating EGFR mutations is a major hindrance to treatment. We investigated the effects of p53 in primary sensitivity and acquired resistance to EGFR-TKIs in NSCLC cells. Changes in sensitivity to EGFR-TKIs were determined using p53 overexpression or knockdown in cells with activating EGFR mutations. We investigated EMT-related molecules, morphologic changes, and AXL induction to elucidate mechanisms of acquired resistance to EGFR-TKIs according to p53 status. Changes in p53 status affected primary sensitivity as well as acquired resistance to EGFR-TKIs according to cell type. Firstly, p53 silencing did not affect primary and acquired resistance to EGFR-TKIs in PC-9 cells, but it led to primary resistance to EGFR-TKIs through AXL induction in HCC827 cells. Secondly, p53 silencing in H1975 cells enhanced the sensitivity to osimertinib through the emergence of mesenchymal-to-epithelial transition, and the emergence of acquired resistance to osimertinib in p53 knockout cells was much slower than in H1975 cells. Furthermore, two cell lines (H1975 and H1975/p53KO) demonstrated the different mechanisms of acquired resistance to osimertinib. Lastly, the introduction of mutant p53-R273H induced the epithelial-to-mesenchymal transition and exerted resistance to EGFR-TKIs in cells with activating EGFR mutations. These findings indicate that p53 mutations can be associated with primary or acquired resistance to EGFR-TKIs. Thus, the status or mutations of p53 may be considered as routes to improving the therapeutic effects of EGFR-TKIs in NSCLC.

Natural Killer Cells as a Potential Biomarker for Predicting Immunotherapy Efficacy in Patients with Non-Small Cell Lung Cancer.

BACKGROUND: Immunotherapy with immune checkpoint inhibitors for non-small cell lung cancer (NSCLC) has emerged as an important treatment option. Although immunotherapy may significantly improve survival and quality of life, response rates are as low as 20% in NSCLC patients. OBJECTIVE: The identification of reliable biomarkers predicting response to immunotherapy is required urgently to determine patient selection guidelines. PATIENTS AND METHODS: Peripheral blood mononuclear cells (PBMCs) from nine NSCLC patients were collected pre- and post-treatment with immunotherapy. The immune cell composition of PBMCs was analyzed using CyTOF with an optimized 32-marker panel. The natural killer (NK) cell activity was assessed with the measurement of interferon (INF)-γ using an NK Vue™ kit. RESULTS: We found that the percentages of NK cell populations in the immune cells of PBMCs were prominently elevated in the immunotherapy responder group when compared with non-responders. While no meaningful differences were observed in other populations of immune cells, consistent with these results, the overall activity of NK cells in responders was highly elevated compared with that of non-responders. From the analysis of NK subsets, although differences in the population of early NK cells were not observed, the functionally differentiated late NK cells were prominently high in responders. CONCLUSIONS: The overall activity or number of NK cells may be a useful biomarker to predict immunotherapy response in patients with NSCLC.

Tumor-derived exosomal miR-619-5p promotes tumor angiogenesis and metastasis through the inhibition of RCAN1.4.

Tumor-derived exosomes (TEXs) contain enriched miRNAs that act as novel non-invasive biomarkers for cancer diagnosis and play a role in cancer progression. We investigated the exosomal miRNAs that affect cancer progression in non-small cell lung cancer (NSCLC) and identified the specific molecules involved. We identified that specific miRNAs in NSCLC cell-released exosomes can modulate angiogenesis, among which miR-619-5p was the most potent inducer. RCAN1.4 was identified as a target of miR-619-5p and its suppression promoted angiogenesis. Furthermore, the suppression of RCAN1.4 induced cell proliferation and metastasis in NSCLC cells. In patients with NSCLC, the level of RCAN1.4 expression was significantly lower, and that of miR-619-5p significantly higher, in tumor than normal lung tissues. miR-619-5p expression was higher than normal in exosomes isolated from the plasma of NSCLC patients. Finally, hypoxic conditions induced miR-619-5p upload into NSCLC cell-derived exosomes. Our findings indicate that exosomal miR-619-5p promotes the growth and metastasis of NSCLCs by regulating RCAN1.4 and can serve as a diagnostic indicator for these lung cancers.

Okadaic acid protects human neuroblastoma SH-SY5Y cells from 1-methyl-4-phenylpyridinium ion-induced apoptosis.

1-methyl-4-phenylpyridinium ion (MPP(+)) has been shown to selectively inhibit mitochondrial function and induce a parkinsonism-like syndrome. MPP(+) stimulates the production of reactive oxygen species (ROS) and induces cell death in vitro. In this study, we investigated the protective effects of okadaic acid on MPP(+)-induced cell death in SH-SY5Y neuroblastoma cells. We found that MPP(+)-induced apoptosis and -ROS generation were blocked by okadaic acid. MPP(+)-mediated activation of AKT was also inhibited by okadaic acid. Taken together, these results demonstrate that okadaic acid protects against MPP(+)-induced apoptosis by blocking ROS stimulation and ROS-mediated signaling pathways in SH-SY5Y cells. These data indicated that okadaic acid could provide a therapeutic strategy for the treatment of neurodegenerative diseases including Parkinson's disease.

Exosomal PD-L1 promotes tumor growth through immune escape in non-small cell lung cancer.

Programmed cell death protein-1/programmed cell death ligand-1 (PD-1/PD-L1) pathway blockade is a promising new cancer therapy. Although PD-1/PD-L1 treatment has yielded clinical benefits in several types of cancer, further studies are required to clarify predictive biomarkers for drug efficacy and to understand the fundamental mechanism of PD-1/PD-L1 interaction between host and tumor cells. Here, we show that exosomes derived from lung cancer cells express PD-L1 and play a role in immune escape by reducing T-cell activity and promoting tumor growth. The abundance of PD-L1 on exosomes represented the quantity of PD-L1 expression on cell surfaces. Exosomes containing PD-L1 inhibited interferon-gamma (IFN-γ) secretion by Jurkat T cells. IFN-γ secretion was restored by PD-L1 knockout or masking on the exosomes. Both forced expression of PD-L1 on cells without PD-L1 and treatment with exosomes containing PD-L1 enhanced tumor growth in vivo. PD-L1 was present on exosomes isolated from the plasma of patients with non-small cell lung cancer, and its abundance in exosomes was correlated with PD-L1 positivity in tumor tissues. Exosomes can impair immune functions by reducing cytokine production and inducing apoptosis in CD8+ T cells. Our findings indicate that tumor-derived exosomes expressing PD-L1 may be an important mediator of tumor immune escape.

Enhanced Glycolysis Supports Cell Survival in EGFR-Mutant Lung Adenocarcinoma by Inhibiting Autophagy-Mediated EGFR Degradation.

Oncogenic EGFR is essential for the development and growth of non-small cell lung cancer (NSCLC), but the precise roles of EGFR in lung cancer metabolism remain unclear. Here, we show that EGFR mutation-mediated enhancement of glycolysis is critical for EGFR stability. EGFR knockdown significantly decreased levels of glycolytic pathway intermediates via transcriptional regulation of glycolytic genes. EGFR mutation-enhanced glycolysis was required for fueling the tricarboxylic acid cycle, a critical component of EGFR stability. Nonsustained ATP production enhanced reactive oxygen species accumulation and subsequent JNK-mediated activation of autophagy, which in turn induced EGFR degradation. Our data show that EGFR-mutant NSCLCs require EGFR mutation-enhanced glycolysis to maintain EGFR stability. This pathway may serve as an attractive therapeutic target for EGFR-mutant NSCLCs.Significance: Enhanced glycolysis by EGFR mutation is required for maintaining EGFR levels via inhibition of JNK-induced autophagy. This provides a promising rationale for use of JNK activators in patients with EGFR-mutated NSCLC. Cancer Res; 78(16); 4482-96. ©2018 AACR.

Discovery of a Potent and Mutant-Selective EGFR Inhibitor that Overcomes T790M-Mediated Resistance in Lung Cancer.

BACKGROUND: Despite remarkable activity in epidermal growth factor receptor (EGFR)-mutant lung cancer patients, the clinical efficacy of EGFR tyrosine kinase inhibitors (TKIs) is limited by the emergence of acquired resistance, which is mostly caused by a secondary T790M mutation. Fortunately, newly developed, mutant-selective EGFR-TKIs against T790M have been proven as an effective therapeutic approach although only osimertinib has received the FDA approval until now. OBJECTIVE: To determine the in vitro and in vivo efficacy of a new EGFR TKI, OBX1-012 in cells with mutant EGFR. METHODS: Effects of OBX1-012 on cellular viability and EGFR-related signaling were determined in EGFR-mutant non-small cell lung cancer (NSCLC) cells, including cells harboring T790M mutations. In addition, in vivo efficacy of OBX1-012 was evaluated in xenograft models. RESULTS: We report the discovery and preclinical assessment of another novel, mutant-selective EGFR-TKI, OBX1-012. Compared with other mutant-selective EGFR-TKIs such as olumitinib and osimertinib, it showed similar potency and selectivity for mutant EGFR. OBX1-012 treatment was highly effective against human EGFR-mutant lung cancer models with or without EGFR T790M, not only in vitro but also in vivo. However, OBX1-012 like other EGFR-TKIs failed to exhibit efficacy for the exon 20 insertion mutation or C797S mutation, which was generated by site-directed mutagenesis and stable transfection of Ba/F3 cells. CONCLUSIONS: These results identify OBX1-012 as a highly effective, mutant-selective EGFR-TKI for the treatment of T790M-mediated resistance in NSCLC.

Multiple receptor tyrosine kinase activation related to ALK inhibitor resistance in lung cancer cells with ALK rearrangement.

The activation of alternative receptor tyrosine kinases (RTKs) is known to mediate resistance to ALK inhibitors. However, the role of multiple RTK activation in resistance has yet to be determined. Two crizotinib-resistant (H3122/CR-1 and H3122/CR-2) and one TAE684-resistant (H2228/TR) cell lines were established. Multi-RTK arrays and Western blots were performed to detect the activation of bypass signals. There were no secondary mutations in the sequencing. EGFR and MET were activated in H3122/CR-1 cells whereas EGFR and IGF1R were activated in H3122/CR-2 cells. Concomitant activation of MET did not contribute to resistance as crizotinib completely suppressed both p-MET and p-ALK in H3122/CR-1 cells, whose survival was not affected by crizotinib. However, combined inhibition of EGFR and ALK was effective in controlling this resistant cell line. In H3122/CR-2 cells, the inhibition of both ALK and IGF1R could effectively suppress cell growth, whereas simultaneous inhibition of ALK and EGFR brought about a less-effective suppression, indicating that IGF1R activation is the main resistance mechanism. H2228/TR cells showed activation of the HER family (EGFR, ErbB2, and ErbB3). Afatinib, a pan-HER inhibitor, was more potent in suppressing resistant cells than gefitinib when combined with crizotinib, which suggests that coactivation of ErbB2 and ErbB3 also contributes to resistance. Interestingly, all three resistant cell lines responded well to AUY922, which can inhibit ALK, EGFR, and IGF1R activity. Activation of multiple RTKs can occur during acquired resistance to ALK inhibitors, in which case the dominant or significant bypass signal should be identified to provide a more appropriate combination therapy.

Activation of the IGF1R pathway potentially mediates acquired resistance to mutant-selective 3rd-generation EGF receptor tyrosine kinase inhibitors in advanced non-small cell lung cancer.

Mutant-selective, 3rd-generation EGFR-TKIs were recently developed to control lung cancer cells harboring T790M-mediated resistance. However, the development of resistance to these novel drugs seems inevitable. Thus, we investigated the mechanism of acquired resistance to the mutant-selective EGFR-TKI WZ4002. We established five WZ4002-resistant cells, derived from cells harboring both EGFR and T790M mutations by long-term exposure to increasing doses of WZ4002. Compared with the parental cells, all resistant cells showed 10-100-folds higher resistance to WZ4002, as well as cross-resistance to other mutant-selective inhibitors. Among them, three resistant cells (HCC827/WR, PC-9/WR and H1975/WR) showed dependency on EGFR signaling, but two other cells (PC-9/GR/WR and PC-9/ER/WR) were not. Notably, insulin-like growth factor-1 receptor (IGF1R) was aberrantly activated in PC-9/GR/WR cells in phospho-receptor tyrosine kinase array, consistently accompanied by loss of IGF binding protein-3 (IGFBP3). Down-regulation of IGF1R by shRNA, as well as inhibition of IGF1R activity either by AG-1024 (a small molecule IGF1R inhibitor) or BI 836845 (a monoclonal anti-IGF1/2 blocking antibody), restored the sensitivity to WZ4002 both in vitro and xenograft. Taken together, these results suggest that activation of the IGF1R pathway associated with IGFBP3 loss can induce an acquired resistance to the mutant-selective EGFR-TKI, WZ4002. Therefore, a combined therapy of IGF1R inhibitors and mutant-selective EGFR-TKIs might be a viable treatment strategy for overcoming acquired resistance.

AKT/mTOR down-regulation by CX-4945, a CK2 inhibitor, promotes apoptosis in chemorefractory non-small cell lung cancer cells.

AIM: The response to chemotherapeutic drugs in non-small cell lung cancer (NSCLC) is unsatisfactory, leading to poor outcomes. This study the aimed to investigates anticancer effects of CX-4945, a potent casein kinase II (CK2) inhibitor, in chemorefractory NSCLC cells. MATERIALS AND METHODS: Cell proliferation and apoptosis assay were carried-out by annexin V-FITC and FACScan after drug treatment with paclitaxel, cisplatin and CX-4945. AKT/mTOR and CK2α signals were measured by western blotting. Treatment was carried-out using siRNA to inhibit CK2α. RESULTS: Paclitaxel, and cisplatin effectively inhibited cell proliferation and induced apoptosis in A549 cells, while not in H1299, Calu-1 and H358 cells. In these chemorefractory cell lines, AKT signalling was maintained despite drug treatment. However, CX-4945 suppressed cell growth, with cell-cycle arrest at G2/M phase and induced apoptosis with an increase of cleaved caspase-3 and PARP1 in a dose-dependent manner. Accordingly, AKT and its downstream signals such as mTOR and p70S6K were down-regulated by CX-4945. Transfection of CK2α siRNA had similar effects to CX-4945 treatment on cell proliferation and apoptosis. CONCLUSION: CX-4945 shows a promising anticancer action through down-regulation of AKT/mTOR signals, suggesting its possible application for treatment of chemorefractory lung cancer.

AUY922 effectively overcomes MET- and AXL-mediated resistance to EGFR-TKI in lung cancer cells.

The activation of bypass signals, such as MET and AXL, has been identified as a possible mechanism of EGFR-TKI resistance. Because various oncoproteins depend on HSP90 for maturation and stability, we investigated the effects of AUY922, a newly developed non-geldanamycin class HSP90 inhibitor, in lung cancer cells with MET- and AXL-mediated resistance. We established resistant cell lines with HCC827 cells harboring an exon 19-deletion mutation in of the EGFR gene via long-term exposure to increasing concentrations of gefitinib and erlotinib (HCC827/GR and HCC827/ER, respectively). HCC827/GR resistance was mediated by MET activation, whereas AXL activation caused resistance in HCC827/ER cells. AUY922 treatment effectively suppressed proliferation and induced cell death in both resistant cell lines. Accordingly, the downregulation of EGFR, MET, and AXL led to decreased Akt activation. The inhibitory effects of AUY922 on each receptor were confirmed in gene-transfected LK2 cells. AUY922 also effectively controlled tumor growth in xenograft mouse models containing HCC827/GR and HCC827/ER cells. In addition, AUY922 reduced invasion and migration by both types of resistant cells. Our study findings thus show that AUY922 is a promising therapeutic option for MET- and AXL-mediated resistance to EGFR-TKI in lung cancer.

MET and AXL inhibitor NPS-1034 exerts efficacy against lung cancer cells resistant to EGFR kinase inhibitors because of MET or AXL activation.

In non-small cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) mutations, acquired resistance to EGFR-tyrosine kinase inhibitors (EGFR-TKI) can occur through a generation of bypass signals such as MET or AXL activation. In this study, we investigated the antitumor activity of NPS-1034, a newly developed drug that targets both MET and AXL, in NSCLC cells with acquired resistance to gefitinib or erlotinib (HCC827/GR and HCC827/ER, respectively). Characterization of H820 cells and evaluation of NPS-1034 efficacy in these cells were also performed. The resistance of HCC827/GR was mediated by MET activation, whereas AXL activation led to resistance in HCC827/ER. The combination of gefitinib or erlotinib with NPS-1034 synergistically inhibited cell proliferation and induced cell death in both resistant cell lines. Accordingly, suppression of Akt was noted only in the presence of treatment with both drugs. NPS-1034 was also effective in xenograft mouse models of HCC827/GR. Although the H820 cell line was reported previously to have T790M and MET amplification, we discovered that AXL was also activated in this cell line. There were no antitumor effects of siRNA or inhibitors specific for EGFR or MET, whereas combined treatment with AXL siRNA or NPS-1034 and EGFR-TKIs controlled H820 cells, suggesting that AXL is the main signal responsible for resistance. In addition, NPS-1034 inhibited cell proliferation as well as ROS1 activity in HCC78 cells with ROS1 rearrangement. Our results establish the efficacy of NPS-1034 in NSCLC cells rendered resistant to EGFR-TKIs because of MET or AXL activation or ROS1 rearrangement.

Neuroendocrine differentiation in acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitor.

BACKGROUND: Small cell lung cancer (SCLC) transformation during epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) treatment in lung cancer has been suggested as one of possible resistance mechanisms. METHODS: We evaluated whether SCLC transformation or neuroendocrine (NE) differentiation can be found in the cell line model. In addition, we also investigated its effect on responses to conventional chemotherapeutic drugs of the SCLC treatment. RESULTS: Resistant cell lines to various kinds of EGFR-TKIs such as gefitinib, erlotinib, CL-387,785 and ZD6474 with A549, PC-9 and HCC827 lung adenocarcinoma cell lines were established. Among them, two resistant cell lines, A549/GR (resistant to gefitinib) and PC-9/ZDR (resistant to ZD6474) showed increased expressions of CD56 while increased synaptophysin, Rb, p16 and poly(ADP-ribose) polymerase were found only in A549/GR in western blotting, suggesting that NE differentiation occurred in A549/GR. A549/GR cells were more sensitive to etoposide and cisplatin, chemotherapeutic drugs for SCLC, compared to parental cells. Treatment with cAMP and IBMX induced synaptophysin and chromogranin A expression in A549 cells, which also made them more sensitive to etoposide and cisplatin than parental cells. Furthermore, we found a tissue sample from a patient which showed increased expressions of CD56 and synaptophysin after development of resistance to erlotinib. CONCLUSION: NE differentiation can occur during acquisition of resistance to EGFR-TKI, leading to increased chemosensitivity.

Ethyl pyruvate stabilizes hypoxia-inducible factor 1 alpha via stimulation of the TCA cycle.

Ethyl pyruvate is a simple derivative of the endogenous metabolite pyruvate. Pyruvate is the starting substrate for the tricarboxylic acid (TCA) cycle and plays a central role in intermediary metabolism. The present study was to determine whether ethyl pyruvate affects the expression of hypoxia-inducible factor 1 alpha (HIF-1alpha) and to explore the mechanism of HIF-1alpha regulation. We found that ethyl pyruvate increased HIF-1alpha stability via inhibition of pVHL-mediated degradation. Furthermore, ethyl pyruvate enhanced the reactive oxygen species (ROS) generated through the TCA cycle in mitochondria. Taken together, our results support a novel role for ethyl pyruvate in HIF-1alpha stabilization by which high rates of the TCA cycle can promote ROS production.

Okadaic acid promotes angiogenesis via activation of hypoxia-inducible factor-1.

Okadaic acid, a potent tumor promoter and an inhibitor of protein phosphatase 1 and 2A, has also been characterized as an angiogenic inducer in the chorioallantoic membrane of the chick embryo. To elucidate the roles of okadaic acid on angiogenic processes, we conducted in vitro angiogenesis assays. In this study, we report that okadaic acid potently stimulated tube formation, migration, and invasion of human umbilical vein endothelial cells. Moreover, okadaic acid elevated the activities of hypoxia-inducible factor-1 (HIF-1), which is closely related with the expression of vascular endothelial growth factor. Exposure to okadaic acid markedly increased the HIF-1alpha protein level through up-regulation of translation via activation of Akt and mTOR pathway. Taken together, these results demonstrated that okadaic acid promotes angiogenesis through stimulation of Akt mediated HIF-1alpha translation.