The Circular RNA Landscape of Non-Small Cell Lung Cancer Cells.

The class of circular RNA (circRNA) is characterized by head-to-tail bonds between exons formed by backsplicing. Here, we provide a resource of circRNA expression in a comprehensive panel of 60 lung cancer and non-transformed cell lines (FL3C dataset). RNA sequencing after depletion of ribosomal RNA quantified the expression of circRNA and linear RNA. We detected 148,811 circular RNAs quantified by 2.8 million backsplicing reads originating from 12,251 genes. The number of identified circRNAs was markedly higher using rRNA depletion compared to public polyA-enriched RNA-seq datasets. CircRNAs almost never started in the first exon nor ended in the last exon and started more frequently in earlier exons. Most circRNAs showed high cell line specificity and correlated positively with their linear RNA counterpart. Known cancer genes produced more circRNAs than non-cancer genes. Subsets of circRNAs correlated with cell proliferation, histological subtype or genotype. CircTNFRSF21 was translated crossing the backsplice site in two different reading frames. Overexpression of circPVT1, circERBB2, circHIPK3, circCCNB1, circSMAD2, circTNFRSF21 and circKIF5B significantly increased colony formation. In conclusion, our data provide a comprehensive map of circRNA expression in lung cancer cells and global patterns of circRNA production as a useful resource for future research into lung cancer circRNAs.

Crizotinib sensitizes the erlotinib resistant HCC827GR5 cell line by influencing lysosomal function.

In non-small cell lung cancer, sensitizing mutations in epidermal growth factor receptor (EGFR) or cMET amplification serve as good biomarkers for targeted therapies against EGFR or cMET, respectively. Here we aimed to determine how this different genetic background would affect the interaction between the EGFR-inhibitor erlotinib and the cMET-inhibitor crizotinib. To unravel the mechanism of synergy we investigated the effect of the drugs on various parameters, including cell cycle arrest, migration, protein phosphorylation, kinase activity, the expression of drug efflux pumps, intracellular drug concentrations, and live-cell microscopy. We observed additive effects in EBC-1, H1975, and HCC827, and a strong synergism in the HCC827GR5 cell line. This cell line is a clone of the HCC827 cells that harbor an EGFR exon 19 deletion and has been made resistant to the EGFR-inhibitor gefitinib, resulting in cMET amplification. Remarkably, the intracellular concentration of crizotinib was significantly higher in HCC827GR5 compared to the parental HCC827 cell line. Furthermore, live-cell microscopy with a pH-sensitive probe showed a differential reaction of the pH in the cytoplasm and the lysosomes after drug treatment in the HCC827GR5 in comparison with the HCC827 cells. This change in pH could influence the process of lysosomal sequestration of drugs. These results led us to the conclusion that lysosomal sequestration is involved in the strong synergistic reaction of the HCC827GR5 cell line to crizotinib-erlotinib combination. This finding warrants future clinical studies to evaluate whether genetic background and lysosomal sequestration could guide tailored therapeutic interventions.

The Role of c-Met as a Biomarker and Player in Innate and Acquired Resistance in Non-Small-Cell Lung Cancer: Two New Mutations Warrant Further Studies.

The c-Met receptor is a therapeutically actionable target in non-small-cell lung cancer (NSCLC), with one approved drug and several agents in development. Most suitable biomarkers for patient selection include c-Met amplification and exon-14 skipping. Our retrospective study focused on the frequency of different c-Met aberrations (overexpression, amplification and mutations) in 153 primary, therapy-naïve resection samples and their paired metastases, from Biobank@UZA. Furthermore, we determined the correlation of c-Met expression with clinicopathological factors, Epidermal Growth Factor Receptor (EGFR)-status and TP53 mutations. Our results showed that c-Met expression levels in primary tumors were comparable to their respective metastases. Five different mutations were detected by deep sequencing: three (E168D, S203T, N375S) previously described and two never reported (I333T, G783E). I333T, a new mutation in the Sema(phorin) domain of c-Met, might influence the binding of antibodies targeting the HGF-binding domain, potentially causing innate resistance. E168D and S203T mutations showed a trend towards a correlation with high c-Met expression (p = 0.058). We found a significant correlation between c-MET expression, EGFR expression (p = 0.010) and EGFR mutations (p = 0.013), as well as a trend (p = 0.057) with regards to TP53 mutant activity. In conclusion this study demonstrated a strong correlation between EGFR mutations, TP53 and c-Met expression in therapy-naïve primary resection samples. Moreover, we found two new c-Met mutations that warrant further studies.

Decrease in phospho-PRAS40 plays a role in the synergy between erlotinib and crizotinib in an EGFR and cMET wild-type squamous non-small cell lung cancer cell line.

INTRODUCTION: Lung squamous cell carcinomas (SCC) typically harbor a strong activation of epidermal growth factor receptor (EGFR) pathway. Since one of the most common resistance mechanisms against EGFR inhibition relies on the activation of cMET parallel signaling, we investigated the efficacy of a dual blockade with erlotinib and crizotinib in EGFR and cMET wild-type lung SCC cell lines. METHODS: Drug sensitivity assays were performed on LUDLU, SKMES-1, H1703, Calu1 and H520 cells. Further studies included analysis of cell cycle, apoptosis, spheroids, migration and Pathscan intracellular signaling array. Expression of emerging proteins was validated by Western blot and evaluated by immunohistochemistry in tissue-microarrays from lung cancer patients. RESULTS: Erlotinib and crizotinib showed additive interaction in Calu1, H520 and SKMES-1, and strong synergism in the LUDLU cells (Combination Index: 0.387), associated to G2/M phase arrest, increased apoptosis, spheroid size reduction and inhibition of migration. Remarkably, this combination decreased the phosphorylation of downstream targets of MAPK and PI3K/Akt/mTOR pathways, with the largest decrease observed for PRAS40 Thr246. Moreover, it reduced the expression of both p-Her3 and p-PRAS40 in the synergistic LUDLU cells. Tissue specimens showed a higher expression of both proteins in SCC compared to adenocarcinoma histology. CONCLUSIONS: Combining erlotinib and crizotinib led to an additive/synergistic interaction in 4 out of 5 SCC cells. By combining both inhibitors, MAPK and PI3K/Akt/mTOR pathways were strongly inhibited, leading to increased cell death. p-Her3 and p-PRAS40 might be used as markers for determining the synergistic effect and for selecting potential candidates for the combination treatment.

Double Trouble: A Case Series on Concomitant Genetic Aberrations in NSCLC.

Several oncogenic drivers have been identified in non-small cell lung cancer. Targeted therapies for these aberrations have already been successfully developed and implemented in clinical practice. Owing to improved sensitivity in genetic testing, more and more tumors with multiple driver mutations are identified, resulting in dilemmas for treating physicians whether and which targeted therapy to use. In this case series, we provide an overview of patients with intrinsic double mutations in oncogenic drivers and their reported response to targeted therapies, with a focus on epidermal growth factor receptor, anaplastic lymphoma kinase, cMET, and Kirsten rat sarcoma viral oncogene. We also include an unpublished case report on a patient with an epidermal growth factor receptor L858R and cMET exon 14 skipping.

Enhanced efficacy of AKT and FAK kinase combined inhibition in squamous cell lung carcinomas with stable reduction in PTEN.

Squamous cell lung carcinoma (SCC) accounts for 30% of patients with NSCLC and to date, no molecular targeted agents are approved for this type of tumor. However, recent studies have revealed several oncogenic mutations in SCC patients, including an alteration of the PI3K/AKT pathway, i.e. PI3K point mutations and amplification, AKT mutations and loss or reduced PTEN expression. Prompted by our observation of a correlation between PTEN loss and FAK phosphorylation in a cohort of patients with stage IV SCC, we evaluated the relevance of PTEN loss in cancer progression as well as the efficacy of a new combined treatment with the pan PI3K inhibitor buparlisip and the FAK inhibitor defactinib. An increase in AKT and FAK phosphorylation, associated with increased proliferation and invasiveness, paralleled by the acquisition of mesenchymal markers, and overexpression of the oncomir miR-21 were observed in SKMES-1-derived cell clones with a stable reduction of PTEN. Notably, the combined treatment induced a synergistic inhibition of cell proliferation, and a significant reduction in cell migration and invasion only in cells with reduced PTEN. The molecular mechanisms underlying these findings were unraveled using a specific RTK array that showed a reduction in phosphorylation of key kinases such as JNK, GSK-3 α/ß, and AMPK-α2, due to the concomitant decrease in AKT and FAK activation. In conclusion, the combination of buparlisib and defactinib was effective against cells with reduced PTEN and warrants further studies as a novel therapeutic strategy for stage IV SCC patients with loss of PTEN expression.

FGFR a promising druggable target in cancer: Molecular biology and new drugs.

INTRODUCTION: The Fibroblast Growth Factor Receptor (FGFR) family consists of Tyrosine Kinase Receptors (TKR) involved in several biological functions. Recently, alterations of FGFR have been reported to be important for progression and development of several cancers. In this setting, different studies are trying to evaluate the efficacy of different therapies targeting FGFR. AREAS COVERED: This review summarizes the current status of treatments targeting FGFR, focusing on the trials that are evaluating the FGFR profile as inclusion criteria: Multi-Target, Pan-FGFR Inhibitors and anti-FGF (Fibroblast Growth Factor)/FGFR Monoclonal Antibodies. EXPERT OPINION: Most of the TKR share intracellular signaling pathways; therefore, cancer cells tend to overcome the inhibition of one tyrosine kinase receptor by activating another. The future of TKI (Tyrosine Kinase Inhibitor) therapy will potentially come from multi-targeted TKIs that target different TKR simultaneously. It is crucial to understand the interaction of the FGF-FGFR axis with other known driver TKRs. Based on this, it is possible to develop therapeutic strategies targeting multiple connected TKRs at once. One correct step in this direction is the reassessment of multi target inhibitors considering the FGFR status of the tumor. Another opportunity arises from assessing the use of FGFR TKI on patients harboring FGFR alterations.

Deep sequencing of the TP53 gene reveals a potential risk allele for non-small cell lung cancer and supports the negative prognostic value of TP53 variants.

The TP53 gene remains the most frequently altered gene in human cancer, of which variants are associated with cancer risk, therapy resistance, and poor prognosis in several tumor types. To determine the true prognostic value of TP53 variants in non-small cell lung cancer, this study conducted further research, particularly focusing on subtype and tumor stage. Therefore, we determined the TP53 status of 97 non-small cell lung cancer adenocarcinoma patients using next generation deep sequencing technology and defined the prognostic value of frequently occurring single nucleotide polymorphisms and mutations in the TP53 gene. Inactivating TP53 mutations acted as a predictor for both worse overall and progression-free survival in stage II-IV patients and patients treated with DNA-damaging (neo)adjuvant therapy. In stage I tumors, the Pro-allele of the TP53 R72P polymorphism acted as a predictor for worse overall survival. In addition, we detected the rare R213R (rs1800372, minor allele frequency: 0.0054) polymorphism in 7.2% of the patients and are the first to show the significant association with TP53 mutations in non-small cell lung cancer adenocarcinoma patients (p = 0.003). In conclusion, Our findings show an important role for TP53 variants as negative predictors for the outcome of non-small cell lung cancer adenocarcinoma patients, especially for TP53 inactivating mutations in advanced stage tumors treated with DNA-damaging agents, and provide the first evidence of the R213R G-allele as possible risk factor for non-small cell lung cancer.

Better to be alone than in bad company: The antagonistic effect of cisplatin and crizotinib combination therapy in non-small cell lung cancer.

AIM: To investigate the potential benefit of combining the cMET inhibitor crizotinib and cisplatin we performed in vitro combination studies. METHODS: We tested three different treatment schemes in four non-small cell lung cancer (NSCLC) cell lines with a different cMET/epidermal growth factor receptor genetic background by means of the sulforhodamine B assay and performed analysis with Calcusyn. RESULTS: All treatment schemes showed an antagonistic effect in all cell lines, independent of the cMET status. Despite their different genetic backgrounds, all cell lines (EBC-1, HCC827, H1975 and LUDLU-1) showed antagonistic combination indexes ranging from 1.3-2.7. These results were independent of the treatment schedule. CONCLUSION: These results discourage further efforts to combine cMET inhibition with cisplatin chemotherapy in NSCLC.

New developments in the management of non-small-cell lung cancer, focus on rociletinib: what went wrong?

Recently, the development of the third-generation epidermal growth factor receptor-small molecule inhibitor (EGFR-TKI) rociletinib had failed. In this review, the wide-ranging aspects of the evolution of EGFR-TKIs were collected, with a special focus on rociletinib. The influence of different oncogenic mutations on EGFR activity was also discussed. Resistance to the first (erlotinib, gefitinib)- and second (afatinib)-generation EGFR-TKIs provided the rationale behind the development of the third-generation inhibitors (rociletinib, osimertinib). On the basis of these data, a comparison of their efficacy on the different mutated EGFRs and the respective resistance mechanisms is further reported. Moreover, the evolution and results of the clinical trials of rociletinib (TIGER trials) are compared with the trials on osimertinib, another third-generation EGFR-TKI that now has been granted US Food and Drug Administration approval. The reasons behind the arrest in the further development of rociletinib are put in the perspective of future drug development.

Exosomal miRNA Analysis in Non-small Cell Lung Cancer (NSCLC) Patients' Plasma Through qPCR: A Feasible Liquid Biopsy Tool.

The discovery of alterations in the EGFR and ALK genes, amongst others, in NSCLC has driven the development of targeted-drug therapy using selective tyrosine kinase inhibitors (TKIs). To optimize the use of these TKIs, the discovery of new biomarkers for early detection and disease progression is mandatory. These plasma-isolated exosomes can be used as a non-invasive and repeatable way for the detection and follow-up of these biomarkers. One ml of plasma from 12 NSCLC patients, with different mutations and treatments (and 6 healthy donors as controls), were used as exosome sources. After RNAse treatment, in order to degrade circulating miRNAs, the exosomes were isolated with a commercial kit and resuspended in specific buffers for further analysis. The exosomes were characterized by western blotting for ALIX and TSG101 and by transmission electron microscopy (TEM) analysis, the standard techniques to obtain biochemical and dimensional data of these nanovesicles. Total RNA extraction was performed with a high yield commercial kit. Due to the limited miRNA-content in exosomes, we decided to perform retro-transcription PCR using an individual assay for each selected miRNA. A panel of miRNAs (30b, 30c, 103, 122, 195, 203, 221, 222), all correlated with NSCLC disease, were analyzed taking advantage of the remarkable sensitivity and specificity of Real-Time PCR analysis; mir-1228-3p was used as endogenous control and data were processed according to the formula 2(-) (ΔΔct) (13). Control values were used as baseline and results are shown in logarithmic scale.

cMET Exon 14 Skipping: From the Structure to the Clinic.

The abnormal stimulation of the multiple signal transduction pathways downstream of the receptor tyrosine kinase mesenchymal-epithelial transition factor (cMET) promotes cellular transformation, tumor motility, and invasion. Therefore, cMET has been the focus of prognostic and therapeutic studies in different tumor types, including non-small cell lung cancer. In particular, several cMET inhibitors have been developed as innovative therapeutic candidates and are currently under investigation in clinical trials. However, one of the challenges in establishing effective targeted treatments against cMET remains the accurate identification of biomarkers for the selection of responsive subsets of patients. Recently, splice site mutations have been discovered in cMET that lead to the skipping of exon 14, impairing the breakdown of the receptor. Patients with NSCLC who are carrying this splice variant typically overexpress the cMET receptor and show a response to small molecule inhibitors of cMET. Here, we review the main differences at the structural level between the wild-type and the splice variants of cMET and their influence on cMET signaling. We clarify the reason why this variant responds to small molecule inhibitors and their prognostic/predictive role.

APR-246 (PRIMA-1(MET)) strongly synergizes with AZD2281 (olaparib) induced PARP inhibition to induce apoptosis in non-small cell lung cancer cell lines.

APR-246 (PRIMA-1(Met)) is able to bind mutant p53 and restore its normal conformation and function. The compound has also been shown to increase intracellular ROS levels. Importantly, the poly-[ADP-ribose] polymerase-1 (PARP-1) enzyme plays an important role in the repair of ROS-induced DNA damage. We hypothesize that by blocking this repair with the PARP-inhibitor AZD2281 (olaparib), DNA damage would accumulate in the cell leading to massive apoptosis. We observed that APR-246 synergistically enhanced the cytotoxic response of olaparib in TP53 mutant non-small cell lung cancer cell lines, resulting in a strong apoptotic response. In the presence of wild type p53 a G2/M cell cycle block was predominantly observed. NOXA expression levels were significantly increased in a TP53 mutant background, and remained unchanged in the wild type cell line. The combined treatment of APR-246 and olaparib induced cell death that was associated with increased ROS production, accumulation of DNA damage and translocation of p53 to the mitochondria. Out data suggest a promising targeted combination strategy in which the response to olaparib is synergistically enhanced by the addition of APR-246, especially in a TP53 mutant background.

Onartuzumab in lung cancer: the fall of Icarus?

The development of targeted therapies has led to a revolution in non-small-cell lung cancer, and opened up possibilities for improved personalized medicine. With the constant findings of new targets, a lot of inhibitors are being developed. However, reliable biomarkers are urgently needed. The design of clinical trials needs to become more flexible in order to obtain the best results and gain the US FDA/EMEA approval for the new drugs. A recent example of a failed trial is the Phase III MetLung trial that compared the effects of the c-MET monovalent antibody onartuzumab with erlotinib versus erlotinib alone in late-stage non-small-cell lung cancer. Here, we discuss several points as to why this trial could have failed.

cMET in NSCLC: Can We Cut off the Head of the Hydra? From the Pathway to the Resistance.

In the last decade, the tyrosine kinase receptor cMET, together with its ligand hepatocyte growth factor (HGF), has become a target in non-small cell lung cancer (NSCLC). Signalization via cMET stimulates several oncological processes amongst which are cell motility, invasion and metastasis. It also confers resistance against several currently used targeted therapies, e.g., epidermal growth factor receptor (EGFR) inhibitors. In this review, we will discuss the basic structure of cMET and the most important signaling pathways. We will also look into aberrations in the signaling and the effects thereof in cancer growth, with the focus on NSCLC. Finally, we will discuss the role of cMET as resistance mechanism.

The role of cMet in non-small cell lung cancer resistant to EGFR-inhibitors: did we really find the target?

The advent of the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) represented the most important innovation in NSCLC treatment over the last years. However, despite a great initial activity, secondary mutations in the same target, or different alterations in other molecular pathways, inevitably occur, leading to the emergence of acquired resistance, in median within the first year of treatment. In this scenario, the mesenchymal-epidermal transition (cMET) tyrosine kinase receptor and its natural ligand, the hepatocyte growth factor (HGF), seem to play an important role. Indeed either the overexpression or the amplification of cMET, as well as the overexpression of the HGF, have been reported in a substantial subgroup of NSCLC patients resistant to EGFR-TKIs. Several cMET-inhibitors have been developed as potential therapeutic candidates, and are currently under investigation in clinical trials. These compounds include both monoclonal antibodies and TKIs, and most of them have been investigated as dual combinations including an anti-EGFR TKI, to improve the efficacy of the available treatments, and ultimately overcome acquired resistance to EGFR-inhibitors.