Comparison of different semi-automated cfDNA extraction methods in combination with UMI-based targeted sequencing

The analysis of circulating cell-free DNA (cfDNA) extracted from peripheral blood can serve as a minimally invasive alternative to tumor tissue biopsies in cases with impaired access to tissue. Its clinical utility has been well demonstrated for EGFR T790M testing in lung cancer patients suffering progress after tyrosine kinase inhibitor treatment. At present, highly sensitive unique molecular identifiers (UMI)-based NGS for liquid biopsy testing is less established compared to single gene assays. However, the critical bottleneck are sufficient cfDNA yields, which are essentially required to obtain meaningful test results.

We compared four different cfDNA extraction methods (Qiagen, Promega, Thermo and Stratec) using the same plasma samples in order to evaluate their suitability for further NGS analysis. We managed to draw 60 ml blood from 12 patients each and equally collected 30ml in PAXgene and EDTA tubes at the same time point, sufficient for total of 96 cfDNA extractions. CfDNA concentrations and total amounts were highest for Qiagen and Promega protocols, showing the best read length profiles after sequencing.

Known oncogenic driver mutations were identified in 9 out of 12 patients with at least one of the cfDNA extraction methods, again favoring the extraction protocols from Qiagen and Promega. We also uncovered putative sequencing artefacts including known driver genes pointing to a careful consideration for the limit of detection of this methodology. Our study shows that pre-analytical optimization is necessary to achieve the maximum sensitivity of UMI-based sequencing but also highlights the low abundance of tumor-derived cfDNA in lung cancer samples.

EGFR mutation decreases FDG uptake in non‑small cell lung cancer via the NOX4/ROS/GLUT1 axis

[18F]fluoro‑2‑deoxyglucose (FDG) positron emission tomography (PET)‑computed tomography (CT) is a functional imaging modality based on glucose metabolism. The association between the maximum standardized uptake value (SUVmax) from 18F‑FDG PET‑CT scanning and epidermal growth factor receptor (EGFR) mutation status has, to the best of our knowledge, not previously been fully elucidated, and the potential mechanisms by which EGFR mutations alter FDG uptake are largely unknown. A total of 157 patients who were pathologically diagnosed with non‑small cell lung cancer (NSCLC) who underwent EGFR mutation testing and PET‑CT pretreatment between June 2015 and October 2017 were retrospectively analyzed. χ2 and univariate analyses were performed to identify the contributors to EGFR mutation. The receiver operating characteristic (ROC) curve was analyzed, and the area under the curve (AUC) was calculated. Glucose transporter 1 (GLUT1) and NADPH oxidase 4 (NOX4) expression, and reactive oxygen species (ROS) activity were detected in the A549 (wild‑type), PC‑9 (EGFR mutation‑positive, EGFR exon 19del) and NCI‑H1975 (EGFR mutation‑positive, combined with L858R and T790M substitution) cell lines. A total of 109 patients who met the criteria were enrolled, and 63 of those tested as EGFR mutation‑positive. The SUVmax values were significantly lower in patients with EGFR mutations (mean, 6.52±0.38) compared with in patients with wild‑type EGFR (mean, 9.37±0.31; P<0.001). Using univariate analysis, EGFR mutation status was significantly associated with sex, smoking status, tumor histology and SUVmax of the primary tumor. In the multivariate analysis, smoking status (never‑smoking), histopathology (adenocarcinoma) and SUVmax (≤9.91) were the statistically significant predictors of EGFR mutations. ROC curve analysis identified that the SUVmax cut‑off point was 9.92, for which the AUC was 0.75 (95% confidence interval, 0.68‑0.83). Reverse transcription‑polymerase chain reaction indicated that the GLUT1 mRNA decreased in the PC‑9 and NCI‑H1975 cell lines compared with the A549 cell line (0.82±0.07 and 0.72±0.04 vs. 0.98±0.04, respectively; P<0.05) and decreased ROS activity was observed in the PC‑9 cell line. Furthermore, the expression of NOX4 mRNA decreased by 20% in PC‑9 (P<0.01) and by 14% (P<0.05) in NCI‑H1975 cells. In addition, NOX4 protein expression decreased by 13% in PC‑9 and by 16% in NCI‑H1975 cells (both P<0.05) compared with the A549 cell line. The SUVmax could be considered to effectively predict EGFR mutation status of patients with NSCLC, and the EGFR mutation status may alter FDG uptake partially via the NOX4/ROS/GLUT1 axis.

Targeting autophagy sensitises lung cancer cells to Src family kinase inhibitors

Lung cancer is the main cancer killer in both men and women, mostly due to the rapid development of drug resistant metastatic disease. Here, we evaluate the potential involvement of SRC family kinases (SFK) in lung cancer biology and assess the possible benefits of their inhibition as a therapeutic approach. We demonstrated that various SRC family members, including LYN and LCK, normally expressed solely in hematopoietic cells and neural tissues, are overexpressed and activated in a panel of SCLC and NSCLC cell lines. This was clinically relevant as LYN and FYN are also overexpressed in lung cancer clinical specimens. Moreover, LYN overexpression correlated with decreased patient survival on univariate and multivariate analysis. Dasatinib (BMS-354825), a SRC/ABL inhibitor, effectively blocked SFK activation at nanomolar concentrations which correlated with a significant decrease in cell numbers of multiple lung cancer cell lines. This effect was matched by a decrease in DNA synthesis, but only moderate induction of apoptosis. Indeed, dasatinib as well as PP2, another SFK inhibitor, strongly induced autophagy that likely prevented apoptosis. However, inhibition of this autophagic response induced robust apoptosis and sensitised lung cancer cells to dasatinib in vitro and in vivo. Our results provide an explanation for why dasatinib failed in NSCLC clinical trials. Furthermore, our data suggest that combining SFK inhibitors with autophagy inhibitors could provide a novel therapeutic approach in this disease.

Liquid biopsy for lung cancer early detection

Molecularly targeted therapies and immune checkpoint inhibitors have markedly improved the therapeutic management of advanced lung cancer. However, it still remains the leading cause of cancer-related mortality worldwide, with disease stage at diagnosis representing the main prognostic factor. Detection of lung cancer at an earlier stage of disease, potentially susceptible of curative resection, can be critical to improve patients survival. Low-dose computed tomography (LDCT) screening of high-risk patients has been demonstrated to reduce mortality from lung cancer, but can be also associated with high false-positive rate, thus often resulting in unnecessary interventions for patients. Novel sensitive and specific biomarkers for identification of high-risk subjects and early detection that can be used alternatively and/or complement current routine diagnostic procedures are needed. Liquid biopsy has recently demonstrated its clinical usefulness in advanced NSCLC as a surrogate of tissue biopsy for noninvasive assessment of specific genomic alterations, thereby providing prognostic and predictive information. Different biosources from liquid biopsy, including cell free circulating tumor DNA (ctDNA), circulating tumor cells (CTCs), exosomes and tumor-educated platelets (TEPs), have also been widely investigated for their potential role in lung cancer diagnosis. This review will provide an overview on the circulating biomarkers being evaluated for lung cancer detection, mainly focusing on results from most recent studies, the techniques developed to perform their assessment in blood and other biologic fluids and challenges in their clinical applications.

5'-nucleotidase cN-II emerges as a new predictive biomarker of response to gemcitabine/platinum combination chemotherapy in non-small cell lung cancer

A number of pharmacogenetic studies have been carried out in non-small-cell lung cancer (NSCLC) to identify and characterize genes involved in chemotherapy activity. However, the results obtained so far are controversial and no reliable biomarker is currently used to predict clinical benefit from platinum-based chemotherapy, which represents the cornerstone of treatment of advanced NSCLC. This study investigated the expression levels of ERCC1 and of six genes (RRM1, RRM2, hENT1, dCK, cN-II and CDA) involved in gemcitabine metabolism in locally/advanced NSCLC patients treated with gemcitabine/platinum combination. Gene expression was assessed by quantitative-PCR in laser-microdissected specimens and correlated with tumor response. Frequency distribution of responses above and below the median expression level of biomarkers was compared using a two-sided Fisher’s test. 5′-nucleotidase (cN-II) was the only gene differently expressed (p = 0.016) in the responders (complete/partial-response) compared to non-responders (stable/progressive disease). In the multivariate analysis, overexpression of this catabolic enzyme of gemcitabine remained a significant negative predictive factor. Patients with low cN-II had a modest trend toward increased survival, while both survival and progression-free survival were significantly longer in a more homogenous validation cohort of 40 advanced NSCLC (8.0 vs. 5.1 months, p = 0.026). Moreover, in vitro studies showed that silencing or pharmacological inhibition of cN-II increased the cytotoxicity of gemcitabine. This is the first study demonstrating the role of cN-II as a predictor of response to gemcitabine/platinum combinations in NSCLC. Its validation in prospective studies may improve clinical outcome of selected patients.

Spotlight on ceritinib in the treatment of ALK+ NSCLC: design, development and place in therapy

The identification of echinoderm microtubule-associated protein-like 4 (EML4) and anaplastic lymphoma kinase (ALK) fusion gene in non-small cell lung cancer (NSCLC) has radically changed the treatment of a subset of patients harboring this oncogenic driver. Crizotinib was the first ALK tyrosine kinase inhibitor to receive fast approval and is currently indicated as the first-line therapy for advanced, ALK-positive NSCLC patients. However, despite crizotinib's efficacy, patients almost invariably progress, with the central nervous system being one of the most common sites of relapse. Different mechanisms of acquired resistance have been identified, including secondary ALK mutations, ALK copy number alterations and activation of bypass tracks. Different highly potent and brain-penetrant next-generation ALK inhibitors have been developed and tested in NSCLC patients with ALK rearrangements. Ceritinib, a structurally distinct and selective ALK inhibitor, showed 20 times higher potency than crizotinib in inhibiting ALK and had activity against the most common crizotinib-resistant mutations, including L1196M and G1269A, in preclinical models. In Phase I and II studies, ceritinib demonstrated pronounced activity in both crizotinib-naïve and crizotinib-refractory patients, with responses observed regardless of the presence of ALK resistance mutations. Ceritinib was the first ALK inhibitor to be approved for the treatment of crizotinib-refractory, ALK-rearranged NSCLC, and recent results from a Phase III study have demonstrated superior efficacy compared to standard chemotherapy in the first- and second-line setting. We provide an extensive overview of ceritinib from the design of the compound through preclinical data until efficacy and toxicity results from Phase I-III clinical studies. We review the molecular alterations associated with resistance to ceritinib and highlight the importance of obtaining tumor biopsy at progression to tailor therapy based upon the underlying resistance mechanism. We finally provide an outlook on novel rational therapeutic combinations.

Second-line therapy of squamous non-small cell lung cancer: an evolving landscape

INTRODUCTION

The treatment of lung cancer has radically changed over the last few years. The discovery of druggable oncogenic alterations and the introduction of immunotherapy have provided lung cancer patients with the possibility of more efficient and less toxic therapeutic alternatives than chemotherapy. In the case of lung squamous cell carcinoma (LSCC), the treatment progress is slower than adenocarcinoma, for which several targeted agents have been already approved. The standard first-line therapy for LSCC, in most sites of the world, is platinum-based chemotherapy. After disease progression, these patients now have novel treatment options, including antiangiogenic agents and immune checkpoint blockade. Areas covered: We provide a summary of the recent novelties for the second-line therapy of LSCC, emphasizing on the results of the most important clinical trials that have led to regulatory approvals. Expert commentary: Immune checkpoint inhibitors have changed the therapeutic algorithm for LSCC patients. Other treatment options in the second-line setting include ramucirumab in combination with docetaxel and afatinib. However, we still lack biomarkers to predict which patients could respond better to each treatment. Despite the identification of several actionable molecular alterations, there are no approved targeted agents specific for advanced LSCC. Results from ongoing biomarker-driven studies are eagerly awaited to establish effective treatments for molecularly selected subgroups of patients.

Clinical and pathological characteristics of EGFR mutation in operable early-stage lung adenocarcinoma

OBJECTIVES

Over the past decade, the biological and clinical characteristics of lung cancer with epidermal growth factor receptor (EGFR) mutation have been well studied. However, most studies have focused on advanced inoperable cancer, and not on resected early-stage lung adenocarcinoma. We aimed to elucidate the differences in the clinicopathological characteristics and postoperative prognosis according to the EGFR mutation status in early-stage lung adenocarcinoma.

MATERIALS AND METHODS

We retrospectively collected clinical and pathological data from 369 patients with pathological stage I or II lung adenocarcinoma who underwent complete resection. Clinicopathological characteristics and postoperative prognosis were compared depending on the EGFR mutation status, using the Chi-squared test and the log-rank test, respectively.

RESULTS AND CONCLUSION

Of the 369 patients, 160 (43.3%) had EGFR mutation, of which 64 (40.0%) were exon 19 deletion (Del-19) and 90 (56.3%) were exon 21 point mutation L858R. Although there was no difference in overall survival (OS) between patients with and without EGFR mutation (p=0.086), tumors with EGFR mutation were associated with a lower consolidation to tumor ratio (CTR) (p <0.001) and a higher incidence of a lepidic growth pattern by pathological evaluation (p <0.001) compared to those without EGFR mutation. Among tumors with EGFR mutation, there was no difference in OS (p=0.140) between Del-19 and L858R. Tumors with L858R were associated with a lower CTR (p=0.046), and tended to have a higher incidence of a lepidic growth pattern by pathological evaluation (p=0.073) compared to those with Del-19. In conclusion, although EGFR mutation status was not a prognostic indicator after surgery in early-stage lung adenocarcinoma, L858R and Del-19 had different radiological and pathological features.

Historical Evolution of Second-Line Therapy in Non-Small Cell Lung Cancer

Innovative therapeutic agents have significantly improved outcome with an acceptable safety profile in a substantial proportion of non-small cell lung cancer (NSCLC) patients, who depend on oncogenic molecular alterations for their malignant phenotype. Despite the survival improvement achieved with first-line chemotherapy, about 30% of patients do not obtain a tumor response. Moreover, those patients, initially sensitive to treatment, acquire resistance and develop tumor progression after a median of about 5 months. Approximately 60% of the patients progressing from first-line chemotherapy receive further systemic treatment in the second-line setting. Moreover, new options have emerged in the second-line armamentarium for the treatment of patients with NSCLC, including immune checkpoint inhibitors and antiangiogenic agents. The current review provides an overview on the clinical studies that gained the approval of chemotherapy agents (docetaxel and pemetrexed) and epidermal growth factor receptor gene–tyrosine kinase inhibitors as second-line treatment options for NSCLC patients, not carrying molecular alterations.

Comparison of plasma and tissue samples in epidermal growth factor receptor mutation by ARMS in advanced non-small cell lung cancer

OBJECTIVE

The aim of this study was to assess the effectiveness and accuracy of blood-based circulating-free tumor DNA on testing epidermal growth factor receptor (EGFR) gene mutations.

METHODS

In total, 219 non-small cell lung cancer patients in stages III-IV were enrolled into this study. All patients had tissue samples and matched plasma DNA samples. EGFR gene mutations were detected by the Amplification Refractory Mutation System (ARMS). We compared the mutations in tumor tissue samples with matched plasma samples and determined the correlation between EGFR mutation status and clinical pathologic characteristics.

RESULT

The overall concordance rate of EGFR mutation status between the 219 matched plasma and tissue samples was 82% (179/219). The sensitivity and specificity for the ARMS EGFR mutation test in the plasma compared with tumor tissue were 60% (54/90) and 97% (125/129), respectively. The positive predictive value was 93% (54/58) and the negative predictive value was 78% (125/161). The median overall survival was longer for those with EGFR mutations than for those without EGFR mutations both in tissue samples (23.98 vs. 12.16months; P<0.001) and in plasma (19.96 vs. 13.63months; P=0.009). For the 68 patients treated with EGFR- tyrosine kinase inhibitors (TKIs), the median progression-free survival (PFS) was significantly prolonged in the EGFR mutant group compared to the non-mutation group in tumor tissue samples (12.26months vs. 2.40months, P<0.001). In plasma samples, the PFS of the mutant group was longer than that of the non-mutant group. However, there was no significant difference between the two groups (10.88months vs. 9.89months, P=0.411).

CONCLUSIONS

The detection of EGFR mutations in plasma using ARMS is relatively sensitive and highly specific. However, EGFR mutation status tested by ARMS in plasma cannot replace a tumor tissue biopsy. Positive EGFR mutation results detected in plasma are fairly reliable, but negative results are hampered by a high rate of false negatives.

Personalized treatment of early-stage non-small-cell lung cancer: the challenging role of EGFR inhibitors

Adjuvant cisplatin-based chemotherapy significantly improves outcomes of completely resected early-stage non-small-cell lung cancer (NSCLC) patients. However, its effect on overall survival is limited and may be unsuitable for many patients due to toxicity. Targeted therapies and individualization of adjuvant treatment offer the potential to improve curability and extend survival of these patients while decreasing toxicity. Here we review Phase II and III studies examining the role of EGF receptor inhibitors, including tyrosine kinase inhibitors and the monoclonal antibody cetuximab, as adjuvant therapy in resected patients or as part of multimodality treatment for stage III NSCLC. Recent results from genotype-directed adjuvant tyrosine kinase inhibitors trials including early-stage NSCLC patients with EGFR mutations are promising, but more data are needed to support their use in this setting.

Strategies to overcome resistance to tyrosine kinase inhibitors in non-small-cell lung cancer

The use of molecularly targeted agents has dramatically improved the prognosis of defined subsets of patients with non-small-cell lung cancer harboring somatically activated oncogenes, such as mutant EGFR or rearranged ALK. However, after initial marked responses to EGFR or ALK tyrosine kinase inhibitors (TKIs), almost all patients inevitably progress due to development of acquired resistance. Multiple molecular mechanisms of resistance have been identified; the best characterized are secondary mutations in the tyrosine kinase domain of the oncogene, such as T790M in EGFR and L1196M in ALK, which prevent target inhibition by the corresponding TKI. Other mechanisms include copy number gain of the ALK fusion gene and the activation of bypass signaling pathways that can maintain downstream proliferation and survival signals despite inhibition of the original drug target. Here, the authors provide an overview of the known mechanisms of resistance to TKIs and outline the therapeutic strategies, including new investigational agents and targeted therapies combinations, that have been developed to overcome resistance.

Copy number gains of FGFR1 and 3q chromosome in squamous cell carcinoma of the lung

Squamous cell carcinoma of the lung (SQCCL) remains a leading cause of cancer-related death. Unlike non-smoker adenocarcinoma of the lung, where highly efficient tyrosine kinase inhibitors are available for treating mutant EGFR or ALK-rearranged, no targetable biomarkers are available for SQCCL. The frequent and focal amplification of FGFR1 has generated great expectations in offering new therapeutical options in case of 16-22% of SQCCL patients. Broad 3q chromosome amplification is widely recognized as the most common chromosomal aberration found in SQCCL, where PIK3CA, SOX2, ACK1, PRKCI, TP63, PLD1, ECT2, and others genes are located. Although SOX2 has been postulated as a key regulator of basal stem cells transformation and tumor progression, it seems to confer a good prognosis in SQCCL. It is known that each patient might carry a different length of 3q chromosome amplicon. Thus, we suggest that the number and the biological importance of the genes spanned along each patient's 3q amplicon might help to explain inter-individual outcome variations of the disease and its potential predictive value, especially when relevant oncogenes such as those mentioned above are implicated. Currently, there is no clinical predictive data available from clinical trials. In this review, we have focused on the potential role of FGFR1 in SQCCL prognosis. Additionally, we have explored recently available public data on the comprehensive genomic characterization of SQCCL, in relation to the protein-coding genes that have a strong gene copy number - mRNA correlation in 3q chromosome, that were previously described as potential driver oncogenes or its modifiers in SQCCL.

Axl as a mediator of cellular growth and survival

The control of cellular growth and proliferation is key to the maintenance of homeostasis. Survival, proliferation, and arrest are regulated, in part, by Growth Arrest Specific 6 (Gas6) through binding to members of the TAM receptor tyrosine kinase family. Activation of the TAM receptors leads to downstream signaling through common kinases, but the exact mechanism within each cellular context varies and remains to be completely elucidated. Deregulation of the TAM family, due to its central role in mediating cellular proliferation, has been implicated in multiple diseases. Axl was cloned as the first TAM receptor in a search for genes involved in the progression of chronic to acute-phase leukemia, and has since been established as playing a critical role in the progression of cancer. The oncogenic nature of Axl is demonstrated through its activation of signaling pathways involved in proliferation, migration, inhibition of apoptosis, and therapeutic resistance. Despite its recent discovery, significant progress has been made in the development of effective clinical therapeutics targeting Axl. In order to accurately define the role of Axl in normal and diseased processes, it must be analyzed in a cell type-specific context.

Peripheral blood for epidermal growth factor receptor mutation detection in non-small cell lung cancer patients

OBJECTIVE: It is important to analyze and track Epidermal Growth Factor Receptor (EGFR) mutation status for predicting efficacy and monitoring resistance throughout EGFR-tyrosine kinase inhibitors (TKIs) treatment in non-small cell lung cancer (NSCLC) patients. The objective of this study was to determine the feasibility and predictive utility of EGFR mutation detection in peripheral blood. METHODS: Plasma, serum and tumor tissue samples from 164 NSCLC patients were assessed for EGFR mutations using Amplification Refractory Mutation System (ARMS). RESULTS: Compared with matched tumor tissue, the concordance rate of EGFR mutation status in plasma and serum was 73.6% and 66.3%, respectively. ARMS for EGFR mutation detection in blood showed low sensitivity (plasma, 48.2%; serum, 39.6%) but high specificity (plasma, 95.4%; serum, 95.5%). Treated with EGFR-TKIs, patients with EGFR mutations in blood had significantly higher objective response rate (ORR) and insignificantly longer progression-free survival (PFS) than those without mutations (ORR: plasma, 68.4% versus 38.9%, P = 0.037; serum, 75.0% versus 39.5%, P = 0.017; PFS: plasma, 7.9 months versus 6.1 months, P = 0.953; serum, 7.9 months versus 5.7 months, P = 0.889). In patients with mutant tumors, those without EGFR mutations in blood tended to have prolonged PFS than patients with mutations (19.7 months versus 11.0 months, P = 0.102). CONCLUSIONS: EGFR mutations detected in blood may be highly predictive of identical mutations in corresponding tumor, as well as showing correlations with tumor response and survival benefit from EGFR-TKIs. Therefore, blood for EGFR mutation detection may allow NSCLC patients with unavailable or insufficient tumor tissue the opportunity to benefit from personalized treatment. However, due to the high false negative rate in blood samples, analysis for EGFR mutations in tumor tissue remains the gold standard.

Prospects for population screening and diagnosis of lung cancer

Deaths from lung cancer exceed those from any other type of malignancy, with 1·5 million deaths in 2010. Prevention and smoking cessation are still the main methods to reduce the death toll. The US National Lung Screening Trial, which compared CT screening with chest radiograph, yielded a mortality advantage of 20% to participants in the CT group. International debate is ongoing about whether sufficient evidence exists to implement CT screening programmes. When questions about effectiveness and cost-effectiveness have been answered, which will await publication of the largest European trial, NELSON, and pooled analysis of European CT screening trials, we discuss the main topics that will need consideration. These unresolved issues are risk prediction models to identify patients for CT screening; radiological protocols that use volumetric analysis for indeterminate nodules; options for surgical resection of CT-identified nodules; screening interval; and duration of screening. We suggest that a demonstration project of biennial screening over a 4-year period should be undertaken.

Moving towards molecular-guided treatments: erlotinib and clinical outcomes in non-small-cell lung cancer patients

Erlotinib is an orally administered small-molecule inhibitor of EGF receptor (EGFR) tyrosine kinase that is approved for the treatment of non-small-cell lung cancer (NSCLC) and pancreatic cancer. Erlotinib was first approved for the treatment of unselected NSCLC patients with advanced disease after failure of at least one prior chemotherapy regimen, and it was subsequently demonstrated to also confer a significant clinical benefit as maintenance therapy after first-line platinum-based chemotherapy. In all clinical studies, erlotinib treatment was associated with a good safety profile. Activating mutations in the EGFR gene have emerged as the strongest predictive marker of response to tyrosine kinase inhibitors, erlotinib and gefitinib, independently of other clinical and molecular features. Results from recently published, randomized Phase III trials showed that first-line erlotinib significantly prolongs progression-free survival in patients with advanced EGFR mutation-positive NSCLC with favorable tolerability, compared with standard chemotherapy. EGFR mutation testing is a crucial factor in the decision-making process regarding the most appropriate initial treatment option for patients. Specific molecular alterations in crucial genes have been discovered and associated with resistance to erlotinib, limiting its efficacy. New targeted agents and combined-treatment strategies are now under evaluation in clinical trials of NSCLC patients following progression to tyrosine kinase inhibitors.

USP8 is a novel target for overcoming gefitinib resistance in lung cancer

PURPOSE

Common treatment modalities for non-small cell lung cancer (NSCLC) involve the EGF receptor-tyrosine kinase inhibitors (EGFR-TKIs) like gefitinib and erlotinib. However, the vast majority of treated patients acquire resistance to EGFR-TKIs, due, in large part, to secondary mutations in EGFR or amplification of the MET gene. Our purpose was to test ubiquitin-specific peptidase 8 (USP8) as a potential therapeutic target for gefitinib-resistant and -sensitive non-small cell lung cancer (NSCLC).

EXPERIMENTAL DESIGN

Testing the effect of knockdown of USP8 and use of a synthetic USP8 inhibitor to selectively kill gefitinib-resistant (or -sensitive) NSCLCs with little effect on normal cells in cell culture and a xenograft mouse model.

RESULTS

Knockdown of ubiquitin-specific peptidase 8 (USP8) selectively kills gefitinib-resistant NSCLCs while having little toxicity toward normal cells. Genetic silencing of USP8 led to the downregulation of several receptor tyrosine kinases (RTK) including EGFR, ERBB2, ERBB3, and MET. We also determined that a synthetic USP8 inhibitor markedly decreased the viability of gefitinib-resistant and -sensitive NSCLC cells by decreasing RTK expression while having no effect on normal cells. Moreover, treatment with a USP8 inhibitor led to significant reductions in tumor size in a mouse xenograft model using gefitinib-resistant and -sensitive NSCLC cells.

CONCLUSIONS

Our results show for the first time that the inhibition of USP8 activity or reduction in USP8 expression can selectively kill NSCLC cells. We propose USP8 as a potential therapeutic target for gefitinib-resistant and -sensitive NSCLC cells.