Combined effect of cabozantinib and gefitinib in crizotinib-resistant lung tumors harboring ROS1 fusions

The Adverse Impact of Tyrosine Kinase Inhibitors on Wound Healing and Repair

Tyrosine kinase inhibitors (TKIs) can treat various cancers, primarily through their antiangiogenic effects. However, as angiogenesis is crucial for successful wound healing, TKIs may adversely impact wound repair. This review analysed all 63 FDA-approved TKIs and identified evidence for wound healing and repair implications in 24 agents. The primary mechanism contributing to impaired wound healing appears to be the inhibition of vascular endothelial growth factor receptors, with secondary targets, such as epidermal growth factor receptors and platelet-derived growth factor receptors, potentially playing a role. Information from safety package inserts, preclinical studies, case reports and clinical trials suggests that these TKIs can cause delayed or impaired wound healing. The safety information generally recommends discontinuing treatment for at least one to 2 weeks before elective surgery and resuming treatment only after adequate wound healing has occurred. Neoadjuvant therapy with TKIs may be feasible if sufficient time is allowed between the cessation of the TKI and the onset of surgery. As the use of TKIs continues to increase, healthcare professionals should be aware of their potential impact on wound healing and take appropriate precautions to minimise the risk of wound-related complications.

Targeting of arachidonic acid-modulated autophagy to enhance the sensitivity of ROS1 + or ALK + non-small cell lung cancer to crizotinib therapy

Background

As an approved targeting drug, crizotinib has been widely used in the treatment of patients with non-small cell lung cancer (NSCLC) with anaplastic lymphoma kinase (ALK) rearrangements or c-ros oncogene 1 (ROS1) fusions and has demonstrated remarkable therapeutic effects. However, crizotinib-treated patients frequently experience drug resistance, and there are still some underlying mechanisms, which remain unclear. Autophagy, a cellular process that involves the degradation and recycling of cellular components, has been implicated in the development of drug resistance. In this study, we aim to elucidate the mechanisms of crizotinib resistance involving autophagy dysregulation and identify novel therapeutic targets to overcome this resistance.

Methods

We first established a model for crizotinib resistance in HCC78 and H3122 cells. Next, the level of proliferation, apoptosis, autophagy flux, and reactive oxygen species (ROS) of these cells were measured. Subsequently, we analyzed the published single-cell RNA sequencing data from three ALK-rearranged lung cancer organoid samples and performed a metabolomics assay on crizotinib-resistant HCC78 cells. Finally, the therapeutic effects were confirmed in vitro by targeting autophagy flux.

Results

Crizotinib induced cell apoptosis and growth arrest by promoting the accumulation of autophagosomes through the inhibition of autophagy flux in ROS1 + or ALK + NSCLC. In contrast, crizotinib-resistant NSCLC cells showed inactivation of signal transducer and activator of transcription 3 (STAT3) phosphorylation and downregulation of prostaglandin endoperoxide synthase 2 (PTGS2), leading to an increase in the metabolite arachidonic acid (AA). AA further promoted autophagy flux and reduced autophagosome accumulation, driving crizotinib resistance under conditions of drug stress. Moreover, chloroquine (CQ), anti-malaria drug and lysosome inhibitor developed in 1940, could induce cell death in crizotinib-resistant NSCLC by blocking AA-mediated autophagy flux and facilitating autophagosome accumulation, significantly enhancing the treatment efficacy of crizotinib in drug-resistant NSCLC.

Conclusions

We discovered a new mechanism of first generation ALK- and ROS1-TKIs resistance, which points to the role of the metabolite AA in resistance to tyrosine kinase inhibitors. It may potentially provide an alternative strategy to overcoming crizotinib resistance in NSCLC treatment by reversing AA-mediated autophagy.

AXL signaling in cancer: from molecular insights to targeted therapies

AXL, a member of the TAM receptor family, has emerged as a potential target for advanced-stage human malignancies. It is frequently overexpressed in different cancers and plays a significant role in various tumor-promoting pathways, including cancer cell proliferation, invasion, metastasis, epithelial-mesenchymal transition (EMT), angiogenesis, stemness, DNA damage response, acquired therapeutic resistance, immunosuppression, and inflammatory responses. Beyond oncology, AXL also facilitates viral infections, including SARS-CoV-2 and Zika highlighting its importance in both cancer and virology. In preclinical models, small-molecule kinase inhibitors targeting AXL have shown promising anti-tumorigenic potential. This review primarily focuses on the induction, regulation and biological functions of AXL in mediating these tumor-promoting pathways. We discuss a range of therapeutic strategies, including recently developed small-molecule tyrosine kinase inhibitors (TKIs), monoclonal antibodies, and antibody-drug conjugates (ADCs), anti-AXL-CAR, and combination therapies. These interventions are being examined in both preclinical and clinical studies, offering the potential for improved drug sensitivity and therapeutic efficacy. We further discuss the mechanisms of acquired therapeutic resistance, particularly the crosstalk between AXL and other critical receptor tyrosine kinases (RTKs) such as c-MET, EGFR, HER2/HER3, VEGFR, PDGFR, and FLT3. Finally, we highlight key research areas that require further exploration to enhance AXL-mediated therapeutic approaches for improved clinical outcomes.

Current treatment and novel insights regarding ROS1-targeted therapy in malignant tumors

BACKGROUND

The proto-oncogene ROS1 encodes an intrinsic type I membrane protein of the tyrosine kinase/insulin receptor family. ROS1 facilitates the progression of various malignancies via self-mutations or rearrangements. Studies on ROS1-directed tyrosine kinase inhibitors have been conducted, and some have been approved by the FDA for clinical use. However, the adverse effects and mechanisms of resistance associated with ROS1 inhibitors remain unknown. In addition, next-generation ROS1 inhibitors, which have the advantage of treating central nervous system metastases and alleviating endogenous drug resistance, are still in the clinical trial stage.

METHOD

In this study, we searched relevant articles reporting the mechanism and clinical application of ROS1 in recent years; systematically reviewed the biological mechanisms, diagnostic methods, and research progress on ROS1 inhibitors; and provided perspectives for the future of ROS1-targeted therapy.

RESULTS

ROS1 is most expressed in malignant tumours. Only a few ROS1 kinase inhibitors are currently approved for use in NSCLC, the efficacy of other TKIs for NSCLC and other malignancies has not been ascertained. There is no effective standard treatment for adverse events or resistance to ROS1-targeted therapy. Next-generation TKIs appear capable of overcoming resistance and delaying central nervous system metastasis, but with a greater incidence of adverse effects.

CONCLUSIONS

Further research on next-generation TKIs regarding the localization of ROS1 and its fusion partners, binding sites for targeted drugs, and coadministration with other drugs is required. The correlation between TKIs and chemotherapy or immunotherapy in clinical practice requires further study.

CRISPR/Cas9-edited ROS1 + non-small cell lung cancer cell lines highlight differential drug sensitivity in 2D vs 3D cultures while reflecting established resistance profiles

INTRODUCTION

The study of resistance-causing mutations in oncogene-driven tumors is fundamental to guide clinical decisions. Several point mutations affecting the ROS1 kinase domain have been identified in the clinical setting, but their impact requires further exploration, particularly in improved pre-clinical models. Given the scarcity of solid pre-clinical models to approach rare cancer subtypes like ROS1 + NSCLC, CRISPR/Cas9 technology allows the introduction of mutations in patient-derived cell lines for which resistant variants are difficult to obtain due to the low prevalence of cases within the clinical setting.

METHODS

In the SLC34A2-ROS1 rearranged NSCLC cell line HCC78, we knocked-in through CRISPR/Cas9 technology three ROS1 drug resistance-causing mutations: G2032R, L2026M and S1986Y. Such variants are located in different functional regions of the ROS1 kinase domain, thus conferring TKI resistance through distinct mechanisms. We then performed pharmacological assays in 2D and 3D to assess the cellular response of the mutant lines to crizotinib, entrectinib, lorlatinib, repotrectinib and ceritinib. In addition, immunoblotting assays were performed in 2D-treated cell lines to determine ROS1 phosphorylation and MAP kinase pathway activity. The area over the curve (AOC) defined by the normalized growth rate (NGR_fit) dose-response curves was the variable used to quantify the cellular response towards TKIs.

RESULTS

Spheroids derived from ROS1G2032R cells were significantly more resistant to repotrectinib (AOC fold change = - 7.33), lorlatinib (AOC fold change = - 6.17), ceritinib (AOC fold change = - 2.8) and entrectinib (AOC fold change = - 2.02) than wild type cells. The same cells cultured as a monolayer reflected the inefficacy of crizotinib (AOC fold change = - 2.35), entrectinib (AOC fold change = - 2.44) and ceritinib (AOC fold change = - 2.12) in targeting the ROS1 G2032R mutation. ROS1L2026M cells showed also remarkable resistance both in monolayer and spheroid culture compared to wild type cells, particularly against repotrectinib (spheroid AOC fold change = - 2.19) and entrectinib (spheroid AOC fold change = - 1.98). ROS1S1986Y cells were resistant only towards crizotinib in 2D (AOC fold change = - 1.86). Overall, spheroids showed an increased TKI sensitivity compared to 2D cultures, where the impact of each mutation that confers TKI resistance could be clearly distinguished. Western blotting assays qualitatively reflected the patterns of response towards TKI observed in 2D culture through the levels of phosphorylated-ROS1. However, we observed a dose-response increase of phosphorylated-Erk1/2, suggesting the involvement of the MAPK pathway in the mediation of apoptosis in HCC78 cells.

CONCLUSION

In this study we knock-in for the first time in a ROS1 + patient-derived cell line, three different known resistance-causing mutations using CRISPR/Cas9 in the endogenous translocated ROS1 alleles. Pharmacological assays performed in 2D and 3D cell culture revealed that spheroids are more sensitive to TKIs than cells cultured as a monolayer. This direct comparison between two culture systems could be done thanks to the implementation of normalized growth rates (NGR) to uniformly quantify drug response between 2D and 3D cell culture. Overall, this study presents the added value of using spheroids and positions lorlatinib and repotrectinib as the most effective TKIs against the studied ROS1 resistance point mutations.

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 modelling of ROS1+ non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is a heterogeneous group of diseases which accounts for 80% of newly diagnosed lung cancers. In the previous decade, a new molecular subset of NSCLC patients (around 2%) harboring rearrangements of the c-ros oncogene 1 was defined. ROS1+ NSCLC is typically diagnosed in young, nonsmoker individuals presenting an adenocarcinoma histology. Patients can benefit from tyrosine kinase inhibitors (TKIs) such as crizotinib and entrectinib, compounds initially approved to treat ALK-, MET- or NTRK- rearranged malignancies respectively. Given the low prevalence of ROS1-rearranged tumors, the use of TKIs was authorized based on pre-clinical evidence using limited experimental models, followed by basket clinical trials. After initiating targeted therapy, disease relapse is reported in approximately 50% of cases as a result of the appearance of resistance mechanisms. The restricted availability of TKIs active against resistance events critically reduces the overall survival. In this review we discuss the pre-clinical ROS1+ NSCLC models developed up to date, highlighting their strengths and limitations with respect to the unmet clinical needs. By combining gene-editing tools and novel cell culture approaches, newly developed pre-clinical models will enhance the development of next-generation tyrosine kinase inhibitors that overcome resistant tumor cell subpopulations.

Yes-associated protein 1 mediates initial cell survival during lorlatinib treatment through AKT signaling in ROS1-rearranged lung cancer

Tyrosine kinase inhibitors (TKIs) that target the ROS proto-oncogene 1, receptor tyrosine kinase (ROS1) gene have shown dramatic therapeutic effects in patients with ROS1-rearranged non-small-cell lung cancer (NSCLC). Nevertheless, advanced ROS1-rearranged NSCLC is rarely cured as a portion of the tumor cells can survive the initial stages of ROS1-TKI treatment, even after maximum tumor shrinkage. Therefore, understanding the mechanisms underlying initial cell survival during ROS1-TKI treatment is necessary to prevent cell survival and achieve a cure for ROS1-rearranged NSCLC. In this study, we clarified the initial survival mechanisms during treatment with lorlatinib, a ROS1 TKI. First, we established a patient-derived ezrin gene-ROS1-rearranged NSCLC cell line (KTOR71). Then, following proteomic analysis, we focused on yes-associated protein 1 (YAP1), which is a major mediator of the Hippo pathway, as a candidate factor involved in cell survival during early lorlatinib treatment. Yes-associated protein 1 was activated by short-term lorlatinib treatment both in vitro and in vivo. Genetic inhibition of YAP1 using siRNA, or pharmacological inhibition of YAP1 function by the YAP1-inhibitor verteporfin, enhanced the sensitivity of KTOR71 cells to lorlatinib. In addition, the prosurvival effect of YAP1 was exerted through the reactivation of AKT. Finally, combined therapy with verteporfin and lorlatinib was found to achieve significantly sustained tumor remission compared with lorlatinib monotherapy in vivo. These results suggest that YAP1 could mediate initial cell resistance to lorlatinib in KTOR71 cells. Thus, combined therapy targeting both YAP1 and ROS1 could potentially improve the outcome of ROS1-rearranged NSCLC.

ROS1-positive non-small cell lung cancer (NSCLC): biology, diagnostics, therapeutics and resistance

ROS1 is a proto-oncogene encoding a receptor tyrosine protein kinase (RTK), homologous to the v - Ros sequence of University of Manchester tumours virus 2 (UR2) sarcoma virus, whose ligands are still being investigated. ROS1 fusion genes have been identified in various types of tumours. As an oncoprotein, it promotes cell proliferation, activation and cell cycle progression by activating downstream signalling pathways, accelerating the development and progression of non-small cell lung cancer (NSCLC). Studies have demonstrated that ROS1 inhibitors are effective in patients with ROS1-positive NSCLC and are used for first-line clinical treatment. These small molecule inhibitors provide a rational therapeutic option for the treatment of ROS1-positive patients. Inevitably, ROS1 inhibitor resistance mutations occur, leading to tumours recurrence or progression. Here, we comprehensively review the identified biological properties and Differential subcellular localisation of ROS1 fusion oncoprotein promotes tumours progression. We summarise recently completed and ongoing clinical trials of the classic and new ROS1 inhibitors. More importantly, we classify the complex evolving tumours cell resistance mechanisms. This review contributes to our understanding of the biological properties of ROS1 and current therapeutic advances and resistant tumours cells, and the future directions to develop ROS1 inhibitors with durable effects.

Breaking the crosstalk of the Cellular Tumorigenic Network by low-dose combination therapy in lung cancer patient-derived xenografts

Non-small cell lung cancer (NSCLC) is commonly diagnosed at advanced stages limiting treatment options. Although, targeted therapy has become integral part of NSCLC treatment therapies often fail to improve patient's prognosis. Based on previously published criteria for selecting drug combinations for overcoming resistances, NSCLC patient-derived xenograft (PDX) tumors were treated with a low dose combination of cabozantinib, afatinib, plerixafor and etoricoxib. All PDX tumors treated, including highly therapy-resistant adeno- and squamous cell carcinomas without targetable oncogenic mutations, were completely suppressed by this drug regimen, leading to an ORR of 81% and a CBR of 100%. The application and safety profile of this low dose therapy regimen was well manageable in the pre-clinical settings. Overall, this study provides evidence of a relationship between active paracrine signaling pathways of the Cellular Tumorigenic Network, which can be effectively targeted by a low-dose multimodal therapy to overcome therapy resistance and improve prognosis of NSCLC.

Characterization of SLC34A2 as a Potential Prognostic Marker of Oncological Diseases

The main goal of this study is to consider SLC34A2 as a potential prognostic marker of oncological diseases using the mutational, expression, and survival data of cancer studies which are publicly available online. We collected data from four databases (cBioPortal, The Cancer Genome Atlas; cBioPortal, Genie; International Cancer Genome Consortium; ArrayExpress). In total, 111,283 samples were categorized according to 27 tumor locations. Ninety-nine functionally significant missense mutations and twelve functionally significant indel mutations in SLC34A2 were found. The most frequent mutations were SLC34A2-ROS1, p.T154A, p.P506S/R/L, p.G257A/E/R, p.S318W, p.A396T, p.P410L/S/H, p.S461C, p.A473T/V, and p.Y503H/C/F. The upregulation of SLC34A2 was found in samples of myeloid, bowel, ovarian, and uterine tumors; downregulation was found in tumor samples of breast, liver, lung, and skin cancer tumors. It was found that the life expectancy of breast and thymus cancer patients with an SLC34A2 mutation is lower, and it was revealed that SLC34A2 overexpression reduced the life span of patients with brain, ovarian, and pancreatic tumors. Thereby, for these types of oncological diseases, the mutational profile of SLC34A2 can be a potential prognostic marker for breast and thymus cancers, and the upregulation of SLC34A2 can be a potential prognostic marker for brain, ovarian, and pancreatic cancers.

Therapeutic Targeting of the Gas6/Axl Signaling Pathway in Cancer

Many signaling pathways are dysregulated in cancer cells and the host tumor microenvironment. Aberrant receptor tyrosine kinase (RTK) pathways promote cancer development, progression, and metastasis. Hence, numerous therapeutic interventions targeting RTKs have been actively pursued. Axl is an RTK that belongs to the Tyro3, Axl, MerTK (TAM) subfamily. Axl binds to a high affinity ligand growth arrest specific 6 (Gas6) that belongs to the vitamin K-dependent family of proteins. The Gas6/Axl signaling pathway has been implicated to promote progression, metastasis, immune evasion, and therapeutic resistance in many cancer types. Therapeutic agents targeting Gas6 and Axl have been developed, and promising results have been observed in both preclinical and clinical settings when such agents are used alone or in combination therapy. This review examines the current state of therapeutics targeting the Gas6/Axl pathway in cancer and discusses Gas6- and Axl-targeting agents that have been evaluated preclinically and clinically.

Antitumor effects of the multi-target tyrosine kinase inhibitor cabozantinib: a comprehensive review of the preclinical evidence

INTRODUCTION

Altered receptor tyrosine kinase (RTK) signaling contributes to tumorigenesis and suppression of immune-mediated destruction of cancer cells. Cabozantinib is an oral tyrosine kinase inhibitor that inhibits several RTKs involved in tumorigenesis, and is approved for the treatment of patients with progressive metastatic medullary thyroid cancer, advanced renal cell carcinoma, and hepatocellular carcinoma that has been previously treated with sorafenib.

AREAS COVERED

We present an up-to-date evaluation of preclinical evidence for RTK inhibition with cabozantinib, specifically VEGFR, MET, KIT, RET, AXL, FLT3, and associated antitumor effects. Preclinical investigations of cabozantinib in combination with other anticancer drugs are also reviewed.

EXPERT OPINION

Preclinical evidence shows that cabozantinib has antitumor activity against various cancer cells and exhibits synergy with other anticancer agents, including immune checkpoint inhibitors and hormone receptor or metabolic pathway inhibitors. Further optimization of cabozantinib treatment requires the identification of biomarkers of response and resistance, and exploration of complementary drug targets. Investigation of mechanisms of adaptive resistance, such as epithelial to mesenchymal transition (cancer intrinsic) and immunomodulation by the tumor microenvironment (cancer extrinsic), as well as identification of novel drug targets based on characterization of cancer stem cell metabolomic phenotypes, appear to be promising approaches.

SHP2 Inhibition Enhances the Effects of Tyrosine Kinase Inhibitors in Preclinical Models of Treatment-naïve ALK-, ROS1-, or EGFR-altered Non-small Cell Lung Cancer

After molecular-targeted therapy, some cancer cells may remain that are resistant to therapies targeting oncogene alterations, such as those in the genes encoding the EGFR and anaplastic lymphoma kinase (ALK) as well as c-ros oncogene 1 (ROS1). The mechanisms underlying this type of resistance are unknown. In this article, we report the potential role of Src homology 2 domain-containing phosphatase 2 (SHP2) in the residual cells of ALK/ROS1/EGFR-altered non-small cell lung cancer (NSCLC). Molecular-targeted therapies failed to inhibit the ERK signaling pathway in the residual cells, whereas the SHP2 inhibitor SHP099 abolished their remaining ERK activity. SHP099 administered in combination with molecular-targeted therapy resulted in marked growth inhibition of cancer cells both in vitro and in vivo Thus, treatment combining an SHP2 inhibitor and a tyrosine kinase inhibitor may be a promising therapeutic strategy for oncogene-driven NSCLC.

VEGFR2 blockade augments the effects of tyrosine kinase inhibitors by inhibiting angiogenesis and oncogenic signaling in oncogene-driven non-small-cell lung cancers

Molecular agents targeting the epidermal growth factor receptor (EGFR)-, anaplastic lymphoma kinase (ALK)- or c-ros oncogene 1 (ROS1) alterations have revolutionized the treatment of oncogene-driven non-small-cell lung cancer (NSCLC). However, the emergence of acquired resistance remains a significant challenge, limiting the wider clinical success of these molecular targeted therapies. In this study, we investigated the efficacy of various molecular targeted agents, including erlotinib, alectinib, and crizotinib, combined with anti-vascular endothelial growth factor receptor (VEGFR) 2 therapy. The combination of VEGFR2 blockade with molecular targeted agents enhanced the anti-tumor effects of these agents in xenograft mouse models of EGFR-, ALK-, or ROS1-altered NSCLC. The numbers of CD31-positive blood vessels were significantly lower in the tumors of mice treated with an anti-VEGFR2 antibody combined with molecular targeted agents compared with in those of mice treated with molecular targeted agents alone, implying the antiangiogenic effects of VEGFR2 blockade. Additionally, the combination therapies exerted more potent antiproliferative effects in vitro in EGFR-, ALK-, or ROS1-altered NSCLC cells, implying that VEGFR2 inhibition also has direct anti-tumor effects on cancer cells. Furthermore, VEGFR2 expression was induced following exposure to molecular targeted agents, implying the importance of VEGFR2 signaling in NSCLC patients undergoing molecular targeted therapy. In conclusion, VEGFR2 inhibition enhanced the anti-tumor effects of molecular targeted agents in various oncogene-driven NSCLC models, not only by inhibiting tumor angiogenesis but also by exerting direct antiproliferative effects on cancer cells. Hence, combination therapy with anti-VEGFR2 antibodies and molecular targeted agents could serve as a promising treatment strategy for oncogene-driven NSCLC.

Combination of crizotinib and chemotherapy in patients with relapsed or refractory anaplastic lymphoma kinase (ALK)-positive anaplastic large cell lymphoma (ALCL)

Our aim was to explore the role of crizotinib, targeted anaplastic lymphoma kinase (ALK), on r/r systemic anaplastic large cell lymphoma (sALCL). The treated group prospectively screened 20 patients. After taking crizotinib in the first week, 16 patients who were tolerant and sensitive received the combination of crizotinib with chemotherapy. The control group included 27 patients receiving chemotherapy in the same hospital during the same period. The objective remission rates of the treated and control group were 81.3% and 74.1% (p = .869), respectively. The progression-free survival rates at two years in treated and control group were 68.7% and 45.0% (HR = 0.42, 95% CI 0.17-0.99, p < .05), respectively. The overall survival rates at two years in the treated and control group were 86.1% and 78.9% (p = .385, HR = 0.51, 95% CI 0.11-2.30), respectively. The main adverse events included elevated transaminase, diarrhea, and vision abnormalities. Thus, the combination of crizotinib with chemotherapy might be effective in ALK-positive and crizotinib sensitive r/r sALCL patients.

Cabozantinib (XL184) and R428 (BGB324) Inhibit the Growth of Esophageal Squamous Cell Carcinoma (ESCC)

Esophageal squamous cell carcinoma (ESCC) is a deadly disease for which no effective targeted therapeutic agent has been approved. Both AXL and c-MET have been reported to be independent prognostic factors for ESCC. Thus, inhibitors of AXL/c-MET might have great potential as targeted therapy for ESCC. In the current study, we evaluated the therapeutic potential of the AXL/c-MET selective inhibitors, R428 and cabozantinib, in cell and mouse xenograft models. We demonstrated that both R428 and cabozantinib significantly inhibited the growth of CE81T and KYSE-70 ESCC cells and showed by wound-healing assay that they both inhibited ESCC cell migration. In the animal model, ESCC xenograft models were established by injecting KYSE-70 cells with Matrigel into the upper back region of NOD-SCID male mice followed by treatment with vehicle control, R428 (50 mg/kg/day), cisplatin (1.0 mg/kg), or cabozantinib (30 mg/kg/day) for the indicated number of days. R428 alone significantly inhibited ESCC tumor growth compared to the vehicle; however, no synergistic effect with cisplatin was observed. Notably, the dramatic efficacy of cabozantinib alone was observed in the mouse xenograft model. Collectively, our study demonstrated that both cabozantinib and R428 inhibit ESCC growth in cell and xenograft models. The results reveal the great potential of using cabozantinib for targeted therapy of ESCC.

ROS1-ADGRG6: a case report of a novel ROS1 oncogenic fusion variant in lung adenocarcinoma and the response to crizotinib

BACKGROUND

ROS1 rearrangements are validated drivers in lung cancer, which have been identified in a small subset (1-2%) of patients with non-small cell lung cancer (NSCLC). To date, 18 fusion genes of ROS1 have been identified in NSCLC. The ALK inhibitor (crizotinib) exhibits therapeutic effect against ROS1-rearranged NSCLC. Next-generation sequencing (NGS) technology represents a novel tool for ROS1 detection that covers many fusion genes.

CASE PRESENTATION

A 55-year-old female with EGFR mutation (L858R) was diagnosed with lung adenocarcinoma, who was responsive to first-generation EGFR-tyrosine kinase inhibitor (TKI). Afterwards, she developed acquired resistance accompanied with a ROS1 rearrangement. A NGS assay showed that the tumor had a novel ROS1-ADGRG6 rearrangement generated by the fusion of exons of 1-33 of ROS1 on chr6: q22.1 to exons of 2-26 of ADGRG6 on chr6: q24.2. The patient was obviously responsive to crizotinib.

CONCLUSION

We firstly identified ROS1-ADGRG6 fusion variant in NSCLC by NGS, which should be considered in further ROS1 detecting assays.

Combined effect of cabozantinib and gefitinib in crizotinib-resistant lung tumors harboring ROS1 fusions

The ROS1 tyrosine kinase inhibitor (TKI) crizotinib has shown dramatic effects in patients with non‐small cell lung cancer (NSCLC) harboring ROS1 fusion genes. However, patients inevitably develop resistance to this agent. Therefore, a new treatment strategy is required for lung tumors with ROS1 fusion genes. In the present study, lung cancer cell lines, HCC78 harboring SLC34A2‐ROS1 and ABC‐20 harboring CD74‐ROS1, were used as cell line‐based resistance models. Crizotinib‐resistant HCC78R cells were established from HCC78. We comprehensively screened the resistant cells using a phosphor‐receptor tyrosine kinase array and RNA sequence analysis by next‐generation sequencing. HCC78R cells showed upregulation of HB‐EGF and activation of epidermal growth factor receptor (EGFR) phosphorylation and the EGFR signaling pathway. Recombinant HB‐EGF or EGF rendered HCC78 cells or ABC‐20 cells resistant to crizotinib. RNA sequence analysis by next‐generation sequencing revealed the upregulation of AXL in HCC78R cells. HCC78R cells showed marked sensitivity to EGFR‐TKI or anti‐EGFR antibody treatment in vitro. Combinations of an AXL inhibitor, cabozantinib or gilteritinib, and an EGFR‐TKI were more effective against HCC78R cells than monotherapy with an EGFR‐TKI or AXL inhibitor. The combination of cabozantinib and gefitinib effectively inhibited the growth of HCC78R tumors in an in vivo xenograft model of NOG mice. The results of this study indicated that HB‐EGF/EGFR and AXL play roles in crizotinib resistance in lung cancers harboring ROS1 fusions. The combination of cabozantinib and EGFR‐TKI may represent a useful alternative treatment strategy for patients with advanced NSCLC harboring ROS1 fusion genes.