Convolutional neural network deep learning model accurately detects rectal cancer in endoanal ultrasounds

BACKGROUND

Imaging is vital for assessing rectal cancer, with endoanal ultrasound (EAUS) being highly accurate in large tertiary medical centers. However, EAUS accuracy drops outside such settings, possibly due to varied examiner experience and fewer examinations. This underscores the need for an AI-based system to enhance accuracy in non-specialized centers. This study aimed to develop and validate deep learning (DL) models to differentiate rectal cancer in standard EAUS images.

METHODS

A transfer learning approach with fine-tuned DL architectures was employed, utilizing a dataset of 294 images. The performance of DL models was assessed through a tenfold cross-validation.

RESULTS

The DL diagnostics model exhibited a sensitivity and accuracy of 0.78 each. In the identification phase, the automatic diagnostic platform achieved an area under the curve performance of 0.85 for diagnosing rectal cancer.

CONCLUSIONS

This research demonstrates the potential of DL models in enhancing rectal cancer detection during EAUS, especially in settings with lower examiner experience. The achieved sensitivity and accuracy suggest the viability of incorporating AI support for improved diagnostic outcomes in non-specialized medical centers.

Tumour mutations in long noncoding RNAs enhance cell fitness

Long noncoding RNAs (lncRNAs) are linked to cancer via pathogenic changes in their expression levels. Yet, it remains unclear whether lncRNAs can also impact tumour cell fitness via function-altering somatic "driver" mutations. To search for such driver-lncRNAs, we here perform a genome-wide analysis of fitness-altering single nucleotide variants (SNVs) across a cohort of 2583 primary and 3527 metastatic tumours. The resulting 54 mutated and positively-selected lncRNAs are significantly enriched for previously-reported cancer genes and a range of clinical and genomic features. A number of these lncRNAs promote tumour cell proliferation when overexpressed in in vitro models. Our results also highlight a dense SNV hotspot in the widely-studied NEAT1 oncogene. To directly evaluate the functional significance of NEAT1 SNVs, we use in cellulo mutagenesis to introduce tumour-like mutations in the gene and observe a significant and reproducible increase in cell fitness, both in vitro and in a mouse model. Mechanistic studies reveal that SNVs remodel the NEAT1 ribonucleoprotein and boost subnuclear paraspeckles. In summary, this work demonstrates the utility of driver analysis for mapping cancer-promoting lncRNAs, and provides experimental evidence that somatic mutations can act through lncRNAs to enhance pathological cancer cell fitness.

A DNA-PK phosphorylation site on MET regulates its signaling interface with the DNA damage response

The DNA damage response (DDR) is intertwined with signaling pathways downstream of oncogenic receptor tyrosine kinases (RTKs). To drive research into the application of targeted therapies as radiosensitizers, a better understanding of this molecular crosstalk is necessary. We present here the characterization of a previously unreported MET RTK phosphosite, Serine 1016 (S1016) that represents a potential DDR-MET interface. MET S1016 phosphorylation increases in response to irradiation and is mainly targeted by DNA-dependent protein kinase (DNA-PK). Phosphoproteomics unveils an impact of the S1016A substitution on the overall long-term cell cycle regulation following DNA damage. Accordingly, the abrogation of this phosphosite strongly perturbs the phosphorylation of proteins involved in the cell cycle and formation of the mitotic spindle, enabling cells to bypass a G2 arrest upon irradiation and leading to the entry into mitosis despite compromised genome integrity. This results in the formation of abnormal mitotic spindles and a lower proliferation rate. Altogether, the current data uncover a novel signaling mechanism through which the DDR uses a growth factor receptor system for regulating and maintaining genome stability.

CAR T cell-based immunotherapy and radiation therapy: potential, promises and risks

CAR T cell-based therapies have revolutionized the treatment of hematological malignancies such as leukemia and lymphoma within the last years. In contrast to the success in hematological cancers, the treatment of solid tumors with CAR T cells is still a major challenge in the field and attempts to overcome these hurdles have not been successful yet. Radiation therapy is used for management of various malignancies for decades and its therapeutic role ranges from local therapy to a priming agent in cancer immunotherapy. Combinations of radiation with immune checkpoint inhibitors have already proven successful in clinical trials. Therefore, a combination of radiation therapy may have the potential to overcome the current limitations of CAR T cell therapy in solid tumor entities. So far, only limited research was conducted in the area of CAR T cells and radiation. In this review we will discuss the potential and risks of such a combination in the treatment of cancer patients.

Beyond keratinocyte differentiation: emerging new biology of small proline-rich proteins

Small proline-rich proteins (SPRRPs) are traditionally known for their function in keratinocyte homeostasis. Recent evidence demonstrates their involvement in additional diverse physiological processes ranging from p53 signaling and direct prevention of DNA damage to bactericidal activities. We highlight these novel, intriguing roles of SPRRPs and discuss them in the context of relevant pathological conditions.

Prognostic and Predictive Biomarkers in Head and Neck Squamous Cell Carcinoma Treated with Radiotherapy-A Systematic Review

Background: Radiotherapy is a mainstay in head and neck squamous cell carcinoma (HNSCC) treatment but is mostly applied without stratification by molecular diagnostics. Development of reliable biomarkers may have the potential to improve radiotherapy (RT) efficacy and reduce toxicity. We conducted a systematic review to summarize the field of biomarkers in HNSCC treated by RT. Methods: Pubmed and EMBASE were searched independently by two researchers following pre-defined inclusion and exclusion criteria. Z curves were generated to investigate publication bias. OncoKB was used for identification of druggable targets. Results: 134 manuscripts remained for data extraction. 12% of tumors were AJCC/UICC stage I-II and 82% were stage III-IV. The most common biomarkers were proteins (39%), DNA (14%) and mRNA (9%). Limiting analysis to prospective data and statistically significant results, we found three potentially druggable targets: ERCC2, PTCH1 and EGFR. Regarding data quality, AJCC/UICC stage was missing in 32% of manuscripts. 73% of studies were retrospective and only 7% were based on prospective randomized trials. Z-curves indicated the presence of publication bias. Conclusion: An abundance of potential biomarkers in HNSCC is available but data quality is limited by retrospective collection, lack of validation and publication bias. Improved study design and reporting quality might accelerate successful development of personalized treatments in HNSCC.

P06.08.B Radiation therapy enhances anti-tumor activity of a MET CAR T-based immunotherapy for glioblastoma

Background

Glioblastoma is the most frequent primary brain tumor with dismal prognosis after standard treatment with surgery, and chemoradiation (the Stupp protocol). After a decade of failed clinical trials, tumor-treating fields have been first to show the added benefit of improved overall survival compared to the Stupp protocol (20.9 months vs 16.0 months). However, GBM remains a devastating disease, with almost inevitable recurrence, and limited options for second-line therapy. Radiation therapy (RT), is a standard therapy option for GBM, and it is used in most GBM cases affecting tumor through induction of DNA-damage. Recently, RT has been investigated as a mediator of T cell-based therapies in the context of immunosuppressive GBM microenvironment. The findings have shown promise in combination of T cell-based therapies, such as chimeric antigen receptor (CAR) T cell therapies, in improving the tumor infiltration, and penetration with immune cells. MET is a relevant oncogene in the context of GBM, being involved in stem-like properties, radiation response and resistance․ Hence, MET appeared to be a plausible target for combination with RT. In our research, we use MET-targeting CAR T cells (MET-CAR T cells) combined with radiation, and hypothesize synergistic interaction for GBM treatment.

Material and Methods

We used adherent (2D) and stem-like (3D) human GBM cell lines with different levels of MET expression. For MET-CAR T cell generation we did retrovirus-mediated transduction of activated human T cells and sorted the CAR-positive cells. We co-cultured MET-CAR T cells with GBM cells with or without RT, and assessed the killing and cytokine production in CAR T cells.

Results

Our results indicated that 5Gy radiation combined with MET-CAR T cells increases their potential in tumor cell killing. We observed increased CAR T cells effect at lower CAR T to target cells ratios when combined with radiation, even when radiation treatment did not lead to a significant decrease in viability. This phenomenon was similar across different types of cell lines (adherent, stem-like), different levels of MET expression, and different sensitivity to CAR T cells. We investigated the underlying mechanisms via intracellular cytokine measurement. We observed the most prominent response in TNF-α-expression. We also observed an increase in Granzyme B expression in co-culture with some of the GBM cell lines, especially in CD8+ subpopulation of CAR T cells. IFN-gamma expression increased in some adherent glioma cell lines but not in stem-like cell lines.

Conclusion

In conclusion, our data demonstrates the potency of MET-CAR T cells against GBM, and increased efficiency when combined with radiation. The suggested mechanism is the increased activation of T cells in TNF-α-dependent-manner. To validate these results we are testing our setup in an orthotopic mouse GBM model.

Automated processing of thermal imaging to detect COVID-19 and microvascular dysfunction

Background

Coronavirus disease 2019 (COVID-19) is associated with microvascular dysfunction. Non-invasive thermal imaging can hypothetically detect changes in perfusion, inflammation and vascular injury. We sought to develop a new point-of-care, non-contact thermal imaging tool to detect COVID-19 by microvascular dysfunction, based on image processing algorithms and machine learning analysis.

Materials and methods

We captured thermal images of the back of 101 individuals, with (n=62) and without (n=39) COVID-19, using a portable thermal camera that connects directly to smartphones. We developed new image processing algorithms that automatically extract multiple texture and shape features of the thermal images (Figure 1A). We then evaluated the ability of our thermal features to detect COVID-19 and systemic changes of heat distribution associated with microvascular disease. We also assessed correlations between thermal imaging to conventional biomarkers and chest X-ray (CXR).

Results

Our novel image processing algorithms achieved up to 92% sensitivity in detecting COVID-19 with an area under the curve of 0.85 (95% CI: 0.78, 0.93; p<0.01). Systemic alterations in blood flow associated with vascular disease were observed across the entire back. Thermal imaging scores were inversely correlated with clinical variables associated with COVID-19 disease progression, including blood oxygen saturation, C- reactive protein, and D-dimer. The thermal imaging findings were not correlated with the results of CXR.

Conclusions

We show, for the first time, that a hand-held thermal imaging device can be used to detect COVID-19. Non-invasive thermal imaging could be used to screen for COVID-19 in out-of-hospital settings, especially in low-income regions with limited imaging resources. Moreover, thermal imaging might detect micro-angiopathies and endothelial dysfunction in patients with COVID-19 and could possibly improve risk stratification of infected individuals (Figure 1B).

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): 1. The Israel Innovation Authority2. The Nicholas and Elizabeth Slezak Super Center for Cardiac Research and Biomedical Engineering at Tel Aviv University Figure 1. A. Representative steps of our thermal image processing algorithms. B. A schematic illustration of the research design and potential impact.

Abstract PO-026: DNA damage response and repair characterization in CHK2-deficient cancers

Double strand breaks (DSBs) are the most lethal DNA lesions as they can result in chromosomal rearrangements or loss of genetic material. To detect and repair DNA, cells have developed the DNA damage response, a cascade of proteins in which the checkpoint kinase 2 (CHK2) is involved. CHK2-deficient cancers, such as breast, prostate or colon, might have a compromised response to ionizing radiation (IR), arresting cell cycle at checkpoints or inducing apoptosis in presence of irreparable damage. To understand how the lack of CHK2 is affecting DNA damage response and repair, the human isogenic HCT116 colorectal cancer cell lines proficient (CHK2 WT) and deficient (CHK2 KO) for CHK2 have been characterized. Cell cycle distribution and γH2AX foci formation were assessed by flow cytometry and immunofluorescence, respectively, to determine the differences in cell cycle checkpoints and DSBs infliction and resolution upon IR. Traffic Light Reporter, complemented by immunofluorescence of RAD51 foci, was employed in both CHK2 WT and KO cell lines to identify the preferred DSB repair pathway. Our results indicate that CHK2-proficient and -deficient cell lines do not exhibit significant differences in cell cycle distribution upon IR. On the other hand, CHK2 KO cells display a significant increase in γH2AX foci per cell compared to the CHK2 WT. Upon 1Gy of IR, cells lacking CHK2 increment the number of foci per cell, indicating that DSBs detection occurs independently of the CHK2 status. Furthermore, the Traffic Light Reporter revealed higher homologous recombination (HR) to non-homologous end-joining (NHEJ) ratio in the CHK2 KO cells as compared to their CHK2 WT counterparts, suggesting that the lack of CHK2 stimulates a shift in the DSBs repair pathway choice. These results contrast with the RAD51 foci formation, which seems to be compromised in the CHK2 KO cells in both treated and untreated conditions as compared to the CHK2-proficient cells. Our results suggest that CHK2 status considerably affects cellular DNA damage response and these differences in execution of DNA repair could be exploited in CHK2-deficient cancers.

Citation Format: Carmen Muñoz-Maldonado, Aurélie Quintin, Daniel M. Aebersold, Yitzhak Zimmer, Michaela Medová. DNA damage response and repair characterization in CHK2-deficient cancers [abstract]. In: Proceedings of the AACR Virtual Special Conference on Radiation Science and Medicine; 2021 Mar 2-3. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(8_Suppl):Abstract nr PO-026.

Abstract PO-039: Radiation therapy enhances anti-tumor activity of a MET CAR T-based immunotherapy approach for glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most prevalent primary malignant brain tumor, which has an aggressive phenotype and mostly fatal recurrence after standard therapy. MET, the hepatocyte growth factor (HGF) receptor is a relevant target for GBM treatment as it is expressed in up to 50% of cases and its expression, which may be induced by radiation therapy (RT), can potentially contribute to RT-resistance of GBM stem cells, and tumor recurrence. MET-based chimeric antigen (CAR) T cell therapy is currently being evaluated in several solid tumor working settings. A combination of T cell-based therapies with RT may improve the efficacy of the CAR T cell therapy through by the RT-induced immune activation via release of cytokines and induction of antigen expression, similarly as has been observed when combining RT with immune checkpoint inhibitors. Here we investigated the combination of MET-targeting CAR T cells with RT for GBM treatment, hypothesizing enhanced anti-tumor effects. The current study used a panel of MET-proficient and MET-deficient human GBM and GBM stem-like cell lines. Cells have been irradiated with a single dose of 0, 2, 5, or 10 Gy and RT impact on MET expression has been assessed at various time points after RT administration. Results show MET increase after RT in some cell lines. To test MET-targeting CAR T effect on the GBM cell lines, CAR constructs that are based on HGF-MET binding elements have been introduced into virus-producing cells and used for human T cells transduction to generate MET-targeting CAR T cells. CAR T cells co-cultured with GBM cell lines in vitro have specifically and significantly decreased viability of MET-positive cancer cells. Data resulting from combination of RT and CAR T cells treatment suggest that radiation exhibits an enhancement of CAR T cells anti-tumor killing activity, indicating a synergism between the two modalities. In conclusion, our data are the first to indicate the efficacy of a MET-based CAR T immunotherapy approach in GBM cell lines. The results also demonstrate a basis for the combination of a MET CAR T modality together with RT. The mechanisms for understanding the interaction between RT and the MET CAR T cells are under investigation.

Citation Format: Lusine Hovhannisyan, Daniel M. Aebersold, John Maher, Adrian F. Ochsenbein, Carsten Riether, Michaela Medova, Yitzhak Zimmer. Radiation therapy enhances anti-tumor activity of a MET CAR T-based immunotherapy approach for glioblastoma multiforme [abstract]. In: Proceedings of the AACR Virtual Special Conference on Radiation Science and Medicine; 2021 Mar 2-3. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(8_Suppl):Abstract nr PO-039.

Synergistic effect of the TLR5 agonist CBLB502 and its downstream effector IL-22 against liver injury

The toll-like receptor 5 (TLR5) agonist, CBLB502/Entolimod, is a peptide derived from bacterial flagellin and has been shown to protect against radiation-induced tissue damage in animal models. Here we investigated the protective mechanism of CBLB502 in the liver using models of ischemia-reperfusion injury and concanavalin A (ConA) induced immuno-hepatitis. We report that pretreatment of mice with CBLB502 provoked a concomitant activation of NF-κB and STAT3 signaling in the liver and reduced hepatic damage in both models. To understand the underlying mechanism, we screened for cytokines in the serum of CBLB502 treated animals and detected high levels of IL-22. There was no transcriptional upregulation of IL-22 in the liver, rather it was found in extrahepatic tissues, mainly the colon, mesenteric lymph nodes (MLN), and spleen. RNA-seq analysis on isolated hepatocytes demonstrated that the concomitant activation of NF-κB signaling by CBLB502 and STAT3 signaling by IL-22 produced a synergistic cytoprotective transcriptional signature. In IL-22 knockout mice, the loss of IL-22 resulted in a decrease of hepatic STAT3 activation, a reduction in the cytoprotective signature, and a loss of hepatoprotection following ischemia-reperfusion-induced liver injury. Taken together, these findings suggest that CBLB502 protects the liver by increasing hepatocyte resistance to acute liver injury through the cooperation of TLR5-NF-κB and IL-22-STAT3 signaling pathways.

Enhancing CRISPR deletion via pharmacological delay of DNA-PKcs

CRISPR-Cas9 deletion (CRISPR-del) is the leading approach for eliminating DNA from mammalian cells and underpins a variety of genome-editing applications. Target DNA, defined by a pair of double-strand breaks (DSBs), is removed during nonhomologous end-joining (NHEJ). However, the low efficiency of CRISPR-del results in laborious experiments and false-negative results. By using an endogenous reporter system, we show that repression of the DNA-dependent protein kinase catalytic subunit (DNA-PKcs)—an early step in NHEJ—yields substantial increases in DNA deletion. This is observed across diverse cell lines, gene delivery methods, commercial inhibitors, and guide RNAs, including those that otherwise display negligible activity. We further show that DNA-PKcs inhibition can be used to boost the sensitivity of pooled functional screens and detect true-positive hits that would otherwise be overlooked. Thus, delaying the kinetics of NHEJ relative to DSB formation is a simple and effective means of enhancing CRISPR-deletion.

Abstract A52: Deciphering MET-dependent modulation of global cellular responses to DNA damage by quantitative phosphoproteomics reveals Ser1016 as a novel MET phosphosite that regulates cellular response to irradiation

There is emerging evidence that DNA damage response (DDR) intertwines with signaling pathways downstream of oncogenic receptor tyrosine kinases (RTKs). Two complementary phosphoproteomic approaches revealed global networks and identified and validated core phosphosites that participate in a crosstalk between the MET RTK and the DDR, including a newly discovered phosphosite on MET itself, Ser1016. DNA-PK phosphorylates Ser1016, and this phosphorylation is increased following irradiation. Cell lines as well as animal models expressing Ser1016Ala phosphodeficient receptor exhibit greater sensitivity to irradiation. MET Ser1016Ala mutants fail to undergo proper radiation-induced cell cycle arrest by bypassing the G2 checkpoint with a premature entry into mitosis and abnormal mitotic spindles, leading to a lower proliferation rate of Ser1016-deficient cells. Regulation of MET activity through Ser1016 phosphorylation by a DDR core kinase represents a critical event involved in DNA repair signaling through a growth factor receptor that frequently functions as a tumor driver.

Citation Format: Jonas P. Koch, Ariel Bensimon, Selina M. Roth, Matúš Medo, Paola Francica, Eleonora Orlando, Rahel Riedo, Jacopo Gavini, Aurélie Quintin, Astrid A. Glück, Deborah M. Stroka, Andree Blaukat, Daniel M. Aebersold, Yitzhak Zimmer, Ruedi Aebersold, Michaela Medová. Deciphering MET-dependent modulation of global cellular responses to DNA damage by quantitative phosphoproteomics reveals Ser1016 as a novel MET phosphosite that regulates cellular response to irradiation [abstract]. In: Proceedings of the AACR Special Conference on the Evolving Landscape of Cancer Modeling; 2020 Mar 2-5; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2020;80(11 Suppl):Abstract nr A52.

Abstract PR05: A metabolomics discovery profiling approach identifies an E2F1-associated purine synthesis pathway as a major component of the MET-DNA damage response network

Various lines of investigation support a signaling interphase shared by various receptor tyrosine kinases and the DNA damage response. However, the underlying driving network nodes and their contribution to the maintenance of DNA integrity remain unknown. We used discovery metabolomics combined with transcriptomics to identify changes in global metabolic pathways that are relevant to DNA repair following MET inhibition (METi). METi was associated with formation of γH2AX foci together with significant alterations in major metabolic circuits. Remarkably, 5′-phosphoribosyl-N-formylglycinamide (FGAR), a de novo purine synthesis pathway metabolite, was decreased in MET-dependent cancer models and a METi-related depletion of dNTPs was observed. Likewise, METi instigated the downregulation of critical purine synthesis enzymes including phosphoribosylglycinamide formyltransferase (GART), which is responsible for FGAR synthesis. Genes encoding these enzymes are regulated through the E2F1 transcription factor, whose levels decreased upon METi in MET-driven cells. To validate those findings, a transient E2F1 overexpression was sufficient to prevent MET targeting-dependent dNTPs depletion and the concomitant METi-associated DNA damage in MET-driven tumor cells. These novel observations support the notion that METi-mediated sensitization to DNA-damaging agents commonly used in cancer therapeutics is largely linked to the depletion of critical metabolites used in DNA repair due to downregulation of key metabolic enzymes whose expression is regulated through MET signaling.

This abstract is also being presented as Poster A51.

Citation Format: Michaela Poliaková, Matúš Medo, Jonas Koch, SiAna Coggins, Baek Kim, Daniel M. Aebersold, Nicola Zamboni, Michaela Medová, Yitzhak Zimmer. A metabolomics discovery profiling approach identifies an E2F1-associated purine synthesis pathway as a major component of the MET-DNA damage response network [abstract]. In: Proceedings of the AACR Special Conference on the Evolving Landscape of Cancer Modeling; 2020 Mar 2-5; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2020;80(11 Suppl):Abstract nr PR05.

Deciphering MET-dependent modulation of global cellular responses to DNA damage by quantitative phosphoproteomics

Increasing evidence suggests that interference with growth factor receptor tyrosine kinase (RTK) signaling can affect DNA damage response (DDR) networks, with a consequent impact on cellular responses to DNA‐damaging agents widely used in cancer treatment. In that respect, the MET RTK is deregulated in abundance and/or activity in a variety of human tumors. Using two proteomic techniques, we explored how disrupting MET signaling modulates global cellular phosphorylation response to ionizing radiation (IR). Following an immunoaffinity‐based phosphoproteomic discovery survey, we selected candidate phosphorylation sites for extensive characterization by targeted proteomics focusing on phosphorylation sites in both signaling networks. Several substrates of the DDR were confirmed to be modulated by sequential MET inhibition and IR, or MET inhibition alone. Upon combined treatment, for two substrates, NUMA1 S395 and CHEK1 S345, the gain and loss of phosphorylation, respectively, were recapitulated using invivo tumor models by immunohistochemistry, with possible utility in future translational research. Overall, we have corroborated phosphorylation sites at the intersection between MET and the DDR signaling networks, and suggest that these represent a class of proteins at the interface between oncogene‐driven proliferation and genomic stability.

Targeting the MET Receptor Tyrosine Kinase as a Strategy for Radiosensitization in Locoregionally Advanced Head and Neck Squamous Cell Carcinoma

Radiotherapy (RT) along with surgery is the mainstay of treatment in head and neck squamous cell carcinoma (HNSCC). Radioresistance represents a major source of treatment failure, underlining the urgent necessity to explore and implement effective radiosensitization strategies. The MET receptor widely participates in the acquisition and maintenance of an aggressive phenotype in HNSCC and modulates the DNA damage response following ionizing radiation (IR). Here, we assessed MET expression and mutation status in primary and metastatic lesions within a cohort of patients with advanced HNSCC. Moreover, we investigated the radiosensitization potential of the MET inhibitor tepotinib in a panel of cell lines, in vitro and in vivo, as well as in ex vivo patient-derived organotypic tissue cultures (OTC). MET was highly expressed in 62.4% of primary tumors and in 53.6% of lymph node metastases (LNM), and in 6 of 9 evaluated cell lines. MET expression in primaries and LNMs was significantly associated with decreased disease control in univariate survival analyses. Tepotinib abrogated MET phosphorylation and to distinct extent MET downstream signaling. Pretreatment with tepotinib resulted in variable radiosensitization, enhanced DNA damage, cell death, and G₂-M-phase arrest. Combination of tepotinib with IR led to significant radiosensitization in one of two tested in vivo models. OTCs revealed differential patterns of response toward tepotinib, irradiation, and combination of both modalities. The molecular basis of tepotinib-mediated radiosensitization was studied by a CyTOF-based single-cell mass cytometry approach, which uncovered that MET inhibition modulated PI3K activity in cells radiosensitized by tepotinib but not in the resistant ones.

A Comparative Analysis of Individual RAS Mutations in Cancer Biology

In human cells, three closely related RAS genes, termed HRAS, KRAS, and NRAS, encode four highly homologous proteins. RAS proteins are small GTPases involved in a broad spectrum of key molecular and cellular activities, including proliferation and survival among others. Gain-of-function missense mutations, mostly located at codons 12, 13, and 61, constitutively activate RAS proteins and can be detected in various types of human cancers. KRAS is the most frequently mutated, followed by NRAS and HRAS. However, each isoform exhibits distinctive mutation frequency at each codon, supporting the hypothesis that different RAS mutants may lead to distinct biologic manifestations. This review is focused on the differences in signaling and phenotype, as well as on transcriptomics, proteomics, and metabolomics profiles related to individual RAS-mutated variants. Additionally, association of these mutants with particular targeted outcomes and rare mutations at additional RAS codons are discussed.

P2435Non-invasive thermal imaging identifies left ventricular remodeling in mice

Purpose

Thermal infrared imaging is a non-invasive tool with the potential to screen physiological processes and diseases. The use of this technique to image internal organs, such as the heart, has not yet been investigated. We aimed to determine the ability of a novel algorithm for thermal image-processing to detect structural and functional changes in a mouse model of cardiac remodeling.

Methods

We randomized 12 male mice (weight 20–25 gr) to treatment with either angiotensin-II (2 mg/kg/day, n=6) or saline (n=6) pump-infusion for 28 days. We measured blood pressure weekly, together with serial trans-thoracic echocardiography studies and histopathological evaluation of the hearts. We captured thermal images with the commercially available FLIR One camera, and processed images by our novel algorithm.

Results

Angiotensin infusion increased blood pressure together with cardiac hypertrophy and fibrosis. Thermal imaging identified an increase in the fraction of the skin heated by the heart in angiotensin-treated mice, at day 28 of the experiment. Thermal image findings were correlated to left ventricular mass and volume by echocardiography (r=0.6, p=0.07 and r=0.8, p<0.01). By thermal imaging, all angiotensin-treated hearts displayed a unique triangle-like shape of heat distribution. This finding was absent in controls, indicating remodeling in the hypertensive heart.

Visual Abstract

Conclusion

Our preliminary findings suggest, for the first time, that a thermal camera with a new image-processing algorithm, identifies cardiac structural changes in mice. Our findings propose a new, simple, and non-invasive tool to diagnose and monitor adverse cardiac remodeling.

Metabolomics reveals tepotinib-related mitochondrial dysfunction in MET-activating mutations-driven models

Genetic aberrations in the hepatocyte growth factor receptor tyrosine kinase MET induce oncogenic addiction in various types of human cancers, advocating MET as a viable anticancer target. Here, we report that MET signaling plays an important role in conferring a unique metabolic phenotype to cellular models expressing MET-activating mutated variants that are either sensitive or resistant toward MET small molecule inhibitors. MET phosphorylation downregulated by the specific MET inhibitor tepotinib resulted in markedly decreased viability and increased apoptosis in tepotinib-sensitive cells. Moreover, prior to the induction of MET inhibition-dependent cell death, tepotinib also led to an altered metabolic signature, characterized by a prominent reduction of metabolite ions related to amino sugar metabolism, gluconeogenesis, glycine and serine metabolism, and of numerous TCA cycle-related metabolites such as succinate, malate, and citrate. Functionally, a decrease in oxygen consumption rate, a reduced citrate synthase activity, a drop in membrane potential, and an associated misbalanced mitochondrial function were observed exclusively in MET inhibitor-sensitive cells. These data imply that interference with metabolic state can be considered an early indicator of efficient MET inhibition and particular changes reported here could be explored in the future as markers of efficacy of anti-MET therapies.

Comprehensive Genomic Profiling of Patient-matched Head and Neck Cancer Cells: A Preclinical Pipeline for Metastatic and Recurrent Disease

Metastases and tumor recurrence have a major prognostic impact in head and neck squamous cell carcinoma (HNSCC); however, cellular models that comprehensively characterize metastatic and recurrent HNSCC are lacking. To this end, we obtained genomic, transcriptomic, and copy number profiles of the UM-SCC cell line panel, encompassing patient-matched metastatic and recurrent cells. UM-SCC cells recapitulate the most prevalent genomic alterations described in HNSCC, featuring common TP53, PI3K, NOTCH, and Hippo pathway mutations. This analysis identified a novel F977Y kinase domain PIK3CA mutation exclusively present in a recurrent cell line (UM-SCC14B), potentially conferring resistance to PI3K inhibitors. Small proline-rich protein 2A (SPRR2A), a protein involved in epithelial homeostasis and invasion, was one of the most consistently downregulated transcripts in metastatic and recurrent UM-SCC cells. Assessment of SPRR2A protein expression in a clinical cohort of patients with HNSCC confirmed common SPRR2A downregulation in primary tumors (61.9% of cases) and lymph node metastases (31.3%), but not in normal tissue. High expression of SPRR2A in lymph node metastases was, along with nonoropharyngeal location of the primary tumor, an independent prognostic factor for regional disease recurrence after surgery and radiotherapy (HR 2.81; 95% CI, 1.16-6.79; P = 0.02). These results suggest that SPRR2A plays a dual role in invasion and therapeutic resistance in HNSCC, respectively through its downregulation and overexpression. IMPLICATIONS: The current study reveals translationally relevant mechanisms underlying metastasis and recurrence in HNSCC and represents an adjuvant tool for preclinical research in this disease setting. Underlining its discovery potential this approach identified a PIK3CA-resistant mutation as well as SPRR2A as possible theragnostic markers.

The relevance of tyrosine kinase inhibitors for global metabolic pathways in cancer

Tumor metabolism is a thrilling discipline that focuses on mechanisms used by cancer cells to earn crucial building blocks and energy to preserve growth and overcome resistance to various treatment modalities. At the same time, therapies directed specifically against aberrant signalling pathways driven by protein tyrosine kinases (TKs) involved in proliferation, metastasis and growth count for several years to promising anti-cancer approaches. In this respect, small molecule inhibitors are the most widely used clinically relevant means for targeted therapy, with a rising number of approvals for TKs inhibitors. In this review, we discuss recent observations related to TKs-associated metabolism and to metabolic feedback that is initialized as cellular response to particular TK-targeted therapies. These observations provide collective evidence that therapeutic responses are primarily linked to such pathways as regulation of lipid and amino acid metabolism, TCA cycle and glycolysis, advocating therefore the development of further effective targeted therapies against a broader spectrum of TKs to treat patients whose tumors display deregulated signalling driven by these proteins.

PIK3CA hotspot mutations differentially impact responses to MET targeting in MET-driven and non-driven preclinical cancer models

Background

The MET receptor tyrosine kinase represents a promising target in cancer. PIK3CA activating mutations are common in several tumor types and can potentially confer resistance to anti-receptor tyrosine kinase therapy.

Methods

MET and/or PI3K pathway inhibition was assessed in NIH3T3 cells harboring MET-activating point mutation with or without ectopic expression of PIK3CA^E545K and PIK3CA^H1047R, as well as in MET-expressing head and neck cancer cells with endogenous PIK3CA mutations. Endpoints included PI3K pathway activation, cell proliferation, colony-forming ability, cell death, wound-healing, and an in vivo model.

Results

PIK3CA^E545K and PIK3CA^H1047R confer resistance to MET inhibition in MET-driven models. PIK3CA^H1047R was more potent than PIK3CA^E545K at inducing resistance in PI3K pathway activation, cell proliferation, colony-forming ability, induction of cell death and wound-healing upon MET inhibition. Resistance to MET inhibition could be synergistically overcome by co-targeting PI3K. Furthermore, combined MET/PI3K inhibition led to enhanced anti-tumor activity in vivo in tumors harboring PIK3CA^H1047R. In head and neck cancer cells the combination of MET/PI3K inhibitors led to more-than-additive effects.

Conclusions

PIK3CA mutations can lead to resistance to MET inhibition, supporting future clinical evaluation of combinations of PI3K and MET inhibitors in common scenarios of malignant neoplasms featuring aberrant MET expression and PIK3CA mutations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-017-0660-5) contains supplementary material, which is available to authorized users.

Software toolbox for analysis of the endometrial myometrial junction - a pilot study

PURPOSE

To develop and evaluate an algorithm for computerized evaluation and measurement of the endometrial-myometrial junction (EMJ).

MATERIALS AND METHODS

The advanced image processing toolbox of the Matlab software package was used for identificiation and quantitative analysis of the EMJ area on three-dimensional (3D) rendered coronal plane uterine images, with clear-cut borders of the EMJ. The algorithm was used to process the images and calculate the geometric parameters characterizing the identified EM The manual measurements of the maximum thickness of the EMJ were compared to automated measurements performed by the algorithm on the same images.

RESULTS

For all three interfaces, the mean maximum manual measurement was less than the mean maximui computed measurement. The differences between the two measurements were not statistically significant (p = 0.275, 0.608 and 0.41 for the right wall, left wall, and fundus, respectively). The mean systematic and random errors ranged from 5.4% tol9.3% and 20.4 to 48.6%, respectively. Pearson correlations for the right wall, left wall and fundus (r = 0.642, p = 0.001; r = 0.730, p < 0.001, and r 0.694, p < 0.001, respectively) were good.

CONCLUSIONS

Maximum EMJ thickness measurements performed by the innovative Matla software algorithm are as accurate as manual measurements, and have the potential to reduce inter-observer variability.

Abstract A20: The DNA damage-induced phosphoproteome is modulated by inhibition of the MET receptor

Ionizing radiation (IR) is frequently used in the treatment of a variety of malignant tumors of different origins and stages. In recent years, numerous studies have demonstrated that interfering with signaling via growth factor receptor tyrosine kinases (RTKs) can increase the sensitivity of certain tumors to IR. The RTK for hepatocyte growth factor MET is aberrantly activated in numerous types of human malignancies. MET inhibition has been shown to synergize with DNA damaging agents in generation of DNA damage and to interfere with damage repair. In this study, we aimed to explore how the cellular response to ionizing radiation is modulated by MET inhibition.

We have conducted an immunoaffinity-based LC-MS/MS phosphoproteomics survey study to explore the cellular phosphoproteome following exposure of MET-addicted cancer cells to MET inhibition alone and in combination with IR. Phosphorylation sites of interest have been examined using selected reaction monitoring (SRM) and further validated in vitro and in vivo by Western blotting and immunohistochemistry, respectively.

Analysis of the survey data has identified more than 300 phosphopeptides which have changed in one experimental condition or more. Several of these phosphorylation changes have been confirmed and further investigated by targeted proteomics. These results have pointed to a sub-network of the DNA damage response (DDR) that is modulated in MET-addicted cancer cells upon DNA damage and MET inhibition. The resulting molecular signature present solely in MET-addicted systems could be responsible for the synergism observed between MET inhibition and DNA-damaging agents. We believe that these results will aid in understanding as how MET signaling crosstalks with the DDR with subsequent translational therapeutic clinical applications.

Citation Format: Ariel Bensimon, Yitzhak Zimmer, Paola Francica, Jonas P. Koch, Astrid A. Glück, Daniel M. Aebersold, Ruedi Aebersold, Michaela Medova. The DNA damage-induced phosphoproteome is modulated by inhibition of the MET receptor. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Targeting the Vulnerabilities of Cancer; May 16-19, 2016; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(1_Suppl):Abstract nr A20.

Depletion of FOXM1 via MET Targeting Underlies Establishment of a DNA Damage-Induced Senescence Program in Gastric Cancer

PURPOSE

Deregulated signaling via the MET receptor tyrosine kinase is abundant in gastric tumors, with up to 80% of cases displaying aberrant MET expression. A growing body of evidence suggests MET as a potential target for tumor radiosensitization.

EXPERIMENTAL DESIGN

Cellular proliferation and DNA damage-induced senescence were studied in a panel of MET-overexpressing human gastric cancer cell lines as well as in xenograft models after MET inhibition and/or ionizing radiation. Pathways activation and protein expression were assessed by immunoblotting and immunohistochemistry. Tumor tissue microarrays (91 gastric cancer patients) were generated and copy number alteration (178 patients) and gene expression (373 patients) data available at The Cancer Genome Atlas were analyzed to assess the coalterations of MET and FOXM1.

RESULTS

MET targeting administered before ionizing radiation instigates DNA damage-induced senescence (∼80%, P < 0.001) rather than cell death. MET inhibition-associated senescence is linked to the blockade of MAPK pathway, correlates with downregulation of FOXM1, and can be abrogated (11.8% vs. 95.3%, P < 0.001) by ectopic expression of FOXM1 in the corresponding gastric tumor cells. Cells with ectopic FOXM1 expression demonstrate considerable (∼20%, P < 0.001) growth advantage despite MET targeting, suggesting a novel clinically relevant resistance mechanism to MET inhibition as the copresence of both MET and FOXM1 protein (33%) and mRNA (30%) overexpression as well as gene amplification (24,7%) are common in patients with gastric cancer.

CONCLUSIONS

FOXM1, a negative regulator of senescence, has been identified as a key downstream effector and potential clinical biomarker that mediates MET signaling following infliction of DNA damage in gastric tumors. Clin Cancer Res; 22(21); 5322-36. ©2016 AACR.

Impact of MET targeting on tumor-associated angiogenesis and growth of MET mutations-driven models of liver cancer

Deregulated expression of the MET receptor tyrosine kinase has been reported in up to 50% of patients with hepatocellular carcinoma, the most abundant form of liver cancers, and is associated with decreased survival. Consequently, MET is considered as a molecular target in this malignancy, whose progression is highly dependent on extensive angiogenesis. Here we studied the impact of MET small molecule inhibitors on angiogenesis-associated parameters and growth of xenograft liver models consisting of cells expressing MET-mutated variants M1268T and Y1248H, which exhibit constitutive kinase activity. We demonstrate that MET mutations expression is associated with significantly increased production of vascular endothelial growth factor, which is blocked by MET targeting only in cells expressing the M1268T inhibitor-sensitive but not in the Y1248H inhibitor-resistant variant. Decrease in vascular endothelial growth factor production is also associated with reduction of tyrosine phopshorylation of the vascular endothelial growth factor receptor 2 expressed on primary liver sinusoidal endothelial cells and with inhibition of vessel formation. Furthermore, MET inhibition demonstrated an efficient anti-tumor activity and considerable reduction in microvessel density only against the M1268T-derived intrahepatic tumors. Collectively, our data support the role of targeting MET-associated angiogenesis as a major biological determinant for liver tumor growth control.

Impact of p53 Status on Radiosensitization of Tumor Cells by MET Inhibition-Associated Checkpoint Abrogation

Signaling via the MET receptor tyrosine kinase has been implicated in crosstalk with cellular responses to DNA damage. Our group previously demonstrated that MET inhibition in tumor cells with deregulated MET activity results in radiosensitization via downregulation of the ATR-CHK1-CDC25 pathway, a major signaling cascade responsible for intra-S and G2-M cell-cycle arrest following DNA damage. Here we aimed at studying the potential therapeutic application of ionizing radiation in combination with a MET inhibitor, EMD-1214063, in p53-deficient cancer cells that harbor impaired G1-S checkpoint regulation upon DNA damage. We hypothesized that upon MET inhibition, p53-deficient cells would bypass both G1-S and G2-M checkpoints, promoting premature mitotic entry with substantial DNA lesions and cell death in a greater extent than p53-proficient cells. Our data suggest that p53-deficient cells are more susceptible to EMD-1214063 and combined treatment with irradiation than wild-type p53 lines as inferred from elevated γH2AX expression and increased cytotoxicity. Furthermore, cell-cycle distribution profiling indicates constantly lower G1 and higher G2-M population as well as higher expression of a mitotic marker p-histone H3 following the dual treatment in p53 knockdown isogenic variant, compared with the parental counterpart.

IMPLICATIONS

The concept of MET inhibition-mediated radiosensitization enhanced by p53 deficiency is of high clinical relevance, as p53 is frequently mutated in numerous types of human cancer. The current data point for a therapeutic advantage for an approach combining MET targeting along with DNA-damaging agents for MET-positive/p53-negative tumors.

KRAS and HRAS mutations confer resistance to MET targeting in preclinical models of MET-expressing tumor cells

The MET receptor tyrosine kinase is often deregulated in human cancers and several MET inhibitors are evaluated in clinical trials. Similarly to EGFR, MET signals through the RAS-RAF-ERK/MAPK pathway which plays key roles in cell proliferation and survival. Mutations of genes encoding for RAS proteins, particularly in KRAS, are commonly found in various tumors and are associated with constitutive activation of the MAPK pathway. It was shown for EGFR, that KRAS mutations render upstream EGFR inhibition ineffective in EGFR-positive colorectal cancers. Currently, there are no clinical studies evaluating MET inhibition impairment due to RAS mutations. To test the impact of RAS mutations on MET targeting, we generated tumor cells responsive to the MET inhibitor EMD1214063 that express KRAS G12V, G12D, G13D and HRAS G12V variants. We demonstrate that these MAPK-activating RAS mutations differentially interfere with MET-mediated biological effects of MET inhibition. We report increased residual ERK1/2 phosphorylation indicating that the downstream pathway remains active in presence of MET inhibition. Consequently, RAS variants counteracted MET inhibition-induced morphological changes as well as anti-proliferative and anchorage-independent growth effects. The effect of RAS mutants was reversed when MET inhibition was combined with MEK inhibitors AZD6244 and UO126. In an in vivo mouse xenograft model, MET-driven tumors harboring mutated RAS displayed resistance to MET inhibition. Taken together, our results demonstrate for the first time in details the role of KRAS and HRAS mutations in resistance to MET inhibition and suggest targeting both MET and MEK as an effective strategy when both oncogenic drivers are expressed.

Abstract C218: Relevance of p53 status for the response of tumor cells to MET inhibitors combined with irradiation

The MET receptor tyrosine kinase is an established molecular target for cancer treatment due to the receptor driven uncontrolled cell proliferation, angiogenesis, local invasion and metastasis. Several studies reported that MET signaling may crosstalk with cellular responses to DNA damage and protect tumor cells from cancer treatment with DNA damaging agents including ionizing radiation (IR).

In this respect, our group previously demonstrated that MET inhibition in tumor cells with deregulated MET activity results in their sensitization to IR. Recent finding suggests that this radiosensitization is accompanied by the MET inhibition associated downregulation of ATR-Chk1-CDC25 pathway, a major signaling cascade responsible for the intra-S and G2/M cell cycle arrests following DNA damage. Here we hypothesized that further improvement of the efficacy of IR in combination with MET inhibition in p53-proficient cancer cells could be achieved by a p53 knock-down that would disrupt the remaining G1/S checkpoint arrest. Consequently, tumor cells revealing abrogated both G2/M and G1/S checkpoints would enter mitosis carrying substantial DNA lesions and undergo cell death in a greater extent than p53-proficient cells with functional G1/S checkpoint.

In order to validate our working hypothesis, GTL-16, a human gastric carcinoma line that reveals MET-dependence and expresses wildtype p53, was used to generate p53-proficient and p53-deficient isogenic cell lines. Following combined treatment of novel selective MET small molecule inhibitor EMD-1214063 and IR, various biological endpoints, such as viability, cytotoxicity, apoptosis, and cell cycle distribution were evaluated in p53 knock-down cells along with their corresponding parental variants.

The data suggests that p53-deficient cells are more susceptible to EMD-1214063 and combination treatment than the wildtype-p53 lines as inferred from elevated γH2AX expression and increased cell death. Furthermore, cell cycle distribution profile indicates constantly lower G1 and higher G2/M population as well as up to 3-fold higher expression of a mitotic marker p-Histone H3 Ser10 following MET inhibition combined with IR in p53 knock-down variant as compared to p53 wildtype cells. Interestingly, p53-deficient cells treated by EMD-1214063/IR tend to be rather resistant to apoptosis, suggesting cell death through an alternative mechanism (i.e. mitotic catastrophe). This assumption is supported by imaging analysis that indicates formation of micronuclei in these cells.

The concept of MET inhibition-mediated radiosensitization enhanced by p53 deficiency reported in our current work is of high clinical relevance, since p53 is frequently inactivated as a consequence of mutations in numerous types of human cancer and has the potential to overcome the major challenge in cancer treatment due to tumor resistance to conventional chemo- and radiation therapy.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C218.

Citation Format: Kei Mikami, Michaela Medová, Bruno Streit, Mario P. Tschan, Andree Blaukat, Friedhelm Bladt, Daniel M. Aebersold, Yitzhak Zimmer. Relevance of p53 status for the response of tumor cells to MET inhibitors combined with irradiation. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C218.

The novel ATP-competitive inhibitor of the MET hepatocyte growth factor receptor EMD1214063 displays inhibitory activity against selected MET-mutated variants

The receptor tyrosine kinase MET is a prime target in clinical oncology due to its aberrant activation and involvement in the pathogenesis of a broad spectrum of malignancies. Similar to other targeted kinases, primary and secondary mutations seem to represent an important resistance mechanism to MET inhibitors. Here, we report the biologic activity of a novel MET inhibitor, EMD1214063, on cells that ectopically express the mutated MET variants M1268T, Y1248H, H1112Y, L1213V, H1112L, V1110I, V1206L, and V1238I. Our results show a dose-dependent decrease in MET autophosphorylation in response to EMD1214063 in five of the eight cell lines (IC50 2-43 nmol/L). Blockade of MET by EMD1214063 was accompanied by a reduced activation of downstream effectors in cells expressing EMD1214063-sensitive mutants. In all sensitive mutant-expressing lines, EMD1214063 altered cell-cycle distribution, primarily with an increase in G1 phase. EMD1214063 strongly influenced MET-driven biologic functions, such as cellular morphology, MET-dependent cell motility, and anchorage-independent growth. To assess the in vivo efficacy of EMD1214063, we used a xenograft tumor model in immunocompromised mice bearing NIH3T3 cells expressing sensitive and resistant MET-mutated variants. Animals were randomized for the treatment with EMD1214063 (50 mg/kg/d) or vehicle only. Remarkably, five days of EMD1214063 treatment resulted in a complete regression of the sensitive H1112L-derived tumors, whereas tumor growth remained unaffected in mice with L1213V tumors and in vehicle-treated animals. Collectively, the current data identifies EMD1214063 as a potent MET small-molecule inhibitor with selective activity towards mutated MET variants.

Protective autophagy is involved in resistance towards MET inhibitors in human gastric adenocarcinoma cells

MET, also known as hepatocyte growth factor receptor (HGFR), is a receptor tyrosine kinase with an important role, both in normal cellular function as well as in oncogenesis. In many cancer types, abnormal activation of MET is related to poor prognosis and various strategies to inhibit its function, including small molecule inhibitors, are currently in preclinical and clinical evaluation. Autophagy, a self-digesting recycling mechanism with cytoprotective functions, is induced by cellular stress. This process is also induced upon cytotoxic drug treatment of cancer cells and partially allows these cells to escape cell death. Thus, since autophagy protects different tumor cells from chemotherapy-induced cell death, current clinical trials aim at combining autophagy inhibitors with different cancer treatments. We found that in a gastric adenocarcinoma cell line GTL-16, where MET activity is deregulated due to receptor overexpression, two different MET inhibitors PHA665752 and EMD1214063 lead to cell death paralleled by the induction of autophagy. A combined treatment of MET inhibitors together with the autophagy inhibitor 3-MA or genetically impairing autophagy by knocking down the key autophagy gene ATG7 further decreased cell viability of gastric cancer cells. In general, we observed the induction of cytoprotective autophagy in MET expressing cells upon MET inhibition and a combination of MET and autophagy inhibition resulted in significantly decreased cell viability in gastric cancer cells.

Abstract 1909: Cytoprotective autophagy is involved in resistance towards MET inhibitors in human gastric adenocarcinoma cells

MET, also known as hepatocyte growth factor receptor, is a receptor tyrosine kinase (RTK) that plays an important role both in normal cellular function as well as in oncogenesis. In many different cancer types, abnormal activation of MET is related to poor prognosis and various strategies to inhibit its function, including small molecule inhibitors, are currently in preclinical and clinical evaluation. Although promising results have been obtained with a variety of different MET RTK inhibitors, different resistance mechanisms were found. We hypothesized that autophagy, a self-digesting recycling mechanism for cellular organelles and macromolecules with cytoprotective functions, might be involved in resistance towards MET inhibitors. Autophagy induced upon MET inhibition might support cancer cell survival. We therefore aimed at investigating the involvement of autophagy upon MET inhibition in GTL-16 gastric adenocarcinoma cells. First, we treated GTL-16 cells with the MET inhibitor PHA665752. We observed a marked induction of autophagy in these cells upon MET inhibition as measured by LC3I/LC3II conversion and GFP-LC3 dot formation. Similar results were seen in another gastric adenocarcinoma cell line, namely MKN-45. Next, to investigate if MET inhibition-mediated induction of autophagy is a protective mechanism, we treated GTL-16 cells with PHA665752 in combination with compounds that influence autophagic activity. Interestingly, a combination treatment of MET and autophagy inhibitors (3-Methyladenine, 3-MA) significantly (MWU, p&lt;0.001) decreased cell viability as determined by an MTT assay. In contrast, using the autophagy activator lithium chloride in combination with MET inhibitors, cell viability was significantly increased (p&lt;0.01). All data were confirmed using a second MET-inhibitor. To exclude that 3-MA autophagy independent functions account for the increased cell death during treatment with PHA665752, we inhibited autophagy by knocking down the key autophagy gene ATG7 in GTL-16 cells using lentiviral vectors expression small hairpin (sh)RNA targeting ATG7. These “autophagy knockdown” GTL-16 cells displayed a significant increase in cell death upon MET inhibition as compared to GTL-16 control cells expressing a scrambled control shRNA. In conclusion, our results point to a cytoprotective function of autophagy in response to MET inhibition. The use of MET in combination with autophagy inhibitors may represent a novel therapeutic option for the treatment of gastric carcinoma with aberrant MET activity.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1909. doi:1538-7445.AM2012-1909

Abstract 1786: Characterization of the inhibitory capacity of EMD1214063, a novel small molecule inhibitor of the MET hepatocyte growth factor receptor on a panel of MET mutated variants

The receptor tyrosine kinase MET is a prime target in clinical oncology because of its aberrant activation in a broad spectrum of malignancies. Here, we tested the anti tumor activity of a novel MET inhibitor, EMD1214063, on cancer cells overexpressing MET and in eight transfected NIH3T3 cell lines expressing different activating mutants of the MET kinase. Our results demonstrate a dose-dependent decrease in MET autophosphorylation in both MET overexpressing cell lines (IC50 of 20nM and 30nM for GTL-16 and H1993, respectively) and in six of the eight cell lines transfected with MET activating mutants (IC50 5-18nM). Blockade of MET by EMD1214063 resulted in reduced downstream activation of AKT, ERK and PLCγ. In contrast, lack of MET inhibition by EMD1214063 in the resistant Y1248H and L1213V MET mutants was associated with high levels of AKT, ERK and PLCγ activation. In all sensitive mutants, EMD1214063 attenuated MET-dependent cellular proliferation and significantly altered cell cycle distribution profiles (increase in G1 and concomitant decrease of S phase). Furthermore, EMD1214063 strongly affected MET-driven biological functions, such as cellular morphology, motility and anchorage-independent growth. To assess the in vivo efficacy of EMD1214063, we established tumor transplantation models exploiting NIH3T3 cells expressing the H1112L or L1213V MET mutants, respectively sensitive and resistant, to in vitro treatment with EMD1214063. Animals bearing H1112L or L1213V tumors were randomized for the treatment with EMD1214063 (50mg/kg/day) or vehicle only. Remarkably, 5 days of treatment with EMD1214063 induced complete regression of sensitive H1112L tumors, while tumor growth remained unaffected in mice injected with resistant L1213V tumor cells and in vehicle-treated mice. Taken together, these results underscore the concordance between in vitro and in vivo effects of EMD1214063 and strongly support its efficacy in inhibiting MET-driven tumor cell growth.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1786. doi:1538-7445.AM2012-1786

MET Inhibition Results in DNA Breaks and Synergistically Sensitizes Tumor Cells to DNA-Damaging Agents Potentially by Breaching a Damage-Induced Checkpoint Arrest

While recent studies implicate that signaling through the receptor tyrosine kinase MET protects cancer cells from DNA damage, molecular events linking MET to the DNA damage response machinery are largely unknown. Here, we studied the impact of MET inhibition by the small molecule PHA665752 on cytotoxicity induced by DNA-damaging agents. We demonstrate that PHA665752 reduces clonogenic survival of tumor cells with MET overexpression when combined with ionizing radiation and synergistically cooperates with ionizing radiation or adriamycin to induce apoptosis. In search of mechanisms underlying the observed synergism, we show that PHA665752 alone considerably increases γH2AX levels, indicating the accumulation of double-strand DNA breaks. In addition, PHA665752 treatment results in sustained high levels of γH2AX and phosphorylated ATM postirradiation, strengthening the assumption that MET inhibition attenuates postdamage DNA repair. PHA665752, alone or in combination with irradiation, leads also to a massive increase of γH2AX tyrosine phosphorylation and its subsequent interaction with the proapoptotic kinase JNK1. Finally, MET inhibition reduces activation of ATR, CHK1, and CDC25B and abrogates an associated DNA damage-induced S phase arrest. This indicates that MET inhibition compromises a critical damage-dependent checkpoint that may enable DNA-damaged cells to exit cell cycle arrest before repair is completed.

MET inhibition in tumor cells by PHA665752 impairs homologous recombination repair of DNA double strand breaks

Abnormal activation of cellular DNA repair pathways by deregulated signaling of receptor tyrosine kinase systems has broad implications for both cancer biology and treatment. Recent studies suggest a potential link between DNA repair and aberrant activation of the hepatocyte growth factor receptor Mesenchymal-Epithelial Transition (MET), an oncogene that is overexpressed in numerous types of human tumors and considered a prime target in clinical oncology. Using the homologous recombination (HR) direct-repeat direct-repeat green fluorescent protein ((DR)-GFP) system, we show that MET inhibition in tumor cells with deregulated MET activity by the small molecule PHA665752 significantly impairs in a dose-dependent manner HR. Using cells that express MET-mutated variants that respond differentially to PHA665752, we confirm that the observed HR inhibition is indeed MET-dependent. Furthermore, our data also suggest that decline in HR-dependent DNA repair activity is not a secondary effect due to cell cycle alterations caused by PHA665752. Mechanistically, we show that MET inhibition affects the formation of the RAD51-BRCA2 complex, which is crucial for error-free HR repair of double strand DNA lesions, presumably via downregulation and impaired translocation of RAD51 into the nucleus. Taken together, these findings assist to further support the role of MET in the cellular DNA damage response and highlight the potential future benefit of MET inhibitors for the sensitization of tumor cells to DNA damaging agents.

Incidence of small lymph node metastases with evidence of extracapsular extension: clinical implications in patients with head and neck squamous cell carcinoma

PURPOSE

Small lymph nodes (LN) show evidence of extracapsular extension (ECE) in a significant number of patients. This study was performed to determine the impact of ECE in LN ≤7 mm as compared with ECE in larger LN.

METHODS AND MATERIALS

All tumor-positive LN of 74 head and neck squamous cell carcinoma (HNSCC) patients with at least one ECE positive LN were analyzed retrospectively for the LN diameter and the extent of ECE. Clinical endpoints were regional relapse-free survival, distant metastasis-free survival, and overall survival. The median follow-up for the surviving patients was 2.1 years (range, 0.3-9.2 years).

RESULTS

Forty-four of 74 patients (60%) had at least one ECE positive LN ≤10 mm. These small ECE positive LN had a median diameter of 7 mm, which was used as a cutoff. Thirty patients (41%) had at least one ECE positive LN ≤7 mm. In both univariate and multivariate Cox regression analyses, the incidence of at least one ECE positive LN ≤7 mm was a statistically significant prognostic factor for decreased regional relapse-free survival (adjusted hazard ratio [HR]: 2.7, p = 0.03, 95% confidence interval [CI]: 1.1-6.4), distant metastasis-free survival (HR: 2.6, p = 0.04, 95% CI: 1.0-6.6), and overall survival (HR: 2.5, p = 0.03, 95% CI: 1.1-5.8).

CONCLUSIONS

The incidence of small ECE positive LN metastases is a significant prognostic factor in HNSCC patients. Small ECE positive LN may represent more invasive tumor biology and could be used as prognostic markers.

Differential inhibition sensitivities of MET mutants to the small molecule inhibitor SU11274

Point mutations emerge as one of the rate-limiting steps in tumor response to small molecule inhibitors of protein kinases. Here we characterized the response of the MET mutated variants, V1110I, V1238I, V1206L and H1112L to the small molecule SU11274. Our results reveal a distinct inhibition pattern of the four mutations with IC(50) values for autophosphorylation inhibition ranging between 0.15 and 1.5muM. Differences were further seen on the ability of SU11274 to inhibit phosphorylation of downstream MET transducers such as AKT, ERK, PLCgamma and STAT3 and a variety of MET-dependent biological endpoints. In all the assays, H1112L was the most sensitive to SU11274, while V1206L was less affected under the used concentration range. The differences in responses to SU11274 are discussed based on a structural model of the MET kinase domain.

Hsp90 transcriptionally and post-translationally regulates the expression of NDRG1 and maintains the stability of its modifying kinase GSK3beta

N-myc downstream-regulated gene 1 (NRDG1) is a stress-induced protein whose putative function is suppression of tumor metastasis. A recent proteonomic study showed NDRG1 interacts with the molecular chaperone heat shock protein 90 (Hsp90). From their reported association, we investigated if NDRG1 is dependent on Hsp90 for its stability and is therefore a yet unidentified Hsp90 client protein. Here, we demonstrate that endogenous NDRG1 and Hsp90 physically associate in hepatocellular cancer cell lines. However, geldanamycin (GA)-mediated inhibition of Hsp90 did not disrupt their interaction or result in NDRG1 protein destabilization. On the contrary, inhibition of Hsp90 led to a transcriptional increase of NDRG1 protein which was associated with cell growth arrest. We also observed that GA inhibited the phosphorylation of NDRG1 by targeting its regulating kinases, serum- and glucocorticoid-induced kinase 1 (SGK1) and glycogen synthase kinase 3 beta (GSK3beta). We demonstrate that in the presence of GA, GSK3beta protein and activity were decreased thus indicating that Hsp90 is necessary for GSK3beta stability. Taken together, our data demonstrate that NDRG1 is not a classic client protein but interacts with Hsp90 and is still dually regulated by Hsp90 at a transcriptional and post-translational level. Finally, we suggest for the first time GSK3beta as a new client protein of Hsp90.

MET Y1253D-activating point mutation and development of distant metastasis in advanced head and neck cancers

We investigated if the MET-activating point mutation Y1253D influences clinical outcomes in patients with advanced squamous cell carcinoma of the head and neck (HNSCC). The study population consisted of 152 HNSCC patients treated by hyperfractionated radiotherapy alone or concomitant with chemotherapy between September 1994 and July 2000. Tumors were screened for the presence of the MET-activating point mutation Y1253D. Seventy-eight patients (51%) received radiotherapy alone, 74 patients (49%) underwent radiotherapy concomitant with chemotherapy. Median patient age was 54 years and median follow-up was 5.5 years. Distant metastasis-free survival, local relapse-free survival and overall survival were compared with MET Y1253D status. During follow-up, 29 (19%) patients developed distant metastasis. MET Y1253D was detected in tumors of 21 out of 152 patients (14%). Distant metastasis-free survival (P = 0.008) was associated with MET Y1253D. In a multivariate Cox regression model, adjusted for T-category, only presence of MET Y1253D was associated with decreased distant metastasis-free survival: hazard ratio = 2.5 (95% confidence interval: 1.1, 5.8). The observed association between MET Y1253D-activating point mutation and decreased distant metastasis-free survival in advanced HNSCC suggests that MET may be a potential target for specific treatment interventions.