A senescence restriction point acting on chromatin integrates oncogenic signals

We identify a senescence restriction point (SeRP) as a critical event for cells to commit to senescence. The SeRP integrates the intensity and duration of oncogenic stress, keeps a memory of previous stresses, and combines oncogenic signals acting on different pathways by modulating chromatin accessibility. Chromatin regions opened upon commitment to senescence are enriched in nucleolar-associated domains, which are gene-poor regions enriched in repeated sequences. Once committed to senescence, cells no longer depend on the initial stress signal and exhibit a characteristic transcriptome regulated by a transcription factor network that includes ETV4, RUNX1, OCT1, and MAFB. Consistent with a tumor suppressor role for this network, the levels of ETV4 and RUNX1 are very high in benign lesions of the pancreas but decrease dramatically in pancreatic ductal adenocarcinomas. The discovery of senescence commitment and its chromatin-linked regulation suggests potential strategies for reinstating tumor suppression in human cancers.

LKB1-SIK2 loss drives uveal melanoma proliferation and hypersensitivity to SLC8A1 and ROS inhibition

Metastatic uveal melanomas are highly resistant to all existing treatments. To address this critical issue, we performed a kinome-wide CRISPR-Cas9 knockout screen, which revealed the LKB1-SIK2 module in restraining uveal melanoma tumorigenesis. Functionally, LKB1 loss enhances proliferation and survival through SIK2 inhibition and upregulation of the sodium/calcium (Na+ /Ca2+ ) exchanger SLC8A1. This signaling cascade promotes increased levels of intracellular calcium and mitochondrial reactive oxygen species, two hallmarks of cancer. We further demonstrate that combination of an SLC8A1 inhibitor and a mitochondria-targeted antioxidant promotes enhanced cell death efficacy in LKB1- and SIK2-negative uveal melanoma cells compared to control cells. Our study also identified an LKB1-loss gene signature for the survival prognostic of patients with uveal melanoma that may be also predictive of response to the therapy combination. Our data thus identify not only metabolic vulnerabilities but also new prognostic markers, thereby providing a therapeutic strategy for particular subtypes of metastatic uveal melanoma.

Development of ELIP to Assess Physical Literacy for Emerging Adults: A Methodological and Epistemological Challenge

Purpose: Following increased interest in physical literacy (PL), development of appropriate tools for assessment has become an important next step for its operationalization. To forward the development of such tools, the objective of this study was to build the foundations of the Évaluation de la Littératie Physique (ELIP), designed to help reduce existing tensions in approaches to PL assessment that may be resulting in a low uptake into applied settings. Methods: We followed two steps: (1) the development of the first version of ELIP by deploying a Delphi method (n = 30); and (2) the modification of items through cognitive interviews with emerging adults (n = 32). Results: The expert consensus highlighted four dimensions of PL to be assessed-physical; affective; cognitive; and social-with new perspectives, including a preference for broad motor tests over fitness. Conclusion: Results offer new insights into the assessment of emerging adults' PL, but ELIP still requires further work concerning validity, reliability, and sensitivity.

A preliminary validation of the pediatric adaptation of the Insomnia Severity Index

INTRODUCTION

The prevalence of insomnia in children aged 5 to 12 years old is 20% to 31%. Currently, there is no well-validated questionnaire assessing all the components of insomnia in school-aged children. The present study aims to introduce an adaptation of the Insomnia Severity Index for this purpose.

METHOD

Fifty-nine children aged 8- to 12-years-old with at least one anxiety disorder were recruited from youth mental health care settings. Their parents completed the pediatric adaptation of the Insomnia Severity Index which includes two scales used to report insomnia symptoms in children and their impact on the child (ISI-Child) and parents (ISI-Parent), My Child's Sleep Habits questionnaire, and the Child Behavior Checklist.

RESULTS

Both the ISI-Child and the ISI-Parent scales presented adequate factorial structure (RMSEA ≤ 0.05) and internal consistency (ISI-Child: α=0.87; ISI-Parent: α=0.88). Furthermore, the results of the two scales were strongly correlated (r=0.91, P<0.001). The convergent validity was assessed using the Waking During the Night scale of the My Child's Sleep Habits questionnaire and was adequate for the ISI-Child (r=0.52, P<0.001) and the ISI-Parent (r=0.53, P<0.001). Finally, the Rule-Breaking Behavior (r ≤ 0.26, P ≥ 0.05) and Aggressive Behavior (r ≤ 0.19, P ≥ 0.19) scales of the Child Behavior Checklist showed small correlations with both subscales, indicating good divergent validity.

CONCLUSION

The pediatric adaptation of the Insomnia Severity Index is a potentially reliable and valid measure for screening and assessing insomnia in children.

Homogeneity in immune features between colorectal liver metastases better identifies patients with good prognosis compared to pathological response to preoperative chemotherapy

In colorectal cancer liver metastases (CRLM), the density of tumor-infiltrating lymphocytes, the expression of class I major histocompatibility complex (MHC-I), and the pathological response to preoperative chemotherapy have been associated with oncological outcomes after complete resection. However, the prognostic significance of the heterogeneity of these features in patients with multiple CRLMs remains under investigation. We used a tissue microarray of 220 mismatch repair-gene proficient CRLMs resected in 97 patients followed prospectively to quantify CD3+ T cells and MHC-I by immunohistochemistry. Histopathological response to preoperative chemotherapy was assessed using standard scoring systems. We tested associations between clinical, immunological, and pathological features with oncologic outcomes. Overall, 29 patients (30.2%) had CRLMs homogeneous for CD3+ T cell infiltration and MHC-I. Patients with immune homogeneous compared to heterogeneous CRLMs had longer median time to recurrence (TTR) (30 vs. 12 months, p = .0018) and disease-specific survival (DSS) (not reached vs. 48 months, p = .0009). At 6 years, 80% of the patients with immune homogeneous CRLMs were still alive. Homogeneity of response to preoperative chemotherapy was seen in 60 (61.9%) and 69 (80.2%) patients according to different grading systems and was not associated with TTR or DSS. CD3 and MHC-I heterogeneity was independent of response to pre-operative chemotherapy and of other clinicopathological variables for their association with oncological outcomes. In patients with multiple CRLMs resected with curative intent, similar adaptive immune features seen across metastases could be more informative than pathological response to pre-operative chemotherapy in predicting oncological outcomes.

Radiomics using computed tomography to predict CD73 expression and prognosis of colorectal cancer liver metastases

BACKGROUND

Finding a noninvasive radiomic surrogate of tumor immune features could help identify patients more likely to respond to novel immune checkpoint inhibitors. Particularly, CD73 is an ectonucleotidase that catalyzes the breakdown of extracellular AMP into immunosuppressive adenosine, which can be blocked by therapeutic antibodies. High CD73 expression in colorectal cancer liver metastasis (CRLM) resected with curative intent is associated with early recurrence and shorter patient survival. The aim of this study was hence to evaluate whether machine learning analysis of preoperative liver CT-scan could estimate high vs low CD73 expression in CRLM and whether such radiomic score would have a prognostic significance.

METHODS

We trained an Attentive Interpretable Tabular Learning (TabNet) model to predict, from preoperative CT images, stratified expression levels of CD73 (CD73^High vs. CD73^Low) assessed by immunofluorescence (IF) on tissue microarrays. Radiomic features were extracted from 160 segmented CRLM of 122 patients with matched IF data, preprocessed and used to train the predictive model. We applied a five-fold cross-validation and validated the performance on a hold-out test set.

RESULTS

TabNet provided areas under the receiver operating characteristic curve of 0.95 (95% CI 0.87 to 1.0) and 0.79 (0.65 to 0.92) on the training and hold-out test sets respectively, and outperformed other machine learning models. The TabNet-derived score, termed rad-CD73, was positively correlated with CD73 histological expression in matched CRLM (Spearman's ρ = 0.6004; P < 0.0001). The median time to recurrence (TTR) and disease-specific survival (DSS) after CRLM resection in rad-CD73^High vs rad-CD73^Low patients was 13.0 vs 23.6 months (P = 0.0098) and 53.4 vs 126.0 months (P = 0.0222), respectively. The prognostic value of rad-CD73 was independent of the standard clinical risk score, for both TTR (HR = 2.11, 95% CI 1.30 to 3.45, P < 0.005) and DSS (HR = 1.88, 95% CI 1.11 to 3.18, P = 0.020).

CONCLUSIONS

Our findings reveal promising results for non-invasive CT-scan-based prediction of CD73 expression in CRLM and warrant further validation as to whether rad-CD73 could assist oncologists as a biomarker of prognosis and response to immunotherapies targeting the adenosine pathway.

Metabolomics-Guided Identification of a Distinctive Hepatocellular Carcinoma Signature

BACKGROUND

Hepatocellular carcinoma (HCC) is a major contributor to cancer-related morbidity and mortality burdens globally. Given the fundamental metabolic activity of hepatocytes within the liver, hepatocarcinogenesis is bound to be characterized by alterations in metabolite profiles as a manifestation of metabolic reprogramming.

METHODS

HCC and adjacent non-tumoral liver specimens were obtained from patients after HCC resection. Global patterns in tissue metabolites were identified using non-targeted ¹H Nuclear Magnetic Resonance (¹H-NMR) spectroscopy whereas specific metabolites were quantified using targeted liquid chromatography-mass spectrometry (LC/MS).

RESULTS

Principal component analysis (PCA) within our ¹H-NMR dataset identified a principal component (PC) one of 53.3%, along which the two sample groups were distinctively clustered. Univariate analysis of tissue specimens identified more than 150 metabolites significantly altered in HCC compared to non-tumoral liver. For LC/MS, PCA identified a PC1 of 45.2%, along which samples from HCC tissues and non-tumoral tissues were clearly separated. Supervised analysis (PLS-DA) identified decreases in tissue glutathione, succinate, glycerol-3-phosphate, alanine, malate, and AMP as the most important contributors to the metabolomic signature of HCC by LC/MS.

CONCLUSIONS

Together, ¹H-NMR and LC/MS metabolomics have the capacity to distinguish HCC from non-tumoral liver. The characterization of such distinct profiles of metabolite abundances underscores the major metabolic alterations that result from hepatocarcinogenesis.

Abstract 4049: TIDAL-01: A selected TIL process that enriches for neoantigen reactive TIL in solid tumors

Background: Tumor infiltrating lymphocyte (TIL) therapy is capable of mediating durable complete responses in melanoma. While solid tumors such as colorectal cancer (CRC), non-small cell lung cancer (NSCLC), ovarian and breast have been shown to contain neoantigen reactive TIL, the success of bulk TIL therapy in these tumors has been limited. Enhancing tumor reactivity through the selective expansion of neoantigen-reactive subpopulations, has demonstrated success in cancers outside of melanoma underscoring the potential of a neoantigen selected TIL approach in indications with lower tumor mutational burdens. Here we demonstrate that the TIDAL-01 process, which utilizes tumor-specific mutation containing peptides to select neoantigen reactive TIL produces TIL products significantly enriched in neoantigen reactivity.

Methods: Fresh tumors were cut into fragments or dissociated and cultured in a primary expansion (preREP). Antigen presenting cells (APCs) were isolated and expanded from patient matched blood. Whole exome and RNA sequencing was performed on tumor tissue and autologous PBMCs and used to predict and prioritize neoantigen mutations. Peptides encoding the mutations were synthesized, loaded onto APCs and co-cultured with autologous TIL. Neoantigen reactive TIL were selected by fluorescence activated cell sorting (FACS), based on the upregulation of the activation markers CD134 and CD137 and expanded with a rapid expansion protocol (REP). Bulk and unselected TIL were expanded alongside for comparison. Neoantigen reactivity was quantified and deconvoluted by cytokine secretion, degranulation, upregulation of CD134/CD137 by flow and when practical, killing of autologous tumor cell lines or organoids.

Results: Successful TIL expansion was achieved in 31/34 (91%) tumors (14/17 CRC, 10/10 NSCLC, 3/3 ovarian and 3/3 melanoma) using both tumor fragments and dissociated tumors. CRC tumors accounted for half of the samples (17/34), and the tumor mutational burden within these samples varied substantially, ranging from 229 to 5436 mutations. Upregulation of CD134 and CD137 and increased IFN-γ production was observed in all samples upon co-culture with peptide loaded APCs. Peptide restimulation and deconvolution revealed that the TIDAL-01 process is capable of enriching for both CD4 and CD8 reactivities. Selected TIL products produced up to 50x more IFN-γ, TNF-α and Granzyme B than bulk TIL and at least 2x higher levels of degranulation, indicative of greater killing potential.

Conclusions: TIL from metastatic CRC, melanoma, NSCLC and ovarian tumors were successfully expanded from the majority of patients. Co-culture of TIL and peptide loaded APCs followed by FACS significantly enriched for neoantigen reactivity compared to bulk TIL, demonstrating the potential of the TIDAL-01 process to produce selected TIL products for the treatment of non-melanoma tumors.

Citation Format: Larissa A. Pikor, Antoine Bernard, Nathalie Brassard, Anna Fritzsche, Anna Kluew, Zachary K. Jilesen, Jake Nikota, Rohan Bareja, Christian Laing, David F. Stojdl, TJ Langer, Stewart Abbot, Barbara Sennino, Simon Turcotte. TIDAL-01: A selected TIL process that enriches for neoantigen reactive TIL in solid tumors. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4049.

How Social Responses to Child Sexual Abuse and Intimate Partner Violence Affect Homelessness Among Women in Two Rural Regions With Resource-Based Economies in Eastern Quebec

This study presents findings from a qualitative study conducted in two relatively remote, primarily rural regions of the Canadian province of Quebec whose resource-based economic structures exacerbate inequalities between men and women. The purpose of this study was to understand how violence and homelessness intertwine in women's life courses in such regions. On the basis of past research showing that gender socialization around traditional roles and conservative values is particularly tenacious in non-urban areas, we conducted life-course interviews with 22 women in 13 different towns and villages of these two regions. Our content analysis of these interviews showed that specific social responses have forced women to maintain relationships with their aggressors or with people who have protected them, thus relegating these women's lives to the private sphere while reducing their opportunities for social participation in the public sphere. These social responses, together with women's economic and social disadvantages in these regions, were also the main factors that explain homelessness experienced by the participants in this study. Our analysis of these responses illustrates the patriarchal social structure of power in these regions, which is perpetuated in the interpersonal, institutional, and representational dimensions and keeps women in precarious, subordinate social positions, while ostracizing or punishing women who try to resist.

CD73 Inhibits cGAS-STING and Cooperates with CD39 to Promote Pancreatic Cancer

The ectonucleotidases CD39 and CD73 catalyze extracellular ATP to immunosuppressive adenosine, and as such, represent potential cancer targets. We investigated biological impacts of CD39 and CD73 in pancreatic ductal adenocarcinoma (PDAC) by studying clinical samples and experimental mouse tumors. Stromal CD39 and tumoral CD73 expression significantly associated with worse survival in human PDAC samples and abolished the favorable prognostic impact associated with the presence of tumor-infiltrating CD8+ T cells. In mouse transplanted KPC tumors, both CD39 and CD73 on myeloid cells, as well as CD73 on tumor cells, promoted polarization of infiltrating myeloid cells towards an M2-like phenotype, which enhanced tumor growth. CD39 on tumor-specific CD8+ T cells and pancreatic stellate cells also suppressed IFNγ production by T cells. Although therapeutic inhibition of CD39 or CD73 alone significantly delayed tumor growth in vivo, targeting of both ectonucleotidases exhibited markedly superior antitumor activity. CD73 expression on human and mouse PDAC tumor cells also protected against DNA damage induced by gemcitabine and irradiation. Accordingly, large-scale pharmacogenomic analyses of human PDAC cell lines revealed significant associations between CD73 expression and gemcitabine chemoresistance. Strikingly, increased DNA damage in CD73-deficient tumor cells associated with activation of the cGAS-STING pathway. Moreover, cGAS expression in mouse KPC tumor cells was required for antitumor activity of the CD73 inhibitor AB680 in vivo. Our study, thus, illuminates molecular mechanisms whereby CD73 and CD39 seemingly cooperate to promote PDAC progression.

MHC Class II Expression Influences the Composition and Distribution of Immune Cells in the Metastatic Colorectal Cancer Microenvironment

Simple Summary

Extensive data exist regarding the importance of major histocompatibility complex (MHC) class I in the tumor microenvironment, but data on MHC class II (MHC-II) are lacking. Using multiplex immunohistochemistry and spatial modeling, we demonstrate that MHC-II expression impacts both the relationships of cells traditionally associated with T lymphocyte priming and spatial interactions of cytotoxic lymphocytes and tumor cells in colorectal cancer.

Abstract

Despite advances in therapy over the past decades, metastatic colorectal cancer (mCRC) remains a highly morbid disease. While the impact of MHC-I on immune infiltration in mCRC has been well studied, data on the consequences of MHC-II loss are lacking. Multiplex fluorescent immunohistochemistry (mfIHC) was performed on 149 patients undergoing curative intent resection for mCRC and stratified into high and low human leukocyte antigen isotype DR (HLA-DR) expressing tumors. Intratumoral HLA-DR expression was found in stromal bands, and its expression level was associated with different infiltrating immune cell makeup and distribution. Low HLA-DR expression was associated with increased intercellular distances and decreased population mixing of T helper cells and antigen-presenting cells (APC), suggestive of decreased interactions. This was associated with less co-localization of tumor cells and cytotoxic T lymphocytes (CTLs), which tended to be in a less activated state as determined by Ki67 and granzyme B expression. These findings suggest that low HLA-DR in the tumor microenvironment of mCRC may reflect a state of poor helper T-cell interactions with APCs and CTL-mediated anti-tumor activity. Efforts to restore/enhance MHC-II presentation may be a useful strategy to enhance checkpoint inhibition therapy in the future.

IL27 Signaling Serves as an Immunologic Checkpoint for Innate Cytotoxic Cells to Promote Hepatocellular Carcinoma

Although inflammatory mechanisms driving hepatocellular carcinoma (HCC) have been proposed, the regulators of anticancer immunity in HCC remain poorly understood. We found that IL27 receptor (IL27R) signaling promotes HCC development in vivo. High IL27EBI3 cytokine or IL27RA expression correlated with poor prognosis for patients with HCC. Loss of IL27R suppressed HCC in vivo in two different models of hepatocarcinogenesis. Mechanistically, IL27R sig-naling within the tumor microenvironment restrains the cytotoxicity of innate cytotoxic lymphocytes. IL27R ablation enhanced their accumulation and activation, whereas depletion or functional impairment of innate cytotoxic cells abrogated the effect of IL27R disruption. Pharmacologic neutralization of IL27 signaling increased infiltration of innate cytotoxic lymphocytes with upregulated cytotoxic molecules and reduced HCC development. Our data reveal an unexpected role of IL27R signaling as an immunologic checkpoint regulating innate cytotoxic lymphocytes and promoting HCC of different etiologies, thus indicating a therapeutic potential for IL27 pathway blockade in HCC.

SIGNIFICANCE

HCC, the most common form of liver cancer, is characterized by a poor survival rate and limited treatment options. The discovery of a novel IL27-dependent mechanism controlling anticancer cytotoxic immune response will pave the road for new treatment options for this devastating disease. This article is highlighted in the In This Issue feature, p. 1825.

Helicobacter pylori serology is associated with worse overall survival in patients with melanoma treated with immune checkpoint inhibitors

The microbiome is now regarded as one of the hallmarks of cancer and several strategies to modify the gut microbiota to improve immune checkpoint inhibitor (ICI) activity are being evaluated in clinical trials. Preliminary data regarding the upper gastro-intestinal microbiota indicated that Helicobacter pylori seropositivity was associated with a negative prognosis in patients amenable to ICI. In 97 patients with advanced melanoma treated with ICI, we assessed the impact of H. pylori on outcomes and microbiome composition. We performed H. pylori serology and profiled the fecal microbiome with metagenomics sequencing. Among the 97 patients, 22% were H. pylori positive (Pos). H. pylori Pos patients had a significantly shorter overall survival (p = .02) compared to H. pylori negative (Neg) patients. In addition, objective response rate and progression-free survival were decreased in H. pylori Pos patients. Metagenomics sequencing did not reveal any difference in diversity indexes between the H. pylori groups. At the taxa level, Eubacterium ventriosum, Mediterraneibacter (Ruminococcus) torques, and Dorea formicigenerans were increased in the H. pylori Pos group, while Alistipes finegoldii, Hungatella hathewayi and Blautia producta were over-represented in the H. pylori Neg group. In a second independent cohort of patients with NSCLC, diversity indexes were similar in both groups and Bacteroides xylanisolvens was increased in H. pylori Neg patients. Our results demonstrated that the negative impact of H. pylori on outcomes seem to be independent from the fecal microbiome composition. These findings warrant further validation and development of therapeutic strategies to eradicate H. pylori in immuno-oncology arena.

Spatially mapping the immune landscape of melanoma using imaging mass cytometry

Melanoma is an immunogenic cancer with a high response rate to immune checkpoint inhibitors (ICIs). It harbors a high mutation burden compared with other cancers and, as a result, has abundant tumor-infiltrating lymphocytes (TILs) within its microenvironment. However, understanding the complex interplay between the stroma, tumor cells, and distinct TIL subsets remains a substantial challenge in immune oncology. To properly study this interplay, quantifying spatial relationships of multiple cell types within the tumor microenvironment is crucial. To address this, we used cytometry time-of-flight (CyTOF) imaging mass cytometry (IMC) to simultaneously quantify the expression of 35 protein markers, characterizing the microenvironment of 5 benign nevi and 67 melanomas. We profiled more than 220,000 individual cells to identify melanoma, lymphocyte subsets, macrophage/monocyte, and stromal cell populations, allowing for in-depth spatial quantification of the melanoma microenvironment. We found that within pretreatment melanomas, the abundance of proliferating antigen-experienced cytotoxic T cells (CD8⁺CD45RO⁺Ki67⁺) and the proximity of antigen-experienced cytotoxic T cells to melanoma cells were associated with positive response to ICIs. Our study highlights the potential of multiplexed single-cell technology to quantify spatial cell-cell interactions within the tumor microenvironment to understand immune therapy responses.

[Distress tolerance and experience of chronic pain]

INTRODUCTION

Chronic pain is a highly prevalent condition that is associated with distressing somatic and emotional experiences. Consequently, an individual's distress tolerance, the perceived capacity to tolerate negative psychological and physical states, may influence their pain experience. This effect could be explained in part by a reduction in the catastrophic interpretation of pain which is associated with increased pain intensity and interference in everyday activities.

AIMS

The first aim of this study was to explore the association between the components of the 5-factor model of distress tolerance and (1) pain intensity and (2) pain interference in everyday activities. The secondary aim was to assess the potential mediating effect of pain catastrophizing in the eventual association between components of distress tolerance and (1) pain intensity or (2) pain interference in everyday activities.

METHOD

This is a cross-sectional study of adult (18 years or older) university students and staff with chronic pain (3 months). They were invited to complete the online questionnaire through an email invitation. Pain intensity and interference in everyday functioning were assessed with the corresponding subscales of the Brief Pain Inventory. The following instruments were used to assess the components of the 5-factor model of distress tolerance: Ambiguity Tolerance Scale (tolerance to ambiguity), Intolerance to Uncertainty Scale (reversed score: tolerance to uncertainty), Discomfort Intolerance Scale (reversed score: discomfort tolerance), Distress Tolerance Scale (tolerance to negative emotions), Frustration Discomfort Scale (tolerance to frustration). Participants also completed the Pain Catastrophizing Scale.

RESULTS

Eighty participants were recruited (57 % women, mean age=33.09; standard deviation=12,87). Tolerance to negative emotions was the only component of distress tolerance that was associated with pain (ß=-0.04; 95% CI): -0.07--0.01; t (78)=-3.06, p<0.01) or pain interference in everyday functioning (ß=-0.07; 95% CI: -0.10--0.03; t (78)=-3.97, p<0.01), independently of the others. Combined with age, these factors explained 16.2 % of the variance in pain intensity and 19.4 % of the variance in pain interference. Pain catastrophizing partially mediated the association between tolerance to negative emotions and pain interference in everyday functioning, but it was not involved in the association between tolerance to negative emotions and pain intensity.

CONCLUSION

Tolerance to negative emotions appears to be the most relevant aspect of distress tolerance in the context of chronic pain and is a potential clinical target that is independent and complementary from pain catastrophizing.

302 Characterization of TIGIT and PVR expression in colorectal liver metastases

Background

Metastatic colorectal cancer (CRC) is common and lethal and generally not responsive to current immunotherapies. We hypothesize that efficacious T cell-based immunotherapy can be developed for this malignancy, provided that immune checkpoints relevant to liver metastasis, the first site of disease progression, are targeted. Here, we characterized CRC liver metastases by RNAseq, FACS and in vitro functional assays to identify candidate immune checkpoints.

Methods

We performed deep RNAseq clustering and differential gene expression analysis on bulk RNA extracted from 52 mismatch repair gene proficient CRC liver metastases. By multiparameter FACS, we analyzed the expression of candidate immune checkpoints in cell suspensions derived from 18 liver metastases, matched non-tumoral livers, and pre-operative PBMCs. We evaluated IFN-γ (ELISA) secretion and tumor lysis (Incucyte) of tumor-infiltrating T lymphocytes (TILs) expanded from liver metastases stimulated by autologous cancer cells with or without monoclonal antibodies blocking candidate immune checkpoints.

Results

Out of 52 metastases, 21 (40.3%) clustered as immune reactive (IR) defined by concurrent high expression of transcripts related to antigen processing, immune cell lineage, immune checkpoints, interferon-gamma response, cytokines, and chemokines, whereas 25 (48.1%) were classified as non-IR. Of all inhibitory ligands assessed, PVR and PVRL2 had the highest expression, both in IR and non-IR metastases, and higher than PD-L1 and PD-L2 expression. The expression of corresponding receptors TIGIT and CD226 was significantly higher in IR compared to non-IR metastases, at absolute levels higher than PD-1. By FACS analysis, PVR and PVRL2 expression by tumor-infiltrating myeloid and tumor cells was higher than PD-L1 and PD-L2 expression. High PVR expression was also found in hepatocytes, liver macrophages and circulating monocytes in the same patients. In TILs, TIGIT was significantly overexpressed in activated CD4+CD25+ (74.8 ±3.0%) and CD8+CD25+ (68.7 ± 8.4%) compared to resting CD25neg T cells, an expression pattern that was not seen for PD-1 or in T cells infiltrating the liver or circulating in the blood. The majority of cancer cell lines derived from liver metastases expressed PVR, but low levels of PD-L1. TIL clones expanded from liver metastases expressed TIGIT at various levels inducible by TCR stimulation. Upon co-culture with autologous cancer cell lines, TIL clones were more lytic and secreted more IFN-γ in presence of anti-TIGIT blocking antibody.

Conclusions

By expression and functional data, the TIGIT/PVR immune suppressive axis appears as a biologically promising target for the development of immunotherapy in patients with CRC metastatic to the liver.

Acknowledgements

This work is supported by Bristol Myers Squibb and by the Quebec Cancer Consortium. A.B. holds a postdoctoral scholarship award from the Institut du cancer de Montréal. S.T. holds a Junior 2 clinical-scientist salary award from the Fond de recherche Santé-Québec. The University of Montreal Roger des Groseillers Research Chair in hepatopancreatobiliary surgical oncology supports the biobanking and clinicopathological database associated with this project.

Ethics Approval

Institutional review board approvals were obtain to conduct this project (16.262) and all patients provided informed consent to contribute to this project with biospecimens and clinicopathological data (09.237).

Predicting the Response to FOLFOX-Based Chemotherapy Regimen from Untreated Liver Metastases on Baseline CT: a Deep Neural Network Approach

In developed countries, colorectal cancer is the second cause of cancer-related mortality. Chemotherapy is considered a standard treatment for colorectal liver metastases (CLM). Among patients who develop CLM, the assessment of patient response to chemotherapy is often required to determine the need for second-line chemotherapy and eligibility for surgery. However, while FOLFOX-based regimens are typically used for CLM treatment, the identification of responsive patients remains elusive. Computer-aided diagnosis systems may provide insight in the classification of liver metastases identified on diagnostic images. In this paper, we propose a fully automated framework based on deep convolutional neural networks (DCNN) which first differentiates treated and untreated lesions to identify new lesions appearing on CT scans, followed by a fully connected neural networks to predict from untreated lesions in pre-treatment computed tomography (CT) for patients with CLM undergoing chemotherapy, their response to a FOLFOX with Bevacizumab regimen as first-line of treatment. The ground truth for assessment of treatment response was histopathology-determined tumor regression grade. Our DCNN approach trained on 444 lesions from 202 patients achieved accuracies of 91% for differentiating treated and untreated lesions, and 78% for predicting the response to FOLFOX-based chemotherapy regimen. Experimental results showed that our method outperformed traditional machine learning algorithms and may allow for the early detection of non-responsive patients.

Outcomes of Older Patients with Resectable Colorectal Liver Metastases Cancer (CRLM): Single Center Experience

Surgery is the only potential curative option of CRLM if resectable. The curative approach in patients over 70 years old is challenging mainly because of comorbidities and other geriatric syndromes. Herein, we report outcomes of older patients with resectable CRLM in our center. We retrospectively analyzed characteristics and outcomes of older patients with CRLM operated at "Centre Hospitalier de l'Université de Montréal" (CHUM) between 2010 and 2019. We identified 210 patients aged ≥70 years with a median age of 76 (range: 70-85). CRLM were synchronous in 56% of patients. Median disease-free survival (DFS) was 41.3 months. Median overall survival (OS) was 62.2 months and estimated 5-year survival rate was 51.5% similar to those of younger counterparts. Patients with metachronous CRLM had a trend to a higher OS compared to those with synchronous disease (67.2 vs. 58.7 months; p = 0.42). Factors associated with lower survival in the multivariate analysis were right-sided tumors and increased Charlson Comorbidity index (CCI). Survival outcomes of patients aged ≥70 years were comparable to those of younger patients and those reported in the literature. Age should not be a limiting factor in the curative management of older patients with resectable CRLM.

Cancer immunotherapy: Macs in the middle

Response to immune checkpoint blockade cancer immunotherapy is variable, but the mechanisms that underlie this variability remain unclear. In a recent issue of Nature Medicine, Yu et al. demonstrate that liver metastases limit immunotherapy efficacy by promoting macrophage-mediated elimination of tumor-specific CD8⁺ T cells. Liver-directed radiotherapy in preclinical models could partially overcome this effect.

Defining best practices for tissue procurement in immuno-oncology clinical trials: consensus statement from the Society for Immunotherapy of Cancer Surgery Committee

Immunotherapy is now a cornerstone for cancer treatment, and much attention has been placed on the identification of prognostic and predictive biomarkers. The success of biomarker development is dependent on accurate and timely collection of biospecimens and high-quality processing, storage and shipping. Tumors are also increasingly used as source material for the generation of therapeutic T cells. There have been few guidelines or consensus statements on how to optimally collect and manage biospecimens and source material being used for immunotherapy and related research. The Society for Immunotherapy of Cancer Surgery Committee has brought together surgical experts from multiple subspecialty disciplines to identify best practices and to provide consensus on how best to access and manage specific tissues for immuno-oncology treatments and clinical investigation. In addition, the committee recommends early integration of surgeons and other interventional physicians with expertise in biospecimen collection, especially in clinical trials, to optimize the quality of tissue and the validity of correlative clinical studies in cancer immunotherapy.

Abstract 5730: A new polyphenol prebiotic isolated from Myrciaria dubia improves gut microbiota composition and increases anti-PD-1 efficacy in murine cancer models

Introduction The gut microbiota influences immune checkpoint inhibitors (ICI) efficacy, and immunogenic commensals bacteria such as Akkermansia muciniphila (AM) and Ruminoccocus are enriched in ICI responder patients. Therefore, strategies to beneficially shift microbiota composition represent a novel therapeutic avenue. Myrciaria dubia (MD) is a polyphenol-rich berry prebiotic that has been recently shown to improve the gut microbiota composition and dampen inflammation in metabolic diseases.

Methods Daily oral administration of MD or water was performed in MCA-205 (PD-1 sensitive) and E0071 (PD-1 resistant) murine tumor models treated with iso-control or anti-PD-1. 16s rRNA gene sequencing and qPCR were used to profile the murine fecal microbiota. Tumor immune infiltration was analyzed by flow cytometry and RNA sequencing. Bile acid levels were measured using liquid chromatography coupled to tandem mass spectrometry in mouse feces and plasma at sacrifice. MD supplementation was also tested in antibiotic-treated mice that had undergone a fecal microbiota transplantation (FMT) using feces from non-responder (NR) and responder (R) non-small cell lung cancer (NSCLC) patients. Finally, to determine the bioactive compound, reverse-phase high performance liquid chromatography was used to isolate fractions that were tested in the MCA-205 tumor model.

Results In MCA-205, MD gavage alone significantly reduced tumor size and in both tumor models MD increased the efficacy of anti-PD-1 compared to water + anti-PD-1. The activity of MD was inhibited upon antibiotics administration. FMT using mouse feces previously treated with MD recreated the effect in MD-naïve mice. Increases in alpha diversity, and AM and Ruminococcaceae were observed in the feces of MD supplemented mice. Serum and fecal CA, αMCA primary and HDCA and DCA secondary bile acids were upregulated in mice treated with MD. The combination of MD + anti-PD-1 increased the frequency of CD8+/CD4+ Treg and ICOS+ expression on CD8+ T cells, while the depletion of the CD8+ cells inhibited the anti-cancer activity. Next, we validated that FMT from NSCLC ICI patients recreated the patients' phenotypes in the MCA-205 tumor model (R vs NR). Treatment with MD resorted anti-PD-1 anti-tumor efficacy post FMT from NR patients. Lastly, we isolated the bioactive polyphenol molecule from MD and confirmed its anti-cancer effect in vivo. Supplementation of AM and ruminococcus further increased anti-PD1 activity.

Conclusion We isolated the bioactive polyphenol molecule from the MD berry and demonstrated that its potent adjuvant effect on anti-PD-1 was associated with a beneficial shift in microbiome and bile acid composition in a CD8+ T cell dependent manner. The modification of the gut microbiota with polyphenol supplementation provides a new therapeutic approach in immuno-oncology.

Citation Format: Meriem Messaoudene, Florent Cauchois, Reilly Piedgeon, Khoudia Diop, Corentin Richard, Thibault Varin, Jocelyn Trottier, Olivier Barbier, Geneviève Pilon, Simon Turcotte, André Marette, Bastien Castagner, Bertrand Routy. A new polyphenol prebiotic isolated from Myrciaria dubia improves gut microbiota composition and increases anti-PD-1 efficacy in murine cancer models [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5730.

Prognostic value of CD73 expression in resected colorectal cancer liver metastasis

Immune checkpoint blockade has not yet been effective in patients with mismatch repair proficient metastatic colorectal cancer. Targeting immunosuppressive metabolic pathways is being explored as a new immunotherapeutic approach. We assessed whether CD73, the rate limiting enzyme that catalyzes the degradation of extracellular AMP into immunosuppressive adenosine, could be an immunological determinant of colorectal liver metastases (CRLMs). By immunofluorescence on tissue microarrays, intratumoral CD73 expression (tCD73) was analyzed in 391 CRLMs resected in 215 patients, and soluble CD73 (sCD73) was measured by ELISA in the pre-operative serum of 193 patients. High tCD73 was associated with worse pathological features, such as multiple and larger CRLMs, and poorer pathologic response to pre-operative chemotherapy. The median time to recurrence and disease-specific survival after CRLM resection was significantly shorter in patients with high tCD73 (11.0 and 46.4 months, respectively) compared with low tCD73 (19.0 and 61.5 months, respectively). tCD73 was strongly associated with patient outcomes independently of clinicopathological variables. sCD73 did not correlate with tCD73. Patients with high levels of sCD73 also had shorter disease-specific survival. Our results suggested that CD73 in CRLMs may be prognostically informative and may help select patients more likely to respond to adenosine pathway blocking agents.

Visualization, Quantification, and Mapping of Immune Cell Populations in the Tumor Microenvironment

The immune landscape of the tumor microenvironment (TME) is a determining factor in cancer progression and response to therapy. Specifically, the density and the location of immune cells in the TME have important diagnostic and prognostic values. Multiomic profiling of the TME has exponentially increased our understanding of the numerous cellular and molecular networks regulating tumor initiation and progression. However, these techniques do not provide information about the spatial organization of cells or cell-cell interactions. Affordable, accessible, and easy to execute multiplexing techniques that allow spatial resolution of immune cells in tissue sections are needed to complement single cell-based high-throughput technologies. Here, we describe a strategy that integrates serial imaging, sequential labeling, and image alignment to generate virtual multiparameter slides of whole tissue sections. Virtual slides are subsequently analyzed in an automated fashion using user-defined protocols that enable identification, quantification, and mapping of cell populations of interest. The image analysis is done, in this case using the analysis modules Tissuealign, Author, and HISTOmap. We present an example where we applied this strategy successfully to one clinical specimen, maximizing the information that can be obtained from limited tissue samples and providing an unbiased view of the TME in the entire tissue section.

The safety and efficacy of hypovolemic phlebotomy on blood loss and transfusion in liver surgery: a systematic review and meta-analysis

BACKGROUND

Hypovolemic phlebotomy (HP) is a novel intervention that involves intraoperative removal of whole blood (7-10 mL/kg) without volume replacement. The subsequent central venous pressure (CVP) reduction is hypothesized to decrease blood loss and the need for blood transfusion. The objective was to conduct a systematic assessment of the safety and efficacy of HP on blood loss and transfusion in the liver surgery literature.

METHODS

MEDLINE, EMBASE, and Cochrane Library databases were searched. Outcomes of interest included blood loss, allogenic red blood cell transfusion, postoperative adverse events, and CVP change. A qualitative synthesis and meta-analysis were performed as appropriate.

RESULTS

Four cohort studies, one case series, and three randomized controlled trials involving 2255 patients were included. Meta-analysis of studies involving liver resections for any indication (n = 6) found no difference in transfusion (OR 0.38, p = 0.12) or incidence of adverse events with HP compared to non-use. Pooling of studies involving liver resections for an underlying pathology (n = 4) revealed HP was associated with significant reduction in transfusion (OR 0.25, p = 0.03) but no differences in blood loss (-173 mL, p = 0.17).

CONCLUSION

This review suggests HP is safe and associated with decreased transfusion in patients undergoing liver surgery. It supports further investigation.

Deep learning workflow in radiology: a primer

Interest for deep learning in radiology has increased tremendously in the past decade due to the high achievable performance for various computer vision tasks such as detection, segmentation, classification, monitoring, and prediction. This article provides step-by-step practical guidance for conducting a project that involves deep learning in radiology, from defining specifications, to deployment and scaling. Specifically, the objectives of this article are to provide an overview of clinical use cases of deep learning, describe the composition of multi-disciplinary team, and summarize current approaches to patient, data, model, and hardware selection. Key ideas will be illustrated by examples from a prototypical project on imaging of colorectal liver metastasis. This article illustrates the workflow for liver lesion detection, segmentation, classification, monitoring, and prediction of tumor recurrence and patient survival. Challenges are discussed, including ethical considerations, cohorting, data collection, anonymization, and availability of expert annotations. The practical guidance may be adapted to any project that requires automated medical image analysis.

Outcomes of elderly patients with resectable liver metastases from colorectal cancer (CRLM): Single center experience

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Background: Half of patients with colorectal cancer develop liver metastases during the course of their disease. Surgery is the only potentially curative option for CRLM if resectable. Treatment of patients over 70 years old is challenging mainly because of comorbidities and other geriatric syndromes. Thus, we intended to report our experience with elderly patients with resectable CRLM. Methods: After approval by the Institutional Review Board (IRB), all records from a prospectively collected database at Centre Hospitalier de l’Université de Monréal (CHUM) were retrospectively analyzed. Clinicopathological characteristics, surgery and chemotherapy treatment modalities were reviewed. RFS and OS in patients ≥ 70y were calculated using the Kaplan Meier survival curve. Results: From 2010 to 2016, 101 patients older than 70 years were identified. Safety and surgical complications were previously reported. Median age was 75 years. CRLM were synchronous in 46.5% and metachronous in 53.5%. Relapse free survival (RFS) of patients ≥ 70 years was 33.7 months. Overall survival (OS) of patients ≥70 years was comparable to those of less than 65 years old (median OS: 56 vs 62 months; p = 0.15, respectively). Hepatic relapse showed worse survival when compared to extra-liver recurrence, mOS: 44 vs 33.2 vs 29.3 months for non-hepatic, hepatic only and hepatic with other sites respectively (trend p = 0.034). Although non-statistically significant, Patients with metachronous CRLM had superior mOS compared to those with synchronous disease (58.7 vs 44.7 months; p = 0.22). Conclusions: Survival Outcomes of patients with an age ≥ 70 years were comparable to those of younger patients and what is reported in literature. Age should not be a limiting factor in the management of elderly patients with resectable CRLM. Hepatic metastatectomies +/- chemotherapy should be offered with curative intents.

Abstract CT225: A Phase Ib/IIa randomized pilot study to investigate the safety and tolerability of autologous T-cells with enhanced T-cell receptors specific to NY-ESO-1/LAGE-1a (GSK3377794) alone, or in combination with pembrolizumab, in advanced non-small cell lung cancer

Introduction: There is a high unmet medical need for patients with advanced non-small cell lung cancer (NSCLC) who have failed platinum-based chemotherapy and checkpoint inhibitors. Only 10% of such patients receive any benefit from current therapies, and novel therapies are needed to improve outcomes. Preclinical data support the efficacy, specificity and possible safety of NYESO1/LAGE1a T-cell receptor-engineered patient Tcells (GSK3377794) in NSCLC. Pembrolizumab (PEM) is a monoclonal antibody, which specifically blocks PD1/PDL1 interaction, thereby increasing the antitumor function of Tcells. Thus, the combination of GSK3377794 and PEM may work synergistically due to the inhibition of PD1/PD-L1 signaling on GSK3377794 and other T-cells, potentially further improving the therapeutic effect.

Methods: This is a Phase Ib/IIa randomized, multiarm, openlabel pilot study (NCT03709706) in human leukocyte antigen (HLA)A*02:01, HLAA*02:05 and/or HLAA*02:06 adult patients (aged &gt;18 years) whose tumors express NYESO1 and/or LAGE1a. This study aims to enroll up to 44 patients with unresectable Stage IIIb or Stage IV NSCLC who were either ineligible for definitive chemoradiotherapy, have recurrent disease which has progressed during or after platinumbased chemotherapy with or without anti-PD-1 agents, have terminated prior treatment due to intolerable side effects, or have refused standard approved treatment. Patients will be randomized (1:1) to two treatment arms. Arm A will receive GSK3377794 as monotherapy, administered as a single intravenous (IV) infusion; Arm B will receive GSK3377794 as a single IV infusion on Day 1 followed by PEM 200 mg initiated on Day 22 and continued for up to 35 cycles or until disease progression. Patients in Arm A who progress after receiving GSK3377794 monotherapy will be offered antiPD1 therapy at the same dose and duration as Arm B. The study will use a Bayesian adaptive design, wherein enrollment can be halted in either arm for futility. The patient journey will consist of 3 parts: patients will undergo eligibility screening (Part 1), followed by leukapheresis (Part 2), after which patients will enter the Interventional Phase (Part 3) during which patients will receive preparative lymphodepleting chemotherapy followed by infusion of GSK3377794. The first patient was screened on December 31, 2018.

ClinicalTrials.gov identifier: NCT03709706

Study is funded by GlaxoSmithKline and is in collaboration with Merck & Co., Inc.

Citation Format: Karen L. Reckamp, Wallace Akerley, Martin J. Edelman, Balazs Halmos, Kai He, Melissa Johnson, Raja Mudad, Joel W. Neal, Taofeek K. Owonikoko, Jyoti D. Patel, Sandip P. Patel, Jonathan W. Riess, Adrian G. Sacher, Simon Turcotte, Liza C. Villaruz, Marjorie G. Zauderer, Benedetto Farsaci, Aisha Hasan, Roma Patel, Yuehui Wu, Michael Chisamore, Vincent Lam. A Phase Ib/IIa randomized pilot study to investigate the safety and tolerability of autologous T-cells with enhanced T-cell receptors specific to NY-ESO-1/LAGE-1a (GSK3377794) alone, or in combination with pembrolizumab, in advanced non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT225.

Dynamic contrast-enhanced MRI to assess hepatocellular carcinoma response to Transarterial chemoembolization using LI-RADS criteria: A pilot study

PURPOSE

To identify quantitative dynamic contrast-enhanced (DCE)-MRI perfusion parameters indicating tumor response of hepatocellular carcinoma (HCC) to transarterial chemoembolization (TACE).

MATERIALS AND METHODS

This prospective pilot study was approved by our institutional review board; written and informed consent was obtained for each participant. Patients underwent DCE-MRI examinations before and after TACE. A variable flip-angle unenhanced 3D mDixon sequence was performed for T1 mapping. A dynamic 4D mDixon sequence was performed after contrast injection for assessing dynamic signal enhancement. Nonparametric analysis was conducted on the time-intensity curves. Parametric analysis was performed on the time-concentration curves using a dual-input single-compartment model. Treatment response according to Liver Reporting and Data System (LI-RADS) v2018 was used as the reference standard. The comparisons within groups (before vs. after treatment) and between groups (nonviable vs. equivocal or viable tumor) were performed using nonparametric bootstrap taking into account the clustering effect of lesions in patients.

RESULTS

Twenty-eight patients with 52 HCCs (size: 10-104 mm) were evaluated. For nonviable tumors (n = 27), time to peak increased from 62.5 ± 18.2 s before to 83.3 ± 12.8 s after treatment (P< 0.01). For equivocal or viable tumors (n = 25), time to peak and mean transit time significantly increased (from 54.4 ± 24.1 s to 69.5 ± 18.9 s, P < 0.01 and from 14.2 ± 11.8 s to 33.9 ± 36.8 s, P= 0.01, respectively) and the transfer constant from the extracellular and extravascular space to the central vein significantly decreased from 14.8 ± 14.1 to 8.1 ± 9.1 s^-1 after treatment (P= 0.01).

CONCLUSION

This prospective pilot DCE-MRI study showed that time to peak significantly changed after TACE treatment for both groups (nonviable tumors and equivocal or viable tumors). In our cohort, several perfusion parameters may provide an objective marker for differentiation of treatment response after TACE in HCC patients.

Role of neoadjuvant therapy (NAT) in pancreatic adenocarcinoma (PAC): A single center experience

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Background: Surgical resection of PAC followed by adjuvant therapy is the standard of care for non-metastatic resectable tumors. Surgical resection with clear margins of borderline (BR) or locally advanced (LA) tumors is either challenging or impossible. Furthermore, there are no clear recommendations concerning NAT for non-upfront resectable PAC. Thus we reviewed our own experience with different NAT modalities for BR and LA PAC. Methods: Medical records of patients identified by Tumor Board as BR or LA PAC and treated with NAT at Centre Hospitalier de l’Université de Montréal (CHUM) were retrospectively reviewed. Survival curves were estimated by the Kaplan-Meier method and compared with the Log-rank test. For both univariate and subgroup analyses, hazard ratio and 95% confidence interval were estimated by Cox proportional hazard regression. Results: Between 2009 and 2017, 90 patients (50 BR, 40 LA) were identified. Chemotherapy, mostly FOLFIRINOX, was the only NAT in 51 patients (56.6%), 23 patients (25.3%) received chemoradiotherapy alone and 16 patients (17.7%) received sequential treatment of both modalities. Tumor resection was achieved in 44 patients, with 32 BR patients (R0: 68.7%) and 12 LA patients (R0: 75%). Median Disease free survival (DFS) of patients that underwent resection was 12.3 months. mPFS was 29 vs 10 months (HR:0.2; p < 0.001) and mOS was 41.7 vs 15.7 months (HR:0.3; p < 0.001) in resected and non-resected patients, respectively. In subgroup analysis, resection statistically improved PFS and OS regardless of age, sex, T stage and type of vessel involvement. Treatment with more than one modality showed better clinical outcomes (PFS and OS) and a non-statistically higher R0 resection rate that was 100% in BR tumors. OS in patients with resected cancers was not reached for the multimodality group, 41.7 months for chemotherapy alone group and 22.4 months in patients treated with chemoradiotherapy group (p = 0.017). Conclusions: In this retrospective single center analysis, NAT with chemotherapy and/or chemoradiotherapy appears to improve patients’ clinical resection results and outcomes. These results validate previous retrospective studies but warrant large prospective trials to define the best NAT.

Deep Learning for Automated Segmentation of Liver Lesions at CT in Patients with Colorectal Cancer Liver Metastases

Purpose

To evaluate the performance, agreement, and efficiency of a fully convolutional network (FCN) for liver lesion detection and segmentation at CT examinations in patients with colorectal liver metastases (CLMs).

Materials and Methods

This retrospective study evaluated an automated method using an FCN that was trained, validated, and tested with 115, 15, and 26 contrast material-enhanced CT examinations containing 261, 22, and 105 lesions, respectively. Manual detection and segmentation by a radiologist was the reference standard. Performance of fully automated and user-corrected segmentations was compared with that of manual segmentations. The interuser agreement and interaction time of manual and user-corrected segmentations were assessed. Analyses included sensitivity and positive predictive value of detection, segmentation accuracy, Cohen κ, Bland-Altman analyses, and analysis of variance.

Results

In the test cohort, for lesion size smaller than 10 mm (n = 30), 10-20 mm (n = 35), and larger than 20 mm (n = 40), the detection sensitivity of the automated method was 10%, 71%, and 85%; positive predictive value was 25%, 83%, and 94%; Dice similarity coefficient was 0.14, 0.53, and 0.68; maximum symmetric surface distance was 5.2, 6.0, and 10.4 mm; and average symmetric surface distance was 2.7, 1.7, and 2.8 mm, respectively. For manual and user-corrected segmentation, κ values were 0.42 (95% confidence interval: 0.24, 0.63) and 0.52 (95% confidence interval: 0.36, 0.72); normalized interreader agreement for lesion volume was -0.10 ± 0.07 (95% confidence interval) and -0.10 ± 0.08; and mean interaction time was 7.7 minutes ± 2.4 (standard deviation) and 4.8 minutes ± 2.1 (P < .001), respectively.

Conclusion

Automated detection and segmentation of CLM by using deep learning with convolutional neural networks, when manually corrected, improved efficiency but did not substantially change agreement on volumetric measurements.© RSNA, 2019Supplemental material is available for this article.

LI-RADS for CT diagnosis of hepatocellular carcinoma: performance of major and ancillary features

PURPOSE

To evaluate the diagnostic performance of Liver Imaging Reporting and Data System (LI-RADS) v2017 major features, the impact of ancillary features, and categories on contrast-enhanced computed tomography (CECT) for the diagnosis of hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

This retrospective study included 59 patients (104 observations including 72 HCCs) with clinical suspicion of HCC undergoing CECT between 2013 and 2016. Two radiologists independently assessed major and ancillary imaging features for each liver observation and assigned a LI-RADS category based on major features only and in combination with ancillary features. The composite reference standard included pathology or imaging. Per-lesion estimates of diagnostic performance of major features, ancillary features, and LI-RADS categories were assessed by generalized estimating equation models.

RESULTS

Major features (arterial phase hyperenhancement, washout, capsule, and threshold growth) respectively had a sensitivity of 86.1%, 81.6%, 20.7%, and 26.1% and specificity of 39.3%, 67.9%, 89.9%, and 85.0% for HCC. Ancillary features (ultrasound visibility as discrete nodule, subthreshold growth, and fat in mass more than adjacent liver) respectively had a sensitivity of 42.6%, 50.8%, and 15.1% and a specificity of 79.2%, 66.9%, and 96.4% for HCC. Ancillary features modified the final category in 4 of 104 observations. For HCC diagnosis, categories LR-3, LR-4, LR-5, and LR-TIV (tumor in vein) had a sensitivity of 5.3%, 29.0%, 53.7%, and 10.7%; and a specificity of 49.1%, 84.4%, 97.3%, and 96.4%, respectively.

CONCLUSION

On CT, LR-5 category has near-perfect specificity for the diagnosis of HCC and ancillary features modifies the final category in few observations.

Portal vein embolization does not affect the long-term survival and risk of cancer recurrence among colorectal liver metastases patients: A prospective cohort study

BACKGROUND

Previous studies comparing the survival outcomes of liver resections with and without preoperative portal vein embolization (PVE) for colorectal liver metastases (CLM) have linked PVE to higher rate of tumor progression, lower overall survival (OS) and lower disease-free survival (DFS). The lack of adjusted models to compare these outcomes is a limitation of these studies since patients requiring PVE may differ significantly from the ones receiving upfront surgery.

MATERIALS AND METHODS

Prospective cohort study of 128 patients undergoing CLM resection. The OS analysis followed an intent-to-treat (ITT) approach. The adjusted impact of PVE on OS and DFS was evaluated using multivariate Cox regression models.

RESULTS

Seventy-one patients underwent PVE before attempting a liver resection while 57 received upfront surgery (NoPVE). All NoPVE patients were resected while 14 PVE participants (19.7%) were not operated (tumor progression = 9/14). PVE patients had a significantly higher preoperative lesions count (3 [1.75-4] vs 1 [1-2.5]; p < 0.001), a higher prevalence of bilateral metastases (23.5% vs 8.8, p = 0.028) and a higher count of neo-adjuvant chemotherapy cycles compared to NoPVE patients. The OS of PVE patients was similar to NoPVE participants (44.7 months [26.9-69.5] vs 49.0 [24.9-64.8], p = 0.761). The DFS of resected PVE patients was higher than NoPVE patients (33.2 months [10.7-54.6] vs 23.4 months [14.1-58.1], p = 0.991). In the adjusted models, preoperative lesions count was the only significant predictor of overall mortality (HR+IC₉₅ = 1.06 (1.02-1.11) p = 0.005) and cancer recurrence (HR+IC₉₅ = 1.14 (1.03-1.27) p = 0.012).

CONCLUSION

In the context of CLM, patients requiring PVE differ significantly from patients receiving upfront surgery. This confirms the need for adjusted models when comparing the clinical outcomes of both groups. Our adjusted analysis suggests that PVE is not a significant predictor of a lower OS or DFS. PVE allowed the resection of 80% of participants with initially unresectable CLM.

INSTITUTIONAL PROTOCOL NUMBER

12.106 STUDY REGISTRATION NUMBER: NCT03168230.

Abstract 4670: Evidence of neoantigen-reactive T cell response in a case of relapsing, mismatch-repair gene proficient, colorectal cancer

Whether the endogenous T cell reactivity to antigens derived from cancer mutations, called neoantigens (neoAgs), can be exploited for immunotherapy in patients with mismatch-repair (MMR) gene proficient metastatic colorectal cancer (CRC) is largely unknown. Here, we investigated the frequency of neoAg-reactive T cells longitudinally in a patient with relapsing CRC. Using whole exome and RNA sequencing, we identified 96 single nucleotide variant (SNV), 8 frameshift and 29 insertion/deletion mutations in a liver metastasis. Co-culture assays between in vitro expanded tumor infiltrating T lymphocytes (TILs) and autologous CD40-activated B cells loaded with peptides derived from SNVs led to the identification of two CD8+ T cell clones specific for PAMA733E, and respectively 1, 4 and 2 CD4+ T cell clones specific for PABPC1G563S, PDE4DIPR685S and TRPM4A480V. T cell clonality was confirmed by TCR Sanger sequencing. We assessed the in vivo frequency of these neoAg-reactive T cell clones by TCRβ chain deep sequencing (Adaptive Biotechnologies). The dominant T cell clone, reactive to PAMA733E, represented 5.2% of TILs in the primary tumor resected in 2010, 2.2% of TILs in the colonic recurrence resected in 2011, and 3.2% of TILs in the liver metastasis resected in 2012. The neoAg-reactive T cells were also detected in the peritumoral liver, but not into the distant normal liver. Along the disease course, most reactive T cell clones were not detected in the tumor draining lymph nodes or in the peripheral blood, at an average detection capacity of 1/3680 and 1/185,495 T cells respectively. When compared to the RNAseq data from 60 other CRC liver metastases, the relatively high level of transcripts related to immune cells, antigen processing and presentation, IFN-γ responsive genes, T-cell inhibitory and stimulatory receptors, cytokines, and chemokines observed in our patient metastasis suggested that there was an ongoing spontaneous immune response intratumoraly, co-existing with many immune-suppressive molecules. Our results support that neoAg-reactive T cells can be found in non-highly mutated, MMR proficient CRC tumors, at a much higher frequency than in the peripheral blood or the draining lymph nodes. As an adjuvant strategy to prevent recurrence, it may be possible in some patients to boost the immune response against a relevant neoAg expressed in the primary tumor. At the metastatic stage, a broader array of neoAgs may be targetable.

Citation Format: Mélissa Mathieu, Alexandre Paradis, Sandy Pelletier, Steven Hébert, Kevin Boutin, Éric Audemard, Sylvie Mader, Claudia Kleinman, Simon Turcotte. Evidence of neoantigen-reactive T cell response in a case of relapsing, mismatch-repair gene proficient, colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4670.

Deep Learning: A Primer for Radiologists

Deep learning is a class of machine learning methods that are gaining success and attracting interest in many domains, including computer vision, speech recognition, natural language processing, and playing games. Deep learning methods produce a mapping from raw inputs to desired outputs (eg, image classes). Unlike traditional machine learning methods, which require hand-engineered feature extraction from inputs, deep learning methods learn these features directly from data. With the advent of large datasets and increased computing power, these methods can produce models with exceptional performance. These models are multilayer artificial neural networks, loosely inspired by biologic neural systems. Weighted connections between nodes (neurons) in the network are iteratively adjusted based on example pairs of inputs and target outputs by back-propagating a corrective error signal through the network. For computer vision tasks, convolutional neural networks (CNNs) have proven to be effective. Recently, several clinical applications of CNNs have been proposed and studied in radiology for classification, detection, and segmentation tasks. This article reviews the key concepts of deep learning for clinical radiologists, discusses technical requirements, describes emerging applications in clinical radiology, and outlines limitations and future directions in this field. Radiologists should become familiar with the principles and potential applications of deep learning in medical imaging. ^©RSNA, 2017.

LI-RADS for MR Imaging Diagnosis of Hepatocellular Carcinoma: Performance of Major and Ancillary Features

Purpose To evaluate the performance of major features, ancillary features, and categories of Liver Imaging Reporting and Data System (LI-RADS) version 2014 at magnetic resonance (MR) imaging for the diagnosis of hepatocellular carcinoma (HCC). Materials and Methods This retrospective institutional review board-approved study included patients with liver MR imaging and at least one pathologically proved lesion. Between 2004 and 2016, 102 patients (275 observations including 113 HCCs) met inclusion criteria. Two radiologists independently assessed major and ancillary imaging features for each liver observation and assigned a LI-RADS category. Per-lesion estimates of diagnostic performance of major features, ancillary features, and LI-RADS categories were assessed by using generalized estimating equation models. Results Major features (arterial phase hyperenhancement, washout, capsule, and threshold growth) had a sensitivity of 88.5%, 60.6%, 32.9%, and 41.6%, and a specificity of 18.6%, 84.8%, 98.8%, and 83.2% for HCC, respectively. Ancillary features (mild-moderate T2 hyperintensity, restricted diffusion, mosaic architecture, intralesional fat, lesional fat sparing, blood products, and subthreshold growth) had a sensitivity of 62.2%, 54.8%, 9.9%, 30.9%, 23.1%, 2.8%, and 48.3%, and a specificity of 79.4%, 90.6%, 99.4%, 94.2%, 83.1%, 99.3%, and 91.4% for HCC, respectively. The LR-5 or LR-5 V categories had a per-lesion sensitivity of 50.8% and a specificity of 95.8% for HCC, respectively. The LR-4, LR-5, or LR-5 V categories (determined by using major features only vs combination of major and ancillary features) had a per-lesion sensitivity of 75.9% and 87.9% and a per-lesion specificity of 87.5% and 86.2%, respectively. Conclusion The use of ancillary features in combination with major features increases the sensitivity while preserving a high specificity for the diagnosis of HCC.

Prediction of Hepatocellular Carcinoma Recurrence Beyond Milan Criteria After Resection: Validation of a Clinical Risk Score in an International Cohort

OBJECTIVE

This study aims to validate a previously reported recurrence clinical risk score (CRS).

SUMMARY OF BACKGROUND DATA

Salvage transplantation after hepatocellular carcinoma (HCC) resection is limited to patients who recur within Milan criteria (MC). Predicting recurrence patterns may guide treatment recommendations.

METHODS

An international, multicenter cohort of R0 resected HCC patients were categorized by MC status at presentation. CRS was calculated by assigning 1 point each for initial disease beyond MC, multinodularity, and microvascular invasion. Recurrence incidences were estimated using competing risks methodology, and conditional recurrence probabilities were estimated using the Bayes theorem.

RESULTS

From 1992 to 2015, 1023 patients were identified, of whom 613 (60%) recurred at a median follow-up of 50 months. CRS was well validated in that all 3 factors remained independent predictors of recurrence beyond MC (hazard ratio 1.5-2.1, all P < 0.001) and accurately stratified recurrence risk beyond MC, ranging from 19% (CRS 0) to 67% (CRS 3) at 5 years. Among patients with CRS 0, no other factors were significantly associated with recurrence beyond MC. The majority recurred within 2 years. After 2 years of recurrence-free survival, the cumulative risk of recurrence beyond MC within the next 5 years for all patients was 14%. This risk was 12% for patients with initial disease within MC and 17% for patients with initial disease beyond MC.

CONCLUSIONS

CRS accurately predicted HCC recurrence beyond MC in this international validation. Although the risk of recurrence beyond MC decreased over time, it never reached zero.

Abstract 2795: Integrating multiomics discovery approaches to identify biomarkers of therapeutic resistance in metastatic colorectal cancer through analyses of multiple sequential tumor and liquid biopsies; Qcroc01: NCT00984048

Colorectal cancer (CRC) is the 2nd leading cause of cancer related-death in Canada. Clinical responses of metastatic (m)CRC to first-line treatment range from 35 to 60%, but even responders inevitably develop therapeutic resistance. Studies aiming at understanding mechanisms of resistance have largely investigated primary tumors. However, selective pressures during therapy can lead to the expansion of resistant clones and tumor heterogeneity. This highlights the need to characterize the molecular changes of metastasis and plasma over time of treatment and response to decipher tumor evolution and therapeutic resistance mechanisms.

In this multicenter study, 52 tissue samples from liver metastasis were collected at baseline (pre-biopsies) and at the time of resistance (post-biopsies) in responder and non-responder mCRC patients (n=44) undergoing the same standard first-line treatments. Multiple post-biopsies also have been harvested in 4 patients, to allow the assessment of tumor heterogeneity and as well as the evolution of the genomic complexity after treatment exposure.

Analyses were carried out across multiple omic platforms to identify resistant signatures and characterize molecular changes during treatment. Biopsies were profiled using exome and transcriptome sequencing as well as high-density SNP array analysis to capture chromosomal anomalies, loss of heterozygosity (LOH) and copy number variations (CNV). Additionally, serial blood samples were collected for proteomic, ctDNA and cytokine analysis.

Our preliminary analysis of transcriptomes performed on serial biopsies from a set of 11 patients identified genes consistently overexpressed at resistance. Cytogenetics analysis showed similar genomic profiles of matched pre- and post-biopsies and allowed the establishment of LOH and CNV catalogues of liver metastasis, while exome sequencing revealed cumulative somatic mutations over time of treatment, which suggests subclonal and acquired “driver” mutations of resistance. Plasma-derived ctDNA analysis was performed to investigate the mutational status during treatment and whether they correlate with their relative levels in biopsies. Immune gene expression analysis of a test set of 27 metastases revealed strong clustering of 7 metastases due to overexpression of transcripts related to active immune response, allowing to define novel subgroups of patients based on immune response status. Our study, using a multi-omic strategy and integration of independent molecular platforms to profile liver metastasis samples of responder and non-responder mCRC patients, constitutes an innovative approach to identify clinical biomarkers and molecular signature of resistance, which may enhance individualization of cancer medicine and customized therapy.

Citation Format: Karen Gambaro, Maud Marques, Ryan Morin, Claudia Kleinman, Michael Witcher, Simon Turcotte, Benoit Samson, Bernard Lespérance, Yoo-Joung Ko, Richard Dalfen, Eve St-Hilaire, Lucas Sideris, Felix Couture, Sabine Tejpar, Ronald Burkes, Mohammed Harb, Francine Aubin, Thierry Alcindor, Errol Camlioglu, Adriana Aguilar, Mathilde Couetoux du Tertre1, Suzan McNamara, Adrian Gologan, Petr Kavan, Gerald Batist. Integrating multiomics discovery approaches to identify biomarkers of therapeutic resistance in metastatic colorectal cancer through analyses of multiple sequential tumor and liquid biopsies; Qcroc01: NCT00984048 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2795. doi:10.1158/1538-7445.AM2017-2795

Tumor-Associated Macrophage Infiltration in Colorectal Cancer Liver Metastases is Associated With Better Outcome

BACKGROUND

Tumor-associated macrophages (TAMs) support growth in most human cancers, with the notable exception of colorectal adenocarcinoma, in which TAM infiltration of primary tumors is correlated with a better outcome. The importance of TAMs in colorectal liver metastases (CLM) is unknown.

METHODS

Using a tissue microarray of CLM resected at their institution from 1998 to 2000, the authors quantified immune marker expression by immunohistochemistry (IHC) using Metamorph Image Analysis software. Findings showed that CD68, CD3, CD4, CD8, FoxP3, and MHC-I were correlated with overall survival (OS) and disease-free survival (DFS).

RESULTS

Tumor cores from 158 patients were analyzed. The median follow-up period was 117 months for survivors (n = 39). The univariate analysis showed a significant positive association between DFS and CD4⁺ (p = 0.025) and CD68⁺ (p = 0.007). The findings showed a significant positive correlation of OS with CD4⁺ (p = 0.042), whereas the correlation with CD68⁺ was not significant (p = 0.17). Cutoffs were determined to dichotimize each marker for the highest log-rank statistic. Patients with CD4^high had a median OS of 115 months and DFS of 41 months (p = 0.007 compared with 40 and 16 months, respectively, for patients with CD4^low (p = 0.022). Patients with CD68^high had a median OS of 50 months and a median DFS of 25 months (p = 0.67) compared with 43 and 15 months (p = 0.028). In the multivariate analysis of factors affecting DFS, high CD68 was associated with longer DFS (hazard ratio [HR], 0.63, 95% confidence interval [CI], 0.43-0.94; p = 0.02), independently of clinicopathologic variables and CD4.

CONCLUSIONS

High TAM infiltration in resected CLM is associated with better outcome, independently of known clinicopathologic and immune predictors. This suggests that TAM depletion, which is being tested clinically in other cancers, may be detrimental in CLM.

A Validated Prognostic Multigene Expression Assay for Overall Survival in Resected Colorectal Cancer Liver Metastases

PURPOSE

Risk stratification after surgery for colorectal cancer liver metastases (CRLM) is achieved using clinicopathologic variables, however, is of limited accuracy. We sought to derive and externally validate a multigene expression assay prognostic of overall survival (OS) that is superior to clinicopathologic variables in patients with surgically resected CRLM.

EXPERIMENTAL DESIGN

We measured mRNA expression in prospectively collected frozen tumor from 96 patients with surgically resected CRLM at Memorial Sloan Kettering Cancer Center (MSKCC, New York, NY). We retrospectively generated a 20-gene molecular risk score (MRS) and compared its prognostic utility for OS and recurrence-free survival (RFS) with three common clinical risk scores (CRS). We then tested the prognostic ability of the MRS in an external validation cohort (European) of 119 patients with surgically resected CRLM at the University Medical Center Utrecht (Utrecht, the Netherlands) and Paul Brousse Hospital (Villejuif, France).

RESULTS

For OS in the MSKCC cohort, MRS was the strongest independent prognosticator (HR, 3.7-4.9; P < 0.001) followed by adjuvant chemotherapy (HR, 0.3; P ≤ 0.001). For OS in the European cohort, MRS was the only independent prognosticator (HR, 3.5; P = 0.007). For RFS, MRS was also independently prognostic in the MSKCC cohort (HR, 2.4-2.6; P ≤ 0.001) and the European cohort (HR, 1.6-2.5; P ≤ 0.05).

CONCLUSIONS

Compared with CRSs, the MRS is more accurate, broadly applicable, and an independent prognostic biomarker of OS in resected CRLM. This MRS is the first externally validated prognostic multigene expression assay after metastasectomy for CRLM and warrants prospective validation. Clin Cancer Res; 22(10); 2575-82. ©2016 AACR.

Abstract B074: Tumor-reactive CD4+ T cells in metastatic gastrointestinal cancer refractory to chemotherapy

Purpose: To evaluate whether patients with metastatic gastrointestinal adenocarcinomas refractory to chemotherapy harbor tumor-reactive CD4+ T cells.

Experimental Design: Expansion of CD4+ tumor-infiltrating lymphocytes (TIL) and cancer cell lines was performed from gastrointestinal cancer metastases in 5 patients for the study of antitumor immune recognition. Retroviral transduction of genes encoding the class II, major histocompatibility complex, transactivator (CIITA) was used to induce the expression of major histocompatibility complex (MHC) class II in tumor cell lines. Recognition of autologous tumor cell lines by TIL was evaluated by up-regulation of 4-1BB and OX40 by flow cytometry, and/or secretion of IFNg by ELISA.

Results: TIL were expanded from metastases, and new tumor cell lines were generated in 5 patients. Retroviral transduction of CIITA in tumor cell lines effectively induced expression of MHC class II in &gt;80% of cells. Autologous tumor recognition was found in CD4+ TIL from 2 of these 5 patients. In a patient with gastric cancer liver metastases, tumor-reactive CD4+OX40+ TIL were cell-sorted from a TIL cell line. These cells up-regulated OX40 in the presence of all 4 autologous cancer cell lines albeit at different levels, but they did not produce IFNg. This recognition was specifically abolished by pan-MHC class II blocking antibodies. CD4+ TIL clones have been isolated and are being further characterised. Interestingly, tumor-reactive CD8+ TIL were previously identified and characterized in this patient. In a second patient with colon cancer abdominal wall metastases, tumor-reactive CD4+OX40+ TIL were cell-sorted from a TIL cell line. These cells were reactive to all 4 autologous cancer cell lines as they up-regulated OX40 and secreted IFNg. Recognition was blocked by anti-HLA-DR blocking antibodies. CD4+ TIL clones have been isolated and are being further characterized. In the near future, we expect to identify the TCR and HLA restriction element for both patients. We will also determine if CD4+ TIL clones have cross-reactivity against allogeneic HLA-matched gastrointestinal tumor cell lines.

Conclusions: This study provides a basis for the development of immunotherapy for patients with advanced gastrointestinal malignancies by first establishing the presence of naturally occurring tumor-reactive CD4+ TIL at the molecular level.

Citation Format: Sandy Pelletier, Simon Turcotte. Tumor-reactive CD4+ T cells in metastatic gastrointestinal cancer refractory to chemotherapy. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr B074.

Abstract A084: Identification of mutation-reactive T cells in patients with gastrointestinal cancers

New immunotherapeutic advances for common epithelial cancers relies on our ability to stimulate T lymphocytes against specific tumour antigens (Ag). Next-generation sequencing now allows rapid identification of somatic cancer mutations that can lead to the expression of mutated Ag. We hypothesize that gastrointestinal cancer metastases are infiltrated by T cells recognizing tumour mutated Ag. Our aim is to set up an experimental platform to screen for and study the frequency and function of mutation-reactive T cells, while characterizing novel tumour mutated Ag.

To do this, we used two cancer cell lines generated from a liver metastasis of a gastric cancer patient. The cell line A was recognized by an autologous CD8+ T cell clone infiltrating the patient's metastasis, restricted by HLA C*0701, while cell line B was not recognized by the same clone despite its expression of the HLA C*0701. The CD8+ T cell clone was not reactive to a large panel of HLA-C*0701 expressing gastrointestinal cancer cell lines, reinforcing the hypothesis that the Ag recognized was unique to the autologous gastric cancer cell line. Exome and transcriptome sequencing was performed to compare the mutated genes differentially expressed by cancer cell line A and B. A total of 27 mutated Ag were selected as candidates: 26 Ag only expressed by cell line A, and one Ag overexpressed by cell line A. To screen for reactivity of the CD8+ T cell clone to mutated Ag, 25 amino acid (aa) mini-genes containing the mutation flanked upstream and downstream by normal aa were synthesised and cloned in tandem into 3 expression plasmids. A control sequence from the MAGE-A12 gene containing an epitope restricted by HLA-C*0701was included in each tandem minigene (TMG) construct. The mRNA from these 3 TMG constructs were in vitro transcribed and electroporated into CD40-activated B cells expressing HLA C*0701, used as antigen presenting cells. Co-culture assays are ongoing, using the CD8+ T cell clones as effectors and T cells transduced with a MAGE-A12-specific TCR as control. For the detection of mutation-reactive T cells, the sensitivity of TMG expression is compared to pulsing mutated peptides on B cells.

Taking advantage of the differential recognition of two cancer cell lines by an autologous CD8+ T cell clone, we have established a bioinformatics approach based on next-generation sequencing to obtain a list of candidate mutated Ag and we have designed an experimental system to assess their recognition by T cells. This platform will allow us to study the function of T cells reactive against metastatic gastrointestinal cancers and should lead to the discovery of new tumour Ag. Gaining a better understanding of T cells reactive to gastrointestinal cancers should ultimately contribute to the development of immunotherapies for these common malignancies.

Citation Format: Mélissa Mathieu, Sandy Pelletier, David Laperrière, Sylvie Mader, Simon Turcotte. Identification of mutation-reactive T cells in patients with gastrointestinal cancers. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr A084.

Immunogenicity of somatic mutations in human gastrointestinal cancers

It is unknown whether the human immune system frequently mounts a T cell response against mutations expressed by common epithelial cancers. Using a next-generation sequencing approach combined with high-throughput immunologic screening, we demonstrated that tumor-infiltrating lymphocytes (TILs) from 9 out of 10 patients with metastatic gastrointestinal cancers contained CD4(+) and/or CD8(+) T cells that recognized one to three neo-epitopes derived from somatic mutations expressed by the patient's own tumor. There were no immunogenic epitopes shared between these patients. However, we identified in one patient a human leukocyte antigen-C*08:02-restricted T cell receptor from CD8(+) TILs that targeted the KRAS(G12D) hotspot driver mutation found in many human cancers. Thus, a high frequency of patients with common gastrointestinal cancers harbor immunogenic mutations that can potentially be exploited for the development of highly personalized immunotherapies.