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Multiplex immunophenotyping technologies are indispensable for a deeper understanding of biological systems. Until recently, high-dimensional cellular analyses implied the loss of tissue context as they were mostly performed in single-cell suspensions. The advent of imaging mass cytometry introduced the possibility to simultaneously detect a multitude of cellular markers in tissue sections. This technique can be applied to various tissue sources including snap-frozen and formalin-fixed, paraffin-embedded (FFPE) tissues. However, a number of methodological challenges must be overcome when developing large antibody panels in order to preserve signal intensity and specificity of antigen detection. We report the development of a 40-marker panel for imaging mass cytometry on FFPE tissues with a particular focus on the study of cancer immune microenvironments. It comprises a variety of immune cell markers including lineage and activation markers as well as surrogates of cancer cell states and tissue-specific markers (e.g., stroma, epithelium, vessels) for cellular contextualization within the tissue. Importantly, we developed an optimized workflow for maximum antibody performance by separating antibodies into two distinct incubation steps, at different temperatures and incubation times, shown to significantly improve immunodetection. Furthermore, we provide insight into the antibody validation process and discuss why some antibodies and/or cellular markers are not compatible with the technique. This work is aimed at supporting the implementation of imaging mass cytometry in other laboratories by describing methodological procedures in detail. Furthermore, the panel described here is an excellent immune monitoring tool that can be readily applied in the context of cancer research.

BackgroundEndoscopic intermuscular dissection (EID) is a promising new technique for managing rectal deep submucosal invasive cancer (D-SMIC), but long-term outcome data are currently lacking.ObjectiveThis multicentre study evaluated the three-year oncological outcomes of EID, focusing specifically on patients with rectal D-SMIC who underwent active surveillance following the procedure.DesignData from consecutive, prospectively recorded EID procedures for suspected rectal D-SMIC—based on optical diagnosis—performed at two academic centres between 2019 and 2023 were analysed. D-SMIC was defined as submucosal invasion of sm2–sm3 depth. Histological risk factors included poorly differentiated tumours (G3), lymphovascular invasion, high-grade tumour budding and positive or indeterminate resection margins (R1/Rx). Study outcomes included three-year rates of locoregional recurrence (intramural and nodal), distant recurrence (metastatic disease), non-salvageable recurrence, cancer-specific mortality and secondary rectal surgery. Cumulative incidence was estimated using the Aalen-Johansen method.ResultsAmong the 188 included cases, EID achieved an en bloc resection rate of 94.1% and R0 resection rate of 82.5%, respectively. Of the 177 procedures that were completed, 16% showed non-invasive histology (low-grade dysplasia/high-grade dysplasia; 20/177=11%) or superficial submucosal invasive cancer (sm1, 9/177=5%), and 31% (54/177) showed deeper (≥pT2) invasion. The remaining 94 D-SMIC cases (53%) represented the main target group. Of these, 37% (n=35) were classified as low risk (no histological risk factors), 34% (n=32) as intermediate risk (one risk factor) and 29% (n=27) as high risk (≥2 risk factors). Active surveillance was initiated in all low-risk patients, in 72% of the intermediate-risk cases and in 22% of the high-risk group. The remaining patients underwent completion surgery or adjuvant chemoradiotherapy. At three years, locoregional recurrence occurred in 7% (1/35, 95% CI 1% to 28%) of low-risk and 13% (2/15, 95% CI 2% to 35%) of intermediate-risk patients managed with active surveillance. All were successfully salvaged. Among the six high-risk patients under surveillance, locoregional recurrence was seen in two. No distant recurrences or cancer-specific deaths occurred in any D-SMIC group. Secondary rectal surgery was finally performed in 5.3%, 25.0% and 59.6% of the low, intermediate and high-risk groups, respectively.ConclusionDespite the challenges associated with accurate preoperative staging, EID followed by active surveillance may offer a viable alternative to radical surgery for patients with low- and intermediate-risk rectal D-SMIC, avoiding rectal surgery in most cases while maintaining oncological safety.

ObjectiveA comprehensive understanding of anticancer immune responses is paramount for the optimal application and development of cancer immunotherapies. We unravelled local and systemic immune profiles in patients with colorectal cancer (CRC) by high-dimensional analysis to provide an unbiased characterisation of the immune contexture of CRC.DesignThirty-six immune cell markers were simultaneously assessed at the single-cell level by mass cytometry in 35 CRC tissues, 26 tumour-associated lymph nodes, 17 colorectal healthy mucosa and 19 peripheral blood samples from 31 patients with CRC. Additionally, functional, transcriptional and spatial analyses of tumour-infiltrating lymphocytes were performed by flow cytometry, single-cell RNA-sequencing and multispectral immunofluorescence.ResultsWe discovered that a previously unappreciated innate lymphocyte population (Lin–CD7+CD127–CD56+CD45RO+) was enriched in CRC tissues and displayed cytotoxic activity. This subset demonstrated a tissue-resident (CD103+CD69+) phenotype and was most abundant in immunogenic mismatch repair (MMR)-deficient CRCs. Their presence in tumours was correlated with the infiltration of tumour-resident cytotoxic, helper and γδ T cells with highly similar activated (HLA-DR+CD38+PD-1+) phenotypes. Remarkably, activated γδ T cells were almost exclusively found in MMR-deficient cancers. Non-activated counterparts of tumour-resident cytotoxic and γδ T cells were present in CRC and healthy mucosa tissues, but not in lymph nodes, with the exception of tumour-positive lymph nodes.ConclusionThis work provides a blueprint for the understanding of the heterogeneous and intricate immune landscape of CRC, including the identification of previously unappreciated immune cell subsets. The concomitant presence of tumour-resident innate and adaptive immune cell populations suggests a multitargeted exploitation of their antitumour properties in a therapeutic setting.

AimsPrevious estimates of the prevalence of mismatch repair (MMR) deficiency and Lynch syndrome in small bowel cancer have varied widely. The aim of this study was to establish the prevalence of MMR deficiency and Lynch syndrome in a large group of small bowel adenocarcinomas.MethodsTo this end, a total of 400 small bowel adenocarcinomas (332 resections, 68 biopsies) were collected through the Dutch nationwide registry of histopathology and cytopathology (Pathologisch-Anatomisch Landelijk Geautomatiseerd Archief (PALGA)). No preselection criteria, such as family history, were applied, thus avoiding (ascertainment) bias. MMR deficiency status was determined by immunohistochemical staining of MMR proteins, supplemented by MLH1 promoter hypermethylation analysis and next generation sequencing of the MMR genes.ResultsMMR deficiency was observed in 22.3% of resected and 4.4% of biopsied small bowel carcinomas. Prevalence of Lynch syndrome was 6.2% in resections and 0.0% in biopsy samples. Patients with Lynch syndrome-associated small bowel cancer were significantly younger at the time of diagnosis than patients with MMR-proficient and sporadic MMR-deficient cancers (mean age of 54.6 years vs 66.6 years and 68.8 years, respectively, p<0.000).ConclusionsThe prevalence of MMR deficiency and Lynch syndrome in resected small bowel adenocarcinomas is at least comparable to prevalence in colorectal cancers, a finding relevant both for treatment (immunotherapy) and family management. We recommend that all small bowel adenocarcinomas should be screened for MMR deficiency.

The increase incidence of early colorectal cancer (T1 CRC) last years is mainly due to the introduction of population-based screening for CRC. T1 CRC staging based on histological criteria remains challenging and there is high variability among pathologists in the scoring of these criteria. It is crucial to unravel the biology behind the progression of adenoma into T1 CRC. Glycomic studies have reported extensively on alterations of the N-glycomic pattern in CRC; therefore, investigating these alterations may reveal new insights into the development of T1 CRC. We used matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging (MSI) to spatially profile the N-glycan species in a cohort of pT1 CRC using archival formalin-fixed and paraffin-embedded (FFPE) material. To generate structural information on the observed N-glycans, CE-ESI-MS/MS was used in conjunction with MALDI-MSI. Relative intensities and glycosylation traits were calculated based on a panel of 58 N-glycans. Our analysis showed pronounced differences between normal epithelium, dysplastic, and carcinoma regions. High-mannose-type N-glycans were higher in the dysplastic region than in carcinoma, which correlates to increased proliferation of the cells. We observed changes in the cancer invasive front, including higher expression of α2,3-linked sialic acids which followed the glycosylation pattern of the carcinoma region.

Deconvolution of bulk gene expression profiles into the cellular components is pivotal to portraying tissue’s complex cellular make-up, such as the tumor microenvironment. However, the inherently variable nature of gene expression requires a comprehensive statistical model and reliable prior knowledge of individual cell types that can be obtained from single-cell RNA sequencing. We introduce BLADE (Bayesian Log-normAl Deconvolution), a unified Bayesian framework to estimate both cellular composition and gene expression profiles for each cell type. Unlike previous comprehensive statistical approaches, BLADE can handle > 20 types of cells due to the efficient variational inference. Throughout an intensive evaluation with > 700 simulated and real datasets, BLADE demonstrated enhanced robustness against gene expression variability and better completeness than conventional methods, in particular, to reconstruct gene expression profiles of each cell type. In summary, BLADE is a powerful tool to unravel heterogeneous cellular activity in complex biological systems from standard bulk gene expression data. Deconvolution methods reveal individual cell types in complex tissues profiled by bulk methods. Here the authors present a Bayesian deconvolution method that outperforms existing methods when benchmarked on >700 datasets, especially in estimating cell-type-specific gene expression profiles.

BackgroundExpression of CD103 and CD39 has been found to pinpoint tumor-reactive CD8+ T cells in a variety of solid cancers. We aimed to investigate whether these markers specifically identify neoantigen-specific T cells in colorectal cancers (CRCs) with low mutation burden.Experimental designWhole-exome and RNA sequencing of 11 mismatch repair-proficient (MMR-proficient) CRCs and corresponding healthy tissues were performed to determine the presence of putative neoantigens. In parallel, tumor-infiltrating lymphocytes (TILs) were cultured from the tumor fragments and, in parallel, CD8+ T cells were flow-sorted from their respective tumor digests based on single or combined expression of CD103 and CD39. Each subset was expanded and subsequently interrogated for neoantigen-directed reactivity with synthetic peptides. Neoantigen-directed reactivity was determined by flow cytometric analyses of T cell activation markers and ELISA-based detection of IFN-γ and granzyme B release. Additionally, imaging mass cytometry was applied to investigate the localization of CD103+CD39+ cytotoxic T cells in tumors.ResultsNeoantigen-directed reactivity was only encountered in bulk TIL populations and CD103+CD39+ (double positive, DP) CD8+ T cell subsets but never in double-negative or single-positive subsets. Neoantigen-reactivity detected in bulk TIL but not in DP CD8+ T cells could be attributed to CD4+ T cells. CD8+ T cells that were located in direct contact with cancer cells in tumor tissues were enriched for CD103 and CD39 expression.ConclusionCoexpression of CD103 and CD39 is characteristic of neoantigen-specific CD8+ T cells in MMR-proficient CRCs with low mutation burden. The exploitation of these subsets in the context of adoptive T cell transfer or engineered T cell receptor therapies is a promising avenue to extend the benefits of immunotherapy to an increasing number of CRC patients.

Pancreatic cancer is the fourth leading cause of cancer-related mortality in the United States. The minority of patients can undergo curative-intended surgical therapy due to progressive disease stage at time of diagnosis. Nonetheless, tumor involvement of surgical margins is seen in up to 70% of resections, being a strong negative prognostic factor. Real-time intraoperative imaging modalities may aid surgeons to obtain tumor-free resection margins. Full-field optical coherence tomography (FF-OCT) is a promising diagnostic tool using high-resolution white-light interference microscopy without tissue processing. Therefore, we composed an atlas of FF-OCT images of malignant and benign pancreatic tissue, and investigated the accuracy with which the pathologists could distinguish these. One hundred FF-OCT images were collected from specimens of 29 patients who underwent pancreatic resection for various indications between 2014 and 2016. One experienced gastrointestinal pathologist and one pathologist in training scored independently the FF-OCT images as malignant or benign blinded to the final pathology conclusion. Results were compared to those obtained with standard hematoxylin and eosin (H&E) slides. Overall, combined test characteristics of both pathologists showed a sensitivity of 72%, specificity of 74%, positive predictive value of 69%, negative predictive value of 79% and an overall accuracy of 73%. In the subset of pancreatic ductal adenocarcinoma patients, 97% of the FF-OCT images (n = 35) were interpreted as tumor by at least one pathologist. Moreover, normal pancreatic tissue was recognised in all cases by at least one pathologist. However, atrophy and fibrosis, serous cystadenoma and neuroendocrine tumors were more often wrongly scored, in 63%, 100% and 25% respectively. FF-OCT could distinguish normal pancreatic tissue from pathologic pancreatic tissue in both processed as non-processed specimens using architectural features. The accuracy in pancreatic ductal adenocarcinoma is promising and warrants further evaluation using improved assessment criteria.

CDKN2A-p16-Leiden mutation carriers have a substantial risk of developing pancreatic ductal adenocarcinoma (PDAC). One of the main clinical features of hereditary cancer is the development of multiple cancers. Since 2000, we have run a surveillance program for CDKN2A-p16-Leiden mutation carriers. The patients are offered a yearly MRI with optionally endoscopic ultrasound. In patients with a confirmed lesion, usually, a partial resection of the pancreas is recommended. A total of 18 PDAC (8.3%) were detected in 218 mutation carriers. In this report, we describe two CDKN2A-p16-Leiden patients with a synchronous and metachronous PDAC. Including two previously-reported cases, we identified four patients with multiple PDAC: two of 18 patients within the surveillance program (11%) and two patients with a proven CDKN2A-p16-Leiden mutation not participating in the surveillance program. In conclusion, this study demonstrated a high risk of developing multiple PDAC in CDKN2A-p16-Leiden mutation carriers. After detecting a primary tumor, it is very important to exclude the presence of a second synchronous tumor. Moreover, after a partial pancreatectomy for PDAC, close surveillance is necessary. In view of the current findings, offering a total pancreatectomy might be an appropriate option in patients with an early PDAC.

Background: A substantial fraction of familial colorectal cancer (CRC) and polyposis heritability remains unexplained. This study aimed to identify predisposing loci in patients with these disorders. Methods: Homozygosity mapping was performed using 222 563 SNPs in 302 index patients with various colorectal neoplasms and 3367 controls. Linkage analysis, exome and whole-genome sequencing were performed in a family affected by microsatellite stable CRCs. Candidate variants were genotyped in 10 554 cases and 21 480 controls. Gene expression was assessed at the mRNA and protein level. Results: Homozygosity mapping revealed a disease-associated region at 1q32.3 which was part of the linkage region 1q32.2–42.2 identified in the CRC family. This includes a region previously associated with risk of CRC. Sequencing identified the p.Asp1432Glu variant in the MIA3 gene (known as TANGO1 or TANGO ) and 472 additional rare, shared variants within the linkage region. In both cases and controls the population frequency was 0.02% for this MIA3 variant. The MIA3 mutant allele showed predominant mRNA expression in normal, cancer and precancerous tissues. Furthermore, immunohistochemistry revealed increased expression of MIA3 in adenomatous tissues. Conclusions: Taken together, our two independent strategies associate genetic variations in chromosome 1q loci and predisposition to familial CRC and polyps, which warrants further investigation.