Epithelial cells remove precancerous cells by cell competition via MHC class I-LILRB3 interaction.

Epithelial cells have an ability termed 'cell competition', which is an immune surveillance-like function that extrudes precancerous cells from the epithelial layer, leading to apoptosis and clearance. However, it remains unclear how epithelial cells recognize and extrude transformed cells. Here, we discovered that a PirB family protein, leukocyte immunoglobulin-like receptor B3 (LILRB3), which is expressed on non-transformed epithelial cells, recognizes major histocompatibility complex class I (MHC class I) that is highly expressed on transformed cells. MHC class I interaction with LILRB3 expressed on normal epithelial cells triggers an SHP2-ROCK2 pathway that generates a mechanical force to extrude transformed cells. Removal of transformed cells occurs independently of natural killer (NK) cell or CD8+ cytotoxic T cell-mediated activity. This is a new mechanism in that the immunological ligand-receptor system generates a mechanical force in non-immune epithelial cells to extrude precancerous cells in the same epithelial layer.

Ubiquitination of hnRNPA1 by TRAF6 links chronic innate immune signaling with myelodysplasia.

Toll-like receptor (TLR) activation contributes to premalignant hematologic conditions, such as myelodysplastic syndromes (MDS). TRAF6, a TLR effector with ubiquitin (Ub) ligase activity, is overexpressed in MDS hematopoietic stem/progenitor cells (HSPCs). We found that TRAF6 overexpression in mouse HSPC results in impaired hematopoiesis and bone marrow failure. Using a global Ub screen, we identified hnRNPA1, an RNA-binding protein and auxiliary splicing factor, as a substrate of TRAF6. TRAF6 ubiquitination of hnRNPA1 regulated alternative splicing of Arhgap1, which resulted in activation of the GTP-binding Rho family protein Cdc42 and accounted for hematopoietic defects in TRAF6-expressing HSPCs. These results implicate Ub signaling in coordinating RNA processing by TLR pathways during an immune response and in premalignant hematologic diseases, such as MDS.

Dicarbonyl Electrophiles Mediate Inflammation-Induced Gastrointestinal Carcinogenesis.

BACKGROUND & AIMS: Inflammation in the gastrointestinal tract may lead to the development of cancer. Dicarbonyl electrophiles, such as isolevuglandins (isoLGs), are generated from lipid peroxidation during the inflammatory response and form covalent adducts with amine-containing macromolecules. Thus, we sought to determine the role of dicarbonyl electrophiles in inflammation-associated carcinogenesis. METHODS: The formation of isoLG adducts was analyzed in the gastric tissues of patients infected with Helicobacter pylori from gastritis to precancerous intestinal metaplasia, in human gastric organoids, and in patients with colitis and colitis-associated carcinoma (CAC). The effect on cancer development of a potent scavenger of dicarbonyl electrophiles, 5-ethyl-2-hydroxybenzylamine (EtHOBA), was determined in transgenic FVB/N insulin-gastrin (INS-GAS) mice and Mongolian gerbils as models of H pylori-induced carcinogenesis and in C57BL/6 mice treated with azoxymethane-dextran sulfate sodium as a model of CAC. The effect of EtHOBA on mutations in gastric epithelial cells of H pylori-infected INS-GAS mice was assessed by whole-exome sequencing. RESULTS: We show increased isoLG adducts in gastric epithelial cell nuclei in patients with gastritis and intestinal metaplasia and in human gastric organoids infected with H pylori. EtHOBA inhibited gastric carcinoma in infected INS-GAS mice and gerbils and attenuated isoLG adducts, DNA damage, and somatic mutation frequency. Additionally, isoLG adducts were elevated in tissues from patients with colitis, colitis-associated dysplasia, and CAC as well as in dysplastic tumors of C57BL/6 mice treated with azoxymethane-dextran sulfate sodium. In this model, EtHOBA significantly reduced adduct formation, tumorigenesis, and dysplasia severity. CONCLUSIONS: Dicarbonyl electrophiles represent a link between inflammation and somatic genomic alterations and are thus key targets for cancer chemoprevention.

Single-Cell Transcriptional Analyses Identify Lineage-Specific Epithelial Responses to Inflammation and Metaplastic Development in the Gastric Corpus.

BACKGROUND & AIMS: Chronic atrophic gastritis can lead to gastric metaplasia and increase risk of gastric adenocarcinoma. Metaplasia is a precancerous lesion associated with an increased risk for carcinogenesis, but the mechanism(s) by which inflammation induces metaplasia are poorly understood. We investigated transcriptional programs in mucous neck cells and chief cells as they progress to metaplasia mice with chronic gastritis. METHODS: We analyzed previously generated single-cell RNA-sequencing (scRNA-seq) data of gastric corpus epithelium to define transcriptomes of individual epithelial cells from healthy BALB/c mice (controls) and TxA23 mice, which have chronically inflamed stomachs with metaplasia. Chronic gastritis was induced in B6 mice by Helicobacter pylori infection. Gastric tissues from mice and human patients were analyzed by immunofluorescence to verify findings at the protein level. Pseudotime trajectory analysis of scRNA-seq data was used to predict differentiation of normal gastric epithelium to metaplastic epithelium in chronically inflamed stomachs. RESULTS: Analyses of gastric epithelial transcriptomes revealed that gastrokine 3 (Gkn3) mRNA is a specific marker of mouse gastric corpus metaplasia (spasmolytic polypeptide expressing metaplasia, SPEM). Gkn3 mRNA was undetectable in healthy gastric corpus; its expression in chronically inflamed stomachs (from TxA23 mice and mice with Helicobacter pylori infection) identified more metaplastic cells throughout the corpus than previously recognized. Staining of healthy and diseased human gastric tissue samples paralleled these results. Although mucous neck cells and chief cells from healthy stomachs each had distinct transcriptomes, in chronically inflamed stomachs, these cells had distinct transcription patterns that converged upon a pre-metaplastic pattern, which lacked the metaplasia-associated transcripts. Finally, pseudotime trajectory analysis confirmed the convergence of mucous neck cells and chief cells into a pre-metaplastic phenotype that ultimately progressed to metaplasia. CONCLUSIONS: In analyses of tissues from chronically inflamed stomachs of mice and humans, we expanded the definition of gastric metaplasia to include Gkn3 mRNA and GKN3-positive cells in the corpus, allowing a more accurate assessment of SPEM. Under conditions of chronic inflammation, chief cells and mucous neck cells are plastic and converge into a pre-metaplastic cell type that progresses to metaplasia.

Immunotherapy for the prevention of high-risk oral disorders malignant transformation: the IMPEDE trial.

BACKGROUND: Oral Potentially Malignant Disorders (OPMD) have a non-negligible malignant transformation rate of up to 8%. Loss of heterozygosity (LOH) in critical chromosomal loci has proven to be the most effective marker in defining the risk of transformation and it is found in about 28% of OPMD and may therefore identify patients carrying higher risk. To date, clinical management of OPMD is limited to surgical excision and clinical surveillance, which however do not fully prevent oral cancer development. Immune system has been shown to play a key role in transformation surveillance mechanism and an immunosuppressive imbalance may be responsible for progression to cancer. Given all these considerations, we designed a clinical trial with the aim to prevent OPMD neoplastic transformation and revert the LOH status. METHODS: This is a phase II, open label, single arm, multicentric trial involving Italian referral centres and expected to enrol 80 patients out of a total of 175 screened. Patients who meet all inclusion criteria and test positive for LOH after an incisional biopsy of the OPMD will undergo a short course of immunotherapy with 4 administration of avelumab. After 6 months since treatment start, resection of the entire OPMD will be performed and LOH assessment will be repeated. The follow-up for malignant transformation and safety assessment will last 30 months from the end of treatment, for a total planned study duration of approximately 5.5 years. DISCUSSION: Restoring the activity of immune system through checkpoint inhibitor may play a crucial role against malignant transformation of OPMD by reverting the balance in favour of immune control and preventing cancer occurrence. TRIAL REGISTRATION: This trial was prospectively registered in ClinicalTrials.gov as NCT04504552 on 7th August 2020.

Dissecting expression profiles of gastric precancerous lesions and early gastric cancer to explore crucial molecules in intestinal-type gastric cancer tumorigenesis.

Intestinal-type gastric cancer (IGC) has a clear and multistep histological evolution. No studies have comprehensively explored gastric tumorigenesis from inflammation through low-grade intraepithelial neoplasia (LGIN) and high-grade intraepithelial neoplasia (HGIN) to early gastric cancer (EGC). We sought to investigate the characteristics participating in IGC tumorigenesis and identify related prognostic information within the process. RNA expression profiles of 94 gastroscopic biopsies from 47 patients, including gastric precancerous lesions (GPL: LGIN and HGIN), EGC, and paired controls, were detected by Agilent Microarray. During IGC tumorigenesis from LGIN through HGIN to EGC, the number of activity-changed tumor hallmarks increased. LGIN and HGIN had similar expression profiles when compared to EGC. We observed an increase in the stemness of gastric epithelial cells in LGIN, HGIN, and EGC, and we found 27 consistent genes that might contribute to dedifferentiation, including five driver genes. Remarkably, we perceived that the immune microenvironment was more active in EGC than in GPL, especially in the infiltration of lymphocytes and macrophages. We identified a five-gene signature from the gastric tumorigenesis process that could independently predict the overall survival and disease-free survival of GC patients (log-rank test: p < 0.0001), and the robustness was verified in an independent cohort (n > 300) and by comparing with two established prognostic signatures in GC. In conclusion, during IGC tumorigenesis, cancer-like changes occur in LGIN and accumulate in HGIN and EGC. The immune microenvironment is more active in EGC than in LGIN and HGIN. The identified signature from the tumorigenesis process has robust prognostic significance for GC patients. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Vaccines for Non-Viral Cancer Prevention.

Cancer vaccines are a type of immune therapy that seeks to modulate the host's immune system to induce durable and protective immune responses against cancer-related antigens. The little clinical success of therapeutic cancer vaccines is generally attributed to the immunosuppressive tumor microenvironment at late-stage diseases. The administration of cancer-preventive vaccination at early stages, such as pre-malignant lesions or even in healthy individuals at high cancer risk could increase clinical efficacy by potentiating immune surveillance and pre-existing specific immune responses, thus eliminating de novo appearing lesions or maintaining equilibrium. Indeed, research focus has begun to shift to these approaches and some of them are yielding encouraging outcomes.

The innate immune architecture of lung tumors and its implication in disease progression.

Lung malignancies are the leading cause of cancer-related mortality. By virtue of its unique physiological function, the lung microenvironment is highly dynamic and constantly subjected to mechanical, chemical and pathogenic stimuli. Thus, the airways rely on highly organized innate defense mechanisms to rapidly protect against pathogens and maintain pulmonary homeostasis. However, in the context of lung malignancy, these defenses often provide collateral inflammatory insults that can foster tumor progression. This review summarizes the interactions between cancer cells, recruited immune cells and tissue-resident cell subpopulations, such as airway epithelial cells and alveolar macrophages, during homeostasis and disease. Furthermore, we examine the role of the lung immune landscape in response to current therapeutic interventions for cancer. Given the prevalence of lung malignancies, we propose that consideration of lung physiology as a whole is necessary to understand and treat these lethal diseases. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The Association Between Chronic Lymphocytic Thyroiditis and the Progress of Papillary Thyroid Cancer.

BACKGROUND: Whether chronic lymphocytic thyroiditis (CLT) influences the risk of development and the progression of papillary thyroid cancer (PTC) remains uncertain. We investigated the effects of CLT on the clinicopathologic features and prognosis of PTC. METHODS: Two thousand nine hundred twenty-eight consecutive patients with PTC treated between 2009 and 2017 were divided into two groups: one with chronic lymphocytic thyroiditis and one without; 1174 (40%) of the patients had coincident CLT. RESULTS: In univariate analysis, CLT correlated positively with small tumor size, frequent extrathyroidal extension, multifocal diseases, and p53 but negatively with central lymph node (LN) metastasis and BRAF mutation. In multivariate analysis, CLT was associated with extrathyroidal extension and multifocal disease; however, it was not a prognostic factor for recurrence even though it was associated with two aggressive factors. Compared with patients with PTC alone, there were more retrieved central LNs in the PTC + CLT group, and these patients also underwent more invasive diagnostic tests such as fine needle aspiration cytology and frozen biopsy of LN. CONCLUSIONS: The CLT patients with PTC had better behavior features and prognoses than did those with PTC alone despite frequent multifocality and extrathyroidal extension. However, precaution may be necessary to avoid performing invasive diagnostic procedures for lateral LN metastasis and to manage the patients appropriately.

The wound inflammatory response exacerbates growth of pre-neoplastic cells and progression to cancer.

There is a long-standing association between wound healing and cancer, with cancer often described as a "wound that does not heal". However, little is known about how wounding, such as following surgery, biopsy collection or ulceration, might impact on cancer progression. Here, we use a translucent zebrafish larval model of Ras(G12V)-driven neoplasia to image the interactions between inflammatory cells drawn to a wound, and to adjacent pre-neoplastic cells. We show that neutrophils are rapidly diverted from a wound to pre-neoplastic cells and these interactions lead to increased proliferation of the pre-neoplastic cells. One of the wound-inflammation-induced trophic signals is prostaglandin E2 (PGE2). In an adult model of chronic wounding in zebrafish, we show that repeated wounding with subsequent inflammation leads to a greater incidence of local melanoma formation. Our zebrafish studies led us to investigate the innate immune cell associations in ulcerated melanomas in human patients. We find a strong correlation between neutrophil presence at sites of melanoma ulceration and cell proliferation at these sites, which is associated with poor prognostic outcome.

Chronically stimulated human MAIT cells are unexpectedly potent IL-13 producers.

Mucosal-associated invariant T (MAIT) cells are unconventional T cells that recognize antigens derived from riboflavin biosynthesis. In addition to anti-microbial functions, human MAIT cells are associated with cancers, autoimmunity, allergies and inflammatory disorders, although their role is poorly understood. Activated MAIT cells are well known for their rapid release of Th1 and Th17 cytokines, but we have discovered that chronic stimulation can also lead to potent interleukin (IL)-13 expression. We used RNA-seq and qRT-PCR to demonstrate high expression of the IL-13 gene in chronically stimulated MAIT cells, and directly identify IL-13 using intracellular flow cytometry and multiplex bead analysis of MAIT cell cultures. This unexpected finding has important implications for IL-13-dependent diseases, such as colorectal cancer (CRC), that occur in mucosal areas where MAIT cells are abundant. We identify MAIT cells near CRC tumors and show that these areas and precancerous polyps express high levels of the IL-13 receptor, which promotes tumor progression and metastasis. Our data suggest that MAIT cells have a more complicated role in CRC than currently realized and that they represent a promising new target for immunotherapies where IL-13 can be a critical factor.

Cancer immunoprevention: from mice to early clinical trials.

Cancer immunoprevention is based on the fact that a functioning immune system controls tumor onset and development in humans and animals, thus leading to the idea that the enhancement of immune responses in healthy individuals could effectively reduce cancer risk later in life. Successful primary immunoprevention of tumors caused by hepatitis B and papilloma viruses is already implemented at the population level with specific vaccines. The immunoprevention of human tumors unrelated to infectious agents is an outstanding challenge. Proof-of-principle preclinical studies in genetically-modified or in carcinogen-exposed mice clearly demonstrated that vaccines and other immunological treatments induce host immune responses that effectively control tumor onset and progression, eventually resulting in cancer prevention. While a straightforward translation to healthy humans is currently unfeasible, a number of pioneering clinical trials showed that cancer immunoprevention can be effectively implemented in human cohorts affected by specific cancer risks, such as preneoplastic/early neoplastic lesions. Future developments will see the implementation of cancer immunoprevention in a wider range of conditions at risk of tumor development, such as the exposure to known carcinogens and genetic predispositions.

CD56+ immune cell infiltration and MICA are decreased in breast lobules with fibrocystic changes.

PURPOSE: While the role of natural killer (NK) cells in breast cancer therapy has been investigated, little information is known about NK cell function and presence in nonmalignant and premalignant breast tissue. Here, we investigate and quantify NK cell marker CD56 and activating ligand MICA in breast tissue with benign breast disease. METHODS: Serial tissue sections from 88 subjects, 44 with benign breast disease (BBD) who remained cancer-free, and 44 with BBD who later developed cancer, were stained with H&E, anti-MICA, and anti-CD56. Up to ten representative lobules were identified on each section. Using digital image analysis, MICA and CD56 densities were determined for each lobule, reported as percent of pixels in the lobule that registered as stained by each antibody. Analyses were performed on a per-subject and per-lobule basis. RESULTS: Per-subject multivariate analyses showed associations of CD56 and MICA with age: CD56 was increased in older subjects (p = 0.03), while MICA was increased in younger subjects (p = 0.005). Per-lobule analyses showed that CD56 and MICA levels were both decreased in lobules with fibrocystic change, with median levels of CD56 and MICA staining, respectively, at 0.31 and 7.0% in fibrocystic lobules compared to 0.76 and 12.2% in lobules without fibrocystic change (p < 0.001 for each). Among fibrocystic lobules, proliferative/atypical lobules showed significantly lower expression compared to nonproliferative lobules for MICA (p = 0.02) but not for CD56 (p = 0.80). CONCLUSION: Levels of CD56+ NK cells and activating ligand MICA were decreased in breast lobules with fibrocystic change, and MICA levels showed a significant stepwise decrease with increasing histopathologic abnormality. MICA levels were also significantly decreased in older subjects, who generally have higher risk of developing cancer. These findings advance a model in which MICA promotes cytotoxic activity in CD56+ NK cells to protect against tumorigenesis in breast lobules, and suggest further research is warranted.

Do not scratch that mole!

Nevi harbor some of the same oncogene mutations that also drive malign melanoma. Further tumor promoting events are required to unleash their carcinogenic potential. Using zebrafish whose melanocytes overexpress an HRAS-oncogene, a new study reports that injury induces melanoma, possibly through recruitment of neutrophils that trigger proliferation of preneoplastic melanocytes.

Evaluation of T-lymphocyte subpopulations in actinic keratosis, in situ and invasive squamous cell carcinoma of the skin.

BACKGROUND: Tumor infiltrating lymphocytes (TILs) represent important regulators of carcinogenesis. Cutaneous invasive squamous cell carcinoma (inSCC) develops through precursor lesions, namely in situ squamous cell carcinoma (isSCC) and actinic keratosis (AK), representing a natural model of carcinogenesis. The study evaluates TIL subpopulations in inSCC and its precursors by comparing 2 semiquantitative scoring systems, and assesses the presence of regulatory T-cells (Tregs) in these lesions. METHODS: Paraffin sections from 33 cases of AK, 19 isSCCs and 34 inSCCs with adjacent precursor lesions or normal skin (NS) were immunostained for CD3, CD4, CD8 and Foxp3. TIL subgroups were evaluated by the semiquantitative Klintrup-Mäkinen (K-M) score, and by a more detailed modification of this system. Treg counts were assessed by image analysis quantification. RESULTS: An increase of all TIL subpolulations from precursor lesions toward inSCC was shown by both scoring systems. Treg counts progressively increased from NS to AK and isSCC, but decreased in inSCC. Tregs were more numerous in pT2 and around indolent inSCCs compared to T1 and aggressive subtypes. CONCLUSIONS: T-cells and cytotoxic T-cells progressively increase in cutaneous squamous cell carcinogenesis, while Treg counts diminish in inSCC. The K-M score is an appropriate, easily applicable TIL scoring system in cutaneous inSCC.

Ataxia Telangiectasia and Cancer Predisposition: Challenges in Management.

Immune dysregulation and predisposition to malignancies are critical comorbidities in children affected with ataxia telangiectasia. In addition, these children exhibit increased toxicity to conventional cancer therapy and dose reductions have been proposed to prevent life threatening adverse effects. These modifications to the treatment regimen may result in suboptimal outcomes for these patients. Our report of 3 children with ataxia telangiectasia and cancer highlight the immense challenges in the management of these children, underlining the need for the development of novel, biological agents with reduced acute and long-term side effects in the treatment of cancers in these children.

Paper-based immunosensor with signal amplification by enzyme-labeled anti-p16INK4a multifunctionalized gold nanoparticles for cervical cancer screening.

The aim of this study was to develop a paper-based immunosensor for cervical cancer screening, with signal amplification by multifunctionalized gold nanoparticles (AuNPs). The AuNPs were functionalized with a highly specific antibody to the p16INK4a cancer biomarker. The signal was amplified using a combination of the peroxidase activity of horseradish peroxidase (HRP) enzyme-antibody conjugate and the peroxidase-like activity of the AuNPs. The immune complex of p16INK4a protein and multifunctionalized AuNPs was deposited on the nitrocellulose membrane, and a positive result was generated by catalytic oxidation of peroxidase enzyme substrate 3,3',5,5'-Tetramethylbenzidine (TMB). The entire reaction occurred on the membrane within 30 min. Evaluation in clinical samples revealed 85.2% accuracy with a kappa coefficient of 0.69. This proof of concept study demonstrates the successful development of a highly accurate, paper-based immunosensor that is easy to interpret using the naked eye and that is suitable for cervical cancer screening in low-resource settings.

FcRL4+ B-cells in salivary glands of primary Sjögren's syndrome patients.

Fc receptor-like protein 4 (FcRL4) is normally expressed on a small subset of mucosa-associated B-cells, as well as on mucosa-associated lymphoid tissue (MALT) lymphoma B-cells. Primary Sjögren's syndrome (pSS) patients have an increased risk of developing MALT lymphomas, preferentially in the parotid glands. For this reason we studied here by immunohistochemistry and mRNA analysis whether FcRL4 expressing B-cells are present in salivary gland tissue (labial and parotid) of pSS patients (n = 54) and non-pSS sicca patients (n = 16) and whether parotid gland MALT lymphomas in pSS patients (n = 49) also express this receptor. We also studied the effect of treatment (rituximab and abatacept) on the presence of FcRL4+ B-cells, and whether numbers in labial gland biopsies at time of diagnosis of pSS can predict whether patients are at risk for MALT lymphoma development. We demonstrate that FcRL4+ cells are present in salivary gland tissue of pSS patients where they are closely associated with ductal epithelial cells forming lymphoepithelial lesions. The glandular FcRL4+ cells are highly proliferative, genuine PAX5+ B-cells. These FcRL4+ B-cells are far more frequent in parotid gland than in labial gland tissue (p = 0.003). We further show that expression of FcRL4 is present in pSS-related parotid MALT lymphomas. The FcRL4 mRNA expression level in parotid MALT lymphoma is increased compared to parotid gland tissue of pSS patients without lymphoma (p = 0.017). However, numbers of FcRL4+ B-cells in labial gland biopsies taken at the time of pSS diagnosis, are not predictive for later development of MALT lymphoma. Reduction of parotid gland FcRL4+ B-cells by rituximab, but not abatacept is accompanied by restoration of the glandular epithelium, illustrating the crosstalk between these B-cells with the ductal cells. In conclusion, intraepithelial FcRL4+ B-cells are present in the salivary glands of pSS patients. These cells are likely involved in the epithelial changes seen in pSS. Their enrichment in parotid glands may explain why MALT lymphomas in pSS patients preferentially develop at this specific location.

PD-L1 overexpression in ampulla of Vater carcinoma and its pre-invasive lesions.

AIMS: PD-1/PD-L1 checkpoint immunotherapy has been proposed recently as a promising treatment in relapsed/refractory disease, used eventually in combination with traditional chemotherapy in different cancer settings. To date, no data are available concerning PD-L1 expression in ampulla of Vater carcinoma and its pre-invasive lesions. METHODS AND RESULTS: We assessed the immunohistochemical expression of PD-L1 in a series of 26 ampullary adenocarcinomas, 50 ampullary dysplastic lesions and 10 normal duodenal mucosa samples. Moreover, in all cases DNA mismatch repair proteins status was investigated. PD-L1 was expressed in seven of 26 (26.9%) invasive carcinomas and three of 50 (6.0%) dysplastic samples. Most of the PD-L1-positive tumours (seven of 10) were intestinal-type and poorly differentiated (G3). The number of PD-L1-positive stromal lymphoid cells was significantly higher in dysplastic and invasive lesions than in the normal samples (P = 0.011). Nineteen dysplastic lesions and eight invasive carcinomas did not show any evident epithelial or stromal PD-L1 expression. Four of the carcinomas were mismatch repair-deficient and two of these were PD-L1-positive. Furthermore, mismatch repair-deficient lesions showed a significantly higher average of PD-L1-positive stromal lymphoid cells than those of neoplastic PD-L1-negative samples (62.8 versus 21.6; P < 0.001). CONCLUSIONS: The present results suggest a role of the PD-1/PD-L1 axis in ampullary adenocarcinomas, and therefore this may also prompt consideration of checkpoint immunotherapy as a novel promising treatment for these tumours.

Senescence surveillance of pre-malignant hepatocytes limits liver cancer development.

Upon the aberrant activation of oncogenes, normal cells can enter the cellular senescence program, a state of stable cell-cycle arrest, which represents an important barrier against tumour development in vivo. Senescent cells communicate with their environment by secreting various cytokines and growth factors, and it was reported that this 'secretory phenotype' can have pro- as well as anti-tumorigenic effects. Here we show that oncogene-induced senescence occurs in otherwise normal murine hepatocytes in vivo. Pre-malignant senescent hepatocytes secrete chemo- and cytokines and are subject to immune-mediated clearance (designated as 'senescence surveillance'), which depends on an intact CD4(+) T-cell-mediated adaptive immune response. Impaired immune surveillance of pre-malignant senescent hepatocytes results in the development of murine hepatocellular carcinomas (HCCs), thus showing that senescence surveillance is important for tumour suppression in vivo. In accordance with these observations, ras-specific Th1 lymphocytes could be detected in mice, in which oncogene-induced senescence had been triggered by hepatic expression of Nras(G12V). We also found that CD4(+) T cells require monocytes/macrophages to execute the clearance of senescent hepatocytes. Our study indicates that senescence surveillance represents an important extrinsic component of the senescence anti-tumour barrier, and illustrates how the cellular senescence program is involved in tumour immune surveillance by mounting specific immune responses against antigens expressed in pre-malignant senescent cells.