Colon Immune-Related Adverse Events: Anti-CTLA-4 and Anti-PD-1 Blockade Induce Distinct Immunopathological Entities

Traditional Chinese medicine enhances the effectiveness of immune checkpoint inhibitors in tumor treatment: A mechanism discussion

ETHNOPHARMACOLOGICAL RELEVANCE

Immune checkpoint inhibitors (ICIs) have altered the landscape of tumor immunotherapy, offering novel therapeutic approaches alongside surgery, chemotherapy, and radiotherapy and significantly improving survival benefits. However, their clinical efficacy is limited in some patients, and their use may cause immune-related adverse events (irAEs). Integrating traditional Chinese medicine (TCM) with ICIs has demonstrated the potential to boost sensitization and reduce toxicity. Clinical trials and experimental explorations have confirmed that TCM and its active components synergistically enhance the effectiveness of ICIs.

AIMS

This narrative review summarizes the TCM practices that enhance the clinical efficacy and reduce irAEs of ICIs. This paper also summarizes the mechanism of experimental studies on the synergies of Chinese herbal decoctions, Chinese herbal preparation, and Chinese herbal active ingredients. Most of the studies on TCM combined with ICIs are basic experiments. We discussed the mechanism of TCM enhanced ICIs to provide reference for the research and development of TCM adjuvant immunotherapy.

METHODS

We conducted a literature search using PubMed and Chinese National Knowledge Infrastructure databases, with a focus on herbal decoction, Chinese medicine preparations, and active ingredients that boost the effectiveness of ICIs and reduce irAEs. The search keywords were "ICIs and traditional Chinese medicine", "PD-1 and traditional Chinese medicine", "PD-L1 and traditional Chinese medicine", "CTLA-4 and traditional Chinese medicine", "IDO1 and traditional Chinese medicine", "Tim-3 and traditional Chinese medicine", "TIGIT and traditional Chinese medicine", "irAEs and traditional Chinese medicine". The search period was from May 2014 to May 2024. Articles involving the use of TCM or its components in combination with ICIs and investigating the underlying mechanisms were screened. Finally, 30 Chinese medicines used in combination with ICIs were obtained to explore the mechanism. In the part of immune checkpoint molecules other than PD-1, there were few studies on the combined application of TCM, so studies involving the regulation of immune checkpoint molecules by TCM were included.

RESULTS

TCM has been shown to boost the effectiveness of ICIs and reduce irAEs. Researchers indicate that TCM and its active components can work synergistically with ICIs by regulating immune checkpoints PD-1, PD-L1, CTLA-4, and IDO1, regulating intestinal flora, improving tumor microenvironment and more.

CONCLUSIONS

Combining TCM with ICIs can play a better anti-tumor role, but larger samples and high-quality clinical trials are necessary to confirm this. Many Chinese medicines and their ingredients have been shown to sensitize ICIs in experimental studies, which provides a rich choice for the subsequent development of ICI enhancers.

Early identification and multidisciplinary management of immune checkpoint inhibitors associated colitis can improve patient outcomes

Currently, the use of immune checkpoint inhibitors (ICIs) has shown notable clinical efficacy in treating various malignant tumors, significantly improving patient prognosis. However, while ICIs enhance the body's anti-tumor effects, they can also trigger immune-related adverse events (irAEs), with ICI-associated colitis being one of the more prevalent forms. This condition can disrupt treatment, necessitate drug discontinuation, and adversely affect therapeutic outcomes. In severe cases, irAEs may even become life-threatening. A recent case report by Hong et al highlights the importance of vigilance for ICI-associated colitis in patients experiencing symptoms such as diarrhea and abdominal pain, which can arise both during and even after completion of ICI treatment. Early identification, multidisciplinary management, and continuous monitoring of patients are essential steps to further improve outcomes.

The growing potential of tofacitinib in immune checkpoint inhibitor-induced colitis: identifying remaining puzzle pieces

Immunotherapy, a primary anti-neoplastic treatment, exploits the patient’s immune system to kill neoplastic cells by modulating immune checkpoints such as cytotoxic T-lymphocyte antigen 4 and programmed cell death 1. Despite an apparent anti-neoplastic efficacy, immunotherapeutic agents are often accompanied by multiorgan toxicity, including gastrointestinal ones. This particular class of immunotherapy-related adverse events, mainly represented by diarrhea and colitis, necessitates a nuanced treatment strategy. Current treatments are primarily based on standardized severity grading systems to guide and proportion therapeutic interventions, ranging from simple behavioral modifications or conventional molecules (such as anti-diarrheal) to advanced biological treatments. Tofacitinib, a pan-Janus kinase inhibitor, emerged as a potential option for managing immune-related (IR) colitis by targeting hyperactivated T cells within the colic microenvironment. However, evidence supporting the use of tofacitinib in IR colitis is primarily derived from case reports and small case series, lacking robust randomized clinical trial data. While preliminary findings demonstrate encouraging clinical control of IR colitis with tofacitinib, further research is warranted to elucidate its efficacy, safety, optimal dosage, and treatment duration. Although there are some worries about its effects on cancer response and safety, current evidence indicates that tofacitinib could be seen as a possible treatment choice if other therapies with more robust evidence profiles have not been successful.

Endoscopic findings of immune checkpoint inhibitor-related gastrointestinal adverse events

The use of immune checkpoint inhibitors (ICIs) for the treatment of various malignancies is increasing. Immune-related adverse events can occur after ICI administration, with gastrointestinal adverse events constituting a significant proportion of these events. When ICI-related diarrhea/colitis is suspected, endoscopic evaluation is recommended to differentiate it from other etiologies and assess the severity of colitis. The distribution of intestinal inflammation in ICI-related colitis demonstrates a high frequency of extensive colitis (23-86%). However, isolated right-sided colitis (3-8%) and ileitis (2-16%) are less prevalent. Endoscopic findings vary and predominantly encompass features indicative of inflammatory bowel disease, including aphthae, ulcers, diffuse or patchy erythema, mucosal edema, loss of vascular pattern, and friability. The presence of ulcers and extensive intestinal inflammation are associated with a reduced response to treatment. Microscopic inflammation can be observed even in endoscopically normal mucosa, underscoring the need for biopsies of seemingly normal mucosa. Histological findings present with acute/chronic inflammation and occasionally exhibit characteristics observed in inflammatory bowel disease, microscopic colitis, or ischemic colitis. The first-line therapeutic choice for ICI-related diarrhea/colitis with a common terminology criteria for adverse events grade of 2 or above is corticosteroids, whereas infliximab and vedolizumab are recommended for refractory cases.

Leukocyte dysfunction and reduced CTLA-4 expression are associated with perianal Crohn's disease

Although perianal Crohn's disease (PCD) is highly associated with the exacerbated inflammation, the molecular basis and immunological signature that distinguish patients who present a history of perianal lesions are still unclear. This paper aims to define immunological characteristics related to PCD. In this cross-sectional observational study, we enrolled 20 healthy controls and 39 CD patients. Blood samples were obtained for the detection of plasma cytokines and lipopolysaccharides (LPS). Peripheral blood mononuclear cells (PBMCs) were phenotyped by flow cytometry. Leukocytes were stimulated with LPS or anti-CD3/anti-CD28 antibodies. Our results show that CD patients had augmented plasma interleukin (IL)-6 and LPS. However, their PBMC was characterized by decreased IL-6 production, while patients with a history of PCD produced higher IL-6, IL-8, and interferon-γ, along with decreased tumor necrosis factor alpha (TNF). CD patients had augmented FoxP3 and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) regulatory markers, though the PCD subjects presented a significant reduction in CTLA-4 expression. CTLA-4 as well as IL-6 and TNF responses were able to distinguish the PCD patients from those who did not present perianal complications. In conclusion, IL-6, TNF, and CTLA-4 exhibit a distinct expression pattern in CD patients with a history of PCD, regardless of disease activity. These findings clarify some mechanisms involved in the development of the perianal manifestations and may have a great impact on the disease management.

Management of liver and gastrointestinal toxicity induced by immune checkpoint inhibitors: Position statement of the AEEH-AEG-SEPD-SEOM-GETECCU

The development of the immune checkpoint inhibitors (ICI) is one of the most remarkable achievements in cancer therapy in recent years. However, their exponential use has led to an increase in immune-related adverse events (irAEs). Gastrointestinal and liver events encompass hepatitis, colitis and upper digestive tract symptoms accounting for the most common irAEs, with incidence rates varying from 2% to 40%, the latter in patients undergoing combined ICIs therapy. Based on the current scientific evidence derived from both randomized clinical trials and real-world studies, this statement document provides recommendations on the diagnosis, treatment and prognosis of the gastrointestinal and hepatic ICI-induced adverse events.

Targeted delivery of Fc-fused PD-L1 for effective management of acute and chronic colitis

The PD-1/PD-L1 pathway in mucosal immunity is currently actively explored and considered as a target for inflammatory bowel disease (IBD) treatment. However, systemic PD-L1 administration may cause unpredictable adverse effects due to immunosuppression. Here we show that reactive oxygen species (ROS)-responsive nanoparticles enhance the efficacy and safety of PD-L1 in a mouse colitis model. The nanoparticles control the accumulation and release of PD-L1 fused to Fc (PD-L1-Fc) at inflammatory sites in the colon. The nanotherapeutics shows superiority in alleviating inflammatory symptoms over systemic PD-L1-Fc administration and mitigates the adverse effects of PD-L1-Fc administration. The nanoparticles-formulated PD-L1-Fc affects production of proinflammatory and anti-inflammatory cytokines, attenuates the infiltration of macrophages, neutrophils, and dendritic cells, increases the frequencies of Treg, Th1 and Tfh cells, reshapes the gut microbiota composition; and increases short-chain fatty acid production. In summary, PD-L1-Fc-decorated nanoparticles may provide an effective and safe strategy for the targeted treatment of IBD.

Achilles' Heel of currently approved immune checkpoint inhibitors: immune related adverse events

Immunotherapy has revolutionized the cancer treatment landscape by opening up novel avenues for intervention. As the use of immune checkpoint inhibitors (ICIs) has exponentially increased, so have immune-related adverse events (irAEs). The mechanism of irAEs may involve the direct damage caused by monoclonal antibodies and a sequence of immune responses triggered by T cell activation. Common side effects include dermatologic toxicity, endocrine toxicity, gastrointestinal toxicity, and hepatic toxicity. While relatively rare, neurotoxicity, cardiotoxicity, and pulmonary toxicity can be fatal. These toxicities pose a clinical dilemma regarding treatment discontinuation since they can result in severe complications and necessitate frequent hospitalization. Vigilant monitoring of irAEs is vital in clinical practice, and the principal therapeutic strategy entails the administration of oral or intravenous glucocorticoids (GSCs). It may be necessary to temporarily or permanently discontinue the use of ICIs in severe cases. Given that irAEs can impact multiple organs and require diverse treatment approaches, the involvement of a multidisciplinary team of experts is imperative. This review aims to comprehensively examine the pathogenesis, clinical manifestations, incidence, and treatment options for various irAEs.

Management of liver and gastrointestinal toxicity induced by immune checkpoint inhibitors: Position statement of the AEEH-AEG-SEPD-SEOM-GETECCU

The development of the immune checkpoint inhibitors (ICI) is one of the most remarkable achievements in cancer therapy in recent years. However, their exponential use has led to an increase in immune-related adverse events (irAEs). Gastrointestinal and liver events encompass hepatitis, colitis and upper digestive tract symptoms accounting for the most common irAEs, with incidence rates varying from 2 % to 40 %, the latter in patients undergoing combined ICIs therapy. Based on the current scientific evidence derived from both randomized clinical trials and real-world studies, this statement document provides recommendations on the diagnosis, treatment and prognosis of the gastrointestinal and hepatic ICI-induced adverse events.

Role of HDAC6-STAT3 in immunomodulatory pathways in Colorectal cancer cells

Colorectal cancer (CRC) is one of the most common malignant neoplasms and the second leading cause of death from tumors worldwide. Therefore, there is a great need to study new therapeutical strategies, such as effective immunotherapies against these malignancies. Unfortunately, many CRC patients do not respond to current standard immunotherapies, making it necessary to search for adjuvant treatments. Histone deacetylase 6 (HDAC6) is involved in several processes, including immune response and tumor progression. Specifically, it has been observed that HDAC6 is required to activate the Signal Transducer and Activator of Transcription 3 (STAT3), a transcription factor involved in immunogenicity, by activating different genes in these pathways, such as PD-L1. Over-expression of immunosuppressive pathways in cancer cells deregulates T-cell activation. Therefore, we focused on the pharmacological inhibition of HDAC6 in CRC cells because of its potential as an adjuvant to avoid immunotolerance in immunotherapy. We investigated whether HDAC6 inhibitors (HDAC6is), such as Nexturastat A (NextA), affected STAT3 activation in CRC cells. First, we found that NextA is less cytotoxic than the non-selective HDACis panobinostat. Then, NextA modified STAT3 and decreased the mRNA and protein expression levels of PD-L1. Importantly, transcriptomic analysis showed that NextA treatment affected the expression of critical genes involved in immunomodulatory pathways in CRC malignancies. These results suggest that treatments with NextA reduce the functionality of STAT3 in CRC cells, impacting the expression of immunomodulatory genes involved in the inflammatory and immune responses. Therefore, targeting HDAC6 may represent an interesting adjuvant strategy in combination with immunotherapy.

Autoimmune PaneLs as PrEdictors of Toxicity in Patients TReated with Immune Checkpoint InhibiTors (ALERT)

BACKGROUND

Immune-checkpoint inhibitors (ICI) can lead to immune-related adverse events (irAEs) in a significant proportion of patients. The mechanisms underlying irAEs development are mostly unknown and might involve multiple immune effectors, such as T cells, B cells and autoantibodies (AutoAb).

METHODS

We used custom autoantigen (AutoAg) microarrays to profile AutoAb related to irAEs in patients receiving ICI. Plasma was collected before and after ICI from cancer patients participating in two clinical trials (NCT03686202, NCT02644369). A one-time collection was obtained from healthy controls for comparison. Custom arrays with 162 autoAg were used to detect IgG and IgM reactivities. Differences of median fluorescent intensity (MFI) were analyzed with Wilcoxon sign rank test and Kruskal-Wallis test. MFI 500 was used as threshold to define autoAb reactivity.

RESULTS

A total of 114 patients and 14 healthy controls were included in this study. irAEs of grade (G) ≥ 2 occurred in 37/114 patients (32%). We observed a greater number of IgG and IgM reactivities in pre-ICI collections from patients versus healthy controls (62 vs 32 p < 0.001). Patients experiencing irAEs G ≥ 2 demonstrated pre-ICI IgG reactivity to a greater number of AutoAg than patients who did not develop irAEs (39 vs 33 p = 0.040). We observed post-treatment increase of IgM reactivities in subjects experiencing irAEs G ≥ 2 (29 vs 35, p = 0.021) and a decrease of IgG levels after steroids (38 vs 28, p = 0.009).

CONCLUSIONS

Overall, these results support the potential role of autoAb in irAEs etiology and evolution. A prospective study is ongoing to validate our findings (NCT04107311).

Highly multiplexed spatial analysis identifies tissue-resident memory T cells as drivers of ulcerative and immune checkpoint inhibitor colitis

Colitis is a prevalent adverse event associated with immune checkpoint inhibitor (ICI) therapy with similarities to inflammatory bowel disease. Incomplete mechanistic understanding of ICI colitis curtails evidence-based treatment. Given the often-overlooked connection between tissue architecture and mucosal immune cell function, we here applied imaging mass cytometry (IMC) to gain spatial proteomic insight in ICI colitis in comparison to ulcerative colitis (UC). Using a cell segmentation pipeline that simultaneously utilizes high-resolution nuclear imaging and high-multiplexity IMC, we show that intra-epithelial CD8+ T cells are significantly more abundant (and numerically dominant) in anti-PD-1 ± anti-CTLA-4-induced colitis compared to anti-CTLA-4-induced colitis and UC. We identified activated, cycling CD8+ tissue-resident memory T(RM) cells at the lamina propria-epithelial interface as drivers of cytotoxicity in ICI colitis and UC. Moreover, we found that combined ICI-induced colitis featured highest granzyme B levels both in tissue and serum. Together, these data reinforce CD8+ TRM cells as potentially targetable drivers of ICI colitis.

Checkpoint Inhibitor-Induced Colitis: From Pathogenesis to Management

The advent of immunotherapy, specifically of immune checkpoint inhibitors (ICIs), for the treatment of solid tumors has deeply transformed therapeutic algorithms in medical oncology. Approximately one-third of patients treated with ICIs may de velop immune-related adverse events, and the gastrointestinal tract is often affected by different grades of mucosal inflammation. Checkpoint inhibitors colitis (CIC) presents with watery or bloody diarrhea and, in the case of severe symptoms, requires ICIs discontinuation. The pathogenesis of CIC is multifactorial and still partially unknown: anti-tumor activity that collaterally effects the colonic tissue and the upregulation of specific systemic inflammatory pathways (i.e., CD8+ cytotoxic and CD4+ T lymphocytes) are mainly involved. Many questions remain regarding treatment timing and options, and biological treatment, especially with anti-TNF alpha, can be offered to these patients with the aim of rapidly resuming oncological therapies. CIC shares similar pathogenesis and aspects with inflammatory bowel disease (IBD) and the use of ICI in IBD patients is under evaluation. This review aims to summarize the pathogenetic mechanism underlying CIC and to discuss the current evidenced-based management options, including the role of biological therapy, emphasizing the relevant clinical impact on CIC and the need for prompt recognition and treatment.

Position statement on the management of the immune checkpoint inhibitor-induced colitis via multidisciplinary modified Delphi consensus

INTRODUCTION

The use of immune checkpoint inhibitors (ICIs) in cancer immunotherapy has shown increased overall survival in a wide range of cancer types with the associated risk of developing severe immune-mediated adverse events, commonly involving the gastrointestinal tract.

AIM

The aim of this position statement is to provide an updated practice advice to the gastroenterologists and oncologists on the diagnosis and management of ICI-induced gastrointestinal toxicity.

METHODOLOGY

The evidence reviewed in this paper includes a comprehensive search strategy of English language publications. Consensus was reached using a three-round modified Delphi methodology and approved by the members of the Belgian Inflammatory Bowel Disease Research and Development Group (BIRD), Belgian Society of Medical Oncology (BSMO), Belgian group of Digestive Oncology (BGDO), and Belgian Respiratory Society (BeRS).

CONCLUSIONS

The management of ICI-induced colitis requires an early multidisciplinary approach. A broad initial assessment is necessary (clinical presentation, laboratory markers, endoscopic and histologic examination) to confirm the diagnosis. Criteria for hospitalisation, management of ICIs, and initial endoscopic assessment are proposed. Even if corticosteroids are still considered the first-line therapy, biologics are recommended as an escalation therapy and as early treatment in patients with high-risk endoscopic findings.

Pembrolizumab-Induced Fatal Myasthenia, Myocarditis, and Myositis in a Patient with Metastatic Melanoma: Autopsy, Histological, and Immunohistochemical Findings-A Case Report and Literature Review

Immune checkpoint inhibitors (ICIs) represent a major advance in cancer treatment. The lowered immune tolerance induced by ICIs brought to light a series of immune-related adverse events (irAEs). Pembrolizumab belongs to the ICI class and is a humanized IgG4 anti-PD-1 antibody that blocks the interaction between PD-1 and PD-L1. The ICI-related irAEs involving various organ systems and myocarditis are uncommon (incidence of 0.04% to 1.14%), but they are associated with a high reported mortality. Unlike idiopathic inflammatory myositis, ICI-related myositis has been reported to frequently co-occur with myocarditis. The triad of myasthenia, myositis, and myocarditis must not be underestimated as they can rapidly deteriorate, leading to death. Herein we report a case of a patient with metastatic melanoma who fatally developed myasthenia gravis, myocarditis, and myositis, after a single cycle of pembrolizumab. Considering evidence from the literature review, autopsy, histological, and immunohistochemical investigations on heart and skeletal muscle are presented and discussed, also from a medical-legal perspective.

Collagenous Colitis in a Patient With Gastric Cancer Who Underwent Chemotherapy

Herein, we present a case of collagenous colitis in a patient who underwent chemotherapy for gastric cancer, comprising five cycles of S-1 plus oxaliplatin and trastuzumab, followed by five cycles of paclitaxel and ramucirumab and seven cycles of nivolumab. The subsequent initiation of trastuzumab deruxtecan chemotherapy led to the development of grade 3 diarrhea after the second cycle of treatment. Collagenous colitis was diagnosed via colonoscopy and biopsy. The patient's diarrhea improved following the cessation of lansoprazole. This case highlights the importance of considering collagenous colitis as a differential diagnosis, in addition to chemotherapy-induced colitis and immune-related adverse event (irAE) colitis, in patients with similar clinical presentations.

Immune Checkpoint Inhibitor Enterocolitis vs Idiopathic Inflammatory Bowel Disease

Immune checkpoint inhibitors have revolutionized management of advanced malignancies. However, their use is frequently complicated by immune related adverse events (irAEs), immune checkpoint inhibitor enterocolitis (IMEC) being the most common toxicity. IMEC is a distinct form of bowel inflammation that is highly reminiscent of idiopathic inflammatory bowel disorders (Crohn's disease, ulcerative colitis, and microscopic colitis). In this review, we highlight the similarities and differences in the pathophysiology, clinical presentation, evaluation, and management of these overlapping immune inflammatory bowel disorders. IMEC is an inflammatory bowel disease-like irAE that occurs as an outcome of disruption of intestinal immune surveillance and gut dysbiosis. Clinical and endoscopic presentation of both entities is strikingly similar, which often guides management. Though well established in inflammatory bowel disease, little is known about the long term outcomes of IMEC.

Immune-related colitis and pancreatitis treated with infliximab

Patients with various cancers benefit from immune checkpoint inhibitors. However, immune checkpoint inhibitor-induced adverse events have also been reported, such as colitis. Prednisolone is the first-line treatment for immune-related adverse events, but second-line therapy for patients refractory to steroids has not been established. Furthermore, the inflammatory cytokine expression pattern in the intestinal mucosa of patients with steroid-refractory immune-related colitis remains unclear. We present the case of a 48-year-old man diagnosed with immune-related colitis and pancreatitis induced by pembrolizumab for advanced lung cancer. First, we administered 50 mg/day of prednisolone, and the patient's abdominal symptoms improved. However, the pancreatic enzyme levels did not return to normal. Furthermore, the patient's diarrhea worsened and hematochezia appeared at a 40 mg/day prednisolone dose. A mucosal cytokine analysis identified a low interleukin-10 messenger RNA level, which has been associated with a poor response to prednisolone. Thus, we administered 5 mg/kg of infliximab; the patient's diarrhea and hematochezia immediately improved, and the pancreatic enzyme levels returned to normal. Infliximab was administered three times every 2 weeks. After, the patient's colitis and pancreatitis did not recur. To our knowledge, this is the first report demonstrating the effectiveness of infliximab for immune-related colitis and pancreatitis.

Immune-related adverse events in checkpoint blockade: Observations from human tissue and therapeutic considerations

Checkpoint inhibitors (CPIs) are monoclonal antibodies which, by disrupting interactions of immune checkpoint molecules with their ligands, block regulatory immune signals otherwise exploited by cancers. Despite revolutionary clinical benefits, CPI use is associated with an array of immune-related adverse events (irAEs) that mirror spontaneous autoreactivity. Severe irAEs necessitate pausing or stopping of CPI therapy and use of corticosteroids and/or other immunomodulatory interventions. Despite increasingly widespread CPI use, irAE pathobiology remains poorly understood; its elucidation may point to targeted mitigation strategies and uncover predictive biomarkers for irAE onset in patients, whilst casting new light on mechanisms of spontaneous immune-mediated disease. This review focuses on common CPI-induced irAEs of the gut, skin and synovial joints, and how these compare to immune-mediated diseases such as ulcerative colitis, vitiligo and inflammatory arthritis. We review current understanding of the immunological changes reported following CPI therapy at the level of peripheral blood and tissue. Many studies highlight dysregulation of cytokines in irAE-affected tissue, particularly IFNγ and TNF. IrAE-affected tissues are also predominantly infiltrated by T-cells, with low B-cell infiltration. Whilst there is variability between studies, patients treated with anti-programmed cell death-1 (PD-1)/PDL-1 therapies seem to exhibit CD8+ T-cell dominance, with CD4+ T-cells dominating in those treated with anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) monotherapy. Interestingly, CD8+CXCR3+ T-cells have been reported to be elevated in gastrointestinal, dermatological and musculoskeletal -irAE affected tissues. These findings may highlight potential opportunities for therapeutic development or re-deployment of existing therapies to prevent and/or improve the outcome of irAEs.

The multifaceted roles of common gut microbiota in immune checkpoint inhibitor-mediated colitis: From mechanism to clinical application

With the arrival of the era of tumor immunotherapy, Immune Checkpoint Inhibitors have benefited countless tumor patients. However, the emergence of Immune-Related Adverse Events, especially Immune Checkpoint Inhibitor-Mediated Colitis (IMC), has become an important obstacle to immunotherapy. Therefore, it is very important to clarify the mechanism and influencing factors of IMC. The effect of gut microbiota on IMC is gradually becoming a research hotspot. Gut microbiota from different phyla can affect IMC by regulating innate and acquired immunity of tumor patients in various ways. In this review, we make a systematic and comprehensive introduction of the effect of gut microbiota on IMC. Through understanding the specific effects of gut microbiota on IMC, and then exploring the possibility of reducing IMC by regulating gut microbiota.

The diagnosis of immune-related pancreatitis disguised as multifocal lesions on MRI by endoscopic ultrasound-guided fine-needle biopsy: A case report

Immune checkpoint inhibitor (ICI)–related acute pancreatitis (irAP) is a rare, potentially life-threatening immune-related adverse event. Whereas CT and MRI remain first-line diagnostic imaging modalities, more patients are presenting with atypical irAP as ICI use increases. To appropriately manage these events, it is important to catalog these presentations and provide comprehensive clinical, radiological, and pathological descriptions to guide evidence-based practice. Here, we present the case of a 66-year-old man with advanced lung adenocarcinoma who, after the fifth course of toripalimab, developed epigastric discomfort and elevated serum amylase and lipase. irAP was suspected, but MRI revealed atypical, multifocal pancreatic lesions. To exclude metastases, an endoscopic ultrasound-guided fine-needle biopsy (EUS-FNB) was performed. EUS revealed a slightly swollen pancreas with heterogeneous echoic signals and scattered hyperechoic areas in the parenchyma without an obvious mass. Histopathological examination of the FNB revealed retention of the normal lobular pancreatic architecture with focal acinar atrophy associated with a CD8⁺ T lymphocyte-predominant infiltrate, further confirming the diagnosis of irAP. After starting glucocorticoids, his symptoms resolved, serum amylase and lipase rapidly decreased to normal, and the abnormal MRI features diminished. irAP can, therefore, present as multifocal lesions on MRI, and, when metastatic disease requires exclusion, EUS-FNB is an effective way to establish a definitive diagnosis. Refining the histopathological and immunopathological criteria for the diagnosis of irAP is now warranted.

Mesalamine and cholestyramine for immune checkpoint inhibitor-mediated diarrhea and colitis

PURPOSE

Immune checkpoint inhibitors (ICI) are effective against various malignancies. However, adverse events including diarrhea and colitis can lead to significant morbidity and mortality. Recommendations for the management of ICI mediated diarrhea and colitis include steroids and biologics. Given their associated risks, this study evaluated the role of the non-immunosuppressive agents, mesalamine and or cholestyramine.

METHODS

This is a retrospective, descriptive, single-center study of adults who developed ICI diarrhea and colitis between 2010 and 2020 at MD Anderson Cancer Center. Clinical data and outcomes were compared between those treated with the non-immunosuppressive therapies mesalamine and/or cholestyramine alone versus those who received additional immunosuppression with steroids and biologics.

RESULTS

Our sample comprised 66 patients wherein, the mean age was 63 years, 71% were males, and 97% had stage III/IV cancers. Fourteen patients were treated successfully with non-immunosuppressive therapy. They had grade 1-3 diarrhea and 1-2 colitis with no difference in the rate of histologic colitis compared to those who received immunosuppressive therapy. They had less CTLA-4 inhibitor-based therapy (36% vs. 73%, p = 0.034), delayed onset of symptoms (159 vs. 64 days, p = 0.011), lower fecal calprotectin levels (56 vs. 234, p = 0.012) and were more likely to resume ICI therapy (64% vs. 25%, p = 0.006).

CONCLUSION

Mesalamine and/or cholestyramine may be effective for mild ICI diarrhea and colitis among patients with delayed symptom onset with lower colonic inflammatory burden. Prospective studies randomizing patients with mild colitis between mesalamine/cholestyramine and immunosuppressive treatment are warranted to assess their efficacy and safety.

Immunotherapy-induced Colitis: A Comprehensive Review of Epidemiology, Clinical Presentation, Diagnostic Workup, and Management Plan

Immune checkpoint inhibitors (ICIs) have revolutionized the treatment of a variety of malignancies including advanced melanoma, non-small cell lung cancer, renal cell carcinoma, head and neck cancers among others. Since their introduction, there has been significant improvement in survival and prognosis in patients with advanced malignancies. Unfortunately, improved outcomes have come at a price of significant immune-related adverse events, with those of the gastrointestinal tract being the most common. Gastrointestinal immune-related adverse events frequently present as diarrhea and colitis, the severity of which can range from mild diarrhea to fulminant colitis with intestinal perforation. Currently, management of ICI-induced colitis is primarily guided by retrospective studies and expert opinion. A significant number of ICI-induced colitis responds to high-dose corticosteroids; however, some patients require further therapy with biologics. There is limited information on the factors which may predispose patients to ICI-induced colitis. Future research elucidating these risk factors along with development of a scoring system could allow for risk-stratification of patients before initiation of ICI therapy. Such a system may help clinicians and patients keep a high index of suspicion regarding ICI-induced colitis and could hopefully reduce the incidence of severe cases. Similarly, future studies should investigate protective factors against ICI-induced colitis, which could potentially allow more patients to safely benefit from ICI therapy.

Predictive Biomarkers of Severe Immune-Related Adverse Events With Immune Checkpoint Inhibitors: Prevention, Underlying Causes, Intensity, and Consequences

Immune checkpoint inhibitors (ICIs) have dramatically transformed oncology by prolonging overall survival and yielding better patient tolerance compared to other chemotherapeutic agents. However, numerous questions remain unanswered about the toxicity profile of ICIs, its relationship with the treatment response, and causes underlying the excellent treatment response in some patients, while recalcitrance in others. Research groups have continued to seek biomarkers that may permit the identification of treatment responders and predict toxicity to facilitate cessation of immunotherapy before the development of severe toxicity. However, some studies have found associations between serious adverse events and longer survivorship. The research question entailed determining whether a biomarker is needed to predict severe immune-related adverse events prior to their development or whether providing early treatment for toxicity would inhibit the immune system from attaining a long-lasting anti-tumor effect. Therefore, this review conducted an in-depth analysis into the molecular basis of these observations.

Pharmacological Treatments Available for Immune-Checkpoint-Inhibitor-Induced Colitis

Immune checkpoint inhibitor treatment has shown revolutionary therapeutic effects in various carcinomas. However, immune-related adverse events (irAE) following this treatment can sometimes lead to treatment discontinuation. One such frequently encountered adverse event is immune-related colitis (irAE colitis). Corticosteroids (CS) are the first-line treatment for irAE colitis, but we often encounter CS-refractory or -resistant cases. The application of multiple biologics has been proposed as a therapy to be administered after CS treatment; however, the efficacy and safety of biologics for patients with irAE colitis who do not respond to CS have not been established. This review summarizes the treatment regimens available for irAE colitis, focusing on the mechanism of action of corticosteroids, infliximab, vedolizumab, and other drugs.

Gut inflammation induced by drugs: Can pathology help to differentiate from inflammatory bowel disease?

Drug‐induced mucosal injury (DIMI) in the gastrointestinal tract is important to recognise, partly because cessation of the culprit agent alone may result in resolution of symptoms. An ever‐growing list of medications, including newer immunotherapeutic agents and targeted therapies, can cause gastrointestinal inflammation of varying severity. However, the diagnosis of DIMI is challenging, as a single drug can induce a variety of histopathological patterns of injury including acute colitis, chronic colitis, microscopic colitis, apoptotic colopathy, and ischaemic‐type colitis. An additional consideration is the potential clinical, endoscopic and histological overlap of DIMI with gastrointestinal mucosal injury secondary to other entities such as inflammatory bowel disease (IBD). We discuss DIMI of the gastrointestinal tract with an emphasis on histological patterns that mimic IBD, histological features which may distinguish the two entities, and the diagnostic role and limitations of the pathologist.

IL-6 blockade in cancer patients treated with immune checkpoint blockade: A win-win strategy

Increasing the efficacy of immune checkpoint blockade therapy while mitigating toxicity is one of the major challenges in oncology research. In this issue of Cancer Cell, Hailemichael et al. provide a strong rationale for the combination of IL-6 blockade and dual inhibition of CTLA-4 and PD-1 to overcome this issue.

The cure from within? a review of the microbiome and diet in melanoma

Therapy for cutaneous melanoma, the deadliest of the skin cancers, is inextricably linked to the immune system. Once thought impossible, cures for metastatic melanoma with immune checkpoint inhibitors have been developed within the last decade and now occur regularly in the clinic. Unfortunately, half of tumors do not respond to checkpoint inhibitors and efforts to further exploit the immune system are needed. Tantalizing associations with immune health and gut microbiome composition suggest we can improve the success rate of immunotherapy. The gut contains over half of the immune cells in our bodies and increasingly, evidence is linking the immune system within our gut to melanoma development and treatment. In this review, we discuss the importance the skin and gut microbiome may play in the development of melanoma. We examine the differences in the microbial populations which inhabit the gut of those who develop melanoma and subsequently respond to immunotherapeutics. We discuss the role of dietary intake on the development and treatment of melanoma. And finally, we review the landscape of published and registered clinical trials therapeutically targeting the microbiome in melanoma through dietary supplements, fecal microbiota transplant, and microbial supplementation.

Endoscopic and histopathologic features of Anti‐PD‐1‐related collagenous colitis

Objectives

Cancer patients treated with immune checkpoint inhibitors occasionally show persistent diarrhea accompanied by endoscopic features of ulcerative colitis. The endoscopic mucosal inflammation may appear mild in some patients compared to the clinical severity, which can make choosing a treatment challenging. In this study, we evaluated the factors that support the continuation of chemotherapy by assessing the endoscopic and histopathological characteristics of patients who experienced diarrhea after immune checkpoint inhibitor administration.

Methods

This study included eight patients who were diagnosed with collagenous colitis based on pathological assessments. We retrospectively investigated these patients’ backgrounds, laboratory data, and computed tomography images that were extracted from their medical records. We also summarized their endoscopic and pathologic findings.

Results

All eight patients were being treated with anti‐programmed cell death‐1/programmed cell death‐ligand 1 therapeutic agents and had a recent history of oral proton pump inhibitor therapy. The anti‐programmed cell death‐1‐related collagenous colitis in these cases was characterized by endoscopically mild mucosal inflammation, high fecal calprotectin levels, and a lower frequency of intestinal wall thickening on computed tomography. Histological assessments showed CD8⁺ lymphocytes predominantly infiltrating the lamina propria and crypts of the colonic mucosa. Suspending the proton pump inhibitor therapy relieved the patients’ symptoms and allowed the continuation of the anti‐programmed cell death‐1/programmed cell death‐ligand 1 therapy.

Conclusions

Anti‐programmed cell death‐1‐related collagenous colitis is reversible; appropriate diagnosis of adverse events is crucial for the continuation of immune checkpoint inhibitor therapy.

Clinical Course and Impact of Immune Checkpoint Inhibitor Colitis Resembling Microscopic Colitis

Background

Microscopic colitis (MC) is suspected to result from increased immune activity in gut mucosa. Immune checkpoint inhibitors (ICIs) treat cancer by activating the immune system, and further investigation is needed regarding their role in the development of MC.

Methods

A retrospective case series investigated cases of endoscopically and histologically confirmed MC developing after administration of ICIs. Clinical notes and medication administration records were reviewed for demographics, symptom duration, and treatment response.

Results

Nineteen cases of de novo MC were identified, with 95% of cases requiring steroid treatment, 53% presenting with hospitalization, and colitis-related mortality in 1 individual. Symptom onset occurred a median of 160 days after initiation of ICI therapy and 53 days after their most recent dose of therapy. Patients had a median of 125 days of symptoms, and ICI therapy was held in 70% of individuals due for treatment.

Conclusions

MC can develop after ICI administration, and presents with severe symptoms, often requiring hospitalization and steroid treatment. In certain individuals this can require a prolonged treatment course of steroid therapy or immunomodulators. Individuals developing diarrhea after ICI therapy warrant thorough workup including endoscopy and rapid treatment initiation given the disease severity observed in this series.

Checkpoint Inhibitors and the Gut

Checkpoint inhibitors have revolutionized treatments in modern oncology, including many conditions previously relegated to palliative therapies only. However, emerging recognition of checkpoint inhibitor-related adverse events has complicated the status of checkpoint inhibitor-related therapies. This review article discusses gastrointestinal adverse events as a result of checkpoint inhibitor therapy, as well as limitations of current guidelines, thus providing recommendations for guideline revision and future study direction.

Insights into Modern Therapeutic Approaches in Pediatric Acute Leukemias

Pediatric cancers predominantly constitute lymphomas and leukemias. Recently, our knowledge and awareness about genetic diversities, and their consequences in these diseases, have greatly expanded. Modern solutions are focused on mobilizing and impacting a patient’s immune system. Strategies to stimulate the immune system, to prime an antitumor response, are of intense interest. Amid those types of therapies are chimeric antigen receptor T (CAR-T) cells, bispecific antibodies, and antibody–drug conjugates (ADC), which have already been approved in the treatment of acute lymphoblastic leukemia (ALL)/acute myeloid leukemia (AML). In addition, immune checkpoint inhibitors (ICIs), the pattern recognition receptors (PRRs), i.e., NOD-like receptors (NLRs), Toll-like receptors (TLRs), and several kinds of therapy antibodies are well on their way to showing significant benefits for patients with these diseases. This review summarizes the current knowledge of modern methods used in selected pediatric malignancies and presents therapies that may hold promise for the future.

Differential diagnosis and management of immune checkpoint inhibitor-induced colitis: A comprehensive review

Immune checkpoint inhibitors (ICIs) are a new class of cancer pharmacotherapy consisting of antibodies that block inhibitory immune regulators such as cytotoxic T lymphocyte antigen 4, programmed cell death 1 and programmed death-ligand 1. Checkpoint blockade by ICIs reactivates a tumor-specific T cell response. Immune-related adverse events can occur in various organs including skin, liver, and gastrointestinal tract. Mild to severe colitis is the most common side effect with some experiencing rapid progression to more serious complications including bowel perforation and even death. Prompt diagnosis and management of ICI-induced colitis is crucial for optimal outcome. Unfortunately, its clinical, endoscopic and histopathologic presentations are non-specific and overlap with those of colitis caused by other etiologies, such as infection, medication, graft-versus-host disease and inflammatory bowel disease. Thus, a definitive diagnosis can only be rendered after these other possible etiologies are excluded. Sometimes an extensive clinical, laboratory and radiologic workup is required, making it challenging to arrive at a prompt diagnosis. Most patients experience full resolution of symptoms with corticosteroids and/or infliximab. For ICI-induced colitis that is treatment-refractory, small scale studies offer alternative strategies, such as vedolizumab and fecal microbiota transplantation. In this review, we focus on the clinical features, differential diagnosis, and management of ICI-induced colitis with special attention to emerging treatment options for treatment-refractory ICI-induced colitis.

Immune Checkpoint Inhibitor-Associated Colitis: From Mechanism to Management

Immune checkpoint inhibitors (ICIs), as one of the innovative types of immunotherapies, including programmed cell death-1 (PD-1), programmed cell death-ligand 1 (PD-L1), and cytotoxic T lymphocyte antigen 4 (CTLA-4) inhibitors, have obtained unprecedented benefit in multiple malignancies. However, the immune response activation in the body organs could arise immune-related adverse events (irAEs). Checkpoint inhibitor colitis (CIC) is the most widely reported irAEs. However, some obscure problems, such as the mechanism concerning gut microbiota, the confusing differential diagnosis with inflammatory bowel disease (IBD), the optimal steroid schedule, the reintroduction of ICIs, and the controversial prognosis features, influence the deep understanding and precise diagnosis and management of CIC. Herein, we based on these problems and comprehensively summarized the relevant studies of CIC in patients with NSCLC, further discussing the future research direction of this specific pattern of irAEs.

Immune Checkpoint Blockade and Skin Toxicity Pathogenesis

Immune checkpoint blockade has revolutionized the treatment of multiple tumor types, including melanoma and nonmelanoma skin cancers. The use of immune checkpoint blockade is curtailed by tissue toxicities termed immune-related adverse events (irAEs), which occur most quickly and most often in the skin. We review the rationale for immune checkpoint blockade use, current agents, use in skin cancers, autoimmune manifestations in the skin, and considerations for predictive biomarkers and treatment options on the basis of skin pathogenesis. We also highlight major gaps in the field and the lack of preclinical modeling in the skin. A deeper understanding of irAE pathophysiology may help to uncouple toxicity and efficacy but mandates an interdisciplinary approach, including foundational skin immunology and autoimmune pathogenesis.

Gastrointestinal Adverse Events Induced by Immune-Checkpoint Inhibitors

BACKGROUND

As immune-checkpoint inhibitors (ICI) are becoming standard therapies for malignant tumors, increasing attention has been paid to their associated immune-related adverse events (irAEs). The gastrointestinal tract is the major site of irAEs, and it has recently become evident that the large bowel is the most frequently affected region. The aim of this narrative review was to clarify the endoscopic and histopathologic findings of and treatments for ICI-induced colitis.

SUMMARY

Endoscopic findings of ICI-induced colitis include a reddish, edematous mucosa with increased mucous exudate, loss of normal vascularity, and a granular mucosa with or without mucosal breaks. Histopathologic findings of ICI-induced colitis are expansion of the lamina propria, intraepithelial infiltration of neutrophils, crypt architectural distortion, neutrophilic crypt abscess, and prominent apoptosis. The clinical, endoscopic, and histopathologic severity of ICI-induced colitis is diverse, but colonoscopy together with biopsy is necessary for diagnosis. While a certain proportion of patients with ICI-induced colitis have an intractable clinical course, management guidelines are based on retrospective analyses. Prospective studies are needed to assess the efficacy of various medications, including immunosuppressive regimens. Key Messages: Colonoscopy with biopsy is the gold standard for the diagnosis of ICI-induced colitis. Endoscopists should be aware of the clinical features and pathophysiology of ICI-induced colitis for prompt diagnosis and treatment planning.

Mechanisms of Immune Checkpoint Inhibitor-Mediated Colitis

Immune checkpoint inhibitors (ICIs) have provided tremendous clinical benefit in several cancer types. However, systemic activation of the immune system also leads to several immune-related adverse events. Of these, ICI-mediated colitis (IMC) occurs frequently and is the one with the highest absolute fatality. To improve current treatment strategies, it is important to understand the cellular mechanisms that induce this form of colitis. In this review, we discuss important pathways that are altered in IMC in mouse models and in human colon biopsy samples. This reveals a complex interplay between several types of immune cells and the gut microbiome. In addition to a mechanistic understanding, patients at risk should be identifiable before ICI therapy. Here we propose to focus on T-cell subsets that interact with bacteria after inducing epithelial damage. Especially, intestinal resident immune cells are of interest. This may lead to a better understanding of IMC and provides opportunities for prevention and management.

Immune Checkpoint Inhibitor-Induced Colitis Presenting As Lymphocytic Colitis

Checkpoint inhibitors (CPIs) are a new class of drugs that have changed the treatment and prognosis of several malignancies, even in their advanced stages. These drugs have increased patient survival rates. CPIs stimulate the immune system and include cytotoxic T-lymphocyte antigen-4 inhibitors (ipilimumab), programmed cell death inhibitors such as pembrolizumab, nivolumab, and avelumab, and programmed cell death protein ligand-1 inhibitors such as atezolizumab. Herein, we present a case of CPI-induced colitis in a 45-year-old woman with a history of melanoma. The melanoma was BRAF-positive with a V600 mutation. She had metastasis to the brain and the right 10th rib, which underwent surgery and radiation treatment, respectively. She was treated with nivolumab and denosumab. The patient presented with chronic watery diarrhea. Biopsy revealed lymphocytic colitis-like changes in the colon and terminal ileum. Thus, given the history of CPIs, a diagnosis of CPIS-induced colitis was made.

Patients With Microscopic Colitis Have Altered Levels of Inhibitory and Stimulatory Biomarkers in Colon Biopsies and Sera Compared to Non-inflamed Controls

Introduction: Microscopic colitis (MC) is an inflammatory bowel condition with two subtypes, lymphocytic colitis (LC) and collagenous colitis (CC). Unlike patients with ulcerative colitis (UC) and non-inflamed individuals, MC patients have reduced risk of developing colorectal cancer, possibly due to increased immune surveillance in MC patients. Aim: To examine differences in levels of immunomodulatory molecules, including those involved in immune checkpoint mechanisms, in sera from patients with MC and in colonic biopsies from patients with MC and UC compared with controls. Methods: Using Luminex, 23 analytes (4-1BB, 4-1BBL, APRIL, BAFF, BTLA, CD27, CD28, CD80, CTLA-4, E-cadherin, Galectin-3, GITR, HVEM, IDO, IL-2Rα, LAG-3, MICA, MICB, PD-1, PD-L1, PD-L2, sCD40L and TIM-3) were studied in serum from patients with active MC (n = 35) and controls (n = 23), and in colonic biopsies from patients with active LC (n = 9), active CC (n = 16) and MC in histological remission (LC n = 6, CC n = 6), active UC (n = 15) and UC in remission (n = 12) and controls (n = 58). Results: In serum, IDO, PD-1, TIM-3, 4-1BB, CD27, and CD80 were decreased whereas 4-1BBL and IL-2Rα were increased in MC patients compared with controls. In contrast, in biopsies, levels of PD-L2 and 4-1BB were increased in MC and UC patients with active disease. Furthermore, in biopsies from CC and UC but not LC patients with active disease, CTLA-4, PD-1, APRIL, BAFF, and IL-2Rα were increased compared with controls. PD-L1 was increased in CC but not UC or LC patients. CD27 and TIM-3 were decreased in biopsies from MC patients in comparison to controls whereas levels of MICB were decreased in patients with active UC compared with controls. Conclusions: Compared with non-inflamed controls, levels of soluble and membrane-bound immunomodulatory molecules were systemically and locally altered in MC and UC patients, with most analytes being decreased in serum but enhanced in colonic biopsies. These findings contribute to knowledge about checkpoint molecules and their role as biomarkers in MC and may also contribute to knowledge about possible mechanisms behind the seemingly protective effects of MC against colorectal cancer.

Metachronous Esophageal Ulcers after Immune-mediated Colitis Due to Immune Checkpoint Inhibitor Therapy: A Case Report and Literature Review

Although cases of gastrointestinal toxicity of pembrolizumab have been reported, cases of acute immune-mediated colitis accompanied with metachronous esophageal disorders (esophagitis and ulcer) are rare. We herein report a case of acute colitis and metachronous esophageal ulcers due to an immune-related adverse event following concomitant pembrolizumab chemotherapy for lung adenocarcinoma. To our knowledge, there have so far been no reports of cases in which both acute immune-mediated colitis and metachronous esophageal ulcers developed. We therefore report the details of this case along with a review of the pertinent literature.

Immune checkpoint inhibitor treatment induces colitis with heavy infiltration of CD8 + T cells and an infiltration pattern that resembles ulcerative colitis

Colitis is a common, but poorly understood, adverse event of immune checkpoint inhibitors that are standard-of-care for an expanding range of cancer types. This explorative study aimed to describe the immune infiltrates in the colon from individuals developing checkpoint inhibitor colitis and compare them to well-known immunophenotypes of acute graft-versus-host disease, ulcerative colitis, and Crohn’s disease. Colon biopsies (n = 20 per group) of patients with checkpoint inhibitor colitis, acute graft-versus-host disease, ulcerative colitis and Crohn’s disease, all colitis treatment-naïve, and of individuals with a normal colon were analyzed using immunohistochemistry: CD8 for cytotoxic T cells, CD4 for T helper cells, and CD68 to identify cells of macrophage lineage. CD8 + T cell, CD4 + T cell, and CD68 + cell counts were performed. Cell infiltration was scored as scattered/patchy or band-like in the superficial and deep gut mucosa. Checkpoint inhibitor colitis was found to be heavily infiltrated by CD8 + T cells. Comparative analysis between groups showed that both CD8 + T cell counts (P < 0.01) and immune cell infiltration patterns in checkpoint inhibitor colitis were most similar to those observed in ulcerative colitis, with a deep band-like CD4 + T cell infiltration pattern and a superficial band-like CD68 + cell infiltration pattern in both. In conclusion, this is the first immunohistopathological study comparing infiltrate characteristics of checkpoint inhibitor colitis, acute graft-versus-host disease, ulcerative colitis, and Crohn’s disease. Checkpoint inhibitor colitis samples are heterogeneous, heavily infiltrated by CD8 + T cells, and show an immune cell infiltration pattern that is more similar to ulcerative colitis than to colonic acute graft-versus-host disease or colonic Crohn’s disease.

CD4+ T cells are essential for the development of destructive thyroiditis induced by anti-PD-1 antibody in thyroglobulin-immunized mice

Immune-related adverse events induced by anti-programmed cell death-1 antibodies (PD-1-Ab), including destructive thyroiditis (thyroid-irAE), are thought to be caused by activated T cells. However, the T cell subsets that are directly responsible for damaging self-organs remain unclear. To clarify which T cell subsets are involved in the development of thyroid-irAE, a mouse model of thyroid-irAE was analyzed. PD-1-Ab administration 2.5 months after immunization with thyroglobulin caused destructive thyroiditis. Thyroiditis was completely prevented by previous depletion of CD4⁺ T cells and partially prevented by depleting CD8⁺ T cells. The frequencies of central and effector memory CD4⁺ T cell subsets and the secretion of interferon-γ after stimulation with thyroglobulin were increased in the cervical lymph nodes of mice with thyroid-irAE compared with controls. Histopathological analysis revealed infiltration of CD4⁺ T cells expressing granzyme B in thyroid glands and major histocompatibility complex class II expression on thyrocytes in mice with thyroid-irAE. Adoptive transfer of CD4⁺ T cells from cervical lymph nodes in mice with thyroid-irAE caused destruction of thyroid follicular architecture in the irradiated recipient mice. Flow cytometric analyses showed that the frequencies of central and effector memory CD4⁺ T cells expressing the cytotoxic marker CD27 were higher in peripheral blood mononuclear cells collected from patients with thyroid-irAE induced by PD-1-Ab versus those without. These data suggest a critical role for cytotoxic memory CD4⁺ T cells activated by PD-1-Ab in the pathogenesis of thyroid-irAE.

Not-so-opposite ends of the spectrum: CD8+ T cell dysfunction across chronic infection, cancer and autoimmunity

CD8⁺ T cells are critical mediators of cytotoxic effector function in infection, cancer and autoimmunity. In cancer and chronic viral infection, CD8⁺ T cells undergo a progressive loss of cytokine production and cytotoxicity, a state termed T cell exhaustion. In autoimmunity, autoreactive CD8⁺ T cells retain the capacity to effectively mediate the destruction of host tissues. Although the clinical outcome differs in each context, CD8⁺ T cells are chronically exposed to antigen in all three. These chronically stimulated CD8⁺ T cells share some common phenotypic features, as well as transcriptional and epigenetic programming, across disease contexts. A better understanding of these CD8⁺ T cell states may reveal novel strategies to augment clearance of chronic viral infection and cancer and to mitigate self-reactivity leading to tissue damage in autoimmunity.

A case of immune checkpoint inhibitor-related colitis with a distinctive endoscopic finding of colonic pseudolipomatosis

A man in his 70s received anticancer chemotherapy with the anti-programmed cell death protein-ligand 1 antibody atezolizumab for non-small cell lung cancer. Ten days later, he developed diarrhea and skin rash, which were suspected to be due to immune-related adverse events, and was treated with prednisolone for 2 weeks. Five weeks after atezolizumab administration, he was admitted to our hospital for Common Terminology Criteria for Adverse Events Grade 3 diarrhea and hematochezia. Sigmoidoscopy revealed a dark red color in the mucosa of the transverse colon and multiple whitish mucosal plaques extending from the transverse colon to the rectum. Biopsy specimens revealed empty vacuoles in the lamina propria with infiltration of numerous inflammatory cells, including CD8⁺ T cells. Based on the findings of sigmoidoscopy and histology, the diagnosis was immune checkpoint inhibitor-related colitis with colonic pseudolipomatosis. The endoscopic findings and symptoms were markedly improved by prednisolone administration. We herein report the first case of immune checkpoint inhibitor-related colitis with characteristic endoscopic findings of colonic pseudolipomatosis. It is important to perform endoscopy and histological evaluation to determine the differential diagnosis and treatment strategy for patients treated with immune checkpoint inhibitors.

Society for Immunotherapy of Cancer (SITC) clinical practice guideline on immune checkpoint inhibitor-related adverse events

Immune checkpoint inhibitors (ICIs) are the standard of care for the treatment of several cancers. While these immunotherapies have improved patient outcomes in many clinical settings, they bring accompanying risks of toxicity, specifically immune-related adverse events (irAEs). There is a need for clear, effective guidelines for the management of irAEs during ICI treatment, motivating the Society for Immunotherapy of Cancer (SITC) to convene an expert panel to develop a clinical practice guideline. The panel discussed the recognition and management of single and combination ICI irAEs and ultimately developed evidence- and consensus-based recommendations to assist medical professionals in clinical decision-making and to improve outcomes for patients.

Distribution of mucosal PD-1 expressing T cells in patients with colitis of different etiologies

BACKGROUND

Immunotherapy, targeting programmed death-1 (PD-1) enhances antitumor T-cell activity in patients with malignancies. Blocking PD-1 or its ligand may lead to fulminant colitis as serious adverse event in these patients. Since little is known of the presence and role of PD-1⁺T cells in colitis of different etiologies, we determined PD-1⁺T cells in mucosal specimens of patients with inflammatory bowel disease, infectious colitis (InfC), immunotherapy-related colitis (ImC) and healthy controls (HC).

METHODS

Newly diagnosed patients with ulcerative colitis (UC, n = 73), Crohn's disease (CD, n = 50), InfC (n = 5), ImC (n = 8) and HC (n = 8) were included. Baseline inflamed colonic biopsies were studied with immunohistochemistry and flowcytometry.

RESULTS

Using immunohistochemistry, PD-1 was not present on lymphocytes in the epithelium of all patients, nor in HC. The percentage PD-1⁺ of all lymphocytes in the lamina propria was 40% in UC, 5% in InfC, 3% in ImC and 0% in HC. Flowcytometry showed significant higher percentages of PD-1⁺T cells in inflamed biopsy specimens of UC patients (22%) compared to all other groups: CD patients (13%), InfC (12%), ImC (5%) and HC (6%).

CONCLUSION

There are relevant differences in distribution and frequencies of mucosal PD-1⁺ T-cell subsets in patients with UC, CD, InfC and ImC, supporting the hypothesis that these types of colitis are driven by different immunological pathways. The increased numbers of PD-1⁺ and PD-L1⁺ lymphocytes in the colonic mucosa of UC patients suggest that the PD-1/PD-L1 pathway might be more activated in UC than in CD.

Granulomatous colitis in a patient with metastatic melanoma under immunotherapy: a case report and literature review

BACKGROUND

Immune checkpoint inhibitors (ICPIs) have changed the way advanced malignancies are currently confronted, improving cancer patients' outcomes but also generating distinct immune-related (ir) adverse events. ICPIs-induced colitis is a common complication showing different clinical and histological manifestations. In the literature review, 14 cases with ICPIs related colon granulomas have been reported in 5 studies with either limited or unavailable information regarding histology. Granulomatous reactions can be mistakenly perceived as disease recurrence or progression. Better understanding and identification of this infrequent histological display can help to avoid misdiagnosis and mismanagement.

CASE PRESENTATION

A 63-year-old female patient with metastatic melanoma was admitted to the hospital with symptoms of nausea, persistent diarrhea and shivering fever under consecutive treatments with ICPIs, initially pembrolizumab and subsequently ipilimumab. Sigmoidoscopy was performed revealing mucosal edema, hyperemia and erosions of the rectum and sigmoid colon. Histological evaluation of sigmoid colon mucosa biopsies revealed an unusual colitis pattern characterized by multiple intracryptal granulomas attributed to ICPIs therapy. Steroids were administered and the patient recovered. ICPIs treatment was discontinued. The patient was subsequently treated with chemotherapy but follow up radiology showed disease progression. A re-challenge with another ICPI regimen was decided and the patient is currently under immunotherapy with stable disease regarding melanoma status and without any sign of colitis recurrence.

CONCLUSIONS

The present report provides detailed histological description of a distinctive ICPIs-induced granulomatous colitis and highlights the need for awareness of the distinct adverse events and reaction patterns in the context of immunotherapy.

Gastrointestinal disorders as immune-related adverse events

Immune checkpoint inhibitors, such as cytotoxic T-lymphocyte antigen 4 inhibitors, programmed cell death 1 inhibitors and programmed cell death-ligand 1 inhibitors, have recently emerged as novel drugs in the anti-cancer therapy. Their use in different types of advanced cancer has shown good results and an increase in survival rates. However, immune-related adverse events (irAEs) are frequent and often require special care. IrAEs may affect all the organs, but they are most commonly seen in skin, lungs, endocrine glands and in the gastrointestinal tract where small bowel, colon, the liver and/or the pancreas can be involved. Despite being usually mild and self-resolving, irAEs may present in severe and life-threatening forms, causing the withdrawal of anti-cancer therapy. IrAEs, therefore, represent a challenging condition to manage that often requires the cooperation between the oncologists and the gastroenterologists in order to identify and treat them adequately.