Pathology of immune checkpoint inhibitor-induced injury of the gastrointestinal tract and hepatobiliary system

Histopathologic Features of Unmasked Inflammatory Bowel Disease Following Immune Checkpoint Inhibitor Therapy in Colon Biopsies

Background and Aims

Typical immune checkpoint inhibitor-induced colitis (T-ICI) has significant histomorphologic overlap with inflammatory bowel disease (IBD), a distinction further complicated in ICI-treated patients with pre-existing inflammatory bowel disease (P-IBD) and those with potentially "unmasked" inflammatory bowel disease (U-IBD) after ICI therapy. This study describes histopathologic findings seen in U-IBD colonic biopsies and assesses for distinguishing features from T-ICI and P-IBD biopsies.

Methods

Initial colon biopsies after symptom onset from 34 patients on ICI therapy were reviewed, and histopathologic features were tabulated. U-IBD patients were identified clinically based on rapid toxicity development post-ICI treatment with multiple recurrences after immune suppression, frequently with regional colitis (versus pancolitis).

Results

The study cohort was classified into T-ICI (n = 20), P-IBD (n = 9), and U-IBD (n = 5) groups. The predominant histological patterns were diffuse active colitis (35%) in the T-ICI, and chronic active colitis in both the P-IBD (67%) and U-IBD (60%) groups (overall P = .003, P > .05 between the two IBD groups). None of the T-ICI biopsies demonstrated chronicity features (ie, architectural distortion score 2, basal lymphoplasmacytosis, or Paneth cell metaplasia). Only U-IBD biopsies demonstrated basal lymphoplasmacytosis (60% vs 0% in T-ICI/P-IBD, P = .002). Among available follow-up biopsies, chronicity features were present in all (4/4) U-IBD patients, including those without chronicity seen in the initial biopsy, but none (0/7) of T-ICI patients.

Conclusion

These early results show that no definite features of chronicity were seen in colon biopsies from T-ICI patients, suggesting that the presence of those features may be a clue to U-IBD in patients without a known IBD diagnosis. Frequent basal lymphoplasmacytosis seen in U-IBD may support a recent onset of mucosal injury and early architectural remodeling.

Histological Features of Celiac-Disease-like Conditions Related to Immune Checkpoint Inhibitors Therapy: A Signal to Keep in Mind for Pathologists

Immune checkpoint inhibitors (ICIs) targeting cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), programmed cell death protein (PD-1), and its ligand PDL-1, are finding increasing application in the treatment of malignant neoplasms. The widespread clinical use of these drugs, however, resulted in the discovery of side effects. The occurrence of celiac disease (CD) after ICIs therapy has been reported in the literature, but its incidence remains unknown and the role of ICIs in its onset is not yet clear. In this review, we examine the published data on this topic in order to better understand and define this entity from a histological point of view. We performed an electronic literature search to identify original reports in which CD or pathological CD-like conditions were documented histologically in patients treated with ICIs. We identified ten papers. A total of twenty-five patients were included in these publications, eleven of them receiving a serologic and histological diagnosis of CD, and four a histological diagnosis of CD-like conditions, in which pathogenesis appears to be multifactorial. ICIs can cause a CD-like enteropathy and biopsies with clinical integration are crucial to diagnose this condition. CD rarely has been observed during treatment with ICIs and its morphological aspects are similar to ICIs-CD enteropathy. Moreover, the onset of ICIs-CD may have a distinct immune mechanism compared to classical CD. Thus, the pathologists must make a histological diagnosis of CD with caution and only in adequate clinical and serological context.

Immunosuppressive Nanoparticles for Management of Immune-Related Adverse Events in Liver

Immune checkpoint blockade (ICB) therapy has been considered as an effective way to boost immune cells to recognize and attack tumors. However, side effects known as immune-related adverse events (irAEs) should be carefully managed. Here, we engineer immunosuppressive nanoparticles by coating PD-L1 overexpressed mesenchymal stem cells (MSCs) plasma membrane on poly lactic-co-glycolic acid nanoparticles (MSC-PD-L1⁺ NPs) for managing and reducing irAEs induced by immune checkpoint inhibitors. The nanoparticles can enrich at liver site after intravenous administration. In the high dose of anti-PD-L1 mAb-induced irAEs clinically relevant mouse model, a low dose of MSC-PD-L1⁺ NPs (2 mg/kg) sufficiently rescues hepatitis by inactivating T cells and macrophages in the liver tissue. More intriguingly, due to the dose threshold for nanoparticles to the tumor site, we unexpectedly find that the injected NPs do not affect the efficiency of ICB therapy to inhibit solid tumor growth. Such a strategy shows potential for managing the various cancer immunotherapy associated irAEs in clinical applications.