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Mismatch repair deficiency (dMMR) is found in approximately 15% of non-metastatic colon cancers (CCs) and is characterized by a defective DNA mismatch repair system, resulting in hypermutated and highly immunogenic tumors. Although patients with dMMR CC have limited benefit from chemotherapy, these tumors have been shown to respond exceptionally well to neoadjuvant anti-PD-1 plus anti-CTLA-4, with high rates of pathologic responses. Here, based on data from melanoma studies, we postulated a high efficacy and favorable toxicity profile of anti-PD-1 plus anti-LAG-3. In the NICHE-3 study, a total of 59 patients with locally advanced dMMR CC were treated with two 4-weekly cycles of nivolumab (480 mg) plus relatlimab (480 mg) before surgery. Pathologic response was observed in 57 of 59 (97%; 95% confidence interval (CI): 88–100%) patients, meeting the primary endpoint. Responses included 54 (92%; 95% CI: 81–97%) major pathologic responses (≤10% residual viable tumor) and 40 (68%; 95% CI: 54–79%) pathologic complete responses. With a median follow-up of 8 months (range, 2–19), one patient had recurrence of disease. The treatment displayed an acceptable safety profile, with all-grade and grade 3–4 immune-related adverse events (irAEs) occurring in 80% and 10% of patients, respectively. The most common irAEs were infusion-related reactions (29%), thyroid dysfunction (22%) and fatigue (20%). In conclusion, our results show that neoadjuvant nivolumab/relatlimab induces high rates of pathologic responses and that further investigation of this treatment in larger studies is warranted. These data add to the body of evidence in support of neoadjuvant immunotherapy regimens in dMMR CC. ClinicalTrials.gov identifier: NCT03026140.

Celiac disease is a gluten-sensitive enteropathy that affects people of all ages worldwide. This disease has emerged as a major health-care problem, as advances in diagnostic and screening methods have revealed its global prevalence. Environmental factors such as gluten introduction at childhood, infectious agents and socioeconomic features, as well as the presence of HLA-DQ2 and/or HLA-DQ8 haplotypes or genetic variations in several non-HLA genes contribute to the development of celiac disease. Growing insight into the variable clinical and histopathological presentation features of this disease has opened new perspectives for future research. A strict life-long gluten-free diet is the only safe and efficient available treatment, yet it results in a social burden. Alternative treatment modalities focus on modification of dietary components, enzymatic degradation of gluten, inhibition of intestinal permeability and modulation of the immune response. A small group of patients with celiac disease (2–5%), however, fail to improve clinically and histologically upon elimination of dietary gluten. This complication is referred to as refractory celiac disease, and imposes a serious risk of developing a virtually lethal enteropathy-associated T-cell lymphoma.

Enteropathy-associated T-cell lymphoma, an often fatal complication of celiac disease, can result from expansion of aberrant intraepithelial lymphocytes in refractory celiac disease type II (RCD II). Aberrant intraepithelial lymphocytes and lymphoma cells are intracellularly CD3ϵ+ but lack expression of the T-cell receptor (TCR)–CD3 complex on the cell surface. It is unknown what causes the loss of TCR-CD3 expression. We report the isolation of a cell line from an RCD II patient with the characteristic phenotype of enteropathy-associated T-cell lymphoma. We demonstrate that in this cell line the TCR-α and -β chains as well as the CD3γ, CD3δ, CD3ϵ, and ζ-chains are present intracellularly and that assembly of the CD3γϵ, CD3δϵ, and ζζ-dimers is normal. However, dimerization of the TCR chains and proper assembly of the TCR-CD3 complex are defective. On introduction of exogenous TCR-β chains, but not of TCR-α chains, assembly and functional cell surface expression of the TCR-CD3 complex were restored. Defective synthesis of both TCR chains was found to underlie loss of TCR expression in similar cell lines isolated from 2 additional patients. (Pre)malignant transformation in RCD II thus correlates with defective synthesis or defective association of the TCR chains, resulting in loss of surface TCR-CD3 expression.

Autologous hematopoietic stem cell transplantation (ASCT) is an increasingly accepted treatment for refractory autoimmune diseases. Refractory celiac disease with aberrant T cells (RCD type II) is unresponsive to available therapies and carries a high risk of transition into enteropathy associated T-cell lymphoma (EATL). This study reports on the feasibility, safety, and efficacy of ASCT in patients with RCD type II. Thirteen patients with RCD type II were evaluated. Seven patients (4 men, 3 women, mean age 61.5 years [range, 51-69 years]) underwent transplantation. After conditioning with fludarabine and melphalan, ASCT was performed. Patients were monitored for response, adverse effects, and hematopoietic reconstitution. All 7 patients completed the mobilization and leukapheresis procedures successfully and subsequently underwent conditioning and transplantation. Engraftment occurred in all patients. No major nonhematologic toxicity or transplantation-related mortality was observed. There was a significant reduction in the aberrant T cells in duodenal biopsies associated with improvement in clinical well-being and normalization of hematologic and biochemical markers (mean follow-up, 15.5 months; range, 7-30 months). One patient died 8 months after transplantation from progressive neuroceliac disease. These preliminary results showed that high-dose chemotherapy followed by ASCT seems feasible and safe and might result in long-term improvement of patients with RCD type II whose condition did not respond promptly to available drugs.