Assessment of cancer cell-expressed HLA class I molecules and their immunopathological implications.

Immunotherapy using immune checkpoint inhibitors (ICIs) has shown superior efficacy compared with conventional chemotherapy in certain cancer types, establishing immunotherapy as the fourth standard treatment alongside surgical intervention, chemotherapy, and radiotherapy. In cancer immunotherapy employing ICIs, CD8-positive cytotoxic T lymphocytes are recognized as the primary effector cells. For effective clinical outcomes, it is essential that the targeted cancer cells express HLA class I molecules to present antigenic peptides derived from the tumor. However, cancer cells utilize various mechanisms to downregulate or lose HLA class I molecules from their surface, resulting in evasion from immune surveillance. Correlations between prognosis and the integrity of HLA class I molecules expressed by cancer cells have been consistently found across different types of cancer. This paper provides an overview of the regulatory mechanisms of HLA class I molecules and their role in cancer immunotherapy, with a particular emphasis on the significance of utilizing pathological tissues to evaluate HLA class I molecules expressed in cancer cells.

[A case of Crohn's disease complicated by Guillain-Barrè syndrome during ustekinumab therapy].

We herein report a case involving a 23-year-old male patient with active Crohn's disease complicated by Guillain-Barrè syndrome during ustekinumab therapy. At age 11, the patient developed an anal fistula and was found to have multiple aphthae on the rectosigmoid colon, for which he was diagnosed with Crohn's disease. At age 12, he underwent gastrojejunal anastomosis for pyrolic stenosis. At age 20, a longitudinal ulcer was found on the ascending colon, and at age 21, aphthae were found on the stomach and efferent jejunum. At age 22, adalimumab was started, but the patient noted abdominal pain and diarrhea 4 months later. Hence, adalimumab was switched to ustekinumab (2017 June). Though ustekinumab was effective, the patient noted anorexia, weakness, and bilateral lower extremity numbness 1 year later (2018 June) and was admitted to the hospital. He was then diagnosed with Guillain-Barrè syndrome after spinal tap, neurological, and hematological examinations. Immunoglobulin therapy was provided but was less effective. The patient has since been receiving physical therapy. This has been the first report regarding Guillain-Barrè syndrome as a complication during ustekinumab therapy.