Unraveling Resistance to Immunotherapy in MSI-High Colorectal Cancer.

Colorectal cancer (CRC) is the third most common cancer and the second leading cause of cancer-related deaths. Incidences of early CRC cases are increasing annually in high-income countries, necessitating effective treatment strategies. Immune checkpoint inhibitors (ICIs) have shown significant clinical efficacy in various cancers, including CRC. However, their effectiveness in CRC is limited to patients with mismatch-repair-deficient (dMMR)/microsatellite instability high (MSI-H) disease, which accounts for about 15% of all localized CRC cases and only 3% to 5% of metastatic CRC cases. However, the varied response among patients, with some showing resistance or primary tumor progression, highlights the need for a deeper understanding of the underlying mechanisms. Elements involved in shaping the response to ICIs, such as tumor microenvironment, immune cells, genetic changes, and the influence of gut microbiota, are not fully understood thus far. This review aims to explore potential resistance or immune-evasion mechanisms to ICIs in dMMR/MSI-H CRC and the cell types involved, as well as possible pitfalls in the diagnosis of this particular subtype.

[Correlation between chronic idiopathic urticaria and infection due to H. pylori]. / Correlación entre urticaria crónica idiopática e infección por H. pylori.

BACKGROUND: H. pylori is considered one of the major etiological agents for chronic idiopathic urticaria; it infects 15 percent of the world's population and induces an inflammatory process in the gastric mucosa. In some cases it is related to chronic urticaria, even in the absence of digestive symptoms. OBJECTIVE: The purpose of this study is to find the correlation between chronic idiopathic urticaria and infection due to Helicobacter pylori. PATIENTS AND METHODS: Twenty patients with chronic idiopathic urticaria and a positive urea breath test for H. pylori were included in the study. All other frequent pathologies were eliminated. Patients began treatment with amoxicillin, clarithromycin and omeprazole for 14 days. Thirty days after the start of treatment, the urea breath test was performed in all of the patients. Also cutaneous symptoms were evaluated. RESULTS: Urticaria disappeared in 11 patients (55%), in 9 (45%) the urea breath test became negative and in two remained positive. Urticaria persisted in 9 patients (45%), in 6 (30%) the urea breath test was negative and in 3 (15%) persisted as positive. Only two patients (10%) experienced gastric symptoms. CONCLUSION: We found a correlation between the disappearance of the symptoms and a negative urea breath test in 45 percent of the patients who were studied. We must consider the possibility of H. pylori infection, which can be present even without gastric symptoms.