The immune system and gastrointestinal stromal tumor: a wealth of opportunities.

PURPOSE OF REVIEW: This article reviews the current literature on tumor-infiltrating immune cells in gastrointestinal stromal tumor (GIST), and the current status and prospects of effective immunotherapeutic strategies.

RECENT FINDINGS: Tumor-infiltrating immune cells populate the microenvironment of GISTs; the most numerous are tumor-associated macrophages (TAMs) and CD3 T cells. TAMs have not been shown to have a relationship with the biological behavior of GISTs; however, the number of CD3 T cells correlates with better outcomes. The prognostic significance of tumor-infiltrating neutrophils, natural killer cells, CD4 T cells, CD8 T cells, and Treg cells remains unknown.Imatinib mesylate achieves a clinical response in 80% of patients with GIST. Its antitumor mechanism is partially immune mediated. The combination of imatinib and interferon-α has been shown to be effective against GIST - it eradicates tumor cells including those that are drug resistant. Preclinical trials including cytotoxic T lymphocyte-associated antigen 4 blockade, anti-KIT antibody, and the generation of designer T cells have shown promising therapeutic effect in animal models of GIST.

SUMMARY: GIST contains many tumor-infiltrating immune cells and should be susceptible to immunotherapy; early clinical and preclinical trials have shown promising results that should lead to new investigations and effective forms of direct and synergistic therapies.