Cancer immunotherapy: the role regulatory T cells play and what can be done to overcome their inhibitory effects.

Since multiple lines of experimental and clinical data clearly identified regulatory T cells as an integral part of the immune response, these cells have become a major focus of investigation in tumor immunology. Regulatory T cells are in place to dampen ongoing immune responses and to prevent autoimmunity, but they also have profound effects in blocking therapeutic anti-tumor activity. Therefore regulatory T cells are seen as a major hurdle that must be overcome in order for cancer immunotherapy to reach its therapeutic potential. Regulatory T cells are heterogeneous with sub-populations that exhibit distinct functional features. Here we will review the individual sub-populations in regards to their mode of action and their potential impact on blocking anti-tumor immunity. Approaches to measure function and frequency of regulatory T cells in model systems and clinical trails will be discussed. Finally, we will describe possible ways to interfere with regulatory T cell-mediated immune suppression with the focus on recent pre-clinical and clinical findings.

Helicobacter pylori as a prognostic indicator after curative resection of gastric carcinoma: a prospective study.

BACKGROUND: The effect of Helicobacter-pylori status on survival after curative resection for gastric adenocarcinoma is unknown. We aimed to follow-up patients who were positive or negative for infection with H pylori who had curative (ie, R0) resection for gastric adenocarcinoma to assess differences in relapse-free survival and overall survival. METHODS: Before surgery, we assessed the H pylori status of 166 patients who had R0 resection for gastric adenocarcinoma between 1992 and 2002 with bacterial culture, histological analyses (ie, staining with haematoxylin and eosin and with Warthin-Starry), and serological analyses. FINDINGS: At a median follow-up of 53.0 months (range 1-146), relapse-free survival was 56.7 months (95% CI 4.7-108.7) and overall survival was 61.9 months (13.0-110.9) in patients positive for H pylori, compared with 19.2 months (12.7-25.6) and 19.2 months (7.1-31.3), respectively, in patients negative for H pylori (p=0.0009 for difference in relapse-free survival between groups, and p=0.0017 for difference in overall survival between groups). In multivariate analyses, H pylori was an independent prognostic factor for relapse-free survival (hazard ratio 2.16 [95% CI 1.33-3.49]) and overall survival (2.00 [1.22-3.27]). Depth of tumour invasion (2.60 [1.66-4.08]), lymph-node metastasis (2.11 [1.25-3.57]), and patient age 67.5 years or older (1.75 [1.11-2.75]) were also independent prognostic factors for overall survival. INTERPRETATION: Tumour-specific immune responses might be downregulated in patients who are negative for H pylori, and these patients should be followed up carefully because of a poor outlook.

TNF plays an essential role in tumor regression after adoptive transfer of perforin/IFN-gamma double knockout effector T cells.

We have recently shown that effector T cells (T(E)) lacking either perforin or IFN-gamma are highly effective mediators of tumor regression. To rule out compensation by either mechanism, T(E) deficient in both perforin and IFN-gamma (perforin knockout (PKO)/IFN-gamma knockout (GKO)) were generated. The adoptive transfer of PKO/GKO T(E) mediated complete tumor regression and cured wild-type animals with established pulmonary metastases of the B16BL6-D5 (D5) melanoma cell line. PKO/GKO T(E) also mediated tumor regression in D5 tumor-bearing PKO, GKO, or PKO/GKO recipients, although in PKO/GKO recipients efficacy was reduced. PKO/GKO T(E) exhibited tumor-specific TNF-alpha production and cytotoxicity in a 24-h assay, which was blocked by the soluble TNFRII-human IgG fusion protein (TNFRII:Fc). Blocking TNF in vivo by administering soluble TNFR II fusion protein (TNFRII:Fc) significantly reduced the therapeutic efficacy of PKO/GKO, but not wild-type T(E). This study identifies perforin, IFN-gamma, and TNF as a critical triad of effector molecules that characterize therapeutic antitumor T cells. These insights could be used to monitor and potentially tune the immune response to cancer vaccines.