Armelle Bardier

Identification of CD8+CD25+Foxp3+ suppressive T cells in colorectal cancer tissue

Background: The antitumoral immune response is one determinant of colorectal cancer (CRC) outcome. Recent work suggests that Foxp3+CD25+CD4+ regulatory T cells (T4reg) might hamper effective immunosurveillance of emerging cancer cells and impede effective immune responses to established tumours. In this descriptive study, we analysed blood and tissue regulatory T cell populations in patients with CRC. Methods: Blood and tissue regulatory Foxp3+ T cells from 40 patients with CRC were compared to regulatory Foxp3+ T cells from normal colonic tissue and from blood of 26 healthy volunteers. Flow cytometry was used to quantify and phenotype all Foxp3+ T cell populations. Correlations were sought with the tumour stage and with micro-invasive status. The suppressive capacity of regulatory Foxp3+ T cells was assessed by their effect on CD4+CD25− T cell proliferation in vitro and by their capacity to inhibit cytokine production by conventional T cells. Results: We found a significant increase of CD8+CD25+Foxp3+ cells (T8reg) in blood and CRC tissue; their phenotype was close to that of T4reg. T8reg cells infiltrating CRC were activated, as suggested by increased cytoxic T lymphocyte-associated antigen-4, glucocorticoid-induced tumour necrosis factor-related protein, and transforming growth factor (TGF)β1 expression compared to T8reg from normal autologous colonic tissue. Moreover, T8reg were able to suppress CD4+CD25− T cell proliferation and Th1 cytokine production ex vivo, demonstrating that tumour-infiltrating T8reg have strong suppressive capacities. T8reg numbers correlated with the tumour stage and with micro-invasive status. Finally, interleukin 6 and TGFβ1 synergistically induced the generation of CD8+CD25+Foxp3+ T cells ex vivo. Conclusions: We have identified a new regulatory T cell population (CD8+Foxp3+) in colorectal tumours. After isolation from cancer tissue these CD8+Foxp3+ cells demonstrated strong immunosuppressive properties in vitro. These data suggest that these cells may contribute to tumoral immune escape and disease progression.

Measurement of Indoleamine 2, 3 Dioxygenase Activity in Colorectal Cancer: A Controlled Group Study

Background: Indoleamine 2,3-dioxygenase (IDO), the rate-limiting enzyme that converts tryptophan (Trp) to kynurenine (Kyn), suppresses antitumor immune responses via depletion of Trp and accumulation of Kyn. We hypothesized that, in colorectal cancer (CRC), IDO activity may serve as a biomarker and thus we compared the IDO activity between patients with CRC and those without CRC. We further assessed the effect of surgical treatment of CRC on IDO activity.Methods: Serum concentrations of Trp and Kyn were measured by high performance liquid chromatography in the sera of 68 patients with CRC (CRC group) and 38 without CRC (Control group) prior surgery (D0) and 7 days after surgery (D7). The IDO activity was estimated by the serum Kyn-to-Trp ratio (Kyn/Trp ratio).Results: At Day 0, serum Kyn concentration was higher in the CRC group than in Control group (1.7 [1.4;2.1] μM vs 1.25 [0.9;1.78] μM, respectively; p=0.004) while no difference in serum concentration of Trp was observed between the two groups. Kyn/Trp ratio (IDO activity) was significantly higher in the CRC group than in Control group. At Day 7 serum concentrations of Trp, Kyn and the Kyn/Trp ratio were not statistically different between the two groups.Conclusion: This study indicates that IDO activity is higher in patients with CRC compared with those without CRC. Surgical treatment impacts the IDO activity with a similar Kyn/Trp ratio in both groups. This study is the first step to larger studies to establish the Kyn/Trp ratio as a reliable serum marker of CRC.

Cancer colique asymptomatique avec métastases hépatiques synchrones non résécables : faut-il réséquer le primitif ?

Au moment du diagnostic, 25 % des patients avec un cancer colorectal ont des metastases synchrones, principalement hepatiques. Dans la majorite des cas, les metastases sont jugees non resecables et le traitement repose sur la chimiotherapie associee a une biotherapie. Chez ces patients, lorsque la tumeur colique est a- ou pauci-symptomatique, l’interet de la colectomie premiere avant de mettre en route le traitement reste controverse. Aucune etude prospective randomisee ne permet de repondre a cette question. Le but de ce travail est de faire le point sur les donnees disponibles dans la litterature pour guider le choix du traitement de premiere intention (colectomie oui vs non) chez un patient porteur d’un cancer colique metastatique avec des metastases synchrones non resecables en se focalisant sur trois elements de discussion : le risque de complications de la tumeur primitive sous chimiotherapie, la morbidite de la colectomie prophylactique en situation metastasique et l’impact de la strategie sur la survie.