Myeloid-derived suppressor cells (MDSC) accumulate in the spleen and tumor bed during tumor growth. They contribute to the immune tolerance of cancer notably by inhibiting the function of CD8 (+) T cells. Thus, their elimination may hamper tumor growth by enhancing antitumor T-cell functions. We have previously reported that some anticancer agents relied on T cell-dependent anticancer responses to achieve maximal efficacy. However, the effect of anticancer agents on MDSC has remained largely unexplored. In this study, we observed that gemcitabine and 5-fluorouracil (5FU) were selectively cytotoxic on MDSC. In vivo, the treatment of tumor-bearing mice with 5FU led to a major decrease in the number of MDSC in the spleens and tumor beds of animals whereas no significant effect on T cells, natural killer cells, dendritic cells, or B cells was noted. Interestingly, 5FU showed a stronger efficacy over gemcitabine to deplete MDSC and selectively induced MDSC apoptotic cell death in vitro and in vivo. The elimination of MDSC by 5FU increased IFN-γ production by tumor-specific CD8(+) T cells infiltrating the tumor and promoted T cell-dependent antitumor responses in vivo. Altogether, these findings suggest that the antitumor effect of 5FU is mediated, at least in part, by its selective cytotoxic action on MDSC. Cancer Res; 70(8); 3052-61. ©2010 AACR.

Myeloid-derived suppressor cells (MDSCs) have been identified in humans and mice as a population of immature myeloid cells with the ability to suppress T cell activation. They accumulate in tumor-bearing mice and humans and have been shown to contribute to cancer development. Here, we have isolated tumor-derived exosomes (TDEs) from mouse cell lines and shown that an interaction between TDE-associated Hsp72 and MDSCs determines the suppressive activity of the MDSCs via activation of Stat3. In addition, tumor-derived soluble factors triggered MDSC expansion via activation of Erk. TDE-associated Hsp72 triggered Stat3 activation in MDSCs in a TLR2/MyD88-dependent manner through autocrine production of IL-6. Importantly, decreasing exosome production using dimethyl amiloride enhanced the in vivo antitumor efficacy of the chemotherapeutic drug cyclophosphamide in 3 different mouse tumor models. We also demonstrated that this mechanism is relevant in cancer patients, as TDEs from a human tumor cell line activated human MDSCs and triggered their suppressive function in an Hsp72/TLR2-dependent manner. Further, MDSCs from cancer patients treated with amiloride, a drug used to treat high blood pressure that also inhibits exosome formation, exhibited reduced suppressor functions. Collectively, our findings show in both mice and humans that Hsp72 expressed at the surface of TDEs restrains tumor immune surveillance by promoting MDSC suppressive functions.

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Although Th17 cells are known to promote tissue inflammation and autoimmunity, their role during cancer progression remains elusive. Here, we showed that in vitro Th17 cells generated with the cytokines IL-6 and TGF-β expressed CD39 and CD73 ectonucleotidases, leading to adenosine release and the subsequent suppression of CD4(+) and CD8(+) T cell effector functions. The IL-6-mediated activation of the transcription factor Stat3 and the TGF-β-driven downregulation of Gfi-1 transcription factor were both essential for the expression of ectonucleotidases during Th17 cell differentiation. Stat3 supported whereas Gfi-1 repressed CD39 and CD73 expression by binding to their promoters. Accordingly, Th17 cells differentiated with IL-1β, IL-6, and IL-23 but without TGF-β did not express ectonucleotidases and were not immunosuppressive. Finally, adoptive transfer of Th17 cells induced by TGF-β and IL-6 promoted tumor growth in a CD39-dependent manner. Thus, ectonucleotidase expression supports the immunosuppressive fate of Th17 cells in cancer.

In this multi-institutional cohort, the incidence of AE is higher among interventional compared to diagnostic cases, and is very low among biopsy cases. Equitable comparisons among institutions will require the development and application of risk adjustment methods.

These authors equally contributed to this work.yy These authors jointly supervised this work. Keywords: B cells, gastric cancer, histology, human tumors, prognosis, T-betAbbreviations: APC, antigen presenting cell; DC, dendritic cell; NK, natural killer; OS, overall survival; RFS, relapse-free survival; Th1, T helper type 1; TLS, tertiary lymphoid structures; Treg, regulatory T cell.Tumor-infiltrating T and B lymphocytes could have the potential to affect cancer prognosis. The objective of this study was to investigate the prognostic significance of tumor infiltration by CD8 and CD4 T cells, and B lymphocytes in patients with localized gastric cancer. In a retrospective cohort of 82 patients with localized gastric cancer and treated by surgery we quantitatively assessed by immunohistochemistry on surgical specimen, immune infiltrates of IL-17 C , CD8 C , Foxp3 C , Tbet C T cells and CD20 C B cells both in the tumor core and at the invasive margin via immunohistochemical analyses of surgical specimens. We observed that CD8 C and IL17 C T-cell densities were not significantly associated with gastric cancer prognosis. In contrast, high infiltration of Tbet C T cells, high numbers of CD20 C B-cell follicles, and low infiltration of Foxp3 C T cells, were associated with better relapse-free survival. Interestingly, treatment with neoadjuvant chemotherapy or histological tumor type (diffuse versus intestinal) did not influence type and density of immune infiltrates or their prognostic value. Immunohistochemical analysis of the gastric cancer stromal microenvironment revealed organized T and B cell aggregates, with strong structural analogies to normal secondary lymphoid organs and which could be considered as tertiary lymphoid structures. Using transcriptomic data from an independent cohort of 365 localized gastric cancer, we confirmed that a coordinated Th1, and B cell stromal gene signature is associated with better outcome. Altogether, these data suggest that tumor infiltration by B and Th1 T cells could affect gastric cancer prognosis and may be used to better define the outcome of patients with localized gastric cancer.

Background— The Congenital Cardiac Catheterization Project on Outcomes (C3PO) was established to develop outcome assessment methods for pediatric catheterization. Methods and Results— Six sites have been recording demographic, procedural and immediate outcome data on all cases, using a web-based system since February 2007. A sample of data was independently audited for validity and data completeness. In 2006, participants categorized 84 procedure types into 6 categories by anticipated risk of an adverse event (AE). Consensus and empirical methods were used to determine final procedure risk categories, based on the outcomes: any AE (level 1 to 5); AE level 3, 4, or 5; and death or life-threatening event (level 4 or 5). The final models were then evaluated for validity in a prospectively collected data set between May 2008 and December 31, 2009. Between February 2007 and April 2008, 3756 cases were recorded, 558 (14.9%) with any AE; 226 (6.0%) level 3, 4, or 5; and 73 (1.9%) level 4 or 5. General estimating equations models using 6 consensus-based risk categories were moderately predictive of AE occurrence (c-statistics: 0.644, 0.664, and 0.707). The participant panel made adjustments based on the collected empirical data supported by clinical judgment. These decisions yielded 4 procedure risk categories; the final models had improved discrimination, with c-statistics of 0.699, 0.725, and 0.765. Similar discrimination was observed in the performance data set (n=7043), with c-statistics of 0.672, 0.708, and 0.721. Conclusions— Procedure-type risk categories are associated with different complication rates in our data set and could be an important variable in risk adjustment models for pediatric catheterization.

Using CHARM (Catheterization for Congenital Heart Disease Adjustment for Risk Method) to adjust for case mix complexity should allow comparisons of AE among institutions performing catheterization for congenital heart disease.