BackgroundChemokines are involved in multiple aspects of pathogenesis and cellular trafficking in tumorigenesis. In this study, we report that the latest member of the C-X-C-type chemokines, CXCL17 (DMC/VCC-1), recruits immature myeloid-derived cells and enhances early tumor progression.Methodology/Principal FindingsCXCL17 was preferentially expressed in some aggressive types of gastrointestinal, breast, and lung cancer cells. CXCL17 expression did not impart NIH3T3 cells with oncogenic potential in vitro, but CXCL17-expressing NIH3T3 cells could form vasculature-rich tumors in immunodeficient mice. Our data showed that CXCL17-expressing tumor cells increased immature CD11b+Gr1+ myeloid-derived cells at tumor sites in mice and promoted CD31+ tumor angiogenesis. Extensive chemotactic assays proved that CXCL17-responding cells were CD11b+Gr1highF4/80− cells (∼90%) with a neutrophil-like morphology in vitro. Although CXCL17 expression could not increase the number of CD11b+Gr1+ cells in tumor-burdened SCID mice or promote metastases of low metastatic colon cancer cells, the existence of CXCL17-responding myeloid-derived cells caused a striking enhancement of xenograft tumor formation.Conclusions/SignificanceThese results suggest that aberrant expression of CXCL17 in tumor cells recruits immature myeloid-derived cells and promotes tumor progression through angiogenesis.

With melanoma, as with many other malignancies, aberrant transcriptional repression is a hallmark of refractory cancer. To restore gene expression, use of a histone deacetylase inhibitor (HDACi) is expected to be effective. Our recent DNA micro-array analysis showed that the HDACi depsipeptide (FK228) significantly enhances gp100 antigen expression. Herein, we demonstrate that depsipeptide promotes tumor-specific T-cell-mediated killing of B16/F10 murine melanoma cells. First, by a quantitative assay of caspase-3/7 activity, a sublethal dose of depsipeptide was determined (ED50: 5 nM), in which p21(Waf1/Cip1) and Fas were sufficiently evoked concomitantly with histone H3 acetylation. Second, the sublethal dose of depsipeptide treatment with either a recombinant Fas ligand or tumor-specific T cells synergistically enhanced apoptotic cell death in B16/F10 cells in vitro. Furthermore, we found that depsipeptide increased levels of perforin in T cells. Finally, in vivo metastatic growth of B16/F10 in the lung was significantly inhibited by a combination of depsipeptide treatment and immune cell adoptive transfer from immunized mice using irradiated B16 cells and gp100-specific (Pmel-1) TCR transgenic mice (P<0.05, vs cell transfer alone). Consequently, employment of a transcriptional modulation strategy using HDACis might prove to be a useful pretreatment for human melanoma immunotherapy.

Regulatory T cells (Tregs), a subset of CD4+ T cells plays a pivotal role in regulating the immune system. An increase in Treg numbers enables cancer progression by dampening the immune system and allowing tumor cells to evade immune detection and destruction. An increase in Treg numbers and expression of inhibitory cytokines including TGF-β and IL-10 are mechanisms by which Tregs exert their immune suppressive function. However, the presence of Tregs and inhibitory cytokines in oral cancer patients is still unclear. In this study, the presence of circulating Tregs in 39 oral cancer patients and 24 healthy donors was examined by studying the presence of the CD4+CD25hiCD127low cell population in their peripheral blood mononuclear cells using flow cytometry. Serum levels of TGF-β and IL-10 were measured by ELISA. T cell subsets of OSCC patients were found to differ significantly from healthy donors where a decrease in CD8+ cytotoxic T cells and an increase in Tregs (CD4+CD25hiCD127low) were observed. Further, the ratio of CD8+ T cells/Tregs was also decreased in patients compared to healthy donors. The presence of Tregs was accompanied by a decrease in IL-10 but not TGF-β secretion in OSCC patients when compared to donors; in addition, the analysis also revealed that an increased presence of Tregs was accompanied by better patient survival. Amongst OSCC patients, smokers had significantly higher levels of TGF-β. It is apparent that the immune system is compromised in OSCC patients and the characterization of the Treg subpopulation could form a basis for improving our understanding of the perturbations in the immune system that occur during OSCC tumorigenesis.

The ever-increasing number of tumor-associated antigens has provided a major stimulus for the development of therapeutic peptides vaccines. Tumor-associated peptides can induce high immune response rates and have been developed as vaccines for several types of solid tumors, and many are at various stages of clinical testing. MAGED4B, a melanoma antigen, is overexpressed in oral squamous cell carcinoma (OSCC) and this expression promotes proliferation and cell migration. In this study, we have identified 9 short peptides derived from MAGED4B protein that are restricted in binding to the HLA subtypes common in the Asian population (HLA-A2, A11, and A24). The peptides had good binding affinity with the MHC-Class I molecules and stimulated ex-vivo IFN-gamma and Granzyme-B production in blood samples from OSCC patients, suggesting that they are immunogenic. Further, T cells stimulated with peptide-pulsed dendritic cells showed enhanced T-cell cytotoxic activity against MAGED4B-overexpressing OSCC cell lines. In summary, we have identified MAGED4B peptides that induce anti-tumor immune responses advocating that they could be further developed as vaccine candidates for the treatment of OSCC.