Dendritic cells infiltrating tumors cotransduced with granulocytes/macrophage colony-stimulating factor (GM-CSF) and CD40 ligand genes take up and present endogenous tumor-associated antigens, and prime naive mice for a cytotoxic T-lymphocyte response.

We transduced BALB/c-derived C-26 colon carcinoma cells with granulocyte/macrophage colony-stimulating factor (GM-CSF) and CD40 ligand (CD40L) genes to favor interaction of these cells with host dendritic cells (DCs) and, therefore, cross-priming. Cotransduced cells showed reduced tumorigenicity, and tumor take was followed by regression in some mice. In vivo tumors were heavily infiltrated with DCs that were isolated, phenotyped, and tested in vitro for stimulation of tumor-specific cytotoxic T lymphocytes (CTLs). BALB/c C-26 carcinoma cells express the endogenous murine leukemia virus (MuLV) env gene as a tumor-associated antigen. This antigen is shared among solid tumors of BALB/c and C57BL/6 mice and contains two epitopes, AH-1 and KSP, recognized in the context of major histocompatibility complex class I molecules H-2L(d) and H-2K(b), respectively. DCs isolated from C-26/GM/CD40L tumors grown in (BALB/c X C57BL/6)F1 mice (H-2(dXb)) stimulated interferon gamma production by both anti-AH-1 and KSP CTLs, whereas tumor-infiltrating DCs (TIDCs) of BALB/c mice stimulated only anti-AH-1 CTLs. Furthermore, TIDCs primed naive mice for CTL activity as early as 2 d after injection into the footpad, whereas double-transduced tumor cells required at least 5 d for priming; this difference may reflect direct DC priming versus indirect tumor cell priming. Immunohistochemical staining indicated colocalization of DCs and apoptotic bodies in the tumors. These data indicate that DCs infiltrating tumors that produce GM-CSF and CD40L can capture cellular antigens, likely through uptake of apoptotic bodies, and mature in situ to a stage suitable for antigen presentation. Thus, tumor cell-based vaccines engineered to favor the interaction with host DCs can be considered

Mast cell targeting hampers prostate adenocarcinoma development but promotes the occurrence of highly malignant neuroendocrine cancers

Mast cells (MC) are c-Kit-expressing cells, best known for their primary involvement in allergic reactions, but recently reappraised as important players in either cancer promotion or inhibition. Here, we assessed the role of MCs in prostate tumor development. In prostate tumors from both tumor-prone transgenic adenocarcinoma of the mouse prostate (TRAMP) mice and human patients, MCs are specifically enriched and degranulated in areas of well-differentiated (WD) adenocarcinoma but not around poorly differentiated (PD) foci that coexist in the same tumors. We derived novel TRAMP tumor cell lines, representative of WD and PD variants, and through pharmacologic stabilization or genetic ablation of MCs in recipients mice, we showed that MCs promote WD adenocarcinoma growth but are dispensable for PD tumors. WD tumors rely on MCs for matrix metalloprotease 9 (MMP-9) provision, as reconstitution of MC-deficient mice with wild-type but not MMP-9 -/- MCs was sufficient to promote their growth. In contrast, PD tumors are MMP-9 self-competent, consistently with epithelial-to-mesenchymal transition. Such a dual source of MMP-9 was confirmed in human tumors, suggesting that MCs could be a good target for early-stage prostate cancer. Interestingly, in testing whether MC targeting could block or delay tumorigenesis in tumor-prone TRAMP mice, we observed a high incidence of early and aggressive tumors, characterized by a neuroendocrine (NE) signature and c-Kit expression. Taken together, these data underscore the contribution of MCs in tumor progression and uncover a new, opposite role of MCs in protecting against the occurrence of aggressive NE variants in prostate cancer. ©2011 AACR

HOXB7: a key factor for tumo-associated angiogenic switch.

We had demonstrated previously a functional bridge between altered homebox (HOX) gene expression and tumor progression through HOXB7 transactivation of basic fibroblast growth factor. Here, we have studied whether HOXB7, in addition to basic fibroblast growth factor, may induce other genes directly or indirectly related to neoangiogenesis and tumor invasion. Parental, beta-galactosidase-transduced, and HOXB7-transduced SkBr3 cell lines were examined for the expression of several growth factors and growth factor receptors involved in the proliferative and angiogenic processes. Vascular endothelial growth factor, melanoma growth-stimulatory activity/growth-related oncogenene alpha, interleukin-8, and angiopoietin-2 were up-regulated by HOXB7 transduction. The exception was angiopoietin-1 expression that was abrogated. Additional analyses included the expression levels of enzymes such as matrix metalloprotease (MMP)-2 and MMP-9 and heparanase, capable of proteolytic degradation of extracellular matrix and basement membranes. Results showed an induction of only MMP-9. The functional implication of such a finding was tested using an in vitro coculture assay in a three-dimensional matrix. A delay of differentiation with persistent nests of proliferating cells was found in endothelial cells cocultured with HOXB7-transduced SkBr3 cells. Tumorigenicity of these cells has been evaluated in vivo. Xenograft into athymic nude mice showed that SkBr3/HOXB7 cells developed tumors in mice, either irradiated or not, whereas parental SkBr3 cells did not show any tumor take unless mice were sublethally irradiated. Comparison of tumor nodules for vascularization by CD-31 and CD-34 immunostaining revealed an increased number of blood vessels in tumors expressing HOXB7. Together, the results indicate HOXB7 as a key factor up-regulating a variety of proangiogenic stimuli. Thus, HOXB7 gene or protein is a target to aim at to inhibit tumor-associated neoangiogenesis, considering the number and the redundancy of proangiogenic molecules that should be targeted one by one to theoretically achieve the same effect

Granulocyte colony-stimulating factor (G-CSF) gene transduction in murine adenocarcinoma drives neutrophil-mediated tumor inhibition in vivo. Neutrophils discriminate between G-CSF-producing and G-CSF-nonproducing tumor cells.

We have previously demonstrated that the murine colon adenocarcinoma C-26 cell line transduced with the human gene for the granulocyte CSF (G-CSF) loses tumorigenic activity through a mechanism that involved massive targeting of neutrophils at the site of tumor injection. The suppression of tumorigenicity by G-CSF was limited to the G-CSF-producing cells and was not transferred to nonproducing C-26 cells in a mixed tumor transplantation assay. We present direct evidence that neutrophils are involved in this phenomenon. We firstly examined, by electron microscopy (EM), the morphology of tumor infiltrates obtained 2, 5, and 10 days after s.c. injection of a mixture of G-CSF-producing and -nonproducing C-26 cells into syngeneic BALB/c mice. The EM analysis showed at 5, but not at 2 or 10 days, the presence of neutrophils in intimate contact with tumor cells. We then investigated whether neutrophils discriminate between G-CSF-producing and -nonproducing C-26 cells. To this aim, C-26 cells were transduced, via retroviral vector, with the Escherichia coli LacZ gene and mixed tumor transplantation assays were performed by injecting a mixture of G-CSF-producing beta-gal- and G-CSF-nonproducing beta-gal+ C-26 cells at different ratios. Histologic and EM analysis of the tumors growing at the site of injection were carried out. Five days after injection, treatment with x-gal revealed, at the histochemical level, the presence of neutrophils around G-CSF producing beta-gal- cells; cell-cell contacts and fusion of cell membranes were detected by EM only between neutrophils and G-CSF-producing cells. In vitro experiments, performed in Boyden chambers, confirmed that the G-CSF produced by C-26 cells was a chemoattractant for neutrophils. In addition, a colorimetric, cytostatic assay revealed that neutrophils were able to inhibit the growth of G-CSF-producing but not of G-CSF-nonproducing C-26 cells. Thus the tumor take after injection of G-CSF-producing C-26 cells seems to be controlled in situ through two major mechanisms namely neutrophil chemotaxis and neutrophil-mediated tumor inhibition. The results indicate that neutrophils can discriminate between G-CSF-producing and -nonproducing tumor cells and that neutrophils infiltrate the tumor mixture as long as G-CSF-producing cells are present

Granulocyte colony-stimulating factor gene transfer suppresses tumorigenicity of a murine adenocarcinoma in vivo.

We have investigated the effect of granulocyte colony-stimulating factor (G-CSF) delivery at the site of tumor growth by transducing, via retroviral vector, the human (hu) G-CSF gene into the colon adenocarcinoma C-26 and assaying the ability of transduced cells to form tumors when injected into syngeneic mice. As a control, the same tumor cells were infected with retroviruses engineered to transduce an unrelated gene, the human nerve growth factor receptor, or carry the neomycin resistance gene only. Only cells transduced with the huG-CSF were unable to develop tumors, although huG-CSF was expressed and produced at low level as estimated by both RNA analysis and enzyme-linked immunosorbent assay, indicating that G-CSF can exert an antitumor effect at a physiological dose. Implication of G-CSF as mediator of tumor inhibition was proven by reversing the nontumorigenic phenotype of G-CSF-expressing cells with anti-huG-CSF monoclonal antibody injected at the tumor site. No tumors were formed by injecting C-26 infected cells into nu/nu mice, while neoplastic nodules appeared after injection into sublethally irradiated mice; such tumors, however, regressed when mice normalized their leukocyte counts after irradiation. Tumors were also formed after injection of a mixture of infected and uninfected C-26 cells, although critical delay in tumor formation occurred when infected cells were 10 times more represented in the mixture. Histological examination of tissues surrounding the site of injection showed infiltration of neutrophilic granulocytes, whose number correlated with that of G-CSF-expressing C-26 cells in the injected mixture. These results indicate that G-CSF may have a potent antitumoral activity when released, even at low doses, at the tumor site. The antitumoral effect is mediated by recruitment and targeting of neutrophilic granulocytes to G-CSF-releasing cells