Human papillomavirus oncoproteins induce a reorganization of epithelial-associated γδ T cells promoting tumor formation.

It has been shown that γδ T cells protect against the formation of squamous cell carcinoma (SCC) in several models. However, the role of γδ T cells in human papillomavirus (HPV)-associated uterine cervical SCC, the third-leading cause of death by cancer in women, is unknown. Here, we investigated the impact of γδ T cells in a transgenic mouse model of carcinogenesis induced by HPV16 oncoproteins. Surprisingly, γδ T cells promoted the development of HPV16 oncoprotein-induced lesions. HPV16 oncoproteins induced a decrease in epidermal Skint1 expression and the associated antitumor Vγ5+ γδ T cells, which were replaced by γδ T-cell subsets (mainly Vγ6+ γδlowCCR2+CCR6-) actively producing IL-17A. Consistent with a proangiogenic role, γδ T cells promoted the formation of blood vessels in the dermis underlying the HPV-induced lesions. In human cervical biopsies, IL-17A+ γδ T cells could only be observed at the cancer stage (SCC), where HPV oncoproteins are highly expressed, supporting the clinical relevance of our observations in mice. Overall, our results suggest that HPV16 oncoproteins induce a reorganization of the local epithelial-associated γδ T-cell subpopulations, thereby promoting angiogenesis and cancer development.

Characterization of spontaneous bone marrow recovery after sublethal total body irradiation: importance of the osteoblastic/adipocytic balance.

Many studies have already examined the hematopoietic recovery after irradiation but paid with very little attention to the bone marrow microenvironment. Nonetheless previous studies in a murine model of reversible radio-induced bone marrow aplasia have shown a significant increase in alkaline phosphatase activity (ALP) prior to hematopoietic regeneration. This increase in ALP activity was not due to cell proliferation but could be attributed to modifications of the properties of mesenchymal stem cells (MSC). We thus undertook a study to assess the kinetics of the evolution of MSC correlated to their hematopoietic supportive capacities in mice treated with sub lethal total body irradiation. In our study, colony-forming units-fibroblasts (CFU-Fs) assay showed a significant MSC rate increase in irradiated bone marrows. CFU-Fs colonies still possessed differentiation capacities of MSC but colonies from mice sacrificed 3 days after irradiation displayed high rates of ALP activity and a transient increase in osteoblastic markers expression while pparγ and neuropilin-1 decreased. Hematopoietic supportive capacities of CFU-Fs were also modified: as compared to controls, irradiated CFU-Fs significantly increased the proliferation rate of hematopoietic precursors and accelerated the differentiation toward the granulocytic lineage. Our data provide the first evidence of the key role exerted by the balance between osteoblasts and adipocytes in spontaneous bone marrow regeneration. First, (pre)osteoblast differentiation from MSC stimulated hematopoietic precursor's proliferation and granulopoietic regeneration. Then, in a second time (pre)osteoblasts progressively disappeared in favour of adipocytic cells which down regulated the proliferation and granulocytic differentiation and then contributed to a return to pre-irradiation conditions.

Leptin reverts pro-apoptotic and antiproliferative effects of α-linolenic acids in BCR-ABL positive leukemic cells: involvement of PI3K pathway.

It is suspected that bone marrow (BM) microenvironmental factors may influence the evolution of chronic myeloid leukaemia (CML). In this study, we postulated that adipocytes and lipids could be involved in the progression of CML. To test this hypothesis, adipocytes were co-cultured with two BCR-ABL positive cell lines (PCMDS and K562). T cell (Jurkat) and stroma cell (HS-5) lines were used as controls. In the second set of experiments, leukemic cell lines were treated with stearic, oleic, linoleic or α-linolenic acids in presence or absence of leptin. Survival, proliferation, leptin production, OB-R isoforms (OB-Ra and OB-Rb), phosphoinositide 3-kinase (PI3k) and BCL-2 expression have been tested after 24h, 48h and 72h of treatment. Our results showed that adipocytes induced a decrease of CML proliferation and an increase in lipid accumulation in leukemic cells. In addition, CML cell lines induced adipocytes cell death. Chromatography analysis showed that BM microenvironment cells were full of saturated (SFA) and monounsaturated (MUFA) fatty acids, fatty acids that protect tumor cells against external agents. Stearic acid increased Bcl-2 expression in PCMDS, whereas oleic and linoleic acids had no effects. In contrast, α-linolenic acid decreased the proliferation and the survival of CML cell lines as well as BCL-2 and OB-R expression. The effect of α-linolenic acids seemed to be due to PI3K pathway and Bcl-2 inhibition. Leptin production was detected in the co-culture medium. In the presence of leptin, the effect of α-linolenic acid on proliferation, survival, OB-R and BCl-2 expression was reduced.

Human bone marrow adipocytes block granulopoiesis through neuropilin-1-induced granulocyte colony-stimulating factor inhibition.

Adipocytes are part of hematopoietic microenvironment, even though up to now in humans, their role in hematopoiesis is still questioned. We have previously shown that accumulation of fat cells in femoral bone marrow (BM) coincides with increased expression of neuropilin-1 (NP-1), while it is weakly expressed in hematopoietic iliac crest BM. Starting from this observation, we postulated that adipocytes might exert a negative effect on hematopoiesis mediated through NP-1. To test this hypothesis, we set up BM adipocytes differentiated into fibroblast-like fat cells (FLFC), which share the major characteristics of primitive unilocular fat cells, as an experimental model. As expected, FLFCs constitutively produced macrophage colony stimulating factor and induced CD34(+) differentiation into macrophages independently of cell-to-cell contact. By contrast, granulopoiesis was hampered by cell-to-cell contact but could be restored in transwell culture conditions, together with granulocyte colony stimulating factor production. Both functions were also recovered when FLFCs cultured in contact with CD34(+) cells were treated with an antibody neutralizing NP-1, which proved its critical implication in contact inhibition. An inflammatory cytokine such as interleukin-1 beta or dexamethasone modulates FLFC properties to restore granulopoiesis. Our data provide the first evidence that primary adipocytes exert regulatory functions during hematopoiesis that might be implicated in some pathological processes. Disclosure of potential conflicts of interest is found at the end of this article.

Tumoral and choroidal vascularization: differential cellular mechanisms involving plasminogen activator inhibitor type I.

An adequate balance between serine proteases and their plasminogen activator inhibitor-1 (PAI-1) is critical for pathological angiogenesis. PAI-1 deficiency in mice is associated with impaired choroidal neovascularization (CNV) and tumoral angiogenesis. In the present work, we demonstrate unexpected differences in the contribution of bone marrow (BM)-derived cells in these two processes regulated by PAI-1. PAI-1(-/-) mice grafted with BM-derived from wild-type mice were able to support laser-induced CNV formation but not skin carcinoma vascularization. Engraftment of irradiated wild-type mice with PAI-1(-/-) BM prevented CNV formation, demonstrating the crucial role of PAI-1 delivered by BM-derived cells. In contrast, the transient infiltration of tumor transplants by local PAI-1-producing host cells rather than by BM cells was sufficient to rescue tumor growth and angiogenesis in PAI-1-deficient mice. These data identify PAI-1 as a molecular determinant of a local permissive soil for tumor angiogenesis. Altogether, the present study demonstrates that different cellular mechanisms contribute to PAI-1-regulated tumoral and CNV. PAI-1 contributes to BM-dependent choroidal vascularization and to BM-independent tumor growth and angiogenesis.

Murine bone marrow stromal cells sustain in vivo the survival of hematopoietic stem cells and the granulopoietic differentiation of more mature progenitors.

The study of the human hematopoietic system would be facilitated by availability of a relevant animal model. Because the medullar microenvironment is made of different types of cells, interactions between hematopoietic cells and stromal cells are difficult to analyze in detail. As an approach for establishing an in vivo model to dissect these interactions, we grafted murine bone marrow fibroblastic cells (MS-5 cell line) with hematopoietic cells into the kidney capsule of syngenic mice. To identify the origin of cells present in the graft, we used green fluorescent protein-stable transfected MS-5 cells for the transplantation. To analyze the evolution of stromal cells and identify hematopoietic cells able to develop in these conditions, we performed morphology, histochemistry, and immunohistology on tissue sections at different times after transplantation. When injected alone, MS-5 cells differentiate into adipocytes. When injected with a bone marrow suspension or with isolated CD45+ cells (leukocytes), the stromal cells keep their fibroblastic morphology and their alkaline phosphatase expression and sustain granulopoiesis. When injected with hematopoietic stem cells called c-kit+ Sca-1+ Lin- suspension, clusters of hematopoietic cells are also observed: They do not present any granulopoietic activity and do not belong to B or T population nor to erythroid lineage. They are quiescent, induce bone marrow recovery and survival of lethally irradiated recipients, are able to form macroscopic colonies in the spleen, and are able to form very few colonies in vitro, suggesting that they are hematopoietic stem cells. In conclusion, our results show that reticular fibroblastic stromal cells MS-5 sustain the survival of stem cells and are not able to induce their differentiation. However, they can control differentiation, proliferation, and/or survival of hematopoietic cells engaged in myeloid lineage.

Differential expression of vascular endothelial growth factor and its receptors in hematopoietic and fatty bone marrow: evidence that neuropilin-1 is produced by fat cells.

Vascular endothelial growth factor (VEGF), its receptors (VEGFR-1, VEGFR-2) and neuropillin-1 (NRP-1) are expressed at variable levels in bone marrow. NRP-1expression is higher in fatty bone marrow than in hematopoietic marrow. Adipocytes are responsible for NRP-1 expression suggesting that they may play a role in hematopoiesis by producing NRP-1 or that NRP-1 may regulate adipocyte activity.

Maintenance of functional human cancellous bone and human hematopoiesis in NOD/SCID mice.

Attempts were made to establish models to study interactions between marrow stromal cells and hematopoietic cells in vivo. The approach was to create a NOD-SCID-hu murine model of long-term human hematopoiesis by implantation of a human adult bone fragment. Nine to 12 weeks posttransplantation, human CD45+ cells were detected in the blood and the spleen of some mice. The histology of the human transplant showed that human bone fragment was viable at 9 weeks. Moreover, vessels of human origin, as assessed by immunohistochemical detection of human beta2-microglobulin, were observed in the mouse tissue surrounding the transplanted human fragment.

Transient modifications of respiratory capacity in thymic cells during murine radioleukemogenesis.

The evolution of mitochondrial oxidative phosphorylation was studied during cancer induction in a model of thymic radiolymphomagenesis in C57BL/Ka mice. During the preneoplastic period, thymuses displayed an increase of the cytochrome c oxidase activity and oxygen consumption together with oxidative DNA damage assessed by the presence of the 8-hydroxydeoxyguanine DNA base modification. These transient changes in mitochondrial functional activity were not observed in thymuses of mice rescued from lymphoma development by a bone marrow graft, suggesting an important role of mitochondria for neoplastic transformation in this model, which might therefore be of interest to test the utilization of antioxidants for the prevention of radiation-induced malignancies.