Adipose mesenchymal stromal cells: Definition, immunomodulatory properties, mechanical isolation and interest for plastic surgery.

Ever since their discovery in 2001, adipose mesenchymal stromal cells (ASC) have profoundly modified clinical indications and our practice of plastic surgery, thereby placing our discipline at the forefront of regenerative medicine. These cells act through paracrine signaling by synthesizing immunosuppressive and pro-angiogenic factors. They are of key importance with regard to the regenerative properties of autologously grafted adipose tissue (AT). Taken together, they make up the stromal vascular fraction (SVF) comprising all AT cells except for adipocytes. As our knowledge evolves, we are moving from fat grafting towards SVF grafting, of which the essential sought-after effect is tissue regeneration. The objective of the present review is to synthesize present-day information on ASCs and their immunomodulatory properties and, from a practical standpoint, to indicate present-day and future steps towards establishment of clinical routine, particularly through application of techniques favoring mechanical digestion of adipose tissue.

ING1b negatively regulates HIF1α protein levels in adipose-derived stromal cells by a SUMOylation-dependent mechanism.

Hypoxic niches help maintain mesenchymal stromal cell properties, and their amplification under hypoxia sustains their immature state. However, how MSCs maintain their genomic integrity in this context remains elusive, since hypoxia may prevent proper DNA repair by downregulating expression of BRCA1 and RAD51. Here, we find that the ING1b tumor suppressor accumulates in adipose-derived stromal cells (ADSCs) upon genotoxic stress, owing to SUMOylation on K193 that is mediated by the E3 small ubiquitin-like modifier (SUMO) ligase protein inhibitor of activated STAT protein γ (PIAS4). We demonstrate that ING1b finely regulates the hypoxic response by triggering HIF1α proteasomal degradation. On the contrary, when mutated on its SUMOylation site, ING1b failed to efficiently decrease HIF1α levels. Consistently, we observed that the adipocyte differentiation, generally described to be downregulated by hypoxia, was highly dependent on ING1b expression, during the early days of this process. Accordingly, contrary to what was observed with HIF1α, the absence of ING1b impeded the adipogenic induction under hypoxic conditions. These data indicate that ING1b contributes to adipogenic induction in adipose-derived stromal cells, and thus hinders the phenotype maintenance of ADSCs.

[Adipose-derived stromal cells: history, isolation, immunomodulatory properties and clinical perspectives]. / Les cellules stromales mésenchymateuses du tissu adipeux : historique, isolement, propriétés immunomodulatrices et perspectives cliniques.

Over the last decade, the clinical use of adipose-derived stromal/stem cells (ASC) in regenerative medicine is rapidly increasing. ASC belong to the mesenchymal stromal cells initially obtained from the bone marrow. Their limited differentiation capacity in vivo into functional mature cells has led to a reassessment of their mechanisms of action. One of the major clinical interests appears related to paracrine effects through a temporary production of trophic and immunomodulatory factors. Our purpose is to provide a review on the latest knowledge in the field of ASC, mechanisms of action, mainly immunomodulatory/immunosuppressive properties, methods of obtention, with a focus on clinical perspectives particularly in the field of cellular therapy and fat grafting technique in plastic surgery.

High level of soluble programmed cell death ligand 1 in blood impacts overall survival in aggressive diffuse large B-Cell lymphoma: results from a French multicenter clinical trial.

The dosage of soluble programmed cell death ligand 1 (sPD-L1) protein in the blood of adults with cancer has never been performed in a prospective patient cohort. We evaluated the clinical impact of sPD-L1 level measured at the time of diagnosis for newly diagnosed diffuse large B-cell lymphoma (DLBCL). Soluble PD-L1 was measured in the plasma of 288 patients enrolled in a multicenter, randomized phase III trial that compared R-high-dose chemotherapy with R-CHOP. The median follow-up was 41.4 months. A cutoff of 1.52 ng/ml of PD-L1 level was determined and related to overall survival (OS). Patients with elevated sPD-L1 experienced a poorer prognosis with a 3-year OS of 76% versus 89% (P<0.001). Considering clinical characteristics, the multivariate analysis retained this biomarker besides bone marrow involvement and abnormal lymphocyte-monocyte score as independently related to poor outcome. sPD-L1 was detectable in the plasma and not in the serum, found elevated in patients at diagnosis compared with healthy subjects and its level dropped back to normal value after CR. The intention-to-treat analysis showed that elevated sPD-L1 was associated with a poorer prognosis for patients randomized within the R-CHOP arm (P<0.001). Plasma PD-L1 protein is a potent predicting biomarker in DLBCL and may indicate usefulness of alternative therapeutic strategies using PD-1 axis inhibitors.

IL-6 supports the generation of human long-lived plasma cells in combination with either APRIL or stromal cell-soluble factors.

The recent understanding of plasma cell (PC) biology has been obtained mainly from murine models. The current concept is that plasmablasts home to the BM and further differentiate into long-lived PCs (LLPCs). These LLPCs survive for months in contact with a complex niche comprising stromal cells (SCs) and hematopoietic cells, both producing recruitment and survival factors. Using a multi-step culture system, we show here the possibility to differentiate human memory B cells into LLPCs surviving for at least 4 months in vitro and producing immunoglobulins continuously. A remarkable feature is that IL-6 is mandatory to generate LLPCs in vitro together with either APRIL or soluble factors produced by SCs, unrelated to APRIL/BAFF, SDF-1, or IGF-1. These LLPCs are out of the cell cycle, express highly PC transcription factors and surface markers. This model shows a remarkable robustness of human LLPCs, which can survive and produce highly immunoglobulins for months in vitro without the contact with niche cells, providing the presence of a minimal cocktail of growth factors and nutrients. This model should be useful to understand further normal PC biology and its deregulation in premalignant or malignant PC disorders.

Unique B cell differentiation profile in tolerant kidney transplant patients.

Operationally tolerant patients (TOL) display a higher number of blood B cells and transcriptional B cell signature. As they rarely develop an allo-immune response, they could display an abnormal B cell differentiation. We used an in vitro culture system to explore T-dependent differentiation of B cells into plasma cells. B cell phenotype, apoptosis, proliferation, cytokine, immunoglobulin production and markers of differentiation were followed in blood of these patients. Tolerant recipients show a higher frequency of CD20(+) CD24(hi) CD38(hi) transitional and CD20(+) CD38(lo) CD24(lo) naïve B cells compared to patients with stable graft function, correlating with a decreased frequency of CD20(-) CD38(+) CD138(+) differentiated plasma cells, suggestive of abnormal B cell differentiation. B cells from TOL proliferate normally but produce more IL-10. In addition, B cells from tolerant recipients exhibit a defective expression of factors of the end step of differentiation into plasma cells and show a higher propensity for cell death apoptosis compared to patients with stable graft function. This in vitro profile is consistent with down-regulation of B cell differentiation genes and anti-apoptotic B cell genes in these patients in vivo. These data suggest that a balance between B cells producing IL-10 and a deficiency in plasma cells may encourage an environment favorable to the tolerance maintenance.

Monocytes and T cells cooperate to favor normal and follicular lymphoma B-cell growth: role of IL-15 and CD40L signaling.

Interleukin-15 (IL-15) has been extensively studied for its role in the survival and proliferation of NK and T cells through a unique mechanism of trans-presentation by producer cells. Conversely, whereas activated B cells have been described as IL-15-responding cells, the cellular and molecular context sustaining this effect remains unexplored. In this study, we found that, whereas human B cells could not respond to soluble IL-15, monocytes and lymphoid tissue-derived macrophages but not stromal cells efficiently trans-present IL-15 to normal B cells and cooperate with T-cell-derived CD40L to promote IL-15-dependent B-cell proliferation. Furthermore, CD40L signaling triggers a Src-independent upregulation of STAT5 expression and favors a Src-dependent phosphorylation of STAT5 in response to IL-15. In follicular lymphoma (FL), immunohistochemical studies reported a strong relationship between malignant B cells, infiltrating macrophages and T cells. We show here an overexpression of IL-15 in purified tumor-associated macrophages, and STAT5A in purified tumor B cells. Moreover, FL B cells respond to IL-15 trans-presented by monocytes/macrophages, in particular, in the presence of CD40L-mediated signaling. This cooperation between IL-15 and CD40L reinforces the importance of tumor microenvironment and unravels a mechanism of FL growth that should be considered if using IL-15 as a drug in this disease.

Characterization of intratumoral follicular helper T cells in follicular lymphoma: role in the survival of malignant B cells.

Accumulating evidences indicate that the cellular and molecular microenvironment of follicular lymphoma (FL) has a key role in both lymphomagenesis and patient outcome. Malignant FL B cells are found admixed to specific stromal and immune cell subsets, in particular CD4(pos) T cells displaying phenotypic features of follicular helper T cells (T(FH)). The goal of our study was to functionally characterize intratumoral CD4(pos) T cells. We showed that CXCR5(hi)ICOS(hi)CD4(pos) T cells sorted from FL biopsies comprise at least two separate cell populations with distinct genetic and functional features: (i) CD25(pos) follicular regulatory T cells (T(FR)), and (ii) CD25(neg) T(FH) displaying a FL-B cell supportive activity without regulatory functions. Furthermore, despite their strong similarities with tonsil-derived T(FH), purified FL-derived T(FH) displayed a specific gene expression profile including an overexpression of several genes potentially involved directly or indirectly in lymphomagenesis, in particular TNF, LTA, IL4 or CD40LG. Interestingly, we further demonstrated that these two last signals efficiently rescued malignant B cells from spontaneous and rituximab-induced apoptosis. Altogether, our study demonstrates that tumor-infiltrating CD4(pos) T cells are more heterogeneous than previously presumed, and underlines for the first time the crucial role of T(FH) in the complex set of cellular interactions within FL microenvironment.

Follicular lymphoma cell niche: identification of a preeminent IL-4-dependent T(FH)-B cell axis.

Follicular lymphoma (FL) B cells contract tight connections with their microenvironment, which governs the pathogenesis and progression of the disease. Indeed, specific immune response gene signatures, obtained from whole biopsy samples, have been associated with patient survival. In this study, we performed gene expression profiling of purified B cell and non-B cell compartments obtained from FL and reactive lymph nodes. We identified 677 non-redundant genes defining the FL interface and involving 26 FL-specific functional networks. This approach highlighted an interleukin-4 (IL-4)-centered pathway associated with an activation of signal transducer and activator of transcription 6 (STAT6), which favors overexpression of IL-4-target genes. In addition, FL microenvironment was characterized by a strong enrichment in follicular helper T cells (T(FH)), as demonstrated through transcriptomic and flow cytometry analyses. The majority of phospho-STAT6(pos) B cells were located at the vicinity of cells expressing the programmed death 1 (PD-1) T(FH) marker. Moreover, purified FL-derived T(FH), expressed IL4 at very high levels compared with purified tonsil-derived T(FH) or non-T(FH) microenvironment. Altogether, our study demonstrated that tumor-infiltrating T(FH) specifically express functional IL-4 in FL, creating an IL-4-dependent T(FH)-B cell axis. This cross talk could sustain FL pathogenesis and represent a new potential therapeutic target.

Identifying intercellular signaling genes expressed in malignant plasma cells by using complementary DNA arrays.

In multiple myeloma (MM), the growth of primary plasma cells depends not only on interleukin-6 (IL-6), but also on additional unidentified signals delivered by the bone marrow environment. Using Atlas complementary DNA (cDNA) arrays comprising 268 genes coding for intercellular signaling molecules, this study identified genes that are overexpressed in myeloma cells compared to autologous B-lymphoblastoid cell lines. These genes encode the oncogenic Tyro3 tyrosine kinase receptor, the heparin-binding epidermal growth factor-like growth factor (HB-EGF) that is an epithelial autocrine tumor growth factor, the thrombin receptor (TR) that is linked to HB-EGF and syndecan-1 processing and to cell invasion, chemokine receptors CCR1 and CCR2, the Wnt pathway actor Frizzled-related protein (FRZB), and the Notch receptor ligand Jagged 2. These data, obtained with the Atlas cDNA array, were confirmed by reverse transcriptase-polymerase chain reaction or protein analysis or both. Furthermore, Tyro3, HB-EGF, TR, and FRZB gene expression was documented in purified primary malignant plasma cells from patients with plasma cell leukemia or MM. HB-EGF and FRZB were poorly expressed in purified polyclonal plasma cells. Finally, HB-EGF was proved to be an essential autocrine growth factor for the XG-1 myeloma cells. This study shows the potency and the biologic relevance of cDNA arrays used to analyze simultaneously a large panel of intercellular signaling genes and, by identifying several genes overexpressed in malignant plasma cells, opens new fields of investigation in MM biology. (Blood. 2001;98:771-780)

JAK2 tyrosine kinase inhibitor tyrphostin AG490 downregulates the mitogen-activated protein kinase (MAPK) and signal transducer and activator of transcription (STAT) pathways and induces apoptosis in myeloma cells.

Cytokines of the interleukin 6 (IL-6) family, which activates the signal transducer gp130, are major survival and growth factors for human multiple myeloma (MM) cells. The signal transduction of gp130 involves the Janus tyrosine kinases (JAK) JAK1, JAK2 and Tyk2 and then the downstream effectors comprising the signal transducer and activator of transcription 3 (STAT3) and mitogen-activated protein kinase (MAPK) pathways. We evaluated the effects of the JAK2 inhibitor tyrphostin AG490 on MM cells. We found that AG490 suppressed cell proliferation and induced apoptosis in IL-6-dependent MM cell lines. JAK2 kinase activity, ERK2 and STAT3 phosphorylation were inhibited. These results suggest that the chemical blocking of the gp130 signalling pathway at the JAK level could be a relevant therapeutic approach to MM.

Extensive characterization of dendritic cells generated in serum-free conditions: regulation of soluble antigen uptake, apoptotic tumor cell phagocytosis, chemotaxis and T cell activation during maturation in vitro.

Dendritic cells (DC) play a key role in the initiation of primary immune response, and pilot clinical studies have demonstrated their ability to induce efficient antitumor immunity. However, the DC used in these clinical trials were generated with various serum sources and were poorly characterized. Obtaining fully characterized DC in controlled and reproducible culture conditions is thus of major interest. We demonstrate that X-VIVO 15 medium supplemented with 2% human albumin can be used to obtain DC. The phenotypic and functional characteristics of these clinical-grade DC were analyzed according to their differentiation stages. CD83 immature DC, obtained in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-4, were able to endocyte soluble antigens and internalize apoptotic tumor cells, and also expressed receptors for inflammatory chemokines. Tumor necrosis factor-alpha (TNF-alpha) induced irreversible DC maturation in association with a decreased ability to uptake antigens and an increased allostimulatory capacity. CD83+ mature DC became responsive to EBI1 ligand chemokine (ELC), a chemokine specifically expressed in secondary lymphoid organs. In addition, mature DC obtained with TNF-alpha produced IL-12 and some IL-10 in response to CD40 stimulation. In conclusion, we present well-defined culture conditions allowing the control of DC maturation for clinical or fundamental studies.

Dendritic cell-based vaccine: a promising approach for cancer immunotherapy.

The unique ability of dendritic cells to pick up antigens and to activate naive and memory CD4+ and CD8+ T cells raised the possibility of using them to trigger a specific anti-tumor immunity. If numerous studies have shown a major interest in dendritic cell-based vaccines for cancer immunotherapy in animal models, only a few have been carried out in human cancers. In this review, we describe recent findings in the biology of dendritic cells that are important to generate anti-tumor cytotoxic T cells in vitro and we also detail clinical studies reporting the obtention of specific immunity to human cancers in vivo using reinfusion of dendritic cells pulsed with tumor antigens.

Induced expression of B7-1 on myeloma cells following retroviral gene transfer results in tumor-specific recognition by cytotoxic T cells.

The aim of this study was to evaluate whether tumor cells from patients with multiple myeloma activate allogeneic and autologous T cells. Results showed that myeloma cells expressed few B7-2 and no B7-1 in six cell lines and primary cells from 11 patients. They expressed substantial levels of HLA class I, CD40, and a set of adhesion molecules. In accordance with the low density of B7 molecules on these cells, they were poor allogeneic CD8+ T cell stimulators. Neither IFN-gamma plus TNF-alpha nor CD40 stimulation significantly induced B7-1 or up-regulated B7-2 on human myeloma cell line or primary myeloma cells from six of seven patients. However, such induction was found on autologous bone-marrow nontumoral cells and on autologous dendritic cells following CD40 stimulation. High B7-1 expression was stably obtained on human myeloma cell line using transduction with a B7-1 retrovirus, enabling these cells to stimulate allogeneic CD8+, though not CD4+, T cell proliferation. For one patient with advanced disease, B7-1 gene transfer made it possible to amplify autologous cytotoxic T cells that killed autologous myeloma cells in an HLA class I-restricted manner, but not autologous PHA blasts. These results suggest that B7-1 gene transfer could be a promising immunotherapeutic approach in multiple myeloma.

Tumor necrosis factor is a survival and proliferation factor for human myeloma cells.

Interleukin-6 (IL-6) is a major survival factor for malignant plasma cells. In patients with multiple myeloma (MM), cell lines whose survival and proliferation are dependent upon addition of exogenous IL-6 have been obtained. We show here that tumor necrosis factor-alpha (TNF-alpha) is also a survival factor for myeloma cell lines, although less potent than IL-6. The survival activity of TNF-alpha is not affected by anti-IL-6 or anti-gp130 monoclonal antibodies (mAbs). TNF-alpha also induces myeloma cells in the cell cycle and promotes the long-term growth of malignant plasma cell lines. As TNF-alpha is produced in patients with MM and associated with a poor prognosis, these results suggest that anti-TNF-alpha therapies could be useful in this disease.

Evidence against KSHV infection in the pathogenesis of multiple myeloma.

Kaposi's sarcoma-associated herpesvirus (KSHV) is likely to play a pathogenic role in Kaposi's sarcoma, body cavity-based primary effusion lymphoma and a subset of Castleman's disease. A recent polymerase chain reaction (PCR)-based study reported an association between KSHV and multiple myeloma (MM). We searched for KSHV infection in MM patients by serology, PCR and immunohistochemistry. In addition, we cultured dendritic and stromal cells from MM patients. KSHV antibodies were universally absent from MM patients (0/25) whereas EBV antibodies were nearly ubiquitous (24/25). All of the bone marrow biopsies (0/16) and negative controls (0/4) were vIL-6 negative. None of the bone marrow aspirates (0/6) or biopsies (0/3), peripheral blood mononuclear cells (0/8), mononuclear apheresis cells (0/5) or dendritic cell cultures (0/5) were positive by PCR. One of the MM stromal cell cultures (1/7) was positive for KSHV DNA by PCR and weakly positive on direct southern hybridization using a probe to the terminal repeat region. However, this same patient was PCR negative using another primer set, KSHV seronegative, and negative for vIL-6 immunostaining. Our results suggest that the KSHV DNA positivity rate among MM patients is much lower than previously reported.