Epicardial adipocyte hypertrophy: Association with M1-polarization and toll-like receptor pathways in coronary artery disease patients

BACKGROUND AND AIMS

In coronary artery disease (CAD) epicardial adipose tissue (EAT) shows an elevated inflammatory infiltrate. Toll-like receptors (TLRs) are important mediators of adipose tissue inflammation and they are able to recognize endogenous products released by damaged cells. Because adipocyte death may be driven by hypertrophy, our aim was to investigate in CAD and non-CAD patients the association between EAT adipocyte size, macrophage infiltration/polarization and TLR-2 and TLR-4 expression.

METHODS AND RESULTS

EAT biopsies were collected from CAD and non-CAD patients. The adipocyte size was determined by morphometric analysis. Microarray technology was used for gene expression analysis; macrophage phenotype and TLRs expression were analyzed by immunofluorescence and immunohistochemical techniques. Inflammatory mediator levels were determined by immunoassays. EAT adipocytes were larger in CAD than non-CAD patients and do not express perilipin A, a marker of lipid droplet integrity. In CAD, EAT is more infiltrated by CD68-positive cells which are polarized toward an M1 state (CD11c positive) and presents an increased pro-inflammatory profile. Both TLR-2 and TLR-4 expression is higher in EAT from CAD and observed on all the CD68-positive cells.

CONCLUSIONS

Our findings suggested that EAT hypertrophy in CAD promotes adipocyte degeneration and drives local inflammation through increased infiltration of macrophages which are mainly polarized towards an M1 state and express both TLR-2 and TLR-4.

Sperm protein 17 is an oncofetal antigen: a lesson from a murine model

Sperm protein 17 (Sp17) was originally identified in the flagellum of spermatozoa and subsequently included in the subfamily of tumor-associated antigens known as cancer-testes antigens (CTA). Sp17 has been associated with the motility and migratory capacity in tumor cells, representing a link between gene expression patterns in germinal and tumor cells of different histological origins. Here we review the relevance of Sp17 expression in the mouse embryo and cancerous tissues, and present additional data demonstrating Sp17 complex expression pattern in this murine model. The expression of Sp17 in embryonic as well as adult neoplastic cells, but not normal tissues, suggests this protein should be considered an "oncofetal antigen." Further investigations are necessary to elucidate the mechanisms and functional significance of Sp17 aberrant expression in human adult cells and its implication in the pathobiology of cancer.

Abstract P6-08-01: Endothelial-Like Phenotype of Triple-Negative Breast Carcinoma Cells and Implications for New Molecular Targets

Background. Triple Negative Breast Cancers (TNBCs) still represent a question mark in breast cancer biology and a primary issue in clinics. A promising approach for an efficient targeted treatment of TNBCs seems to be represented by antiangiogenic therapies.

Methods. Effects of different compounds on proliferation of TNBC was evaluated in vivo and in vitro respectively by xenograft tumor volume analysis and SRB assay. Vasculogenic Mimicry (VM) properties were evaluated in vitro and in vivo respectively by tube formation assay and Transmission Electron Microscopy (TEM).

Results. Treatment of triple negative (TN) MDA-MB-231 xenografts with Sunitinib induced tumor regression, versus only a slight growth inhibition in tumors derived from MCF7 luminal cell line, whereas Bevacizumab determined only a modest decrease in tumor growth in both models. Accordingly, the efficacy of Sunitinib in blocking in vitro growth of breast cancer cell lines was higher in MDA-MB-231 cells in comparison with MCF7 cells (IC50 at 72h in MDA-MB-231 was 5 uM vs 25 uM in MCF7, as evaluated by SRB), and sensitivity to Bevacizumab was comparable between the two different cell lines. Investigating the undifferentiated nature of TNBCs, we observed that these tumors present an endothelial like phenotype and behavior, as supported respectively by the expression of endothelial markers, and the formation of vascular-like channels in vitro. In fact, all six TN cell lines evaluated (MDA-MB-231, MDA-MB-157, MDA-MB-468, BT-549, BT-20 and HCC1937) were able to form vascular channels when seeded on the murine tumor-derived basement membrane (Matrigel), whereas luminal (MCF7, T47D and ZR-75-1) and HER2- positive (MDA-MB-361, BT474 and SKBr3) breast carcinoma cell lines did not exhibit vascular structures. Then, we evaluated the VM in xenograft tumors derived from MDA-MB-231, MCF7 and MDA-MB-361 using transmission electron microscopy (TEM). MDA-MB-231 xenografts displayed channel-like structures formed by tumor cells encompassing erytrocytes, whereas in MCF7 and MDA-MB-361 xenografts the endothelial lining delimiting blood vessels was clearly visible. Notably, blood vessels surrounded by tumor cells were also identified in human TN specimens processed for TEM, and these structures were significantly more frequent in TN compared to non-TN tumors. 60% reduction in TN vascular channel formation in vitro by an anti-bFGF monoclonal antibody along with no effect using anti-VEGF antibody indicated that TN breast carcinoma cells can generate vascular channels through bFGF-mediated pathway. Silencing of different receptors involved in bFGF signal (i.e. FGFR2 and PDGFR β) abrogated VM in TN cells. Finally, TNBC cells able to perform vascular-like channels were found to express significantly higher (p= 0.003) levels of FGFR related genes, described associated with basal-like BC aggressiveness, compared to all the other tested cell lines. Conclusions. Our findings point to the possibility that TNBC cells are maintained by proangiogenic signals and that increased sensitivity to Sunitinib probably relies on the specific impairment of PDGFRβ and FGFR2-mediated pathways, which might represent a possible specific therapeutic target. Partially supported by AIRC and Italian Bureau of Health.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-08-01.

Toll-like receptor agonists regulate β-defensin 2 release in hair follicle

BACKGROUND

Skin is constantly in contact with different pathogens, which are present in the environment. The hair follicle is particularly susceptible to this microbial invasion as it offers an easy way of access for microorganisms; for this reason it is equipped with defence mechanisms to avoid frequent infections.

OBJECTIVES

To analyse the expression pattern of four different members of the toll-like receptor (TLR) family in murine hair follicles and to evaluate the effects of their activation by their specific microbiota-derived agonists, in terms of production of the antimicrobial peptide beta-defensin 2 (DEFB2).

METHODS

TLR and DEFB2 protein expression was investigated by immunohistochemistry on murine skin samples.

RESULTS

Murine hair follicle expresses TLR2, TLR4 and TLR5; agonists of TLR2, TLR4 and TLR5 but not of TLR9 induced DEFB2 production in this compartment. The strongest DEFB2 expression was observed following TLR4 activation by lipopolysaccharide.

CONCLUSIONS

Our data show that the hair follicle is equipped with TLR2, TLR4 and TLR5, and that these receptors are able to respond to microbial stimuli inducing the production of DEFB2 by epithelial cells. This immune response might be important in preserving the skin from microorganism infections.

Caveolin-1 is expressed on multipotent cells of hair follicles and might be involved in their resistance to chemotherapy

BACKGROUND

Caveolin-1 is the principal protein that composes caveolae, which are vesicular invaginations present on the plasma membrane of different cell types. Caveolae are involved in a variety of cellular functions including regulation of proliferation rate and resistance to chemotherapeutic drugs. Chemotherapy frequently induces alopecia which is reversible most probably due to the low proliferative rate of hair follicle stem cells and due to the expression of proteins which confer resistance.

OBJECTIVES

Using a specific animal model and immunohistochemistry, we analysed the expression of both caveolin-1 and the cell proliferation marker beta-catenin, at different stages of the hair follicle cycle, both before and after doxorubicin (DXR) -induced alopecia.

METHODS

Seven-week-old C57BL/6 mice were depilated in order to synchronize hair follicle cycle in the anagen phase. Chemotherapy with DXR 15 mg kg(-1) was used to induce alopecia. Control and treated mice were then sacrificed at precise time points and caveolin-1 expression in hairs at different stages of the cycle were analysed by immunohistochemistry. By double immunofluorescence, colocalization of caveolin-1 and cytokeratin-15 was confirmed in the bulge region. The state of proliferation of cells composing hair follicle was assessed by beta-catenin immunohistochemistry.

RESULTS

Caveolin-1 was expressed by the cells of the bulge area, the multipotent compartment of the hair follicle, during all phases of growth (anagen), regression (catagen) and resting (telogen). During the anagen phases, nuclear beta-catenin labelling was not observed in bulge cells, but rather in the deeper portion of the follicle. Damaged hair follicles from DXR-treated mice presented bulge cells which still expressed caveolin-1, suggesting that this protein might play a role in their drug resistance. As expected, no beta-catenin nuclear staining was detectable in DXR-treated hair follicles, indicating the complete lack of proliferative processes. The differential localization of caveolin-1 and beta-catenin suggests that the mutually exclusive expression of these proteins is useful for correct hair regrowth, whether during the physiological cycle or after chemotherapy-induced alopecia.

CONCLUSIONS

Expression of caveolin-1 within the multipotent cell compartment of the hair follicle can explain the resistance of bulge cells to many chemotherapeutics, suggested by the reversibility of chemotherapy-induced alopecia.