Zinc-alpha2-glycoprotein: a new biomarker of breast cancer?

BACKGROUND/AIM: Obesity increases the risk of breast cancer. It is established that adipocyte secretions, i.e. adipokines, may play a role in mammary carcinogenesis. We have shown that two major adipokines, leptin and adiponectin, were expressed in mammary adenocarcinoma. PATIENTS AND METHODS: Here, we evaluated zinc-alpha2-glycoprotein (ZAG) expression in tumor (n=55) and healthy (n=6) breast tissue by immunohistochemistry and examined whether it was correlated with that of major adipokines, usual tumor biomarkers (sex steroids receptors, i.e. estrogen (ER) and progesterone; Ki-67; cErb2), or apoptosis markers (Bcl2 and Bax). RESULTS: ZAG expression was detected in ductal carcinoma and normal epithelial adjacent tissue but not in normal tissue of healthy women. In cancer tissue, its expression was correlated positively to leptin receptor and negatively to adiponectin receptor and ER. CONCLUSION: These preliminary results suggest both a relationship between ZAG expression and pathways involving adipokines or estrogen and that ZAG may be a potential breast cancer biomarker.

Involvement of adiponectin and leptin in breast cancer: clinical and in vitro studies.

Obesity is a risk factor for breast cancer development. A recent hypothesis suggests that the adipokines, adiponectin and leptin, are involved in breast cancer development. This prompted us to investigate the role of adiponectin and leptin in mammary carcinogenesis. Adiponectin receptors (AdipoR1 and AdipoR2) and leptin receptor (Ob-Rt, representing all the isoforms of Ob-R) proteins were detected by immunohistochemistry in in situ ductal carcinoma, invasive ductal malignancy, and healthy adjacent tissue. In addition, mRNA expression of adiponectin, AdipoR1, AdipoR2, leptin, Ob-Rt, and Ob-Rl (the long isoform of Ob-R) was observed in MCF-7 breast cancer cells. Interestingly, leptin mRNA expression was 34.7-fold higher than adiponectin mRNA expression in the MCF-7 cell line. Moreover, adiponectin (10 microg/ml) tended to decrease the mRNA expression of leptin (-36%) and Ob-Rl (-28%) and significantly decreased Ob-Rt mRNA level (-26%). In contrast, leptin treatment (1 microg/ml) significantly decreased AdipoR1 mRNA (-23%). Adiponectin treatment (10 microg/ml) inhibited the proliferation of MCF-7 cells, whereas leptin (1 microg/ml) stimulated the growth of cancer cells. In addition, adiponectin inhibited leptin-induced cell proliferation (both 1 microg/ml). Using microarray analysis, we found that adiponectin reduced the mRNA levels of genes involved in cell cycle regulation (mitogen-activated protein kinase 3 and ATM), apoptosis (BAG1, BAG3, and TP53), and potential diagnosis/prognosis markers (ACADS, CYP19A1, DEGS1, and EVL), whereas leptin induced progesterone receptor mRNA expression. In conclusion, the current study indicates an interaction of leptin- and adiponectin-signaling pathways in MCF-7 cancer cells whose proliferation is stimulated by leptin and suppressed by adiponectin.

Potential anti-inflammatory effects of Melaleuca alternifolia essential oil on human peripheral blood leukocytes.

The fungicidal and bactericidal actions of the essential oil (EO) of Melaleuca alternifolia seem well established, but their anti-inflammatory and antioxidative effects remain unclear. This study investigated in vitro the possible role of whole Melaleuca alternifolia EO as a modulator of the inflammatory/non-specific immune response by exploring the chemotaxis and kinetic radical oxygen species (ROS) production of leukocytes and cytokine secretion in peripheral blood mononuclear cells (PBMCs) in humans. The influence of Melaleuca alternifolia EO on the chemotaxis under agarose of isolated neutrophils (PMNs) was evaluated. The kinetics of ROS production by stimulated total circulating leukocytes was followed over 2 h by recording the fluorescence intensity of oxidized dihydrorhodamine 123. The effects of this EO on pro-(interleukin IL-2) and anti-(IL-4 and IL10) inflammatory cytokine secretions were determined by ELISA following incubation of PBMCs with the EO for 24 h. Melaleuca alternifolia EO was inefficient on the chemotaxis of PMNs. It exerted an antioxidant effect, reducing ROS production throughout the kinetic study. Melaleuca alternifolia EO inhibited PBMC proliferation, as revealed by a reduction in IL-2 secretion by stimulated lymphocytes. This EO at 0.1% directly increased the secretion of the anti-inflammatory cytokine IL-4 compared with IL-4 secretion without EO (18.5 +/- 10.0 vs 3.3 +/- 1, p < 0.05), and also increased IL-10 secretion at 0.01% (94.9 +/- 38.7 vs 44.1 +/- 18, ns). Melaleuca alternifolia EO may not only act as an anti-inflammatory mediator through its antioxidant activity but may also efficiently protect the organism by reducing the proliferation of inflammatory cells without affecting their capacity to secrete anti-inflammatory cytokines.

Study of the expression of Tn antigen in different types of human breast cancer cells using VVA-B4 lectin.

VVA-B4 lectin was used to investigate the differences in Tn antigen expression in tissues of different types of human breast cancer (benign lesions, carcinoma in situ, invasive carcinoma) and in normal tissues neighboring lobular carcinoma. Locations in which Tn antigen was expressed were identified using the avidin-biotin-peroxidase labeling system. Tissues collected during cosmetic procedures and classified as normal were completely negative, except for one case. Benign proliferative changes including fibroadenoma, apocrine and cylindrical metaplasia showed a very weak positive reaction, although strongly positive cells were also observed. The reaction in non-invasive cases of atypical hyperplasia was diversified depending on site. Intralobular hyperplasia was characterized by a particularly high percentage of labeled cells. A majority (up to 80%) of ductal and lobular carcinoma in situ showed very strong or moderate staining. In invasive cancers, there were conspicuous differences between stage of cancer development and tendency towards a decrease in intensely labeled cell count in the most advanced stages. In normal tissues in the direct neighborhood of carcinoma in situ, the cytoplasm of 40% of cells was strongly labeled. However, the findings for normal tissues in the close vicinity of invasive cancer were the most surprising, since there was either no or only very weak positive reaction. It can be concluded that glycosylation modifications during carcinogenesis, as demonstrated by the presence of Tn epitope, develop very early, before any destructive changes in proliferation/apoptosis or cell differentiation become discernible.

Leptin: a proliferative factor for breast cancer? Study on human ductal carcinoma.

Mammary adipose tissue is an important source of paracrine mitogens and anti-mitogens, including insulin-like growth factor, transforming growth factors, and cytokines (especially, TNFalpha and IL-1beta). Nevertheless, it is also an important source of the adipocytokine, leptin. Recently, leptin was reported to stimulate the proliferation of various cell types (pancreatic beta cells, prostate, colorectal, lung, etc.) as a new growth factor. It was also shown to stimulate the proliferation of breast cancer cell lines. In this study, we conducted an immunohistochemical analysis of leptin expression in normal tissue and benign and malignant ductal breast cell, representing the different states of the invasion process. We determined for the first time that leptin is expressed both by ductal breast tumors and by benign lesions as atypical hyperplasia. This suggests that leptin may be taken up or synthesized by all modified ductal breast cells, and may prove a proliferative factor. Moreover, leptin is unexpressed by normal tissue in the healthy breast but is exhibited by the normal tissue in near vicinity of the malignant ductal breast lesions. We also postulated that leptin may be a prognostic or diagnostic factor for ductal breast cancer. These putative hypotheses require further study.

Troglitazone reduces leptinemia during experimental dexamethasone-induced stress.

BACKGROUND AND AIMS: Recently, we found that profound anorexia observed in a catabolic model induced by chronic glucocorticoid (dexamethasone, Dex) injection could be associated with strong hyperleptinemia. To investigate the implication of leptin in this catabolic stress response, we used a model whereby leptin secretion was inhibited using troglitazone (Trg) concomitantly with a Dex-induced-stress injection. METHODS: Adult rats (3 months, n=12) were stressed with a Dex injection (1.5 mg/kg/day ip, 5 days) and either treated (DXTG+, n=6) or not (DXTG-, n=6) with Trg (60 mg/kg/day sc, 5 days). These DXTG+ and DXTG- groups were compared with an untreated ad libitum group and a pair-fed group receiving saline ip instead of the Dex injection. The effects of troglitazone treatment on leptin gene expression in adipose tissue, blood glucose, insulin, and on hepatic parameters under stress conditions were determined. RESULTS: Trg treatment specifically diminished leptinemia (30%, DXTG+ vs DXTG-, p<0.05). Insulinemia and glycemia remained unchanged, as did leptin gene expression; food intake improved, but hepatic capacities did not show any alteration. CONCLUSION: Trg is a useful agent in exploring certain potential effects of leptin on metabolic and immune disorders occurring during aggression.

Anti-inflammatory effects of Melaleuca alternifolia essential oil on human polymorphonuclear neutrophils and monocytes.

OBJECTIVE AND DESIGN: The fungicidal and bactericidal actions of the essential oil (EO) of Melaleuca alternifolia seem well established, but their anti-inflammatory and anti-oxidative effects remain unclear. In this study, we investigated in vitro the possible role of whole M. alternifolia EO as a modulator of the oxidative response, i.e. reactive oxygen species (ROS) production, of leukocytes (monocytes and polymorphonuclear neutrophils (PMNs)) in humans. METHODS: Whole blood leukocytes from healthy human volunteers (n = 7), isolated from erythrocytes by haemolytic shock, were incubated for 30 min with M. alternifolia EO (0-0.1%) to determine their ROS production by flow cytometry with or without stimulation of cells. We compared the effects of 3 different stimulating agents acting differently on transductional pathways to stimulate the ROS production: a phorbol ester (PMA), formyl-methionyl-leucyl-phenylalanine (fMLP) and opsonised zymosan (OZ). RESULTS: As attested by the Krüskall-Wallis test, M. alternifolia EO at 0.1% directly stimulated ROS production by PMNs (x 8.7 vs. 0% EO, p < 0.05) and increased the intracellular ROS produced by monocytes. Whichever the stimulating agent used (PMA, fMLP or OZ), M. alternifolia EO decreased the intracellular ROS production at the dilution of 0.1% by PMNs and monocytes, more so with PMNs. CONCLUSION: M. alternifolia EO may be both a direct active mediator of the bactericidal action of the circulating leukocytes and may be efficient in protecting the organism from an excess of ROS, through an anti-oxidant and radical scavenging activity.

Leptin regulates functional capacities of polymorphonuclear neutrophils.

Recent studies report that leptin may be able to modulate some functions of cells involved in non-specific immune response. We recently found that a functional leptin receptor is present on polymorphonuclear neutrophils (PMNs) and may be able to influence their oxidative capacities. We demonstrate here for the first time that leptin is also able to stimulate chemotaxis of PMNs and exerts by itself a chemoattractive effect comparable to that of well-known formyl-methionyl-leucyl-phenylalanine, and a stimulating effect on intracellular hydrogen peroxide production, without modification of phagocytosis.

Dexamethasone treatment induces long-lasting hyperleptinemia and anorexia in old rats.

Aging brings poor adaptation to stress, the causes of which remain unclear. We previously reported impairment of nitrogen metabolism in glucocorticoid-treated old rats due to profound anorexia. Here we investigated whether leptin, a satiety hormone, was implicated in impaired adaptation to stress. Plasma glucose and insulin levels, which are known to modulate leptin secretion, were also studied. Adult (3 months, n = 18) and aged (24 months, n = 18) rats were treated with dexamethasone (DEX) (1.5 mg/kg/d, intraperitoneal [IP] injection) for 3, 5, and 7 days. Results were compared with ad libitum (n = 12) and pair-fed groups, receiving intraperitoneal saline injection, for each age (n = 6 per group). Transitory anorexia was observed in adult rats (day 3 to day 5), whereas anorexia persisted in aged rats until day 7. This anorexia was associated (r = -.65, P <.05) with an elevated constant hyperleptinemia. In contrast, hyperleptinemia was moderate and reverted rapidly to basal values by day 5 in adult rats. The time course of plasma insulin and glucose levels was similar in old and adult rats, except for marked hyperglycemia noted in aged animals. In old stressed rats, DEX treatment induces an anorexia, which is concomitant to an increase in serum leptin levels. Thus, leptin may be implicated in the poor adaptation to stress of aged compared with adult rats.

Leptin: a potential regulator of polymorphonuclear neutrophil bactericidal action?

It is well known that leptin, the ob gene product, is involved in the regulation of food intake and thermogenesis. Recent studies also demonstrate that leptin may be able to modulate functions of cells involved in nonspecific immune response such as phagocytosis and secretion of cytokines by macrophages. This and the prominent implication of polymorphonuclear neutrophils (PMNs) in infectious response suggested a possible role of leptin as a modulator of PMN functions. We detected a leptin receptor on the PMN membrane by immunocytochemistry with an anti-leptin receptor. Using chemiluminescence we then demonstrated that leptin enhances oxidative species production by stimulated PMNs. These results show for the first time that a functional leptin receptor is present on PMNs and that leptin may be able to influence their oxidative capacity.