Investigating the mechanism of enhanced cytotoxicity of HPMA copolymer-Dox-AGM in breast cancer cells

Recently we have described an HPMA copolymer conjugate carrying both the aromatase inhibitor aminoglutethimide (AGM) and doxorubicin (Dox) as combination therapy. This showed markedly enhanced in vitro cytotoxicity compared to the HPMA copolymer-Dox (FCE28068), a conjugate that demonstrated activity in chemotherapy refractory breast cancer patients during early clinical trials. To better understand the superior activity of HPMA copolymer-Dox-AGM, here experiments were undertaken using MCF-7 and MCF-7ca (aromatase-transfected) breast cancer cell lines to: further probe the synergistic cytotoxic effects of AGM and Dox in free and conjugated form; to compare the endocytic properties of HPMA copolymer-Dox-AGM and HPMA copolymer-Dox (binding, rate and mechanism of cellular uptake); the rate of drug liberation by lysosomal thiol-dependant proteases (i.e. conjugate activation), and also, using immunocytochemistry, to compare their molecular mechanism of action. It was clearly shown that attachment of both drugs to the same polymer backbone was a requirement for enhanced cytotoxicity. FACS studies indicated both conjugates have a similar pattern of cell binding and endocytic uptake (at least partially via a cholesterol-dependent pathway), however, the pattern of enzyme-mediated drug liberation was distinctly different. Dox release from PK1 was linear with time, whereas the release of both Dox and AGM from HPMA copolymer-Dox-AGM was not, and the initial rate of AGM release was much faster than that seen for the anthracycline. Immunocytochemistry showed that both conjugates decreased the expression of ki67. However, this effect was more marked for HPMA copolymer-Dox-AGM and, moreover, only this conjugate decreased the expression of the anti-apoptotic protein bcl-2. In conclusion, the superior in vitro activity of HPMA copolymer-Dox-AGM cannot be attributed to differences in endocytic uptake, and it seems likely that the synergistic effect of Dox and AGM is due to the kinetics of intracellular drug liberation which leads to enhanced activity. (c) 2006 Elsevier B.V All rights reserved.

Antitumor activity of Titanocene Y against freshly explanted human breast tumor cells and in xenografted MCF-7 tumors in mice

Bis-[(p-methoxybenzyl)cyclopentadienyl] titanium dichloride, better known as Titanocene Y, is a newly synthesized transition metal-based anticancer drug. We studied the antitumor activity of Titanocene Y with concentrations of 2.1, 21 and 210 mu mol/l against a freshly explanted human breast cancer, using an in-vitro soft agar cloning system. The sensitivity against Titanocene Y was highly remarkable in the breast cancer tumor in the full concentration range. Titanocene Y showed cell death induction at 2.1 mu mol/l, well comparable to cisplatin, given at a concentration of 1.0 mu mol/l. A further preclinical development of Titanocene Y was warranted and therefore an MCF-7 human breast cancer xenograft nonobese diabetic/severe combined immunodeficient mouse model was used. Titanocene Y was given for 21 days at 30 mg/kg/ day (75% of the maximum tolerable dose of Titanocene Y), which resulted in the reduction of the tumor volume to around one-third, whereas no mouse was lost because of the surprisingly low toxicity of Titanocene Y.

Objects and positions in visual scenes: effects of perirhinal and postrhinal cortex lesions in the rat

The authors assessed rats' encoding of the appearance or egocentric position of objects within visual scenes containing 3 objects (Experiment 1) or I object (Experiment 2A). Experiment 2B assessed encoding of the shape and fill pattern of single objects, and encoding of configurations (object + position, shape + fill). All were assessed by testing rats' ability to discriminate changes from familiar scenes (constant-negative paradigm). Perirhinal cortex lesions impaired encoding of objects and their shape; postrhinal cortex lesions impaired encoding of egocentric position, but the effect may have been partly due to entorhinal involvement. Neither lesioned group was impaired in detecting configural change. In Experiment 1, both lesion groups were impaired in detecting small changes in relative position of the 3 objects, suggesting that more sensitive tests might reveal configural encoding deficits.

Effects of vitamin E and fish oil inclusion in broiler diets on meat fatty acid composition and on the flavour of a composite sample of breast meat

BACKGROUND: Enriching poultry meat with long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) can increase low population intakes of LC n-3 PUFA, but fishy taints can spoil reheated meat. This experiment determined the effect of different amounts of LC n-3 PUFA and vitamin E in the broiler diet on the fatty acid composition and sensory characteristics of the breast meat. Ross 308 broilers (120) were randomly allocated to one of five treatments from 21 to 42 days of age. Diets contained (g kg−1) 0, 9 or 18 LC n-3 PUFA (0LC, 9LC, 18LC), and 100, 150 or 200 mg LD--tocopherol acetate kg−1 (E). The five diets were 0LC100E, 9LC100E, 18LC100E, 18LC150E, 18LC200E, with four pens per diet, except 18LC100E (eight pens). Breast meat was analysed for fatty acids (uncooked) and sensory analysis by R-index (reheated). RESULTS: LC n-3 PUFA content (mg kg−1 meat) was 514 (0LC100E) and 2236 (9LC and 18LC). Compared with 0LC100E, meat from 18LC100E and 18LC150E tasted significantly different, while 23% of panellists detected fishy taints in 9LC100E and 18LC200E. CONCLUSION: Chicken meat can be enriched with nutritionally meaningful amounts of LC n-3 PUFA, but > 100 mg dl--tocopherol acetate kg−1 broiler diet is needed to protect reheated meat from oxidative deterioration. Copyright © 2010 Society of Chemical Industry

Examination of faecal Bifidobacterium populations in breast- and formula-fed infants during the first 18 months of life.

Bifidobacteria in the infant faecal microbiota have been the focus of much interest, especially during the exclusive milk-feeding period and in relation to the fortification of infant formulae to better mimic breast milk. However, longitudinal studies examining the diversity and dynamics of the Bifidobacterium population of infants are lacking, particularly in relation to the effects of weaning. Using a polyphasic strategy, the Bifidobacterium populations of breast- and formula-fed infants were examined during the first 18 months of life. Bifidobacterium-specific denaturing gradient gel electrophoresis demonstrated that breast-fed infants harboured greater diversity than formula-fed infants and the diversity of the infants' Bifidobacterium populations increased with weaning. Twenty-seven distinctive banding profiles were observed from ∼1100 infant isolates using ribosomal intergenic spacer analysis, 14 biotypes of which were confirmed to be members of the genus Bifidobacterium. Two profiles (H, Bifidobacterium longum subsp. infantis; and I, Bifidobacterium bifidum) were common culturable biotypes, seen in 9/10 infants, while profile E (Bifidobacterium breve) was common among breast-fed infants. Overall, inter- and intra-individual differences were observed in the Bifidobacterium populations of infants between 1 and 18 months of age, although weaning was associated with increased diversity of the infant Bifidobacterium populations. Breast-fed infants generally harboured a more complex Bifidobacterium microbiota than formula-fed infants.

In vitro immunomodulatory activity of Lactobacillus fermentum CECT5716 and Lactobacillus salivarius CECT5713: two probiotic strains isolated from human breast milk

Commensal bacteria, including some species of lactobacilli commonly present in human breast milk, appear to colonize the neonatal gut and contribute to protection against infant infections, suggesting that lactobacilli could potentially modulate immunity. In this study, we evaluated the potential of two Lactobacillus strains isolated from human milk to modulate the activation and cytokine profile of peripheral blood mononuclear cell (PBMC) subsets in vitro. Moreover, these effects were compared to the same probiotic species of non-milk origin. Lactobacillus salivarius CECT5713 and Lactobacillus fermentum CECT5716 at 105, 106 and 107 bacteria/mL were co-cultured with PBMC (106/mL) from 8 healthy donors for 24 h. Activation status (CD69 and CD25 expressions) of natural killer (NK) cells (CD56+), total T cells (CD3+), cytotoxic T cells (CD8+) and CD4+ T cells was determined by flow cytometry. Regulatory T cells (Treg) were also quantified by intracellular Foxp3 evaluation. Regarding innate immunity, NK cells were activated by addition of both Lactobacillus strains, and in particular, the CD8+ NK subset was preferentially induced to highly express CD69 (90%, p<0.05). With respect to acquired immunity, approximately 9% of CD8+ T cells became activated after co-cultivation with L. fermentum or L salivarius. Although CD4+ T cells demonstrated a weaker response, there was a preferential activation of Treg cells (CD4+CD25+Foxp3+) after exposure to both milk probiotic bacteria (p<0.05). Both strains significantly induced the production of a number of cytokines and chemokines, including TNFα, IL-1β, IL-8, MIP-1α, MIP-1β, and GM-CSF, but some strain-specific effects were apparent. This work demonstrates that L salivarius CECT5713 and L. fermentum CECT5716 enhanced both natural and acquired immune responses, as evidenced by the activation of NK and T cell subsets and the expansion of Treg cells, as well as the induction of a broad array of cytokines.

Differential effects of overexpression of ERalpha and ERbeta in MCF10A immortalised, non-transformed human breast epithelail cells

Background: Cellular effects of oestrogen are mediated by two intracellular receptors ERα and ERβ. However, to compare responses mediated through these two receptors, experimental models are needed where ERα and ERβ are individually stably overexpressed in the same cell type. Methods: We compared the effects of stable overexpression of ERα and ERβ in the MCF10A cell line, which is an immortalised but non-transformed breast epithelial cell line without high endogenous ER expression. Results: Clones of MCF10A cells were characterised which stably overexpressed ERα (10A-ERα2, 10A-ERα13) or which stably overexpressed ERβ (10A-ERβ12, 10A-ERβ15). Overexpression of either ERα or ERβ allowed induction of an oestrogen-regulated ERE-LUC reporter gene by oestradiol which was not found in the untransfected cells. Oestradiol also increased proliferation of 10A-ERα13 and 10A-ERβ12 cells, but not untransfected cells, by 1.3-fold over 7 days. The phytoestrogen, genistein, which is reported to bind more strongly to ERβ than to ERα, could induce luciferase gene expression from an ERE-LUC reporter gene at concentrations of 10−6 M and 10−5 M but only in the clones overexpressing ERβ and not in those overexpressing ERα. Clone 10A-ERβ12 also yielded growth stimulation with 10-6 M genistein. Finally, the overexpression of ERα, but not ERβ, gave rise to increased growth in semi-solid methocel suspension culture in the presence of 70 nM oestradiol, suggesting that overexpression of ERα, but not ERβ, produces characteristics of a transformed phenotype. Conclusions: This provides a model system to compare effects of oestradiol with other oestrogenic ligands in cells stably overexpressing individually ERα or ERβ.

Environmental oestrogens and breast cancer: evidence for combined involvement of dietary, household and cosmetic xenoestrogens

Many environmental compounds with oestrogenic activity are measurable in the human breast and oestrogen is a known factor in breast cancer development. Exposure to environmental oestrogens occurs through diet, household products and cosmetics, but concentrations of single compounds in breast tissue are generally lower than needed for assayable oestrogenic responses. Results presented here and elsewhere demonstrate that in combination, chemicals can give oestrogenic responses at lower concentrations, which suggests that in the breast, low doses of many compounds could sum to give a significant oestrogenic stimulus. Updated incidence figures show a continued disproportionate incidence of breast cancer in Britain in the upper outer quadrant of the breast which is also the region to which multiple cosmetic chemicals are applied. CONCLUSION: If exposure to complex mixtures of oestrogenic chemicals in consumer products is a factor in breast cancer development, then a strategy for breast cancer prevention could become possible.

Enhanced sensitivity to rapamycin following long-term oestrogen deprivation in MCF-7, T-47-D and ZR-75-1 human breast cancer cells

Human breast cancer cells (MCF-7, T-47-D and ZR-75-1) can adapt to circumvent any reduced growth rate during long-term oestrogen deprivation, and this provides three model systems to investigate mechanisms of endocrine resistance in breast cancer. In this paper we report consistent differences in the effects of three growth inhibitors following long-term oestrogen deprivation in all three cell models. Long-term oestrogen deprivation of MCF-7, T-47-D and ZR-75-1 cells resulted in reduced growth inhibition by PD98059 (2–10 µg/ml), implying a loss of dependence on mitogen-activated protein kinase pathways for growth. The growth inhibitor LY294002 (2–10 µM) inhibited growth of both oestrogen-maintained and oestrogen-deprived cells with similar dose–responses, implying continued similar dependence on phosphoinositide 3-kinase (PI3K) pathways with no alteration after adaptation to oestrogen independent growth. However, by contrast, long-term oestrogen deprivation resulted in an increased sensitivity to growth inhibition by rapamycin, which was not reduced by readdition of oestradiol. The enhanced inhibition of long-term oestrogen-deprived MCF-7-ED, T-47-D-ED and ZR-75-1-ED cell growth by combining rapamycin with LY294002 at concentrations where each alone had little effect, offers preclinical support to the development of therapeutic combinations of rapamycin analogues with other PI3K inhibitors in endocrine-resistant breast cancer.

Fatty acid compositions of inositol and choline phospholipids of breast tumours and normal breast tissue

The fatty acid compositions of the -choline and -inositol phospholipids of breast tumours of women undergoing surgery for treatment of breast disease (malignant n = 12; benign n = 10) and normal breast tissue of women undergoing breast reduction surgery (n = 6) were determined. The fatty acid compositions of erythrocyte phospholipids were also determined in the same subjects and in an additional number of normal healthy volunteers (n = 16). Levels of oleic acid were lower in both phospholipid fractions of erythrocytes of women with breast disease and in the phosphatidylcholine fraction of breast tumours compared with normal breast tissue. Significantly higher levels of linoleic acid were found in erythrocytes of tumour-bearing subjects and a similar trend was evident in the phosphatidylcholine fraction of tumour compared with normal breast tissues. Conversely, lower levels of two of the products of linoleic acid chain elongation and desaturation, dihomogamma-linolenic and arachidonic acids, were found in the erythrocyte phospholipids of tumour-bearing subjects and in the choline phospholipids of breast tumour tissues. These data suggest that in women with breast disease, there may be inhibition of 6-desaturase, and enhanced activity of 9-desaturase, enzymes which play an important role in determining membrane phospholipid fatty acid composition. This pattern of altered fatty acid composition characteristic of erythrocyte phospholipids of tumour-bearing subjects and phosphatidylcholine of breast tumour tissue was less evident in the case of the breast tumour phosphatidylinositol in which differences other than those described were seen.

Exposure to environmental oestrogenic chemicals and breast cancer.

The human population is now exposed on a daily basis to a multitude of environmental pollutant chemicals that would not have been present a century ago, and many of these chemicals have been detected in the human breast. The fatty nature of human breast tissue makes it a particular target for lipophilic as well as hydrophilic pollutant chemicals, which may enter the human body through oral, respiratory, or dermal routes. These chemicals possess a range of endocrine-disrupting properties and genotoxic activity, but from a breast cancer perspective the greatest concern has centered around their ability to mimic or interfere with the action of estrogen. The breast is an endocrine target organ and exposure to estrogen is a known risk factor for breast cancer.

Analysis of aluminium content and iron homeostasis in nipple aspirate fluids from healthy women and breast cancer-affected patients

Aluminium is not a physiological component of the breast but has been measured recently in human breast tissues and breast cyst fluids at levels above those found in blood serum or milk. Since the presence of aluminium can lead to iron dyshomeostasis, levels of aluminium and iron-binding proteins (ferritin, transferrin) were measured in nipple aspirate fluid (NAF), a fluid present in the breast duct tree and mirroring the breast microenvironment. NAFs were collected noninvasively from healthy women (NoCancer; n = 16) and breast cancer-affected women (Cancer; n = 19), and compared with levels in serum (n = 15) and milk (n = 45) from healthy subjects. The mean level of aluminium, measured by ICP-mass spectrometry, was significantly higher in Cancer NAF (268.4 ± 28.1 μg l−1; n = 19) than in NoCancer NAF (131.3 ± 9.6 μg l−1; n = 16; P < 0.0001). The mean level of ferritin, measured through immunoassay, was also found to be higher in Cancer NAF (280.0 ± 32.3 μg l−1) than in NoCancer NAF (55.5 ± 7.2 μg l−1), and furthermore, a positive correlation was found between levels of aluminium and ferritin in the Cancer NAF (correlation coefficient R = 0.94, P < 0.001). These results may suggest a role for raised levels of aluminium and modulation of proteins that regulate iron homeostasis as biomarkers for identification of women at higher risk of developing breast cancer. The reasons for the high levels of aluminium in NAF remain unknown but possibilities include either exposure to aluminium-based antiperspirant salts in the adjacent underarm area and/or preferential accumulation of aluminium by breast tissues.

Plasma lipids and prolactin in patients with breast cancer

In a comparative study of pre- and postmenopausal women with benign and malignant breast disease, a number of differences were observed in circulating plasma prolactin and lipid concentrations. Plasma lipids, phospholipids, triglycerides, cholesterol and free fatty acids were all higher in blood obtained from breast cancer patients prior to surgery. HDL-Cholesterol levels were significantly lower in these patients. These differences remained when the patient groups were sub-divided according to menopausal status. Plasma prolactin concentrations were also found to be higher in cancer compared with non-cancer patients, this effect being more marked in premenopausal than in postmenopausal patients. Premenopausal patients with invasive or poorly differentiated disease had significantly higher prolactin levels than those with non-invasive disease. No correlations were found between plasma prolactin and any of the lipid fractions.