Proteomic analysis of MCF-7 breast cancer cell line exposed to leptin

Background: Obesity is a well-known factor risk for breast cancer in postmenopausal women. Circulating leptin levels are increased in obese and it has been suggested to play an important role in mammary tumor formation and progression. To contribute to the understanding of the molecular mechanisms underlying leptin action in breast cancer, our aim was to identify proteins regulated by leptin in MCF-7 human breast cancer cells. Methods: We used two-dimensional gel electrophoresis (2-DE) and matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) to identify proteins affected by leptin. Results: Thirty proteins were found differentially expressed in MCF-7 cells after 48 h leptin exposure. Proteins regulated by leptin included proteins previously implicated in breast cancer such as catechol-o-methyltransferase, cathepsin D, hsp27, serine/threonine-protein phosphatase and regulatory proteins of the Ras signaling pathway. Proteins involved in other cellular functions such as stress response, cytosqueleton remodeling and proteins belonging to ubiquitin-proteasome system, were also identified. Furthermore, leptin-treated cells showed a substantial uptake of the serum carrier proteins albumin and alpha-2-HS-glycoprotein. Conclusions: This screening reveals that leptin influences the levels of key proteins involved in breast cancer which opens new avenues for the study of the molecular mechanisms linking obesity to breast cancer.

17β-Estradiol regulates oxidative stress in prostate cancer cell lines according to ERalpha/ERbeta ratio

Estrogen action is mediated by the two receptor isoforms: estrogen receptor alpha and beta. Both receptors are expressed in human prostate tissue and have different action profiles. ERalpha is positively correlated with the malignancy of prostate cancer, while ERbeta may protect against abnormal prostate cell growth. 17β-Estradiol (E2), at least in part, induces cancerous transformations by causing deleterious mutations through the formation of reactive oxygen species (ROS). The aim was to study the effect of E2 on oxidative stress and the expression of uncoupling proteins (UCPs) and antioxidant enzymes in several prostate cancer cell lines with different ERalpha/ERbeta ratios. The cell prostate lines with a lower ERalpha/ERbeta ratio had lower oxidative stress, which could be partially explained by the increased expression of antioxidant enzymes and UCPs. Moreover, the action of E2 on the expression of antioxidant enzymes and UCPs was dual and dependent on the ERalpha/ERbeta ratio. Treatments with 0.1 nM E2 in cell lines with high ERalpha/ERbeta ratio produced a decrease in antioxidant enzymes and UCPs levels, with an increase in ROS production. These effects disappeared when the treatment was done in the presence of an ERalpha antagonist (MPP). In the cell lines with greatest levels of ERbeta and the lowest ERalpha/ERbeta ratio, E2 treatment caused the up-regulation of antioxidant enzymes and UCPs with a look-up decrease in ROS production. These effects were reversed when the cells were treated with E2 in the presence of an ERbeta antagonist (R,R-THC). On the whole, our results suggest a dual E2 effect; increasing or decreasing oxidative stress in part by modulation of UCPs and antioxidant enzymes according to the abundance ERbeta and ERalpha/ERbeta ratio in prostate cancer cell lines.

RENAL DAMAGE FOLLOWING THE INGESTION OF A DIET CONTAINING AN EXCESS OF INORGANIC PHOSPHATE

The addition of an excess of inorganic phosphate in the form of orthophosphoric acid, acid, basic or neutral sodium or potassium phosphate to the diet of albino rats results in the development of an interesting and permanent renal lesion. The phosphate renal lesion is characterized by a necrosis of the cells of the convoluted tubules commencing at the terminal end, followed by a regeneration of atypical epithelium and calcification of the necrotic debris that fills the tubules. The entire outer stripe of the outer zone of the medulla is transformed into a zone of distorted structures and there is an increase in the interstitial connective tissue. The adjoining cortex is also involved with cystic dilatation of tubules and collapse. Such areas may reach the free surface of the organ and produce a retracted scar. In the gross the kidneys are enlarged and firm on section with a pebbled surface produced by numerous scars. The maximum changes in the kidney structure are reached after some 15 days although necrosis of the convoluted tubule cells is evident after a single day of phosphate feeding. The renal structure is not restored to its normal form when the excess of phosphate is removed from the diet.

DETERMINATION OF THE QUANTITY OF SECRETING TISSUE IN THE LIVING KIDNEY

1. Under the strain induced by the administration of urea, it is possible to demonstrate the relation between the degree of anatomical damage in the kidney and the degree of defect in the urea-excreting capacity induced by uranium. 2. The closest correlation between structure and function was obtained when the ratio between the urea content of the urine and of the blood was used as the measure of function.

EXPERIMENTAL NEPHRITIS IN THE FROG : II. PERFUSION METHODS OF TESTING THE KIDNEY BY DISSOCIATION OF ITS FUNCTIONS

1. A method of testing the frog's kidney by means of perfusion is described. 2. This is made possible by dissociating, as far as possible, from the total function of the organ the functions of its constituent parts. 3. The characteristics by which tubular, glomerular, and combined tubular-glomerular lesions may be recognized are described.

EXPERIMENTS ON THE PRODUCTION OF SPECIFIC ANTISERA FOR INFECTIONS OF UNKNOWN CAUSE : II. THE PRODUCTION OF A SERUM EFFECTIVE AGAINST THE AGENT CAUSING A CHICKEN SARCOMA

By the method of selective absorption with tissue, protective serum antibodies have been demonstrated in the case of an infection of unknown cause; namely, a chicken sarcoma transmitted by a filterable agent. Geese were repeatedly injected with the finely ground sarcoma and with blood from fowls moribund of it; and their sera acquired the power to prevent the tumor-producing agent from causing growths. That this was not due to antibodies elicited by the chicken tissue as such was shown by exhaustion of the goose sera with chicken red cells, a step which had not the least effect on the tumor-preventing power, and also by experiments with rabbits immunized as were the geese. These animals developed strong chicken antibodies in their sera which failed nevertheless to affect the tumor-producing agent. Serum immunity to the chicken sarcoma is weak at best; and in the case of some other infections of unknown cause, more striking results may be anticipated from the method of selective absorption. It is even conceivable that by its means sera of therapeutic usefulness may become available. But much remains to be settled as regards the dangers of exhausted sera and the limitations of the method. Fortunately there exists an immediate field for the latter in laboratory studies on the nature of immunity to infections of which the cause has not been recognized.

THE HISTOGENESIS OF CHRONIC URANIUM NEPHRITIS WITH ESPECIAL REFERENCE TO EPITHELIAL REGENERATION

1. Proliferation of connective tissue in chronic uranium nephritis is early and progressive and due to a direct stimulation on the part of the uranium. 2. The hydronephrotic theory fails to explain the phenomena observed in the progress of the chronic nephritis. 3. Carmine is deposited, as shown by Suzuki, in the proximal convoluted tubule only, and in different amounts in different levels of this segment of the tubule, so that subdivisions may be made. 4. Regeneration begins about the fourth day, but varies in proportion to the dose of renal irritant given. 5. The first cells to appear are large vesicular elements, and there is a gradual development of syncytium-like masses and giant-cells. These last are due to the rapidity of cell division. 6. Small, deeply staining nuclei, which are morphologically identical with the newly regenerated cells described by Thorel and others, are present from the first day of the acute nephritis and are persisting renal cells which have been slightly affected by the toxic agent.

EXPERIMENTS ON THE PRODUCTION OF SPECIFIC ANTISERA FOR INFECTIONS OF UNKNOWN CAUSE : I. TYPE EXPERIMENTS WITH KNOWN ANTIGENS-A BACTERIAL HEMOTOXIN (MEGATHERIOLYSIN), THE PNEUMOCOCCUS, AND POLIOMYELITIC VIRUS

Attempts to produce antisera in animals to combat specific infections are usually deferred until the cause of the infection has been isolated and grown in pure culture to furnish antigen. It has seemed to us that the fulfillment of these conditions might in some cases be rendered unnecessary through the use of infected tissue itself as an antigen, combined with selective absorption of the antiserum to rid it of elements injurious to the species furnishing the tissue. In order to test this possibility type experiments have been carried out with immune sera effective against known antigens of three different sorts: 1. Sera resulting from the injection of rabbits and a goat with normal guinea pig tissues and a bacterial hemotoxin, the megatheriolysin described by Todd, which hemolyzes guinea pig cells. The sera possessed strong antitoxins for the megatheriolysin but were fatal to guinea pigs. By the method of selective absorption they were rendered innocuous to these animals and were successfully used to protect them from lethal doses of the megatheriolysin. 2. Anti-rabbit dog sera containing antibodies protective against pneumococcus infection. Such sera, subjected to repeated absorption with rabbit red cells, proved capable of protecting mice from pneumococcus infection in exactly the same degree as the unexhausted serum; that is to say, they protected against 100 times the dose of pneurnococci that was fatal with normal dog serum. 3. The serum of a monkey recovered from poliomyelitis and repeatedly injected with human red cells and extract of placental tissue. This serum, after selective absorption with human red cells, protected a monkey against an intracerebral dose of poliomyelitic virus fatal to eight other monkeys given it with normal monkey or human serum. The results in these instances, purposely chosen for their simplicity, would seem to indicate for the absorption method some usefulness in the study of immunity to infections of unknown cause. In Part II of our paper the method is applied to one such infection; namely, a sarcoma of the fowl engendered by a filterable agent. A general discussion will be found in connection with this portion of the work.

A FURTHER STUDY OF THE REGENERATED EPITHELIUM IN CHRONIC URANIUM NEPHRITIS. AN ANATOMICAL INVESTIGATION OF ITS FUNCTION

1. Definite morphological changes occur in the batonnets of the proximal convoluted tubule in stages of activity. 2. Atypical mitochondria but no batonnets exist in the regenerated cells found in chronic uranium nephritis. 3. No secretion of urea occurs in these cells which do not contain the cell organs. 4. The urea is secreted normally in the proximal convoluted tubule only (Leschke). 5. The urea appears in the form of granules, which are arranged in definite rows. 6. It is suggested that the secretion of the urea is by means of the mitochondrial batonnets which act as condensors.

EXPERIMENTAL NEPHRITIS IN THE FROG : III. THE EXTRAVITAL PRODUCTION OF ANATOMICAL LESIONS IN THE KIDNEY AND THEIR CORRELATION WITH THE FUNCTIONAL ASPECTS OF DAMAGE

1. It is possible to produce in the perfused frog's kidney an experimental nephritis which is anatomically similar to that which develops in the living animal. 2. The functional effects of these anatomical alterations may be examined by a method previously described. 3. The correlation of the two aspects of damage, anatomical and functional, is more certain under such conditions than in the living animal. 4. The value of the extravital method in general problems is indicated by our brief consideration of mitochondrial changes.

A MECHANISM OF CONSERVATION IN THE KIDNEYS OF THE WINTER FROG

1. A method of conservation has been demonstrated in the kidneys of winter frogs. 2. The mechanism of this conservation is an increase in the absorptive function and a decrease in the excretory activity of the tubular epithelium. 3. The excessive absorptive process may be depressed by various means. Such a depression in the tubular activity is followed by large increases in the rate of excretion of water, salts and, if present in the urine, phenol red. 4. Further evidence is thus obtained which supports the theory that phenol red is excreted chiefly through the glomeruli.

EXPERIMENTS ON THE PRODUCTION OF SPECIFIC ANTISERA FOR INFECTIONS OF UNKNOWN CAUSE : III. THE EFFECTS OF A SERUM PRECIPITIN ON ANIMALS OF THE SPECIES FURNISHING THE PRECIPITINOGEN

There is present in serum of high precipitin titer, produced by the repeated injection of rabbits with the blood-free serum of guinea pigs or dogs, a principle highly toxic for animals of the species furnishing the antigen. Intravenously the serum causes severe shock, and even sudden death, while locally it gives rise to acute inflammatory changes and profuse capillary hemorrhages. The complete removal of hemolysins and hemagglutinins from the serum by exposing it repeatedly to washed red cells lessens its toxicity to only a slight degree and one obviously dependent on these elements; while the further removal of precipitin by specific precipitation in vitro has no detoxifying effect whatever. Whether the toxic principle is a hitherto unrecognized antibody or perhaps a toxic product of the interaction of precipitin and precipitinogen,—one formed as readily in the test-tube as in the animal body,—remains to be determined. The symptoms of guinea pigs and dogs given an intravenous injection of treated or untreated serum markedly resemble those of anaphylaxis, but our attempts at desensitization have been unsuccessful. The local lesion in guinea pigs is more severe than that of the Arthus phenomenon. But these differences from anaphylaxis may, of course, be dependent merely on differing proportions of constituents that are themselves, as yet, scarcely apprehended. Our observations, as here summed up, were made with a practical point in mind, and as regards this point they are of a discouraging nature. In papers already published it has been shown that sera specifically effective against infections of which the excitant is unknown can in some cases be obtained by using infected tissue itself as antigen. Such sera must, of course, be deprived of antibodies injurious to tissue, prior to their employment in the animal body; and this was successfully accomplished in our early experiments by exhaustion with washed red cells. The purpose of the present work was to determine whether serum used as antigen gives rise to injurious principles in the antiserum. For the serum of infected individuals would in many diseases form a convenient antigen. It is evident that injurious principles result from its use, and that they are not removed from the antiserum when the latter is exhausted with red cells and its precipitin removed by specific precipitation, nor can their action be nullified by desensitization as carried out in anaphylaxis. Unless the obstacle of their presence is in some way overcome the body fluids of infected human beings cannot be practically utilized for the production of antiserum. In test animals the difficulty is not so grave. For we have found that the toxic antiserum produces no enduring lesions when it is administered intravenously in non-lethal doses.

ON THE ORIGIN OF HEPARIN : AN EXAMINATION OF THE HEPARIN CONTENT AND THE SPECIFIC CYTOPLASMIC PARTICLES OF NEOPLASTIC MAST CELLS

1. The spontaneous mast cell tumor of the dog contains heparin. 2. The cytoplasmic particulate content of the tumor mast cells varies with their anaplasia. This conclusion is based on the following findings: (a) in the immature cell of the more malignant tumor the particulate matter appeared in the living cells by phase microscopy to be composed of greyish illdefined particles or as a fine, weakly metachromatic granulation in the fixed and stained preparation; (b) in the mature cells of a relatively benign mast cell tumor, both in the living cell and in stained preparations, the particulate matter occurred in the form of discrete, dense, and strongly metachromatic granules, resembling those of the normal mast cell. 3. The heparin content was large (fifty times that of dog liver) in the growth with mature cells and only moderate (1.7 times) in that with immature cells. 4. Since there may be a great amount of greyish particulate matter (or fine stained granules) in a tumor of relatively low heparin content, it is suggested that this material represents an early or precursor phase in the development of heparin. 5. This possibility and the fact that the blood stream may be invaded by mature tumor mast cells of large heparin content without evident disturbance in the coagulability of the blood suggest the value of a comprehensive biochemical study of the heparin of mast cell tumors.

STRUCTURAL AND FUNCTIONAL TRANSFORMATIONS IN THE TUBULAR EPITHELIUM OF THE DOG'S KIDNEY IN CHRONIC BRIGHT'S DISEASE AND THEIR RELATION TO MECHANISMS OF RENAL COMPENSATION AND FAILURE

1. The wall of the proximal convolution in chronic canine nephritis is composed of various types of epithelial cells which can be recognized as definite structural types from their cytological characteristics. 2. The function of these cell types, as tested by their reaction to the administration of trypan blue, varies with their structural constitution. 3. As a result of the varied cellular content of its wall the abnormal proximal convolution handles trypan blue by mechanisms which differ both quantitatively and qualitatively from those of the normal convolution. 4. A distinguishing characteristic of the decompensated kidney in chronic canine nephritis is the inability of its epithelium to concentrate trypan blue within its cells and to prevent diffusion of the dye from the lumen into the tubule wall. 5. It follows: (a) (from conclusion 3), that it cannot be assumed that the renal mechanisms concerned with other substances are not unaltered and that comparisons of blood and urine concentrations (clearances) have similar significance in the normal and nephritic kidney; (b) (from conclusion 4), that tubular dysfunction may play a part in the ultimate failure of the compensating kidney in all forms of chronic Bright's disease where the tubule walls are similarly affected.