Distribution of retinoic acid-binding proteins in normal and neoplastic mammary tissues

Cellular retinoic acid-binding proteins were detected in chemically induced mammary tumors using sucrose density gradient analysis. Unlabeled retinoic acid did not displace nonspecific binding in the 5S region but was, however, a competitive inhibitor for the specifically binding 2S component. Mammary gland cytosol fractions from both 1-methyl-1-nitrosourea-treated and untreated as well as from lactating rats contained low levels of retinoic acid-binding proteins. 1-Methyl-1-nitrosourea treatment did not result in the increased number of binding sites. Thus, the increase in the levels of binding proteins in tumors most probably occurred during tumor development and probably was not a result of the carcinogen per se. Retinoids which have been shown to be effective in the chemoprevention of mammary carcinogenesis only partially competed for the binding sites, indicating that they may be metabolized prior to their action as an active chemopreventive agent.     

Distribution of epidermal growth-factor receptors in normal and neoplastic mammary tissues

Epidermal growth factor (EGF) is considered to be mitogenic for proliferation of mammary glands in animals. The action of EGF is mediated by specific EGF receptors (EFG-R). In the present study, we investigated distribution of EGF receptors during various physiological stages of mammary glands, N-methyl-N-nitrosourea (MNU)-induced mammary tumors in rats and human breast cancer samples. EGF receptor concentrations were determined by Scatchard analyses in the membrane fraction of the tissues. Results showed increased EGF receptor levels in the structurally differentiated mammary tissues from pregnant rats; whereas lower concentrations were observed in the functionally differentiated glands from lactating rats. EGF receptors were absent in the majority of the tumors induced by MNU. The loss of EGF receptor was not observed during the first 20 days post carcinogen treatment, but appeared to be correlated with the onset of the tumor. Consistent with the literature, the majority of the steroid receptor positive human breast cancer samples were EGF receptor negative, whereas steroid receptor negative samples contained EGF receptors. These results suggest that the loss of EGF receptors in ovarian hormone dependent mammary tumors does not occur gradually during carcinogenesis but appears to be a characteristic of hormone dependent mammary tumor cells.     

Distribution of intracisternal A-particles in a variety of normal and neoplastic mouse tissues

Examination of various normal and neoplastic tissues reveals the presence of intracisternal A-particles in five strains of mice and their hybrids. Cell types derived from all three embryonic germ layers contain these particles, and their presence in gonadal tissue of both sexes suggests that vertical transmission can take place. Intracisternal A-particles are found in most of the tissues known to support the replication of mouse leukemia viruses and mammary tumor virus. Further, they have been shown to coexist in the same cell with C particles and intracytoplasmic A-particles (mammary tumor virus precursors). Although it has not been possible to demonstrate biological activity associated with intracisternal A-particles, there is the possibility that they represent the partial gene expression of one of the known oncogenic RNA viruses, and as such serve as a marker for an incomplete replication cycle.     

Extravascular diffusion in normal and neoplastic tissues

Extravascular transport of fluorescein isothiocyanate-conjugated bovine serum albumin and a graded series of fluorescein isothiocyanate-dextrans from Mr 19,400 to 71,800 were studied in both normal tissue (granulation) and tumor (VX2 carcinoma) grown in a rabbit ear chamber. Sodium fluorescein was used as a representative small molecule. A one-dimensional diffusion model adequately described extravascular transport in both normal and tumor tissue. Measured diffusion coefficients showed a relationship with molecular size which progressively deviates from that of free diffusion in water, with values for albumin being significantly reduced from that for a dextran of equivalent size. Macromolecular transport in tumor tissue was hindered to a lesser extent than in normal tissue, which is consistent with reports of reduced contents of glycosaminoglycans, and markedly large interstitial space in tumors. Diffusion coefficients for dextran were found to vary with molecular weight according to the expression, D = a(Mr)b, in both normal tissue (a = 10(6) and b = -2.96) and tumor (a = 2.51 X 10(-2) and b = 1.14).     

Distribution of the c-myc oncoprotein in normal and neoplastic tissues of the rat colon

A rat model of 5-azoxymethane induced colon cancer was studied in order to correlate histopathological changes and the differential distribution of the c-myc protein. Weanling Fisher 344 rats were injected with three, one week apart, subcutaneous injections of 5-azoxymethane (AOM) (15 mg kg-1) and the animals were divided into low and high fat diet groups. Nine colon tumors, of varying degrees of malignancy, that developed in the AOM-treated rats, and sections of normal colonic mucosa were examined. A rabbit polyclonal anti-c-myc antibody produced nuclear staining at 1:100 dilution in cryostat frozen sections of the normal rat colonic mucosa and the colon tumors when prepared with a Cryostat Frozen Sectioning Aid (CFSA). The tissue localization of the c-myc antibody staining revealed: (1) in normal mucosa, nuclei of the basal portion of the mucosa; (2) in adenomatous polyps, nuclei at all levels of the mucosa; and (3) in a carcinoma in situ, intense staining of glandular epithelial cell nuclei at all levels within the tumor. This procedure may provide a sensitive method for detecting abnormal cells in the colonic epithelium that have an altered proliferative capacity.     

Nuclear protein phosphokinases in normal and neoplastic tissues.

Protein phosphokinases were isolated from the nuclei of normal and fetal liver and neoplastic tissues. Chromatography on phosphocellulose columns resolved the normal and fetal liver kinases into five reproducible fractions. Each of the fractions differed in optimal divalent cation and substrate requirements. Hepatic proliferation was accompanied by quantitative changes in the kinase activity profiles (with endogenous phosphoprotein as natural substrate). An additional phosphoprotein kinase activity stimulated by Mn2+ was found in the nuclei of malignant cells. This tumor-specific kinase could not be detected either in tumor cytoplasm or in fetal or regenerating liver nuclei. Mn2+-dependent phosphoprotein kinase from Novikoff hepatoma phosphorylated only one major protein band detectable by polyacrylamide gel electrophoresis. This substrate could not be detected in chromatin of normal tissues.     

Distribution of epithelial membrane antigen in normal and neoplastic tissues and it value in diagnostic tumor pathology

An antiserum raised against human milk fat globule membranes has been used to stain a wide variety of human tissues by the indirect immunoperoxidase method. The antigen detected has been designated Epithelial Membrane Antigen and was confined to the luminal and surface membranes (and to a lesser extent the cytoplasm) of epithelial tissues in the normal state. Increased staining was observed in a variety of nonneoplastic disease states as well as in many neoplasms. The staining of tumors is related both to their histogenesis and degree of differentiation, being found only in lesions of surface epithelial or mesothelial origin and being more consistently present in well and moderately differentiated neoplasms. However, strong staining was also present in many anaplastic tumors and this together with the resistance of the antigen to formol fixation and paraffin embedding suggest that the antiserum has a valuable role to play in diagnostic tumor histopathology as an indicator of epithelial differentiation. The distinction of anaplastic carcinomas from malignant lymphomas and the recognition of spindle-cell epithelial malignancies are especially useful applications. The identification of minute metastatic deposits of carcinoma in organs such as the liver and bone marrow is also greatly facilitated. Malignant neoplasms often exhibit patterns of staining different from those of the normal tissues. The possible significance of these patterns is discussed.