Primary culture of human mammary epithelial cells embedded in collagen gels

Human mammary epithelial cells were dissociatd from mastectomy tissues. The contaminating fibroblasts were removed by the use of Percoll density-gradient centrifugation, which utilizes the difference in buoyant densities between epithelial cells and fibroblasts. A preparation highly enriched for mammary epithelial cells ws then embedded in collagen gel and cultured in Ham's F12 medium containing 12.5% horse serum, 2.5% fetal calf serum, 0.1 microgram cholera toxin/ml, an extract prepared from human male urine (L microgram protein/ml), and a hormone combination of 10 microgram insulin/ml, 10 microgram human placental lactogen/ml, 1 microgram aldosterone/ml, and 0.5 microgram hydrocortisone/ml. Sustained growth leading to an increase of tenfold to thirtyfold in cell number over the initial value was accomplished in primary culture, and this growth was maintained even after passage to secondary culture. Deletion of either the urine extract or the hormone combination resulted in less than optimal growth. Subsequent studies showed that hydrocortisone alone could replace the hormone combination. In addition, urine extract could be replaced by extracts prepared from human kidneys or brains. The collagen gel system provies a reproducible and consistent method for sustained three-dimensional growth of mammary epithelial cells from human breast tissue in primary as well as passaged cultures.

Growth factor- and cyclic nucleotide-induced proliferation of normal and malignant mammary epithelial cells in primary culture

Sustained growth of normal mouse mammary epithelial cells in primary culture, leading to an increase in cell number, in response to growth factors [epidermal growth factor (EGF) and fibroblast growth factor (FGF)] or cholera toxin has been achieved by embedding the cells inside collagen cells. Inclusion of agents known to increase the level of cellular cAMP have been found to be favorable for mammary epithelial cell proliferation. Cholera toxin is by far the best of all of the agents tested (prostaglandins E1 and E2, isoproterenol, theophylline, and dibutyryl cAMP). When growth factors (EGF or FGF) are added with cholera toxin, a synergistic effect resulting in a response much greater than with either of them alone is seen. This synergism was best seen in normal mammary epithelial cells from nonpregnant mice. The extent of this synergistic effect was found to be less in normal cells from pregnant mice, suggesting that these cells may be less responsive to EGF during pregnancy. Tumor cells were found to be rather inconsistent in their responses to EGF and cholera toxin, ranging from a minimal response, similar to that of normal cells from pregnant animals, to a maximal response, similar to that of normal cells from nonpregnant animals.

Primary culture of mouse mammary tumor epithelial cells embedded in collagen gels

Mammary tumor epithelial cells from BALB/cfC3H mice were dispersely embedded inside the collagen gels in Ham's F-12 medium containing horse serum. A sustained cell growth leading to a 5- to 10-fold increase in cell number over initial level was observed in less than 2 weeks. The extent of this growth was found to be dependent on serum concentration. However, addition of various protein and steroid hormones, both singly and in combination, to low-serum-containing medium failed to achieve a comparable level of growth to that promoted by higher serum concentration. Mammary tumor cells can now be consistently propagated in primary culture.

Sustained growth in primary culture of normal mammary epithelial cells embedded in collagen gels

Normal mammary epithelial cells from BALB/cfC3H midpregnant mice were freed from stromal cell types by Percoll density gradient centrifugation after collagenase digestion and were then embedded within collagen gels. Sustained growth leading to an increase in cell number was accomplished in response to cholera toxin and high concentrations of horse serum. The extent of growth was found to be dependent on the horse serum concentration, the maximum growth being attained at 50%. A serum concentration of 12.5% horse serum and 2.5% fetal calf serum, along with cholera toxin at 0.01 mug/ml, allowed maintenance but failed to cause any significant increase in cell number during the experimental period of 2 weeks. This same maintenance medium was used to determine the effects of various exogenously added steroids, protein hormones, and organ extracts on the proliferation of mammary epithelial cells in culture. Hormones failed to elicit any proliferative response, but extracts of kidney, brain, uterus, and spleen produced proliferative responses equal to or greater than the response obtained with 50% horse serum and cholera toxin. Kidney extracts prepared from midpregnant mice, virgin mice, and virgin mice given pituitary isografts all showed comparable activities, suggesting that the concentration of stimulatory factor(s) was not influenced by the hormonal status of the donor. Normal mammary epithelial cells that had undergone a 10- to 15-fold increase in cell number over initial values during 2-3 weeks in culture were passaged to secondary gel cultures. Outgrowth similar to those seen in primary culture were seen again in secondary culture. The present system provides a method for sustaining growth in culture of primary mammary epithelial cells from normal tissues.

Sustained growth and three-dimensional organization of primary mammary tumor epithelial cells embedded in collagen gels

We have developed a method for embedding cells within a collagen matrix which allows sustained growth of mouse mammary tumor epithelial cells in primary culture. A characteristic and reproducible pattern of organization and growth occurs: the cells rearrange themselves and produce duct-like structures extending into the matrix, resulting in a three-dimensional outgrowth. Autoradiography showed continuous [3H]thymidine incorporation during 8 weeks in culture. An increase in DNA content of the cultured cells as a function of time was observed. Mouse mammary tumor cells cultured in the conventional monolayer system failed to show any significant increase in cell number during a culture period of 6 weeks. In addition, in such monolayer systems, cells progressively became detached from the dishes in long-term culture. The mammary epithelial cell origin of the collagen gel cell outgrowths was shown by electron microscopic demonstration of polarized cells containing tight junctions and budding mammary tumor virus particles. In addition, in vivo transplantation of collagen gel outgrowths resulted in the development of mammary adenocarcinoma histologically similar to the donor tumor. Cellular outgrowth patterns resembling those from tumor cells were also seen in similar collagen gel cultures of normal mammary cells from mouse and human and of hyperplastic alveolar nodule cells from mouse. The significance and usefulness of this system in comparison to the conventional monolayer system are discussed.

Antibody-mediated activation of a defective beta-D-galactosidase: dimeric form of the activatable mutant enzyme

Sedimentation analyses of AMEF, an activatable mutant beta-D-galactosidase (beta-D-galactoside galactohydrolase, EC 3.2.1.23), and the products of its reaction with Fab fragments of activating antibody show that this enzyme exists mainly as 10S dimers. Activation of AMEF by purified antibody resulted in formation of 16S tetramers. A unifying hypothesis postulating a dimer--tetramer equilibrium accounts for this observation as the counterpart of inactivation, which was shown to involve the breakdown of tetramers into inactive subunits [Roth, R. A. & Rotman, B. (1975) Biochem. Biophys. Res. Commun. 67, 1382--1390]. Conditions are described under which AMEF loses the specific antigenic determinant(s) responsible for binding activating antibody, allowing its subsequent use as an absorption to obtain immunologically purified activating antibody,

Intraocular ovarian isografts in male mice and their response to human placental lactogen

Division of Natural Sciences and Oakes College, Thimann Laboratories, University of California, Santa Cruz, California 95064, U.S.A.

(Received 6 May 1977)

The luteotrophic activity of human placental lactogen (HPL) in non-primates was demonstrated by its ability to maintain the induced decidual reaction in hypophysectomized pseudopregnant rats (Josimovich, Atwood & Goss, 1963). In the mouse, HPL has been reported to induce hyperaemia of corpora lutea of ovulation in non-parous mice (Kavocic, 1968). However, because of the design of the study, it was not possible to determine the duration of hyperaemia in those HPL-induced corpora lutea.

Ovarian isografts in male mice develop mature follicles that only rarely luteinize spontaneously. Such follicles luteinize upon the administration of luteinizing hormone (LH) and the resultant corpora lutea only show hyperaemia of function if a luteotrophic hormone is then given (Browning, 1968). The present investigation was undertaken to examine the hyperaemic response of ovarian isografts in

Roles of individual mgl gene products in the beta-methylgalactoside transport system of Escherichia coli K12

Previous findings showed that galactose-binding protein defective mutants (mgl B-,A+,C+) of Escherichia coli K12 are still capable of growth on methyl-beta-D-galactopyranoside, while mgl A- and mgl C- mutants are not. When assayed by previous methods, none of these mutants exhibited methylgalactoside transport system activity. In this study, we present a modified assay developed for measuring low levels of transport. Using this assay, we found that mgl B-,A+,C+ mutants defective in galactose-binding protein accumulate methyl-beta-D-galactopyranoside up to six times the concentration gradient while mgl A- and mgl C- mutants failed to accumulate this substrate. Similar results were obtained using D-glyceryl-beta-D-galactopyranoside, another substrate of the methylgalactoside transport system. In contrast, all sugars tested which are not substrates of this system were transported equally by all mgl- mutants. The kinetic parameters of transport in mgl B- mutants were compared to those of the isogenic mgl+ strain which accumulates methyl-beta-D-galactopyranoside against a 10,000-fold concentration gradient. The apparent Km of methyl-beta-D-galactopyranoside influx was 1,000 times greater in mgl B- than in mgl+ strains. In contrast, there was no significant difference between these strains in either the Vmax of substrate influx or the rate of substrate exit. D-Galactose competitively inhibited methyl-beta-D-galactopyranoside influx into both mgl B- and mgl+ strains; the Ki of inhibition in mgl B- cells was 2,000-fold greater than that in mgl+ cells.