Biochemical studies of hormone-responsive mammary tumors.

Abstract

Russell HilfSquibb Institute ÂiorMedical Research, New Brunswick, New JerseyStudies in our laboratory have been devoted to the characterization of experimental mammary tumors. We have approached this problem by studying both morphologic and biochemical parameters, with emphasis on achieving correlations,in order to obtain an understanding of this class of malignancies. \Ve have the ability to draw upon the knowledge fromclinical studies, such as those conducted by the CooperativeBreast Study Group, in looking for experimental models thatsimulate the chemotherapeutic sensitivity of the human disease. It is well known that estrogens and androgens, and to alesser extent progestogens and corticoids, can induce remissionof advanced breast cancer. It is essential, therefore, that anunderstanding be gained of the biochemical alterations accompanying hormonal treatment in an effort to evaluate the mechanism of action of the hormonal agent, as well as to establishthe criteria for judging the validity of a particular experimentaltest system.For the past several years, we have endeavored to characterize a particular transplan tabi e mammary carcinoma (5-7),R3230AC, an adenocarcinoma with predominantly epithelialelements and a slight amount of interstitial stroma. The growthof this autonomous tumor was inhibited by treatment withestrogen which produced a marked secretory response characterized by extensive vacuolization and distention of acini witha milk-like fluid that stained with Oil Red O. This lactation-like response was shown to be related to the dose of estrogenadministered, and it was demonstrated that estrogen treatmentproduced elevations in the activities of glucose-6-phosphatedehydrogenase, malate dehydrogenase (decarboxylating) andphosphoglucomutase and decreases in glucosephosphate isom-erase and tx-glycerolphosphate dehydrogenase (4). In additionto the enzyme changes, treatment with estrogen caused a dose-related increase in the amounts of free fatty acids and triglycA©ridesin the neoplasm, although cholesterol levels were notaltered (4). Further studies demonstrated that the estrogen-1The studies performed in our laboratory were supported bycontracts SA-43-ph-2395 and PH43-65-1050, Endocrine EvaluationBranch, General Laboratories and Clinics, National Cancer Institute, NIH, Bethesda, Maryland. The data obtained on the13762 transplantable dimethylbenz(a)anthracene mammary tumorswere derived from experiments performed in cooperation withDr. Albert Segaloff, Ochsner Medical Foundation, New Orleans,Louisiana. The preliminary data obtained on the primary methyl-cholanthrene and dimethylbenz(a)anthracene neoplasms were theresult of a continuing cooperative study with Dr. Sidney Wein-house, Dr. Michael Shimkin, Mrs. Margot Gruenstein, and Dr.David Meranze, Fels Research Institute, Temple UniversitySchool of Medicine, Philadelphia, Pennsylvania.induced elevations in enzyme activities were prevented by concomitant administration of either actinomycin D or actidione,results which strongly suggest that the hormone-induced responses in enzyme activities reflected protein synthesis de novo(2,8).One of the most intriguing aspects of this biochemical response to estrogen, which resembles the response of the normalmammary gland during pregnancy and lactation, was the accumulation of a milk-like fluid in the neoplasm. This fluid wasfound to contain lactose, at a concentration of about 2% thatfound in rat milk, and exhibited a pattern of fatty acids thatresembled that found in rat milk. Electrophoresis of the proteins in this milk-like fluid from the tumor revealed the presence of both casein and whey proteins with clectrophoreticproperties similar to those of the casein and whey proteins inrat milk (1). It was concluded from the above biochemicalstudies that the inhibition of growth of the R3230AC adenocarcinoma by estrogen treatment was the result of the inductionof a metabolic state similar to lactation, and the resultant stimulation of the metabolic pathways resulted in a secretory staterather than cellular proliferation.In contrast to the effects of estrogen, administration of andro-gen resulted in a flattening of the epithelial cells, absence ofvacuolization, and a dose-related decrease in all enzyme activities studies with the exception of a-glycerolphosphate dehydrogenase (5, 7). Unfortunately, androgen treatment causesonly a slight inhibition of tumor growth, suggesting that thedecrease in enzyme activities in no way significantly impairsthe ability of the neoplasm to grow. It is of interest that recentstudies, employing concomitant administration of actinomycinD or actidione to androgen-treated tumor-bearing animals, havedemonstrated a partial prevention of the hormone-induced decrease in enzyme activities by these antibiotics. These dataindicate that the response to androgens also was dependent onthe synthesis of proteins de novo.In cooperation with Dr. Albert Segaloff, we have expandedour studies by examining four lines of the 13762 transplantable dimethylbenz(a)anthracene (DMBA)-induced mammarytumor that were developed by him (9). These neoplasms havebeen maintained in normal male hosts, androgen-treated hosts(TP-line), normal female hosts, and estrogen-treated hosts(estradici line). Segaloff has shown that the morphology ofthese tumors can be influenced by conditioning, since the normal male line appears to contain mostly stroma, whereas theandrogen-conditioned neoplastic line is primarily composed ofmalignant glandular cells. We have investigated the profile ofenzyme activities of these four tumor lines and have found that1888 CANCER RESEARCH VOL. 28€Copyright © 1968 American Association for Cancer Research