[CANCERRESEARCH57. 3071-3078, August 1. 1997] Perspectives in Cancer Research MCF-7: The First Hormone-responsiveBreast Cancer Cell Line' Anait S. Levenson and V. Craig Jordan2 Robert H. Lurie Cancer Center, Northwestern University Medical School, Chicago, Illinois 60611 !ntroduction On Thursday,January2, 1997, Dr. HerbertSoule, the scientist who Marc Lippman (3) demonstrated that the antiestrogen tamoxifen in developed the MCF-7 breast cancer cell line, died. At the time, we hibited the growth of MCF-7 cells, but the inhibition could be re were in the processof writingthis tributeto markthe 25th anniversary versed by estrogen. The drug was classified as a competitive inhibitor of Dr. Soule's remarkableaccomplishment.The cells, derivedfrom a of estrogen action, but at high concentrationstamoxifen killed cells. breast cancer patient in the Detroit area and developed at the Michigan Because these results appeared to parallel the emerging clinical oh CancerFoundation,Detroit,became a standardmodel in hundredsof servations (4), Lippman (3) went on to predict a future path for laboratories around the world. In retrospect, the story of the diverse endocrine research: “Thepotential value of a hormone-dependent uses of these cells is really the history of our developing knowledge human breast cancer in long term tissue culture for the study of of hormone-regulatedcell replication, and they provided a unique mechanism(s) by which steroid hormones exert their trophic effects is insight into the endocrine therapyof breastcancer. significant,particularlyin view of the likelihood of obtainingregula Our article is offered as a tributeand memorial to Dr. Soule. We tory variantsor mutantswhich are hormone independent.―Atabout will trace researchwith MCF-7 cells to illustratethe change in our the same time, KathrynHorwitz,who was completingherPh.D. in the ideas about cell replication and to highlight the advances in our late Dr. Bill McGuire's laboratory, identified the receptors for glu understanding of the signal transduction pathway of estrogen and the cocorticoids, progestins, and androgens, as well as the ER (5). She molecular biology of estrogen action. All of these advances depended concluded, “MCF-7maybe an excellent in vitro model for studying on the uniquepropertiesof MCF-7 cells. Additionally,it is important the mechanismof tumorresponseto endocrinetherapyas well as the to appreciate that the cell system has now found applications in complex relationshipsbetweenbindingandbiological actionsof these experimental therapeutics, and the results from these studies are being hormones―(5).The predictionsfrom both researchprogramswere to translated to the clinic for the treatment of patients. None of this be proved correctover the next 2 decades. would have been possible withoutDr. Soule's skill as a cell biologist. Horwitz and McGuire focused initially on the regulation of PgR synthesis in MCF-7 cells by estrogens and antiestrogens. They devel Characterization oped a largebody of evidence to associate processing(destruction)of nuclearreceptorcomplexes with the initiationof PgR synthesis (6, 7). The MCF-7 breast cancer cell line was derived from a pleural This work paralleled their suggestion of using PgR assays as a effusion taken from a patient with metastatic breast cancer (1). The predictive test for hormone-dependent breast cancer (8). Turning to 69-year-old patient had undergone a mastectomy of her right breast the effects of antiestrogens,Horwitzet a!. (9) found thattamoxifen is for a benign tumorand a radicalmastectomyof her left breastfor a sufficiently estrogenic to initiate PgR synthesis by itself. The estro malignant adenocarcinoma 7 and 3 years, respectively, before primary genic propertiesof tamoxifen would subsequently be importantto cultureof cells was started.Interestingly,the Soule et aL article (1) explain the additionalbenefits of tamoxifen on bones and lipids and notes that local recurrences were controlled for 3 years with radio the possible development of drug resistance (10). However, at that therapy and hormone therapy. In the days before tamoxifen, the time in the late l970s, work on the antiproliferative actions of antics patientwas probablytreatedwith high doses of the syntheticestrogen trogens was of paramountimportance. Tamoxifen and other corn diethylstilbestrol.Clearly, the disease was very hormoneresponsive, pounds were shown to inhibit replication(11). Drs. Rob Sutherland because it was controlled for three times longer than the 1-year (12, 13) and Kent Osborne (14, 15) would demonstrate subsequently, average to be expected. Two months after widespread nodular recur using MCF-7 cells, that tamoxifen produces a reversible block in the rences occurred, in June of 1970, samples were taken from a pleural G1 phase of the cell cycle. effusion for laboratory studies. The cells were proven to be of human Despite the interesting findings with antiestrogens, the central focus origin, and cytogenetic studies indicated a distinct stem line of 88 of laboratoryresearchin the 1970s andearly 1980s was to prove that chromosomes. Dr. Sam Brooks, working with Dr. Soule (2), first estrogen actually stimulated tumor growth directly. Dogma predicted described the ER3 in MCF-7 cells by both Scatchard and sucrose thatthe MCF-7 ER-positive cell line should grow faster with exoge density gradient analysis. This was a pivotal discovery. nous estrogen. The experiment could be accomplished routinely if From this point onward,researchacceleratedrapidly.In 1975, Dr. cells first were treated with antiestrogens for a few days. Estrogen could “rescue―antiestrogen-blockedcells (3), but the effects of es Received 4/10/97; accepted 5/30/97. trogen alone were less dramatic.Here was a paradox. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18U.S.C.Section1734solelyto indicatethisfact. Cells Grown in Estrogen 1 These studies were supported by NIH Grant CA-56143, Breast Cancer Program Development Grant P11 CA-657634, and the Lynn Sage Breast Cancer Foundation of Although Lipprnan'sgroup consistently demonstratedstimulatory Northwestern Memorial Hospital, Chicago. 2 To whom requests for reprints should be addressed, at the Robert H. Lutie Cancer effects with estrogen using [3H]thymidineincorporationas a method Center, Northwestern University Medical School, 303 East Chicago Avenue, Olson of monitoringDNA replication(3, 11, 16), otherswere unableto show Pavilion8258,Chicago,IL60611.Phone:(312)908-4148;Fax:(312)908-1372. profound effects on cell proliferation (17—19).This led to intense 3 The abbreviations used are: ER, estrogen receptor, PGR, progesterone receptor; TGF, transforming growth factor; [OF, insulin-like growth factor. debate (20) and also to the suggestion that estrogen really produced 3071 Downloaded from cancerres.aacrjournals.org on September 23, 2021. © 1997 American Association for Cancer Research. MCF-7 BREAST CANCER CELLS growth by an indirect method (21). This latter conclusion was based pivotal to all of the subsequent progress in the understanding and on the observation that estrogen did not stimulate MCF-7 cells to interpretation of data obtained with MCF-7 cells in culture. replicate in vitro, but if the same cells were grown in athymic mice, then estrogen stimulated growth. It was reasoned that estrogen must be triggeringa second messengerin vivo. At the time (1980), this was Monoclonal Antibodies to the ER not an unreasonable conclusion, because it was accepted that carcin ogen-induced rat mammary tumors require both estrogen and estro The discovery and detection of the ER protein (30—33)in the rat gen-stimulated prolactin for growth (22). Subsequently, Huseby et a!. uterus was of fundamental importance to progress in breast cancer (23), at the Michigan Cancer Foundation, provided evidence, in athy therapy. However, studies on the biochemistry of the protein mid mice, to demonstrate that estrogen had a direct growth-stimulat involved expensive experiments using rats or the collection of calf ing effect on MCF-7 tumor cells in vivo. Indirect growth stimulation uteri from slaughterhouses. Clearly, the development of antibodies through a second messenger was improbable. to the human receptor would be extremely important in research The breakthrough in our understanding of direct estrogen action and for the convenient detection of ER by clinical laboratories. came with the discovery that MCF-7 cells had been grown in estro Progress in the detection of the ER using antibodies primarily gen-containing media from the start. Indeed, if the occult estrogen had centered on Jensen's group at the Ben May Laboratory in Chicago. not been there, the MCF-7 cell model would not have been possible. Polyclonal antibodies against ER protein were obtained initially The story unfolded through a series of fortuitous accidents. Dr. using highly purified ER as an antigen to immunize rabbits and a John Katzenellenbogen was particularlyinterested in developing a goat (34, 35). To avoid the heterogeneity in the antibodies, the fluorescent-tagged estrogen so that ER could be detected easily in hybridoma techniques of Kohler and Milstein (36) were used breast cancer specimens under the fluorescence microscope. Natu subsequently to obtain monoclonal antibodies to the calf uterine rally, he was using MCF-7 cells as his laboratory model, but the nuclear ER (37). Unfortunately, there was no absolute proof that