• The BCRL at Fox Chase Cancer Center from 1991 to the present
• Seminal work performed in the BCRL from 1972 to 1991
• Accomplishments
• Translational Research at the BCRL
• Recent Accomplishments
• Conferences and Lectures

Seminal work performed in the BCRL from 1972 to 1991

C. Development and differentiation of the human breast

Studies have progressed from understanding of the pathogenesis of mammary cancer in rodents, to the validation of this model for the study of the human disease. Research performed during these years has led to the demonstration that undifferentiated structures of the human breast, designated lobules type 1, are the site of origin of ductal carcinoma, the most common type of cancer, (Figure 7: Click to see) (J Natl Cancer Inst 78:413, 1987; Breast Cancer Res Treat 2: 5, 1987; Cancer Res 48: 2837, 1988). More importantly, it was shown that the pattern of development and differentiation of the breast differs between nulliparous and parous women (Figure 8: Click to see).

Figure 7: Lobules types in the human breast.

Figure 8: Cycle of differentiation of the nulliparous and parous breast.

Lobules type 1 are the most frequent structures present in the breast of nulliparous women, exhibiting a high rate of cell proliferation. Their in vitro binding of a carcinogen to the DNA and their susceptibility to be transformed in culture by chemical carcinogens are greater than those of the differentiated lobule type 3 found in the breast of parous women (Cancer Res 48: 2837, 1988; Crit Rev Oncogen 4: 403,1993).

D. Development of the MCF10 cell line

Induction of immortality, or immortalization, involves abrogation of cellular programs which limit the rate and the number of cell replications, and is generally perceived as the key event of an oncogenic process. The spontaneous immortalization of HBECs is a rare event. Numerous investigators have tried to induce immortalization of HBEC using various physical, chemical, and biological approaches, such as radiation, benzo(a)pyrene, viruses, and gene transfer, respectively. The most consistent approach has been the biological one. Human papilloma virus 16 (HPV-16), the oncogenes E6 and/or E7, and the simian virus 40 (SV40) have successfully induced immortalization of HBEC. Interestingly, HBEC immortalized with viral oncogenes often express phenotypes indicative of neoplastic transformation, such as an increase in anchorage-independent growth and tumorigenesis in nude mice, even though these viruses have not been linked with the origin of human breast cancer. Therefore a normal HBEC, which does not express any transformed phenotypes, is essential to any study pertaining to experimentally induced transformation.

MCF10F was derived from a mortal human breast cell procured from a subcutaneous mastectomy specimen of a 36 year old woman with no family history of breast cancer. The breast was composed of lobule type 2 and was free of neoplasia, exhibiting only stromal fibrosis, cystic changes and ductal hyperplasia without atypia. Original explants of the tissue, maintained for over a year exhibited a normal diploid chromosomal pattern. MCF-10F cells, which exhibited immortality after extended cultivation in low calcium medium, retained the characteristics of the normal breast epithelium, such as lack of tumorigenicity in nude mice, three-dimensional growth in collagen, hormone and growth factor dependency for in vitro growth, and the lack of anchorage-independent growth and dome formation in confluent cultures. Immortalization of these cells was characterized by their continuous growth in culture medium containing either low Ca++ or the conventional level of Ca++ (1.05 mM) without entering senescence, and without expressing phenotypes indicative of neoplastic transformation, such as colony formation in agar or in agar-methocel. MCF-10F cells are bona fide normal HBEC in nature, expressing genetic, cytogenetic, ultrastructural and phenotypic characteristics of normal human breast epithelium, representing the cell line closest to a normal HBEC available. The phenotype of MCF-10F cells has been maintained stable for more than 118 passages in vitro. Several mechanisms are considered to play a role in cell immortalization, among them are the activation of telomerase, abrogation of cell cycle control, and activation of specific genes (Cancer Res 50: 6087, 1990).