Monoclonal antibody that defines human myoepithelium.

Abstract

We have isolated a mouse monoclonal antibody that, upon immunohistochemical localization in frozen sections, displays specificity for human myoepithelial cells in the resting mammary gland, sweat glands, and salivary glands. Furthermore, this antibody was strongly and homogeneously reactive with frozen sections of 3 of 60 breast carcinoma specimens. Using immunolocalization techniques in conjunction with polyacrylamide gel electrophoresis, we have determined that the reactivity of this monoclonal antibody is directed toward a 51,000-dalton keratin polypeptide. The potential uses of this antibody in the prognosis of human mammary carcinoma and in understanding the role of the myoepithelium in development and differentiation are discussed.Myoepithelial cells are derived from ectoderm and are known to exhibit both epithelial and mesenchymal characteristics (1, 2). They are situated between acinar or ductal luminal cells and the basal lamina in a number of secretory glands such as breast, lacrimal, eccrine, and apocrine sweat glands and various salivary glands (3).We report here on a monoclonal antibody directed toward a cytoskeletal keratin that is unique to the myoepithelial or "basal" layer of epithelial cells in human mammary ducts, sweat glands, and salivary glands. Using polyacrylamide gel electrophoresis and immunoblotting, we have found the apparent molecular weight of this basal epithelium-specific keratin to be 51,000 daltons. The antibody is generally nonreactive with luminal epithelium, stroma, muscle, fat, and vasculature. Therefore, it appears to be a useful tool in studying the role of the myoepithelium in the normal development of the breast, during lactation and involution, and in malignancy and metastasis.Recently, considerable advances have been made in tumor diagnosis by immunocytochemical typing of intermediate filaments. For example, carcinomas are characterized by antibodies to cytokeratins; sarcomas of muscle cells, by anti-desmin; nonmuscle sarcomas, by anti-vimentin; and gliomas, by anti-glial fibrillary acidic protein (for review, see ref. 4). The myoepithelium-specific monoclonal antibody described in this report has allowed us to define and characterize subclasses of human mammary carcinomas that would not be possible to distinguish by conventional techniques. The potential application of this antibody in the prognosis of human mammary carcinoma is discussed. MATERIALS AND METHODSImmunization. BALB/c mice raised under pathogen-free conditions were injected via subcutaneous or intravenous routes for 5 weeks at weekly intervals with whole-cell preparations of a secondary culture of an infiltrating ductal breast carcinoma. For each inoculation, 106 cells, which had been cultured as previously described (5), were prepared by scraping the monolayer with a rubber policeman into phosphate-buffered saline. Splenocytes from immunized animals were fused with SP2/0 mouse myeloma cells in the presence of polyethylene glycol (Mr 4000; Merck) by the procedure of Kohler and Milstein (6). Monocl...

Stem Cells in the Human Breast

“…A landmark paper in 1985 reported the first reliable staining of the basal/myoepithelial lineage within the human breast (Dairkee et al 1985). Surprisingly, a fraction of cancer cells also stained with the keratin 14 antibody in a subset of breast carcinomas, but the majority displayed a luminal staining pattern.…”

“…Surprisingly, a fraction of cancer cells also stained with the keratin 14 antibody in a subset of breast carcinomas, but the majority displayed a luminal staining pattern. This mixed phenotype provided the first evidence for multilineage evolution within the tumor (Dairkee et al 1985). Based on genome-wide gene expression profiling of breast tumors, we now know that these carcinomas belong to the basal-like subtype of breast cancers, which are assumed to be stem cell-derived or to have acquired properties of stem cells during transformation (Sørlie et al 2001).…”

Repression of p63 and induction of EMT by mutant Ras in mammary epithelial cells

“…In head and neck squamous cell carcinomas, the p63 locus is often amplified, suggesting an oncogenic role (23). However, in other types of tumors, basal epithelial markers like p63 and keratin 14 are lost (24)(25)(26), and ΔNp63 has been found to suppress EMT in prostate and bladder cancer cells (27,28). Surprisingly, in one report, ΔNp63α and ΔNp63β were found to inhibit, whereas ΔNp63γ promoted, EMT in MCF10A mammary epithelial cells (29).…”

Immunohistochemical detection of keratin, actin and type IV collagen in serial sections of methacarn-fixed breast cancer tissues.

“…Moreover, loss of keratin 14-positive cells in transplantable sublines of mouse mammary carcinoma has been recently reported by the authors to be accompanied by the acquisition of lung-colonizing capability and patchy type IV collagen surrounding cancer nests (10). Keratin 14 has been thought to be identified only in cryostat sections (3,11,17), but it can now be seen in methacarn-fixed, dewaxed and actinasepretreated sections. In this paper, correlations among the immunolocalizations of some cytokeratins, muscle actin and type IV collagen are investigated in serial sec- Table 2.…”