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Characterization of Cytokeratins Expressed in Metastatic Rat Mammary Adenocarcinoma Cells

Department of Tumor Biology [R. B. L., G. L. N.], The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, and the Department of Cell Biology [J. A. J., S. R. G.], Baylor College of Medicine, Houston, Texas 77030

The expression of cytokeratins (CKs) was investigated in cell lines and clones established from the rat 13762NF mammary adenocarcinoma tumor and its spontaneous lymph node and lung metastases. Two-dimensional polyacrylamide gel electrophoresis of intermediate filament-enriched protein fractions from cultured cells revealed that clones established from spontaneous metastases contained three CKs (M_r 54,000, 52,000, and 40,000) characteristic of simple epithelia and two CKs (M_r 51,000 and 47,000) characteristic of stratified epithelia. CK expression varied qualitatively and quantitatively between the different metastasis-derived cell clones. In contrast, cell clones established from the original mammary fat pad tumor expressed low or undetectable levels of CKs. Western blot analyses with a panel of anti-CK antibodies with defined specificities confirmed the observations. One-dimensional polyacrylamide gel electrophoresis of whole-cell lysates and intermediate filament-enriched extracts were transferred and probed with the panel of antibodies. The relative expression of individual CKs varied according to the cell line or clone examined and environmental conditions (low versus high passage and in vitro versus in vivo growth), whereas the amount of total CKs expressed relative to total cell protein varied according to cell line or clone and growth conditions.

¹ Present address: Department of Immunology and Genetics, German Cancer Center, 69, Heidelberg, FRG.

² Supported by NIH Grant R01-HD07495 from the National Institute of Child Health and Development, United States Department of Health and Human Services.

³ To whom requests for reprints should be addressed, at the University of Texas, M. D. Anderson Medical Center, Dept. of Tumor Biology, Box 108, 1515 Holcombe Boulevard, Houston, TX 77030. Supported by NIH Grant R35-CA44352 (OIG) from the National Cancer Institute, United States Department of Health and Human Services, and a grant from Dr. Karl Thomae GmbH.

Received 5/30/88. Revised 9/26/88. Accepted 9/29/88.