Nature 316, 840 - 842 (29 August 1985); doi:10.1038/316840a0

Smooth muscle -actin is a transformation-sensitive marker for mouse NIH 3T3 and Rat-2 cells

John Leavitt^*, Peter Gunning^†, Larry Kedes^† & Raxit Jariwalla^*

^*Armand Hammer Cancer Research Center, Linus Pauling Institute of Science and Medicine, Palo Alto, California 94306, USA
^†The MEDIGEN Project, Department of Medicine, Stanford University School of Medicine and Veterans Administration Medical Center, Palo Alto, California 94304, USA

Heteroploid mouse NIH 3T3 fibroblasts and several rat fibroblast strains (Rat-1, Rat-2 and REF-52) are cell lines of special interest in the field of carcinogenesis because of their extensive use as normal cells in transformation assays for putative cancer-causing genes. Exposure of these cells to carcinogenic chemicals or oncogenic DNA produces anchorage-independent cells with retracted cytoplasms that lack actin cables¹⁻⁷. All human fibroblast strains, normal and transformed, synthesize two electrophoretic forms of actin (- and -actin)⁸⁻¹⁰. In contrast, we discovered that early-passage mouse and rat strains synthesize abundant amounts of each of the three electrophoretic forms of actin (-, - and -actin) but mouse and rat cancer cells express only - and -actins. We now show that in NIH 3T3 and Rat-2 fibroblasts a third actin, the smooth muscle isoform, is abundantly co-expressed with -and -actin. In every instance tested following transformation to tumorigenicity, the accumulation of a-actin messenger RNA and -actin synthesis was greatly inhibited. Shutdown of -actin expression thus appears to be a reproducible transformation-sensitive marker in rodent fibroblasts.

References

1.	Topp, W. C. Virology 113, 408−411 (1981).
2.	Aaronson, S. A. & Todaro, G. J. J. cell. Physiol. 72, 141−148 (1968).
3.	Land, H., Parada, L. F. & Weinberg, R. A. Nature 304, 596−602 (1983).
4.	Tabin, C. J. et al. Nature 300, 143−149 (1982).
5.	Parker, R. C., Varmus, H. E. & Bishop, J. M. Cell 37, 131−139 (1984).
6.	Eva, A., Tronick, S. R., Gol, R. A., Pierce, J. H. & Aaronson, S. A. Proc. natn. Acad. Sci. U.S.A., 80, 4926−4930 (1983).
7.	Pollack, R., Osborn, M. & Weber, K. Proc. natn. Acad. Sci. U.S.A. 72, 994−998 (1975).
8.	Leavitt, J. et al. Cell 28, 259−268 (1982).
9.	Leavitt, J. & Kakunaga, T. J. biol. Chem. 255, 1650−1661 (1980).
10.	Leavitt, J., Leavitt, A. & Attallah, A. J. biol. Chem. 255, 4984−4987 (1980).
11.	Latter, G. I., Burbeck, S., Fleming, J. Leavitt, J. clin. Chem. 30, 1925−1932 (1985).
12.	Jariwalla, R. J., Aurelian, L. & Ts'o, P. O. P. Proc. natn. Acad. Sci. U.S.A. 80, 5902−5906 (1983).
13.	Clanton, D. J., Jariwalla, R. J., Kress, C. & Rosenthal, L. Proc. natn. Acad. Sci. U.S.A. 80, 5107−5111 (1983).
14.	Franza, B. R. & Garrels, J. I. Cancer Cells 1, 137−146 (1984).
15.	Gunning, P., Ponte, P., Kedes, L., Hickey, R. J. & Skoultchi, A. I. Cell 36, 709−715 (1984).
16.	Ponte, P., Gunning, P., Blau, H. & Kedes, L. Molec. cell. Biol. 3, 1783−1791 (1983).
17.	Garrels, J. I. & Gibson, W. Cell 9, 793−805 (1976).
18.	Hunter, T. & Garrels, J. I. Cell 12, 767−781 (1977).
19.	Vandekerckhove, J. & Weber, K. J. molec. Biol. 126, 783−802 (1978).
20.	Vandekerckhove, J. Weber, K. Eur. J. Biochem. 113, 595−603 (1981).
21.	Matsumura, F., Lin, J. J.-C., Yamashiro-Matsumura, S., Thomas, G. P. & Topp, W. C. J. biol. Chem. 258, 13954−13964 (1983).
22.	Leavitt, J., Barren, J. C., Crawford, B. D. & Ts'o, P. O. P. Nature 271, 262−265 (1978).
23.	Naharro, G., Robbins, K. C. & Reddy, E. P. Science 223, 63−66 (1984).
24.	Goldstein, D. & Leavitt, J. Cancer Res. (in the press).
25.	Vanderkerckhove, J., Leavitt, J., Kakunaga, T. Weber, K. Cell 22, 893−899 (1980).
26.	Friedman, E., Verderame, M., Winawer, S. & Pollack, R. Cancer Res. 44, 3040−3050 (1984).
27.	Gunning, P. et al. Molec. cell. Biol. 3, 787−795 (1983).
28.	Gunning, P., Mohun, T., Ng, S-Y. Ponte, P. & Kedes, L. J. molec. Evol. 20, 202−214 (1984).
29.	Rigby, P. W., Dieckmann, M., Rhodes, C. & Berg, P. J. Molec. cell. Biol. 113, 237−251 (1977).
30.	Denhardt, D. T. Biochem. biophys. Res. Commun. 23, 641−646 (1966).