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Amplification of the Murine Leukemia Virus M_r 70,000 Glycoprotein Gene Product by Human Xenografts in Athymic Mice¹

Cancer Center and Department of Chemistry [G. M. B., R. A. L., E. V. H., J. F. L., N. O. K.] and Department of Pathology [S. M. B.], University of California at San Diego, La Jolla, California 92093; The Veteran's Administration Medical Center, San Diego, California 92161 [S. M. B.]; and Research Institute of Scripps Clinic, La Jolla, California 92037 [F. C. J.]

Passage of human tumors in athymic mice is accompanied by an increase in serum levels of the M_r 70,000 murine leukemia virus envelope protein, gp70. Elevated levels of gp70 can be detected in tissues of the hematopoietic systems of mice bearing human xenografts, but there is no evidence of synthesis of gp70 in these tissues. By far, the highest concentration of gp70 is in the human xenografts themselves. When assayed for gp70, 8 human xenografts and 12 cell lines established from human xenografts were all positive. In the plasma membrane of the human astrocytoma xenograft, T24, the gp70 was found to be approximately 10% of the total membrane protein. In contrast, the concentration of the M_r 30,000 viral core protein, p30, was 17-fold less. Only trace amounts of complete infectious virus could be detected. A human prostate carcinoma line that had not been grown in the athymic mice was found to have no gp70, but was shown to be able to synthesize gp70 after a single passage in the athymic mice.

¹ Supported by USPHS National Cancer Institute Grants CA 23052 and 11683, and the Research Service of the Veteran's Administration.

² To whom requests for reprints should be addressed.

Received 9/20/82. Accepted 6/ 8/83.