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A Distinctive Form of Human Chorionic Gonadotropin ß-Subunit-like Material Produced by Cervical Carcinoma Cells¹

Department of Gynecology and Obstetrics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226 [R.O. H., R. A. P.]; Departments of Internal Medicine and Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan 48109 [F. P., R. W. R., L. A. C.]; Walter Reed Army Institute of Research, Washington, DC 20307 [H. G. F.]; Clinical Endocrinology Branch, National Institute of Arthritis, Diabetes, and Digestive and Kidney Diseases, NIH, Bethesda, Maryland 20205 [S. W. R., B. D. W.]; and Department of Medicine, Jefferson Medical College of Thomas Jefferson University, Philadelphia, Pennsylvania 19107 [S. B. N.]

The DoT and CaSki human cervical carcinoma cell lines ectopically produce material immunologically similar to the ß-subunit of human chorionic gonadotropin (hCGß). Culture fluids were analyzed by gel filtration chromatography and radioimmunoassay (RIA) using (a) antiserum directed to conformation-specific (core-directed) determinants not involving the carboxyl-terminal peptide (CTP) in hCGß purified from urinary hCG (i.e., standard hCGß) or (b) antiserum directed to the CTP in standard hCGß. CTP-directed RIA recognized a peak of hCGß-like immunoreactive material that eluted in the same position as standard hCGß. However, core-directed RIA recognized additional hCGß-like material (i.e., ectopic ß-II), most of which eluted before standard hCGß. CaSki cells were incubated with [³H]mannose, [³H]proline, and [³H] leucine, and the spent medium was immunoprecipitated and analyzed by gel electrophoresis. Several labeled peaks were detected in the lane from the anti-hCGß. Sepharose immunoprecipitate, one of which corresponded in mobility to standard hCGß, with two more intense components migrating at higher apparent molecular weights. Carboxypeptidase Y digestion released only 0.2 mol equivalents each of [³H]proline and [³H]leucine from the labeled CaSki material immunoprecipitated with anti-hCGß. Sepharose, compared to 1 mol equivalent each in similar analysis of standard hCGß. These findings were consistent with the absence of the 4-carboxy-terminal amino acids from 80% of the hCGß-like immunoreactive material secreted by CaSki cells. The affinity purified ectopic ß-II failed to combine with standard hCG under conditions in which combination of standard hCGß with standard hCG was essentially complete. Neither aggregation nor proteolytic degradation was the cause of failure of ectopic ß-II to combine with hCG. We conclude that both the DoT and CaSki cervical carcinoma cell lines secrete a distinctive form of hCGß-like material, ectopic ß-II. Lack of recognition by CTP-directed antisera and amino acid analysis suggest that ectopic ß-II may lack the CTP, despite its apparent larger size relative to standard hCGß.

¹ This work was sponsored in part by USPHS grant numbers CA-23357 and CA-32949, awarded by the National Cancer Institute, Department of Health and Human Services, by a grant from the Patrick and Anna Cudahy Fund, and by funds from the Department of Clinical Investigation, Walter Reed Army Medical Center. The opinions expressed herein are those of the authors and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense.

² To whom requests for reprints should be addressed.

Received 6/12/85. Revised 11/ 8/85. Accepted 1/ 7/86.

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