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Enhancement by Human Placenta! Lactogen of Mammary Hyperplastic Nodules in Ovariectomized Mice1

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Enhancement by Human Placenta! Lactogen of Mammary Hyperplastic Nodules in Ovariectomized Mice1 (CANCER RESEARCH 33. 1642 1644, July 1973] Enhancement by Human Placenta! Lactogen of Mammary Hyperplastic Nodules in Ovariectomized Mice1 Reiko Yanai and Hiroshi Nagasawa Pharmacology Division, National Cancer Center Research Institute, Tsukiji 5-1-1, Chuo-ku, Tokvo 104, Japan SUMMARY effect of placental lactogen on the maintenance and growth of HN in mice as 1 step to clarify the hormonal mechanism The effect of human placenta! lactogen on the mainte of the influence of pregnancy on mammary tumorigenesis. nance and growth of precancerous mammary hyperplastic nodules was studied in ovariectomized, multiparous C3H/He female mice. In mice receiving injections of 0.5 mg MATERIALS AND METHODS of human placenta! lactogen twice daily for 19 days and on the morning of the 20th day, beginning the morning C3H/He multiparous female mice, without palpable following bilateral ovariectomy, the number of nodules per mammary tumors and 10 to 11 months old, were divided mouse was similar to that in the intact controls. The into 3 groups. Group 1 remained intact and served as the ovariectomized controls had significantly fewer nodules intact controls. Groups 2 and 3 were bilaterally ovariecto than the intact controls and the ovariectomized, placenta! mized. Group 2 received no further treatment (ovariecto lactogen-treated mice. The average size of nodules was mized controls). Group 3 received injections s.c. of 0.5 mg significantly larger in the ovariectomized, placenta! lacto of HPL (Nutritional Biochemicals, Cleveland, Ohio) dis gen-treated mice and was smaller in the ovariectomized solved in 0.1 ml of 0.9% NaCl solution, twice daily for 19 controls than in the intact controls. The number of very days and on the morning of the 20th day. The injections large nodules was extremely high in the ovariectomized, were started on the morning following ovariectomy. They placental lactogen-treated mice. These results suggest that were maintained in an air-conditioned and artificially placenta! lactogen plays an important role in the mainte illuminated room and offered commercial diet and water ad nance and growth of precancerous mammary hyperplastic libitum. All the mice were killed 4 to 5 hr after the last nodules in mice. injection. The 3rd thoracic mammary glands were excised from both sides and prepared for whole-mount evaluations. The numbers of HN and "ghosts" (remnants of regressed INTRODUCTION HN) were counted and the size of each HN was expressed as the arithmetic mean of the 2 major diameters. The mam Some mammary tumors in mice grow rapidly during mary glands were examined under 10-fold magnification. pregnancy but regress after parturition (7). However, up to the present time, no data are available on the precise hormonal mechanism of mammary tumorigenesis during RESULTS AND DISCUSSION pregnancy, although Foulds (6) described the possible effect of gonadotropic hormones, placental hormones, and the The number and size of HN and the number of ghosts in cooperative action of estrogenic and luteal hormones on this each group are presented in Table 1. The number of HN per process. The development and growth of precancerous HN2 mouse in Group 3 was not different from that in Group 1 and their malignant transformation depend primarily upon and both were significantly higher than that in Group 2 (p pituitary prolactin (21 23). Recently, it has been demon < 0.05). The average size of HN was significantly smaller strated that there exists a prolactin-like substance (placental in Group 2 and was larger in Group 3 than in Group 1 (p < lactogen) in the placentae of mice (13), rats (5, 12, 14-17, 0.01). Very large HN were characteristic in the glands of 20), goats (3, 4), and monkeys (8-11) as well as humans Group 3. The average number of HN greater than 1 mm (19, 20). The similarity of placental lactogen to prolactin in was 6.2, 2.3, and 14.2 per mouse in Groups 1, 2, and 3, several biological actions has been documented (1, 2) and respectively. While the number of ghosts was not signifi the predominant participation of placental lactogen in cantly different among groups, it was rather large in Group mammary development during pregnancy is suggested (1, 2. A representative whole-mount preparation from each 18). In the present paper, we have attempted to study the group is shown in Figs. 1 to 3. The glands of Group 1 consisted of numerous ducts and branches with good 1This research was supported in part by a grant-in-aid for Cancer lobuloalveolar development and many HN (Fig. 1). On the Research, from the Ministry of Education. Japan (90393). 2The abbreviations used are: HN, hyperplastic nodules; HPL. human other hand, the glands of Group 2 were markedly involuted placental lactogen. and some small HN were found (Fig. 2). In Group 3, while Received September 26, 1972; accepted March 28, 1973. normal lobuloalveolar system rather regressed, some alveoli 1642 CANCER RESEARCH VOL. 33 Downloaded from cancerres.aacrjournals.org on September 26, 2021. © 1973 American Association for Cancer Research. Placental Lactogen on Mammary Nodules Table 1 Number and size of mammary HN and number of ghosts in each group Group 3 received injections s.c. of 0.5 mg of HPL twice daily for 19 days and on the morning of ¡he20thday, beginning the morning following ovariectomv. ofmouse*33.320.733.6±2.5"-'±3.7±3.5'0.640.540.94(mm)r±HN/Av. size Group123Treatment"Intact controlsOvx 0.03'±0.02± controlsOvx; HPL, 0.5mg, 2xNo.ofmice91012No.No.of 0.02'- «HNofghosts/mouse(299)"(207)(403)0.72.50.9±t±0.21.00.3 " Ovx, ovariectomy. "Sum in bilateral thoracic 3rd mammary glands. r Arithmetic mean of the major 2 diameters of HN. " Mean ±S.E. ' Significant difference, p < 0.05 from Ovx controls. ' Significant difference, p < 0.01 from Ovx controls. 8Significant difference, p < 0.05 from intact controls. *Total number of HN examined. showed atypical development and milk secretion was ob 7. Foulds, L. The Experimental Study of Tumor Progression. A Review. served in all glands. There existed several huge HN (Fig. 3). Cancer Res., 14: 327 339, 1954. The body weight in Group 3 slightly decreased during the 8. Friesen, H. G. Biosynthesis of Placental Proteins and Placental experiment, whereas those in Groups 1and 2 changed little. Lactogen. Endocrinology, 83: 744-753, 1968. These results provide ample evidence that HPL can 9. Friesen, H. G., Suwa, S., and Pare, P. Synthesis and Secretion of Placental Lactogen and Other Proteins by the Placenta. Recent Progr. promote the maintenance and growth of HN in the absence Hormone Res., 25; 161-205, 1969. of ovarian steroid hormones, and they imply that placenta! 10. Grant, D. B., Kaplan, S. L., and Grumbach, M. M. Studies on a lactogen is 1 of the important factors in the earlier and Monkey Placental Protein with Immunochemical Similarity to higher incidence of spontaneous mammary tumors in Human Growth Hormone and Human Chorionic Somatomammotro- multiparous mice than in virgin mice. phin. Acta Endocrino!., 63: 736 746, 1970. The normal mammary system was not always maintained 11. Kaplan, S. L., and Grumbach, M. M. Studies of a Human and Simian by HPL. We previously observed that involution of the Placental Hormone with Growth Hormone-like and Prolactin-like normal mammary gland was not completely prevented by Activities. J. Clin. Endocrinol. Metab., 24: 80 100, 1964. isograft of pituitaries in adrenoovariectomized mice, 12. Kinzey, W. G. Hormonal Activity of the Rat Placenta in the Absence of Dietary Protein. Endocrinology, 82: 266-270, 1968. whereas the maintenance and growth of HN in these mice 13. Kohmoto, K., and Bern, H. A. Demonstration of Mammotrophic Ac were good (22). Further experiments on the different tivity of the Mouse Placenta in Organ Culture and by Transplantation. responsiveness between normal mammary gland and HN to J. Endocrinol., 48: 99 107, 1970. placenta! lactogen or pituitary prolactin are now in pro 14. Lyons, W. R. Hormonal Synergism in Mammary Growth. Proc. Roy. gress. Soc. London Ser. B, 149: 303 325, 1958. 15. Matthies, D. L. Studies of the Luteotropic and Mammotropic Factor Found in Trophoblast and Maternal Peripheral Blood of the Rat at Midpregnancy. Anat. Record, 159: 55-67, 1967. REFERENCES 16. Matthies, D. L. A Rapid Assay for the Lactogenic Activity of Rat Chorionic Mammotropin. Proc. Soc. Exptl. Biol. Med., 127: 1. Amoroso, E. C., and Porter, D. G. Anterior Pituitary Function in 1126 1129, 1968. Pregnancy. In: G. W. Harris and B. T. Donovan (eds.). The Pituitary 17. Matthies, D. L., and Lyons, W. R. Luteotrophic and Luteolytic Effects Gland, Vol. 2, pp. 364-411. London: Butterworth. 1966. of Rat Chorionic Mammotropin. Proc. Soc. Exptl. Biol. Med., 136: 2. Cowie, A. T., and Tindal, J. S. The Physiology of Lactation, pp. 520-523, 1971. 53-83, 355-359. London: Edward Arnold, 1971. 18. Nagasawa, H., and Yanai, R. Quantitative Participation of Placental 3. Buttle, H. L., and Forsyth, I. A. Prolactin Concentration and Mammotropic Hormones in Mammary Development during Preg Lactogenic Activity in the Plasma of Pregnant and Lactating Goats. J. nancy of Mice. Endocrinol. Japon., 18: 507-510, 1971. Endocrinol., 5/: xxxiii-xxxiv, I97K 19. Saxena, B. N. Protein-Polypeptide Hormones of the Human Placenta. 4. Buttle, H. L., Forsyth, I. A., and Knaggs, G. S. Plasma Prolactin Vitamins Hormones, 29: 95- 151, 1971. Measured by Radioimmunoassay and Bioassay in Pregnant and 20. Shani (Mishkinsky), J., Zanbelman, L., Khazen, K., and Sulman, F. Lactating Goats and the Occurrence of a Placental Lactogen. J. G. Mammotrophic and Prolactin-like Effects of Rat and Human Endocrinol., 53: 483-491, 1972. Placentae and Amniotic Fluid.
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