We are investigating the phenomenon of ectopic protein synthesis of placental proteins in neoplasms because of the link between the mechanisms associated with the derepression of the genes synthesizing embryonic proteins and those involved in neoplastic transformation. Our work has concentrated on two placental membrane proteins with emphasis on alkaline phosphatase and the transferrin receptor. We have investigated the regulation of alkaline phosphatase activity by 1,25 dihydroxyvitamin D?3? and showed specific activation of the phenotypic liver/kidney/bone enzyme in osteogenic sarcoma cells and in MDA-MB-157 breast carcinoma cells. Another breast carcinoma cell line, BT20, ectopically expresses the placental alkaline phosphatase which can be down-regulated by 1,25 dihydroxyvitamin D?3? in conjunction with its effects to promote differentiation. Bovine tranferrin was demonstrated by affinity chromatography to bind specifically to the human transferrin receptor on K562 cells grown in serum-free medium. The K?a? was estimated at 5 x 10?-5?M?-1? based on the competitive binding of unlabeled bovine transferrin with ?125?I-labeled human transferrin. Immunocytochemical localization by indirect immunofluorescence revealed that bovine transferrin is internalized in the same manner as the human ligand. Recycling of the transferrin-transferrin receptor complex was demonstrated to be partially Golgi-dependent (monensin-sensitive pathway) by the addition of 10?-5? M monensin to K562 cells. This resulted in a 50% decrease of cell-surface binding sites that was not affected by new protein synthesis. Evidence for a second recycling pathway (monensin-resistant) was found when kinetic studies were performed with monensin followed by ?125?I-human transferrin. K562 cells continued to internalize transferrin at 50% of control level and the recycling time was approximately doubled. Levels of human transferrin receptor (TR) were measured in 94 cases of primary infiltrating ductal carcinma. The mean level for these cases was approximately 5 times the level for 7 samples of benign non-neoplastic breast disease. There was a negative correlation between TR levels and estrogen (ER) levels with tumors from premenopausal patients having low levels of unsaturated ER but high TR levels indicating the possibility of faster-than-average growth. (M)

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
2R01CA013533-14
Application #
3163780
Study Section
Pathology B Study Section (PTHB)
Project Start
1974-06-01
Project End
1988-07-31
Budget Start
1985-09-01
Budget End
1986-07-31
Support Year
14
Fiscal Year
1985
Total Cost
Indirect Cost
Name
Stanford University
Department
Type
Schools of Medicine
DUNS #
800771545
City
Stanford
State
CA
Country
United States
Zip Code
94305
Sussman, H H (1992) Iron in cancer. Pathobiology 60:2-9
Penhallow, R C; Mason, A B; Woodworth, R C (1991) Electrophoretic characterization of human, equine and bovine transferrins. Comp Biochem Physiol B 98:41-5
Penhallow, R C; Sussman, H H (1990) A difference in the regulation of mRNA expression between the phenotypic and the embryonic alkaline phosphatase genes in human cancer cells. Exp Cell Res 188:279-85
Penhallow, R C; Sussman, H H (1990) Human placental alkaline phosphatase PstI RFLP alleles are the result of a single base substitution. Nucleic Acids Res 18:1930
Tsavaler, L; Penhallow, R C; Sussman, H H (1988) Pst I restriction fragment length polymorphism of human placental alkaline phosphatase gene: Mendelian segregation and localization of mutation site in the gene. Proc Natl Acad Sci U S A 85:7680-4
Enns, C A; Mulkins, M A; Sussman, H et al. (1988) Modulation of the transferrin receptor during DMSO-induced differentiation in HL-60 cells. Exp Cell Res 174:89-97
Tsavaler, L; Penhallow, R C; Kam, W et al. (1987) Pst I restriction fragment length polymorphism of the human placental alkaline phosphatase gene in normal placentae and tumors. Proc Natl Acad Sci U S A 84:4529-32
Mulkins, M A; Sussman, H H (1987) 1,25-Dihydroxyvitamin D3 exerts opposite effects on the regulation of human embryonic and nonembryonic alkaline phosphatase isoenzymes. Endocrinology 120:416-25
Tonik, S E; Sussman, H H (1987) Radioimmunoassay of transferrin receptor. Methods Enzymol 147:253-65
Stein, B S; Sussman, H H (1986) Demonstration of two distinct transferrin receptor recycling pathways and transferrin-independent receptor internalization in K562 cells. J Biol Chem 261:10319-31

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