Influence of treatment with tamoxifen and change in tumor burden on the IGF-system in breast cancer patients.
Plasma levels of IGF-I, IGFBP-I and IGFBP-3 were measured before and during treatment with tamoxifen up to 19+ months in 34 post-menopausal patients with advanced breast cancer. In 28 patients, pro-IGF-IIE (IGF-IIE) levels were determined and IGFBP-3 was evaluated by immunoblot in 27 patients. Tamoxifen suppressed plasma levels of IGF-I by a mean value of 25.5%-37.7% at different times. This effect was fully developed after 1-2 months of treatment. IGF-IIE was decreased by a mean value of 7.7-23.2% at different time intervals during treatment with tamoxifen, but this effect was significant after long-term treatment (19 months +) only. Plasma IGFBP-I increased by a mean value varying between 48.6% and 190.1%. Tamoxifen had no significant effect on total IGFBP-3 levels. However, patients responding to treatment had a 28% reduction in fragmentation of IGFBP-3, while patients with progressive disease had a 36% increase in fragmentation. The difference between responders and non-responders was highly significant. These findings confirm and extend previous observations regarding the effects of treatment with tamoxifen on IGF-I and IGFBP-I. The finding that patients responding to tamoxifen achieve a reduction in the ratio of fragmented to intact IGFBP-3, while patients progressing on therapy experience an increase in the IGFBP-3 fragmentation ratio, suggest that the tumor burden influences IGFBP-3 protease activity in breast- cancer patients.
Helle
S I
SI
Department of Oncology, Haukeland University Hospital, Bergen, Norway.
Holly
J M
JM
Tally
M
M
Hall
K
K
Vander Stappen
J
J
Lønning
P E
PE
D000368:Aged; D000369:Aged, 80 and over; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy*; D005260:Female; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood*; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D008875:Middle Aged; D017698:Postmenopause; D011498:Protein Precursors / Q000378:metabolism; D011863:Radioimmunoassay; D013629:Tamoxifen / Q000627:therapeutic use*
D018970:Insulin-Like Growth Factor Binding Protein 1; D018972:Insulin-Like Growth Factor Binding Protein 3; D011498:Protein Precursors; D013629:Tamoxifen; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II