Insulin-like growth factor binding protein-related protein 1 (IGFBP-rP1/mac 25) is reduced in human prostate cancer and is inversely related to tumor volume and proliferation index in Lucap 23.12 xenografts.
BACKGROUND
In the prostate, insulin-like growth factor binding protein-related protein-1 (IGFBP-rP1/mac 25) appears to be decreased in cancer. Likewise, mice injected with prostate cells over-expressing IGFBP-rP1/mac 25 showed decreased tumor formation and tumor volume.


METHODS
Immunohistochemistry was used to determine the presence of IGFBP-rP1/mac 25 in human prostate tissue and in LuCaP 23.12 prostate cancer xenografts.


RESULTS
Immunoreactivity for IGFBP-rP1/mac 25 was detected in the cytoplasm and nuclei of benign prostate epithelium. Cancer cells also stained but the level of intensity was less than that observed in benign epithelium (P < 0.05). Within the stroma, peripheral nerves, and endothelial vessels reacted with IGFBP-rP1/mac 25 antibodies. IGFBP-rP1/mac 25 was also observed in the nuclei of LuCaP 23.12 cells. LuCaP xenografts with smaller tumor volumes demonstrated more staining, and larger tumor volumes had less staining (P = 0.0033, R = 0.610). There was also a significant inverse correlation between IGFBP-rP1/mac 25 levels in LuCaP 23.12 cells and the proliferative index, measured by percent of cells staining for 5-bromo-2'-deoxyuridine (Br-dU) (P = 0.0045, R = 0.594).


CONCLUSIONS
IGFBP-rP1/mac 25 is present in normal prostate epithelium and is decreased in human prostate malignancy and higher IGFBP-rP1/mac 25 levels are associated with reduced tumor growth.
Tennant
Marie K
MK
Department of Medicine, University of Washington, Seattle, Washington, USA.
Vessella
Robert L
RL
Sprenger
Cynthia C
CC
Sikes
Robert A
RA
Hwa
Vivian
V
Baker
Laura D
LD
Plymate
Stephen R
SR
D000818:Animals; D002455:Cell Division; D002460:Cell Line; D004847:Epithelial Cells / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000378:metabolism*; D008297:Male; D051379:Mice; D009368:Neoplasm Transplantation; D011467:Prostate / Q000166:cytology / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology*; D014183:Transplantation, Heterologous
D018970:Insulin-Like Growth Factor Binding Protein 1