Prostate cancer cells regulate growth and differentiation of bone marrow endothelial cells through TGFbeta and its receptor, TGFbetaRII.
BACKGROUND
The underlying mechanisms permitting prostate cancer bone metastasis are poorly understood. We previously showed that the highly metastatic prostate cancer cell line, PC-3, inhibits bone marrow endothelial (HBME-1) cell growth in collagen gels and induces them to differentiate into cords, resembling angiogenesis in vivo.


METHODS
cDNA microarray analysis was performed to identify cytokines responsible for the effects of PC-3 cells on HBME-1 cells. Cytokine and neutralizing antibody studies were done to further investigate specific angiogenic factors, such as transforming growth factor beta (TGFbeta). TGFbeta RNA and protein were detected by real-time RT-PCR and enzyme-linked immunosorbent assay (ELISA) analysis to measure their production by prostate cancer cell lines. Conditioned media experiments using TGFbeta neutralizing antibodies were used to analyze TGFbeta activation by prostate cancer cells.


RESULTS
PC-3 conditioned media altered the expression of several TGFbeta-regulated or -associated genes in HBME-1 cells. Low concentrations of TGFbeta cytokines inhibited HBME-1 cell growth to a similar level as PC-3 conditioned media and partially induced differentiation. Inhibitors and neutralizing antibodies directed against TGFbeta isoforms and TGFbeta receptor type 2 (TGFbetaRII) reversed the growth inhibition of HBME-1 cells conferred by PC-3 conditioned media. Yet, only TGFbetaRII neutralizing antibodies significantly inhibited HBME-1 differentiation. Also, prostate cancer cell lines produced low levels of TGFbeta RNA and protein, and were shown to activate serum-derived TGFbeta.


CONCLUSIONS
These results suggest that prostate cancer cells mediate growth inhibition and differentiation of bone marrow endothelial cells both through production and activation of TGFbeta as well as alteration of TGFbetaRII-mediated signal transduction. This could contribute to the establishment and growth of bone metastases.
Barrett
Jeffrey M
JM
Interdepartmental Biological Sciences Program, Northwestern University, Evanston, Illinois 60201, USA.
Rovedo
Mark A
MA
Tajuddin
Aamair M
AM
Jilling
Tamas
T
Macoska
Jill A
JA
MacDonald
James
J
Mangold
Kathy A
KA
Kaul
Karen L
KL
D001854:Bone Marrow Cells / Q000166:cytology / Q000473:pathology*; D002449:Cell Aggregation; D045744:Cell Line, Tumor; D017077:Culture Media, Conditioned; D017931:DNA Primers; D042783:Endothelial Cells / Q000166:cytology / Q000473:pathology*; D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology*; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000502:physiology*
D017077:Culture Media, Conditioned; D017931:DNA Primers; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II