PTHrP regulates angiogenesis and bone resorption via VEGF expression.
BACKGROUND
Parathyroid hormone-related protein (PTHrP) is a key regulator of osteolytic metastasis of breast cancer (BC) cells, but its targets and mechanisms of action are not fully understood. This study investigated whether/how PTHrP (1-34) signaling regulates expression of vascular endothelial growth factor (VEGF) produced by BC cells.


METHODS
A mouse model of bone metastasis was prepared by inoculating mice with tumour cell suspensions of the human BC cell line MDA-MB-231 via the left cardiac ventricle. VEGF expression was examined by Western blot and real-time RT-PCR analysis, as well as by confocal microscopy in the bone microenvironment.


RESULTS
PTHrP was expressed in cancer cells producing PTH/PTHrP receptor and VEGF that had invaded the bone marrow, and PTHrP was up-regulated VEGF in MDA-MB-231 in vitro. The culture medium conditioned by PTHrP-treated MDA-MB-231 cells stimulated angiogenesis and osteoclastogenesis compared with control medium, giving a response that was inhibited by VEGF-neutralizing antibody treatment. Inhibition of protein kinase C (PKC) prevented PTHrP-induced extracellular signal-regulated kinase (ERK1/2) and p38 activation, and PTHrP-induced VEGF expression.


CONCLUSIONS
PTHrP plays an important role in modulating the angiogenic and bone osteolytic actions of VEGF through PKC-dependent activation of an ERK1/2 and p38 signaling pathway during bone metastasis by breast cancer cells.
Isowa
Sachiko
S
Department of Oral and Maxillofacial Surgery, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikatacho, Okayama, 700-8525, Japan.
Shimo
Tsuyoshi
T
Ibaragi
Soichiro
S
Kurio
Naito
N
Okui
Tatsuo
T
Matsubara
Kiminori
K
Hassan
Nur Mohammad Monsur
NM
Kishimoto
Koji
K
Sasaki
Akira
A
D000818:Animals; D001859:Bone Neoplasms / Q000235:genetics / Q000378:metabolism / Q000556:secondary*; D001862:Bone Resorption / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D001943:Breast Neoplasms / Q000098:blood supply* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D003470:Culture Media; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000378:metabolism / Q000473:pathology; D004789:Enzyme Activation; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009389:Neovascularization, Pathologic / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D010010:Osteoclasts / Q000473:pathology; D044162:Parathyroid Hormone-Related Protein / Q000378:metabolism* / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D044168:Receptor, Parathyroid Hormone, Type 1 / Q000378:metabolism; D015533:Transcriptional Activation; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism
D003470:Culture Media; C473449:PTH1R protein, human; D044162:Parathyroid Hormone-Related Protein; D044168:Receptor, Parathyroid Hormone, Type 1; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases