Hedgehog promotes neovascularization in pancreatic cancers by regulating Ang-1 and IGF-1 expression in bone-marrow derived pro-angiogenic cells.
BACKGROUND
The hedgehog (Hh) pathway has been implicated in the pathogenesis of cancer including pancreatic ductal adenocarcinoma (PDAC). Recent studies have suggested that the oncogenic function of Hh in PDAC involves signaling in the stromal cells rather than cell autonomous effects on the tumor cells. However, the origin and nature of the stromal cell type(s) that are responsive to Hh signaling remained unknown. Since Hh signaling plays a crucial role during embryonic and postnatal vasculogenesis, we speculated that Hh ligand may act on tumor vasculature specifically focusing on bone marrow (BM)-derived cells.


RESULTS
Cyclopamine was utilized to inhibit the Hh pathway in human PDAC cell lines and their xenografts. BM transplants, co-culture systems of tumor cells and BM-derived pro-angiogenic cells (BMPCs) were employed to assess the role of tumor-derived Hh in regulating the BM compartment and the contribution of BM-derived cells to angiogenesis in PDAC. Cyclopamine administration attenuated Hh signaling in the stroma rather than in the cancer cells as reflected by decreased expression of full length Gli2 protein and Gli1 mRNA specifically in the compartment. Cyclopamine inhibited the growth of PDAC xenografts in association with regression of the tumor vasculature and reduced homing of BM-derived cells to the tumor. Host-derived Ang-1 and IGF-1 mRNA levels were downregulated by cyclopamine in the tumor xenografts. In vitro co-culture and matrigel plug assays demonstrated that PDAC cell-derived Shh induced Ang-1 and IGF-1 production in BMPCs, resulting in their enhanced migration and capillary morphogenesis activity.


CONCLUSIONS
We identified the BMPCs as alternative stromal targets of Hh-ligand in PDAC suggesting that the tumor vasculature is an attractive therapeutic target of Hh blockade. Our data is consistent with the emerging concept that BM-derived cells make important contributions to epithelial tumorigenesis.
Nakamura
Kazumasa
K
Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical College, Asahikawa, Japan.
Sasajima
Junpei
J
Mizukami
Yusuke
Y
Sugiyama
Yoshiaki
Y
Yamazaki
Madoka
M
Fujii
Rie
R
Kawamoto
Toru
T
Koizumi
Kazuya
K
Sato
Kazuya
K
Fujiya
Mikihiro
M
Sasaki
Katsunori
K
Tanno
Satoshi
S
Okumura
Toshikatsu
T
Shimizu
Norihiko
N
Kawabe
Jun-ichi
J
Karasaki
Hidenori
H
Kono
Toru
T
Ii
Masaaki
M
Bardeesy
Nabeel
N
Chung
Daniel C
DC
Kohgo
Yutaka
Y
D042683:Angiopoietin-1 / Q000235:genetics*; D000818:Animals; D001854:Bone Marrow Cells / Q000378:metabolism*; D016026:Bone Marrow Transplantation; D021441:Carcinoma, Pancreatic Ductal / Q000098:blood supply* / Q000235:genetics / Q000473:pathology; D045744:Cell Line, Tumor; D053823:Hedgehog Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D051379:Mice; D008819:Mice, Nude; D009389:Neovascularization, Pathologic / Q000503:physiopathology*; D010190:Pancreatic Neoplasms / Q000098:blood supply* / Q000235:genetics / Q000473:pathology; D014183:Transplantation, Heterologous; D014704:Veratrum Alkaloids / Q000494:pharmacology
C467630:ANGPT1 protein, human; D042683:Angiopoietin-1; D053823:Hedgehog Proteins; D014704:Veratrum Alkaloids; D007334:Insulin-Like Growth Factor I; C000541:cyclopamine