Chondromodulin-1 directly suppresses growth of human cancer cells.
BACKGROUND
Chondromodulin-1 (ChM1), an endogenous anti-angiogenic factor expressed in cartilage, has been suggested to inhibit invasion of endothelial cells into cartilage. In addition, the ectopic administration of ChM1 has been reported to suppress tumorigenesis in vivo. However, it is unclear whether the anti-tumor effect is due to not only the anti-vascularization effect of ChM1, but also its direct action against oncocytes. In the present study, we sought to determine whether ChM1 has a direct action on tumor cells.


METHODS
BrdU incorporation assay was performed on human umbilical vein endothelial cells (HUVECs), normal human dermal fibroblasts (NHDFs), HepG2 cells and HeLa cells in the presence or absence of recombinant human ChM1 (rhChM1). An adenovirus that expresses ChM1, Ad-ChM1, was established and applied to the tumor xenografted in vivo, and to in vitro tumor cells cultured on plates or in soft agar. Cell cycle-related proteins and the phosphorylation of Erk, Akt, and GSK3beta, the downstream molecules of the extracellular matrix-integrin signaling pathways, in HepG2 cells treated with or without Ad-ChM1 were detected by western blot analysis. Luciferase reporter assays of STAT, GAS, and ISRE, which participate in another cytokine signaling pathway, ware performed in HepG2, HeLa, and HUVEC cells.


RESULTS
ChM1 suppressed BrdU incorporation in HUVECs and in HepG2 cells dose-dependently, but did not suppress BrdU incorporation in NHDFs and HeLa cells cultured on plates. In soft agar, however, ChM1 suppressed the growth of HeLa cells, as well as HepG2 cells. Western blot analyses demonstrated that ChM1 decreased the levels of cyclin D1, cyclin D3, and cdk6 and increased those of p21cip1 without affecting the phosphorylation levels of Erk, Akt, and GSK3beta in HepG2 cells. The luciferase reporter assay demonstrated that ChM1 suppressed the transcriptional activities of STAT and GAS but not of ISRE.


CONCLUSIONS
ChM1 directly suppressed the proliferation of tumor cells in an anchorage-independent manner. However, ChM1 did not alter the phosphorylation of downstream molecules, at which the signaling pathways through growth factor and cytokine receptors converge with the anchorage-dependent pathway. Our results show that ChM1 has a direct anti-tumor effect; moreover, this effect occurs by inhibiting the STAT signaling pathway.
Mera
Hisashi
H
Division of Orthopedic Surgery, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan. hisme0214@gmail.com
Kawashima
Hiroyuki
H
Yoshizawa
Tatsuya
T
Ishibashi
Osamu
O
Ali
Md Moksed
MM
Hayami
Tadashi
T
Kitahara
Hiroshi
H
Yamagiwa
Hiroshi
H
Kondo
Naoki
N
Ogose
Akira
A
Endo
Naoto
N
Kawashima
Hiroyuki
H
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000628:therapy; D018797:Cell Cycle Proteins / Q000096:biosynthesis; D045744:Cell Line, Tumor; D004273:DNA, Neoplasm / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005822:Genetic Vectors / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis* / Q000235:genetics; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000628:therapy; D008297:Male; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000628:therapy; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics; D050791:STAT Transcription Factors / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection
D018797:Cell Cycle Proteins; D004273:DNA, Neoplasm; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D011994:Recombinant Proteins; D050791:STAT Transcription Factors; C068675:CNMD protein, human