TY - JOUR
T1 - Autocrine transforming growth factor-β growth pathway in murine osteosarcoma cell lines associated with inability to affect phosphorylation of retinoblastoma protein
AU - Navid, Fariba
AU - Letterio, John J.
AU - Yeung, Choh L.
AU - Pegtel, Michiel
AU - Helman, Lee J.
PY - 2000
Y1 - 2000
N2 - Purpose. Production of active transforming growth factor-β (TGF-β) by human osteosarcoma may contribute to malignant progression through mechanisms that include induction of angiogenesis, immune suppression and autocrine growth stimulation of tumor cell growth. To study events associated with induction of cell proliferation by TGF-β, we have evaluated the TGF-β pathway in two murine osteosarcoma cell lines, K7 and K12. Results. Northern and immunohistochemical analyses show that each cell line expresses TGF-β1 and TGF-β3 mRNA and protein. Both cell lines secrete active TGF-β1 and display a 30-50% reduction in growth when Cultured in the presence of a TGF-β blocking antibody. Expression of TGF-β receptors TSSRI, TSSRII and TSSRIII is demonstrated by affinity labeling with 125I-TGF-β1, and the intermediates, Smads 2, 3 and 4, are uniformly expressed. Smads 2 and 3 are phosphorylated in response to TGF-β, while pRb phosphorylation in each osteosarcoma cell line is not affected by either exogenous TGF-β or TGF-β antibody. Conclusions. The data implicate events downstream of Smad activation, including impaired regulation of pRb, in the lack of a growth inhibitory response to TGF-β, and indicate that this murine model of osteosarcoma is valid for investigating the roles of autocrine TGF-β in vivo.
AB - Purpose. Production of active transforming growth factor-β (TGF-β) by human osteosarcoma may contribute to malignant progression through mechanisms that include induction of angiogenesis, immune suppression and autocrine growth stimulation of tumor cell growth. To study events associated with induction of cell proliferation by TGF-β, we have evaluated the TGF-β pathway in two murine osteosarcoma cell lines, K7 and K12. Results. Northern and immunohistochemical analyses show that each cell line expresses TGF-β1 and TGF-β3 mRNA and protein. Both cell lines secrete active TGF-β1 and display a 30-50% reduction in growth when Cultured in the presence of a TGF-β blocking antibody. Expression of TGF-β receptors TSSRI, TSSRII and TSSRIII is demonstrated by affinity labeling with 125I-TGF-β1, and the intermediates, Smads 2, 3 and 4, are uniformly expressed. Smads 2 and 3 are phosphorylated in response to TGF-β, while pRb phosphorylation in each osteosarcoma cell line is not affected by either exogenous TGF-β or TGF-β antibody. Conclusions. The data implicate events downstream of Smad activation, including impaired regulation of pRb, in the lack of a growth inhibitory response to TGF-β, and indicate that this murine model of osteosarcoma is valid for investigating the roles of autocrine TGF-β in vivo.
KW - Osteosarcoma
KW - Retinoblastoma protein
KW - Smad proteins
KW - Transforming growth factor-β
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U2 - 10.1080/13577140020008057
DO - 10.1080/13577140020008057
M3 - Article
C2 - 18521287
AN - SCOPUS:0033638672
SN - 1357-714X
VL - 4
SP - 93
EP - 102
JO - Sarcoma
JF - Sarcoma
IS - 3
ER -