TY - JOUR
T1 - Restoration of transforming growth factor-β signaling enhances radiosensitivity by altering the Bcl-2/Bax ratio in the p53 mutant pancreatic cancer cell line MIA PaCa-2
AU - Ahmed, Mansoor M.
AU - Alcock, Rachael A.
AU - Chendil, Damodaran
AU - Dey, Swatee
AU - Das, Anindita
AU - Kolaparthi, Venkatasubbarao
AU - Mohiuddin, Mohammed
AU - Sun, Luzhe
AU - Strodel, William E.
AU - Freeman, James W
PY - 2002/1/18
Y1 - 2002/1/18
N2 - In this study, we investigated whether lack of transforming growth factor β (TGF-β) type II receptor (RII) expression and loss of TGF-β signaling played a role in radiation resistance of pancreatic cancer cells MIA PaCa-2 that possess a mutated p53 gene. Transfection of this cell line with a RII cDNA led to a stimulation of the transcriptional activity of p3TP-Lux, a TGF-β-responsive reporter construct. The RII transfectants (MIA PaCa-2/RII) showed a significant increase in sensitivity to radiation when compared with MIA PaCa-2/vector cells. The increase in sensitivity to radiation was reversed by neutralizing antibodies to TGF-β, indicating that these changes were dependent on TGF-β signaling. Compared with MIA PaCa-2/vector cells, MIA PaCa-2/RII cells showed a greater than 3-fold increase in apoptosis after radiation. Enhanced radiation sensitivity of MIA PaCa-2/RII cells was associated with an induction of Bax mRNA and protein that was followed by a release of cytochrome c and activation of caspase-3 and poly(ADP-ribose) polymerase cleavage after radiation exposure. Overexpression of Bcl-xL or treatment with antisense oligodeoxynucleotides targeted against Bax significantly inhibited radiation-induced apoptosis in MIA PaCa-2/RII but not in MIA PaCa-2/Vector cells, suggesting that Bax induction is necessary for radiation-induced TGF-β signaling-mediated apoptosis. Thus, restoration of TGF-β signaling sensitized these cells to ionizing radiation, although these cells possess a mutated p53 gene. In addition, disruption of RII function by dominant negative mutant of RII inhibited the radiation-induced TGF-β signaling and apoptosis in primary cultures of mouse embryonic fibroblasts. Together, these observations imply that RII is an important component of radiation-induced TGF-β signaling, and loss of function of RII may enhance resistance to radiation-induced apoptosis.
AB - In this study, we investigated whether lack of transforming growth factor β (TGF-β) type II receptor (RII) expression and loss of TGF-β signaling played a role in radiation resistance of pancreatic cancer cells MIA PaCa-2 that possess a mutated p53 gene. Transfection of this cell line with a RII cDNA led to a stimulation of the transcriptional activity of p3TP-Lux, a TGF-β-responsive reporter construct. The RII transfectants (MIA PaCa-2/RII) showed a significant increase in sensitivity to radiation when compared with MIA PaCa-2/vector cells. The increase in sensitivity to radiation was reversed by neutralizing antibodies to TGF-β, indicating that these changes were dependent on TGF-β signaling. Compared with MIA PaCa-2/vector cells, MIA PaCa-2/RII cells showed a greater than 3-fold increase in apoptosis after radiation. Enhanced radiation sensitivity of MIA PaCa-2/RII cells was associated with an induction of Bax mRNA and protein that was followed by a release of cytochrome c and activation of caspase-3 and poly(ADP-ribose) polymerase cleavage after radiation exposure. Overexpression of Bcl-xL or treatment with antisense oligodeoxynucleotides targeted against Bax significantly inhibited radiation-induced apoptosis in MIA PaCa-2/RII but not in MIA PaCa-2/Vector cells, suggesting that Bax induction is necessary for radiation-induced TGF-β signaling-mediated apoptosis. Thus, restoration of TGF-β signaling sensitized these cells to ionizing radiation, although these cells possess a mutated p53 gene. In addition, disruption of RII function by dominant negative mutant of RII inhibited the radiation-induced TGF-β signaling and apoptosis in primary cultures of mouse embryonic fibroblasts. Together, these observations imply that RII is an important component of radiation-induced TGF-β signaling, and loss of function of RII may enhance resistance to radiation-induced apoptosis.
UR - https://www.scopus.com/pages/publications/0037127220
UR - https://www.scopus.com/inward/citedby.url?scp=0037127220&partnerID=8YFLogxK
U2 - 10.1074/jbc.M110168200
DO - 10.1074/jbc.M110168200
M3 - Article
C2 - 11694525
AN - SCOPUS:0037127220
SN - 0021-9258
VL - 277
SP - 2234
EP - 2246
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 3
ER -