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

Mansoor M. Ahmed, Rachael A. Alcock, Damodaran Chendil, Swatee Dey, Anindita Das, Kolaparthi Venkatasubbarao, Mohammed Mohiuddin, Luzhe Sun, William E. Strodel, James W. Freeman

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53 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)2234-2246
Number of pages13
JournalJournal of Biological Chemistry
Issue number3
StatePublished - Jan 18 2002


ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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