TGF-Beta Signaling and Radiation Response in Pancreatic Cancer

Pancreatic carcinoma is the fourth leading cause of cancer mortality in the US, with more than 28,000 people deaths attributed to the disease each year. For all stages combined, the 1 -year relative survival rate is only 20 percent, and the 5-year rate is 4 percent. Surgery, radiation therapy, and chemotherapy are treatment options, but generally have little influence on the outcome. Gene expression studies revealed that there exist more than one pathways regulating growth inhibition and apoptosis processes. Of these, one pathway, which is mediated through TGF-B signaling for negative growth regulation, is pivotal in inhibiting tumor progression. Our recent preliminary experiments in pancreatic tumors showed that there exists aberrant expression of genes downstream to TGF-B pathway, particularly, in TGF-B type II (RII) receptor and DPC-4. In addition, we also observed that the loss of RII expression contributed to enhanced radiation resistance. Influence of aberrant TGF-B pathway on radiation treatment response remains to be understood. Based on our preliminary findings, we hypothesize that the dysregulation of TGF-p signaling due to lack of RII or DPC-4 expression will cause an impact on radiation response. Thus, to test this hypothesis, the following specific aims are proposed. A. Determine the functional and regulatory role of TGF-B signaling on radiation-induced clonogenic inhibition and apoptosis in pancreatic cancer cell lines harboring aberrant expression of RII and/or DPC-4. Induction of TGF-B signaling by ionizing radiation and p53 functional status will be established. B. Determine the basal and radiation-inducible expression levels of TGF- B effector genes, p2lwafl/cipl and Bax (a presumed TGF- B signaling effector based on our preliminary data) as a function of radiation dose by reporter assays, inimunohistochemistry, Western blot, reverse transcription-polymerase chain reaction and RNase protection assay. Data obtained on TGF-B effector genes (basal and radiation-inducible) will be compared to those corresponding to clonogenic survival (analyzed by colony-forming assay) and apoptosis (analyzed by TUNEL and flow cytometry) profiles. In this way the functional role of TGF-B signaling in radiation treated pancreatic cancer cells can be elucidated.