Figure 3

Inhibition of Notch Pathway Results in the Loss of Tumor Phenotype and a Decrease in Proliferation. (A) Inhibition of Notch signaling pathway using the dominant-negative Notch3 receptor (DN) and MRK003 markedly reduces the size of the colonies formed in soft agar of pancreas cancer cell line BxPC3, compared with control. (B) Similar to our previous observation in lung cancer, inhibition of Notch pathway using the DN receptor enhances cancer cells dependency on exogenous growth factor. Cells transfected with the DN construct shows a higher death rate in 0% serum, measured using PI staining, compared to control and cells grew in 10% fetal calf serum (FCS). (C). Using siRNA, loss of Notch3 reduces expression of Bcl-2 family proteins such as Bcl-xL and Bcl-2 in BxPC3. (D) A similar result is obtained when the γ-secretase inhibitor MRK003 is used. Loss of Bcl-xL also coincides with the increase in cleaved PARP, a measure of apoptosis. (E) Both γ-secretase inhibitors DAPT (10 mg/kg i.p.) and MRK003 (100 mg/kg, given through oral gavage in 3 consecutive days/week) attenuate tumor growth in K399 and K162 subcutaneous xenograft models.