Mesothelin, a secreted
protein, is overexpressed in some
cancers, including
pancreatic cancer. Rescent studies have shown that overexpression of
mesothelin significantly increased
tumor cell proliferation, and downregulation of
mesothelin inhibited cell proliferation in
pancreatic cancer cells, but its exact function and mechanism remains unclear. The aim of the present study was to evaluate the effects of
mesothelin on proliferation and apoptosis in
pancreatic cancer cells with different p53 status and to explore its signal pathway.
Mesothelin levels were detected by western blot and RT-PCR assay in human
pancreatic cancer AsPC-1, HPAC and Capan-2, Capan-1 and MIA PaCa-2 cell lines.
Mesothelin was slienced by
shRNA in AsPC-1, Capan-2 and Capan-1 cells with rich
mesothelin level, and
mesothelin was overexpressed in the HPAC and Capan-2 cells with less
mesothelin level. We observed that in the AsPC-1 and Capan-1cells with mt-p53, and Capan-2 cells with wt-p53,
shRNA mediated sliencing of the
mesothelin significantly increased PUMA and Bax expression and
caspase-3 activity, and decreased bcl-2 expression, followed by the reduced proliferation and colony forming capability and increased cell apoptosis. When PUMA was slienced by
siRNA in the stable
mesothelin shRNA transfected cells, proliferative capability was significantly increased, and apoptosis was decreased. However, in the Capan-2 cells with wt-p53, suppression of the
mesothelin significantly increased wt-p53 levels. When p53 was blocked by
siRNA in the stable
mesothelin shRNA transfected Capan-2 cells, PUMA was inhibited, followed by increased proliferative capability and decreased cell apoptosis. In the HPAC and Capan-2 cells with wt-p53 and in the MIA PaCa-2 cells with mt-p53, overexpression of the
mesothelin significantly decreased bax levels and increased bcl-2 levels, followed by increased proliferative and colony forming capability. Furthermore,
mesothelin-
shRNA-transfected cells exhibited a reduced rate of
tumor growth under in vivo conditions. However,
mesothelin-transfected cells exhibited a increased rate of
tumor growth under in vivo conditions. Our data demonstrated that
mesothelin promotes proliferation and inhibited apoptosis through p53-dependent pathway in
pancreatic cancer cells with wt-p53, and p53-independent pathway in
pancreatic cancer cells with mt-p53. Targeting
mesothelin by
shRNA is the important method for
pancreatic cancer therapy.