Abstract
BackgroundPancreatic cancer is characterized by constitutive activation of mitogen-activated protein kinase (MAPK). Activation of MAPK is associated with the upregulation of genes implicated in the proliferation and survival of pancreatic cancer cells. We hypothesized that knockdown of these MAPK-associated molecules could produce notable anticancer phenotypes.MethodsA RNA interference-mediated knockdown screening of 78 MAPK-associated molecules previously identified was performed to find molecules specifically associated with proliferation of pancreatic cancer cells in vitro. Expression of an identified molecule in pancreatic cancer tissues was examined by immunohistochemistry. In vivo tumorigenicity of cancer cells with stable knockdown of the molecule was assayed by using xenograft models. Flow cytometry and live cell imaging were employed to assess an association of the molecule with cell cycle.ResultsThe knockdown screening revealed that knockdown of SON, the gene encoding SON, which is a large serine/arginine-rich protein involved in RNA processing, substantially suppressed pancreatic cancer cell proliferation and survival in vitro and tumorigenicity in vivo. SON expression was higher in ductal adenocarcinomas than in cells of normal ducts and precursor lesions in pancreatic cancer tissues. Knockdown of SON induced G2/M arrest and apoptosis in cultured cancer cells. The suppressive effect of SON knockdown on proliferation was less pronounced in cultured normal duct epithelial cells. SON formed nuclear speckles in the interphase of the cell cycle and dispersed in the cytoplasm during mitosis. Live cell imaging showed that SON diffusely dispersed in the early mitotic phase, accumulated in some foci in the cytoplasm in the late mitotic phase, and gradually reassembled into speckles after mitosis.ConclusionThese results indicate that SON plays a critical role in the proliferation, survival, and tumorigenicity of pancreatic cancer cells, suggesting that SON is a novel therapeutic molecular target for pancreatic cancer.
Highlights
Pancreatic cancer is characterized by constitutive activation of mitogen-activated protein kinase (MAPK)
Knockdown screening of MAPK-modulated genes in pancreatic cancer cells We performed knockdown screening using a pancreatic cancer cell line, MIA PaCa-2, and custom-designed short interfering RNAs targeting all the 78 MAPKmodulated genes that were previously identified and isolated in the cell line (Additional file 1: Table S1) [9]
Knockdown of aurora kinase B (AURKB), centromere protein A (CENPA), EBNA1BP2, Golgi transport 1A (GOLT1A), kinesin family member 11 (KIF11), Neural precursor cell expressed (NEDD4L), SON, Tpx2 of Xenopus (TPX2), or WD repeat domain 5 (WDR5) suppressed proliferation by more than 50% compared with control
Summary
Pancreatic cancer is characterized by constitutive activation of mitogen-activated protein kinase (MAPK). Activation of MAPK is associated with the upregulation of genes implicated in the proliferation and survival of pancreatic cancer cells. We screened the genome for downstream targets of MAPK and identified 78 molecules associated with MAPK activity in pancreatic cancer cells [9]. These MAPK-associated molecules include molecules implicated in DNA replication, RNA editing, spindle formation, mitosis, signal transduction, and membrane trafficking. These biological processes play critical roles in the survival, maintenance, and proliferation of pancreatic cancer cells. We performed a systematic knockdown screening of MAPK-associated molecules in pancreatic cancer cells
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