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01.12.2012 | Research | Ausgabe 1/2012 Open Access

Molecular Cancer 1/2012

Targeting of MAPK-associated molecules identifies SON as a prime target to attenuate the proliferation and tumorigenicity of pancreatic cancer cells

Molecular Cancer > Ausgabe 1/2012
Toru Furukawa, Etsuko Tanji, Yuko Kuboki, Takashi Hatori, Masakazu Yamamoto, Kyoko Shimizu, Noriyuki Shibata, Keiko Shiratori
Wichtige Hinweise

Electronic supplementary material

The online version of this article (doi:10.​1186/​1476-4598-11-88) contains supplementary material, which is available to authorized users.

Competing interests

TF applied a patent on siRNAs used in this study. Other authors declare that they have no competing interests.

Authors’ contribution

TF designed the study. TF and ET carried out in vitro and in vivo experiments and analyzed data. TF, YK, TH, MY, KShim, NS and KShir obtained, examined and analyzed surgical materials. TF wrote the manuscript. All authors had final approval of the submitted and published versions.



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 hypothesized that knockdown of these MAPK-associated molecules could produce notable anticancer phenotypes.


A 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.


The 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.


These 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.
Additional file 1: Table S1. Short interfering RNAs used in a systematic knockdown screening of MAPK-assoicated genes in pancreatic cancer. (PDF 37 KB)
Authors’ original file for figure 1
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