Abstract 4897: Identification of microRNA networks in pancreatic cancer stem cells.
Authors: Hasegawa Shinichiro , Ishii Hideshi , Nishikawa Shimpei , Eguchi Hidetoshi , Kobayashi Shogo , Wada Hiroshi , Hama Naoki , Akita Hirofumi , Kawamoto Koichi , Konno Masamitsu , Ogawa Hisataka , Ohta Katsuya , Kano Yoshihiro , Fukusumi Takahito , Hamabe Atsushi , Nishimura Takenori , Hinohara Kunihiko , Satoh Taroh , Gotoh Noriko , Doki Yuichiro , Mori Masaki , Nagano Hiroaki 
Published: August 2014

Background. Pancreatic adenocarcinoma is a highly lethal disease, which is usually diagnosed in advanced stages for which there are little or no effective therapies. It has the worst prognosis of any major malignancy (3% 5-year survival) and is the fourth most common cause of cancer death yearly in the United States. Recently there have been several reports that the presence of cancer stem cells (CSCs) was related to the high refractoriness in pancreatic cancer. CSCs have two characteristics, self-renewal and differentiation, for maintenance of cancer tissues (Nature, 2001). Given that chemotherapies target generally against differentiated non-CSCs, small populations of CSCs survive and the recurrence of tumor growth will occur. Nevertheless, the underlined mechanism, which links between chemoresistance and stemness, remains to be elucidated. Considering that microRNAs are number-limited, functional nucleotides, those should be beneficial for efficient diagnostic and therapeutic approaches of pancreatic cancer.

Matherials and Methods. Pancreatic cancer Panc1 cells were cultured in the medium containing increasing amounts of gemcitabine (GEM) to obtain several GEM-resistant clones. To identify the microRNAs, which play a critical role in the chemoresistance in pancreatic CSCs, we performed the serum-free floating culture of embryoid body-like structures by quick re-aggregation method (SFEBq), as a tool for separating CSCs; The SFEBq is the method for culture and concentration of neural stem cells, which can concentrate CSCs successfully in several types of cancer. The chemoresistance was studied by the MTT assay. RNAs were extracted, the genome-wide transcriptome was identified and networks were studied between stemness and chemoresistance.

Results. The study of original Panc1 cells and four representative, independent GEM-resistant clones (R1, R2, R3 and R4) allowed the identification of CSC-specific and GEM-specific signal transduction pathways. The data were verified among four resistant clones. By utilizing specific inhibitors including small-molecule compounds and anti-microRNAs, we studied the network cross-talking CSCs and chemoresistance. Even if the SFEBq-enriched CSC clones were not exposed to GEM, their similarity to chemo-specific pathway reinforces that the small populations of CSCs would pre-exist as an innate resistance before treatment in patients. Such cross-talking pathway would be eligible to sensitize pancreatic cancer to chemotherapy, and to eradicate tumors.

Conclusion. The data demonstrate the successful molecular dissection of stemness and chemoresistant pathways, and the present study provides the rationale for novel therapeutic approaches such as modified nucleotide medicines to target the pre-existing CSCs.

Citation Format: Shinichiro Hasegawa, Hideshi Ishii, Shimpei Nishikawa, Hidetoshi Eguchi, Shogo Kobayashi, Hiroshi Wada, Naoki Hama, Hirofumi Akita, Koichi Kawamoto, Masamitsu Konno, Hisataka Ogawa, Katsuya Ohta, Yoshihiro Kano, Takahito Fukusumi, Atsushi Hamabe, Takenori Nishimura, Kunihiko Hinohara, Taroh Satoh, Noriko Gotoh, Yuichiro Doki, Masaki Mori, Hiroaki Nagano. Identification of microRNA networks in pancreatic cancer stem cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4897. doi:10.1158/1538-7445.AM2013-4897