Abstract 5201: MicroRNA 760 regulates gastric cancer progression by downregulation of histone mRNA expression
Authors: Iwaya Takeshi , Fukagawa Takeo , Suzuki Yutaka , Sudo Tomoya , Ishida Kaoru , Kume Kohei , Nishizuka Satoshi , Iinuma Hisae , Mori Masaki , Sasako Mitsuru , Wakabayashi Go , Mimori Koshi 
Published: May 2015

The presence of isolated tumor cells in the peripheral blood (PB) and bone marrow (BM) is an important factor contributing to the metastasis of solid cancers. Moreover, recent studies have demonstrated that various types of host cells are also involved in cancer development and metastasis. BM microenvironment is thought to be a good reflection of the interplay between tumor cells and cancer-associated host cells in metastatic sites compared to the bloodstream. We performed RNA-seq analysis of the BM samples from 8 gastric cancer (GC) patients (Stages I and IV: n = 4 each) in order to identify candidate prognostic markers, and revealed higher expression of multiple histone mRNAs in Stage IV patients. Results were validated through qRT-PCR analysis of HIST1H3D expression in 175 BM, 92 PB, and 115 primary tumor (PT) samples from GC patients. HIST1H3D expression in the BM, PB, and PT of Stage IV patients was higher than that in Stage I patients (p = 0.0284, 0.0243, 0.0006, respectively). In silico analysis revealed that most of the histone genes upregulated in BM samples from Stage IV GC patients had predictive target sites for microRNA 760 (miR-760) in their 3′ UTRs. miR-760 expression was assayed using qRT-PCR in 105 BM and 96 PT samples. In contrast to histone mRNA expression, miR-760 was downregulated in the BM and PT of Stage IV patients compared to Stage I patients (p = 0.0094 and 0.0018, respectively). Direct interaction between miR-760 and histone mRNA was confirmed by luciferase analysis in a GC cell line, NUGC3. HIST1H3D expression was downregulated in 3 GC cell lines (NUGC3, KE39, and KATOIII) after Pre-miR-760 transfection in both mRNA and protein levels. We also examined miR-760 expression levels of noncancerous host cells in samples from GC patients. In BM samples from another set of 4 GC patients, the CD14 positive fraction exhibited the same degree of miR-760 expression compared to a

CD45/EpCAM+ fraction. Moreover, in corresponding noncancerous tissues from primary gastric tumors, miR-760 expression was lower in Stage IV patients than in Stage I patients. These results suggest that changes in miR-760 expression in host noncancerous cells are also associated with GC progression. In conclusion, histone mRNA is upregulated, while miR-760 is downregulated in the BM and PT of advanced GC patients and proposed that the histone mRNA/miR-760 axis may have a crucial role in the development of GC.

Citation Format: Takeshi Iwaya, Takeo Fukagawa, Yutaka Suzuki, Tomoya Sudo, Kaoru Ishida, Kohei Kume, Satoshi Nishizuka, Hisae Iinuma, Masaki Mori, Mitsuru Sasako, Go Wakabayashi, Koshi Mimori. MicroRNA 760 regulates gastric cancer progression by downregulation of histone mRNA expression. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5201. doi:10.1158/1538-7445.AM2014-5201