2013 Fiscal Year Final Research Report

Identification of microRNA that correctly inhibits KRAS-related downstream signal transduction in KRAS mutant colorectal cancer

Research Project

Project/Area Number	24659608
Research Category	Grant-in-Aid for Challenging Exploratory Research
Allocation Type	Single-year Grants
Research Field	Digestive surgery
Research Institution	Osaka University
Principal Investigator	YAMAMOTO Hirofumi 大阪大学, 医学(系)研究科(研究院), 准教授 (30322184)
Project Period (FY)	2012-04-01 – 2014-03-31
Keywords	KRAS / colorectal cancer / microRNA / RAF/MEK/ERK pathway / PI3K/Akt pathway / carbonate apatite / nanoparticle
Research Abstract	The antiEGFR monoclonal antibodies are effective in patients with metastatic CRC with KRAS wild type. However, KRAS mutant mCRC shows resistance to the antiEGFR antibodies. To identify miRNAs that inhibit KRAS mutant CRCs, we first introduced KRASG12V cDNA into HEK293 and MRC5. After miRNA microarray analyses we searched which candidate miRNAs would inhibit two major KRAS-associated signal transduction pathways using SRE and AP1 luciferase reporter assays. And we found 2 miRNAs. miR-4689 regulated not only RAF/MEK/ERK pathway but also PI3K/Akt pathway by directly binding to both 3UTR of KRAS and the coding sequence of Akt1. Down-regulation of Akt1 led to sequential induction of pro-apoptotic factors and inhibition of anti-apoptotic molecules. Systemic administration of miR-4689 with super carbonate apatite nanoparticles in nude mice significantly inhibited the growth of pre-established DLD1 xenografts compared to miR-NC with a proof of down-regulation of KRAS and Akt1.