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  • br MicroRNAs miRNAs are endogenous small non coding RNA mole

    2020-08-12


    MicroRNAs (miRNAs) are endogenous small non-coding RNA molecules (19–22 nt in length) that regulate protein-coding gene LipoxinA4 by binding to the 30 UTR of mRNAs. Increasing evidence suggests that miRNAs are aberrantly expressed in various human cancers and that they play significant roles in cancer initiation, development, and metastasis.5–7 miRNAs potently influence cellular activities through the regulation of extensive gene expression net-works. Our team has been focusing on the studies for the develop-ment of RNA medicine targeting plural genes through RNAi by the replacement of tumor suppressor (TS)-miRNAs. miR-143 is one of the representative TS-miRNAs that is poorly expressed in a variety of cancers, including BC.8–10 miR-143 has been shown to act as a tumor suppressor in non-small-cell lung cancer,11 cervical cancer,12
    prostate cancer,13 ovarian cancer,14 colon cancer,15 and leuke-mia16,17 and to silence not only K-RAS18 but also RAS-effector
    signal genes Erk and Akt.19 So far, we have been exploring the development of RNA medicine of miR-143 for RAS-driven cancers, because miR-143 perturbs K-RAS-signaling networks systematically.20
    The RAS gene, which is expressed as 3 isoforms, K-RAS, H-RAS, and N-RAS, is one of the most well-known oncogenes,21 and the fre-quency of mutations of both K-RAS and H-RAS has been reported to be almost 10% in BC.22 The contribution of the RAS gene to the
    Correspondence: Yukihiro Akao, MD, United Graduate School of Drug Discovery
    and Medical Information Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193,
    Japan.
    E-mail: [email protected]
    This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
    www.moleculartherapy.org
    Table.1. Clinicopathological Patient Features
    Case
    Age
    Sex
    Grade
    T Stage
    CIS
    RAS
    Meta
    M
    pTa
    no
    D
    U
    M
    no
    D
    U
    M
    no
    D
    U
    F
    no
    D
    U
    M
    no
    D
    U
    M
    no
    D
    U
    M
    yes
    D
    U
    M
    no
    D
    U
    F
    no
    D
    U
    M
    yes
    D
    U
    M
    pTa
    no
    D
    U
    F
    pTa
    yes
    D
    U
    M
    pTa
    fair
    D
    U
    M
    fair
    D
    U
    M
    pTa
    fair
    D
    U
    M
    yes
    D
    U
    M
    pTa
    no
    D
    U
    M
    pTa
    no
    D
    U
    M
    pTa
    no
    D
    U
    no
    D
    M, male; F, female; U, upregulation RAS expression level; D, downregulation of miR-143 relative ratio; grade 1, well-differentiated type carcinoma; grade 2, moderately differentiated type carcinoma; grade 3, poorly differentiated type carcinoma; pTa, papiloma non-invasive carcinoma; pT1, non-muscle-invasive carcinoma; pT2, muscle-invasive carcinoma; CIS, carcinoma in situ; Meta, metastasis.
    pathogenesis of BC has already been reported,21,23 but the detailed mechanism has not been elucidated.
    In this study, we examined the expression levels of RAS and miR-143 in human BC clinical samples, including some CISs, and we clarified the correlation between them. For the development of RNA medicine against RAS-driven cancers, we produced more than 100 chemically modified miR-143 derivatives. Among them, we found an RNase-resistant and potent miR-143 that was chemically modified only in the guide strand. By using this miR-143, we were able to unveil the networks of RAS-signaling pathways and the oncogenic roles of K-RAS and H-RAS in BC cells, and we showed the possibility that the novel synthetic miR-143 would be applied to early BC by intraves-ical infusion. 
    expression levels of total RAS, K-RAS, and H-RAS were evaluated by performing western blot analysis of the same clinical samples. In all cases tested, K-RAS and H-RAS protein expression levels were significantly increased in the BC tumors compared with those in the normal tissue samples (Figure 1B). Importantly, both K-RAS and H-RAS were upregulated in the tumor samples, and an inverse correlation was found between miR-143 and K-RAS or H-RAS (Fig-ure 1C). On the other hand, a positive relation was found between H-RAS and K-RAS (Figure 1C). Also, dataset analysis of 1,314 sam-ples of various BC showed that K-RAS mutation was in 86 cases (7%), H-RAS mutation was in 71 cases (5%), and N-RAS mutation was in 28 cases (2.1%) (Figure S1A). These findings suggested that not only H-RAS but also K-RAS might play pivotal roles in the pathogenesis of BC and that their overexpression in the tumor samples was closely associated with the downregulation of miR-143.