メンバー： 打出毅、伊藤博

分野： 動物生命科学、内科系臨床医学、基礎医学

所属： 農学研究院動物生命科学部門獣医外科学研究室

キーワード： 腫瘍幹細胞、mRNA－133a、イヌ骨肉腫

近年、ヒトの医療では細胞内に発現しているmicroRNAのコントロールを行う「核酸医薬」という考えが注目を集めている。microRNAとは細胞内に存在する長さ21－25塩基長の1本鎖RNAであり、遺伝子発現の抑制を担っているnon-codingRNAである[3]。獣医療の臨床現場において、Synthetic TuDなどを用いた「核酸医薬」が臨床に応用されるまでの過程の中で、標的とするmicroRNAが腫瘍細胞内で発現が亢進しているか、及び、標的microRNAの機能阻害によって転移を抑制することが可能なのか、が重要となる。今回、核酸医薬によるがん治療を目的に、採材した腫瘍組織及び血清からmicroRNA133aの発現や推移、並びに症例の転移や再発の有無を追跡調査した。今回の試験により、犬骨肉腫腫瘍細胞にも、microRNA133aが高次に発現しており、かつそれが予後の指標になり得るとともに骨肉腫の肺転移を抑制することが示唆された。また、この試験の結果により、人医療の核酸医薬が獣医療にも適用でき、またその成果が人医療に還元できることが示唆され、今回得られた結果が今後、担がん犬における核酸医薬の臨床応用での一助になることが言える。

Research members： Tsuyoshi Uchide PhD., Hiroshi ITOH PhD.

Research fields： Animal life science, Clinical internal medicine, Basic medicine

Departments： Veterinary Surgery, Division of Animal Life Science, Institute of Agriculture

Keywords： Cancer stem cell,Synthetic Tough Cecoy RNA,Canine Osteosarcoma

MicroRNAs are short single strand RNA, which function in RNA-silencing and regulate gene expression at post transcriptional level. MicroRNAs involve with cell malignant transformations and acquisition of metastatic ability. In the various tumors, specific miRNA’s expression is induced or suppressed individually. Moreover, by the correction them, it can be observed with the loss of properties of metastasis and resistance to drugs of the cancer.

In human osteosarcoma (OS), it is revealed a small subset cells with over expression of microRNA133a (miR-133a) have abilities to metastasize and resist to drugs, which are suggested relation to cancer stem cells. Moreover, in in-vitro, those abilities disappear by the loss of activity of the miR-133a. Therefore, it is expected radical cure can be practiced if miR-133a can be controlled in case of OS. As a new drug, Synthetic tough decoy RNA (S-TuD) has been invented which differs from current microRNA inhibitor on the point it can depress microRNA’s activity without plasmid or virus vectors. However, it proved only in nude mice transplanted SaOS2-luc cell, therefore the efficiency of S-TuD for dogs bearing cancer is unknown.

Recently, we showed the safety of S-TuD for healthy dogs, and then practiced clinical trial of S-TuD for tumor-bearing dogs. We could have obtained 8 OS cases and one malignant mesenchymal tumor case as subjects for S-TuD clinical test. We performed preoperative administration of S-TuDantimiR-133a 0.1mg/kg twice if it could be done, and amputation tumor. After amputation, we dosed carboplatin and S-TuD in multiple times in all the cases, and then checked recurrence and metastasis. At the same time, we collected sera, tumor tissues, and normal tissues from the cases, then quantitate the expression level of miR-133a by qRT-PCR, with saw how the level changed. As a result, in all cases that we could obtained tumor tissues, miR-133a had expressed, and miR-133a had been observed in all cases sera.

Moreover, in the two cases, the expression level of miR-133a in serum had reduced after dose of S-TuD. But other two cases had been dead in short term. To check efficacy of S-TuD, we have to investigate further whether metastasis or recurrence occur in surviving cases. In this report, we have showed OS cells in dogs express miR-133a, and miR-133a in their serum may be promising biomarkers for prognosis. In addition, S-TuD may be able to reduce the expression level of miR-133a for dogs in serum bearing OS. These results demonstrate the usefulness of the clinical application of nucleic acid medicine for cancer bearing dogs in the future.