Deep-Sequencing Reveals Specific microRNAs in An Autoregressive Tumor Model

微小核醣核酸（microRNAs, miRNAs）是一種長約18-25個核苷酸的小分子非編碼核醣核酸（non-coding RNA），廣泛存在於真核生物中。miRNA的表現具有細胞或組織特異性，能針對特定的基因群進行轉錄後抑制作用，進而調控細胞生長發育、分化以及凋亡。近年來，多方證據顯示，miRNA的異常表現和腫瘤的發生、生長和轉移息息相關。因此，發展以miRNA為基礎的生物標誌分子作為腫瘤疾病的診斷依據、預後指標，或是治療的標的已經漸成研究趨勢。犬傳染性花柳病 （canine transmissible venereal tumor, CTVT）是一種在犬間自然發生的傳染性腫瘤疾病。以實驗室方法接種CTVT細胞或組織團塊於犬隻，建立CTVT生長週期，能夠隨時間進行觀察到發展期（progressive phase）、穩定期（stable phase）、消退期（regressive phase） 等三個顯著不同的腫瘤時期。其中，CTVT獨特的自發性消退現象，正好可以提供一套由生長發展到死亡的完整腫瘤模式以作研究用途。我們計畫以CTVT作為研究miRNA的基礎，探討參與在腫瘤發生及腫瘤抑制的相關機制。在本研究中，我們以次世代定序技術（next generation sequencing, NGS）揭示了在CTVT不同生長時期所表現的特異miRNA族群，進而挑選出顯著表現於腫瘤消退期的miRNA序列，並以即時定量聚合酶鏈鎖反應（real-time quantitative polymerase chain reaction, RT-qPCR）技術在不同個體來源樣品進行生物性重複測試，找到可能參與腫瘤自發性消退現象的miRNA，並配合CTVT轉錄體核酸探針微陣列（transcriptome microarray）及miRNA目標預測軟體，進一步找出潛在的下游調控路徑。我們期待藉由了解miRNA在腫瘤消退中所扮演的角色，在未來找到有效對抗腫瘤的方法。MicroRNAs (miRNAs) are a rapidly expanding class of non-coding RNAs, which can be expressed in a cell- and tissue-specific manner. Mature miRNAs are about 18-25 nt, known to work in post-transcriptional regulations. They are active in the processes of development, apoptosis, and differentiation. Strong evidence has also emerged that miRNAs are key molecules involved in cancer initiation, progression, and metastasis. The involvement of miRNAs in all stages of cancer development opens the possibility for miRNA-based diagnosis, prognosis, or even therapeutics. Canine transmissible venereal tumor (CTVT) is a naturally occurring clonally transmissible cancer. The tumor can be transplanted by the direct contact of cancer cells or tumor tissue between individuals. Experimentally transferred CTVT have three distinct phases of growth, described as progressive, stable and regressive phases. The dramatic autoregression phenomenon in CTVT is uncommon to most kind of tumors, and it provides a complete tumor lifecycle to study for. We planned to take CTVT as an extra vision to study miRNA-mediate tumor suppression or oncogenesis. Furthermore, it has been reported that miRNAs in circulating systems are extremely stable, and have the potential to connect with distant cells. In the consideration of all the tumors grow on one dog would regress simultaneously, we believe that there are communications between tumors and host via the circulating system, and it is worth to keep an eye on sera-miRNAs. In this study, we revealed specific miRNAs possibly involved in the autoregression phenomenon in CTVT lifecycle through next generation sequencing (NGS), and confirmed the screening strategy by qRT-PCR upon biological repetitive individuals. For understanding the probable downstream regulatory network of miRNA-drived tumor life cycle, the predicted targets of these miRNAs were then integratively analyzed with the CTVT tissue gene expression data obtained from transcriptome microarray analysis. Together, the investigation of miRNAs in this autoregressive tumor model may provide valuable hints for tumor development and contribute to the therapeutic applications for cancer treatments