腫瘤生長時內部會有局部地區呈現缺氧狀態，而這個缺氧狀態對於腫瘤的惡性化以及腫瘤細胞對抗化學治療及放射線治療上扮演著重要的角色。當腫瘤組織處於缺氧狀態的時候，缺氧調控因子 hypoxia-inducible factor-1 (HIF-1)會穩定存在並且累積。 HIF-1是一個heterodimeric 的轉錄因子，在缺氧的情況HIF-1會和hypoxia response element (HRE)作用以調控下游基因的表現。人類的端粒酶反轉錄酶 (human telomerase reverse transcriptase, hTERT) 是端粒酶中主要用來進行催化作用的次單位，大約有百分之九十的癌症細胞上都有大量hTERT的表現。因此hTERT的過度表現通常被認為是腫瘤形成的指標。研究指出在缺氧狀態下端粒酶的活性增加，主要是經由調控hTERT轉錄活性，而HIF-1為之中一個重要的轉錄因子。為了要解決腫瘤在缺氧情況會對化學治療及放射線治療等治療方式產生抵抗反應這個難題，所以我們針對具有缺氧狀態和高活性hTERT的腫瘤設計了一個新的治療策略。我們將6xHRE接上hTERT 的啟動子 (6xHRE-hTERT promoter)去增加它的轉錄活性，並且建構一由這個改造過的啟動子所驅動的溶瘤腺病毒(Ad.WiSh)來治療腫瘤。我們證明在缺氧情況下6xHRE-hTERT 啟動子的活性的確高於原始啟動子的活性。相同的，Ad.WiSh 在缺氧狀態下產生的毒殺作用的能力也優於非缺氧的情況。而在動物實驗中，我們可以發現Ad.WiSh 能更有效的抑制腫瘤的生長以及延長老鼠生存時間。當cisplatin這個常用來治療腫瘤的化學藥物加上hypoxia的情況時，會使的腫瘤細胞有更多的HIF-1表現,進而使得6xHRE-hTERT 啟動子的活性增加,也使得Ad.WiSh對腫瘤細胞有更好的毒殺作用。在動物模式中，同時給予Ad.WiSh和cisplatin做治療時的確可以達到更好的療效。由結果顯示，我們利用6xHRE-hTERT 啟動子驅動的溶瘤腺病毒對於腫瘤的治療有所幫助。

　Hypoxia, a condition that oxygen density is low at local areas, plays a critical role in tumor malignancy and is associated with resistance of cancer cells to conventional chemotherapy and radiotherapy. Hypoxia-inducible factor-1 (HIF-1) is stabilized and accumulated when tissues are exposed to hypoxia. HIF-1 is a heterodimeric transcription factor that regulates the physiologic reaction to hypoxia by binding to hypoxia response element (HRE) of target genes. Human telomerase reverse transcriptase (hTERT), the catalytic subunit of the telomerase is transcriptionally upregulated in about 90% of cancers. Therefore, overexpression of hTERT is considered as a tumorigenesis marker. It has been suggested that hypoxia activates telomerase via transcriptional activation of hTERT, and that HIF-1 plays an important role as a transcription factor. Novel therapeutic strategies to target tumor cells in hypoxia regions with high TERT promoter activity to overcome their resistance to chemotherapy and radiotherapy are urgently needed. Therefore, we have exploited 6 copies of HRE ligated to hTERT promoter to modify the transcription activity of hTERT and constructed AdWiSh (Ad5-6xHRE-hTERT), an oncolytic adenovirus driven by this modified promoter. The transcription activity of the 6xHRE-hTERT promoter has been proved higher than that of the original promoter in hypoxia conditions. Similarly the oncolytic efficacy of AdWiSh under hypoxia is better than under normoxia. Intratumoral injection of AdWiSh resulted in suppressing of tumor growth and prolonging survival in mice bearing subcutaneous Lewis lung carcinoma. Cisplatin combined with hypoxia stimulated HIF-1α upregulation and enhanced 6xHRE-hTERT promoter activity, and Ad.WiSh could have better cytolytic efficacy in this condition. Combination of hypoxia-inducible adenovirus and chemotherapeutic drug cisplatin exhibited higher antitumor efficacy compared with either treatment alone. Taken together, these results suggest that AdWiSh, a 6xHRE-hTERT-driven oncolytic adenovirus may have therapeutic potential for solid tumors.

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