類胰島素生長因子之訊息傳遞於調控人類睪丸癌多功能性之探討

目前的研究證實IGF-1R所傳遞之細胞訊息，可能藉由促進細胞增生、存活，進一步使細胞轉型為惡性腫瘤。Oct-4蛋白已知是專一表現在胚胎幹細胞及精原幹細胞之轉錄因子；而在人類生殖細胞瘤中，Oct-4也被證實有過度表現。臨床病理檢測發現，人類生殖細胞瘤中精細胞癌（seminoma）及胚胎癌（embryonal carcinoma）不但高度表現Oct-4，同時也高度表現IGF-II；同時由Bendall研究團隊證實，IGF-1R所傳遞之細胞內訊息對於人類胚胎幹細胞維持全能性是扮演重要的角色；人類胚胎幹細胞可能藉由其自身分化出的類似纖維母細胞分泌IGF-II，進而活化IGF-1R途徑，使得人類胚胎幹細胞自我更新。本實驗室先前的研究發現IGF-1R之訊息傳遞可維持精原幹細胞 Oct-4的表現及其多功能性，因此我們假設過度活化的IGF-1R之訊息傳遞導致多功能精原幹細胞中Oct-4過度表現，進而使之癌化為癌細胞之原因之一。我們以 NT2 及 NCCIT 細胞株為模式，想了解 IGF-1R 途徑是否會影響這株胚胎癌細胞的 Oct-4 表現及其多功性表現，而進一步去了解 IGF-1R 於精原幹細胞轉型為生殖癌幹細胞的角色。我們實驗結果證實抑制 IGF-1R 途徑會抑制 NT2 細胞株 Oct-4 的表現，並走向分化途徑；外加 IGF-I 及 IGF-II 則會使 NT2 細胞 Oct-4 表現上升。以shRNA knockdown IGF-1R 表現，NT2 細胞株 Oct-4 表現下降。然而 NCCIT 細胞對於 IGF-1R 調控 Oct-4 表現的情形不明顯。綜合以上的結果，強烈暗示 IGF-I / IGF-1R 訊息途徑調控生殖細胞多功能性及腫瘤生成。我們的結論是 IGF-I / IGF-1R 訊息傳遞調控生殖腫瘤細胞的多功能性，未來可進一步做為臨床上癌症治療的目標之一。

關鍵字

類胰島素生長因子；生殖腫瘤

並列摘要

Recent studies demonstrated that the IGF-1R signaling might promote the cell proliferation, survival, and drive cells undergoing EMT transition to be malignant tumors. Oct-4 protein is known as transcription factor specifically displayed in embryonic stem cells (ES cells) and germline stem cells. In human germ cell tumors, Oct-4 is overexpressed in seminomas and embryonal carcinomas (ECs). Further clinical evidence suggested that human seminoma and ECs also highly express growth factors IGF-I and IGF-II. This result is similar to that of hES cells which depend on the IGF-1R signaling to maintain their self-renew and pluripotency. Our previous studies indicated that the pluripotency of mouse germline stem cells was maintained by the IGF-I dependent pathway (2009, The FASEB J). To further identify the role of IGF-I/ IGF-1R signaling in pluripotent germ cell tumors, we used NT2 and NCCIT cells as model to examine the effect of IGF-I/ IGF-II/ IGF-IR signaling on the germ cell pluripotency. In our study, by utilizing both real-time PCR and Western blotting, we observed the up-regulation of pluripotent Oct-4 protein in NT2 and NCCIT cells (the pluripotent germ cell tumors). Further study using PPP (a specific inhibitor for IGF-1R phosphorylation) to block the IGF-I/ IGF-1R signaling, the downregulation of Oct-4 as well as neuron-like differentiation of NT2 cell were demonstrated. Exogeneous addition of IGF-I and /or IGF-II in medium significantly increased the Oct-4 expression level in NT2 cells. Furthermore, down-regulation of IGF-1R expression by shRNA siginificantly suppressed the IGF-1R as well as the Oct-4 expression in NT2, but not in NCCIT cells. Together with these observations strongly suggested the maintenance of germ cell pluripotency and tumorigenesis by IGF-I/ IGF-1R-mediated signals. In summary, here we presented the regulation of IGF-I/ IGF-1R signaling in pluripotent germ cell tumors. This finding may contribute to important clinical therapeutic targeting for cancer treatment.

並列關鍵字

insulin like growth factor；germ cell tumor

參考文獻

Reference List

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類胰島素生長因子之訊息傳遞於調控人類睪丸癌多功能性之探討

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