低氧壓力與胰島素生長因子第一型訊息之交互作用對小鼠精原幹細胞的多功能性之探討

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Title:	低氧壓力與胰島素生長因子第一型訊息之交互作用對小鼠精原幹細胞的多功能性之探討 Cross-talking of Hypoxia Stress and IGF-1 Signaling in Pluripotent Regulation of Mouse Germline Stem Cells
Authors:	陳怡君 Yi-Chun Chen
Contributors:	醫學科學研究所
Keywords:	低氧胰島素生長因子第一型精原幹細胞 Hypoxia IGF-1 Germline stem cells
Date:	2009
Issue Date:	2009-09-15 10:45:59 (UTC+8)
Abstract:	癌幹細胞 (cancer stem cells, CSCs) 被認為存在於腫瘤細胞之中，而關於CSCs的起源，則不清楚。目前CSCs被認為可能是來自於正常的幹細胞 (例如glioma CSCs和intestine CSCs)，因為基因的不穩定性或是導因於微環境 (niche) 中對細胞的壓力 (如低氧，hypoxia) 所產生的刺激，可能是誘使幹細胞轉形 (transformation) 變成CSCs的原因。然而，目前關於低氧環境下誘導幹細胞轉形為癌幹細胞之相關機轉的研究，仍非常有限。臨床疾病中，我們可以發現在human pluripotent testicular tumors (包括seminomas和embryonal carcinomas) 的組織中，表現大量HIF-1α、HIF-2α和IGF-1蛋白，高度暗示著在多功能幹細胞睪丸癌中，hypoxia stress與IGF-1 signaling間的交互作用。我們實驗室已成功的建立了serum-free stem-niche cell 共同培養的系統，能將新生小鼠的睪丸細胞在體外培養成多功能性精原幹細胞 (AP+GSCs)；並且藉此發現IGF-1/IGF-1R signaling可以維持AP+GSCs的多功能性。有趣的是，當與normoxia (21 % O2) 相對照，可以發現在hypoxia (5 % O2) 培養下的AP+GSCs，表現高度鹼性磷酸酶活性 (AP)、細胞增生速率、HIF-1α、HIF-2α和Oct-4蛋白以及pluripotent gene (像是Oct-4、Sox2、Nanog、Klf4和c-Myc) 的表現。除此之外，IGF-1和IGF-1R在hypoxia下的表現量也都會增加。進一步給與PPP (IGF-1R的抑制劑) 和LY294002 (PI3K的抑制劑) 於AP+GSCs培養液中，發現Oct-4、HIF-1α和HIF-2α的蛋白表現量都會有顯著的下降，暗示IGF-1 signaling可以調控Oct-4和HIF-2α的表現。綜合以上結果，證明了hypoxia會與IGF-1 signaling共同調控AP+GSCs 之stemness (Oct-4、Sox2、Nanog和Klf4) 與 tumor factor (c-Myc) 的表現，促使幹細胞在hypoxia下進行轉化 (transformation)。 Recent advances in cancer research suggest that existance of cancer stem cells (CSCs) in tumor tissues. The origin of CSCs are still controversial; but it has been proved CSCs are possibly originated from organ stem cells (e.q. glioma CSCs and intestine CSCs). The niche stress such as hypoxia effect may provide external signals in stem cell transformation. However, the mechanism of hypoxia-induced stem cell transformation still remains unclear. Our preliminary observations in human pluripotent testicular tumors (seminomas and embryonal carcinomas) showed a high level of hypoxia-inducible protein HIF-1α/HIF-2α as well as IGF protein expression in tissues. This observation strongly highlights the cross-talking of niche hypoxic stress and IGF-1 signaling in transformation of germline stem cells into pluripotent cancers. To address this point, we have successfully established a serum-free stem-niche cell co-culture system to generate pluripotent germline stem cells from neonatal mouse testis (AP+GSCs), and uncovered the role of IGF-1/IGF-1R signaling in germ cell pluripotency. Interestingly, while comparing with the normoxia ( 21 % O2), the AP+GSCs showed in a dramatically increase of alkaline phosphatase activity (AP), cell proliferation, HIF-1α, HIF-2α, Oct-4 protein expression, and pluripotent gene expression (such as Oct-4, Sox2, Nanog, Klf-4, and c-Myc) under hypoxia condition (5 % O2). Moreover, the IGF-1 and IGF-1R expression were also significantly increased under hypoxia. Further analysis by using PPP (a specific inhibitor of IGF-1R phosphorylation) and/or LY294002 (a specific PI3K inhibitor) treatment dramatically reduced the Oct-4 expression as well as HIF-1??/HIF-2???nprotein of AP+GSCs. These results highlight the regulation of Oct-4/HIF-2α expression by IGF-1/IGF-1R signaling. In summary, our results demonstrated an up-stream regulation of stemness (Oct-4, Sox2, Nanog, and Klf-4) and tumor factor (c-Myc) of AP+GSCs which was cross-talking with IGF-1/IGF-1R signaling in stem cell transformation under hypoxia condition.
Data Type:	thesis
Appears in Collections:	[Graduate Institute of Medical Sciences] Dissertation/Thesis

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