探討致糖尿病因子S100A9於胰臟癌誘發糖尿病之角色及臨床應用

To Investigate The Role of Diabetogenic Factor S100A9 in Pancreatic Cancer-Associated Diabetes Mellitus and Its Clinical Application

陳芃瑞(Peng-Ruei Chen)

指導教授 ： 周綠蘋

國立臺灣大學/醫學院/生物化學暨分子生物學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201900222

摘要

胰臟癌是目前全球癌症致死率排名中的第三位，在常見的癌症中，胰臟癌擁有最低的5年存活率。85%的病患被診斷出胰臟癌時已至晚期，因其缺乏早期診斷的方法。過去的研究指出，大約40%的胰臟癌患者在被診斷出胰臟癌的前兩年內會發生糖尿病，此種胰臟癌誘發之糖尿病是一個早期發現胰臟癌的機會。鑑於胰臟癌誘發之糖尿病是由腫瘤分泌的致糖尿病因子所導致，鑑定該致糖尿病因子為何，能夠幫助我們了解致病的機制，及提供區分胰臟癌誘發之糖尿病與第二型糖尿病的生物標記。
在實驗室先前的研究中，我們收集了胰臟癌細胞株的分泌性蛋白，並透過蛋白質體學、DNA微陣列及生物資訊分析結果，鑑定出S100A9作為致糖尿病因子的候選蛋白。並且於後續的實驗，發現S100A9能抑制肌肉細胞攝取葡萄糖的能力，並且觀察到S100A9高表現於胰臟癌組織及周圍基質的現象，說明S100A9可能在新生糖尿病的形成中扮演角色。
在本篇中，我們為了評估S100A9作為生物標記的能力，我們收集了臨床上六組病患的血清檢體，分別為健康人、第二型糖尿病、胰臟癌新生糖尿病、無糖尿病之胰臟癌、胰臟炎，及其他胰臟腫瘤族群。我們發現血清SX
A9濃度於胰臟癌新生糖尿病患者相較於其它族群顯著提高，並且經ROC分析得到S100A9能夠區分胰臟癌新生糖尿病及第二型糖尿病的結果。我們進一步探討生物標記的分析，發現合併S100A9及CA19-9兩種血液生物標記，得到比兩者單獨使用更佳的區分效果。
此外，我們也探討了致糖尿病因子S100A9於新生糖尿病中扮演的角色。結果顯示S100A9能夠藉由與TLR4交互作用造成胰島素阻抗。TLR4下游的IKKβ因Ser181磷酸化而活化，進而將IRS-1的抑制型Ser307位點磷酸化，造成IRS-1活性下降，導致下游Akt的磷酸化被抑制，胰島素訊息傳遞被阻礙。
總結本篇研究，我們證實S100A9可作為診斷PCDM的潛力生物標記，並且合併S100A9與CA19-9可以在胰臟癌的早期偵測達到更佳的效果。此外，我們也證明S100A9會藉由與TLR4的交互作用造成胰島素阻抗。我們的實驗成果可幫助我們釐清胰臟癌導致新生糖尿病的機制，以及提供一個新的胰臟癌早期偵測研究方向。

關鍵字

胰臟癌 ； 新生糖尿病 ； 胰島素阻抗 ； 生物標記 ； S100A9

並列摘要

Pancreatic cancer (PC) is the third leading cause of cancer-related deaths in the world with the lowest 5-year survival among major cancers. 85% of patients are diagnosed at advanced stage owing to the lack of early-stage detection methods. Previous studies demonstrated that approximately 40% patients of PC develop pancreatic cancer-associated diabetes mellitus (PCDM) within 2 years preceding the diagnosis of PC, providing a window of opportunity for early detection. Given that PCDM is mediated by unknown tumor-secreted diabetogenic factors, identifying the diabetogenic factors may help understand its pathogenesis and discover novel biomarkers to discriminate PCDM from type 2 diabetes mellitus (T2DM).
In our previous studies, we identified S100A9 as a candidate diabetogenic factor in condition media (CM) of two pancreatic cancer cell lines (MiaPaCa-2 and PANC-1) by LC-MS/MS combining DNA microarray. We produced S100A9 recombinant protein and discovered that S100A9 can reduce glucose uptake in C2C12 cells. Besides, we also found that S100A9 is highly expressed both in cancer cells and tumor stroma of PCDM. The results revealed that S100A9 played an important role in PCDM.
To evaluate the usefulness of S100A9 as a diagnostic biomarker, we collected different groups of patients’ samples, including normal healthy control, type 2 diabetes mellitus (T2DM), PC without DM, PCDM, pancreatitis, and other pancreatic tumors. We found that serum S100A9 concentration was higher in PCDM than in other groups and could distinguish PCDM from T2DM. Furthermore, the combination of S100A9 and CA19-9 constituted a more discriminatory panel than either marker alone.
In addition, we investigated the role of diabetogenic factor S100A9 in PCDM. Our results showed that S100A9 caused insulin resistance through interacting with Toll-like receptor 4 (TLR4), which activates IκB kinase-β (IKK-β) by Ser181 phosphorylation. The phosphorylated IKK-β then stimulates inhibitory Ser307 phosphorylation of insulin receptor substrate-1 (IRS-1) and therefore suppresses activating Ser 473 phosphorylation of Akt and downstream insulin signaling.
In conclusion, we verified S100A9 was a potential diagnostic biomarker for PCDM, and the combination of S100A9 and CA19-9 may facilitate early detection of PC. Moreover, we demonstrated that S100A9 caused insulin resistance through interacting with TLR4. Our results can help us not only for clarifying the pathogenesis of PCDM, but also for early detection of pancreatic cancer.

並列關鍵字

Pancreatic cancer ； diabetes ； insulin resistance ； biomarker ； S100A9

參考文獻

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