胰臟癌誘發新生糖尿病之潛力致糖尿病因子之角色探討

Abstract

胰臟癌是目前全球癌症致死率排名中的第四位，且其五年內的存活率只有 5%。由於其症狀不明顯，導致有85% 的病人在被診斷時都已位於末期的階段。因此找尋能夠早期偵測出胰臟癌的方法是必要的。臨床上有高達40% 的病人在確診前兩年內會發生新生糖尿病，目前認為，新生糖尿病能提供早期診斷胰臟癌的潛力指標。而新生糖尿病是由於胰臟癌分泌的致糖尿病因子所導致。因此，在本篇研究中我們想找尋在新生糖尿病中的致糖尿病因子，作為區分新生糖尿病與第二型糖尿病的指標，達到早期偵測胰臟癌的目的。 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，並透過蛋白質體學及生物資訊分析結果，以及後續的驗證，鑑定出IL-32、TIMP-1、galectin-3及S100A9作為致糖尿病因子的候選蛋白。 在本篇中，我們收集臨床上四組病人的組織及血清檢體，分別為糖尿病、新生糖尿病、胰臟癌及健康人組別。我們發現galectin-3在新生糖尿病病人的組織中表現量會上升，S100A9在胰臟癌及新生糖尿病病人組織中會同時表現在癌細胞及癌症基質細胞中，而IL-32及TIMP-1則是在胰臟癌及新生糖尿病病人組織中表現量無顯著差異。另外，galectin-3及S100A9在有糖尿病的病人血清中含量都會上升，而IL-32在四個族群中無顯著差異。上述實驗顯示galectin-3及S100A9可能為糖尿病的指標。因此我們選定galectin-3及S100A9，繼續探討其對於細胞代謝功能上的影響。在先前實驗室的實驗結果中，已證明galectin-3會抑制肌肉細胞攝 取葡萄糖能力及降低胰臟β細胞胰島素的釋放量。 在本篇中，我們發現S100A9也能夠有效抑制肌肉細胞攝取葡萄糖的能力，並且降低β細胞胰島素的釋放量，說明S100A9能夠造成細胞胰島素阻抗的發生。接著我們去探討S100A9造成胰島素阻抗的機制，由結果顯示，S100A9會透過抑制IRS-1的活性，降低AKT的磷酸化，造成細胞胰島素訊息傳遞路徑受到阻擾。上述的實驗中，我們確認galectin-3及S100A9為胰臟癌中的致糖尿病因子，在後續的實驗中，我們將深入探討其在胰臟癌中導致糖尿病的機制。並且若能再搭配其他胰臟癌的生物標記，組合成複合型生物標記，便能提供早期偵測胰臟癌的指標。

Pancreatic cancer (PC) is the fourth leading cause of cancer-related deaths in the world with an overall-5-year survival rate less than 5%. Due to the lack of effective detection methods, 85% of patients are diagnosed at advanced stage. Therefore, the discovery of biomarkers for early detection is necessary. There are approximately 40% of PC patients followed with PC-associated new-onset diabetes (PCDM), occurring 2 years before PC is diagnosed. These provide a potential clue to detect PC in early stage. PCDM is mediated by some unknown tumor-secreted diabetogenic factors. Identifying the diabetogenic factors in PCDM may help us understand its pathogenesis and discover novel biomarkers to distinguish PCDM from Type 2 diabetes (T2DM). In our previous studies, we identified IL-32, TIMP-1, galectin-3 and S100A9 as candidates in condition media (CM) of two pancreatic cancer cell lines (MiaPaCa-2 and PANC-1), and further investigated their feature in PC. First, we collected different groups of patients’ samples, including diabetes (DM), PCDM, PC and normal control. We found that galectin-3 expressed higher level in cancer cells of PCDM, S100A9 expressed both in cancer cells and tumor stroma cells of PCDM and PC, while IL-32 and TIMP-1 showed no differences between PCDM and PC. Additionally, galectin-3 and S100A9 expressed higher level in serum of PCDM, while IL-32 showed no difference between each groups. Through clinical evidences, we selected galectin-3 and S100A9 as candidates of diabetogenic factors, and further detected their effects on cell functions. In our study, we found that S100A9 impaired glucose uptake ability of C2C12 cells and decreased the insulin secretion level in ß cells. Moreover, we investigated the mechanism of S100A9 leading to inferior glucose uptake of C2C12 cells. We verified that S100A9 inhibits insulin signaling pathway through reduced IRS-1 activity and AKT phosphorylation, resulted in insulin resistance in C2C12 cells. By characterizing these proteins, we discovered galectin-3 and S100A9 as potential biomarkers of PCDM. In the future, in order to distinguish PCDM from T2DM, it is necessary to combine other potential biomarkers of PC into a multiple panel.