胰臟腺泡導管型態轉分化 (ADM) 是胰臟用以修復組織或應對環境刺激的可逆性機制。因為此機制使 PTF1α+ 外分泌腺泡細胞去分化並轉分化為具有始祖細胞特徵的 SOX9+ 導管細胞，異常的 ADM 被視為胰腺導管腺癌 (PDAC) 的初期特徵以及癌前病變。來自於胰臟組織的微環境刺激，不僅促使纖維細胞異常分化，更加速對胰臟外分泌腺泡細胞的轉分化過程，導致胰臟微環境之異質性，藉此反映在胰管腺癌患者的惡化速度以及對各種治療預後反應的差異。所以在此研究中我們探討一個在胰臟癌中經常受到DNA去甲基化機制所異常表達的胰臟基質基因- CD248在纖維細胞活化、胰管腺癌初期病變、與促發胰腺泡細胞導管化型態轉換的角色。在Cd248-/-; LSL-KrasG12D; Trp53fl/fl; Pdx1-Cre (Cd248-/--KPC) 轉基因小鼠之中，我們透過檢測分子特徵和形態，發現晚期ADM和胰腺上皮內細胞增生 (PanIN) 此兩種癌前病變均比KPC小鼠顯著下降，且更能維持外分泌腺泡團的細胞體系結構。Cd248-/--KPC 小鼠胰臟組織中含有較低SOX9+ 細胞族群，這也呈現出Cd248基因缺失對導管細胞群的增殖有抑制作用。此外，小鼠免疫組織染色檢測和細胞實驗均顯示Cd248野生型纖維細胞表現較高的α-SMA網絡，說明了Cd248能夠支持纖維細胞活化成肌纖維細胞。Cd248基因剔除型的小鼠胚胎纖維母細胞 (MEFs) 在癌細胞條件培養 (Conditioned medium) 所誘導下，對癌相關纖維母細胞亞型 (CAF subtype) 之特徵基因群也呈現出對比於Cd248野生型迥異的表達模式。而我的研究也在細胞實驗驗證了Cd248 野生型 MEFs 所分泌的旁泌因子對ADM型態轉分化的促進作用。整體而言，我的研究數據顯示CD248藉由調控纖維母細胞活化，加速對胰臟ADM的作用。

Acinar-to-Ductal Metaplasia (ADM) is a reversible cellular process in which pancreatic acinar cells respond to developmental cues or tissue injuries and transdifferentiate into progenitor-like SOX9+-ductal cells. Dysregulated fibroblasts in pancreatic microenvironment dynamically differentiate into cancer-associated fibroblasts (CAFs) and the heterogeneity may reflect diversified treatment responses and cancer progression in pancreatic ductal adenocarcinoma (PDAC). As high degrees of fibrosis present in PDAC tumor microenvironment, we focus on the role of a frequently demethylated stromal gene, CD248, and analyzed its activation in CAF and in the initiation of PDAC. We established transgenic mice with the Cd248-/-;LSL-KrasG12D;Trp53fl/fl;Pdx1-Cre (Cd248-/--KPC) genotype and analyzed its molecular pathological patterns to define the transdifferentiation between the ADM (early/late) and the pancreatic intraepithelial neoplasia (PanIN) precursor lesions. Multiplex immunofluorescence histochemistry staining of early-stage PDAC sections showed decreased frequency of both the late ADM and PanIN lesions and nicely maintained architectural acinar clusters in the Cd248-/--KPC mice as compared to those of KPC genotype. A lower level of SOX9+ population in the Cd248-/--KPC tissue consistently revealed the stimulatory effects of ectopic Cd248 expression in KPC tumors in accelerating the transdifferentiation of acinar cells into the ductal cells. Decreased α-SMA level in Cd248 deficient fibroblasts also indicated the myofibroblast promoting effects of Cd248 in both the tissue immunohistochemistry and in vitro assays. The wild type and the Cd248 knockout mouse embryo fibroblasts (MEFs) also demonstrated distinct stromal gene expression signatures of the myCAF and the iCAF subtypes. My work verified the ADM promoting capacity of paracrine factors secreted from Cd248 wild-type MEFs by using the Cd248 knockout approach in mice. In summary, our data supported that CD248 in CAFs is essential for cellular stimulation in the ADM of pancreatic acinar transdifferentiation.

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