基質纖維母細胞分泌趨化激素CXCL12在人類基底細胞癌侵襲與血管新生中所扮演的角色

The role of stromal fibroblasts-produced chemokine CXCL12 in human basal cell carcinoma invasion and angiogenesis

朱家瑜(Chia-Yu Chu)

指導教授 ： 郭明良

國立臺灣大學/醫學院/毒理學研究所/博士(2007年)

https://doi.org/10.6342/NTU.2007.00091

摘要

基底細胞癌是人類最常見的皮膚癌，其特徵是局部的侵襲性而很少轉移至遠端器官，然而基底細胞癌還是可以往下侵犯深部組織、造成局部復發或轉移，目前對於基底細胞癌侵襲深部組織的機轉仍然未明。由於皮膚極易受到外界的刺激如紫外線或其他化學物質刺激而發炎，因此可以做為研究發炎對癌症細胞生物特性影響之理想模型。在本研究中，我們企圖探討趨化激素CXCL12引發基底細胞癌侵襲與血管新生的機轉。
趨化激素為一群小分子量(8-14 kDa)的多肽類分子，可與細胞膜上的G蛋白關聯性受體結合，這些受體即是所謂趨化激素受體。近年來研究發現，趨化激素與其受體在癌細胞的增生、血管新生與轉移上扮演重要的角色。此外，發炎時也會導致趨化激素與其受體的表現增加，近二年來陸續在其他癌細胞（包括肺癌、乳癌、黑色素細胞癌、神經膠母細胞瘤）發現趨化激素CXCL12與其受體CXCR4可能在腫瘤形成、細胞增生與血管新生扮演了重要的角色。我們發現人類基底細胞癌組織與基底細胞癌細胞株具有顯著的CXCR4表現，人類基底細胞癌組織的CXCR4表現比率與其侵襲性組織亞型有高度相關，而且在回顧本院過去12年來所有基底細胞癌案例 (390例) 中局部復發的19例腫瘤組織後發現，其中CXCR4高度表現者占17例(89.5%)，體外實驗也發現外加CXCL12 (SDF-1α)可以促進人類基底細胞癌細胞的侵襲度。同時MMP-13的mRNA與蛋白表現量以及活性也在外加CXCL12後顯著上升。我們的研究顯示：CXCL12轉錄調控MMP-13表現增加的機轉，係透過活化ERK1/2與AP-1中的c-Jun等訊息傳遞路徑而達成。動物實驗也顯示CXCR4高表現的細胞株具有較大的腫瘤與侵襲性組織亞型，而CXCR4與MMP-13也會同時表現。
此外我們也運用免疫組織染色法分析71例人類基底細胞癌的手術檢體，發現人類基底細胞癌組織的CXCR4表現強度與微血管密度(MVD)具有顯著相關(P < 0.0001)。以CXCL12處理後的基底細胞癌細胞培養液也可以顯著地增加人類臍帶靜脈內皮細胞(HUVEC)的血管形成，此一作用可以藉由預處理CXCR4抑制劑或中和抗體而加以抑制。我們使用DNA微陣列分析來探討CXCL12所造成的血管新生因子基因表現變化，發現IFI27, IL-6, BMP-6, SOCS2與 COX-2等基因都有超過3倍以上之表現增加。CXCL12刺激後最早出現顯著上升的基因是介白素-6(IL-6)與骨骼形成蛋白-6(BMP-6)。我們進一步確認，CXCL12促進IL-6的 mRNA表現與分泌蛋白增加具有劑量與時間效應關係。使用CXCR4高表現的基底細胞癌細胞株與對照組細胞株進行裸鼠之皮下注射，也顯示前者會產生較大的腫瘤與較高的微血管密度(MVD)。
我們也建立IL-6高度表現之人類基底細胞癌細胞株，並探討IL-6在基底細胞癌血管新生的角色。IL-6高表現之人類基底細胞癌細胞株具有較高之血管形成活性，也具有較高的bFGF mRNA表現，且分泌較多的鹼性纖維母細胞生長因子。外加IL-6處理人類基底細胞癌細胞株也會導致bFGF mRNA與蛋白的顯著上升，並具有時間效應關係，以中和抗體中和bFGF的功能可以有效抑制人類基底細胞癌細胞株培養液促進HUVEC血管形成的活性，同時我們也發現 COX-2的特異性 siRNA亦可以有效抑制HUVEC血管形成。因此，bFGF與COX-2二者皆參與了IL-6所調控的基底細胞癌血管新生。使用AG490 (JAK抑制劑)與LY294002 (PI3-激酶抑制劑)均可抑制IL-6所誘發的bFGF mRNA表現與蛋白分泌增加；轉殖不具酵素活性之STAT3或Akt突變質體也具有同樣的抑制功能。因此，我們的研究證實：在IL-6所引發的人類基底細胞癌細胞株血管新生作用中，bFGF與COX-2都是IL-6的下游作用因子，而且IL-6調控bFGF表現增加的機制，乃是透過JAK/STAT3與PI3-Kinase/Akt二訊息傳導路徑之活化。
總結來說，本論文提供了趨化激素CXCL12與其受體CXCR4作用可以增加人類基底細胞癌之惡性度的證據。確認CXCL12-CXCR4交互作用、MMP-13、IL-6在人類基底細胞癌侵襲性、腫瘤形成與血管新生扮演了重要的角色，可以使我們對於人類基底細胞癌的惡性度機轉有更多的認識，同時也可以提供針對侵襲性基底細胞癌的未來治療趨勢。

關鍵字

血管新生 ； 基底細胞癌 ； 趨化激素 ； 纖維母細胞 ； 侵襲

並列摘要

Basal cell carcinoma (BCC) is one of the most common skin neoplasms in humans and is usually characterized by local aggressiveness with little metastatic potential, though deep invasion, recurrence, and regional and distant metastases may occur. Since the skin could be inflamed after exposure to a variety of stimulants including ultraviolet lights and some chemical agents, it might be a good model for studying the effects of inflammation on cancer cell biology. In this study, we studied the mechanisms of CXCL12-induced BCC invasion and angiogenesis.
Chemokines are structurally related, small (8-14 kDa) polypeptide signaling molecules that bind to and activate a family of seven transmembrane G protein-coupled receptors, the chemokine receptors. Recently, it was found that chemokines and their receptors were involved in proliferation, angiogenesis and metastasis of various types of cancer cells. Among these chemokines and chemokine receptors, CXCL12-CXCR4 interaction has been found to play an important role in tumorigenicity, proliferation, and angiogenesis in many cancer cell lines such as lung cancer, breast cancer, melanomas and glioblastoma. We found that human BCC tissues and a BCC cell line had significant expression of CXCR4, which was higher in invasive than non-invasive BCC types. Further, of 19 recurrent tumors among 390 BCCs diagnosed during the past 12 years, 17/19 (89.5%) had high CXCR4 expression. We found that the CXCR4 ligand, CXCL12 (SDF-1α), directed BCC invasion and that this was mediated by time-dependent up-regulation of mRNA expression and gelatinase activity of matrix metalloproteinase-13 (MMP-13). The transcriptional regulation of MMP-13 by SDF-1α was mediated by phosphorylation of extracellular signal-related kinase 1/2 (ERK1/2) and activation of the AP-1 component c-Jun. Finally, CXCR4-transfected BCC cells injected into nude mice induced aggressive BCCs that co-expressed CXCR4 and MMP-13.
In addition, we also found a significant correlation of CXCR4 expression in BCC tumor cells and microvessel density (MVD) in 71 BCC biopsy specimens by immunohistochemical staining (P < 0.0001). In vitro study of angiogenesis by using capillary tube formation assay of human umbilical vein endothelial cells (HUVEC) also revealed the condition medium (CM) obtained from BCC cell stimulated with CXCL12 had greater angiogenesis activity, which can be inhibited by pre-treatment with a CXCR4 inhibitor or neutralizing antibody. By using a DNA oligonucleotide microarray designed for angiogenesis-associated genes, we found CXCL12 significantly up-regulated (more than 3-fold) several angiogenesis-associatted genes including IFI27, IL-6, BMP-6, SOCS2, and PTGS2 (COX-2) in human BCC cells. Among them, interleukin-6 (IL-6) and bone morphogenetic protein-6 (BMP-6) were the earliest significantly up-regulated factors in BCC cells stimulated with CXCL12. CXCL12 enhanced IL-6 mRNA and protein secretion in human BCC cells in a dose- and time- dependent manner. CXCR4-transfected BCC cells injected into nude mice induced greater tumorigenicity and MVD compared to the BCC/pcDNA3 cells.
Finally, we elucidated the role of IL-6 in human BCC angiogenesis by establishing an IL-6 over-expressing BCC cell line. We found 10-fold concentrated CM from IL-6 over-expressing BCC cells exhibited higher angiogenic activities in chorioallantoic membrane (CAM) and Matrigel plug assays, when compared to CM from vector control or parental BCC cells. The level of bFGF mRNA and secreted bFGF increased in IL-6 over-expressing BCC cells as shown by RT-PCR and ELISA respectively. Concordantly, recombinant IL-6 treatment caused the elevation of bFGF mRNA and protein levels in parental BCC cells in a time-dependent manner. Neutralizing bFGF function by anti-bFGF antibody significantly inhibited CM-induced HUVEC tube formation and Matrigel plug formation. Meanwhile, cyclooxygenase 2 (COX-2)-specific siRNA markedly abolish HUVEC tube formation. These data indicated both bFGF and COX-2 play an essential role for IL-6 induced angiogenesis in BCC cell line. Treatment with AG490 (JAK inhibitor) and LY294002 (PI3-Kinase inhibitor) inhibited IL-6 mediated up-regulation of bFGF mRNA and protein secretion. Transfection with dominant negative mutants of STAT3 and Akt effectively abolished IL-6 mediated expression of bFGF mRNA and protein. Our data suggest that under in vitro experimental condition, bFGF and COX-2 are downstream effectors of IL-6 induced angiogenic activity in BCC cells. The IL-6 mediated bFGF up-regulation is through activation of JAK/STAT3 and PI3-Kinase/Akt pathways.
In summary, these studies provide evidences for the involvement of CXCL12-CXCR4 interaction, MMP-13, IL-6, and other angiogenesis factors in the aggressiveness of human BCC. The identification of CXCL12-CXCR4 as an important factor in BCC invasiveness, tumorigenicity and angiogenesis may contribute insight into mechanisms involved in the aggressive potential of human BCC and may improve therapy for invasive BCCs.

並列關鍵字

angiogenesis ； basal cell carcinoma ； chemokine ； fibroblasts ； invasion

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