癌症患犬血清/組織YKL-40表現量與癌症病程的關聯性

Abstract

YKL-40又稱為CHI3L1 (chitinase-3-like-1) 蛋白，是一種分泌型的醣蛋白，具有幾丁質酶樣結構和幾丁質結合之親和力，但缺乏幾丁質酶活性。人類的YKL-40被認為是一種促炎反應及與腫瘤相關性的蛋白，在人類癌症醫學的研究中發現病患若有升高的血漿/血清YKL-40則會有較低的生存率或不良的預後，這表明YKL-40可能是一種潛在的腫瘤生物標誌，可當作診斷、風險評估和預後的指標。為了研究YKL-40在犬癌症的作用，我們先前的研究已經揭示犬重組YKL-40蛋白 (rcYKL-40) 具有與人類YKL-40相似的生物功能，隨後透過融合瘤技術開發了抗rcYKL-40的小鼠單株抗體，並將其轉變成單鏈變異區片段抗體 (scFv Abs)；有了先前研究的基礎，本研究的目的是在評估癌症犬的組織/血清中YKL-40的表現量，以探討其與癌症病程的相關性。首先，我們將純化的過程加以優化，以獲得高純度及高產量的rcYKL-40，之後以rcYKL-40和scFv Ab建立定量ELISA來偵測血清YKL-40的量；從國立臺灣大學附設動物醫院及地方動物醫院收集21隻健康犬及17隻癌症犬的血清做綜合調查，隨後也追蹤15隻淋巴癌患犬其治療前、治療中和治療後血清中YKL-40的量；另為了評估腫瘤組織中YKL-40的表現量，本實驗以商品化的抗人類YKL-40抗體建立免疫組織化學染色（IHC），評估由臺灣動藥國際股份有限公司所提供的38個犬黑素細胞瘤和23個犬肥大細胞腫瘤之石蠟包埋組織中YKL-40的表現量。研究結果發現癌症犬血清中YKL-40的量 (中位數=8.6450) 顯著高於健康犬血清中YKL-40的量 (中位數=1.8335)，同時血清中YKL-40量的變化與淋巴癌患犬的治療反應有密切關聯，其中治療後腫瘤消退時血清YKL-40量會顯著下降 (p=0.0013)，若後續腫瘤再轉變為惡性進展則血清YKL-40量會顯著上升 (p=0.0037)。在腫瘤組織中，YKL-40的表現量與黑素瘤的惡性程度有關，其中相較於良性黑素細胞瘤和皮膚型惡性黑色素瘤，粘膜型和趾間型的惡性黑素瘤會表現較高量的YKL-40 (p=0.0042)；而在肥大細胞腫瘤中，雖然YKL-40的表現在腫瘤分級間沒有顯著差異 (p=0.2921)，但我們觀察到YKL-40在腫瘤組織周邊的腫瘤細胞染色強度高於中心區域，此染色強度的區別顯示YKL-40可能在肥大細胞腫瘤局部的細胞侵潤過程發揮作用。根據我們研究的結果，犬YKL-40在血液和組織中的量或許可以作為評估癌症的惡性程度及預後良惡的指標。

YKL‐40, also known as CHI3L1 (chitinase-3-like-1), is a secretory glycoprotein and belongs to the mammalian chitinase‐like proteins with chitinase like structure and chitin-binding affinity, but lacking chitinase activity. Human YKL-40 was considered to be a proinflammatory and tumor-associated protein. Several studies indicated that elevated levels of plasma/serum YKL-40 were related to poor survival and poor prognosis in various human cancers, suggesting that YKL-40 might serve as a potential bio-marker of diagnosis, risk assessment, and prognosis factor for tumors. To investigate the role of YKL-40 in dogs, our previous studies have successfully expressed and purified recombinant canine YKL-40 (rcYKL-40) which revealed similar bio-functions with human YKL-40. Inspired by this, our lab has developed mouse monoclonal antibodies against rcYKL-40 through hybridoma technology and generated, subsequently, single-chain variable fragment antibodies (scFv Abs). Based on our previous results, the aims of this study are to investigate the correlation of tissue/serum YKL-40 levels and tumor progression in canine cancers. First, we optimized the process of purification and successfully gained high yield and high purity of rcYKL-40. To evaluate the YKL40 levels in serum, our rcYKL40 and scFv Abs were used to establish a quantitative ELISA. The serum samples of healthy dogs (n=21) and cancer dogs (n=17) were collected from National Taiwan University Veterinary Hospital and local animal hospitals. Furthermore, lymphoma dogs (n=15) were kept monitoring the serum YKL-40 levels by before, during and after treatment. In addition, a rabbit polyclonal anti-human YKL-40 antibody was used to establish immunohistochemical staining for evaluating YKL-40 levels in tumor tissues. Paraffin embedded tissue blocks of canine melanocytic neoplasms (n=38) and mast cell tumors (n=23) were provided by the Histopathology Service Section of Vetco Pharmaceuticals Inc. Our results indicated that serum YKL-40 levels in cancer dogs (median=8.6450) are significantly higher than that in healthy dogs (median=1.8335). The alternation of serum YKL-40 levels was significantly related to the treatment response in lymphoma dogs. The levels significantly decreased in the response of remission (p=0.0013), and the levels significantly elevated when the progression was noted (p=0.0037) afterwards. Canine YKL-40 expression is associated with tumor malignancy in melanocytic neoplasms, which the mucosal and digital malignant melanoma have significant YKL-40 overexpression than benign melanocytoma and cutaneous melanoma (p=0.0042). Although there was no significant difference of YKL-40 overexpression among different grade of mast cell tumors (p=0.2921), YKL-40 was observed that the tumors cell in the tumor margin had stronger staining intensity than those in the central area. This staining pattern indicated YKL-40 may play a role in local invasion of tumor cells in MCT. In accordance with our results, the YKL-40 levels in tissue and blood may be a potential indicator for assessing malignancy and prognosis in canine cancers.