以冷光化學免疫試驗偵測各種腫瘤患犬之α型胎兒蛋白受體血清量

Abstract

α型胎兒蛋白簡稱AFP，是一哺乳動物胎兒時期主要的血清蛋白，此蛋白是一種運輸蛋白並會參與胎兒組織的生長調節，一般認為此蛋白會經由受體媒介的胞飲作用進入細胞進而參與腫瘤細胞和胚胎細胞的生長發育。α型胎兒蛋白受體簡稱AFPR，最早於人類的MCF-7乳癌細胞株發現，並陸續在人類單核球細胞株以及其他腫瘤的細胞膜上發現此特異性受體的存在，因此AFPR逐漸被認為是一種泛腫瘤表現的膜蛋白受體。雖然AFPR已被部分分離及純化，但其特性及生理機制仍未完全明朗。然而隨著抗AFPR的單株抗體發展，已有文獻指出人類AFPR的血清量具有偵測人類早期乳腺癌的能力。另外，合併使用AFPR及CA125亦能提高早期診斷人類卵巢癌的敏感度及特異度。目前在犬AFPR血清量的相關研究甚少。因此，本實驗的目的為利用冷光化學免疫試驗偵測並定量在健康犬及各種腫瘤病犬的AFPR血清量，以及比較腫瘤患犬在治療前後血清AFPR量的變化。結果顯示在26隻健康犬AFPR血清量為4953±1220 (Mean ± SD, median 5284) units；24隻良性腫瘤病犬的AFPR血清量為4770±1256 (Mean ± SD, median 4601) units；94隻惡性腫瘤病犬的AFPR血清量為4742±1497 (Mean ± SD, median 4669) units，上述結果顯示AFPR 血清量於健康犬及腫瘤患犬間並無顯著差異。上皮來源腫瘤、間質來源腫瘤、血淋巴來源腫瘤及性腺來源腫瘤的腫瘤患犬AFPR 血清量亦未見明顯差異。此外，比較各種類別間良惡性腫瘤的AFPR血清量，僅有惡性上皮腫瘤患犬有較高的趨勢。在比較治療前後的AFPR血清量變化上發現，化療前後AFPR血清量的變化與疾病進展有明顯相關，若AFPR血清量上升則代表惡化，下降則代表好轉。然而，手術切除局部病灶的患犬並未見到此AFPR血清量的變化現象。總結，犬 AFPR血清量在區別良惡性腫瘤的效力並不顯著。然而犬AFPR血清量應能使用在全身性腫瘤病犬化療後的復發追蹤，以及用於評估惡性腫瘤的預後。然而此結果仍待更進一步研究。

Alpha-fetoprotein (AFP), assigned as an onco-fetal protein in mammalian, were single-chain glycoproteins with molecular masses ranging from 69 kDa and 3%–5% carbohydrate (glycan) content. The entry of AFP into malignant cells may occurred by a process of receptor-mediated endocytosis. The specific binding of alpha-fetoprotein was first demonstrated on human MCF-7 breast cancer cell line, and then subsequently on the membrane of various neoplastic cells. Followed, the putative alpha-fetoprotein receptor (AFPR) was partially purified and characterized from human monocytes. Several studies had been demonstrated that the presence of AFPR on tumor cell membranes. By the developing of monoclonal antibody against the AFP receptor, AFPR was considered to provide with the better sensitivity and specificity in detection for some human early-stage breast cancers than conventional serum marker. Combination of AFPR and CA-125 also elevated the efficacy on ovarian tumor detection. However, researches about AFPR in canine sera were rare. The aim of our study was to explore the difference of serum AFPR level by the quantitative chemiluminescence immunoassay in dogs with healthy condition and tumor-bearing dogs and to compare the serum AFPR values of untreated dogs with treated dogs. Results showed that there were neither a significant difference in serum AFPR level between healthy group and tumor-bearing group nor obvious differences among epithelial tumor group, mesenchymal tumor group, hematopoietic/ lymphoreticular tumor group, and gonadal tumors group. Except for the malignant epithelial tumors having higher tendency than benign epithelial tumors (p=0.098), there is no statistical difference between different types of neoplasm. Intriguingly, serum AFPR level in 14 of 15 dogs after chemotherapy showed highly corresponding along with course of disease, increased level for progression and decreased level for remission, respectively. However, there was no significant difference between serum AFPR level in those dogs with localized tumor before and after surgery. In conclusion, although serum AFPR level have unremarkable efficacy in screening and detecting canine tumors, serum AFPR level may be able to use on monitoring the dogs with the relapse of systemic malignant tumors after chemotherapy. Furthermore, AFPR level may have potential use to evaluate the prognosis of the dogs with advanced tumors but it need further investigation.