Expression Of Aminopeptidase N And Its Clinical Significance In Breast Cancer

Objective: Aminopeptidase N(APN) is a zinc-dependent exopeptidase,and it was found to be the same protein with CD13in1989. APN/CD13hasfirst been known as a surface marker of myeloid hemopoietic cell for years,and subsequently been reported its high expression in tumor cells in theseyears, with functions including extracellular matrix degradation, angiogenesis,tumor invasion and metastasis. At the same time, some studies about APNinhibitor are performed, showing that APN inhibitor therapy could inhibittumor invasion and metastasis, induce tumor cells apoptosis, and prolongsurvival time. In this experiment we study the expression of APN and therelationship between APN expression and clinicopathological parameters inbreast cancer. Meanwhile, we investigate the correlation of APN and VEGF,MMP-2, MMP-9, to discuss the role of APN in the process of breastcarcinoma angiogenesis, invasion and metastasis; and, investigate theexpression of APN in lymph node metastatic carcinoma, to explore whetherthe expression is in accordance with that in the primary lesion of breast cancer.And its result provides a pre-exploratory of the application of APN relateddrugs in Chinese population.Methods:1.This study collected60specimens of surgically resected andparaffin-embedded human breast cancer tissues,26corresponding lymph nodemetastatic carcinoma, and20cases of adjacent normal breast tissues.Immunohistochemistry (SP means) was performed to measure the expressionsof APN, MMP-2and MMP-9in breast cancer, also the expressions of APN inadjacent normal breast tissues and lymph node metastatic carcinoma.2. This study also collected20fresh specimens of surgically resectedhuman breast cancer, and10cases of normal breast tissues. ReverseTranscription-Polymerase Chain Reaction (RT-PCR) was performed for the detection of APN mRNA expression.3. Statistical analysis: Pearson Chi-square (χ2) test, Wilcoxon rank sumtest and Spearman’s rank correlation analysis were performed. A probability(P)-value less than0.05was considered statistically significant. All statisticalanalyses were performed by SPSS13.0.Result:1. By immunohistochemistry, APN protein was mainly found inthe membrane of malignant cells, pale yellow or claybank. Besides, we alsoobserved APN expression in neovascular endothelium in breast cancer tissues,but no expression in normal endothelium. The positive rate of APN expressionin breast cancer tissues was higher than that in adjacent normal breast tissues,36.7%(22out of60) and0%(0out of20) respectively (χ2=10.115, P=0.001).2. In60cases of breast cancer tissues, tumor cell APN expression wasassociated with tumor pathological type, e.g., APN expression was more oftenfound in ductal invasive breast carcinoma than in other pathological types(χ2=4.429, P=0.035), with positive expression rates45.2%(19out of42) and16.7%(3out of18) respectively. However, there was no relationship betweenthe tumor cell APN expression and clinicopathological features, such asmenopausal state, clinical stage, tumor size, histological grade, and nodalstatus. Under the correlation analysis, there was no correlation between tumorcell APN expression and ER, PR, Her-2expression.(P＞0.05).3.MMP-2and MMP-9proteins expression were mainly observed in thecytoplasm of the malignant cells, brownish yellow granular, and the positiveexpression rates in breast cancer tissues were75.0%(45out of60) and76.7%(46out of60) respectively. The APN positive rates in MMP-2positive groupand in MMP-2negative group were33.3%（15out of45），46.7%（7out of15）respectively, showing no significant difference between the two groups(χ2=0.861，P=0.353). The APN positive rates in MMP-9positive group and inMMP-9negative group were39.1%（18out of46），28.6%（4out of14）respectively, showing no significant difference between the two groups(χ2=0.515，P=0.473). Under the correlation analysis, there was no correlationbetween the APN expression and MMP-2, MMP-9expression.(rs=-0.113,P =0.390vs. rs=0.076,P=0.566).4. In60cases of breast cancer tissues, the positive rate of VEGFexpression was78.3%(47out of60). The APN positive rates in VEGFpositive group and in VEGF negative group were44.7%（21out of47）、7.7%（1out of13）respectively, showing the APN expression was more oftenfound in VEGF positive group than in VEGF negative group (χ2=4.512,P=0.034). Under the correlation analysis, there was no correlation between theAPN expression and VEGF expression (rs=0.078,P=0.553).5. There was26cases breast cancers with lymphatic metastases. In thesecases, The positive rate of tumor cell APN expression in breast cancer tissueswas38.5%(10out of26), which was higher than that in lymphatic metastasestissues with the positive rate11.5%(3out of26)（χ2=5.026，P=0.025）. Therewas no correlation between breast cancer group and lymphatic metastasesgroup on the tumor cell expression of APN (rs=-0.277,P=0.171).6. Using RT-PCR technique to further detect the expression of APNmRNA, we got that the APN mRNA expression in breast cancer tissues washigher than that in normal breast tissues (Z=-2.376, P=0.018).Conclusion:1. The APN expression in breast cancer is higher thannormal breast tissues, and, high expression may indicates a poor prognosis.2. APN participates in the genesis and development process of breastcancer, and, there may be a synergistic effect between APN and VEGFexpression.3. The expression of APN in lymph node metastatic carcinoma isdifferent with the expression in the primary lesion of breast cancer.