Expression Of ILT3 In NSCLC And The Clinical Significance

[Background and Objective]Lung cancer is a frequent malignancy with poor prognosis nowadays,of which 80% are non small cell lung cancer(NSCLC).At present,therapuetic strategy for NSCLC is still multimodality treatment.While large progess has been made in surgery,chemicotherapy and radiotherapy,life span of NSCLC patients has not improved much because of high metastasis rate and low local control rate. With the development of molecular biology and immunology, biotherapy has become the fourth main method along with the three above.Cell immunity mediated by T cell is the most important mechanism in tumor-associated immunoresponse.However,tumor cells can still escape from organic immunosurveillence and attaction of T cells through kinds of ways. Among with them, immunoinhibitory factors are considered can inhibit the activation of tumor-specific T cell,induce proliferation and differentiation of Treg,and impair anti-tumor immunoresponse of organism. ILT3 is just one of them.Rescent years,large amount of researches has focused on immunoinhibitory function of ILT3 on T cell immune which has been demonstrated in transplantation tolerance, hypersensitivity and autoimmune diseases.However, its inhibitory activity in malignancies is still seldom seen.In the test,we will investigate expression of ILT3 in NSCLC and the correlation between ILT3 and genesis of NSCLC and provide reference for further approching the mechanism of ILT3 on immune escape of tumor.[Purpose]Using four NSCLC cell lines (A549, H1975, H460, A427) and 57 specimens from NSCLC,we will explore the expression of ILT3 from both mRNA and protein level and the associativity between ILT3 expressed on tumor tissues and several clinical parameters such as sex,age,size of tumor,pathology type, differentiation degree,metastasis of lymph nodes, TILs.[Methods](1) Detect ILT3 expression in NSCLC cell lines(A549, H1975, H460, A427)from mRNA level by RT-PCR.(2) Detect ILT3 expression on NSCLC cell lines (A549, H1975, H460, A427)from protein level by flow cytometry and immunocytochemistry.(3) Detect ILT3 expression of 57 NSCLC specimens by immunohistochemistry and further analyze its correlation with sex,age,size of tumor,pathology type, differentiation degree and metastasis of lymph node by SPSS software.P<0.05 is the standard for dominant difference.[Results](1) All the cell lines express ILT3 mRNA.The forward and retroward primers are designed on exon 3 and 4 respectively and the size of PCR product is 393bp.(2) FCM shows ILT3 expression in all the four cell lines from protein level,the positive rate for them are 31.31%,22.32%,47.07% and 41.59% respectively.While the positive rate for their negtive controls are 0.89%,0.57%,0.94% and 0.39% respectively,which is corresponding with RNA semi-quantitation results.Immunocytochemistry verifies existance of ILT3 in both cytoplasmas and cell membranes of these cell lines.(3) Expression of ILT3 in tumor tissues①20 among 57 specimens are ILT3 positive(35.1%) both in cytoplasmas and cell membranes.Tumor infiltrated lymphocytes(TILs) in strauma also show ILT3 positive granules,while normal lung tissue around and specimens from 22 benign diseases show no expression of ILT3.②Expression of ILT3 in tumor tissues is uncorrelated with sex,age,size of tumor, pathology type, differentiation degree,metastasis of lymph nodes.③Relation between ILT3 and TILs:CD45+ T cells in ILT3 positive specimens are 23.65±6.218, while 51.54±11.864 in ILT3 negtive specimens, P<0.05,tiping dominant difference and significance. Meanwhile,tumor cells around TILs from ILT3 positive specimens show neither sign of necrosis nor impairment,suggesting immunotolerance feature of TILs.[Conclusion] ILT3 is expressed from both mRNA and protein level in cell lines and tissues of NSCLC,which may represent one of the immune escape mechanisms for NSCLC.Clearing or blocking ILT3 proteins in tumor cells may be a nobal way responding for tumor immunotheraphy.