Experimental Study On Correlation Between Expression Of P-p38,MMP-9 And MICA And Immune Escape Mechanism In Pituitary Adenomas

Objective:Pituitary adenoma is a common epithelial cell-derived intracranial tumor that accounts for 10-20%of all primary intracranial tumors,and its incidence rate is second only to glioma and meningioma.Moreover,according to epidemiological investigations,the morbidity of pituitary adenoma increases annually.The occurrence and development of tumors are complex processes that involve many aspects,such as immune status,cell differentiation and apoptosis.p38/mitogen-activated protein kinase(p38/MAPK)is a major pathway among the mitogen-activated protein kinase(MAPK)signal transduction pathways.Activation of the p38/MAPK pathway activates downstream nuclear transcription factors and regulates the expression of related genes,which affect cellular responses such as cell proliferation,differentiation,inflammation,and apoptosis.The MHC class I chain-related molecule A(MICA)is one of the Natural Killer Group 2D(NKG2D)ligands.soluble MHC class I chain-related molecule A(sMICA),one type of MICA,mediates tumor immune escape.In addition,matrix metalloproteinase-9(MMP-9),as an important member of the MMPs family,can promote the shedding of SMICA.The purpose of this study was to investigate the expression level of p38,phospho-p38(p-p38),MMP-9 and MICA in pituitary adenomas and the relationship between them.It provides a new histological basis for the study of the role of p38/MAPK signaling pathway in the immune escape of pituitary adenomas and points out a potential direction for the immunotherapy of pituitary adenomas.Methods:Immunohistochemistry(IHC)case slice source was the pathology department of Binzhou Medical College Hospital,from which 38 paraffin-embedded nonfunctional pituitary adenoma tissue sections(20 males and 18 females)and 21 paraffin-embedded prolactinoma pituitary adenoma tissue sections(6 males and 15 females)were randomly selected.A total of 39 patients were diagnosed with pituitary adenoma,including 21 nonfunctional pituitary adenomas(12 males and 9 females)and 18 prolactinoma pituitary adenomas(6 males and 12 females).All patients received trans-sphenoidal surgery at the Binzhou Medical University Affiliated Hospital between July 2015 and December 2017.These patients were diagnosed with pituitary adenoma by postoperative pathological confirmation.We also collected 20 normal brain tissues.In addition,peripheral blood serum was collected from each patient with pituitary adenoma before surgery.We also collected peripheral blood serum from 20 volunteers as controls.We used IHC to detect the expression of p38,phospho-p38,MMP-9 and MICA proteins in 59 paraffin-embedded pituitary adenoma and normal brain tissues.We used qRT-PCR to detect the expression of p38,MMP-9 and MICA mRNA in 39 pituitary adenoma and normal brain tissues;we also used Western blot to detect the expression of p38,phospho-p38,MMP-9 and MICA proteins in 39 pituitary adenoma and normal brain tissues.Detection of sMICA and MMP-9 protein levels in peripheral blood serum from pituitary adenoma patients and normal controls via ELISA.Finally,we analyzed relationships between phospho-p38,MMP-9,and MICA expression in pituitary adenoma tissues through Spearman analysis.Results:We found that p38 was positively expressed in the cytoplasm and in the nuclei,phospho-p38 was expressed in only the nuclei,MMP-9 was cytoplasmic,while MICA was expressed in the cytoplasm and nucleus.Moreover,the expression of p38,p-p38,MMP-9 and MICA proteins in non-functional pituitary adenomas and prolactin pituitary adenomas were significantly higher than those in normal brain tissues,and the difference was statistically significant.p38,MMP-9 and MICA mRNA expression levels in nonfunctional pituitary adenoma and prolactin pituitary adenoma tissues were significantly higher than those in normal brain tissues.There was a positive correlation between the expression of p-p38 protein and MMP-9,MICA protein in pituitary adenoma.In addition,the serum levels of MMP-9,sMICA proteins in nonfunctional pituitary adenoma and prolactin pituitary adenoma patients were significantly higher than those in normal controls.Conclusion:In pituitary adenomas,the activation of the p38/MAPK pathway may increase MICA expression and induce MMP-9 expression.MMP-9 is involved in the shedding of sMICA from MICA to promote tumor immune escape.Furthermore,p38/MAPK could potentially represent a novel target for inhibiting pituitary adenoma immune escape.