Expression Of HMGB1/RAGE Protein In Renal Carcinoma And Its Clinical Significance

Background and ObjectiveRenal carcinoma is the most common malignant renal tumor,and it has variable biological characteristics and is prone to metastasis and relapse.In recent years,the incidence of renal carcinoma shows a rising trend over each year.Because of highly expressed drug-resistant genes in renal carcinoma cells,routine chemotherapy has no significant effect in renal carcinoma.Therefore,developing a deeper understanding of the mechanisms underlying renal carcinoma pathogenesis and progression along with specifically targeted drugs has important clinical significance in the improvement of prognoses in renal carcinoma patients.High mobility group box 1(HMGB1)was one of high mobility group protein.In most cells,HMGB1 is located in the nucleus,where it acts as a DNA chaperone to help maintain nuclear homeostasis.HMGB1 was later discovered to express on cell surface membranes,cytosol,and mitochondria,and release into the extracellular space.HMGB1 has many biological functions inside as well as outside the cell,and plays a significant role in many diseases,especially inflammatory diseases and cancer.In addition to its role in the nucleus,HMGB1 also functions as a damage-associated molecular pattern(DAMP)when passively released from dead,dying,or injured cells or when actively secreted from immune cells or cancer cells in response to exogenous and endogenous stimuli such as endotoxin,CpG DNA,double-stranded RNA(dsRNA),tumor necrosis factor(TNF)-a,interleukin(IL)-1,interferons(IFN)-y,hydrogen peroxide,adenosine triphosphate(ATP),and hypoxia.In addition,macrophage engulfment of apoptotic cells may induce significant active HMGB1 release,suggesting a direct interplay between dying cells and immune cells,which also induces HMGB1 release.Once released,extracellular HMGB1 binds to several cell surface receptors to activate the downstream signaling pathway(e.g.,NF-?B,IFN regulatory factor-3(IRF3),and phosphatidylinositol 3-kinase[PI3K])to produce a functional response,such as activation of innate immune cells,induction of proinflammatory cytokines and type I IFNs,stimulation of cell adhesion and migration,inhibition of phagocytosis,promotion of cell proliferation and angiogenesis,and induction of autophagy.These receptors mainly include the receptor for advanced glycation end products(RAGE),Toll-like receptors(TLRs,such as TLR2,TLR4,and TLR9)and others.RAGE was the first receptor demonstrated to bind HMGB1.The loci(AGER)encoding RAGE is located on chromosome 6 near MHC class III in humans and mice.RAGE is a type I transmembrane protein composed of three extracellular immunoglobulin-like domains(V,C1,and C2)a single trans-membrane domain,and a short cytoplasmic tail.Interactions between RAGE and its ligands are mapped to the V/Cl domain,with the amino-terminal V domain providing the major contribution.RAGE is constitutively expressed at high levels in the lung.Expression is localized to alveolar type II cells and on the basolat-eral membranes of the alveolar type I epithe-lial cells.The physiological relevance of the high expression in these cells is unknown.Elsewhere,there is widespread but relatively low expression of RAGE on vascular endothelial cells,neutrophils,monocytes/macrophages,lymphocytes,DCs,cardiomyocytes,and neurons.Recent data indicated that HMGB1/RAGE axis was associated with tumor formation,progression,and metastasis in a wide variety of tumors.Elevated expression of HMGB1 occurs in several solid tumors,including melanoma,colon cancer,prostate cancer,pancreatic cancer,and breast cancer.The inhibition of HMGB 1/RAGE interaction suppresses tumor growth and metastasis.Lin et al study found that HMGB1 and RAGE correspond to the tumor growth and clinical stage of the clear cell renal cell carcinoma patients.However,M.Srinivasan study showed that HMGB1 and RAGE gene expression between cancer and normal samples did not show any significant difference suggesting that further studies are required to validate the expression of HMGB1 and RAGE in the clear cell renal cell carcinoma.Previous studies have found that high mobility group protein B1(HMGB1)and its receptor,receptor for advanced glycation end-product(RAGE),play important roles in the development,progression and metastasis of multiple tumors.The clinical renal cell carcinoma patients as the research object in this study.The expression of HMGB1 and RAGE proteins in renal cancer tissue and paratumoral tissue was examined using immunohistochemical methods.To explore the correlation between the two in the renal cell carcinoma.The relationship between the expression of HMGB1/RAGE protein and gender,age,tumor size,differentiation degree,clinical stage and lymph node metastasis in renal cell carcinoma patients were analyzed to reveal the correlation and clinical significance of such expression in the development and progression of renal cell carcinoma.To investigate the relationship between the expression of HMGB1/RAGE protein and the prognosis of patients,which provide a new direction for the treatment and to provide the basis for the new target of renal cell carcinoma.Methods1.A total of 80 renal carcinoma patients who were surgically treated in our hospital from February 2004 to December 2012 were included in this study.Diagnoses were confirmed with postoperative pathological examination.All of the patients had complete clinical pathological data and signed informed consent before surgery.Patients with trauma or systemic disorders were excluded,and follow-up investigations on the participants were performed for 3-60 months.2.Immunohistochemistry was performed with surgically resected tumor tissues and adjacent normal tissues.The expression of HMGB1/RAGE proteins' in renal cancer tissue was examined using immunohistochemical methods.Normal paratumoral tissues were collected as a control.3.A x2 test was employed for the count data,and the Kaplan-Meier method was used for the survival analysis.The correlation between the expression of RAGE and HMGB1 in renal carcinoma tissues was analyzed using Spearman's rank correlation coefficient.Results1.HMGB1 mainly located in the cytoplasm or nuclei,and RAGE protein mainly located in the cell membrane.The statistical analysis indicated an HMGB1-positive rate of 88.75%in renal cancer tissues and 31.25%in the paratumoral normal tissues,and the difference was statistically significant(P<0.05)..The positive expression rate of RAGE was 90%in renal cancer tissue,which was significantly higher than that in the paratumoral normal tissue(33.75%)(P<0.05).2.The positive expression rate of HMGB1 was 93.2%in male and 83.4%in female.The positive expression rate of HMGB1 was 80%in tumor diameter<4 cm group,and 92.7%in tumor diameter>4 cm group.The positive expression rate of HMGB1 was 89.7%in the age<65 years group,and 86.4%in the age>65 years group.The results showed that the expression level of HMGB1 was not correlated with tumor size and gender and age of the patients with renal carcinoma(P>0.05).The positive expression rate of HMGB1 was 98.0%in medium/low differentiation,and 74.2%in high differentiation of renal carcinoma.The positive expression rate of HMGB1 was 75.0%in linical stage ?/?,and 96.2%in linical stage?/?.The positive expression rate of HMGB1 was 97.6%in lymph node metastasis group,and 78.6%in non lymph node metastasis group.The results showed that the expression level of HMGB1 displayed a significant correlation with clinical stage,differentiation degree and lymph node metastasis in the patient(P<0.05).3.The positive expression rate of RAGE was 95.5%in male and 83.4%in female.The positive expression rate of RAGE was 84%in tumor diameter<4 cm group,and 92.7%in tumor diameter>4 cm group.The positive expression rate of RAGE was 89.7%in the age<65 years group,and 86.4%in the age>65 years group.The results showed that the expression level of RAGE was not correlated with tumor size and gender and age of the patients with renal carcinoma(P>0.05).The positive expression rate of RAGE was 98.0%in medium/low differentiation,and 74.2%in high differentiation of renal carcinoma.The positive expression rate of RAGE was 75.0%in linical stage ?/?,and 96.2%in linical stage ?/?.The positive expression rate of RAGE was 97.6%in lymph node metastasis group,and 78.6%in non lymph node metastasis group.The results showed that the expression level of RAGE displayed a significant correlation with clinical stage,differentiation degree and lymph node metastasis in the patient(P<0.05).That indicating a consistent relationship between the expression of HMGB1 and RAGE and clinical pathological characteristics of the renal carcinoma patients.4.The expression of HMGB1 protein in renal cancer tissues exhibited a significant positive correlation with the expression of RAGE protein in these tissues(P<0.05).The expression of HMGB1 and RAGE proteins exhibited a negative correlation with the prognosis of patients,and the five-year survival rate of patients with positive expression was significantly lower than that of patients with negative expression(P<0.05).Conclusion1.HMGB1 mainly located in the cytoplasm or nuclei,and RAGE mainly located in the cell membrane in renal cell cancer tissues.2.HMGB1 and RAGE exhibited significantly elevated expression in renal cancer tissues.In addition,HMGB1 expression exhibited a significant positive correlation with RAGE protein expression.3.The expression level of HMGB1 and RAGE was not correlated with tumor size and gender and age of the patients with renal carcinoma,although it displayed a significant correlation with clinical stage,differentiation degree and lymph node metastasis in the patient.The 5-year survival rate of the patients with positive HMGB1 and RAGE protein expression was significantly lower than that of the patients with negative HMGB1 and RAGE protein expression that was closely related to the clinical prognosis of patients.Thus,the expression levels might be a useful parameter as an indication of tumor invasion,metastasis,prognosis and clinical prognosis biological behavior of human renal carcinoma.The HMGB1 and RAGE may become a new target in the gene treatment of renal carcinoma.