| Background:Colon cancer is caused by malignant transformation of the colonic mucosa epithelium under the action of various carcinogens,and gradually develops into visible lesion.Its predominant site is the junction of the rectum and the sigmoid colon.In China,the incidence of colon cancer among all cancers ranks fifth among men,fourth among women,and mortality ranks fifth among both men and women.Moreover,both morbidity and mortality are still increasing[1].The five-year survival of colon cancer is highly dependent on the stage of the disease,the 5-year survival rate of early colon cancer may be as high as 90%,unfortunately,by the time of diagnosis,more than 60%of the cases had progressed to advanced stages with 5-year survival rates of approximately 8-9%[2].Adenoma is the main precursor lesion of intestinal cancer and often develops to colorectal cancer,but the process is slow and there are no obvious symptoms locally,which is the main factor attributing to advanced stage,poor prognosis and high mortality[3].Therefore,early diagnosis of cancer is crucial.TNM staging is currently the main tool for evaluating the prognosis of malignant tumors in clinical work.The higher the staging,the higher the tumor progression and the worse the prognosis.However,there are some differences in prognosis for patients of the same stage,which mainly depends on tumor heterogeneity[4].More and more evidence indicates that colon cancer is related to activation of oncogenic signaling pathways and inactivation of tumor suppressor signals,mainly caused by genetic mutations and epigenetic changes,the latter including DNA methylation,histones acetylated and non-coding RNA[5].The high mobility group A2（HMGA2）protein is a non?histone architectural transcription factor that modulates the transcription of several genes and alters the chromatin structure[6].It may up-regulate cancer stem cell markers（CD44,ALDH1,Sox2,Oct4）and epithelial-mesenchymal transition（EMT）related factors（Snail,β-catenin）expression,thereby promoting tumor growth and cell migration[7].The pre-B cell leukemia（PBX）family is a group of homeodomain-containing transcription factors and homologues of the Drosophila extradenticle gene.Humans have 4 PBX homologues,PBX1–4,all of which encode a protein that contains a homeodomain DNA-binding region and a protein interaction domain[8].PBX3 differs from other PBX proteins,as it can form a stable interaction with DNA as a monomer or homodimer,through a consensus binding sequence of TGATTGATTTGAT[9].PBX3 can induce EMT by up-regulating N-cadherin and vimentin,and down-regulating the expression of E-cadherin,up-regulate the level of phosphorylated AKT and ERK,and associate with various malignant tumors initiation and progression[10-12].PBX3 can interfere with EMT induced by transforming growth factor-β（TGF-β）;by up-regulating the expression of LIN28 to inhibits let-7b,thereby promoting the expression of HMGA2[13].However,the current understanding on the expression and mechanism of HMGA2 and PBX3protein in colon cancer,the relationship with the prognosis and the correlation between the two genes in colon cancer are still very limited.Objectives:To detect the protein expression of HMGA2 and PBX3 in colon cancer tissues and adjacent tissues;study the correlation of the expression of HMGA2 protein and PBX3 protein in colon cancer;analyze the relationship between the protein expressions of HMGA2 and PBX3 and different pathological parameters and prognosis of colon cancer,with a aim to provide new markers for the early diagnosis and prognosis evaluation of colon cancer patients and new intervention targets for individualized treatment of colon cancer patients.Materials and Methods:Sixty-five paraffin-embedded specimens of colon and paired adjacent tissues（≥5cm from the cancerous tissue）were collected from patients undergoing radical resection at the Affiliated Tumor Hospital of Zhengzhou University from May 2012to May 2014.The experimental group was colon cancer tissues,the control group was the adjacent tissues.TNM staging was completed in accordance with the 2018 NCCN guidelines and the postoperative pathology of colon cancer patients.Immunohistochemistry was performed to detect the expressions of HMGA2 protein and PBX3 protein in colon cancer tissues and adjacent tissues.We analyzed the expression differences of HMGA2 protein and PBX3 protein in the two groups,the relationship between the expression of HMGA2 protein and PBX3 protein and age,sex,tumor size,degree of differentiation,lymph node metastasis,TNM staging and other postoperative clinicopathological factors in patients withχ2 test.Pearson correlation was employed to analysis the correlation between the expression of HMGA2 protein and PBX3 protein in colon cancer tissues.The expressions of HMGA2 and PBX3 proteins were analyzed by Kaplan-Meier method and Log-rank test to analyze the relationship between DFS and OS in patients with colon cancer after surgery.Finally,prognostic factors were estimated by single-factor and multi-factor COX proportional hazard models,and calculate the hazard ratio（HR）and its 95%confidence interval（CI）.Results:1.Among 65 colon cancer tissues,45（69.23%）were positive for HMGA2protein expression,10 of the 65 adjacent tissues（15.38%）were positive for HMGA2protein expression,and the difference between the two groups was statistically significant（P<0.001）.Among 65 cases of colon cancer,26 cases（40.00%）were positive for PBX3 protein,10 of 65 adjacent tissues（15.38%）were positive for PBX3protein expression,there were differences between the two groups Statistical significance（P=0.002<0.05）.2.Among 65 colon cancer tissues,22（33.85%）were positive for HMGA2protein and PBX3 protein,23（35.38%）were positive for HMGA2 protein and negative for PBX3 protein,4（6.15%）were negative for HMGA2 protein and positive for PBX3 protein expression,16（24.62%）cases of HMGA2 protein and PBX3protein expression were negative.The protein expressions between HMGA2 and PBX3 were positively correlated in colon cancer（r=0.272,P=0.028<0.05）.3.In 23 cases of colon cancer tissues with lymph node metastasis,20 cases had positive HMGA2 protein expression,and the positive expression rate was 86.96%.In42 cases of colon cancer tissues without lymph node metastasis,25 cases had positive and positive HMGA2 protein expression.The expression rate was 59.52%,and the difference was statistically significant（P=0.022<0.05）.Among 39 cases of high and moderately differentiated colon cancer tissues,23 cases had positive HMGA2 protein expression,and the expression rate was 58.97%.Among 26 low and undifferentiated colon cancer tissues,22 cases were positive for HMGA2 protein expression,the positive rate was 84.62%,and the difference was statistically significant（P=0.028<0.05）.In 36 cases of TNM stage I and II colon cancer tissues,20 cases were positive for HMGA2 protein expression,and the positive rate of 55.56%.Among 29 cases of colon cancer tissues with TNM stage III and IV,25 cases were positive,and the positive rate was 86.21%,and the difference was statistically significant(P=0.008<0.05.In the group comparison of patients’gender,age,tumor site,tumor size,and depth of invasion,there was no statistically significant difference in the expression of HMGA2 protein in colon cancer tissues（P>0.05）.4.Of the 37 cases colon cancer tissues that muscle layer invasion,19 cases had positive PBX3 protein expression,with a positive expression rate of 51.35%.Among28 cases of colon cancer tissues that did not invade the muscle layer,7 cases had positive PBX3 protein expression,the expression rate was 25.00%,and the difference was statistically significant（P=0.032<0.05）.Among 36 cases of colon cancer tissues with TNM stage I and II,10 cases had positive PBX3 protein expression,and the positive expression rate was 27.78%,of the 29 cases colon cancer tissues with TNM stage III and IV stage,16 cases had positive PBX3 protein expression,with a positive expression rate of 55.17%,and the difference was statistically significant（P=0.025<0.05）.In the group comparison of patient gender,age,tumor site,tumor size,differentiation,and whether there is lymph node metastasis,there was no statistically significant difference in the expression of PBX3 protein in colon cancer tissues（P>0.05）.5.Follow-up of 65 patients with colon cancer in this study was performed by telephone or case review.The operation day was taken as the starting point of follow-up,and the patient was lost to follow-up,died,or the deadline（May 1,2019）as the end point of follow-up.A total of 60 follow-up data were obtained,with a follow-up rate of 92.31%.Among 60 patients with colon cancer,the median DFS of patients with positive HMGA2 protein expression was 25.64 months,and the median DFS of patients with negative HMGA2 protein expression was 40.64 months.The difference between the two groups was statistically significant（P=0.030<0.05）.Among 60 patients with colon cancer,the median DFS of patients with positive PBX3 protein expression was 23.81 months,and the median DFS of patients with negative PBX3 protein expression was 37.82 months.The difference between the two groups was statistically significant（P=0.029<0.05）.Univariate COX regression analysis showed that the degree of tissue differentiation（HR=1.979;95%CI:1.117-3.508;P=0.019）,the presence or absence of lymph node metastasis（HR=7.336;95%CI:3.825-14.069;P<0.001）,TNM stage（HR=6.577;95%CI:3.484-12.417;P<0.001）,PBX3 protein expression level（HR=1.823;95%CI:1.055-3.150;P=0.031）and HMGA2 protein expression level（HR=1.945;95%CI:1.053-3.593;P=0.034）was significantly correlated with DFS.Multivariate COX regression analysis showed that whether there was lymph node metastasis（HR=3.519;95%CI:1.181-10.488;P=0.024）,TNM stage（HR=3.347;95%CI:1.134-9.879;P=0.029）,PBX3 Protein expression level（HR=2.130;95%CI:1.158-3.917;P=0.015）and HMGA2 protein expression level（HR=2.014;95%CI:1.006-4.032;P=0.048）were independent predictors of DFS.6.Among 60 patients with colon cancer,the median OS of patients with positive HMGA2 protein expression was 43.85 months,and the median OS of patients with negative HMGA2 protein expression was 53.58 months,there was no statistically significant difference between the two groups（P=0.534>0.05）.The median OS of patients with positive PBX3 protein expression was 39.46 months,and the median OS of patients with negative PBX3 protein expression was 53.82 months,there was no statistically significant difference between the two groups（P=0.069>0.05）.Univariate COX regression analysis showed whether there was lymph node metastasis（HR=4.550;95%CI:2.444-8.473;P<0.001）and TNM stage（HR=5.772;95%CI:2.970-11.217;P<0.001）was significantly correlated with OS.Multivariate COX regression analysis showed that TNM stage（HR=4.967;95%CI:1.692-14.582;P=0.004）were independent predictors of OS.Conclusion:1.The positive expression rates of HMGA2 protein and PBX3 protein in colon cancer tissues were significantly higher than those in adjacent tissues,indicating that both expressions were up-regulated during tumorigenesis of colon cancer.2.The expression of HMGA2 protein and PBX3 protein was positively correlated in colon cancer tissues,indicating that the two proteins may play a synergistic role in the development of colon cancer.3.The expression of HMGA2 protein in colon cancer tissues was significantly related to the degree of tumor tissue differentiation,the presence or absence of lymph node metastasis,and the stage of TNM,while the expression of PBX3 protein was significantly related to the depth of tumor invasion,and the stage of TNM,suggesting that the expressions of HMGA2 protein and PBX3 protein may be related to the metastasis and aggressiveness of colon cancer.4.Colon cancer patients with positive protein expressions of HMGA2 and PBX3showed shorter postoperative DFS than those with negative expression.HMGA2 and PBX3 proteins expression levels were independent predictors of DFS,indicating that the expression of HMGA2 protein and PBX3 protein may be used as a marker to evaluate the poor prognosis of colon cancer patients. |
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