The Expression And The Clinical Significance Of Detecting SSTR2 And PTEN Protein In Colorectal Cancer

Colorectal cancer is a common malignant tumor,its morbidity and mortality of our country has an upward trend year after year.Only about 5%of patients with early colorectal cancer have been diagnosed and 60%-70%of those who have been advanced colorectal cancer when they are diagnosed.Five year survival rate of the patients with colorectal cancer after operation is about 50%,and the recurrence rate is up to 30%,which seriously affects the quality of life and health of people.Surgical treatment of colorectal cancer is recognized as the preferred method.The efficacy of surgery combined with adjuvant chemotherapy,radiotherapy or biological target therapy has shown superiority in colorectal cancer therapy,but each adjuvant treatment still has its shortcomings.Somatostatin(SST) is a cyclic peptide hormone,which has a wide range of biological activity.Somatostatin binding of the specific somatostatin receptor of target cell membrane exerts its biological activity.It can inhibit nearly all internal and external secretory function,reduce visceral blood flow,suppress smooth muscle contraction and also have a certain degree of inhibition on the activity of immune cells.In recent years,animal experiments and human outside the cell line studies have shown that somatostatin receptor(SSTR) mediated through somatostatin and its analogues (SSTA) exerts anti-tumor effect,such as inhibition of cell growth, induction of apoptosis,anti-tumor proliferation,inhibition tumor angiogenesis,regulation of immune cell activity,which can inhibit the proliferation of many endocrine tumors and solid tumors.Somatostatin receptor is located in cell membrane,which is G protein-coupled receptor that has been cloned and identified as five kinds of receptor subtypes.Different subtypes of receptor mediated exerting different use:SSTR2 primarily mediates inhibition of the release of growth hormone,has the use of anti-tumor proliferation and induced apoptosis,and is considered as the dominant subtype of anti-tumor effect;SSTR3 is related to apoptosis;SSTR5 mainly mediates inhibition of insulin and regulates the release of growth hormone;SSTR1,SSTR2,SSTR4 and SSTR5 can inhibit cell growth;Among them,SSTR2 is considered to be closely related to the colorectal tumor.Tumor suppressor gene PTEN(phosphatase and tensin homolog detected on chromosome ten) is the first discovered tumor suppressor gene with dual-specificity phosphatase activity.It's the role of its lipid phosphatase and protein phosphatase that makes intracellular protein phosphorylation level get fine adjustment,and impact cell growth,proliferation,differentiation,apoptosis, adhesion and migration and many other important biological behaviors. Tumor suppressor gene PTEN plays an important role in the process of the occurrence,development and metastasis of tumor.Large study show that low expression or expression loss of SSTR2 and PTEN protein is related to the malignancy of colorectal cancer,pathological stage and so on.It may play an important role at the occurrence and development of colorectal cancer.However,Whether or not there is correlation in the expression of SSTR2 and PTEN protein on colorectal cancer tissues,rarely reported.The aim of this paper is to explore the expression and clinical significance of SSTR2 and PTEN protein in colorectal carcinoma, analyze the correlation between the expression of SSTR2 and PTEN protein in colorectal carcinoma,and provide probable bases for clinical diagnosis,treatment and prognosis of colorectal cancer.We detected SSTR2 and PTEN protein in 30 cases of colorectal cancer tissues with immunohistochemical method(S-P method) and made 16 cases of normal mucosal adjacent to cancer as the control.The results showed that:SSTR2 and PTEN protein expressed at different degrees in colorectal cancer and adjacent mucosa tissues;they were mainly located in cytoplasm and cell membrane,showing brown-yellow granules. The rate of positive expression of SSTR2 in colorectal cancer group was lower than that in mucosa adjacent to cancer,but difference was not significant(P＞0.05).The rate of positive expression of PTEN proteinin colorectal cancer group was significantly lower than that in mucosa adjacent to cancer group(P＜0.05);the rate of positive expression of SSTR2 and PTEN protein in well-differentiated colorectal carcinoma were significantly higher than that in poorly differentiated ones;the expression of SSTR2 and PTEN protein in colorectal cancer had nothing to do with serosal infiltration(P＞ 0.05);In colorectal cancer group with regional lymph node metastasis, the rate of positive expression of SSTR2 was lower than that without lymph node metastasis,but there was no significant difference(P＞0.05);In colorectal cancer group with regional lymph node metastasis,the rate of positive expression of PTEN protein was significantly lower than that without lymph node metastasis group(P＜0.05).The rate of positive expression of SSTR2 in colorectal carcinoma of Dukes A and B stage is higher than that in colorectal cancer of Dukes C and D stage,but there was no significant difference (P＞0.05);The rate of positive expression of PTEN protein in colorectal carcinoma tissues of Dukes A and B stage was significantly higher than that in colorectal cancer of Dukes C and D stage(P＜0.05).Compared with the expression of SSTR2-negative colorectal cancer group,in the expression of SSTR2-positive colorectal cancer group,the rate of positive expression of PTEN protein was higher but the difference was not significant,that was to say,there was no correlation between the expression of SSTR2 and PTEN protein in colorectal cancer.Based on experimental results,we make the following conclusions: the low expression of SSTR2 is associated with the malignancy of colorectal cancer,which plays an important role in the occurrence and development of colorectal cancer.The low expression of PTEN protein is related to the differentiation of colorectal cancer,lymph node metastasis and Dukes stage,which also plays an important role in the occurrence and development of colorectal cancer.PTEN protein can be used as one of the prognostic indicators of colorectal cancer. There is no correlation between the expression of SSTR2 and PTEN protein in colorectal cancer.This experiment provides a theoretical basis for clinical application of SSTR2 and PTEN protein in colorectal cancer.