| Objective:Gastric cancer,the most common gastrointestinal malignancy,is an important public health event,although its incidence and mortality rate have been decreasing for several decades.Although with early diagnosis and early treatment,the prognosis of GC remains poor and the overall 5-year survival rate is still less than 40%.The prognosis indicators include pathology findings of histological type,invasion and metastasis,imaging results of classifications and other clinical characteristics like age and underlying diseases.However,there are still lots of limitations for these traditional indicators.Currently,biomarkers like p27,cyclin E,E-cadherin,c-erbB2,cmyc,tumor suppressor gene p53,and so on,have been reported to be effective prognosis factors for GC patients[4].However,Little of these factors can serve as an indictor of cancer diagnosis and treatment.So it is necessary to explore new indicators,with higher expression in gastric cancer tissues than normal tissues,which can be easily detected and applied to clinical diagnosis and treatment.Mixed lineage leukemia(MLL)genes include MLL,MLL2,MLL3,MLL4 and MLL5,and encode proteins that can act as histone methyltransferases[1-3].The MLL proteins include MLL,MLL2,MLL3,MLL4,SET1A and SET1B,which regulate histone 3-lysine4(H3K4)methylation,a modification associated with transcriptionally active genes[1].The MLL gene is often involved in the chromosomal translocations associated with acute leukemias[2].Lei Ming,et al.found that the structural,biochemical,and computational analyses reveal a two-step activation mechanism of MLL-family proteins:interaction with the RbBP5-Ash2L heterodimer reduces the inherent flexibility of MLLset and favors to form a catalytically competent conformation;and the H3 substrate binding induces a local conformational change in the SET-I motif of MLLset to achieve the fully active configuration that facilitates the methyl transfer process.This is the way to active MLL-family histone methyltransferases and maybe the way to affect on tumorigenesis,as histone modification of chromatin has long been recognized as an important step in cancer development.And,the expression of MLL genes are identified not only in hematopoietic cells,but also in other non-hematopoietic cells[4-7].MLL4 gene is amplified and expressed in glioblastomas and pancreatic cancer[8].Previous studies have reported frameshift mutations of MLL,MLL2,MLL3 and MLL5 genes in gastric cancer,and these mutation were found exclusively in the cancer with MSI-H.But what is less studied are the abnormal expression of MLL and MLL4 in gastric cancer and how they play the role in the disease.The expression of MLL and MLL4 in gastric malignant tissues and normal stomach tissueshas been examined in our study using technological method.And for the first time we explored the corelationship between MLL,MLL4expression andgastric cancers' clinicopathological parameters,in the same time,detected if the over expression of MLL and MLL4 will impact the survivals of patients.Methods:242 stomach samples were chosen from gastrectomy which were retrospectively enrolledfrom Provincial Hospital between January 1st in 2008 and December 31th in 2010.We have got the specimen after surgeryfrom pathology apartment and send them to related corporation to be made into tissue chips.Of them all,gastric cancer tissues were 190 cases,of which 180 cases have complete follow-up data,most of the cases(189 cases)were gastric adenocarcinoma tissues,of all 2 cases were adenocarcinoma with neuroendocrine tissues.Of all 1 case was squamous-cell carcinoma tissue.There are 42 cases of para-carcinoma tissues,9 cases of gastric stromal cancer tissue and 2 cases of chronic gastric ulcer tissues which were all included into thetissue microarray.We have examined the expression of MLL and MLL4 protein in all the 242 cases of tissue microarray using immunohistochemical technique.The expressionof MLL and MLL4 was evaluated and scored by two independent pathologists who had no knowledge of the clinicopathological information and patient outcome.A modified immunoreactive score(IRS)[9]was referred to,which took into account the percentage of stained cells(no staining,0;<10%,1;10-50%,2;51-80%,3;>80%,4)and the staining intensity(no staining,0;weak,1;moderate,2;strong,3).The final score(ranging from 0 to 12)was obtained in each case by multiplying the percent-age and the intensity scores.A two-grade scale system was applied for subsequent statistical analyses.Tumor specimens scoring<4 were considered as low expression,whereas those scoring>4 as high expression.About how to process the data,we used the SPSS Mac 23.0 software.Acquisition of the relationship between MLL,MLL4 expression and related cilinicopathological parameter,the factors whicheffect the prognosis of gastric cancer patients using Spearman's logical analysis and Kaplan-Meier test respectively.This is a two-sided test,in which significance is defined P<0.05.Results:1.The abnormal or over expression of MLL in gastric cancer cells were mainly distributed in the cytoplasm.The over expression of MLL4 in gastric cancer cells were mainly distributed in the cytoplasm and nuclear.The over expression of MLL and MLL4 in cytoplasm were also detected in pare-carcinoma cells,gastric stromal cancer cells and chronic gastric ulcer cells with low expression or no expression in nuclear.2.Spearman's logical analysis showed that the over expression of MLL in cancer cytoplasm and the over expression of MLL 4 in cancer nuclear were obviously related to tumor lymph node metastasis which is an traditional marker of tumor aggressiveness.Patients' gender,age,the depth of invasion,TNM stage,tumor differentiation grade and the status of tumor marker played no role.Patients' age of onset may workas some function to the over expression of MLL4 in gastric cancer cytoplasm.3.Mann-whitney U test showed that the expression of MLL and MLL4 in gastric cancer tissues is much higher than that in related para-carcinoma tissues.4.As for the 5 year survival rate,showed in Life Table,patients with high or over expression of MLL was 41.0%,patients with low or no expression of MLL was 48.4%,with no significant difference in statistics.Patients with high or over expression of MLL4 in cancer cytoplasm was 44.5%,low or no expression was 40.4%,with no significant difference in statistics.High or over expression of MLL4 in cancer nuclear was 42.1%,low or no expression was 43.5%.,with no significant difference in statistics.5?We have used Unilabiate Long-rank test to determine which factors would effect in the prognosis of gastric cancer patients.The positive factors are tumor invasion depth,the number of lymph node metastasis,post surgery TNM stage,standardadjuvant treatment after surgery and what operation is performed(P<0.05).Of all the positive factors local lymph node metastasis is most important,because it plays the way independently.Conclusions:1?The expression of MLL and MLL4 in gastric cancer tissues is especially higher than that in para-carcinoma tissues,which implicate that MLL and MLL4 may play as new markers of diagnosis and treatment.2?The expression of MLL in cancer cytoplasm and the expression of MLL4 in cancer nuclear are significantly related with the lymph node metastasis,which is an traditional indicator of tumor aggressiveness.So that the expression of MLL and MLL4 in gastric cancer may be correlated with more aggressive tumor type of gastric cancer.The mechanism is worth more research and discussion.3?The study didn't find significant difference between the expression of MLL and MLL4 and prognosis in gastric cancer patients.However,we found that the high expression of MLL and MLL4 correlate to more lymph nodes metastasis,which is an traditional indicator of tumor aggressiveness and is an independent indicator of tumor prognosis.In conclusion,the relationship between MLL and MLL4 expression and patients' prognosis deserve more research.4?The prognosis of gastric cancer patients is related to the depth of tumor invasion,the numbers of lymph nodes metastasis,TNM stage,treatment after operation and operation methods,but not related to patients' sex,ages,tumor differentiation degree and tumor marker.Lymph nodes metastasis is an independent influence factor to patients' prognosis. |
PDF Full Text Request