| BackgroundPJS is an autosomal dominant disorderm,charactefised by mucocutaneous hyperpigmentation and multiple benign gastrointestinal hamartomatous polyps.In addition,they are at risk for intestinal and extraintestinal cancer The relative incidence of PJS is approximately 1/120000 -1/8300 births.In earlier studies,PJS polyps were thought to be hamartomatous or hyperplastic polyps which had rare risk of risk of canceration.Along with the furthor research on PJS,it is found that some PJS polyps are adenomatoid polyps which have higher risk of canceration.And hamartoma may change to become adenomatoid polyps and cancer which is known as hamartoma-adenoma-carcinoma sequence.PJS patients have obviously higer risk to develop into cancer both in digestive tissues and parenteral organs than health people. The incidence of tumor is almost 20%in China.And the PJS families also have higer incidence of tumor than general population.Additional PJS related malignancies include cancers of the breast,lung,uterus,ovaries,cervix,and testes.The molecular mechanisms that underlie these malignancies are not fully understood.The gene responsible for PJS has been identified by linkage analysis on chromosome 19p13.3 and encodes a novel serine/threonine kinase,LKB1.Most (60-70%) patients with patients PJS show germline mutations in the LKB1 gene, with a smaller proportion of individuals presenting with sporadic PJS,and a single family presenting with complete germline deletion of the lkb1 gene.The heterogeneity of PJS suggests the possibility of the involvement of other loci, working alone or in concert with the LKB1 gene.LKB1 has been found to play a role in chromatin remodelling,cell cycle arrest,Wnt signalling,cell polarity,and energy metabolism.LKB1 has also been implicated in Wnt signalling,the authors found that XEEK1/LKB1 enhances Wnt/β-catenin mediated signaling in vivo,so we focus onβ-catenin and IFITM1,the former was the key element of the Wnt pathway,which can make ectopic cytoplasmic accumulation of this protein,and then transfer into nuclear.By binding with the transcription factor,the transcription of downstream gene,such as c-myc and cyclin D1,make cell proliferation and differentiation out of control.The latter was a component of a multimeric complex involved in the trunsduction of antiproliferative and cell adhesion signals,which maybe served as a doewstream regulator ofβ-catenin in Wnt signaling.Both of them play an important role in gastrulation formation and tumorigenesis.The up-regulation of the IFITM1 genes seems to be an early event inβ-catenin intestinal tumorigenesis.Objective:To detect gene expression of IFITM1,β-catenin and LKB1 in PJS,and make some research on their roles in the generation,development and canceration of PJS polyps, and provide further experimental basis for the clinical diagnosis and prognosis.Materials and Methods:In this report,we evaluated the expresion levels of LKB1,β-catenin and IFITM1 mRNA and protein in PJS patients from different families and human colorectal adenocarcinomas,paired non-tumor normal mucosas and colorectal cancers.We used RT-PCR method to investigate the their mRNA expression.Th-e distribution and expression of IFITM1,β-catenin and LKB1 was assessed by immunohistochemitry, and the IFITM1 protein level was checked by westernblot,then immunofluorescence was performed to check the co-expression of IFITM1 andβ-catenin.Statistical analysisValues represent the mean(?)±SD.The date of RT-PCR,Westernblot and Immunofluorescence among the four groups were evaluated with A One-way ANOVA.Kruskal-Wallis test and Mann-Whitney U-test were used to assess the differences of staining intensity.Partial correlation was used to determine whether there was a positive or negative correlation.Differences were considered significant if P＜0.05.These analyses were made using SPSS Version 13.0(SPSS,Chicago,IL, USA).Results:1,The ratio of LKB1 IOD and GAPDH IOD in PJS polyps(0.451±0.118) was significantly different compared to that in paired normal mucosas(0.219±0.071 ) and colorectal cancers(0.787±0.151 )(Oneway Anova analysis,F=34.227,P＜0.001),it was no significant difference between PJSmucosas and colon adenoma (0.515±0.146).The expression levels ofβ-catenin and IFITM1 in PJS polyps (0.360±0.134,0.384±0.102 ) were significantly lower compared to that in colorectal adenomas(0.521±0.131,0.558±0.105) and colorectal cancers(0.521±0.131, 0.558±0.105)(Oneway Anova analysis,F=51.397,P＜0.001 ),and higher versus normal mucosas(0.218±0.055).There were similar statistically significant(P＜0.001) differences in the levels ofβ-catenin and IFITM1 expression in PJS polyps versus colorectal adenomas and colorectal cancers.2.In normal colonic mucosas,β-catenin and IFITM1 were detected in the cell membranes of epithelial cells,LKB1 was detected in the cytoplasmic of epithelial cells.The LKB1 expression intension in PJS were significantly different from that in colorectal adenoma,carcinoma and normal mucosa(Kruskal-Wallis H test,χ~2=30.584,P=0.000＜0.05) Reduced membranous expression,cytoplasmic expression were found in the PJS polyps,colorectal adenomas,and colorectal cancers. The reduced membranousβ-catenin expression rate was 30.0%in PJS polyps,which was significantly different from that in colorectal adenoma(44.0%), carcinoma(68.0%)and normal mucosa(5.0%)(R×Cχ~2 test,χ_P~2=19.519, P=0.000＜0.05).The cytoplasmicβ-catenin intension in PJS were significantly different from that in colorectal cancers and normal mucosas(Kruskal-Wallis H test,χ~2=30.584,P=0.000＜0.05).The IFITM1 expression intension in PJS were significantly different from that in colorectal carcinoma and normal mucosa (Kruskal-Wallis H test,χ~2 =30.584,P=0.000＜0.05 ) The nuclearβ-catenin expression was rarely found in PJS and colorectal adenoma.3.The protein level of IFITM1 was lower in PJS polyps than colorectal adenomas and carcinomas,and higher than in normal mucosa(F=30.182 0.000).4.The distribution and intention ofβ-catenin and IFITM1 were similar,in PJS polyps and colorectal neoplasm they located mostly in membranes and cytoplasmic of epithelial cells,in normal mucosas they located mostly in membranes.By One-way anova analysis the difference of the doubel labelled-positive cells rate is explicit (F=30.182,P=0.000＜0.05).Doubel labelled-positive cells rate ofβ-catenin and IFITM1 in PJS were significantly different from that in colorectal adenomas, carcinomas and normal mucosa.Conclusion:1.LKB1 showed significant positive correlations withβ-catenin and IFITM1.2.β-catenin is co-localized with IFITM1,the activated Wnt/β-catenin signaling pathway including IFITM1 might play an important role in the occurrence and development of PJS polyps.3.The aberrent expression of Wnt/β-catenin signaling pathway may be caused by the expression of LKB1 in PJS polyps. |
