CD 44V6、β-catenin 在骨肉瘤中的表达及其临床意义

目的：检测CD44V6、β-catenin在骨肉瘤组织中的表达,分析其表达与人骨肉瘤细胞侵袭及转移能力的相关性。方法：应用免疫组织化学方法检测35例骨肉瘤、15例骨软骨瘤、15例正常骨组织中CD 44V6、β-catenin的表达。结果：骨肉瘤组织中CD 44V6、β-catenin的阳性表达显著高于骨软骨瘤及正常骨组织（P〈0.01）;两者的表达分别与骨肉瘤临床分期、肿瘤转移及2年内死亡有关（P〈0.05）,而与患者性别、年龄、肿瘤大小、病理分型、术前化疗无关（P〉0.05）;两者的阳性表达呈正相关（P〈0.01）。结论：CD 44V6、β-catenin在骨肉瘤中的阳性表达与骨肉瘤的发生、发展和转移密切相关,可能在骨肉瘤细胞侵袭、转移的过程中起协同作用;联合检测CD 44V6、β-catenin可以作为骨肉瘤诊断及其转移预测的指标。     

β-连环素与上皮型钙粘蛋白在宫颈鳞癌中的表达及意义

目的　探讨 β 连环素 (β cat)与上皮型钙粘蛋白 (E cad)在宫颈鳞癌中的表达及其临床意义。 方法　应用免疫组化SP法 ,检测 4 0例宫颈鳞癌 ,1 0例宫颈上皮内瘤样病变 (CIN)和 1 0例正常宫颈上皮组织中的 β cat与E cad的表达。结果　正常宫颈上皮组织中 ,β cat与E cad表达均显著位于细胞膜 ,而胞浆表达很少见 ;在CINⅢ与宫颈鳞癌组织中 ,β cat与E cad表达特征发生改变 ,胞膜表达量减少甚至缺失 ,呈现不同程度的胞浆表达 ,其中有些在细胞核内还可检出 β cat蛋白。随着肿瘤病理分级的升高 ,β cat与E cad的膜表达减弱 ,浆表达增强。淋巴结转移组的 β cat与E cad的异常表达率明显高于无淋巴结转移组 (P <0 .0 5 )。 结论　β cat异位表达可能参与了宫颈鳞癌发生、发展过程 ;β cat与E cad胞膜表达缺失可能与宫颈鳞癌的侵袭和转移有关。     

Activation of Wnt/beta-catenin/Tcf signaling in mouse skin carcinogenesis

Although Wnt/beta-catenin/Tcf signaling pathway has been shown to be an important factor in the development of many malignancies including colorectal, ovarian, prostate, and many other cancers, little is known about its role in non-melanoma skin cancers. Here, we report the first evidence that beta-catenin/Tcf signaling pathway is constitutively activated in non-melanocytic skin tumors induced by two stage chemical carcinogenesis protocol. Mouse skin tumors showed cytoplasmic and nuclear accumulation of beta-catenin, and upregulation of beta-catenin/Tcf target genes (c-myc and c-jun). We found high levels of skin-expressed Wnt proteins (Wnt 3, 4, and 10b) in different parts of the tumors, likely representing key upstream events in beta-catenin/Tcf activation during mouse skin carcinogenesis. Inhibition of beta-catenin/Tcf signaling by ectopic expression of dominant negative Tcf4 resulted in significant inhibition of growth in squamous cell carcinoma cells. A role of the constitutive activation of beta-catenin/Tcf signaling in skin carcinogenesis is discussed.     

Truncated E-cadherin potentiates cell death in prostate epithelial cells

BACKGROUND: E-cadherin, a fundamental component of the adherens junction, is known to mediate aggregation-dependent cell survival. We have previously identified a novel, calpain-dependent proteolytic cleavage of E-cadherin that resulted in the generation of a stable 100-kDa E-cadherin fragment (E-cad(100)) in prostate epithelial cells in response to cell death stimuli. We postulated that the E-cad(100) fragment may play a role in abrogating survival of LNCaP cells following induction of apoptosis. METHODS: Wild-type E-cadherin and E-cad(100) were engineered, tagged with GFP, and stably expressed in LNCaP cells. These cell lines were characterized for E-cadherin-GFP/beta-catenin interactions, endogenous E-cadherin and beta-catenin expression, and sensitivity to apoptosis induced by PKC activation. RESULTS: E-cad(100)-GFP demonstrated a punctuate expression pattern, in contrast to E-cad(120)-GFP, which was membrane-localized. E-cad(100)-GFP, unlike E-cad(120)-GFP, failed to bind to and co-localize with beta-catenin. Transient or stable overexpression of E-cad(100) resulted in the downregulation of endogenous E-cadherin expression at the cell membrane. Activation of PKC in LNCaP cells which overexpressed E-cad(100) potentiated cell death. CONCLUSIONS: Truncated E-cadherin may play a role in the regulation of endogenous E-cadherin expression and epithelial cell survival.     

Cribriform-morular variant of papillary thyroid carcinoma: a pathological and molecular genetic study with evidence of frequent somatic mutations in exon 3 of the beta-catenin gene

The cribriform-morular variant (C-MV), an unusual and peculiar subtype of papillary thyroid carcinoma (PTC), has been observed frequently in familial adenomatous polyposis (FAP)-associated thyroid carcinoma and also in sporadic thyroid carcinoma. In this paper, five young women with the C-MV of PTC, aged 22-34 years at cancer diagnosis, are reported; two of them had attenuated FAP. Grossly, one FAP-associated tumour and one sporadic tumour were multicentric and the others were solitary. Histologically, the tumours were encapsulated and exhibited a combination of cribriform, follicular, trabecular, solid, and papillary patterns of growth, with morular areas. Immunohistochemically, the tumour cells showed cytoplasmic expression of thyroglobulin, neuron-specific enolase, epithelial membrane antigen, high- and low-molecular-weight cytokeratins, vimentin, and bcl-2 protein; nuclear expression of oestrogen and progesterone receptors, and retinoblastoma protein; and cytoplasmic and nuclear accumulation of beta-catenin. Germline mutations of the adenomatous polyposis coli (APC) gene were investigated using the protein truncation test in four subjects, including two FAP individuals. Germline APC mutation was identified in only one FAP patient with the multicentric C-MV of PTC, who had a thymidine deletion at codon 512, resulting in a frameshift leading to a premature stop codon. No loss of heterozygosity of loci close to the APC gene was detected in tumour tissues from these four patients. Somatic mutation analysis of exon 3 of the beta-catenin gene (CTNNB1) revealed alterations in seven tumours from all five individuals: one at a serine residue (codon 29), three at amino acids adjacent to serine or threonine residues (codons 22, 39, and 44), and three at other amino acids (codons 49, 54, and 56). Moreover, each of two different tumours examined from two patients with the multicentric C-MV of PTC, had different somatic mutations of the CTNNB1 gene. Taken together, these data suggest that accumulation of mutant beta-catenin contributes to the development of the C-MV of PTC.     

Epigenetic and genetic alterations of APC and CDH1 genes in lobular breast cancer: relationships with abnormal E-cadherin and catenin expression and microsatellite instability

The causes and functional consequences of E-cadherin (E-CD) loss in breast cancer are poorly understood. E-CD loss might act in concert with alterations in the APC/beta-catenin pathway to permit oncogenic beta-catenin signaling. To test this hypothesis, we have analyzed the presence of genetic and epigenetic alterations affecting E-CD (CDH1), APC and beta-catenin (CTNNB1) genes and the immunohistochemical expression of E-CD, beta- and gamma-catenin in a series of 46 infiltrating lobular breast carcinomas (ILCs). Since 80% of ILCs featured complete loss of E-CD expression, we analyzed the molecular alterations responsible for E-CD inactivation in these tumors. We found that 10 of 46 (22%) cases harbored mutations in CDH1, including 1 case with 2 different mutations (1 of which was germline). CDH1 was also inactivated by loss of heterozygosity (LOH; 30/41, 73%) and promoter hypermethylation (19/46, 41%). Interestingly, LOH and mutations were also detected in the corresponding in situ lesions of the ILCs, implying that these alterations are early events in lobular cancer tumorogenesis. Additionally, the presence of a polymorphism in the CDH1 promoter was found to be inversely correlated with CDH1 mutations, but not with E-CD levels. We next examined whether alterations in the APC/beta-catenin pathway also occurred in the same series of ILCs. Although no CTNNB1 or APC mutations were detected, promoter methylation (25/46, 52%) and LOH (7/30, 23%) of APC were found. Moreover, methylation of APC and CDH1 occurred concordantly. However, beta- and gamma-catenin were severely reduced or absent in 90% of these tumors, implying that alterations in CDH1 and APC genes do not promote beta-catenin accumulation in ILC. These molecular alterations were not associated with microsatellite instability. In summary, several different mechanisms (mutations, LOH, methylation) are involved in the frequent CDH1 inactivation in invasive and in situ lobular breast cancer. The same tumors also show genetic and epigenetic alterations of APC gene. However, altered CDH1 and APC genes do not promote beta-catenin accumulation in this tumor type.