Expression of Smad2 and Smad4 in cervical cancer: absent nuclear Smad4 expression correlates with poor survival

Abstract

Alterations in transforming growth factor-b signaling, due to a decrease in Smad2 and especially Smad4 expression, has primarily been reported in pancreatic and colorectal cancers, although loss of the chromosomal region 18q21.1, containing the loci of Smad2 and Smad4, is among the most frequent molecular alterations in cervical cancer. The aim of our study was to investigate whether decreased Smad2 and Smad4 protein expression in primary cervical cancers is associated with molecular alterations at 18q21.1, mutations in the functional domains of Smad2 and Smad4 or hypermethylation, and to assess the biological relevance of decreased Smad2 and Smad4 expression. Subsequently, Smad2, Smad4 and p21 protein expression was determined by immunohistochemistry in 117 primary cervical carcinomas, assembled in a tissue array. Smad signaling was shown to be associated with p21 mRNA expression. All the tumors expressed Smad2 or Smad4. Weak cytoplasmic Smad2 or weak cytoplasmic Smad4 expression could not be attributed to loss of heterozygosity at 18q21.1. Despite weak/moderate Smad2 expression and absent nuclear Smad4 expression, the coding regions of the functional MH1 and MH2 domains of Smad2 and Smad4 were unchanged, as assessed by sequence analysis. The Smad4 promoter region was unmethylated in tumor samples with weak/moderate cytoplasmic Smad4 expression. Remarkably, both weak cytoplasmic Smad4 expression and absent nuclear Smad4 expression significantly correlated with poor disease-free (P ¼ 0.003 and P ¼ 0.003, respectively) and overall 5-year survival (P ¼ 0.003 and P ¼ 0.010, respectively). Our findings support the hypothesis that Smad4 is a target molecule for functional inactivation in cervical cancer.

Involvement of the TGF-β and β-Catenin Pathways in Pelvic Lymph Node Metastasis in Early-Stage Cervical Cancer

“…Furthermore, TGF-b is directly involved in the formation of metastases, as it contributes to the establishment and outgrowth of lung and bone metastases in breast cancer models (32,34). Smad4 downregulation is associated with TGF-b downregulation and has been implicated in cervical cancer (30) and metastatic mouse models (32). The downregulation of Smad4 in N þ is consistent with these data and establishes TGF-b as one of the pathways affecting the metastatic potential in early-stage cervical cancer.…”

“…Also the percentage of positive cells was recorded. Positive Smad4 expression was defined as presence of both more than 50% moderate/strong positive nuclear and moderate/strong positive cytoplasmic staining (30). b-catenin and p120 positivity was defined as membranous staining at any intensity (1-3) in more than 50% of cells (31).…”

SLC5A8 Nuclear Translocation and Loss of Expression are Associated With Poor Outcome in Pancreatic Ductal Adenocarcinoma

“…For example, loss of heterozygosity at 18q, the locus of Smad4, is a common mechanism for inactivation of Smad4 in pancreatic cancer. 28 Kloth and colleagues 29 reported that weak cytoplasmic and absent nuclear expression of Smad4 were associated with poor survival in cervical cancer patients. In another study, nuclear expression of maspin, a member of the serine protease inhibitors family, has been associated with tumor status 30,31 and a better prognosis in pancreatic cancer.…”

Adenovirus encoding Smad4 suppresses glioma cell proliferation and increases apoptosis through cell cycle arrest at G1 phase

“…The loss of Smad4 protein expression in the cytoplasm (36 of 114, 32%) and in the nucleus (46 of 114, 40%) of tumor cells has been found [13]. Moreover, the loss of nuclear Smad4 expression in primary tumors has been found to be significantly correlated with poor survival and has been used as an independent prognostic marker in multivariate analysis [16][17][18].…”