Transcriptional silencing of secreted frizzled related protein 1 (SFRP1) by promoter hypermethylation in non-small-cell lung cancer

Abstract

Secreted frizzled related protein 1 (SFRP1) is an antagonist of the transmembrane frizzled receptor, a component of the Wnt signaling pathway, and has been suggested to be a candidate tumor suppressor in several human malignancies. Since SFRP1 is located at chromosome 8p11, where lung cancers also exhibit frequent allelic loss, we hypothesized that the inactivation of SFRP1 is also involved in lung carcinogenesis. To substantiate this, we performed mutational analysis of SFRP1 for 29 nonsmall-cell lung cancer (NSCLC) and 25 small-cell lung cancer (SCLC) cell lines, and expression analysis for the same cell lines. Although somatic mutations were not detected in the coding sequence, downregulation of SFRP1 was observed in 14 (48%) NSCLC and nine (36%) SCLC cell lines. We analysed epigenetic alteration of the SFRP1 promoter region and detected hypermethylation in 15 (52%) of 29 NSCLC cell lines, two (8%) of 25 SCLC cell lines, and 44 (55%) of 80 primary lung tumors. By comparing the methylation status with SFRP1 expression, we found a significant correlation between them. We also performed loss of heterozygosity (LOH) analysis and found that 15 (38%) of 40 informative surgical specimens had LOH in the SFRP1 gene locus. Furthermore, we performed colony formation assay of two NSCLC cell lines (NCI-H460 and NCI-H2009) and found the reduction of colony formation with SFRP1 transfection. In addition, we also detected that SFRP1 inhibits the transcriptional activity of b-catenin, which is thought to be a downstream molecule of SFRP1, with luciferase reporter assay. Our current studies demonstrated that the SFRP1 gene is frequently downregulated by promoter hypermethylation and suppresses tumor growth activity of lung cancer cells, which suggests that SFRP1 is a candidate tumor suppressor gene for lung cancer.Oncogene (

Frequent epigenetic inactivation of Wnt antagonist genes in breast cancer

“…Because none of the breast cancer cell lines presented aberrant TCF/LEF transcription, we used an expression vector encoding a b-catenin mutant to boost Wnt signalling. We found that the TCF/LEF transcriptional activity induced by the mutant b-catenin was synergistically upregulated when combined with SFRP1 depletion, which is consistent with the recent observation by Fukui et al (2005). Using non-small-cell lung carcinoma cells in which SFRP1 was methylated, they showed that when SFRP1 was cotransfected with mutant b-catenin, SFRP1 could attenuate TCF/LEF activity induced by exogenous b-catenin.…”

“…Consistent with that idea, we have previously found that SFRP1 is methylated in several breast cancer cell lines (Suzuki et al, 2002), and two other groups recently reported frequent SFRP1 methylation in both primary and cultured breast cancer cells (Lo et al, 2006;Veeck et al, 2006). To date, epigenetic silencing of SFRP1 has been identified in a variety of malignancies, including cancers of the bladder (Stoehr et al, 2004), prostate (Lodygin et al, 2005), lung (Fukui et al, 2005) and breast, although abnormalities involving other SFRP family genes are largely unexplored.We previously showed that SFRP1, SFRP2 and SFRP5 are frequently inactivated in CRC and gastric cancer (GC) (Suzuki et al, 2002;Nojima et al, 2007), and that SFRPs suppress constitutive Wnt signalling when overexpressed in CRC and GC cells. Similarly, Bafico et al (2004) reported that constitutive Wnt signalling could be suppressed in breast cancer cells by SFRP1 and DKK1.…”

“…Consistent with that idea, we have previously found that SFRP1 is methylated in several breast cancer cell lines (Suzuki et al, 2002), and two other groups recently reported frequent SFRP1 methylation in both primary and cultured breast cancer cells (Lo et al, 2006;Veeck et al, 2006). To date, epigenetic silencing of SFRP1 has been identified in a variety of malignancies, including cancers of the bladder (Stoehr et al, 2004), prostate (Lodygin et al, 2005), lung (Fukui et al, 2005) and breast, although abnormalities involving other SFRP family genes are largely unexplored.…”

Involvement of genetic instability in the downregulation of sFRP1 in Chinese patients with hepatocellular carcinoma

“…Interestingly, sFRP1 functions as a negative regulator of the Wnt pathway and blocks the activation of the downstream target genes (Kawano and Kypta, 2003). Downregulation of the sFRP1 has been found in a variety of malignancies including colon (Caldwell et al, 2004), breast (Veeck et al, 2006), bladder (Stoehr et al, 2004), ovarian (Takada et al, 2004), and lung (Fukui et al, 2005) cancers. It has been reported that reconstitution of sFRP1 inhibits HCC growth in vitro and in vivo, and the sFRP1 restoration offers a potential therapeutic approach for treatment of HCC (Hu et al, 2009;Jiang et al, 2010).…”

“…Decrease in the sFRP1 expression due to promoter hypermethylation may result in the activation of the Wnt pathway and consequent tumor development. Interestingly, reduced expression of sFRP1 has been found in many malignancies, including colorectal (Caldwell et al, 2004;Suzuki et al, 2004), lung (Fukui et al, 2005), ovarian (Takada et al, 2004), breast (Veeck et al, 2006), esophageal (Zou et al, 2005;Clement et al, 2006), and liver (Shih et al, 2006) cancers.…”