Frequent inactivation of SPARC by promoter hypermethylation in colon cancers

Abstract

Epigenetic modification of gene expression plays an important role in the development of human cancers. The inactivation of SPARC through CpG island methylation was studied in colon cancers using oligonucleotide microarray analysis and methylation specific PCR (MSP). Gene expression of 7 colon cancer cell lines was evaluated before and after treatment with the demethylating agent 5-aza-2 0 -deoxycytidine (5Aza-dC) by oligonucleotide microarray analysis. Expression of SPARC was further examined in colon cancer cell lines and primary colorectal cancers, and the methylation status of the SPARC promoter was determined by MSP. SPARC expression was undetectable in 5 of 7 (71%) colorectal cancer cell lines. Induction of SPARC was demonstrated after treatment with the demethylating agent 5Aza-dC in 5 of the 7 cell lines. We examined the methylation status of the CpG island of SPARC in 7 colon cancer cell lines and in 20 test set of colon cancer tissues. MSP demonstrated hypermethylation of the CpG island of SPARC in 6 of 7 cell lines and in all 20 primary colon cancers, when compared with only 3 of 20 normal colon mucosa. Immunohistochemical analysis showed that SPARC expression was downregulated or absent in 17 of 20 colon cancers. A survival analysis of 292 validation set of colorectal carcinoma patients revealed a poorer prognosis for patients lacking SPARC expression than for patients with normal SPARC expression (56.79% vs. 75.83% 5-year survival rate, p 5 0.0014). The results indicate that epigenetic gene silencing of SPARC is frequent in colon cancers, and that inactivation of SPARC is related to rapid progression of colon cancers. ' 2007 Wiley-Liss, Inc.

SPARC promoter hypermethylation in colorectal cancers can be reversed by 5-Aza-2′deoxycytidine to increase SPARC expression and improve therapy response

“…This finding differs from a recent study by Yang et al (2007), where only partial methylation (and no hypermethylation) was observed in their cases of colorectal cancers within a shorter 221 bp region of the SPARC promoter (Yang et al, 2007). One possible explanation to account for this difference between our studies may be in the processing of the clinical samples: all of the samples used in the current study were laser capture microdissected to minimise potential contamination of either normal colonic epithelium in our colorectal cancer specimens, and vice versa.…”

“…Aberrant hypermethylation of the SPARC promoter has also been observed in cancers of the lung (Suzuki et al, 2005), prostate (Wang et al, 2005), endometrium (Rodriguez-Jimenez et al, 2007) and leukaemia cell lines (DiMartino et al, 2006). Recent studies using genome-wide screening to identify genes that are targeted for aberrant methylation in tumours have also consistently shown SPARC expression to be inducible by 5-Aza-2 0 deoxycytidine, in pancreatic (Sato et al, 2003), cervical (Sova et al, 2006), and colorectal cancer cell lines (Yang et al, 2007). In this study, we found an overall methylation pattern of 60% in the SPARC promoter of primary colorectal cancer specimens, while only 28% of the CpG sites were partially methylated.…”

Differential survival trends of stage II colorectal cancer patients relate to promoter methylation status of PCDH10, SPARC, and UCHL1

“…This is also supported from animal models were SPARC deficiency strongly suppressed adenoma formation in the intestine in Sparc knockout mice intercrossed with Apc(Min/ þ ) mice. 39 In contrast, a significant association of SPARC methylation and poorer prognosis was reported by Yang et al 40 Although the authors analyzed a large cohort of patients, they did not differentiate between tumor stages nor did they consider stratification by chemotherapy. In our study, SPARC promoter methylation tended to be associated with shortened overall survival and disease-free survival, only in patients who received chemotherapy.…”

Lymphovascular invasion of colorectal cancer is correlated to SPARC expression in the tumor stromal microenvironment

“…[7][8][9][10][11][12] In colorectal cancer (CRC), the role of SPARC is not well understood. 13,14 SPARC is expressed not only by cancer cells but also by stromal cells surrounding the tumor. 5 Tumor-associated stromal cells such as cancer-associated fibroblasts are important components of the tumor microenvironment, where their interaction with cancer cells leads to the production of regulatory growth factors…”