Inactivation of Wnt inhibitory factor-1 (WIF1) expression by epigenetic silencing is a common event in breast cancer

Abstract

The Wnt signaling pathway is a powerful and prominent oncogenic mechanism dysregulated in numerous cancer types. While evidence from transgenic mouse models and studies of human tumors clearly indicate that this pathway is of likely importance in human breast cancer, few clues as to the exact molecular nature of Wnt dysregulation have been uncovered in this tumor type. Here, we show that the Wnt inhibitory factor-1 (WIF1) gene, which encodes a secreted protein antagonistic to Wnt-dependent signaling, is targeted for epigenetic silencing in human breast cancer. We show that cultured human breast tumor cell lines display absent or low levels of WIF1 expression that are increased when cells are cultured with the DNA demethylating agent 5-aza-2'-deoxycytidine. Furthermore, the WIF1 promoter is aberrantly hypermethylated in these cells as judged by both methylation-specific PCR and bisulfite genomic sequencing. Using a panel of patient-matched breast tumors and normal breast tissue, we show that WIF1 expression is commonly diminished in breast tumors when compared with normal tissue and that this correlates with WIF1 promoter hypermethylation. Analysis of a panel of 24 primary breast tumors determined that the WIF1 promoter is aberrantly methylated in 67% of these tumors, indicating that epigenetic silencing of this gene is a frequent event in human breast cancer. Using an isogenic panel of cell lines proficient or deficient in the DNA methyltransferases (DNMTs) DNMT1 and/or DNMT3B, we show that hypermethylation of the WIF1 promoter is attributable to the cooperative activity of both DNMT1 and DNMT3B. Our findings establish the WIF1 gene as a target for epigenetic silencing in breast cancer and provide a mechanistic link between the dysregulation of Wnt signaling and breast tumorigenesis.

Wnt inhibitory factor 1 induces apoptosis and inhibits cervical cancer growth, invasion and angiogenesis in vivo

“…This inhibition of cell proliferation is consistent with the in vitro inhibition of cell growth by WIF1 as previously shown for other cancer cell lines (Ai et al, 2006;Kim et al, 2007;Kansara et al, 2009;Kawakami et al, 2009;Tang et al, 2009). However, in previous studies, WIF1 overexpression was shown to induce G 1 arrest in HPVimmortalized osteoblasts and osteosarcoma cell lines containing null or wild-type p53 (Kansara et al, 2009), as well as in bladder cancer cell lines containing mutant p53 (Tang et al, 2009).…”

“…WIF1 is a secreted Wnt antagonist that is often downregulated because of genomic rearrangement, genomic loss or promoter hypermethylation in several human tumors, including colon, lung, breast, prostate, bladder, kidney and salivary gland (Wissmann et al, 2003;Byun et al, 2005;Taniguchi et al, 2005;Ai et al, 2006;Urakami et al, 2006;Queimado et al, 2008;Kawakami et al, 2009). Our study demonstrates that WIF1 downregulation is an early and widespread event in human cervical oncogenesis, which occurs frequently due to promoter hypermethylation.…”

Prodigiosin inhibits Wnt/β-catenin signaling and exerts anticancer activity in breast cancer cells

“…Wnt ligands and FZD receptors are expressed in human breast cancer cell lines and primary tumors (30)(31)(32)(33). Multiple negative regulators of Wnt/β-catenin signaling, such as SFRP1, SFRP2, SFRP5, WIF1, DKK1, and DKK3, are down-regulated in many breast tumors (34)(35)(36)(37)(38)(39). Although Wnt/β-catenin pathway mutations are rarely detected in breast tumors, elevated levels of nuclear and/or cytoplasmic β-catenin are frequently found and are associated with poor prognosis (40).…”

Association between Wnt inhibitory factor-1 expression levels in articular cartilage and the disease severity of patients with osteoarthritis of the knee

“…Wnt inhibitory factor-1 (WIF-1) is a secreted protein that antagonizes Wnt signaling (7). WIF-1 was initially detected in the human retina and highly conserved homologs have previously been described in various vertebrates (8).…”