RE-1–silencing transcription factor shows tumor-suppressor functions and negatively regulates the oncogenic TAC1 in breast cancer cells

Abstract

Breast cancer remains the most prevalent cancer among women in the United States. Substance P, a peptide derived from the TAC1 gene, mediates oncogenic properties in breast and other cancers. TAC1 expression facilitates the entry of breast cancer cells into bone marrow. The transcriptional repressor element 1-silencing transcription factor (REST) has been implicated in both oncogenic and tumor-suppressor functions. REST binds to the 5 untranslated region of the TAC1 promoter and suppresses its expression. This study investigated a role for REST in TAC1 induction in breast cancer. Western blots and real-time PCR indicated that REST expression in breast cancer cells was inversely proportional to the cells' aggressiveness, for both cell lines and primary breast cancer cells. REST knockdown in low-metastatic T47D cells and nontumorigenic MCF12A cells resulted in increases in TAC1 induction, proliferation, and migration. These parameters were negatively affected by ectopic expression of REST in highly aggressive MDA-MB-231 cells. Together, these findings show a central role for REST in the oncogenic function of TAC1 and suggest a tumor-suppressor role for REST in breast cancer.REST ͉ substance P ͉ tachykinin D espite advances in diagnostic technologies and treatments, breast cancer (BC) continues to be among the leading causes of cancer-related deaths among women (1). The TAC1 gene has been implicated in the development of breast and other cancers (2-4). TAC1 (preprotachykinin-A) is a single-copy gene with 7 exons (5). Through alternative splicing and posttranslational modification, TAC1 produces peptides belonging to the tachykinin family (5-7). Substance P (SP) is the predominant peptide produced from TAC1 (8, 9).BC cells (BCCs) produce high levels of SP (6). SP binds with varying affinities to 3 G protein-coupled, 7-transmembrane receptors: neurokinin (NK)1, NK2, and NK3 (6, 10). NK1 and NK2 have been reported on BCCs. SP mediates BCC proliferation, imparts radiation resistance, protects from apoptosis, induces growth-and angiogenic-promoting factors, and facilitates BC metastasis to bone marrow (2,4,11,12). The truncated NK1 has also been linked to oncogenesis, partly through the induction of TAC1 (2).Stromal-derived factor-1␣, which is implicated in BC biology, regulates TAC1 expression (4, 13). Other cytokines also induce TAC1 expression in BCCs via autocrine stimulation (2, 14). RE-1 silencer of transcription (REST) represses TAC1 expression in mesenchymal stem cells (15). The link between REST and TAC1 could be relevant to disorders such as tumorigenesis and hippocampal seizure (16).REST, also known as neural restrictive silencing factor, is a zinc finger transcriptional repressor of neuronal genes in nonneuronal and immature neuronal cells (17). REST facilitates chromatin remodeling and inhibits gene expression by assembling a repressor complex (18), Sin3A/histone deacetylase, and co-REST at the N and C termini, respectively (18). REST has been implicated in both oncogenic and tumor-suppressor roles (19,20)....

Regulation of the NRSF/REST gene by methylation and CREB affects the cellular phenotype of small-cell lung cancer

“…Although in breast cancer the TAC1 gene coding for substance P was identified as a NRSF/REST target gene (Reddy et al, 2009), we could identify AKT2 important for cell proliferation and survival as a target of NRSF/ REST in SCLC. An siRNA-mediated knockdown of NRSF/REST expression in H128 enhanced transcription of the AKT2 and synaptophysin genes in H128.…”

Transformation by E1A Oncoprotein Involves Ubiquitin-Mediated Proteolysis of the Neuronal and Tumor Repressor REST in the Nucleus

“…In accordance with this, loss of REST function has been implicated in several human cancers, including breast, prostate, ovarian, colorectal, pancreatic, and small-cell lung cancers (1,6,9,15,19,35,51,56). In breast cancer cells, REST has been found to repress the oncogenic TAC1 gene, as well as cell proliferation and migration (39). These findings indicate that REST plays a pivotal role in suppressing cancer formation and may represent a potential therapeutic target of some human cancers.…”

REST (RE1-silencing transcription factor)

“…It was recently shown that, together with NFkB, REST represses TAC1 expression in mesenchymal stem cells. However, the level of REST decreases in breast cancer cells and inversely correlates with substance P production and an aggressive cellular phenotype (Reddy et al, 2009). …”