Tumor suppressor SET9 guides the epigenetic plasticity of breast cancer cells and serves as an early-stage biomarker for predicting metastasis.

During the course of cancer progression, neoplastic cells undergo dynamic and reversible transitions between multiple phenotypic states, and this plasticity is enabled by underlying shifts in epigenetic regulation. Our results identified a negative feedback loop in which SET9 controls DNA methyltransferase-1 protein stability, which represses the transcriptional activity of the SET9 promoter in coordination with Snail. The modulation of SET9 expression in breast cancer cells revealed a connection with E2F1 and the silencing of SET9 was sufficient to complete an epigenetic program that favored epithelial-mesenchymal transition and the generation of cancer stem cells, indicating that SET9 plays a role in modulating breast cancer metastasis. SET9 expression levels were significantly higher in samples from patients with pathological complete remission than in samples from patients with disease recurrence, which indicates that SET9 acts as a tumor suppressor in breast cancer and that its expression may serve as a prognostic marker for malignancy.

Targeting the epigenetics of the DNA damage response in breast cancer.

Cancer is as much an epigenetic disease as it is a genetic disease, and epigenetic alterations in cancer often serve as potent surrogates for genetic mutations. Because the epigenetic factors involved in the DNA damage response are regulated by multiple elements, therapies to target specific components of the epigenetic machinery can be inefficient. In contrast, therapies aimed at inhibiting the methionine cycle can indirectly inhibit both DNA and protein methylation, and the wide variety of genes and pathways that are affected by these methylations make this global strategy very attractive. In the present study, we propose an adjuvant therapy that targets the epigenetics of the DNA damage response in breast cancer cells and that results in efficient apoptosis and a reduction in distant metastases in vivo. We observed that a combined therapy designed to uncouple adenosine metabolism using dipyridamole in the presence of a new synthetic antifolate, 3-O-(3,4,5-trimethoxybenzoyl)-(-)-catechin, simultaneously and efficiently blocked both the folic cycle and the methionine cycle in breast cancer cells and sensitized these cells to radiotherapy. The treatment impeded the recruitment of 53BP1 and BRCA1 to the chromatin regions flanking DNA double-strand breaks and thereby avoided the DNA damage responses in breast cancer cells that were exposed to ionizing radiation. In addition, this hypomethylating therapy was also efficient in reducing the self-renewal capability of breast cancer-initiating cells and induced reversion of mesenchymal phenotypes in breast cancer cells.

Targeting the epigenetic machinery of cancer cells.

Cancer is characterized by uncontrolled cell growth and the acquisition of metastatic properties. In most cases, the activation of oncogenes and/or deactivation of tumour suppressor genes lead to uncontrolled cell cycle progression and inactivation of apoptotic mechanisms. Although the underlying mechanisms of carcinogenesis remain unknown, increasing evidence links aberrant regulation of methylation to tumourigenesis. In addition to the methylation of DNA and histones, methylation of nonhistone proteins, such as transcription factors, is also implicated in the biology and development of cancer. Because the metabolic cycling of methionine is a key pathway for many of these methylating reactions, strategies to target the epigenetic machinery of cancer cells could result in novel and efficient anticancer therapies. The application of these new epigenetic therapies could be of utility in the promotion of E2F1-dependent apoptosis in cancer cells, in avoiding metastatic pathways and/or in sensitizing tumour cells to radiotherapy.

The anti-inflammatory and anti-cancer properties of epigallocatechin-3-gallate are mediated by folate cycle disruption, adenosine release and NF-kappaB suppression.

OBJECTIVE: To understand the mechanism by which (-)-epigallocatechin-3-gallate (EGCG), the major polyphenol of green tea, exerts its anti-inflammatory action. METHODS: To check our hypothesis that the anti-inflammatory properties of EGCG could be related to its antifolate action and whether adenosine and its receptors are involved in EGCG action, we investigated the EGCG-induced suppression of NF-kappaB in Caco-2 cell monolayer, which acted as a model of the human intestinal epithelium. RESULTS: We demonstrate that the anti-inflammatory properties of EGCG are associated with its antifolate activity. By using a natural stable folate we were able to reverse the EGCG suppression of TNF-alpha-induced NF-kappaB activation, the phosphorylation and degradation of IkappaBalpha and the phosphorylation of Akt in this human colon carcinoma cell line. These suppressions were mediated by the release of adenosine following disruption of the folate cycle by EGCG. By binding to its specific receptors, adenosine can modulate the Akt and NF-kappaB pathway. Moreover, EGCG produces a significant increase in a specific adenosine receptor, which could explain the suppression of the constitutive activation of NF-kappaB in colon cancer cells. CONCLUSIONS: The data suggest that by modulating NF-kappaB activation, EGCG might not only combat inflammation, but also cancer.

Muscular dystrophy with laminin deficiency decreases acetylcholinesterase activity in thymus of dystrophic Lama2dy mice.

We have studied the effect of muscular dystrophy by merosin deficiency on mouse thymus acetyl- (AChE) and butyrylcholinesterase (BuChE). The organ contains AChE and BuChE activities. Merosin deficiency causes an important decrease (46%) in AChE specific activity. Thymus produces dimers, monomers and tetramers of AChE, and the three kinds of AChE mRNAs. The drop in AChE activity in dystrophic animals could affect the amount of ACh reaching cholinergic receptors in cells of lymphoid organs.