gsk343 and Carcinogenesis

Targeting self-renewal and tumorigenicity has been proposed as a potential strategy against cancer stem cells (CSCs). Epigenetic proteins are key modulators of gene expression and cancer development contributing to regulation and maintenance of self-renewal and tumorigenicity. Here, we have screened a small-molecule epigenetic inhibitor library using 3D in vitro models in order to determine potential epigenetic targets associated with self-renewal and tumorigenicity in Canine Mammary Cancer (CMC) cells. We identified inhibition of BET proteins as a promising strategy to inhibit CMC colonies and tumorspheres formation. Low doses of (+)-JQ1 were able to downregulate important genes associated to self-renewal pathways such as WNT, NOTCH, Hedgehog, PI3K/AKT/mTOR, EGF receptor and FGF receptor in CMC tumorspheres. In addition, we observed downregulation of ZEB2, a transcription factor important for the maintenance of self-renewal in canine mammary cancer cells. Furthermore, low doses of (+)-JQ1 were not cytotoxic in CMC cells cultured in 2D in vitro models but induced G2/M cell cycle arrest accompanied by upregulation of G2/M checkpoint-associated genes including BTG2 and CCNG2. Our work indicates the BET inhibition as a new strategy for canine mammary cancers by modulating the self-renewal phenotype in tumorigenic cells such as CSCs.

Topics: Animals; Antineoplastic Agents; Azepines; Biomarkers, Tumor; Carcinogenesis; Cell Proliferation; Dog Diseases; Dogs; Enzyme Inhibitors; Epigenesis, Genetic; Female; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Genetic Testing; Indazoles; Mammary Neoplasms, Animal; Multigene Family; Neoplastic Stem Cells; Pyridones; Transcription Factors; Triazoles

Loss or inactivation of the histone H3K27 demethylase UTX occurs in several malignancies, including multiple myeloma (MM). Using an isogenic cell system, we found that loss of UTX leads to deactivation of gene expression ultimately promoting the proliferation, clonogenicity, adhesion, and tumorigenicity of MM cells. Moreover, UTX mutant cells showed increased in vitro and in vivo sensitivity to inhibition of EZH2, a histone methyltransferase that generates H3K27me3. Such sensitivity was related to a decrease in the levels of IRF4 and c-MYC and an activation of repressors of IRF4 characteristic of germinal center B cells such as BCL6 and IRF1. Rebalance of H3K27me3 levels at specific genes through EZH2 inhibitors may be a therapeutic strategy in MM cases harboring UTX mutations.

Topics: Animals; Carcinogenesis; Cell Adhesion; Cell Dedifferentiation; Cell Line, Tumor; Cell Proliferation; Cell Survival; Clone Cells; Enhancer of Zeste Homolog 2 Protein; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Histone Demethylases; Histones; Indazoles; Interferon Regulatory Factors; Lysine; Methylation; Mice; Mice, Inbred NOD; Mice, SCID; Multiple Myeloma; Mutation; Nuclear Proteins; Phenotype; Pyridones; Transcription, Genetic

Enhancer of zeste 2 (EZH2), a polycomb histone methyltransferase, is overexpressed in various cancers, including cervical cancer. Gene expression analysis revealed that increased expression of EZH2 is associated with cervical cancer progression, particularly the progression to invasive squamous cell carcinoma. Enhancer of zeste 2 is known to trimethylate lysine 27 on histone H3, leading to gene silencing that contributes to the progression of tumours into a more aggressive form of cancer. However, the specific molecular mechanisms by which EZH2 contributes to the development of cervical cancer remain largely unknown. Recently, an EZH2 inhibitor was reported to selectively inhibit trimethylated lysine 27 on histone H3 and to reactivate silenced genes in cancer cells. In this study, we found that GSK343 (a specific inhibitor of EZH2 methyltransferase) induces phenotypic reprogramming of cancer cells from mesenchymal to epithelial cells, reducing proliferation and cell motility and blocking the invasion of cervical cancer cell lines both in vitro and in vivo. Treatment with the EZH2 inhibitor led to increased levels of the epithelial marker E-cadherin and decreased levels of mesenchymal markers such as N-cadherin and vimentin. The observed reprogramming is associated with restrained cervical cancer progression and provides direct evidence in support of EZH2 as a therapeutic target.

Topics: Animals; Cadherins; Carcinogenesis; Cell Movement; Cell Proliferation; Enhancer of Zeste Homolog 2 Protein; Female; Gene Expression Regulation, Neoplastic; HeLa Cells; Humans; Indazoles; Mice; Molecular Targeted Therapy; Neoplasm Invasiveness; Polycomb Repressive Complex 2; Pyridones; Uterine Cervical Neoplasms; Xenograft Model Antitumor Assays