X chromosome protects against bladder cancer in females via a KDM6A-dependent epigenetic mechanism

Lysine demethylases KDM6A and UTY: The X and Y of histone demethylation

Histone demethylases remove transcriptional repressive marks from histones in the nucleus. KDM6A (also known as UTX) is a lysine demethylase which acts on the trimethylated lysine at position 27 in histone 3. The KDM6A gene is located on the X chromosome but escapes X inactivation even though it is not located in the pseudoautosomal region. There is a homologue of KDM6A on the Y chromosome, known as UTY. UTY was thought to have lost its demethylase activity and to represent a non-functional remnant of the ancestral KDM6A gene. However, results with knockout mice suggest that the gene is expressed and the protein performs some function within the cell. Female mice with homozygous deletion of Kdm6a do not survive, but hemizygous males are viable, attributed to the presence of the Uty gene. KDM6A is mutated in the human condition Kabuki syndrome type 2 (OMIM 300867) and in many cases of cancer. The amino acid sequence of KDM6A has been conserved across animal phyla, although it is only found on the X chromosome in eutherian mammals. In this review, we reanalyse existing data from various sources (protein sequence comparison, evolutionary genetics, transcription factor binding and gene expression analysis) to determine the function, expression and evolution of KDM6A and UTY and show that UTY has a functional role similar to KDM6A in metabolism and development.

The mouse as a model of fundamental concepts related to Turner syndrome

Although XO mice do not show many of the overt phenotypic features of Turner syndrome (TS; 45,X or XO), mice and humans share different classes of genes on the X chromosome that are more or less likely to cause TS phenotypes. Based on the evolutionary history of the sex chromosomes, and the pattern of dosage balancing among sex chromosomal and autosomal genes in functional gene networks, it is possible to prioritize types of X genes for study as potential causes of features of TS. For example, X-Y gene pairs are among the most interesting because of the convergent effects of X and Y genes that both are likely to prevent the effects of TS in XX and XY individuals. Many of the high-priority genes are shared by mouse and human X chromosomes, but are easier to study in genetically tractable mouse models. Several mouse models, used primarily for the study of sex differences in physiology and disease, also produce XO mice that can be investigated to understand the effects of X monosomy. Using these models will lead to the identification of specific X genes that make a difference when present in one or two copies. These studies will help to achieve a better appreciation of the contribution of these specific X genes to the syndromic features of TS.

The histone demethylase UTX/KDM6A in cancer: Progress and puzzles

The lysine-specific demethylase 6A/UTX (gene name KDM6A) acts as a component of the COMPASS complex to control gene activation. UTX demethylates H3K27me2/3 at genes and enhancers. Deleterious mutations in KDM6A are found in many cancer types, prominently urothelial carcinoma and certain T-cell leukemias. In certain cancers, however, UTX supports oncogenic transcription factors, e.g. steroid hormone receptors in breast and prostate cancer. In fetal development, UTX regulates lineage choice and cell differentiation. Analogously, loss of UTX function in cancer may lead to metaplasia or impede differentiation. Likely because its function is contingent on its interacting transcription factors, the effects of UTX inactivation are not uniform and require detailed investigation in each cancer type. In urothelial carcinoma, in particular, the functional consequences of the frequent mutations in KDM6A and other COMPASS component genes are poorly understood. Nevertheless, UTX inactivation appears to sensitize many cancers to inhibitors of the H3K27 methyltransferase EZH2. Conversely, inhibitors of UTX enzymatic activity may be applicable in cancers with an oncogenic UTX function. Intriguingly, the fact that KDM6A is localized on the X-chromosome, but both copies are expressed, may account for gender-specific differences in cancer susceptibility. In conclusion, despite recent progress, many open questions need to be addressed, most importantly, the detailed mechanisms by which KDM6A inactivation promotes various cancers, but also with which proteins UTX interacts in and apart from the COMPASS complex, and to which extent its catalytic function is required for its tumor-suppressive function.

Immunology, Immunotherapy, and Translating Basic Science into the Clinic for Bladder Cancer

The Fourth Annual Albert Institute Bladder Cancer Care and Research Symposium was held from September 14th–16th in Houston, Texas. The symposium covered a range of topics relevant to bladder cancer, including basic science aspects of immunology and immunotherapy that inform clinical management; intravesical therapy for non-muscle invasive disease; understanding the nuances of carcinoma in situ; and optimizing patient care and outcomes following therapy. The moving landscape of bladder cancer from an industry perspective was also discussed.

In the following sections we discuss intrinsic and extrinsic factors, including the immune microenvironment and sex bias, in the context of bladder cancer; how these influence tumor development, progression, and treatment strategies; and how the interpretation of immune features in relation to molecular subtypes informs both treatment decisions and response. We conclude with a summary of key points that will need to be addressed to ensure best use of new knowledge in this area for improved clinical management of patients with bladder cancer.