Targeting the Myeloid Lineages and the Immune Microenvironment in Myelodysplastic Syndromes: Novel and Evolving Therapeutic Strategies

A Promising Future for Precision Epigenetic Therapy for Follicular and Diffuse Large B-Cell Lymphoma?

Epigenetic mechanisms such as DNA hypermethylation or histone deacetylation normally silence gene expression that regulates numerous cellular activities. Germinal center–derived lymphomas such as follicular lymphoma (FL) and diffuse large B cell lymphoma (DLBCL) are characterized by frequent mutations of histone-modifying genes. EZH2 is essential to the formation of germinal center in the secondary lymphoid tissue (eg, lymph nodes and spleen) and is one of the most frequently mutated histone-modifying genes in human lymphomas. EZH2 encodes a histone methyltransferase, mediates transcriptional repression and acts as an oncogene that promotes the development and progression of a variety of human malignancies, including FL and DLBCL. Thus, recurrent mutations in the EZH2 and other non-histone epigenetic regulators represent important targets for therapeutic interventions. Recently, an orally active inhibitor of EZH2, tazemetostat, has received regulatory approval for patients with mutated EZH2 relapsed or refractory FL after ≥2 prior systemic therapies. It is also approved for those with relapsed or refractory FL who have no satisfactory alternative treatment options, regardless of their mutational status of EZH2. Currently, tazemetostat and its combination therapies for patients with relapsed or refractory germinal center-derived lymphomas, as well as frontline therapies for previously untreated patients, are in various phases of clinical investigations. Despite the promise of epigenetic therapies, potential pitfalls such as target selectivity, risk of oncogenic activation, risk of secondary malignancies associated with epigenetic therapies must be carefully monitored. Future applications of epigenetic approach that incorporate clinical and genomic features are needed to determine how individualized treatments can be used for these hematologic malignancies.