PHF6 functions as a tumor suppressor by recruiting methyltransferase SUV39H1 to nucleolar region and offers a novel therapeutic target for PHF6-muntant leukemia

Small molecules targeting selected histone methyltransferases (HMTs) for cancer treatment: Current progress and novel strategies

Histone methyltransferases (HMTs) play a critical role in gene post-translational regulation and diverse physiological processes, and are implicated in a plethora of human diseases, especially cancer. Increasing evidences demonstrate that HMTs may serve as a potential therapeutic target for cancer treatment. Thus, the development of HMTs inhibitor have been pursued with steadily increasing interest over the past decade. However, the disadvantages such as insufficient clinical efficacy, moderate selectivity, and propensity for acquired resistance have hindered the development of conventional HMT inhibitors. New technologies and methods are imperative to enhance the anticancer activity of HMT inhibitors. In this review, we first review the structure and biological functions of the several essential HMTs, such as EZH2, G9a, PRMT5, and DOT1L. The internal relationship between these HMTs and cancer is also expounded. Next, we mainly focus on the latest progress in the development of HMT modulators encompassing dual-target inhibitors, targeted protein degraders and covalent inhibitors from perspectives such as rational design, pharmacodynamics, pharmacokinetics, and clinical status. Lastly, we also discuss the challenges and future directions for HMT-based drug discovery for cancer therapy.

PHF6-altered T-ALL Harbor Epigenetic Repressive Switch at Bivalent Promoters and Respond to 5-Azacitidine and Venetoclax

PURPOSE

To assess the impact of PHF6 alterations on clinical outcome and therapeutical actionability in T-cell acute lymphoblastic leukemia (T-ALL).

EXPERIMENTAL DESIGN

We described PHF6 alterations in an adult cohort of T-ALL from the French trial Group for Research on Adult Acute Lymphoblastic Leukemia (GRAALL)-2003/2005 and retrospectively analyzed clinical outcomes between PHF6-altered (PHF6ALT) and wild-type patients. We also used EPIC and chromatin immunoprecipitation sequencing data of patient samples to analyze the epigenetic landscape of PHF6ALT T-ALLs. We consecutively evaluated 5-azacitidine efficacy, alone or combined with venetoclax, in PHF6ALT T-ALL.

RESULTS

We show that PHF6 alterations account for 47% of cases in our cohort and demonstrate that PHF6ALT T-ALL presented significantly better clinical outcomes. Integrative analysis of DNA methylation and histone marks shows that PHF6ALT are characterized by DNA hypermethylation and H3K27me3 loss at promoters physiologically bivalent in thymocytes. Using patient-derived xenografts, we show that PHF6ALT T-ALL respond to the 5-azacytidine alone. Finally, synergism with the BCL2-inhibitor venetoclax was demonstrated in refractory/relapsing (R/R) PHF6ALT T-ALL using fresh samples. Importantly, we report three cases of R/R PHF6ALT patients who were successfully treated with this combination.

CONCLUSIONS

Overall, our study supports the use of PHF6 alterations as a biomarker of sensitivity to 5-azacytidine and venetoclax combination in R/R T-ALL.

Targeted Epigenetic Interventions in Cancer with an Emphasis on Pediatric Malignancies

Over the past two decades, novel hallmarks of cancer have been described, including the altered epigenetic landscape of malignant diseases. In addition to the methylation and hyd-roxymethylation of DNA, numerous novel forms of histone modifications and nucleosome remodeling have been discovered, giving rise to a wide variety of targeted therapeutic interventions. DNA hypomethylating drugs, histone deacetylase inhibitors and agents targeting histone methylation machinery are of distinguished clinical significance. The major focus of this review is placed on targeted epigenetic interventions in the most common pediatric malignancies, including acute leukemias, brain and kidney tumors, neuroblastoma and soft tissue sarcomas. Upcoming novel challenges include specificity and potential undesirable side effects. Different epigenetic patterns of pediatric and adult cancers should be noted. Biological significance of epigenetic alterations highly depends on the tissue microenvironment and widespread interactions. An individualized treatment approach requires detailed genetic, epigenetic and metabolomic evaluation of cancer. Advances in molecular technologies and clinical translation may contribute to the development of novel pediatric anticancer treatment strategies, aiming for improved survival and better patient quality of life.