DRP1 Inhibition Enhances Venetoclax-Induced Mitochondrial Apoptosis in TP53-Mutated Acute Myeloid Leukemia Cells through BAX/BAK Activation

SOHO State of the Art Updates and Next Questions: Understanding and Overcoming Venetoclax Resistance in Hematologic Malignancies

The discovery of Venetoclax (VEN) has transformed the therapeutic landscape of acute myeloid leukemia (AML) and chronic lymphocytic leukemia (CLL). However, the response is heterogeneous with 10% to 50% of newly diagnosed AML patients not responding to hypomethylating agent (HMA) and VEN. Furthermore, up to 40% of responding patients relapse shortly. This review discusses the mechanism of action of Venetoclax and the major mechanisms of inherent and acquired resistance to VEN. VEN is highly specific to BCL-2 binding, as such other antiapoptotic proteins in BCL-2 family induce resistance. These antiapoptotic proteins can also be upregulated via a number of compensatory cell signaling pathways including PI3K/AKT/mTOR, the MAPK/ERK pathway, and mutant FLT3-ITD. Mutations can occur in BCL-2 and BAX proteins, or they can be silenced by TP53 mutations and other epigenetic changes. Changes to mitochondrial structure and metabolism can induce resistance. Key metabolic regulators include OXPHOS and alternative amino acid metabolism. Finally microenvironmental factors can influence VEN responses. This paper evaluates subsets of AML by differentiation, histology, cytogenetics and molecular markers and their different responses to VEN; with spliceosome mutations, ASXL1, NPM1 and IDH1/2 being favorable while others such as FLT3, TP53 and BCL-2 mutations being less responsive. Currently intensive multiagent chemotherapy and Venetoclax combinations such as 7+3+VEN are favored in fit younger AML patients. However, with resistant patients' subsets targeted combination therapies are becoming an increasingly attractive option. We explore the incorporation of non-BCL-2 inhibitors, next-generation BCL-2 and multi-protein agents, other inhibitors most prominently FLT-3 inhibitors in addition to Venetoclax, and other novel approaches for resolving Venetoclax resistance.

Prognostic value and immune regulatory role of dynamin 1-like in lung adenocarcinoma

Background

Lung adenocarcinoma (LUAD) is the most common histological subtype of non-small cell lung cancer (NSCLC), with poor treatment outcomes worldwide. Dynamin-related protein 1 (DRP1), which is encoded by the dynamin 1-like (DNM1L) gene, acts as a regulator of mitochondrial fission and plays crucial roles in tumor initiation and progression. However, the clinical value and immune regulation of DNM1L in LUAD have not been explored.

Methods

We comprehensively analyzed the expression of DNM1L in the LUAD cohort of the Human Protein Atlas (HPA) and the University of The ALabama at Birmingham CANcer data analysis Portal (UALCAN) databases. Kaplan-Meier plotter, in addition to the PrognoScan database, was used to estimate the correlation between DNM1L expression and survival outcome of LUAD patients. The association between the immune tumor microenvironment (TME) and DNM1L expression in LUAD was evaluated based on the Tumor IMmune Estimation Resource (TIMER)2.0 database. Finally, the functions of DNM1L were validated in vitro experiments, including reverse transcription-quantitative polymerase chain reaction (RT-qPCR), western blot, wound healing assays, and transwell assays.

Results

DNM1L was overexpressed in LUAD compared to healthy control tissues and was regarded as an independent prognostic factor. Overexpression of DNM1L was significantly related to clinical variables and poor survival outcomes of LUAD patients. Moreover, DNM1L expression was positively associated with the expression of key genes involved in the regulation of immune cell subsets, including T helper (Th)2 cells, Th cells, B cells, CD8 T cells, dendritic cells, and mast cells. In contrast, DNM1L was negatively correlated with the infiltrating levels of myeloid dendritic cells and B cells. Furthermore, DNM1L may play a role in regulating immune cell infiltration and have prognostic value in LUAD patients. Finally, the in vitro experiments showed that increased DNM1L significantly promoted the proliferation and migration of LUAD cells.

Conclusions

This study suggested that DNM1L may play an important role in regulating the proliferation and migration of LUAD cells as well as the infiltration of tumor-related immune cells, which suggests DNM1L was a potential therapeutic target in LUAD. Further studies are however warranted to define its exact mechanism of action and potential therapeutic significance in LUAD patients.