HDAC/NAMPT dual inhibitors overcome initial drug-resistance in p53-null leukemia cells

Area of Science:

• Biochemistry
• Epigenetics
• Cancer Biology

Background:

• Cancer development is linked to metabolic and epigenetic dysregulation.
• Histone deacetylases (HDACs) are key epigenetic regulators of gene expression.
• Nicotinamide phosphoribosyltransferase (NAMPT) is crucial for cellular metabolism and NAD+ biosynthesis.

Purpose of the Study:

• To design and synthesize novel dual inhibitors targeting both HDAC and NAMPT.
• To evaluate the efficacy and specificity of these dual inhibitors against leukemia.
• To investigate their potential to overcome resistance mechanisms in p53-null acute myeloid leukemia (AML).

Main Methods:

• Rational drug design based on structural similarities between HDAC and NAMPT inhibitors.
• In vitro biochemical assays to determine inhibitory activity (IC50 values) against HDACs and NAMPT.
• Cell-based assays to assess anti-proliferative activity and apoptosis induction in leukemia cell lines.
• Kinase panel screening to evaluate target specificity.

Main Results:

• Compounds 39a and 39h demonstrated potent and selective inhibition of HDAC1-3 (IC50: 0.71-25.1 nM) with modest NAMPT inhibition.
• Compound 39h showed high specificity, lacking activity against 370 kinases.
• Both compounds exhibited low nanomolar anti-proliferative activity in leukemia cells.
• Dual inhibitors 39a and 39h effectively overcame resistance in p53-null AML cell lines, inducing apoptosis.
• Nicotinamide mononucleotide (NMN) reversed the cell death, confirming inhibition of the NAD+ biosynthesis pathway and HDAC.

Conclusions:

• Novel HDAC/NAMPT dual inhibitors offer a promising therapeutic strategy for leukemia, particularly p53-null AML.
• These compounds effectively target both epigenetic regulation and cellular metabolism.
• The dual inhibition mechanism overcomes resistance associated with single-target inhibitors.
• This approach presents a viable strategy to address limitations of current HDAC inhibitors in treating specific leukemia subtypes.