Histone Modifications Drive Aberrant Notch3 Expression/Activity and Growth in T-ALL

Area of Science:

• Molecular Biology
• Cancer Research
• Epigenetics

Background:

• T-cell acute lymphoblastic leukemia (T-ALL) is driven by dysregulated T-cell development pathways, notably Notch signaling.
• Aberrant Notch signaling in T-ALL involves NOTCH1 gain-of-function mutations and NOTCH3 overexpression.
• The transcriptional regulation of NOTCH3 in T-ALL subsets lacking Notch1 activation remains unclear.

Purpose of the Study:

• To elucidate the transcriptional machinery controlling NOTCH3 expression in T-ALL.
• To investigate the role of JMJD3 and p300 in Notch signaling-driven T-ALL.
• To evaluate the therapeutic potential of inhibiting JMJD3 and p300 in T-ALL.

Main Methods:

• Analysis of Notch1 and Notch3 intracellular domain binding to the NOTCH3 gene locus.
• Assessment of JMJD3 and p300 recruitment and their impact on H3K27 marks.
• Pharmacological inhibition of JMJD3 (GSKJ4) and p300 (A-485) in T-ALL cell models.
• Evaluation of cell viability and gene expression changes (NOTCH3, NOTCH1, DELTEX1, c-Myc) following inhibition.
• Rescue experiments with re-introduction of Notch1, Notch3, or c-Myc.

Main Results:

• Notch1 and Notch3 binding to the NOTCH3 locus recruits JMJD3 and p300, preserving active H3K27 marks and sustaining NOTCH3 expression.
• Inhibition of JMJD3 or p300 significantly decreased NOTCH3, NOTCH1, DELTEX1, and c-Myc expression and abrogated T-ALL cell viability.
• Exogenous Notch1, Notch3, or c-Myc partially rescued cells from the anti-growth effects of JMJD3/p300 inhibition.

Conclusions:

• JMJD3 and p300 function as general co-activators for both Notch1 and Notch3 signaling in T-ALL.
• Targeting JMJD3 and p300 enzymatic activity demonstrates anti-leukemic effects in T-ALL.
• These findings suggest therapeutic potential for JMJD3 and p300 inhibition in Notch/c-Myc axis-related cancers.