Loss of p53 enhances the tumor-initiating potential and drug resistance of clonogenic multiple myeloma cells

Abstract

Tumor relapse and drug resistance are major factors that limit the curability of multiple myeloma (MM). New regimens have improved overall MM survival rates, but patients with high-risk features continue to have inferior outcomes. Chromosome 17p13 deletion (del17p) which includes the loss of the TP53 gene is a high-risk cytogenetic abnormality and is associated with poor clinical outcomes due to relatively short remissions and the development of pan-drug resistant disease. Increased relapse rates suggest that del17p enhances clonogenic growth, and we found that the loss of p53 increased both the frequency and drug resistance of tumor-initiating MM cells (TICs). Subsequent RNA sequencing (RNA-seq) studies demonstrated significant activation of the Notch signaling pathway and upregulation of inhibitor of DNA binding (ID1/ID2) genes in p53-knock out (p53-KO) cells. We found that the loss of ID1 or HES-1 expression or treatment with a gamma-secretase inhibitor (GSI) significantly decreased the clonogenic growth of p53-KO, but not p53 wild-type cells. GSI treatment in a small set of MM specimens also reduced the clonogenic growth in del17p samples but not in non-del17p samples. This effect was specific as overexpression of the Notch intracellular domain (NICD) rescued the effects of GSI treatment. Our study demonstrates that the Notch signaling and ID1 expression are required for TIC expansion in p53-KO MM cells. These findings also suggest that GSI may be specifically active in patients with p53 mutant MM.

Novel Anti-B-cell Maturation Antigen Alpha-Amanitin Antibody-drug Conjugate HDP-101 Shows Superior Activity to Belantamab Mafodotin and Enhanced Efficacy in Deletion 17p Myeloma Models

“…This ability to impact both committed plasma cells and their precursors may in part underlie the ability of HDP-101 to eradicate myeloma in in vivo models, including those with del17p, and to show greater efficacy than BelaMaf pre-clinically. It is interesting in this regard to note that one recent study described TP53 loss as contributing to the tumor-initiating and drug resistance potential of clonogenic myeloma cells through activation of the Notch signaling pathway and upregulation of inhibitor of DNA binding (ID1/ID2) genes ( 43 ).…”