Upregulated heme biosynthesis, an exploitable vulnerability in MYCN-driven leukemogenesis. Mus musculus

The increased heme biosynthesis long observed in leukemia was previously of unknown significance. Heme, synthesized from porphyrin precursors, plays a central role in oxygen metabolism and mitochondrial function, yet little is known about its role in leukemogenesis. Here we show increased expression of heme biosynthetic genes, including UROD, only in pediatric AML with high MYCN expression. Both high UROD and MYCN expression predict poor overall survival and unfavorable outcomes in adult AML. Murine leukemic progenitors derived from hematopoietic progenitor cells (HPCs) overexpressing a MYCN cDNA (MYCN-HPC) require heme/porphyrin biosynthesis, accompanied by increased oxygen consumption, to fully engage in self-renewal and oncogenic transformation. Blocking heme biosynthesis reduced mitochondrial oxygen consumption and markedly suppressed self-renewal. Leukemic progenitors rely on balanced production of heme and heme intermediates, the porphyrins. Porphyrin homeostasis is required because absence of the porphyrin exporter, ABCG2, increased death of leukemic progenitors in vitro and prolonged the survival of mice transplanted with Abcg2-KO MYCN HPCs. Pediatric AML patients with elevated MYCN mRNA display strong activation of TP53 target genes. Abcg2-KO MYCN HPCs were rescued from porphyrin toxicity by p53 loss. This vulnerability was exploited to show that treatment with a porphyrin precursor, coupled with the absence of ABCG2, blocked MYCN-driven leukemogenesis in vivo thereby demonstrating, that porphyrin homeostasis is a pathway crucial to MYCN leukemogenesis. We used microarrays to compare the global transcription profiles of hematopoietic progenitor cells from wild-type and Abcg2-ko mice that after transduction with vector-alone or vector containing MYCN gene. Overall design: We analyzed a total of 8 samples; duplicates of hematopoietic progenitors in the following conditions: WT + Vector, WT + MYCN, Abcg2-ko + Vector, Abcg2-ko + MYCN