Abstract C055: Distinct epigenomic regulation of gene expression in Hispanic/Latino children with high-risk B-cell acute lymphoblastic leukemia

Abstract

Abstract B-Cell Acute Lymphoblastic Leukemia (B-ALL) is the most common childhood malignancy. Hispanic/Latino (H/L) children have a 40% higher death rate than non-Hispanic white (NHW) children after correcting for socioeconomic factors. Recently, we identified a 3.5-fold increased incidence of deletion of one IKZF1 allele (IKZF1-del) and over 15-fold increased incidence of deletion of one IKZF1 allele concomitant with IGH-CRLF2 translocation (IKZF1-del/IGH-CRLF2) in B-ALL of H/L children. This provided a biological rationale for the worse prognosis of B-ALL in H/L children. The very high incidence (29% in all H/L children and 60% in ≥10yr old H/L children) makes IKZF1-del the most frequent genetic alteration that confers adverse prognosis in B-ALL in H/L children. The IKZF1 gene encodes a DNA-binding protein, IKAROS, which regulates transcription of its target genes via chromatin remodeling. The purpose of the study is to analyze the global epigenomic regulation of gene expression in H/L and NHW children with B-ALL and identify biological determinants of altered gene expression that result in worse prognosis for H/L children with B-ALL. /. B-ALL primary cells from 60 H/L and NHW children were analyzed with whole genome sequencing and gene expression profiling using RNA-seq. A subset of B-ALL from each group was analyzed for epigenomic changes by Reduced Representation Bisulfite Sequencing (RRBS), ChIP-seq, CUT&RUN, and CUT&Tag. Results showed that gene expression pattern in B-ALL of H/L children is quite different from B-ALL of NHW children. GSEA and Ingenuity pathway analysis identified oncogenic drivers of B-ALL in H/L children. B-ALL of H/L children have elevated expression of genes that promotestemness, inflammation, and with antiapoptotic activity. RBBS analysis showed a distinct DNA methylation pattern in B-ALL in H/L vs NHW children at promoters of a large set of genes that are involved in cellular signaling, RNA processing, and cellular proliferation. Presence of IKZF1-del results in the alteration of global epigenomic regulation of gene expression with altered enhancer and super-enhancer landscape. Epigenomic alterations due to IKZF1-del resulted in profound redistribution of enhancers and super-enhancers in B-ALL of both H/L vs. NHW children. This was associated with a distinct alteration in gene expression and uncovered that IKAROS regulates different sets of genes in B-ALL in H/L vs. NHW children. These data identified a unique oncogenic signaling that are responsible for aggressive course of B-ALL in H/L children. In conclusion, the multiomics analysis of primary B-ALL cells revealed a distinct global epigenomic regulation of gene expression between B-ALL from H/L and NHW children. This was demonstrated by alterations in DNA methylation and enhancer landscape. Presence of IKZF1-del has a different effect on gene expression in B-ALL of H//L vs NHW children. Results of the study provide a biological rationale for the worse prognosis of B-ALL in H/L children and identified novel therapeutic targets for this disease. Citation Format: Laura Budurlean, Bing He, Yali Ding, Diwakar Bastihalli Tukaramrao, Chingakham Singh, Joseph Schramm, Daniel Bogush, James Broach, Sinisa Dovat. Distinct epigenomic regulation of gene expression in Hispanic/Latino children with high-risk B-cell acute lymphoblastic leukemia [abstract]. In: Proceedings of the 16th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2023 Sep 29-Oct 2;Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2023;32(12 Suppl):Abstract nr C055.