Abstract 7176: ROR1-dependent mutant TP53 and cyclin A1 increases, via NRF2 activation, potentially potentiate genomic instability in chronic lymphocytic leukemia cells with del(17p)

Abstract Deletion of 17p (del(17p)) and/or TP53 mutated (p53MU) and/or complex karyotype (CK) are adverse prognostic factors with chemotherapy or targeted therapy that define high-risk chronic lymphocytic leukemia (CLL). Del(17p) causes loss of one allele of TP53. Somatic mutations occur in the other allele of TP53 in about 80% of del(17p) CLL. ROR1 is an embryonic receptor for Wnt5a, which can induce ROR1-signaling leading to activation of ERK1/2, NF-κB and NRF2 target genes in CLL cells. Anti-ROR1 antibody (zilovertamab) therapy, which blocks ROR1-signaling, inhibited expression of such target genes in CLL cells of patients (pts) treated in a phase I study. Prior work also found that pts with CLL cells with high-level ROR1 (ROR1Hi) had an inferior progression-free survival and overall survival compared to pts with CLL cells with low-levels of ROR1 (ROR1Lo). Our gene set enrichment analysis revealed that NRF2 target genes and cell-cycle control genes were significantly enriched in ROR1Hi versus ROR1Lo CLL cells or in pre-treatment CLL cells (D0) versus CLL cells of the same pts treated with zilovertamab (D28). Most pronounced was CCNA1, which encodes cyclin A1 and is transcriptionally activated by wild-type p53 or most p53MU. NRF2 activation can enhance cyclin A1 activation by inducing NRF2 target genes such as NQO1, which can bind p53MU and mitigate its proteasomal degradation. We assessed 493 untreated CLL for ROR1 expression, FISH, and cytogenetics. We found that cases with ROR1Hi CLL had a significantly higher proportion of del(17p) and/or CK than cases with ROR1Lo CLL. This suggests that high-level ROR1-signaling may be conducive to the survival of CLL cells with del(17p) and genomic instability associated with high-level oxidative stress. We examined for this using a CLL-cell line, MEC1, which lacks ROR1 but makes high levels of Wnt5a and has p53MU (Q317fs*29) with del(17p). We also used MEC1Wnt5a-/- cells, in which we deleted WNT5A. MEC1 or MEC1Wnt5a-/- cells were transduced with a lentivirus vector encoding ROR1 to generate MEC1-ROR1 or MEC1-ROR1Wnt5a-/- cells. Relative to MEC1 or MEC1-ROR1Wnt5a-/-, MEC1-ROR1 cells had significantly increased expression of NRF2 target genes and cell-cycle control genes, NQO1, p53MU, and cyclin A1, and increased resistance to drug induced oxidative stress. Similarly, we found that culture of ROR1+ del(17p) CLL cells with Wnt5a increased expression of NQO1, cyclin A1, and p53MU, and enhanced their resistance to drug induced oxidative stress; this effect of Wnt5a could be blocked by concomitant treatment with zilovertamab. As such, inhibiting ROR1-signaling may reduce resistance to oxidative stress and prove selectively deleterious to CLL cells with del(17p) and CK, thereby mitigating their adverse prognostic implications for pts with CLL. Citation Format: Emanuela M. Ghia, Can Huang, Michael Y. Choi, George F. Widhopf, Thomas J. Kipps. ROR1-dependent mutant TP53 and cyclin A1 increases, via NRF2 activation, potentially potentiate genomic instability in chronic lymphocytic leukemia cells with del(17p) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 7176.