Lack of hydroxyurea‐associated mutagenesis in pediatric sickle cell disease patients

Abstract

Hydroxyurea is approved for treating children and adults with sickle cell anemia (SCA). Despite its proven efficacy, concerns remain about its mutagenic and carcinogenic potential that hamper its widespread use. Cell culture-and animal-based investigations indicate that hydroxyurea's genotoxic effects are due to indirect clastogenicity in select cell types when high dose and time thresholds are exceeded (reviewed by Ware & Dertinger, 2021). The current study extends these preclinical observations to pediatric patients receiving hydroxyurea for treatment of SCA. First, proof-of-principle experiments with testicular cancer patients exposed to a cisplatinbased regimen validated the ability of flow cytometric blood-based micronucleated reticulocyte (MN-RET) and PIG-A mutant reticulocyte (MUT RET) assays to detect clastogenicity and gene mutations, respectively. Second, these biomarkers were measured in a cross-sectional study with 26 SCA patients receiving hydroxyurea and 13 SCA patients without exposure. Finally, a prospective study was conducted with 10 SCA patients using pretreatment blood samples and after 6 or 12 months of therapy. Cancer patients exposed to cisplatin exhibited increased MN-RET within days of exposure, while the MUT RET endpoint required more time to reach maximal levels.In SCA patients, hydroxyurea induced MN-RET in both the cross-sectional and prospective studies. However, no evidence of PIG-A gene mutation was found in hydroxyurea-treated children, despite the fact that the two assays use the same rapidly-dividing, highly-exposed cell type. Collectively, these results reinforce the complementary nature of MN-RET and MUT RET biomarkers, and indicate that hydroxyurea can be clastogenic but was not mutagenic in young patients with SCA.

Erythrocyte PIG‐A mutant frequencies in cancer patients receiving cisplatin

“…In one patient, DW012, neither RET nor total RBC PIG‐A MF increased over the study period. Similar modest increases in PIG‐A MF were observed in a small group of testicular cancer patients receiving cisplatin‐containing chemotherapy 30 . However, the chemotherapy regimen in the testicular cancer study was different than in our HNC study.…”

Review on Hydroxyurea Usage in Young Children with Sickle Cell Disease: Examining Hemoglobin Induction, Potential Benefits, Responses, Safety, and Effectiveness

“…They help create loops between the locus control region (LCR) and individual globin promoters. This looping is crucial for regulating the transcription of globin genes and ensuring their proper expression [15].…”

“…One such factor, BCL11A, binds to the HBG promoters or the HBD/HBB intergenic region. BCL11A has emerged as a promising target for drug interventions that aim to increase HbF production effectively [15].…”

The PIG‐A gene mutation assay in human biomonitoring and disease

“…Another study identified only 1/10 patients undergoing chemotherapy had a notable (three‐fold) increase in erythrocyte PIG‐A mutant cell levels (Dobrovolsky et al, 2011). Reticulocyte PIG‐A mutant cell levels have been shown to increase in testicular cancer patients ( n = 3) after cisplatin‐based treatment, but it took longer to observe PIG‐A mutant reticulocytes compared to micronucleated reticulocytes (Torous et al, 2023). Although we would expect systemic genotoxic agents such as chemotherapy to increase mutant levels, the time between treatment and mutant manifestation is critical.…”

“…This short time frame of opportunity may also be the case for the COMET assay. Together with the mechanistic differences of these endpoints and the differences in fate of the mutated cells proves the need for the combination of complementary assays to comprehensively recognize genotoxic exposures (Torous et al, 2023). F I G U R E 5 phosphatidylinositol glycan class A (PIG-A) mutant frequency and lymphocyte micronucleus levels for 141 individuals (R = .2124, p = .0114).…”