Quantification of <i><scp>HBG</scp></i> m<scp>RNA</scp> in primary erythroid cultures: prediction of the response to hydroxyurea in sickle cell and beta‐thalassemia

<jats:title>Abstract</jats:title><jats:sec><jats:title>Background and Objective</jats:title><jats:p>Increased expression of fetal hemoglobin (<jats:styled-content style="fixed-case">H</jats:styled-content>b<jats:styled-content style="fixed-case">F</jats:styled-content>) may ameliorate the clinical course of hemoglobinopathies like sickle cell disease (<jats:styled-content style="fixed-case">SCD</jats:styled-content>) and β‐thalassemia. Hydroxyurea (<jats:styled-content style="fixed-case">HU</jats:styled-content>) can stimulate <jats:styled-content style="fixed-case">H</jats:styled-content>b<jats:styled-content style="fixed-case">F</jats:styled-content> production in these diseases but the response is highly variable indicating the utility of developing an <jats:italic>in vitro</jats:italic> test to predict the patient's response to <jats:styled-content style="fixed-case">HU</jats:styled-content>. We assessed whether the <jats:styled-content style="fixed-case">H</jats:styled-content>b<jats:styled-content style="fixed-case">F</jats:styled-content> response of patients with <jats:styled-content style="fixed-case">SCD</jats:styled-content> and thalassemia intermedia (<jats:styled-content style="fixed-case">TI</jats:styled-content>) to <jats:styled-content style="fixed-case">HU</jats:styled-content> correlates with <jats:italic><jats:styled-content style="fixed-case">HBG</jats:styled-content></jats:italic> (both γ‐globin genes) expression in their cultured erythroid progenitors following exposure to <jats:styled-content style="fixed-case">HU</jats:styled-content>.</jats:p></jats:sec><jats:sec><jats:title>Patients and Methods</jats:title><jats:p>We exposed primary erythroid cultures from peripheral blood mononuclear cells from 30 patients with <jats:styled-content style="fixed-case">SCD</jats:styled-content> and 15 with <jats:styled-content style="fixed-case">TI</jats:styled-content> to <jats:styled-content style="fixed-case">HU</jats:styled-content> and measured <jats:italic><jats:styled-content style="fixed-case">HBG</jats:styled-content></jats:italic> m<jats:styled-content style="fixed-case">RNA</jats:styled-content> by real‐time quantitative <jats:styled-content style="fixed-case">PCR</jats:styled-content>. The same patients were then treated with <jats:styled-content style="fixed-case">HU</jats:styled-content> and their <jats:styled-content style="fixed-case">H</jats:styled-content>b<jats:styled-content style="fixed-case">F</jats:styled-content> response after treatment with a stable dose of <jats:styled-content style="fixed-case">HU</jats:styled-content> was compared with the m<jats:styled-content style="fixed-case">RNA</jats:styled-content> results in cultured cells.</jats:p></jats:sec><jats:sec><jats:title>Results and Conclusion</jats:title><jats:p>The fold increase in <jats:italic><jats:styled-content style="fixed-case">HBG</jats:styled-content></jats:italic> m<jats:styled-content style="fixed-case">RNA</jats:styled-content> in erythroid progenitors was similar to the fold increase in <jats:styled-content style="fixed-case">H</jats:styled-content>b<jats:styled-content style="fixed-case">F </jats:styled-content><jats:italic>in vivo</jats:italic>. Quantification of <jats:italic><jats:styled-content style="fixed-case">HBG</jats:styled-content></jats:italic> m<jats:styled-content style="fixed-case">RNA</jats:styled-content> in erythroid progenitor cell cultures from patients with <jats:styled-content style="fixed-case">SCD</jats:styled-content> and <jats:styled-content style="fixed-case">TI</jats:styled-content> is predictive of their clinical response to <jats:styled-content style="fixed-case">HU</jats:styled-content>.</jats:p></jats:sec>