en قلب Heart پژوهشي Research <div><strong>Background: </strong>Transcription factors (TFs) play a key role in the development, therapy, and relapse of B-cell malignancies, such as B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Given the essential function of Forkhead box protein P1 (FOXP1) transcription factor in the early development of B-cells, this study was designed to evaluate <em>FOXP1</em> gene expression levels in pediatric BCP-ALL patients and NALM6 cell-line.<br> <strong>Materials and Methods</strong>: This case-control study was done on the NALM6 cell-line and bone marrow specimens of 23 pediatric BCP-ALL patients (median age: 7.5 years; range: 2.0 &ndash; 15.0 years) at different clinical stages including new diagnosis, 15th day after the treatment, and relapse. Also, 10 healthy children were included as the control group. <em>FOXP1</em> gene expression was analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). The correlation analysis was performed between the <em>FOXP1</em> gene expression and patients&rsquo; demographic and laboratory characteristics.<br> <strong>Results: </strong>The results showed that <em>FOXP1</em> gene expression was significantly downregulated in the NALM-6 cell-line (median=0.05, P<0.001) and patients at new diagnosis (median=0.06, p<0.0001), and relapse (median=0.001, p<0.0001) phases, compared to the control group (median=0.08). <em>FOXP1</em> gene expression on the 15^th day of the treatment was significantly higher than its level at the new diagnosis stage (p<0.001). Moreover, <em>FOXP1</em> gene was significantly downregulated in the relapse phase compared to the new diagnosis. Patients whose number of bone marrow blasts on the 15^th day of the treatment was below 5% had higher <em>FOXP1 </em>gene expression at the diagnosis phase (Spearman&rsquo;s correlation, P<0.05, r=-0.485) and higher ratio of diagnosis/day 15 (p<0.001, Mann-Whitney U test).<br> <strong>Conclusions: </strong><em>FOXP1</em> levels could be a potential biomarker of therapy response in remission induction therapy for pediatric BCP-ALL patients<strong>.</strong></div> <span dir="RTL"></span> FOXP1 protein, Neoadjuvant Therapy, Neoplasm, Residual, Precursor B-cell lymphoblastic leukemia 257 265 http://ijpho.ssu.ac.ir/browse.php?a_code=A-10-793-1&slc_lang=en&sid=1 Gholamhossein Tamaddon tamadon@sums.ac.ir 0000-0001-8158-6004 No Diagnostic Laboratory Sciences and Technology Research Center, School of Paramedical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran Diagnostic Laboratory Sciences and Technology Research Center, School of Paramedical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran Mehran Bahraini mehranbahreini70@gmail.com 0000-0001-9735-4830 No Department of Hematology, Faculty of allied medicine, Iran University of Medical Sciences, Tehran, Iran Department of Hematology, Faculty of allied medicine, Iran University of Medical Sciences, Tehran, Iran Alieh Fazeli saharfazeli1373@gmail.com 0000-0003-2311-3473 Yes Diagnostic Laboratory Sciences and Technology Research Center, School of Paramedical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran Diagnostic Laboratory Sciences and Technology Research Center, School of Paramedical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran