الفهرس 
Pediatric Acute Lymphoblastic LeukemiaOnly 14 pages are availabe for public view
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Abstract
leukemia has a high mortality rates throughout the globe (Bernard et al., 2017). ALL is the most common type of pediatric leukemia in children (Smith et al., 2014; Bhatia et al., 2015). It represents the 11th and 10th most frequent cause of cancer occurrence and death worldwide; respectively (Miranda-Filho et al., 2018). The role of different T-lymphocyte subsets in cancer development and progression are currently of great interest (Marshall et al., 2016).
CD4+ T cells differentiate into several subsets including; Th1, Th2, Th17, Treg, Th9 and Th22 (Knochelmann et al., 2018). Treg/Th17 balance is essential for maintaining homeostasis of antitumor immunity (Zou and Restifo, 2010). Recently, it is widely accepted that alteration in the balance between Treg and Th17 cells is associated with several types of cancers (Luo et al., 2017). Tregs are correlated with cancer progression while Th17 cells have been implicated in carcinogenesis. (Knochelmann et al., 2018). The differentiation of Treg and Th17 cells is controlled by a combination of their cytokine milieu, transcriptional activities, and genetic control (Luo et al., 2017).
Several miRNAs were determined to be key molecules in modulating immune cell development and differentiation (Yao et al., 2011). On the other hand, miRNA expression profile reported to be related to the formation and progression of various cancers (Takasaki, 2016). miR-155 and miR-21 were reported to be positive and negative regulators of Tregs cells; respectively (Li et al., 2015). miR-26a could inhibit Th17 differentiation and promote the development and function of Treg cells (Liu et al., 2018). Moreover, Jin et al. (2018) documented that miR-148a might be a promoter for Treg and miR-133b was demonstrated as novel biomarkers for Th17-type immune reaction (Haas et al., 2011). In addition, miR-24 expression was recorded to promote response of Th17 (Cho et al. (2017)
FOXP3, the master transcriptional activator and the most specific marker for Tregs, is important for Tregs development and maintenance of function (Fontenot et al., 2003; Feng et al., 2014). SNPs in the FOXP3 gene might change its expression level and impair the suppressive function of Tregs (Cheng et al., 2018). RORγ encode RORγt, the master transcription factor expressed by Th17 cells (Ivanov et al., 2006). The promoter region of ROR-γ was identified to have several elements crucial for the activity of the promoter and the expression of the gene in Th17 (Ratajewski et al., 2016).
In the light of the vital role of Treg and Th17 cells in cancer, the current study was performed to investigate Tregs percentage and the role of cytokine/miRNA in regulating Treg/Th17 balance in pediatric ALL. Also, to investigating the genetic association between FOXP3 (-3279C/A and -2383C/T) and ROR-γ (rs9017A/G & rs9826A/G) gene polymorphism and susceptibility to ALL in the Egyptian children and their potential role in regulating both cells.
The frequency of Treg was assessed by flow cytometry in 43 ALL patients versus 42 controls. Plasma levels of Treg- (IL-10 and TGF-β) and Th17- (IL-6, IL-17, IL-23 and TNF-α) related cytokines were measured by ELISA. miR-21, miR-24, miR-26a, miR133b, miR-148a and miR-155 expression were analyzed using qRT-PCR. Genotyping of FOXP3 (-3279C/A & -2383C/T) were performed by PCR-RFLP, while ROR-γ (rs9017A/G & rs9826A/G) polymorphism was performed by PCR-SSP.
A slight increase in Treg cells coincides with a decrease in IL-17 levels in ALL patients compared to controls was observed. There was a significant elevation in IL-10 (p<0.05), IL-6 (p<0.01), IL-23 (p<0.05) and TNF-α (p<0.01) in ALL patients compared with normal controls. Meanwhile, a significant reduction in TGF-β (p<0.001) was recorded. ALL patients showed a significant increase in miR-21 (p<0.05), miR-148a (p<0.01), miR-24 (p<0.05) and significant decrease in miR-155 (p<0.01). Relapsed ALL patients showed a significant (p<0.01) up-regulation in miR-24 expression levels compared to the non-relapsed group Thus the insignificant increase of Tregs in the view
of cytokine and miRNAs might refer to reduction of Th17 cells which in favor to ALL progress.
Concerning SNPs in the transcription factors of both cells, there was a significant increase (p<0.01) in FOXP3 -3279CC genotype, while FOXP3 -3279CA genotype was significantly decreased in ALL patients compared to controls. A significant increase (p<0.001) in ROR-γ rs9826AA genotype with a significant reduction (p<0.01) in ROR-γ rs9826AG genotype was observed in the patients group compared to the control group. Concerning Treg and Th17 cells, Insignificant change in FOXP3 (-2383C/T) or (-3279C/A) in Tregs percentage or related cytokines only rs9017AG and rs9826GG genotypes affect significantly IL-23 expression.
Taken together, the analysis of the current study results revealed that ALL has a corruption in pathways responsible for fully activated Treg cells which might be related to cytokines and miRNA in the surrounded microenvironment. This pilot study pointed to the potential role of FOXP3 (-3279C/A) and ROR-γ (rs9017A/G) gene polymorphisms in the susceptibility ALL in Egyptian children. Concerning correlation between selected SNPs in FOXP3/ROR-γ; results did not detect any significant correlation between both SNPs and Treg/IL-17 secretion. An additional prospective large scale study should be carried out to support these findings.