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Multidrug resistance (MDR) is considered as the major obstacle for treating pediatric acute lymphoblastic leukemia (ALL). MicroRNAs (miRNAs) are small non coding RNAs which may potentially regulate response to chemotherapy. In this study, total RNA was isolated from bone marrow samples of 46 children with de novo ALL and 16 controls. Quantitative reverse transcriptase polymerase chain reaction was used to investigate the expression profile of the predicted miRNAs; miR-326 and miR-200c, and their predicted targets ABCA2, and ABCA3 transporters. The presence of minimal residual disease was studied using PCR-SSCP (single-strand conformation polymorphism) 1 year after treatment. The association between the miRNA expression and drug resistance was analyzed statistically. Results showed a significant down-regulation of both miR-326 and miR-200c expressions in ALL patients compared with non-cancer controls (P = 0.0002, AUC = 0.813 and P = 0.035, AUC = 0.79, respectively). A considerable negative association between miR-326 expression and MDR was identified which could raise the risk of chemoresistance by 4.8- fold. The expression profiles of miR-326 and ABCA2 transporter were inversely correlated. Data revealed, a novel diagnostic role for miR-326 and miR-200c as potential biomarkers of pediatric ALL. Down-regulation of miR-326 was introduced, for the first time, as a prognostic factor for drug resistance in childhood ALL. To the best of our knowledge, this is the first time that ABCA2 transporter is proposed as a target gene for miR-326, through which it can exert its impact on drug resistance. These data may provide novel approaches to new therapeutics and diagnostics.

Biomarkers are biological molecules found in body fluids or tissues, which can be considered as indications of a normal or abnormal process, or of a condition or disease. There are various types of biomarkers based on their application and molecular alterations. Treatment-sensitivity or drug resistance biomarkers include prognostic and predictive molecules with utmost importance in selecting appropriate treatment protocols and improving survival rates. Acute lymphoblastic leukemia (ALL) is the most prevalent hematological malignancy diagnosed in children with nearly 80% cure rate. Despite the favorable survival rates of childhood ALL (chALL), resistance to chemotherapeutic agents and, as a consequence, a dismal prognosis develops in a significant number of patients. Therefore, there are urgent needs to have robust, sensitive, and disease-specific molecular prognostic and predictive biomarkers, which could allow better risk classification and then better clinical results. In this article, we review the currently known drug resistance biomarkers, including somatic or germ line nucleic acids, epigenetic alterations, protein expressions and metabolic variations. Moreover, biomarkers with potential clinical applications are discussed.

Altered metabolism of fatty acid synthesis is considered a hallmark characteristic of several malignancies, including acute lymphoblastic leukemia (ALL). to evaluate the impact of fatty acid synthase (FASN) on drug resistant ALL, bone marrow samples were collected from 65 pediatric ALLs, including 40 de novo and 25 relapsed patients. 22 non-cancer individuals were chosen as controls. Quantitative RT-PCR showed increased expression levels of FASN in drug resistant patients compared with the therapy responders. Single and combined treatment of malignant cells were analyzed using Annexin-V/PI double staining and MTT assays. Incubation of resistant primary cells with ginger showed simultaneous increased apoptosis rates and reduced FASN expression levels. Furthermore, docking studies demonstrated high affinity bindings between ginger derivatives and FASN thioesterase and ketosynthase domains, compared with their known inhibitors, fenofibrate and morin, respectively. Finally, combined treatment of in-house multidrug resistant TALL subline with ginger and dexamethasone induced drug sensitivity and down regulation of FASN expression, accordingly. To the best of our knowledge, this is the first study that introduces FASN upregulation as a poor prognostic factor for drug resistant childhood ALL. Moreover, it was revealed that fASn inhibition may be applied by ginger phytochemicals and overcome dexamethasone resistance, subsequently. Acute lymphoblastic leukemia (ALL) is the most common type of hematological malignancy in children 1,2. Despite the enormous advances in modern medicine and development of innovative therapeutic strategies, disease relapse remains a leading cause of cancer-related morbidity and mortality in children 3. Metabolic rearrangements are vital to satisfy the different requirements of cancer cells during tumorigenesis 4. Elevated de novo fatty acid biosynthesis is a hallmark adaptation in many cancers that supply signaling molecules and basic elements for lipid biosynthesis 5. While most normal cells supply their fatty acids from dietary sources, cancer cells reactivate de novo fatty acid synthesis 6. Fatty acid synthase (FASN) is a multifunctional protein containing six enzymatic domains that catalyzes the biosynthesis of palmitate 5. Elevated expression of FASN is found to be associated with poor prognosis and higher risk of recurrence in a number of human cancers. Indeed, FASN overexpression has been shown to contribute to multidrug resistance (MDR). Multi-drug resistance is one of the major obstacles to the successful treatment of various types of cancer, particularly childhood ALL 5,7,8. Glucocorticoids (GCs) such as prednisone and dexamethasone (DEX) are indispensable drugs for childhood ALL treatment 9. Early response to glucocorticoids is a positive prognostic indicator and glucocorticoid resistance has been associated with an increased risk of relapse and poor clinical response 10,11. Glucocorticoids regulate FASN expression and subsequently affect lipogenesis 12. Therefore, FASN knock down or...

Purpose Multidrug resistance (MDR) and the subsequent disease relapse are the major causes of childhood acute lymphoblastic leukemia (ALL) related death. The Hedgehog (Hh) signaling pathway can contribute to cancer MDR. In the current study, Smoothened ( Smo ) was selected as the experimental target due to its importance in the Hh pathway in order to evaluate its probable role in pediatric B-ALL drug resistance. Patients and methods The study included 27 pediatric B-ALL and 16 control bone marrow samples. Quantitative RT-PCR was used to investigate the expression levels of Smo and miR-326 as the key players of the Hh pathway. Western blot analysis was performed. The presence of minimal residual disease was studied using PCR-SSCP. The association between Smo expression and drug resistance was analyzed statistically. Results Results showed a significant increase in the Smo expression levels in drug-resistant patients in comparison with drug-sensitive children with B-ALL ( P =0.0128, AUC=0.82). A considerable negative association between miR-326 and Smo expression levels was identified ( r =−0.624, P =0.002). A binomial test confirmed the regulatory role of miR-326 on the translational repression of Smo ( P =0.031). Statistics showed no association between Smo and ABCA2 expression levels. However, a significant positive correlation was observed between the Smo and ABCA3 transcripts in the resistant ALL children ( r =0.607, P =0.016). Conclusion Data revealed the possible oncogenic impact of Smo on leukemogenesis and drug resistance in pediatric B-ALL. Upregulation of Smo was introduced, for the first time, as a prognostic factor for drug resistance in childhood B-ALL. To the best of our knowledge, this is the first study that shows a positive correlation between Smo and ABCA3 expression levels in pediatric B-ALL, explaining a possible mechanism for the development of drug resistance in this cancer. Moreover, the current project revealed a negative modulatory effect of miR-326 on the expression levels of Smo .