Browsing by Author "Şahin, Hande Nur"

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Citation - Scopus: 3
Combined Effect of Midostaurin and Sphingosine Kinase-1 İnhibitor on FMS-Like Tyrosine Kinase 3 (FLT3) Wild Type Acute Myeloid Leukemia Cells
(De Gruyter Open Ltd, 2022) Şahin, Hande Nur; Adan, Aysun
Objectives: Therapeutic potential of clinically approved FLT3 inhibitor midostaurin has been neglected in wild-type FLT3 positive acute myeloid leukemia (AML). Sphingosine kinase-1 (SK-1) having anti-proliferative functions is studied in various cancers, but not in FLT3 wild-type AML. We aimed to develop new therapeutic strategies to combat FLT3 wild-type AML by combining midostaurin with SK-1 inhibitor (SKI II) in THP1 cells. Methods: The anti-proliferative effects of midostaurin, SKI II and in combination on THP1 cells were determined by MTT assay. The combination indexes were calculated using calcusyn software. SK-1 expression and PARP cleavage were checked by western blot. Cell cycle distributions (PI staining) and apoptosis (annexin-V/PI dual staining) were assessed by flow cytometry for each agent alone and in combinations. Results: Midostaurin decreased SK-1 protein level. Midostaurin, SKI II and certain combinations decreased cell viability in a dose dependent manner. The combined anti-leukemic effects of the aforementioned drug combination afforded additive effect. Co-administration induced both necrosis and apoptosis via phosphatidylserine externalization, PARP cleavage and cell cycle arrest at G0/G1 and S phases. Conclusions: Targeting sphingosine kinase-1 together with FLT3 inhibition could be a novel mechanism to increase limited clinic response to midostaurin in wild-type FLT3 overexpressing AML after further pre-clinical studies. © 2022 Elsevier B.V., All rights reserved.
Citation - Scopus: 1
Glucosylceramide Synthase is a Novel Biomarker of Midostaurin-Induced Cytotoxicity in Non-Mutant FLT3 Positive Acute Myeloid Leukemia Cells
(Istanbul University Press, 2021) Şahin, Hande Nur; Adan, Aysun
Objective: Glucosylceramide (GC) synthesized by glucosylce-ramide synthase (GCS) favors cell survival and proliferation in many cancers. However, it’s role in Fms-like tyrosine kinase 3 (FLT3) non-mutant Acute Myeloid Leukemia (AML) pathogenesis is not clarified. Midostaurin, a multi-kinase inhibitor, clinically benefits FLT3-mutated AML, however, its clinical efficacy is under-estimat-ed in FLT3 non-mutant AML. This study aimed to investigate the efficacy of combination of midostaurin with GCS inhibitor in FLT3 AML cell carrying wild-type FLT3 and the underlying molecular mechanisms. Material and Method: Cytotoxic and cytostatic effects of mido-staurin, PDMP (GCS inhibitor) alone and in combination on THP1 cells were determined by MTT assay and flow cytometric propidi-um iodide (PI) staining, respectively. Calcusyn software was used to calculate combination indexes (CIs). GCS expression was checked by western blot. Results: Midostaurin downregulated GCS. Simultaneous inhibition of FLT3 and GCS resulted in suppression of cell proliferation as compared to untreated control. Combinations showed synergistic cytotoxic effects (CI<1). Co-treatments increased cell cycle population at G2/M phase. Conclusion: Inhibition of GCS enhances the efficacy of midostau-rin in FLT3 non-mutant AML, which could be a novel therapeutic approach to increase midostaurin’s limited usage in the clinic after detailed mechanistic studies. © 2023 Elsevier B.V., All rights reserved.