Metformin and Thymoquinone Synergistically Inhibit Proliferation of Imatinib-Resistant Human Leukemic Cells

Una Glamoclija; Lejla Mahmutovic; Esma Bilajac; Violeta Soljic; Katarina Vukojevic; Mirza Suljagic

doi:10.3389/fphar.2022.867133

Metformin and Thymoquinone Synergistically Inhibit Proliferation of Imatinib-Resistant Human Leukemic Cells

Front Pharmacol. 2022 Apr 13:13:867133. doi: 10.3389/fphar.2022.867133. eCollection 2022.

Authors

Una Glamoclija^{1

2

3}, Lejla Mahmutovic⁴, Esma Bilajac⁴, Violeta Soljic^{2

5}, Katarina Vukojevic^{2

6}, Mirza Suljagic⁷

Affiliations

¹ Department of Biochemistry and Clinical Analysis, University of Sarajevo-Faculty of Pharmacy, Sarajevo, Bosnia and Herzegovina.
² Department of Histology and Embryology, School of Medicine, University of Mostar, Mostar, Bosnia and Herzegovina.
³ Scientific Research Unit, Bosnalijek JSC, Sarajevo, Bosnia and Herzegovina.
⁴ Genetics and Bioengineering Department, Faculty of Engineering and Natural Sciences, International University of Sarajevo, Sarajevo, Bosnia and Herzegovina.
⁵ Faculty of Health Studies, University of Mostar, Mostar, Bosnia and Herzegovina.
⁶ Department of Anatomy, Histology and Embryology, University of Split School of Medicine, Split, Croatia.
⁷ 3D BioLabs, FabLab Bosnia and Herzegovina, University of Sarajevo, Sarajevo, Bosnia and Herzegovina.

Abstract

Chemotherapy resistance is one of the major challenges in cancer treatment, including leukemia. A massive array of research is evaluating combinations of drugs directed against different intracellular signaling molecules to overcome cancer resistance, increase therapy effectiveness, and decrease its adverse effects. Combining chemicals with proven safety profiles, such as drugs already used in therapy and active substances isolated from natural sources, could potentially have superior effects compared to monotherapies. In this study, we evaluated the effects of metformin and thymoquinone (TQ) as monotherapy and combinatorial treatments in chronic myeloid leukemia (CML) cell lines sensitive and resistant to imatinib therapy. The effects were also evaluated in primary monocytic acute myeloid leukemia (AML) and chronic lymphocytic leukemia (CLL) cells. Both compounds induced a dose- and time-dependent decrease of viability and proliferation in tested cells. Metformin had similar IC₅₀ values in imatinib-sensitive and imatinib-resistant cell lines. IC₅₀ values of TQ were significantly higher in imatinib-resistant cells, but with a limited resistance index (2.4). Synergistic effects of combinatorial treatments were observed in all tested cell lines, as well as in primary cells. The strongest synergistic effects were observed in the inhibition of imatinib-resistant cell line proliferation. Metformin and TQ inhibited the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling and induced apoptosis in tested cell lines and primary cells. The enhanced effects of combinatorial treatments on the induction of apoptosis were more dominant in imatinib-resistant compared to imatinib-sensitive CML cells. Primary cells were more sensitive to combinatorial treatments compared to cell lines. A combination of 1.25 mM metformin and 0.625 µM TQ increased the levels of cleaved poly (ADP-ribose) polymerase (PARP), decreased the levels of proliferation regulatory proteins, and inhibited protein kinase B (Akt) and NF-κB signaling in primary CLL cells. This study demonstrates that combinatorial treatments of imatinib-resistant malignant clones with metformin and TQ by complementary intracellular multi-targeting represents a promising approach in future studies.

Keywords: combinatorial therapy; leukemia; metformin; therapy resistance; thymoquinone.