Repurposing Alzheimer’s disease medications in a drug combination for the study of the crosstalk between cell apoptosis and autophagy in the modulation of cell death in chronic myeloid leukaemia

The world population is ageing and with this shift is a concurrent rise in comorbidities such as Alzheimer’s disease (AD) and cancer. Interestingly, an increasing number of studies have reported certain AD drugs to possess anti-cancer properties. This raises the possibility of repurposing these AD drugs for the treatment of cancers such as chronic myeloid leukaemia (CML). This requires the understanding of the possible interconnection between CML and AD at the molecular level. The overall aim of this research was to study the crosstalk between cell apoptosis and autophagy in the modulation of cell death and to determine if AD medications, singly and in combination with a CML drug, have the potential to be repurposed for the treatment of CML
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HEK293T (cell model of AD) and K-562 (cell model of CML) cells were individually treated with the test drugs for 24 and 48 h, depending on the assay. Cell viability was assessed by overlaying the treated cells with CyQUANT® Direct assay dye for 40 min before fluorescence signal detection at a wavelength of 485/520 nm excitation/emission. Cell death assay was also conducted using BD FACSCalibur flow cytometer to detect fluorescent emission at 530 nm (FL1), 575 nm (FL3) and excitation wavelength of 488 nm, in Annexin V/PI-stained treated cells. To examine the autophagic and apoptotic effects modulated by the drug treatments, Western blot analyses were carried out and the proteins of interest were quantified using Image Studio software on the Odyssey® Fc LI-COR Imaging System.
The results demonstrated that the chemotherapy drug, Doxorubicin, caused death in both HEK293T and K-562 cells by modulating the apoptotic pathway. In 48 h Doxorubicin (1 μM)-treated K-562 cells, the autophagic proteins, Beclin-1 (p < 0.05) and LC3 (p < 0.001), were also upregulated. With the addition of Chloroquine (10 μM), a known autophagy inhibitor, these autophagic activities were verified as being involved in the induction of cell death in the CML cells. When Imatinib (1 μM), a known tyrosine kinase inhibitor, was used in the treatment of CML K562 cells, it was shown to also induce apoptotic cell death effect but without the involvement of the Beclin-1-induced autophagy pathway. Therapeutically relevant but low concentrations (1, 5 and 10 μM) of Memantine and Donepezil (AD drugs) were shown to be non-toxic in this study, as they induced no measurable cell death in both cell lines tested, with Memantine (1 μM) increasing the viability of HEK293T (the AD cell model) by 41% (p < 0.05). Following the results of the preliminary study, further investigations were carried out employing the combination of Doxorubicin (1 μM) and Memantine (1 μM) to determine if the Doxorubicin-killing effect in the CML cells can be enhanced while mitigating its adverse effects in HEK293T non-cancer cells. For the first time, we report herein the apoptotic and autophagic effects of Doxorubicin and Memantine as a combination drug in K-562 and HEK293T cells. The presence of Memantine in the combination induced an increase in the levels of anti-apoptotic Bcl-2 proteins in the non-cancerous HEK293T cells (p = 0.001), but not in K-562 cells. Also, the autophagy-mediated cell death pathway initially induced by Doxorubicin in K-562 cells was maintained in the Doxorubicin/Memantine (1 μM)-treated CML cells.
The findings from this study indicated that the AD drug, Memantine, could modulate the apoptotic pathway to reduce the Doxorubicin-induced death effect in the non-cancerous HEK293T cells without suppressing its killing effect in the K-562 CML cells. Further studies (in vitro and in vivo) are warranted to help develop this therapeutic strategy that offers non-cancer cell protection while simultaneously providing therapeutic benefits against the cancer cell population in AD and CML co-morbidity.