An allomaltol derivative triggers distinct death pathways in luminal a and triple-negative breast cancer subtypes

Breast cancer is the most common cancer in women that shows a predisposition to metastasize to the distant organs. Kojic acid is a natural fungal metabolite exhibiting various biological activities. Compounds derived from kojic acid have been extensively studied and proved to demonstrate anti-neoplastic features on different cancer types. In the present study, allomaltol-structural analog of kojic acid and its seven derivatives including four novel compounds, have been synthesized, characterized and their possible impact on breast cancer cell viability was investigated. It was discovered that compound 5, bearing 3,4-dichlorobenzyl piperazine moiety, could decrease the viability of both MCF-7 and MDA-MB-231 cell lines distinctively. To ascertain the death mechanism, cells were subjected to different tests following the application of IC₅₀ concentration of compound 5. Data obtained from lactate dehydrogenase activity and gene expression assays pointed out that necrosis had taken place predominantly in MDA-MB-231. On the other hand, in MCF-7 cells, the p53 apoptotic pathway was activated by overexpression of the pro-apoptotic TP53 and Bax genes and suppression of the anti-apoptotic Mdm-2 and Bcl-2 genes. Furthermore, Bax/Blc-2 ratio was escalated by 3.5 fold in the study group compared to the control. Compound 5 did not provoke drug resistance in MCF-7 cells since the Mdr-1 gene expression, drug efflux, and H₂O₂ content remained unaltered. As for MDA-MB-231 cells, only a 1.4 fold increase in the Mdr-1 gene expression was detected. These results indicate the advantage of the allomaltol derivative over the chemotherapeutic agents conventionally used for breast cancer treatment that can be highly toxic and mostly lead to drug resistance. Thus, this specific allomaltol derivative offers an alternative therapeutic approach for breast cancer which needs further investigation.

Evaluation of antibacterial and anti-biofilm properties of kojic acid against five food-related bacteria and related subcellular mechanisms of bacterial inactivation

Although the antimicrobial properties of kojic acid have been recognized, the subcellular mechanism of bacterial inactivation caused by it has never been clearly elucidated. In the present study, the antibacterial and anti-biofilm activity of kojic acid was evaluated against five foodborne pathogens including Listeria monocytogenes, Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Salmonella typhimurium. The antibacterial activity was determined by minimum inhibitory concentration, minimum bactericidal concentration, and the time-kill assay. Among them, the susceptibility of Escherichia coli was significant with the lowest minimum inhibitory concentration and minimum bactericidal concentration values of 10 and 20 mM, respectively. Subcellular mechanism of bacterial inactivation related to kojic acid was revealed through comprehensive factors including cell morphology, membrane permeability, K+ leakage, zeta potential, intracellular enzyme, and DNA assay. Results demonstrated that bacterial inactivation caused by kojic acid, especially for Gram-negative bacteria, was primarily induced by the pronounced damage to the cell membrane integrity. Leakage of intracellular enzyme to the supernatants implied that the cell membrane permeability was compromised. Consequently, the release of K+ from the cytosol leads to the alterations of the zeta potential of cells, which would disturb the subcellular localization of some proteins and thereby cause the bacterial inactivation. The free −CH2OH group at the C-2 of kojic acid could play more significant role in the antimicrobial performance of kojic acid against Gram-negative bacteria. Moreover, remarkable interaction with DNA was also observed. Kojic acid at sub-minimum inhibitory concentration inhibited biofilm formation by these bacteria.