Investigating effects of carob extracts on leukaemia

Abstract

Acute promyelocytic leukaemia (APL) is a leukaemia subtype defined by the presence of high numbers of abnormal haematopoietic cells arrested at the promyelocytic stage within the bone marrow. APL prognosis has increased considerably with the introduction of all-trans retinoic acid (ATRA) in combination with arsenic trioxide (ATO) as therapy, however it still has limitations. Particularly, up to 15% of APL patients are either naturally resistant to it or become resistant after repeated rounds of such treatment and relapse. These patients have poor prognosis as it becomes equal to that of patients before ATRA and ATO introduction. Hence, a better treatment is required. Polyphenols present in honeys and syrups have, through studies, shown anticancer effects on leukaemia cells. Therefore, this study aims to confirm if polyphenolrich extracts from carob honey (CHE) and syrup (CSE) have beneficial effects on ATRA-resistant APL NB4-R2 cells and the nature of their effects. Polyphenols were extracted and confirmed through dispersive liquid-liquid microextraction and compositional assays respectively. Their effects on NB4-R2 cell viability and differentiation were tested through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and nitroblue tetrazolium assays and morphological analysis. Their antiproliferative effects were tested through cell cycle analysis, and they were tested on lymphocytes to elucidate cytotoxic effects. At particular concentrations, the CHE and CSE partially differentiated and decreased the viability of NB4-R2 cells and arrested them within different cell cycle phases. They did not negatively affect the viability of lymphocytes. Hence, this study confirmed that specific concentrations of CHE and CSE confer antiproliferative, and a degree of differentiative and viability decreasing effects on these cells but do not confer cytotoxic effects on the healthy cells. Altogether, this study concludes that specific concentrations of CHE and CSE could be a potential treatment against APL and highlights the need for these extracts to be investigated further.