POTENTIATING EFFECT OF CITRAL IN COMBINATION WITH DOXORUBICIN, VINCRISTINE OR ETOPOSIDE ON HUMAN B-LYMPHOMA CELLS

Abstract

This study intended to evaluate the potentiating effect of citral on anticancer effects of doxorubicin, vincristine, and etoposide against human lymphoma Ramos cells. Cytotoxicity of citral and anticancer drugs was determined by resazurin reduction assay. The results demonstrated that citral and these drugs had cytotoxicity on Ramos cells at 24 hours incubation. The IC50 value of citral was 75.9 µM. Citral at 10-40 µM significantly increased the cytotoxic effects of doxorubicin, vincristine, and etoposide on Ramos cells, leading to the decrease in the IC50 value of each drug. It did not increase the effect of these anticancer drugs on normal human peripheral blood mononuclear cells (PBMCs). This study also evaluated the effect of citral on apoptosis induction activity of the anticancer drugs by annexin V-FITC and 4', 6-diamidino-2-phenylindole (DAPI) staining monitored by fluorescence flow cytometer. The result demonstrated that citral increased anticancer drug-mediated apoptosis against human B lymphoma cells. BCL-2 family proteins play a pivotal role in the regulation of the mitochondrial pathway of apoptosis. Modulation of the mRNA expression of these proteins in the treated Ramos cells was also performed by real time RT-PCR. The mRNA expression of pro-apoptotic BAK was dramatically increased in Ramos cells treated with either 40 µM citral alone or in combination with anticancer drug. On the other hand, it significantly decreased the mRNA expression of anti-apoptotic BCL-XL when compared to the effect of the doxorubicin alone. Thus, it is possible that citral may potentiate apoptotic effect of doxorubicin by reducing the expression of anti-apoptotic BCL-XL. Citral did not change anti-proliferative effect of the drugs. In conclusion, citral potentiated cytotoxicity of doxorubicin, vincristine, and etoposide by increasing in apoptotic effect of these drugs. The results from this study may be an initial information about the possible potentiating anticancer activity of citral which is a component in several edible plants. This additive effect of citral may be useful for consuming food containing citral while using these anticancer drugs.