Effects of Ascorbic Acid on Tax, NF- κB and MMP-9 in Human T-cell Lymphotropic virus type 1 positive malignant T-Lymphocytes.

BACKGROUND: HTLV-1 is a retrovirus that infects CD4-positive cells and leads to Adult T-cell leukemia by constitutive activation of nuclear factor kappa B. Ascorbic acid (AA) is an essential nutrient that possess anti-proliferative and pro-apoptotic activity against a number of malignant cell lines. This study delineates the effect of AA on Tax protein expression as well as NF-κB and MMP9 activity in two HTLV-1-positive leukemia cells (HuT-102 and C91-PL).

METHODS: The cytotoxic and antiproliferative effect of AA were studied by LDH release and MTT tests respectively. The proteins expression level was assessed by western blotting. RT-PCR was used to study mRNAs level. Finally, ELISA/EMSA and Zymography were used to evaluate NF-κB and MMP-9 activities respectively.

RESULTS: Cell lines were treated with non-cytotoxic concentrations of AA for 48h and 96h, which resulted in a significant inhibition of proliferation at a concentration of 50μg/ml at 96h in both cell lines. The same concentration inhibited Tax protein expression as well as the NF-κB nuclearization and DNA binding activity. The inhibitory effect of AA on MMP9 protein expression and activity started at 100μg/ml and 50μg/ml in HuT-102 and C91-PL cells respectively, with no effect at the transcriptional levels of MMP-9 in either one of the two cell lines.

CONCLUSION: These results indicated that while the AA exerted its anti-proliferative effect on the NF- κB activation pathway by suppressing Tax expression, its effects on MMP9 seemed to be independent of this mechanism and follow a different approach.