Effects of sodium ascorbate (vitamin C) and 2-methyl-1,4-naphthoquinone (vitamin K3) treatment on human tumor cell growth in vitro. II. Synergism with combined chemotherapy action.

The growth inhibitory effects of a combined application of sodium ascorbate (Vitamin C) and 2-methyl-1,4-naphthoquinone (Vitamin K3) together with various chemotherapeutic agents has been examined on in vitro cultured human endometrial adenocarcinoma (AN3CA) cells. Combined vitamin treatment and chemotherapy in well defined conditions of cell confluence and at the dose levels applied result in a synergistic effect on growth inhibition. The combined vitamins when reaching their own synergistic cytotoxicity levels frequently obscure the additional synergistic effects attributable to the chemotherapeutic agents. Apart from the specific cytotoxic characteristics of the chemotherapeutic drugs examined, the formation of reactive oxygen radicals during treatment, possibly accentuated by less defined secondary mechanisms, appears essentially responsible for the observed stimulated cytotoxicity.