In vitro studies using a variety of human cell lines have been used to assess the effectiveness of antineoplastons as antineoplastic agents. Burzynski states that antineoplaston A is species-specific because it had no therapeutic effect when the human preparation was tested on animal tumor systems. Although this finding limits the usefulness of animal model testing, the developer has suggested that a "marked" therapeutic effect was produced in a xenograft bearing human tumor tissue. This claim is made only for antineoplaston A. Other formulations of antineoplastons have not been tested in animal models.
Japanese scientists have tested antineoplastons A10 and AS2-1 in vitro for cell growth inhibition and progression in several human hepatocellular cell lines.[2,3] Tests were performed in a dose-dependent manner at concentrations varying from 0.5 to 8 µg/mL for A10 and AS2-1, and growth inhibition was generally observed at 6 to 8 µg/mL. This dose level is considered excessively high and generally reflects a lack of activity. Growth inhibition of one of the cell lines (KIM-1) was observed at low concentration for a mixture of cisplatin (CDDP) and A10, but this result was probably caused by the cisplatin, which was effective at concentrations of 0.5 to 2.0 μg/mL when tested alone. AS2-1 was reported to induce apoptosis in three of the cell lines at concentrations of 2 and 4 μg/mL.
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Antineoplaston A10 was also shown to inhibit prolactin or interleukin-2 stimulation of mitogenesis in a dose-dependent manner in rat Nb2 lymphoma cell line. The addition of A10 (1–12 mm) to prolactin-stimulated cells inhibited growth but was reversible when A10 was removed, suggesting a cytostatic rather than cytotoxic mechanism of action. A10 also showed no toxicity in a chromium release assay. DNA synthesis was also inhibited by A10.
The ability of antineoplaston A3, isolated from urine and not an analog, to inhibit the growth of the HBL-100 human breast cancer cell line in vitro was investigated in a study that also examined the toxicity of A3 in Swiss white mice. Antineoplaston A3 inhibited colony formation in a dose-dependent manner over a dose range of 0.05, 0.1, 0.2, and 0.4 µg/mL.