Levels of Viral Glycoprotein Provide a Measure of Modulated Chemotherapeutic Effect

A chemosensitivity assay with small replicate Mm5mt/cl C3H mammary tumor cell cultures was developed to determine whether changes in viral antigen expression and release into culture fluids could be utilized as an in vitro measure of modulating drug effect. The 52,000 MW viral envelope glycoprotein (gp52) of the mouse mammary tumor virus (MMTV) was measured in culture fluids of control and drug-treated cultures while cell density was simultaneously determined by cell staining and OD 664 nm determination. While extra-cellular gp52 levels and cell density progressively increased over 72 hours for control cultures, declines in both parameters provided dual measures of effect for combination [N(phophonacetyl-L-aspartic acid)+5-fluorouracil], combination 〔N(phophonacetyl-L-aspartic acid )+5-fluoro-5'-deoxyuridine〕and single component treatment of this combination. At each treated time point, thesecombinations begin to produce a greater decline in both cell density and gp52 levels as compared to single drug treatments. These results indicate that N(phopho-nacetyl-L-aspartic acid) in combination can enhance the effectiveness of single drug.