Effects of lucanthone on chinese hamster V-79 cells I. Interaction with radiation in monolayers and spheroids

Abstract

Lucanthone has previously been shown to reduce the capacity of cells to accumulate and repair sublethal radiation damage, which suggests its potential as an adjuvant to clinical radiotherapy. Present results indicate that lucanthone was effective even for V-79 cells having a markedly enhanced shoulder on the radiation survival curve as a result of growth as multicell spheroids. Lucanthone also proved to be an effective cytotoxic agent in large spheroids. Unlike radiation toxicity, however, lucanthone toxicity was equal for cells from asynchronous monolayers or small spheroids. Thus, for equal levels of drug toxicity, the radiation-modifying effect of lucanthone was greater in the spheroid; the “interaction” was larger in the system which had a greater capacity for accumulation and repair of sublethal radiation damage. Direct extrapolation of this result to the clinic would suggest that lucanthone be used judiciously, and that it might be of value as an adjuvant to radiotherapy only in the unusual circumstance where the malignant tissue has a larger capacity for accumulation and repair of sublethal radiation damage than the surrounding normal tissue.