Purpose: To determine whether measurement of colour junctions by fluorescent in situ hybridisation (FISH) can predict radiosensitisation of gemcitabine (2'-2'-difluorodeoxycytidine).
Methods: Human lung carcinoma cells (SW-1573) were irradiated with X-rays with or without incubation of 10 n M gemcitabine for 24 h. Cell survival was determined with clonogenic assay. Colour junctions were measured by whole chromosome FISH of chromosomes 2 and 18 and were scored according to the PAINT method.
Results: A clear radiosensitisation by gemcitabine was observed on cell survival. A significant decrease in the number of colour junctions was observed after gemcitabine treatment compared with radiation treatment alone. The correlation between colour junction induction and cell survival was high for both with and without gemcitabine, but the gemcitabine-sensitised curve did not coincide with the non-sensitised curve.
Conclusions: Gemcitabine-induced radiosensitisation is not predicted by induction of colour junctions in cultured SW-1573 cells. This reduces the clinical applicability of this predictive assay for radiotherapy in combination with gemcitabine.