CYP1B1 and neoplasm: In CAL27 cells, control tumours, not expressing CYP1B1, increased by 1.5–2.5-fold under treatment, while CYP1B1-WT tumours were resistant to all three drugs, with tumour size increasing by 5–10-fold; CYP1B1-VAR tumours were resistant to a much higher degree, the average tumour increase at the end of the treatment being in the range of 10–20-fold.