Previously, we (a) identified SLIT2 promoter methylation in 53% non-small-cell lung cancer, 36% small-cell lung cancer and 43% of breast cancers, (b) demonstrated that promoter methylation is associated with reversible transcriptional silencing and (c) determined that restoration of SLIT2 expression suppressed tumour growth in in vitro studies (Dallol et al, 2002a). The gene discussed is SLIT2; the disease is breast carcinoma.