Given previous work indicating involvement of tumour cell LFA-1 expression in lymphoma [29] and liver metastasis [7], we hypothesised that owing to the presence of LFA-1 on breast cancer cells, knocking down LFA-1 expression in the tumour cells would impair interactions with host tissue cells, primarily through ICAM-1 interaction, and alter tumour colonisation in the brain. This evidence concerns the gene ITGAL and breast cancer.