Fig. 5
From: Folate deficiency as predisposing factor for childhood leukaemia: a review of the literature
Multi-hit hypothesis for the insurgence of childhood leukaemia. The initiation of childhood leukaemia requires multiple oncogenic events to occur, with the first event occurring in utero and a second hit occurring after birth or later in life. The first event may be called the predisposing condition at the genomic level that is necessary but not sufficient for the insurgence of cancer. Leukaemia is initiated when a second event promotes abnormal cell proliferation