“…This synergy may be cancer cell selective in that di erentiation induction is not aberrant in normal cells and consequently the combined toxicity does not a ect normal proliferating cells (Waxman et al, 1990). Interestingly, in primary cultures of leukemic blasts obtained from patients, additions of low doses of chemotherapy with the combination of di erentiation agents has resulted in a higher di erentiation induction than the individual agents (Hassan et al, 1991). This is consistent with the clinical observation that duration of remission in patients with APL is signi®cantly longer following RA combined with chemotherapy as compared to ATRA followed by chemotherapy.…”