Low dose cytosine-arabinoside has only minimal differentiation inducing capacity in HL60 cells

Salvage therapy with low-dose cytosine arabinoside in refractory or relapsed acute non-lymphocytic leukaemia: a report on 25 patients

Thirteen patients with de novo acute non-lymphocytic leukaemia (ANLL) refractory to standard chemotherapy for remission induction and 12 patients with ANLL in relapse were treated with low-dose cytosine arabinoside (LD ara-C) 10 mg/m2 subcutaneously every 12 hours for 21 days. Five of 13 patients (38%) and 6 of 12 patients (50%), respectively, obtained a complete remission (CR). Of these, 7 patients subsequently relapsed after 2-76 months, while 4 patients remain in CR after 7-131 months. Compared to standard intensive regimens treatment with LD ara-C was rather non-toxic, requiring platelet transfusions and antibiotics in only 6 and 13 cases, respectively. Three patients (12%) died during induction therapy with LD ara-C; 2 had a cerebral haemorrhage and 1 developed anuria following a staphylococcal septicaemia. In conclusion, therapy with LD ara-C may be preferable to more intensive and toxic regimens in the treatment of patients with relapsed or refractory ANLL.

A quantitative ultrastructural and cytochemical study of TPA-induced differentiation in HL-60 cells

The effects of the phorbol ester 12-O-tetradecanoyl phorbol-13-acetate on morphometric and stereological parameters have been studied using the HL-60 cell line as a differentiation model for the monocytic pathway. Evaluation of the differentiation was carried out by quantification of endoplasmic reticulum, Golgi apparatus, mitochondria and cytoplasmic granules. Changes in both nuclear and cytoplasmic volumes during TPA-induced differentiation led to a decrease of the nucleus-cytoplasmic ratio after 3 days of treatment. Plasma membrane glycoprotein pattern was also determined. The major change in cell surface was the presence of high amounts of glycoproteins containing N-acetyl glucosamine residues that make wheatgerm agglutinin lectin a valuable marker of the monocytic differentiation pathway in HL-60 cells.

Low-dose cytarabine for acute myeloid leukaemia and myelodysplastic syndromes: in vivo and in vitro cytotoxicity

14 patients with acute myeloid leukaemia (AML) and 7 with myelodysplastic syndrome (MDS) were treated with cytarabine in low dosage. In AML a complete remission rate of 43% was found and in all patients profound cytopenia was noticed without any sign of maturation induction. In MDS no effect of low-dose cytarabine could be detected. We also studied the effect of low-dose cytarabine in vitro in freshly isolated leukaemic cells of 10 patients with AML. Maturation induction was measured by a comprehensive panel of quantitative and qualitative markers of maturation. No differentiation inducing effect of low-dose cytarabine could be found. We conclude on the basis of our own results and after reviewing the literature that low-dose cytarabine exerts its effect by cytotoxicity instead of maturation induction.