Elderly patients with chronic lymphocytic leukaemia (CLL): predicting their survival and managing their disease with valproic acid and fludarabine

Chronic Lymphocytic Leukaemia (CLL) is a disease of B-lymphocytes that account for significant morbidity and mortality in mostly elderly patients (aged ≥ 70 years). The relative survival of patients with CLL has been shown to decrease with patient age, and this age-related reduction in survival was found to correlate with the levels of two inflammatory cytokine levels in the patients’ plasma. The levels of two inflammatory cytokines, interleukin-6 and -8 (IL-6, IL-8) were found to correlate positively with patient age, and increased levels were associated with lower overall survival. Addition of IL-6 or IL-8 to a co-culture system of CLL cells with bone marrow stromal cells increased the CLL-stromal cell adhesion, and co-culturing increased IL-8 secretion. In a search of a treatment regimen that may be effective and readily tolerated by elderly patients, we examined the combination of fludarabine with valproic acid (VPA), an epileptic that was found to inhibit histone deacetylases (HDACs). The combination was synergistic against human leukaemic cells, including primary CLL cells. In a phase II clinical trial where six elderly patients with relapsed, previously treated CLL were enrolled (half of whom were clinically refractory to fludarabine), the VPAfludarabine combination induced reduction in the peripheral and lymph node tumour loads. Mechanistically, the fludarabine treatment induced disruption of the lysosomes, while VPA induced increase in the level and activity of cathepsin B, a lysosomal protease. The VPA-induced increase in cathepsin B levels was observed in in cell lines (in vitro), primary CLL cells (ex vivo) and in patients treated with VPA (in vivo). Chemical inhibition of cathepsin B was sufficient to dampen the VPA-fludarabine cytotoxicity, and the addition activated cathepsin B to leukaemic cell lysates was sufficient to induce caspase cleavage and reduction in anti-apoptotic protein levels. The VPA-fludarabine combination also lowered phospho-Akt levels and ATM activation, which also contributed ...