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Recently, great progress has been achieved in the treatment of chronic lymphocytic leukemia (CLL). However, some patients, particularly older patients with comorbidities or with relapsed/refractory leukemia, still have limited therapeutic options. There is an urgent need to discover less toxic and more effective drugs for CLL patients. Applying new modalities or substances that are widely used for the treatment of other diseases has been reported to improve results in CLL treatment. This study aimed to assess the non-chemotherapeutic drug danazol for its potential to destroy leukemic cells. Leukemic cells, obtained from the peripheral blood and bone marrow of 23 CLL patients, were cultured in the presence of danazol and its combination with the purine nucleoside analogs fludarabine and cladribine and bendamustine. After 24 h of incubation, the rate of apoptosis indicated by active caspase-3 expression, and cytotoxicity indicated by forward light scatter and light scatter analysis, was assessed by flow cytometry. We also measured expression of apoptosis-regulating proteins of BCL family and active caspase 9 and active caspase 8 expressions in leukemic cells. Danazol had a caspase-dependent pro-apoptotic and cytotoxic effect on leukemic cells in a tumor-specific manner. The mechanisms of its action appear to be complex and should be precisely established; however, induction of apoptosis involving both mitochondrial and receptor cascades appears to be most probable. Danazol showed a synergic effect with cladribine, an additive effect with fludarabine, and an infra-additive effect with bendamustine. The rate of danazol-induced apoptosis and cytotoxicity did not differ between patients with better and worse prognostic markers. Our results indicate that danazol may be a potential therapeutic agent for CLL patients alone and in combination with purine analogs.

In this study, we attempted to assess the interactions of resveratrol, a natural compound present in various plant species, with the purine analogues fludarabine and cladribine in terms of their effects on DNA damage and apoptosis in chronic lymphocytic leukemia (CLL) cells. The experiments were performed ex vivo using short-term cell cultures of blood and bone marrow cells from newly diagnosed untreated patients. We analyzed the expression of active caspase-3 and the BCL-2/BAX ratio as markers of apoptosis and the expression of phosphorylated histone H2AX (γH2AX) and activated ATM kinase, which are reporters of DNA damage. The results of our study revealed that resveratrol induced apoptosis in CLL cells in a tumor-specific manner but did not affect non-leukemic cells, and apoptosis was associated with a decreased BCL2/BAX ratio. Here, we report for the first time that both resveratrol + fludarabine and resveratrol + cladribine caused a higher rate of apoptosis in comparison to the rate caused by a single drug. The percentage of apoptotic cells induced by resveratrol alone was higher in the group of patients with better prognostic markers than in those with worse prognostic markers. However, the rates of apoptosis caused by resveratrol combined with purine analogues were independent of ZAP-70 and CD38 expression and the clinical state of the disease; they were only dependent on the presence of high-risk cytogenetic abnormalities. We also observed an increase in γH2AX expression together with a rise in activated ATM in most of the analyzed samples. The obtained results indicate that resveratrol might warrant further study as a new therapeutic option for CLL patients. This naturally occurring substance may be used as a single agent, especially in older persons for whom there are some limitations for the use of aggressive treatment. On the other hand, a lower purine analogue dose could potentially be used in combination with resveratrol because of their combined effect. One of the mechanisms of action of resveratrol is the induction of DNA damage, which ultimately leads to apoptosis.

Despite many therapeutic regimens introduced recently, chronic lymphocytic leukemia (CLL) is still an incurable disorder. Thus, there is an urgent need to discover novel, less toxic and more effective drugs for CLL patients. In this study, we attempted to assess simvastatin, widely used as a cholesterol-lowering drug, both as a single agent and in combination with purine analogs-fludarabine and cladribine-in terms of its effect on apoptosis and DNA damage of CLL cells. The experiments were done in ex vivo short-term cell cultures of blood and bone marrow cells from newly diagnosed untreated patients. We analyzed expression of active caspase-3 and the BCL-2/BAX ratio as markers of apoptosis and the expression of phosphorylated histone H2AX (named γH2AX) and activated ATM kinase (ataxia telangiectasia mutated kinase), reporters of DNA damage. Results of our study revealed that simvastatin induced apoptosis of CLL cells concurrently with lowering of BCL-2/BAX ratio, and its pro-apoptotic effect is tumor-specific, not affecting normal lymphocytes. We observed that combinations of simvastatin+fludarabine and simvastatin+cladribine had a synergic effect in inducing apoptosis. Interestingly, the rate of apoptosis caused by simvastatin alone and in combination was independent of markers of disease progression like ZAP-70 and CD38 expression or clinical stage according to Rai classification. We have also seen an increase in γH2AX expression in parallel with activation of ATM in most of the analyzed samples. The results suggest that simvastatin can be used in the treatment of CLL patients as a single agent as well as in combination with purine analogs, being equally effective both in high-risk and good-prognosis patients. One of the mechanisms of simvastatin action is inducing DNA damage that ultimately leads to apoptosis.