Targeted treatment for chronic lymphocytic leukemia

Targeting Mitochondrial Apoptosis to Overcome Treatment Resistance in Cancer

Deregulated cellular apoptosis is a hallmark of cancer and chemotherapy resistance. The B-cell lymphoma 2 (BCL-2) protein family members are sentinel molecules that regulate the mitochondrial apoptosis machinery and arbitrate cell fate through a delicate balance between pro- and anti-apoptotic factors. The recognition of the anti-apoptotic BCL2 gene as an oncogenic driver in hematological malignancies has directed attention toward unraveling the biological significance of each of the BCL-2 superfamily members in cancer progression and garnered interest in the targeting of apoptosis in cancer therapy. Accordingly, the approval of venetoclax (ABT-199), a small molecule BCL-2 inhibitor, in patients with chronic lymphocytic leukemia and acute myeloid leukemia has become the proverbial torchbearer for novel candidate drug approaches selectively targeting the BCL-2 superfamily. Despite the inspiring advances in this field, much remains to be learned regarding the optimal therapeutic context for BCL-2 targeting. Functional assays, such as through BH3 profiling, may facilitate prediction of treatment response, development of drug resistance and shed light on rational combinations of BCL-2 inhibitors with other branches of cancer therapy. This review summarizes the pathological roles of the BCL-2 family members in cancer, discusses the current landscape of their targeting in clinical practice, and highlights the potential for future therapeutic inroads in this important area.

Tumor-selective cytotoxicity of a novel pentadiene analogue on human leukemia/ lymphoma cells

BACKGROUND

A novel series of structurally divergent 1,5-diaryl-3-oxo-1,4-pentadiene analogues 1-10 displayed marked cytotoxic potencies towards a number of human leukemia/lymphoma cells.

OBJECTIVE

To identify novel selective cytotoxic compounds that induce apoptosis.

METHODS

The Differential Nuclear Staining (DNS) screening protocol was utilized to measure the cytotoxicity of all experimental dienones on several cancerous cells. Additionally, the selective cytotoxicity index was calculated by comparing the dienone's cytotoxicity between leukemia/lymphoma cells vs. non-cancerous cells. Furthermore, to discern whether a selected dienone induced cell death via apoptosis or necrosis on T-lymphocyte leukemia cells, diverse approaches were utilized to detect individual biochemical facets of apoptosis.

RESULTS

The dienones were tested for their anti-neoplastic efficiency on human leukemia/lymphoma-derived cell lines. Special emphasis was applied on dienone 1, on the basis of its sub-micromolar cytotoxicity (CC₅₀=0.43+0.02 μM) and high selective cytotoxicity index (11.1) exerted on T-leukemia cells. In general, dienone 1 showed the most potent cytotoxic properties as compared to other dienones and a related reference cytotoxin curcumin as well as the EF-24 curcumin analogue. Dienone 1 caused cell death by apoptosis in Jurkat cells as evidenced by inducing phosphatidylserine externalization, mitochondrial depolarization and caspase-3/7. These effects were mainly attributed to the induction of apoptotic pathways.

CONCLUSION

The novel dienone 1 was found to exhibit potent anti-leukemia activity by inducing programmed cell death/apoptosis. Consequently, dionone 1 should be developed further to examine its potential efficacy to combat malignancies in a pre-clinical animal model.

A novel class of piperidones exhibit potent, selective and pro-apoptotic anti-leukemia properties

In the present pre-clinical study, a series of 1-[3-(2-methoxyethylthio)-propionyl]-3,5- bis(benzylidene)-4 piperidones and structurally-related compounds were observed to be cytotoxic in vitro to three human leukemia cell lines, namely Nalm-6, CEM and Jurkat. The 50% cytotoxic concentration (CC₅₀) values of the three cell lines ranged between 0.9-126.4 µM and 0.3-11.7 µM at 24 and 48 h subsequent to exposure, respectively. The two lead compounds with sub-micromolar CC₅₀ concentrations, 1-(2-methoxyethylthio-propionyl)-3,5-bis(benzylidene)-4 piperidone (2a) and 3,5-bis(4-fluorobenzylidene)-1-[3-(2-methoxyethyl sulfinyl)-propionyl]-4-piperidone (3e), were selected for additional analyses. Several strategies were undertaken to determine whether the above piperidones caused cell death via apoptosis or necrosis on T-lymphocyte leukemia Jurkat cells. The results revealed that the two piperidones caused phosphatidylserine externalization, mitochondrial depolarization and activation of caspase-3, which are all biochemical hallmarks of apoptosis. In addition, the selected piperidones displayed selective cytotoxicity towards leukemia cells, and were less toxic in non-cancerous control cells. Therefore, the findings of the present study revealed that the novel piperidones 2a and 3e exert a selective cytotoxic effect on lymphocyte leukemia cells by favoring the activation of the intrinsic/mitochondrial apoptotic pathway.