Curcumin reduces expression of Bcl-2, leading to apoptosis in daunorubicin-insensitive CD34⁺acute myeloid leukemia cell lines and primary sorted CD34⁺acute myeloid leukemia cells

• Main Authors: Huang Sheng-Shan, Long Zi-Jie, Zheng Fei-Meng, Xu Duo-Rong, Rao Jia, Wu Xing, Zhou Wei-Hua, Huang Ren-Wei, Liu Quentin
• Format: Article
• Language: English
• Published: BMC 2011-05-01
• Series: Journal of Translational Medicine
• Online Access: http://www.translational-medicine.com/content/9/1/71
• ISSN: 1479-5876

<p>Abstract</p> <p>Background</p> <p>Acute myeloid leukemia (AML) is an immunophenotypically heterogenous malignant disease, in which CD34 positivity is associated with poor prognosis. CD34⁺AML cells are 10-15-fold more resistant to daunorubicin (DNR) than CD34^-AML cells. Curcumin is a major component of turmeric that has shown cytotoxic activity in multiple cancers; however, its anti-cancer activity has not been well studied in DNR-insensitive CD34⁺AML cells. The aim of this study was to therefore to explore curcumin-induced cytotoxicity in DNR-insensitive CD34⁺AML cell lines (KG1a, Kasumi-1), DNR-sensitive U937 AML cells, and primary CD34⁺AML bone-marrow-derived cells.</p> <p>Methods</p> <p>Primary human CD34⁺cells were isolated from peripheral blood mononuclear cells or bone marrow mononuclear cells using a CD34 MicroBead kit. The growth inhibitory effects of curcumin were evaluated by MTT and colony-formation assays. Cell cycle distribution was examined by propidium iodide (PI) assay. Apoptosis was analyzed by Wright-Giemsa, Hoechst 33342 and Annexin-V/PI staining assays. The change in mitochondrial membrane potential (MMP) was examined by JC-1 staining and flow cytometry. Expression of apoptosis-related proteins was determined by reverse transcription-polymerase chain reaction and Western blotting. Short interfering RNA (siRNA) against <it>Bcl-2 </it>was used in CD34⁺KG1a and Kasumi-1 cells incubated with/without DNR.</p> <p>Results</p> <p>Curcumin inhibited proliferation and induced apoptosis and G1/S arrest in both DNR-insensitive KG1a, Kasumi-1 and DNR-sensitive U937 cells. Curcumin-induced apoptosis was associated with reduced expression of both Bcl-2 mRNA and protein, subsequent loss of MMP, and activation of caspase-3 followed by PARP degradation. Curcumin synergistically enhanced the cytotoxic effect of DNR in DNR-insensitive KG1a and Kasumi-1 cells, consistent with decreased Bcl-2 expression. Accordingly, siRNA against <it>Bcl-2 </it>increased the susceptibility of KG1a and Kasumi-1 cells to DNR-induced apoptosis. More importantly, curcumin suppressed Bcl-2 expression, selectively inhibited proliferation and synergistically enhanced the cytotoxicity of DNR in primary CD34⁺AML cells, while showing limited lethality in normal CD34⁺hematopoietic progenitors.</p> <p>Conclusion</p> <p>Curcumin down-regulates Bcl-2 and induces apoptosis in DNR-insensitive CD34⁺AML cell lines and primary CD34⁺AML cells.</p>