Figure 1: AICAR treatment inhibits proliferation of human childhood leukemia ALL cells. The ALL cell lines CCRF-CEM (T-lineage), NALM6 (Bp-lineage), REH (Bp-ALL expressing the TEL/AML1 fusion protein), and SupB15 (Bp-ALL expressing the BCR/ABL fusion protein) were treated for 24 h with various concentrations of AICAR (0.25 – 2 mM), and cell growth analyzed by thymidine ribotide ([3H]TdR) incorporation into DNA. The results are expressed as percentage of [3H]thymidine uptake (%) relative to control values (mean ± SEM, n = 3). #, p < 0.001 for AICAR-treated cells vs. control.

Mentions: We investigated the effect of AICAR on the growth of CCRF-CEM, NALM6, REH, and SupB15 ALL cells. REH and SupB15 cell lines were used as models for B-precursor ALL sensitive and resistant phenotypes, respectively. Cells were treated with various concentrations of AICAR (0.25 to 1.0 mM) for 24 h, and growth was examined by [3H]thymidine uptake assays. As shown in Figure 1, AICAR inhibited the growth of CCRF-CEM, NALM6, and REH in a dose-dependent manner at all doses studied (p < 0.001, cells treated with AICAR vs. untreated/control cells). SupB15 cells, which harbor the BCR/ABL translocation, were relatively resistant to lower concentrations of AICAR, but exhibited significant growth inhibition when treated with higher concentrations of AICAR (p < 0.001, cells treated with 0.5 to 2.0 mM AICAR vs. untreated/control cells).

Sengupta TK, Leclerc GM, Hsieh-Kinser TT, Leclerc GJ, Singh I, Barredo JC - Mol. Cancer (2007)

Bottom Line: These effects were abolished by treatment with the adenosine kinase inhibitor 5'-iodotubericidin prior to addition of AICAR indicating that AICAR's cytotoxicity is mediated through AMPK activation.Additionally, AICAR treatment resulted in phosphorylation of Akt suggesting that activation of the PI3K/Akt pathway may represent a compensatory survival mechanism in response to apoptosis and/or cell cycle arrest.Combined treatment with AICAR and the mTOR inhibitor rapamycin resulted in additive anti-proliferative activity ALL cells.AICAR-mediated AMPK activation was found to be a proficient cytotoxic agent in ALL cells and the mechanism of its anti-proliferative and apoptotic effect appear to be mediated via activation of p38-MAPK pathway, increased expression of cell cycle inhibitory proteins p27 and p53, and downstream effects on the mTOR pathway, hence exhibiting therapeutic potential as a molecular target for the treatment of childhood ALL.

Affiliation: School of Life Sciences, Indian Institute of Science Education and Research, Kolkata, India. senguptk@yahoo.com

Abstract: Acute lymphoblastic leukemia (ALL) is the most common hematological malignancy affecting children. Despite significant progress and success in the treatment of ALL, a significant number of children continue to relapse and for them, outcome remains poor. Therefore, the search for novel therapeutic approaches is warranted. The aim of this study was to investigate the AMP activated protein kinase (AMPK) as a potential target in childhood acute lymphoblastic leukemia (ALL) subtypes characterized by non-random translocation signature profiles. We evaluated the effects of the AMPK activator AICAR on cell growth, cell cycle regulators and apoptosis of various childhood ALL cells.We found that treatment with AICAR inhibited cell proliferation, induced cell cycle arrest in G1-phase, and apoptosis in CCRF-CEM (T-ALL), NALM6 (Bp-ALL), REH (Bp-ALL, TEL/AML1) and SupB15 (Bp-ALL, BCR/ABL) cells. These effects were abolished by treatment with the adenosine kinase inhibitor 5'-iodotubericidin prior to addition of AICAR indicating that AICAR's cytotoxicity is mediated through AMPK activation. Moreover, we determined that growth inhibition exerted by AICAR was associated with activation of p38-MAPK and increased expression of the cell cycle regulators p27 and p53. We also demonstrated that AICAR mediated apoptosis through the mitochondrial pathway as revealed by the release of cytochrome C and cleavage of caspase 9. Additionally, AICAR treatment resulted in phosphorylation of Akt suggesting that activation of the PI3K/Akt pathway may represent a compensatory survival mechanism in response to apoptosis and/or cell cycle arrest. Combined treatment with AICAR and the mTOR inhibitor rapamycin resulted in additive anti-proliferative activity ALL cells.AICAR-mediated AMPK activation was found to be a proficient cytotoxic agent in ALL cells and the mechanism of its anti-proliferative and apoptotic effect appear to be mediated via activation of p38-MAPK pathway, increased expression of cell cycle inhibitory proteins p27 and p53, and downstream effects on the mTOR pathway, hence exhibiting therapeutic potential as a molecular target for the treatment of childhood ALL. Therefore, activation of AMPK by AICAR represents a novel approach to targeted therapy, and suggests a role for AICAR in combination therapy with inhibitors of the PI3K/Akt/mTOR pathways for the treatment of childhood in ALL.