Telomerase inhibition on acute myeloid leukemia stem cell induced apoptosis with both intrinsic and extrinsic pathways

Acute Myeloid Leukemia (AML) is an invasive and lethal blood cancer caused by a rare population of Leukemia Stem Cells (LSCs). Telomerase activation is a limitless self-renewal process in LSCs. Apart from telomerase role in telomere lengthening, telomerase (especially hTERT subunit) inhibits intrinsic-, extrinsic-, and p53- mediated apoptosis pathways. In this study, the effect of Telomerase Inhibition (TI) on intrinsic-, extrinsic-, p53-mediated apoptosis, and DNMT3a and TET epigenetic markers in stem (CD34⁺) and differentiated (CD34^-) AML cells is evaluated.

High-purity CD34⁺ (primary AML and KG-1a) cells were enriched using the Magnetic-Activated Cell Sorting (MACS) system. CD34⁺ and CD34^- (primary AML and KG-1a) cells were treated with BIBR1532 and then, MTT assay, Annexin V/7AAD, Ki-67 assay, Telomere Length (TL) measurement, and transcriptional alterations of p53, hTERT, TET2, DNMT3a were analyzed. Finally, apoptosis-related genes and proteins were studied.

TI with the IC50 values of 83.5, 33.2, 54.3, and 24.6 μM in CD34⁺ and CD34^- (primary AML and KG-1a) cells significantly inhibited cell proliferation and induced apoptosis. However, TI had no significant effect on TL. The results also suggested TI induced intrinsic-, extrinsic-, and p53-mediated apoptosis. It was shown that the expression levels of DNMT3a and TET2 epigenetic markers were highly increased following TI.

In total, it was revealed that TI induced apoptosis through intrinsic, extrinsic, and p53 pathways and increased the expression of DNMT3a and TET2 epigenetic markers.