PI3K/mTOR dual-inhibition with VS-5584 enhances anti-leukemic efficacy of ponatinib in blasts and Ph-negative LSCs of chronic myeloid leukemia.

Ponatinib is used for advanced treatment of chronic myeloid leukemia (CML), although low doses to prevent side effects do not suppress survival pathways and eradicate leukemia stem cells (LSCs). We evaluated the potential of ponatinib and PI3K/mTOR dual-inhibitor VS-5584 combination (PoVS) therapy to increase the anti-leukemic effects of ponatinib and investigated the underlying mechanisms at the molecular level. We measured the cytotoxicities of ponatinib, VS-5584, and PoVS (CCK-8 assay), and used the median-effect equation for combination analyses. We investigated the effects of inhibitory concentrations on apoptosis, cell viability and cell-cycle regulation (flow cytometry), protein levels (ELISA, Western blot), transcriptional activities (dual-luciferase reporter assay), gene expressions (qRT-PCR). VS-5584 exerted selective cytotoxic effects against CML and LSC cell lines. VS-5584 inhibited the PI3K/Akt/mTOR pathway, resulting in reduced cell viability, slightly induced caspase-independent apoptosis, prominent G0/G1 cell-cycle blockade that is not a consequence of quiescence. Normal hematopoietic stem cell line was the least affected. Moreover, ponatinib and VS-5584 mediated synergistic anti-leukemic effects on leukemic cells. VS-5584 reduced the ponatinib dose required to target leukemic cells. PoVS treatment inhibited PI3K/Akt/mTOR pathway more consistently than either of the two agents alone through reducing p-Akt, p-mTOR, p-S6K, p-PRAS40, p-S6. The subsequent downstream effects were an increase in C/EBP transcriptional activity and decreases in activities of E2F/DP1, Myc/Max, CREB, STAT3, NFκB, AP-1, Elk-1/SRF. Transcriptional regulation resulted in alterations in the expression levels of target mRNAs. Our results highlight PoVS can be a promising treatment strategy for eliminating CML cells and LSCs selectively, with the reduced ponatinib doses.

Comparative effect of imatinib and ponatinib on autophagy and miRNome in chronic myeloid leukemia.

BCR-ABL tyrosine kinase inhibitors (TKIs) are selective therapies for the patients with Chronic Myeloid Leukemia (CML). Imatinib and ponatinib have remarkable long-term efficacy on a major molecular response. Although TKI related induction of cytotoxicity and apoptosis have been clearly investigated in molecular levels, their comparative effect on autophagy and miRNome are largely unknown. This study aimed to investigate the involvement of alterations of miRNA expressions in CML progression, and how imatinib and ponatinib affect this process, by comparing CML, imatinib-resistant CML and leukemia stem cells (LSC). Cytotoxicity analysis was conducted by WST-1, apoptosis was evaluated by AnnexinV, autophagy was analyzed by Tb/GFP TR-FRET LC3B assay and changes in miRNomes were evaluated with microarray method. Ponatinib showed higher cytotoxicity and apoptosis at far fewer concentrations than imatinib. Both imatinib and ponatinib was able to trigger autophagy in imatinib-resistant K562ima3 cell line but not in LSC. We pointed that imatinib and ponatinib caused significant miRNA profile alterations, especially in the expressions of miR-214-pre, miR-218, miR-19a-5p, miR-19b-1-5p, miR-27b-pre, miR-23b-pre, miR-320e, miR-200a-pre, miR-508-3p, miR-33-pre and miR-766. This study is the first comparative miRNome analysis of CML, resistant CML and LSCs following the imatinib or ponatinib treatment and may guide to identify new markers for diagnosis, follow-up of the disease and to develop novel therapeutic strategies if supported by preclinical studies.

The effect of tomatine on metastasis related matrix metalloproteinase (MMP) activities in breast cancer cell model.

Breast cancer is one of the most common malignancies in women and metastasis is the cause of morbidity and mortality in patients. In the development of metastasis, the matrix metalloproteinase (MMP) family has a very important role in tumor development. MMP-2 and MMP-9 work together for extracellular matrix (ECM) cleavage to increase migration. Tomatine is a secondary metabolite that has a natural defense role against plants, fungi, viruses and bacteria that are synthesized from tomato. In addition, tomatine is also known that it breaks down the cell membrane and is a strong inhibitor in human cancer cells. In this study, it was aimed to evaluate the effect of tomatine on cytotoxicity, apoptosis and matrix metalloproteinase inhibition in MCF-7 cell lines. Human breast cancer cell line (MCF-7) was used as a cell line. In MCF-7 cells, the IC50 dose of tomatine was determined to be 7.07µM. According to the control cells, apoptosis increased 3.4 fold in 48thh. Activation of MMP-2, MMP-9 and MMP-9\NGAL has been shown to decrease significantly in cells treated with tomatine by gelatin zymography compared to the control. As a result, matrix metalloproteinase activity and cell proliferation were suppressed by tomatine and this may provide support in treatment methods.