Anti-Leukemic Effects of Small Molecule Inhibitor of c-Myc (10058-F4) on Chronic Myeloid Leukemia Cells.

BACKGROUND: As one of the main molecules in BCR-ABL signaling, c-Myc acts as a pivotal key in disease progression and disruption of long-term remission in patients with CML. OBJECTIVES: To clarify the effects of c-Myc inhibition in CML, we examined the anti-tumor property of a well-known small molecule inhibitor of c-Myc 10058-F4 on K562 cell line. METHODS: This experimental study was conducted in K562 cell line for evaluation of cytotoxic activity of 10058-F4 using Trypan blue and MTT assays. Flow cytometry and Quantitative RT-PCR analysis were also conducted to determine its mechanism of action. Additionally, Annexin/PI staining was performed for apoptosis assessment. RESULTS: The results of Trypan blue and MTT assay demonstrated that inhibition of c-Myc, as shown by suppression of c-Myc expression and its associated genes PP2A, CIP2A, and hTERT, could decrease viability and metabolic activity of K562 cells, respectively. Moreover, a robust elevation in cell population in G1-phase coupled with up-regulation of p21 and p27 expression shows that 10058-F4 could hamper cell proliferation, at least partly, through induction of G1 arrest. Accordingly, we found that 10058-F4 induced apoptosis via increasing Bax and Bad; In contrast, no significant alterations were observed NF-KB pathway-targeted anti-apoptotic genes in the mRNA levels. Notably, disruption of the NF-κB pathway with bortezomib as a common proteasome inhibitor sensitized K562 cells to the cytotoxic effect of 10058-F4, substantiating the fact that the NF-κB axis functions probably attenuate the K562 cells sensitivity to c-Myc inhibition. CONCLUSIONS: It can be concluded from the results of this study that inhibition of c-Myc induces anti-neoplastic effects on CML-derived K562 cells as well as increases the efficacy of imatinib. For further insight into the safety and effectiveness of 10058-F4 in CML, in vivo studies will be required.

C-Myc inhibition sensitizes pre-B ALL cells to the anti-tumor effect of vincristine by altering apoptosis and autophagy: Proposing a probable mechanism of action for 10058-F4.

Unlike the broad spectrum efficacies in wiping the malignant cells out, application of vincristine (VCR) in acute lymphoblastic leukemia (ALL) therapeutic protocol is partially restricted due to its high frequent resistant rate. Although several mechanisms have been enumerated for VCR resistance, to the best of our knowledge, there is no report reflecting the suppressive effect of oncogenic pathways on VCR cytotoxicity in ALL. The results of the present study indicated that both pre-B ALL-derived REH and Nalm-6 cells were partly resistant to VCR, with this note that Nalm-6 cells displayed more resistant phenotype. More interestingly, we showed for the first time that among inhibitors of different signaling pathways including those targeting PI3K, ERK, and NF-κB, the enhancive effect of small molecule inhibitor of c-Myc 10058-F4 was more significant on VCR cytotoxicity. Inhibition of c-Myc in VCR-treated Nalm-6 cells promoted a caspase-3-dependent apoptosis not only through altering the balance between death promoters to death suppressors, but also via modulating the expression of autophagy-related genes. Noteworthy, favorable impact of 10058-F4 on VCR anti-leukemic effect was not restricted to the induction of cell death and this agent also reinforced VCR anti-proliferative effect through disturbing cell cycle progression and hampering the expression of Pin1 and hTERT. In conclusion, it seems that targeting c-Myc could produce a synergistic anti-cancer effect with VCR and provide a fundamental infrastructure for a promising approach in ALL.

Synergistic Effects of PI3K and c-Myc Co-targeting in Acute Leukemia: Shedding New Light on Resistance to Selective PI3K-δ Inhibitor CAL-101.

Enthusiasms into the application of PI3K-δ inhibitor CAL-101 has been muted due to the over-activation of compensatory molecules. Our results delineated that c-Myc suppression using 10058-F4 enhanced CAL-101 cytotoxicity in less sensitive cells through different mechanisms based on p53 status; while CAL-101-plus-10058-F4 induced G1 arrest in wild-type p53-expressing leukemic cells, no conspicuous increase in G1 was noted in U937 cells harboring mutant p53. Conclusively, this study shed lights on the role of c-Myc oncoprotein in acute leukemia cells sensitivity to PI3K inhibitor and outlined that the combination of c-Myc inhibitor and CAL-101 may be a promising therapeutic approach in leukemia.

Suppression of c-Myc using 10058-F4 exerts caspase-3-dependent apoptosis and intensifies the antileukemic effect of vincristine in pre-B acute lymphoblastic leukemia cells.

Despite an old history behind the identification of the leading role of c-Myc in leukemogenesis, the road to constructing a therapeutic perspective for this molecule in acute lymphoblastic leukemia (ALL) is yet mesmerizing. This study was designed to provide a better outlook for the anticancer property of 10058-F4, an appealing inhibitor of c-Myc, in pre-B ALL cell lines either in the context of monotherapy or in combination with chemotherapeutic drugs. Our results declared that abrogation of c-Myc decreased the proliferative capacity of pre-B ALL-derived cells through halting the transition of the cells from G1 phase, and reducing the replicative potential of both REH and Nalm-6 cells, at least partly, through c-Myc-mediated suppression of human telomerase reverse transcriptase. Moreover, 10058-F4 potently induced a caspase-3-dependent apoptosis in pre-B ALL cells via shifting the balance between pro- and anti-apoptotic target genes. Although the inhibition of PI3Kδ using Idelalisib upregulated the messenger RNA expression of autophagy-related genes in 10058-F4-treated cells, treatment with autophagy inhibitor chloroquine decreased viability of the cells, either as a single agent or in combination with Idelalisib and/or 10058-F4; suggesting that the activation of autophagy in pre-B ALL cells could blunt apoptotic events and attenuate anticancer effect of both c-Myc and PI3K inhibitors. Finally, the results of our synergistic experiments delineated that 10058-F4 produced a synergistic effect with vincristine and provided an enhanced therapeutic efficacy in ALL cells, highlighting that c-Myc oncoprotein could be a bona fide target for the treatment of ALL.

Small molecule inhibitor of c-Myc 10058-F4 inhibits proliferation and induces apoptosis in acute leukemia cells, irrespective of PTEN status.

Based on the frequent over-expression of c-Myc in hematologic malignancies and its crucial role in the regulation of diverse oncogenic pathways involved in leukomogenesis, intense interest has recently focused on this factor as an appealing therapeutically target in leukemia. In the present study, we aimed to investigate the anti-leukemic property of small molecule inhibitor of c-Myc 10058-F4 in two distinct acute leukemia cell lines consist of acute promyelocytic leukemia (APL)-derived NB4 cells (with wild-type PTEN) and acute lymphoblastic leukemia (ALL)-derived Nalm-6 cells (with down-regulated PTEN). 10058-F4 effectively reduced survival of leukemic cells; however, we found a different cell sensitivity pattern in the tested cell lines. To the best of our knowledge, no study has addressed the underlying mechanisms responsible for leukemic cell resistance to 10058-F4, and we propose for the first time that the effectiveness of c-Myc inhibition might be attenuated through over-activated phosphoinositide 3-kinase (PI3K) in less sensitive Nalm-6 cells. Notably, we failed to find an obvious correlation between PTEN status and cell sensitivity to the inhibitor in a panel of hematologic malignant cells. Beyond 10058-F4 cytotoxicity as a single agent, synergistic experiments also delineated that pharmaceutical targeting of c-Myc could potentiate the anti-cancer effect of both vincristine and Arsenic trioxide in ALL and APL cells, respectively. In conclusion, this study sheds light on the potent anti-leukemic characteristics of 10058-F4 and provide an interesting evidence to the application of this agent in combination with PI3K inhibitors especially in acute leukemia with over-activated PI3K, irrespective of PTEN status.