Inhibitory effects of Tomivosertib in acute myeloid leukemia

Inhibition of MNK pathway sensitizes nasopharyngeal carcinoma to radiotherapy

Improving the clinical management of nasopharyngeal carcinoma (NPC) is an unmet need owing to the high incidence of treatment failure caused by radioresistance. In our study, we observed increased phosphorylation of translation initiation factor 4E (eIF4E), regulated by MAP kinase-interacting kinase (MNK), in NPC cells following irradiation treatment. Using siRNA to deplete MNK, we found that radiation-induced eIF4E phosphorylation was eliminated, NPC cell sensitivity to radiation was enhanced, and radioresistant NPC cell viability was reduced. Furthermore, we tested three pharmacological MNK inhibitors (eFT508, CGP57380, and cercosporamide) and found that they were effective against radioresistant NPC cells and synergized with irradiation. In-vivo experiments confirmed that eFT508, at a tolerable dose, inhibited the growth of radioresistant NPC and synergized with radiation in a radiosensitive NPC xenograft model. Our research highlights the activation of MNK-mediated survival mechanisms in NPC in response to radiotherapy and the potential of combining radiation with MNK inhibitors as a sensitizing strategy. Notably, eFT508 is currently being investigated in clinical trials for cancer treatment, and our findings may prompt the initiation of clinical trials using eFT508 in radioresistant NPC patients.

Molecular targeting of the UDP-glucuronosyltransferase enzymes in high-eukaryotic translation initiation factor 4E refractory/relapsed acute myeloid leukemia patients: a randomized phase II trial of vismodegib, ribavirin with or without decitabine

Drug resistance underpins poor outcomes in many malignancies including refractory and relapsed acute myeloid leukemia (R/R AML). Glucuronidation is a common mechanism of drug inactivation impacting many AML therapies, e.g., cytarabine, decitabine, azacytidine and venetoclax. In AML cells, the capacity for glucuronidation arises from increased production of the UDP-glucuronosyltransferase 1A (UGT1A) enzymes. UGT1A elevation was first observed in AML patients who relapsed after response to ribavirin, a drug used to target the eukaryotic translation initiation factor eIF4E, and subsequently in patients who relapsed on cytarabine. UGT1A elevation resulted from increased expression of the sonic-hedgehog transcription factor GLI1. Vismodegib inhibited GLI1, decreased UGT1A levels, reduced glucuronidation of ribavirin and cytarabine, and re-sensitized cells to these drugs. Here, we examined if UGT1A protein levels, and thus glucuronidation activity, were targetable in humans and if this corresponded to clinical response. We conducted a phase II trial using vismodegib with ribavirin, with or without decitabine, in largely heavily pre-treated patients with high-eIF4E AML. Pre-therapy molecular assessment of patients' blasts indicated highly elevated UGT1A levels relative to healthy volunteers. Among patients with partial response, blast response or prolonged stable disease, vismodegib reduced UGT1A levels, which corresponded to effective targeting of eIF4E by ribavirin. In all, our studies are the first to demonstrate that UGT1A protein, and thus glucuronidation, are targetable in humans. These studies pave the way for the development of therapies that impair glucuronidation, one of the most common drug deactivation modalities. Clinicaltrials.gov: NCT02073838.

Combination Therapies with Kinase Inhibitors for Acute Myeloid Leukemia Treatment

Targeting kinase activity is considered to be an attractive therapeutic strategy to overcome acute myeloid leukemia (AML) since aberrant activation of the kinase pathway plays a pivotal role in leukemogenesis through abnormal cell proliferation and differentiation block. Although clinical trials for kinase modulators as single agents remain scarce, combination therapies are an area of therapeutic interest. In this review, the author summarizes attractive kinase pathways for therapeutic targets and the combination strategies for these pathways. Specifically, the review focuses on combination therapies targeting the FLT3 pathways, as well as PI3K/AKT/mTOR, CDK and CHK1 pathways. From a literature review, combination therapies with the kinase inhibitors appear more promising than monotherapies with individual agents. Therefore, the development of efficient combination therapies with kinase inhibitors may result in effective therapeutic strategies for AML.

An Aptamer against MNK1 for Non-Small Cell Lung Cancer Treatment

Lung cancer is the leading cause of cancer-related death worldwide. Its late diagnosis and consequently poor survival make necessary the search for new therapeutic targets. The mitogen-activated protein kinase (MAPK)-interacting kinase 1 (MNK1) is overexpressed in lung cancer and correlates with poor overall survival in non-small cell lung cancer (NSCLC) patients. The previously identified and optimized aptamer from our laboratory against MNK1, apMNKQ2, showed promising results as an antitumor drug in breast cancer in vitro and in vivo. Thus, the present study shows the antitumor potential of apMNKQ2 in another type of cancer where MNK1 plays a significant role, such as NSCLC. The effect of apMNKQ2 in lung cancer was studied with viability, toxicity, clonogenic, migration, invasion, and in vivo efficacy assays. Our results show that apMNKQ2 arrests the cell cycle and reduces viability, colony formation, migration, invasion, and epithelial-mesenchymal transition (EMT) processes in NSCLC cells. In addition, apMNKQ2 reduces tumor growth in an A549-cell line NSCLC xenograft model. In summary, targeting MNK1 with a specific aptamer may provide an innovative strategy for lung cancer treatment.

MNK Proteins as Therapeutic Targets in Leukemia

In leukemia, resistance to therapy is a major concern for survival. MAPK-interacting kinases (MNKs) have been identified as important activators of oncogenic-related signaling and may be mediators of resistance. Recent studies in leukemia models, especially acute myeloid leukemia (AML), have focused on targeting MNKs together with other inhibitors or treating chemotherapy-resistant cells with MNK inhibitors. The preclinical demonstrations of the efficacy of MNK inhibitors in these combination formats would suggest a promising potential for use in clinical trials. Optimizing MNK inhibitors and testing in leukemia models is actively being pursued and may have important implications for the future. These studies are furthering the understanding of the mechanisms of MNKs in cancer which could translate to clinical studies.

MAPK-interacting kinases inhibition by eFT508 overcomes chemoresistance in preclinical model of osteosarcoma

The MAPK-interacting kinases 1 and 2 (MNK1/2) have generated increasing interest as therapeutic targets for many cancers with little known in osteosarcoma. This study evaluated the efficacy of eFT508, a highly selective inhibitor of MNK1/2, as single drug alone and in combination with paclitaxel in preclinical models of osteosarcoma. EFT508 is active against multiple osteosarcoma cell lines via inhibiting growth, survival and migration. It also demonstrates anti-osteosarcoma selectivity with much less toxicity on normal osteoblastic than osteosarcoma cells. Consistent with in vitro findings, eFT508 at non-toxic dose significantly arrested tumor growth in mice throughout the whole duration of treatment. Mechanistically, eEFT508 is highly effective in blocking eIF4E phosphorylation and eIF4E-mediated protein translation. Combination index shows that eFT508 and paclitaxel is synergistic in osteosarcoma cells. Our findings highlight the therapeutic value of MNK1/2 inhibition and suggest eFT508 as a promising candidate for the treatment of osteosarcoma.

Inhibition MNK-eIF4E-β-catenin preferentially sensitizes gastric cancer to chemotherapy

Aberrant activation of eIF4E contributes to gastric cancer growth and resistance. MAPK-interacting kinases (MNKs) regulate eIF4E phosphorylation and activity in tumor but not normal cells and are potentially safe targets for the treatment of various cancers. Our work reveals that tomivosertib, a potent and highly selective dual MNK1/2 inhibitor, preferentially sensitizes gastric cancer to chemotherapy via suppressing MNK-eIF4E-β-catenin. We firstly demonstrate that tomivosertib displays higher efficacy than other MNK inhibitors in inhibiting gastric cancer cells. In addition, tomivosertib significantly augments the inhibitory effects of 5-FU and paclitaxel but not everolimus, suggesting that tomivosertib preferentially sensitizes gastric cancer to chemotherapy. We next show that eIF4E overexpression and phosphorylation coordinately regulate β-catenin signaling in gastric cancer. Rescue studies confirm that tomivosertib inhibits gastric cancer via targeting MNK- eIF4E-β-catenin. Finally, we demonstrate that the in vitro functional and mechanism observations are translatable to in vivo gastric cancer model in mice. Tomivosertib is now in Phase 2 clinical trials. Our study provides preclinical evidence to initialize clinical trials for gastric cancer using tomivosertib in combination with chemotherapy.