Sirolimus enhances remission induction in patients with high risk acute myeloid leukemia and mTORC1 target inhibition

Targeting Molecular Signaling Pathways and Cytokine Responses to Modulate c-MYC in Acute Myeloid Leukemia

Overexpression of the MYC oncogene, encoding c-MYC protein, contributes to the pathogenesis and drug resistance of acute myeloid leukemia (AML) and many other hematopoietic malignancies. Although standard chemotherapy has predominated in AML therapy over the past five decades, the clinical outcomes and patient response to treatment remain suboptimal. Deeper insight into the molecular basis of this disease should facilitate the development of novel therapeutics targeting specific molecules and pathways that are dysregulated in AML, including fms-like tyrosine kinase 3 (FLT3) gene mutation and cluster of differentiation 33 (CD33) protein expression. Elevated expression of c-MYC is one of the molecular features of AML that determines the clinical prognosis in patients. Increased expression of c-MYC is also one of the cytogenetic characteristics of drug resistance in AML. However, direct targeting of c-MYC has been challenging due to its lack of binding sites for small molecules. In this review, we focused on the mechanisms involving the bromodomain and extra-terminal (BET) and cyclin-dependent kinase 9 (CDK9) proteins, phosphoinositide-Akt-mammalian target of rapamycin (PI3K/AKT/mTOR) and Janus kinase-signal transduction and activation of transcription (JAK/STAT) pathways, as well as various inflammatory cytokines, as an indirect means of regulating MYC overexpression in AML. Furthermore, we highlight Food and Drug Administration (FDA)-approved drugs for AML, and the results of preclinical and clinical studies on novel agents that have been or are currently being tested for efficacy and tolerability in AML therapy. Overall, this review summarizes our current knowledge of the molecular processes that promote leukemogenesis, as well as the various agents that intervene in specific pathways and directly or indirectly modulate c-MYC to disrupt AML pathogenesis and drug resistance.

Signaling effect, combinations, and clinical applications of triciribine

Triciribine (TCN) is a tricyclic nucleoside. Its synthesis was first described in 1971. Subsequent studies have indicated that TCN plays a role in inhibiting DNA synthesis and was revealed to possess a higher selectivity for Akt. Although a single dose of TCN demonstrated limited activity in solid tumors at the clinical level, combinations of TCN with various agents, such as specific inhibitors, tyrosine kinase inhibitor dasatinib, ErbB inhibitor tipifarnib, IGF1-R inhibitor NVP-AEW541, mTORC1 inhibitor RAD-001, TNF-related apoptosis-inducing ligand, PPARγ agonist, 1,25(OH)2D3, gemcitabine, and paclitaxel, have been reported to be efficient against various malignancies such as pancreatic, breast, prostate cancer, insulinoma, gut neuroendocrine tumor, and hepatocellular carcinoma at the preclinical level. Other than malignancies, through Akt inhibition activity, TCN has also been demonstrated potential for treating lung injuries, including those encountered in COVID-19 infections.

Identification of triciribine as a novel myeloid cell differentiation inducer

Differentiation therapy using all-trans retinoic acid (ATRA) for acute promyelocytic leukemia (APL) is well established. However, because the narrow application and tolerance development of ATRA need to be improved, we searched for another efficient myeloid differentiation inducer. Kinase activation is involved in leukemia biology and differentiation block. To identify novel myeloid differentiation inducers, we used a Kinase Inhibitor Screening Library. Using a nitroblue tetrazolium dye reduction assay and real-time quantitative PCR using NB4 APL cells, we revealed that, PD169316, SB203580, SB202190 (p38 MAPK inhibitor), and triciribine (TCN) (Akt inhibitor) potently increased the expression of CD11b. We focused on TCN because it was reported to be well tolerated by patients with advanced hematological malignancies. Nuclear/cytoplasmic (N/C) ratio was significantly decreased, and myelomonocytic markers (CD11b and CD11c) were potently induced by TCN in both NB4 and acute myeloid leukemia (AML) M2 derived HL-60 cells. Western blot analysis using NB4 cells demonstrated that TCN promoted ERK1/2 phosphorylation, whereas p38 MAPK phosphorylation was not affected, suggesting that activation of the ERK pathway is involved in TCN-induced differentiation. We further examined that whether ATRA may affect phosphorylation of ERK and p38, and found that there was no obvious effect, suggesting that ATRA induced differentiation is different from TCN effect. To reveal the molecular mechanisms involved in TCN-induced differentiation, we performed microarray analysis. Pathway analysis using DAVID software indicated that "hematopoietic cell lineage" and "cytokine-cytokine receptor interaction" pathways were enriched with high significance. Real-time PCR analysis demonstrated that components of these pathways including IL1β, CD3D, IL5RA, ITGA6, CD44, ITGA2B, CD37, CD9, CSF2RA, and IL3RA, were upregulated by TCN-induced differentiation. Collectively, we identified TCN as a novel myeloid cell differentiation inducer, and trials of TCN for APL and non-APL leukemia are worthy of exploration in the future.

PI3K/Akt/mTOR Signaling Pathway in Blood Malignancies-New Therapeutic Possibilities

Blood malignancies remain a therapeutic challenge despite the development of numerous treatment strategies. The phosphatidylinositol-3 kinase (PI3K)/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) signaling pathway plays a central role in regulating many cellular functions, including cell cycle, proliferation, quiescence, and longevity. Therefore, dysregulation of this pathway is a characteristic feature of carcinogenesis. Increased activation of PI3K/Akt/mTOR signaling enhances proliferation, growth, and resistance to chemo- and immunotherapy in cancer cells. Overactivation of the pathway has been found in various types of cancer, including acute and chronic leukemia. Inhibitors of the PI3K/Akt/mTOR pathway have been used in leukemia treatment since 2014, and some of them have improved treatment outcomes in clinical trials. Recently, new inhibitors of PI3K/Akt/mTOR signaling have been developed and tested both in preclinical and clinical models. In this review, we outline the role of the PI3K/Akt/mTOR signaling pathway in blood malignancies' cells and gather information on the inhibitors of this pathway that might provide a novel therapeutic opportunity against leukemia.

A Phase I Trial of Sirolimus with "7&3" Induction Chemotherapy in Patients with Newly Diagnosed Acute Myeloid Leukemia

Chemotherapy remains a primary treatment for younger AML patients, though many relapse. Data from our group have shown that highly phosphorylated S6 in blasts may predict response to sirolimus given with chemotherapy. We report the results of a phase I study of this combination in newly diagnosed AML and the pharmacodynamic analysis of pS6 before and after treatment. Subjects received sirolimus (12 mg on day 1, 4 mg daily, days 2-10), then idarubicin and cytarabine (days 4-10). Response was assessed at hematologic recovery or by day 42 using a modified IWG criteria. Fifty-five patients received sirolimus. Toxicity was similar to published 7 + 3 data, and 53% had high-, 27% intermediate-, and 20% favorable-risk disease. Forty-four percent of the high-risk patients entered into CR/CRp. Seventy-nine percent of the intermediate-risk subjects had a CR/CRp. All favorable-risk patients had a CR by day 42; 9/11 remained alive and in remission with a median follow-up of 660 days. Additionally, 41/55 patients had adequate samples for pharmacodynamic analysis. All patients demonstrated activation of S6 prior to therapy, in contrast to 67% seen in previous studies of relapsed AML. mTORC1 inhibition was observed in 66% of patients without enrichment among patients who achieved remission. We conclude that sirolimus and 7 + 3 is a well-tolerated and safe regimen. mTORC1 appears to be activated in almost all patients at diagnosis of AML. Inhibition of mTORC1 did not differ based on response, suggesting that AML cells may have redundant signaling pathways that regulate chemosensitivity in the presence of mTORC1 inhibition.

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.

Targeting regulated cell death pathways in acute myeloid leukemia

The use of the BCL2 inhibitor venetoclax has transformed the management of patients with acute myeloid leukemia (AML) who are ineligible for intensive chemotherapy. By triggering intrinsic apoptosis, the drug is an excellent illustration of how our greater understanding of molecular cell death pathways can be translated into the clinic. Nevertheless, most venetoclax-treated patients will relapse, suggesting the need to target additional regulated cell death pathways. To highlight advances in this strategy, we review the recognized regulated cell death pathways, including apoptosis, necroptosis, ferroptosis and autophagy. Next, we detail the therapeutic opportunities to trigger regulated cell death in AML. Finally, we describe the main drug discovery challenges for regulated cell death inducers and their translation into clinical trials. A better knowledge of the molecular pathways regulating cell death represents a promising strategy to develop new drugs to cure resistant or refractory AML patients, particularly those resistant to intrinsic apoptosis.

The dual role of autophagy in acute myeloid leukemia

Acute myeloid leukemia (AML) is a severe hematologic malignancy prevalent in older patients, and the identification of potential therapeutic targets for AML is problematic. Autophagy is a lysosome-dependent catabolic pathway involved in the tumorigenesis and/or treatment of various cancers. Mounting evidence has suggested that autophagy plays a critical role in the initiation and progression of AML and anticancer responses. In this review, we describe recent updates on the multifaceted functions of autophagy linking to genetic alterations of AML. We also summarize the latest evidence for autophagy-related genes as potential prognostic predictors and drivers of AML tumorigenesis. We then discuss the crosstalk between autophagy and tumor cell metabolism into the impact on both AML progression and anti-leukemic treatment. Moreover, a series of autophagy regulators, i.e., the inhibitors and activators, are described as potential therapeutics for AML. Finally, we describe the translation of autophagy-modulating therapeutics into clinical practice. Autophagy in AML is a double-edged sword, necessitating a deeper understanding of how autophagy influences dual functions in AML tumorigenesis and anti-leukemic responses.

Imaging dynamic mTORC1 pathway activity in vivo reveals marked shifts that support time-specific inhibitor therapy in AML

Acute myeloid leukemia (AML) is a high remission, high relapse fatal blood cancer. Although mTORC1 is a master regulator of cell proliferation and survival, its inhibitors have not performed well as AML treatments. To uncover the dynamics of mTORC1 activity in vivo, fluorescent probes are developed to track single cell proliferation, apoptosis and mTORC1 activity of AML cells in the bone marrow of live animals and to quantify these activities in the context of microanatomical localization and intra-tumoral heterogeneity. When chemotherapy drugs commonly used clinically are given to mice with AML, apoptosis is rapid, diffuse and not preferentially restricted to anatomic sites. Dynamic measurement of mTORC1 activity indicated a decline in mTORC1 activity with AML progression. However, at the time of maximal chemotherapy response, mTORC1 signaling is high and positively correlated with a leukemia stemness transcriptional profile. Cell barcoding reveals the induction of mTORC1 activity rather than selection of mTORC1 high cells and timed inhibition of mTORC1 improved the killing of AML cells. These data define the real-time dynamics of AML and the mTORC1 pathway in association with AML growth, response to and relapse after chemotherapy. They provide guidance for timed intervention with pathway-specific inhibitors.

The role of mTORC1 in AML has not yet been proven due to the mixed results of its inhibitors in clinical trials. Here the authors show the real-time dynamics of the mTORC1 pathway in association with AML growth and response to chemotherapy with fluorescent markers, providing guidance for timed intervention with pathway-specific inhibitors.

The Role of mTOR Inhibitors in Hematologic Disease: From Bench to Bedside

The mTOR pathway plays a central role in many cellular processes, such as cellular growth, protein synthesis, glucose, and lipid metabolism. Aberrant regulation of mTOR is a hallmark of many cancers, including hematological malignancies. mTOR inhibitors, such as Rapamycin and Rapamycin analogs (Rapalogs), have become a promising class of agents to treat malignant blood diseases-either alone or in combination with other treatment regimens. This review highlights experimental evidence underlying the molecular mechanisms of mTOR inhibitors and summarizes their evolving role in the treatment of hematologic disease, including leukemia, lymphoma, myeloma, immune hemocytopenia, and graft-versus-host disease (GVHD). Based on data presented in this review, we believe that mTOR inhibitors are becoming a trusted therapeutic in the clinical hematologist's toolbelt and should be considered more routinely in combination therapy for the management of hematologic disease.

Drug Repurposing for COVID-19 using Graph Neural Network with Genetic, Mechanistic, and Epidemiological Validation

Amid the pandemic of 2019 novel coronavirus disease (COVID-19) infected by SARS-CoV-2, a vast amount of drug research for prevention and treatment has been quickly conducted, but these efforts have been unsuccessful thus far. Our objective is to prioritize repurposable drugs using a drug repurposing pipeline that systematically integrates multiple SARS-CoV-2 and drug interactions, deep graph neural networks, and in-vitro/population-based validations. We first collected all the available drugs (n= 3,635) involved in COVID-19 patient treatment through CTDbase. We built a SARS-CoV-2 knowledge graph based on the interactions among virus baits, host genes, pathways, drugs, and phenotypes. A deep graph neural network approach was used to derive the candidate drug’s representation based on the biological interactions. We prioritized the candidate drugs using clinical trial history, and then validated them with their genetic profiles, in vitro experimental efficacy, and electronic health records. We highlight the top 22 drugs including Azithromycin, Atorvastatin, Aspirin, Acetaminophen, and Albuterol. We further pinpointed drug combinations that may synergistically target COVID-19. In summary, we demonstrated that the integration of extensive interactions, deep neural networks, and rigorous validation can facilitate the rapid identification of candidate drugs for COVID-19 treatment. This paper had been uploaded to arXiv : https://arxiv.org/abs/2009.10931.

Targeting PI3K/Akt/mTOR in AML: Rationale and Clinical Evidence

Acute myeloid leukemia (AML) is a highly heterogeneous hematopoietic malignancy characterized by excessive proliferation and accumulation of immature myeloid blasts in the bone marrow. AML has a very poor 5-year survival rate of just 16% in the UK; hence, more efficacious, tolerable, and targeted therapy is required. Persistent leukemia stem cell (LSC) populations underlie patient relapse and development of resistance to therapy. Identification of critical oncogenic signaling pathways in AML LSC may provide new avenues for novel therapeutic strategies. The phosphatidylinositol-3-kinase (PI3K)/Akt and the mammalian target of rapamycin (mTOR) signaling pathway, is often hyperactivated in AML, required to sustain the oncogenic potential of LSCs. Growing evidence suggests that targeting key components of this pathway may represent an effective treatment to kill AML LSCs. Despite this, accruing significant body of scientific knowledge, PI3K/Akt/mTOR inhibitors have not translated into clinical practice. In this article, we review the laboratory-based evidence of the critical role of PI3K/Akt/mTOR pathway in AML, and outcomes from current clinical studies using PI3K/Akt/mTOR inhibitors. Based on these results, we discuss the putative mechanisms of resistance to PI3K/Akt/mTOR inhibition, offering rationale for potential candidate combination therapies incorporating PI3K/Akt/mTOR inhibitors for precision medicine in AML.

Relapsed or primary refractory AML: moving past MEC and FLAG-ida

PURPOSE OF REVIEW

Treatment of relapsed and refractory acute myeloid leukemia (AML) is still very challenging, with poor response rates and low chance for cure. This is especially true when treating patients who are elderly, have multiple comorbidities, or who are too unfit for traditional salvage chemotherapy regimens.

RECENT FINDINGS

Recently, advances in the treatment of relapsed/refractory AML utilizing novel chemotherapy combinations, hypomethylating, and targeted therapies have shown promising results.

SUMMARY

Several early-phase studies with novel targeted therapy combinations have demonstrated encouraging results warranting larger, comparative studies. This has expanded the access of treatment for patients with relapsed/refractory AML who cannot receive traditional salvage chemotherapy. These newer treatments have the potential to outperform traditional chemotherapy as well.

Mechanistic target of rapamycin inhibitors: successes and challenges as cancer therapeutics

Delineating the contributions of specific cell signalling cascades to the development and maintenance of tumours has greatly informed our understanding of tumorigenesis and has advanced the modern era of targeted cancer therapy. It has been revealed that one of the key pathways regulating cell growth, the phosphatidylinositol 3-kinase/mechanistic target of rapamycin (PI3K/mTOR) signalling axis, is commonly dysregulated in cancer. With a specific, well-tolerated inhibitor of mTOR available, the impact of inhibiting this pathway at the level of mTOR has been tested clinically. This review highlights some of the promising results seen with mTOR inhibitors in the clinic and assesses some of the challenges that remain in predicting patient outcome following mTOR-targeted therapy.

Dually Efficacious Medicine Against Fibrosis and Cancer

Although there is a contemporary consensus of managing a severe disease with multi-targeted approach-based therapeutic combinations, it should not be ignored that certain patho-biological pathways are shared by distinct medical conditions and can be exploited to develop an exceptional type of medication conferring a dual efficacy. This article thus presents a spectrum of emerging molecular targets that substantially contribute to the pathogenesis of both fibrotic and neoplastic disorders, including kinase activities, cytokine cascades, and protein dynamics among others. Moreover, recently approved therapeutic agents in this regard have been sorted out to corroborate the drug’s ability upon targeting each one of these molecular pathways to treat fibrosis and cancer simultaneously. It not only streamlines an overlapping mechanistic profile in the pathogenesis across these two medical conditions, but also inspires clinicians and pharmaceutical innovation to tackle concomitant diseases, such as fibrosis and cancer, with an optimally efficacious medication.