Chemical derivatization leads to the discovery of novel analogs of azotochelin, a natural siderophore, as promising anticancer agents

Siderophores are structurally unique medicinal natural products and exhibit considerable therapeutic potential. Herein, we report the design and synthesis of azotochelin, a natural siderophore, and an extensive library of azotochelin analogs as a potential anticancer agent. We modified the carboxylic acid and the aromatic ring motifs of azotochelin using various chemical motifs. We tested the compounds against six different cancer cell lines (KB-3-1, SNB-19, MCF-7, K-562, SW-620, and NCI-H460) and a non-cancerous cell line (HEK-293) to assess the cytotoxicity. Among the twenty compounds tested, the IC50 values of eight compounds (14, 32, 35-40, and 54) were between 0.7 to 2.0 μM against a lung cancer cell line (NCI-H460). Moreover, several compounds had a good cytotoxicity profile (IC50 < 10 μM) against many tested cancer cell lines. The flow cytometry analysis showed that compounds 36 and 38 induce apoptosis in NCI-H460 in a dose-dependent manner. The cell cycle analysis indicated that compounds 36 and 38 significantly arrest the cell cycle at the S phase to block cancer cell proliferation in the NCI-H460 cell line. The study has produced various novel azotochelin analogs that are potentially effective anticancer agents and leads for further synthetic and medicinal chemistry exploration.

Direct Targeting of the Raf-MEK-ERK Signaling Cascade Inhibits Neuroblastoma Growth

The Raf-MEK-ERK signaling network has been the subject of intense research due to its role in the development of human cancers, including pediatric neuroblastoma (NB). MEK and ERK are the central components of this signaling pathway and are attractive targets for cancer therapy. Approximately 3–5% of the primary NB samples and about 80% of relapsed samples contain mutations in the Raf-MEK-ERK pathway. In the present study, we analyzed the NB patient datasets and revealed that high RAF and MEK expression leads to poor overall survival and directly correlates with cancer progression and relapse. Further, we repurposed a specific small-molecule MEK inhibitor CI-1040 to inhibit the Raf-MEK-ERK pathway in NB. Our results show that CI-1040 potently inhibits NB cell proliferation and clonogenic growth in a dose-dependent manner. Inhibition of the Raf-MEK-ERK pathway by CI-1040 significantly enhances apoptosis, blocks cell cycle progression at the S phase, inhibits expression of the cell cycle-related genes, and significantly inhibits phosphorylation and activation of the ERK1/2 protein. Furthermore, CI-1040 significantly inhibits tumor growth in different NB 3D spheroidal tumor models in a dose-dependent manner and by directly inhibiting spheroidal tumor cells. Overall, our findings highlight that direct inhibition of the Raf-MEK-ERK pathway is a novel therapeutic approach for NB, and further developing repurposing strategies using CI-1040 is a clinically tractable strategy for effectively treating NB.

Repurposing clofazimine for malignant pleural mesothelioma treatment - In-vitro assessment of efficacy and mechanism of action

AIMS

Malignant pleural mesothelioma (MPM) is a rare cancer of lungs' pleural cavity, with minimally effective therapies available. Thus, there exists a necessity for drug repurposing which is an attractive strategy for drug development in MPM. Repurposing of an old FDA-approved anti-leprotic drug, Clofazimine (CFZ), presents an outstanding opportunity to explore its efficacy in treating MPM.

MAIN METHODS

Cytotoxicity, scratch assay, and clonogenic assays were employed to determine CFZ's ability to inhibit cell viability, cell migration, and colony growth. 3D Spheroid cell culture studies were performed to identify tumor growth inhibition potential of CFZ in MSTO-211H cell line. Gene expression analysis was performed using RT-qPCR assays to determine the CFZ's effect of key genes. Western blot studies were performed to determine CFZ's ability to induce apoptosis its effect to induce autophagy marker.

KEY FINDINGS

CFZ showed significant cytotoxicity against both immortalized and primary patient-derived cell lines with IC₅₀ values ranging from 3.4 μM (MSTO-211H) to 7.1 μM (HAY). CFZ significantly impaired MPM cell cloning efficiency, migration, and tumor spheroid formation. 3D Spheroid model showed that CFZ resulted in reduction in spheroid volume. RT-qPCR data showed downregulation of genes β-catenin, BCL-9, and PRDX1; and upregulation of apoptosis markers such as PARP, Cleaved caspase 3, and AXIN2. Additionally, immunoblot analysis showed that CFZ down-regulates the expression of β-catenin (apoptosis induction) and up-regulates p62, LC3B protein II (autophagy inhibition).

SIGNIFICANCE

It can be concluded that CFZ could be a promising molecule to repurpose for MPM treatment which needs numerous efforts from further studies.

Abstract 2957: Inhibition of epigenetic regulator menin is a novel therapeutic approach for high-risk neuroblastoma

Controlling epigenetic factors such as histone methyltransferases and demethylases has recently emerged as an attractive therapeutic approach for different cancers. KMT2 family protein KMT2A or MLL1 is a H3K4 methyltransferase, which is known to play an essential role in cancer development. MLL1 forms a COMPASS complex to function as an epigenetic regulator and Menin is one of the specific and required binding partner for the activation and function of this epigenetic enzyme. Menin acts as a tumor suppressor protein, and inhibition of Menin-MLL1 interaction has been shown to destabilize the MLL1 epigenetic complex, inhibits H3K4 methyltransferase activity, and hinder the oncogenic potential of various cancers. High-risk neuroblastoma (NB) is the most common extracranial solid pediatric tumor and accounts for almost 15% of all pediatric cancer-related deaths. Recent reports indicate that aberrant activation of epigenetic regulators may drive NB progression and relapse. Therefore, in the present study, we used a specific small-molecule inhibitor, MI-503 to disrupt Menin-MLL1 interaction, and to further understand the role of Menin in pediatric NB. We used different NB cell lines including MYCN-non-amplified (SH-SY5Y, SK-N-AS, CHLA-255) and MYCN-amplified (NGP, LAN-5, IMR-32), and performed cytotoxicity and Colonogenic assays to determine the effect of Menin inhibition on NB proliferation. Results showed that MI-503 significantly inhibits NB proliferation and colony formation capacity in a dose-dependent manner in contrast to controls. Further, we performed apoptosis and cell cycle assays and observed that MI-503 significantly induces apoptosis as detected by the increase of Annexin-V positive early apoptotic cells, and blocks cell cycle progression at the S phase in all NB cell lines tested. Additionally, Western blot assays demonstrated an overall inhibition of H3K3me3 levels in NB cells in response to MI-503. To further determine the effects of Menin inhibition on NB tumor growth, we developed a NB 3D spheroid tumor model that recapitulate in vivo tumor growth for solid tumors. Treatment with MI-503 significantly inhibits spheroidal tumor growth by inducing tumor cell death in a dose-dependent manner. Overall, these data highlight the role of epigenetic regulation, MLL1 complex, and of Menin in NB growth and tumorigenicity. In our future efforts, we will further elucidate the effects of MI-503 and the role of Menin in NB by using in vivo tumor models. Epigenetic inhibitor such as MI-503 holds significant potential for further clinical development and as a novel therapeutic approach for NB.

Citation Format: Rameswari Chilamakuri, Saurabh Agarwal. Inhibition of epigenetic regulator menin is a novel therapeutic approach for high-risk neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2957.

Inhibition of Polo-like Kinase 1 by HMN-214 Blocks Cell Cycle Progression and Inhibits Neuroblastoma Growth

Polo-like kinase 1 (PLK1) is an essential cell cycle mitotic kinase component that plays an important role in cell cycle progression and has been reported to be involved in various cancers, including neuroblastoma (NB). PLK1 also regulates G2/M transition, chromosomal segregation, spindle assembly maturation, and mitotic exit. NB is an early embryonic-stage heterogeneous solid tumor and accounts for 15% of all pediatric cancer-related deaths. Therefore, we aimed to develop a targeting strategy for PLK1 by repurposing HMN-214 in NB. HMN-214 is a prodrug of HMN-176 and is known to selectively interfere with PLK1 function. In the present study, we performed the transcriptomic analysis of a large cohort of primary NB patient samples and revealed that PLK1 expression is inversely correlated with the overall survival of NB patients. Additionally, we found that PLK1 strongly correlates with NB disease and stage progression. HMN-214 significantly inhibited NB proliferation and colony formation in both MYCN-amplified and -nonamplified cell lines in a dose-dependent manner. Furthermore, HMN-214 induces apoptosis and significantly obstructs the cell cycle at the G2/M phase in NB cells by inhibiting multiple cell-cycle-related genes, such as PLK1, WEE1, CDK1, CDK2, Cyclin B1, CHK1, and CHK2. HMN-214 significantly inhibits cell cycle regulator CDK1 and the phosphorylation and activation of PLK1 in NB. In the NB 3D spheroid tumor model, HMN-214 significantly and in a dose-dependent manner inhibits spheroid tumor mass and growth. Overall, our study highlights that targeting PLK1 using HMN-214 is a novel therapeutic approach for NB.

Dual Targeting of PI3K and HDAC by CUDC-907 Inhibits Pediatric Neuroblastoma Growth

Simple Summary

High-risk neuroblastoma (NB) is an aggressive cancer of very young children and accounts for almost 15% of all pediatric cancer deaths. Current therapies include high-dose chemotherapy and radiation, which have long-term toxic side effects. Despite these intensive therapies, the overall 5-year survival rate of NB is less than 50%. Therefore, developing novel therapeutic approaches targeting the molecular mechanisms that drive NB progression is very important. In the present study, we repurpose CUDC-907, a dual inhibitor of PI3K and histone deacetylases. These regulators are known to regulate MYCN expression, a key prognostic marker of NB. CUDC-907 potently inhibits NB growth and 3D spheroid tumor growth by inhibiting PI3K, HDAC, and MYCN. Overall, our pre-clinical data demonstrate that repurposing CUDC-907 as a single drug is a novel and effective therapeutic approach for NB.

Abstract

The dysregulation of PI3K, HDACs, and MYCN are well known for promoting multiple cancer types, including neuroblastoma (NB). Targeting the upstream regulators of MYCN, including HDACs and PI3K, was shown to suppress cancer growth. In the present study, we analyze different NB patient datasets to reveal that high PI3K and HDAC expression is correlated with overall poor NB patient survival. High PI3K level is also found to be associated with high MYCN level and NB stage progression. We repurpose a dual inhibitor CUDC-907 as a single agent to directly target both PI3K and HDAC in NB. We use in vitro methodologies to determine the efficacy and selectivity of CUDC-907 using six NB and three control fibroblast cell lines. Our results show that CUDC-907 significantly inhibits NB proliferation and colony growth, induces apoptosis, blocks cell cycle progression, inhibits MYCN, and enhances H3K9Ac levels by inhibiting the PI3K/AKT signaling pathway and HDAC function. Furthermore, CUDC-907 significantly inhibits NB tumor growth in a 3D spheroid tumor model that recapitulates the in vivo tumor growth. Overall, our findings highlight that the dual inhibition of PI3K and HDAC by CUDC-907 is an effective therapeutic strategy for NB and other MYC-dependent cancers.

BX-795 inhibits neuroblastoma growth and enhances sensitivity towards chemotherapy

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AKT overexpression correlates with poor prognosis in neuroblastoma patients.

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BX-795 inhibits PDK1 and abrogates the AKT signaling pathway activation.

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BX-795 demonstrates strong efficacy in neuroblastoma spheroid tumor model.

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Combination with BX-795 synergistically enhances doxorubicin antitumor activity.

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BX-795 synergistically sensitized ALK mutated neuroblastoma cell lines to crizotinib.

High-risk neuroblastoma (NB) represents a major clinical challenge in pediatric oncology due to relapse of metastatic, drug-resistant disease, and treatment-related toxicities. An analysis of 1235 primary NB patient dataset revealed significant increase in AKT1 and AKT2 gene expression with cancer stage progression. Additionally, Both AKT1 and AKT2 expression inversely correlate with poor overall survival of NB patients. AKT1 and AKT2 genes code for AKT that drive a major oncogenic cell signaling pathway known in many cancers, including NB. To inhibit AKT pathway, we repurposed an antiviral inhibitor BX-795 that inhibits PDK1, an upstream activator of AKT. BX-795 potently inhibits NB cell proliferation and colony growth in a dose-dependent manner. BX-795 significantly enhances apoptosis and blocks cell cycle progression at mitosis phase in NB. Additionally, BX-795 potently inhibits tumor formation and growth in a NB spheroid tumor model. We further tested dual therapeutic approaches by combining BX-795 with either doxorubicin or crizotinib and found synergistic and significant inhibition of NB growth, in contrast to either drug alone. Overall, our data demonstrate that BX-795 inhibits AKT pathway to inhibit NB growth, and combining BX-795 with current therapies is an effective and clinically tractable therapeutic approach for NB.

Abstract 1346: Direct targeting of MAPK/ERK signaling pathway is a novel therapeutic approach for high-risk neuroblastoma

Neuroblastoma is a highly heterogenous pediatric tumor that develops during the early embryonic stages, and accounts for almost 15% of pediatric cancer related deaths. Despite advanced and intensive therapeutic approaches that combine surgery, radiation, and chemotherapy, high-risk neuroblastoma (NB) patients' long-term survival is still less than 50%. Tumor metastasis, relapse, drug-resistance, and treatment related toxicities mandate the development of novel therapeutic approaches to treat NB patients. MAPK/ERK pathway plays an important oncogenic role in different types of cancers, including NB. Activation of the MAPK/ERK pathway is known to induce cancer cell proliferation, progression, metabolism, and resistance to drug-induced apoptosis. In the present study, we investigated the effect of a small-molecule MEK inhibitor that targets MEK1 and MEK2 to block MAPK/ERK pathway in NB. Cytotoxicity assays using Cell-Titer One solution in different MYCN-amplified (NGP, LAN-5, CHLA-255-MYCN) and MYCN-non-amplified (SH-SY5Y, SK-N-AS, CHLA-255) NB cell lines show that MEK inhibitor significantly reduce the NB cell proliferation in a dose-dependent manner. We further performed clonogenic assays and 3D spheroidal assays to mimic the NB tumor growth, and our results show that MEK inhibitor significantly inhibit NB colony formation, inhibit 3D spheroidal tumor size by inducing cell death in 3D spheroidal tumors, in comparison to controls. Additionally, MEK inhibitor in a dose-dependent manner induces apoptosis and blocks cell cycle progression in NB cells in comparison to control, as determined by Annexin V apoptosis assays and Click-iT EdU cell proliferation assay respectively. Furthermore, gene expression analysis show that MEK inhibitor significantly reduce the mRNA expression of specific MAPK/ERK pathway targets such as MEK1, MEK2, and ERK2. Western blot assays further confirm the efficacy of MEK inhibitor in blocking MAPK/ERK pathway by significantly inhibiting the phosphorylation of key pathway proteins. Taken together, our results highlight that: a) MAPK/ERK pathway is implicated in NB growth, and b) direct targeting of MAPK/ERK signaling pathway by using a novel small molecule MEK inhibitor inhibit NB proliferation and 3D tumor growth. We will further combine this MEK inhibitor with current chemotherapy drugs to develop effective therapeutic approaches for NB patients.

Citation Format: Rameswari Chilamakuri, Bharti Sharma, Danielle C. Rouse, Saurabh Agarwal. Direct targeting of MAPK/ERK signaling pathway is a novel therapeutic approach for high-risk neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1346.

COVID-19: Characteristics and Therapeutics

Novel coronavirus (COVID-19 or 2019-nCoV or SARS-CoV-2), which suddenly emerged in December 2019 is still haunting the entire human race and has affected not only the healthcare system but also the global socioeconomic balances. COVID-19 was quickly designated as a global pandemic by the World Health Organization as there have been about 98.0 million confirmed cases and about 2.0 million confirmed deaths, as of January 2021. Although, our understanding of COVID-19 has significantly increased since its outbreak, and multiple treatment approaches and pharmacological interventions have been tested or are currently under development to mitigate its risk-factors. Recently, some vaccine candidates showed around 95% clinical efficacy, and now receiving emergency use approvals in different countries. US FDA recently approved BNT162 and mRNA-1273 vaccines developed by Pfizer/BioNTech and Moderna Inc. for emergency use and vaccination in the USA. In this review, we present a succinct overview of the SARS-CoV-2 virus structure, molecular mechanisms of infection, COVID-19 epidemiology, diagnosis, and clinical manifestations. We also systematize different treatment strategies and clinical trials initiated after the pandemic outbreak, based on viral infection and replication mechanisms. Additionally, we reviewed the novel pharmacological intervention approaches and vaccine development strategies against COVID-19. We speculate that the current pandemic emergency will trigger detailed studies of coronaviruses, their mechanism of infection, development of systematic drug repurposing approaches, and novel drug discoveries for current and future pandemic outbreaks.

Abstract 5010: Targeting of AKT pathway inhibit high-risk neuroblastoma growth

High-risk neuroblastoma (NB) represents a major clinical challenge in pediatric oncology. Despite intensive genotoxic therapies, long-term survival for NB patients remains poor (&lt;45%), and the disease accounts for almost 15% of all pediatric cancer deaths. Relapse of metastatic, drug-resistant disease, and treatment-related toxicities mandate the development of novel therapeutic strategies for NB patients. Oncogenic activation of AKT signaling pathway has been shown in different cancer types, including NB. Activation of AKT pathway induce cancer progression, proliferation, metabolism, angiogenesis, and resistance to drug-induced apoptosis. Activation of PI3K (phosphatidylinositol 3-kinase) and PDK1 (3-Phosphoinositide-dependent kinase 1) are the two major steps that mediate the AKT phosphorylation and activation. In the present study, we performed a custom low-density Human AKT pathway array and found that genes coding for PI3K, PIP3, PDK1, and AKT are overexpressed in NB cells in comparison to normal human fibroblast cells. Further, we analyzed a total of 1135 NB patient samples to determine the effect of PI3K and PDK1 overexpression on NB patient survival and correlation with disease stage. Kaplan-Meier analyses of patient datasets revealed that both PI3K and PDK1 high levels strongly correlate with poor overall and event-free survival of NB patients (p&lt;0.0001). In addition, higher stage, more aggressive tumors have significantly higher PI3K and PDK1 expression, suggesting that gain of PI3K or PDK1 function may lead to de-differentiated invasive malignancy. To further analyze the effect of PI3K and PDK1 on NB cell proliferation, we used specific small molecule inhibitors that target PI3K and PDK1, and performed cell proliferation assays in NB cell lines. Results show that inhibition of either PI3K or PDK1 significantly inhibit NB cell proliferation (p&lt;0.01) in a dose-dependent manner. Furthermore, both of the inhibitors induce apoptosis, block cell cycle progression, inhibit colony formation, and inhibit cell migration in NB cells, in comparison to control. Additionally, we performed in vitro 3D sphere formation assays that mimic in vivo tumor growth, and found that inhibition of AKT pathway by either inhibiting PI3K or PDK1 leads to significant reduction of sphere growth and size in contrast to control. Overall, these data highlight that: a) AKT signaling pathway is implicated in NB growth, b) PI3K and PDK1 upstream of the AKT are important regulators of NB proliferation, and c) direct targeting of these regulators is a novel therapeutic approach to high-risk NB. We will further explore these strategies and combine them with current therapies to develop effective therapeutic approaches for NB patients.

Citation Format: Rameswari Chilamakuri, Saurabh Agarwal. Targeting of AKT pathway inhibit high-risk neuroblastoma growth [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5010.