Monoamine oxidase A inhibitor-near-infrared dye conjugate reduces prostate tumor growth

Targeting monoamine oxidases in cancer: advances and opportunities

Monoamine oxidases (MAOs) are a crucial pair of isoenzymes responsible for degrading monoamine neurotransmitters and dietary amines. In addition to extensive studies of their roles in the context of brain functions and disorders over decades, emerging evidence indicates that MAOs are also often dysregulated and associated with clinical outcomes in diverse cancers, with the ability to differentially regulate cancer growth, invasion, metastasis, progression, and therapy response depending on the cancer type. In this review, we summarize recent advances in understanding the clinical relevance, functional importance, and mechanisms of MAOs in a broad range of cancers, and discuss the application and therapeutic benefit of MAO inhibitors (MAOIs) for cancer treatment, highlighting the roles of MAOs as novel regulators, prognostic biomarkers, and therapeutic targets in cancer.

Divergent Syntheses of Near-Infrared Light-Activated Molecular Jackhammers for Cancer Cell Eradication

Aminocyanines incorporating Cy7 and Cy7.5 moieties function as molecular jackhammers (MJH) through vibronic-driven action (VDA). This mechanism, which couples molecular vibrational and electronic modes, results in picosecond-scale concerted stretching of the entire molecule. When cell-associated and activated by near-infrared light, MJH mechanically disrupts cell membranes, causing rapid necrotic cell death. Unlike photodynamic and photothermal therapies, the ultrafast vibrational action of MJH is unhindered by high concentrations of reactive oxygen species scavengers and induces only a minimal temperature increase. Here, the efficient synthesis of a library of MJH is described using a practical approach to access a key intermediate and facilitating the preparation of various Cy7 and Cy7.5 MJH with diverse side chains in moderate to high yields. Photophysical characterization reveals that structural modifications significantly affect molar extinction coefficients and quantum yields while maintaining desirable absorption and emission wavelengths. The most promising compounds, featuring dimethylaminoethyl and dimethylcarbamoyl substitutions, demonstrate up to sevenfold improvement in phototherapeutic index compared to Cy7.5 amine across multiple cancer cell lines. This synthetic strategy provides a valuable platform for developing potent, light-activated therapeutic agents for cancer treatment, with potentially broad applicability across various cancer types.

Heat shock proteins as hallmarks of cancer: insights from molecular mechanisms to therapeutic strategies

Heat shock proteins are essential molecular chaperones that play crucial roles in stabilizing protein structures, facilitating the repair or degradation of damaged proteins, and maintaining proteostasis and cellular functions. Extensive research has demonstrated that heat shock proteins are highly expressed in cancers and closely associated with tumorigenesis and progression. The "Hallmarks of Cancer" are the core features of cancer biology that collectively define a series of functional characteristics acquired by cells as they transition from a normal state to a state of tumor growth, including sustained proliferative signaling, evasion of growth suppressors, resistance to cell death, enabled replicative immortality, the induction of angiogenesis, and the activation of invasion and metastasis. The pivotal roles of heat shock proteins in modulating the hallmarks of cancer through the activation or inhibition of various signaling pathways has been well documented. Therefore, this review provides an overview of the roles of heat shock proteins in vital biological processes from the perspective of the hallmarks of cancer and summarizes the small-molecule inhibitors that target heat shock proteins to regulate various cancer hallmarks. Moreover, we further discuss combination therapy strategies involving heat shock proteins and promising dual-target inhibitors to highlight the potential of targeting heat shock proteins for cancer treatment. In summary, this review highlights how targeting heat shock proteins could regulate the hallmarks of cancer, which will provide valuable information to better elucidate and understand the roles of heat shock proteins in oncology and the mechanisms of cancer occurrence and development and aid in the development of more efficacious and less toxic novel anticancer agents.

A Mitochondria-Targeted Heptamethine Indocyanine Small Molecular Chelator for Attenuating Uranium Nephrotoxicity

Radionuclide uranium has both a chemical and radioactive toxicity, leading to severe nephrotoxicity as it predominantly deposits itself in the kidneys after entering into human bodies. It crosses renal cell membranes, accumulates in mitochondria and causes mitochondrial oxidative damage and dysfunction. In this study, a mitochondria-targeted heptamethine indocyanine small molecule chelator modified with gallic acid (IR-82) is synthesized for uranium detoxication. Both gallic acid and sulfonic acid, as two hydrophilic endings, make IR-82, being excreted feasibly through kidneys. Gallic acid with polyphenol groups has a steady metal chelation effect and potent antioxidant ability, which may facilitate IR-82-alleviated uranium nephrotoxicity simultaneously by enhancing uranium decorporation from the kidneys and reducing mitochondrial oxidative damage. Cell viability assays demonstrate that IR-82 can significantly improve the cell viability of uranium-exposed human renal (HK-2) cells. It is also demonstrated to accumulate in mitochondria and reduce mitochondrial ROS and total intracellular ROS, as well as intracellular uranium content. In vivo imaging experiments in mice show that IR-82 could be excreted out through kidneys. ICP-MS tests further reveal that IR-82 can efficiently decrease the uranium deposition in mouse kidneys. IR-82 treatment improves the animal survival rate and renal function of experimental mice after high-dose uranium exposure. Collectively, our study may evidence that the development of uranium decorporation agents with kidney-mitochondrion dual targeting abilities is a promising strategy for attenuating uranium-induced nephrotoxicity.

Conditional PROTAC: Recent Strategies for Modulating Targeted Protein Degradation

Proteolysis-targeting chimeras (PROTACs) have emerged as a promising technology for inducing targeted protein degradation by leveraging the intrinsic ubiquitin-proteasome system (UPS). While the potential druggability of PROTACs toward undruggable proteins has accelerated their rapid development and the wide-range of applications across diverse disease contexts, off-tissue effects and side-effects of PROTACs have recently received attentions to improve their efficacy. To address these issues, spatial or temporal target protein degradation by PROTACs has been spotlighted. In this review, we explore chemical strategies for modulating protein degradation in a cell type-specific (spatio-) and time-specific (temporal-) manner, thereby offering insights for expanding PROTAC applications to overcome the current limitations of target protein degradation strategy.

Fluorescent Probes for Disease Diagnosis

The identification and detection of disease-related biomarkers is essential for early clinical diagnosis, evaluating disease progression, and for the development of therapeutics. Possessing the advantages of high sensitivity and selectivity, fluorescent probes have become effective tools for monitoring disease-related active molecules at the cellular level and in vivo. In this review, we describe current fluorescent probes designed for the detection and quantification of key bioactive molecules associated with common diseases, such as organ damage, inflammation, cancers, cardiovascular diseases, and brain disorders. We emphasize the strategies behind the design of fluorescent probes capable of disease biomarker detection and diagnosis and cover some aspects of combined diagnostic/therapeutic strategies based on regulating disease-related molecules. This review concludes with a discussion of the challenges and outlook for fluorescent probes, highlighting future avenues of research that should enable these probes to achieve accurate detection and identification of disease-related biomarkers for biomedical research and clinical applications.

A second life for MAO inhibitors? From CNS diseases to anticancer therapy

Monoamine oxidases A and B (MAO A, B) are ubiquitous enzymes responsible for oxidative deamination of amine neurotransmitters and xenobiotics. Despite decades of studies, MAO inhibitors (MAOIs) find today limited therapeutic space as second-line drugs for the treatment of depression and Parkinson's disease. In recent years, a renewed interest in MAOIs has been raised up by several studies investigating the role of MAOs, particularly MAO A, in tumor insurgence and progression, and the efficacy of MAOIs as coadjutants in the therapy of chemoresistant tumors. In this survey, we highlight the implication of MAOs in the biochemical pathways of tumorigenesis and review the state-of-the-art of preclinical and clinical studies of MAOIs as anticancer agents used in monotherapy or in combination with antitumor chemotherapeutics.

Rational Design of Bioorthogonally Activatable PROTAC for Tumor-Targeted Protein Degradation

Protein degradation mediated by the proteolysis-targeting chimera (PROTAC) has emerged as an efficient strategy to accurately control intracellular protein levels. However, the development of PROTACs is limited by their systemic toxicity. Herein, we report a bioorthogonally activatable prodrug (BT-PROTAC) strategy to accurately control the activity of PROTACs. As a proof of concept, we introduced the highly reactive trans-cyclooctene into PROTAC molecule MZ1, the structure-acitivity relationships of which were well characterized previously, to construct the bioorthogonally activatable prodrug BT-PROTAC. Compared with MZ1, BT-PROTAC is incapable of degradation of BRD4 protein. However, BT-PROTAC can be activated by highly active tetrazine compound BODIPY-TZ in vitro. Furthermore, we could selectively degrade BRD4 protein in tumor tissue enabled by tumor-targeted tetrazine compound IR808-TZ. This strategy may represent an alternative to existing strategies and may be widely applied in the design of BT-PROTAC targeting other proteins.

A Mitochondria-Targeted Ferroptosis Inducer Activated by Glutathione-Responsive Imaging and Depletion for Triple Negative Breast Cancer Theranostics

Ferroptosis is a new type of iron-dependent programmed cell death characterized by glutathione (GSH) depletion, selenoprotein glutathione peroxidase 4 (GPX4) inactivation, and lipid peroxides accumulation. Mitochondria, as the main source of intracellular energy supply and reactive oxygen species (ROS) generation, play a central role in oxidative phosphorylation and redox homeostasis. Therefore, targeting cancer-cell mitochondria and attacking redox homeostasis is expected to induce robust ferroptosis-mediated anticancer effects. In this work, a theranostic ferroptosis inducer (IR780-SPhF), which can simultaneously achieve the imaging and therapy of triple-negative breast cancer (TNBC) by targeting mitochondria is presented. It is developed from a mitochondria-targeting small molecule (IR780) with cancer-preferential accumulation, enabling it to react with GSH by nucleophilic substitution, resulting in mitochondrial GSH depletion and redox imbalance. More interestingly, IR780-SPhF exhibits GSH-responsive near-infrared fluorescence emission and photoacoustic imaging characteristics, further facilitating diagnosis and treatment with real-time monitoring of TNBC with a highly elevated GSH level. Both in vitro and in vivo results demonstrate that IR780-SPhF exhibits potent anticancer effect, which is significantly stronger than cyclophosphamide, a classic drug commonly recommended for TNBC patients in clinic. Hence, the reported mitochondria-targeted ferroptosis inducer may represent a promising candidate and a prospective strategy for efficient cancer treatment.

GSH-Responsive Prodrug Nanoassembly as a Carrier-Free Nanoplatform for Tumor-Targeting Delivery and Chemo-Photothermal Therapy

Photothermal therapy, combined with chemotherapy, holds promising prospects for the therapeutic outcome of malignant tumors. However, the synergistic therapeutic effect suffers from low coloading capacity and inefficient synchronous tumor-targeting delivery of chemodrug and photothermal photosensitizers. Herein, we designed a versatile carrier-free nanoplatform to seek improvement for chemo-photothermal therapy. An NIR photosensitizer IR-808 was used for noninvasive cancer imaging, diagnosis, and imaging-guided photothermal therapy. A reduction-sensitive paclitaxel prodrug (PTX-SS-PEG2k) was rationally synthesized by covalently linking paclitaxel with polyethylene glycol 2000 via a disulfide bond. Then, the carrier-free nanoassemblies were constructed with an inner core of IR-808 and an amphiphilic paclitaxel prodrug shell. PTX-SS-PEG2k served as a stabilizer and chemodrug and could facilitate the self-assembly of IR-808 nanoparticles with high coloading efficiency and reduction-sensitive drug release. The versatile nanoplatform exhibited multiple advantages, including high drug payload, reduction-sensitive drug release, tumor-targeting drug delivery, and potent synergistic antitumor effect. We provide a versatile theranostic nanoplatform, which improves the effectiveness of synergetic chemo-photothermal therapy and reduces the off-target toxicity.

Design, synthesis, and biological activity of dual monoamine oxidase A and heat shock protein 90 inhibitors, N-Methylpropargylamine-conjugated 4-isopropylresorcinol for glioblastoma

Monoamine oxidase A (MAO A) and heat shock protein 90 (HSP90) inhibitors have been shown to decrease the progression of glioblastoma (GBM) and other cancers. In this study, a series of MAO A/HSP90 dual inhibitors were designed and synthesized in the hope to develop more effective treatment of GBM. Compounds 4-b and 4-c are conjugates of isopropylresorcinol (pharmacophore of HSP90 inhibitor) with the phenyl group of clorgyline (MAO A inhibitor) by a tertiary amide bond substituted with methyl (4-b) or ethyl (4-c) group, respectively. They inhibited MAO A activity, HSP90 binding, and the growth of both TMZ-sensitive and -resistant GBM cells. Western blots showed that they increased HSP70 expression indicating reduced function of HSP90, reduced HER2 and phospho-Akt expression similar to MAO A or HSP90 inhibitor itself. Both compounds decreased IFN-γ induced PD-L1 expression in GL26 cells, suggesting they can act as immune checkpoint inhibitor. Further, they reduced tumor growth in GL26 mouse model. NCI-60 analysis showed they also inhibited the growth of colon cancer, leukemia, non-small cell lung and other cancers. Taken together, this study demonstrates MAO A/HSP90 dual inhibitors 4-b and 4-c reduced the growth of GBM and other cancers, and they have potential to inhibit tumor immune escape.

High monoamine oxidase a expression predicts poor prognosis for prostate cancer patients

BACKGROUND

Monoamine oxidase A (MAOA) is a mitochondrial enzyme that is involved in prostate tumorigenesis and cancer metastasis. The predictive power of the preoperative clinical and pathological indicators for prostate cancer(PC) remains to be improved. To enrich evidence regarding the value of MAOA as a prognostic biomarker in clinical practice, this study explored the significance of MAOA expression as a prognostic marker for patients with PC after radical prostatectomy-pelvic lymph node dissection (RP-PLND).

METHODS

MAOA expression was analyzed in 50 benign prostate tissues and 115 low-intermediate risk and 163 high-risk PC tissues using tissue immunohistochemistry (IHC). Propensity score matching, survival analysis and COX regression analysis were conducted to investigate the correlation between high MAOA expression and progression free survival (PFS) in PC patients.

RESULTS

MAOA expression was increased in PC patients, especially in those with high risk PC and pathological lymph node (pLN) metastasis. High MAOA expression was significantly associated with PSA recurrence for both low-intermediate risk PC patients (log-rank test: P = 0.02) and high risk PC patients (log-rank test: P = 0.03). Cox regression analysis revealed that high MAOA expression was an adverse prognostic factor for both low-intermediate risk PC patients (hazard ratio [HR] 2.74, 95% confidence interval [CI] 1.26-5.92; P = 0.011) and high risk PC patients (HR 1.73, 95% CI 1.11-2.71; P = 0.016). High MAOA expression was also significantly associated with PSA recurrence in high risk PC patients developed into castration-resistant prostate cancer (CRPC) and were receiving abiraterone therapy (log-rank: P = 0.01).

CONCLUSIONS

MAOA expression correlates with the malignant progression of PC. High MAOA expression may be a poor prognostic marker for patients with PC after RP-PLND. More careful follow up or potential of adjuvant hormonal therapy may be addressed for patients with high MAOA expression.

Multifunctional small-molecule theranostic agents for tumor-specific imaging and targeted chemotherapy

Cancer is one of the leading causes of death worldwide. Although great progress has been achieved in cancer diagnosis and treatment, novel therapies are still urgently needed to increase the efficacy and reduce the side effects of conventional therapies. Personalized medicine involves administering patients drugs that are specific to the characteristics of their tumors, and has significantly reduced side effects and increased overall survival rates. Multifunctional theranostic drugs are designed to combine diagnostic and therapeutic functions into a single molecule, which reduces the number of drugs administered to patients and increases patient compliance, and have shown great potential in propelling personalized medicine. This review focuses on multifunctional small-molecule theranostic agents for tumor-specific imaging and targeted chemotherapy, with a particular emphasis placed on highlighting design strategies and application in vitro or in vivo. The challenges and future perspectives of multifunctional small molecules are also discussed.

Monoamine oxidase A (MAOA): A promising target for prostate cancer therapy

Monoamine oxidase A (MAOA) is a mitochondrial enzyme that catalyzes the oxidative deamination of monoamine neurotransmitters and dietary amines. Previous studies have shown that MAOA is clinically associated with prostate cancer (PCa) progression and plays a key role in almost each stage of PCa, including castrate-resistant prostate cancer, neuroendocrine prostate cancer, metastasis, drug resistance, stemness, and perineural invasion. Moreover, MAOA expression is upregulated not only in cancer cells but also in stromal cells, intratumoral T cells, and tumor-associated macrophages; thus, targeting MAOA can be a multi-pronged approach to disrupt tumor promoting interactions between PCa cells and tumor microenvironment. Furthermore, targeting MAOA can disrupt the crosstalk between MAOA and the androgen receptor (AR) to restore enzalutamide sensitivity, blocks glucocorticoid receptor (GR)- and AR-dependent PCa cell growth, and is a potential strategy for immune checkpoint inhibition, thereby alleviating immune suppression and enhancing T cell immunity-based cancer immunotherapy. MAOA is a promising target for PCa therapy, which deserves further exploration in preclinical and clinical settings.

Doxorubicin-isoniazid conjugate regulates immune response and tumor microenvironment to enhance cancer therapy

Immune checkpoint inhibitors (ICIs) represent a new class of immunotherapy drugs, and are used to relieve immune suppression or enhance the immune response through the blockade of checkpoint ligands or receptors. ICIs have achieved great success in clinical cancer treatment. Monoamine oxidase A (MAOA) is a potent immune checkpoint of immunotherapy. Recently, it has been reported that MAOA inhibitors could enhance CD8⁺ T cell activity by upregulating 5-HT autocrine pathway in T cells. In this study, we synthesized doxorubicin (DOX) and isoniazid (INH, a MAOA inhibitor) conjugates through a pH sensitive hydrazone bond. Results of the in vivo studies showed that DOX-INH could effectively enhance the activity of CD8⁺ T cells and perform a synergistic anti-tumor effect with PD-L1 small molecular inhibitor (BMS202). In addition, in an orthotopic 4T1 breast cancer model, it was demonstrated that DOX-INH could inhibit the epithelial-mesenchymal transition process by blocking Shh, IL-6, and TGF-β signaling pathways, thereby inhibiting the growth and metastasis of breast cancer. Thus, a simple and effective small molecule conjugate produced by the combination of a chemotherapy drug and a MAOA inhibitor shows broad prospect in cancer therapy.

In Vitro and In Vivo Assays Characterizing MAO A Function in Cancers

Emerging studies, including ours, have revealed the novel essential roles of monoamine oxidase A (MAO A) in mediating the growth and progression of several types of cancers. Recently, we presented the first evidence of MAO A's ability to promote cancer cell perineural invasion, the neoplastic invasion of nerves widely recognized as a significant route for cancer metastasis. Here, we describe a perineural invasion in vitro assay using a 3D coculture with a cancer cell line and an immortalized dorsal root ganglion neuronal cell line for rapid examination of MAO A's roles in cancer-nerve cell crosstalk and evaluating the efficacy of MAO A inhibitors for disrupting perineural invasion. We also summarized the fundamental methods for determining MAO A's effects on cancer cell proliferation in vitro and tumorigenesis in vivo.

Monoamine oxidase A: An emerging therapeutic target in prostate cancer

Monoamine oxidase A (MAOA), a mitochondrial enzyme degrading biogenic and dietary amines, has been studied in the contexts of neuropsychiatry and neurological disorders for decades, but its importance in oncology, as best exemplified in prostate cancer (PC) to date, was only realized recently. PC is the most commonly diagnosed non-skin cancer and the second deadliest malignancy for men in the United States. In PC, the increased expression level of MAOA is correlated with dedifferentiated tissue microarchitecture and a worse prognosis. A wealth of literature has demonstrated that MAOA promotes growth, metastasis, stemness and therapy resistance in PC, mainly by increasing oxidative stress, augmenting hypoxia, inducing epithelial-to-mesenchymal transition, and activating the downstream principal transcription factor Twist1-dictated multiple context-dependent signaling cascades. Cancer-cell-derived MAOA also enables cancer-stromal cell interaction involving bone stromal cells and nerve cells by secretion of Hedgehog and class 3 semaphorin molecules respectively to modulate the tumor microenvironment in favor of invasion and metastasis. Further, MAOA in prostate stromal cells promotes PC tumorigenesis and stemness. Current studies suggest that MAOA functions in PC in both cell autonomous and non-autonomous manners. Importantly, clinically available monoamine oxidase inhibitors have shown promising results against PC in preclinical models and clinical trials, providing a great opportunity to repurpose them as a PC therapy. Here, we summarize recent advances in our understanding of MAOA roles and mechanisms in PC, present several MAOA-targeted strategies that have been nominated for treating PC, and discuss the unknowns of MAOA function and targeting in PC for future exploration.

Affinity probes based on small-molecule inhibitors for tumor imaging

Methods for molecular imaging of target areas, including optical imaging, radionuclide imaging, magnetic resonance imaging and other imaging technologies, are helpful for the early diagnosis and precise treatment of cancers. In addition to cancer management, small-molecule inhibitors are also used for developing cancer target probes since they act as the tight-binding ligands of overexpressed proteins in cancer cells. This review aims to summarize the structural designs of affinity probes based on small-molecule inhibitors from the aspects of the inhibitor, linker, dye and radionuclide, and discusses the influence of the modification of these structures on affinity and pharmacokinetics. We also present examples of inhibitor affinity probes in clinical applications, and these summaries will provide insights for future research and clinical translations.

Rationally Designed Heptamethine Cyanine Photosensitizers that Amplify Tumor-Specific Endoplasmic Reticulum Stress and Boost Antitumor Immunity

Cancer phototherapy activates immunogenic cell death (ICD) and elicits a systemic antitumor immune response, which is an emerging approach for tumor treatment. Most available photosensitizers require a combination of immune adjuvants or checkpoint inhibitors to trigger antitumor immunity because of the immunosuppressive tumor microenvironment and the limited phototherapeutic effect. A class of tumor-targeting heptamethine cyanine photosensitizers modified with an endoplasmic reticulum (ER)-targeting group (benzenesulfonamide) are synthesized. Phototherapy of tumor cells markedly amplifies ER stress and promotes tumor antigen release, as the ER is required for protein synthesis, secretion, and transport. More importantly, different electron-donating or -withdrawing substitutions are introduced into benzenesulfonamide to modulate the nonradiative decay pathways through intramolecular charge transfer, including singlet-triplet intersystem crossing (photodynamic effect) and internal thermal conversion (photothermal effect). Thus, a heptamethine cyanine photosensitizer containing a binitro-substituted benzenesulfonamide (ER-Cy-poNO₂ ) is identified that preferentially accumulates in the ER of tumor cells. It significantly enhances the phototherapeutic effect by inducing excessive ER stress and robust ICD. Consequently, this small molecular photosensitizer triggers a sufficient antitumor immune response and effectively suppresses the growth of both primary and distant metastatic tumors, whereas no apparent toxicity is observed. This heptamethine cyanine photosensitizer has the potential to enhance cancer-targeted immunotherapy.

Two-photon fluorescence imaging and ratiometric quantification of mitochondrial monoamine oxidase-A in neurons

Herein, we designed and developed a single two-photon ratiometric fluorescence probe (TMF2P) for selective and accurate determination of mitochondrial MAO-A in live neurons. It was discovered that the increases in MAO-A levels under oxidative stress resulted in an elevated influx of Ca²⁺ flow into mitochondria through the transient receptor potential melastatin 2 (TRPM2) channels.

Heterocycle-containing tranylcypromine derivatives endowed with high anti-LSD1 activity

As regioisomers/bioisosteres of 1a, a 4-phenylbenzamide tranylcypromine (TCP) derivative previously disclosed by us, we report here the synthesis and biological evaluation of some (hetero)arylbenzoylamino TCP derivatives 1b-6, in which the 4-phenyl moiety of 1a was shifted at the benzamide C3 position or replaced by 2- or 3-furyl, 2- or 3-thienyl, or 4-pyridyl group, all at the benzamide C4 or C3 position. In anti-LSD1-CoREST assay, all the meta derivatives were more effective than the para analogues, with the meta thienyl analogs 4b and 5b being the most potent (IC₅₀ values = 0.015 and 0.005 μM) and the most selective over MAO-B (selectivity indexes: 24.4 and 164). When tested in U937 AML and prostate cancer LNCaP cells, selected compounds 1a,b, 2b, 3b, 4b, and 5a,b displayed cell growth arrest mainly in LNCaP cells. Western blot analyses showed increased levels of H3K4me2 and/or H3K9me2 confirming the involvement of LSD1 inhibition in these assays.

Near-Infrared MAO A Inhibitor (NMI) Outperformed FDA-Approved Chemotherapeutic Agents in Brain and Other Cancers: A Bioinformatic Analysis of NCI60 Screening Data

Our previous work has shown that monoamine oxidase A (MAO A) is overexpressed in glioma and prostate cancer. Near-infrared dye conjugate MAO A Inhibitor (NMI) inhibited the growth of these cancers. This study investigated the effects of NMI on other cancers by NCI60 screening. Our results showed that 48 out of 59 screened cell lines from nine types of cancer had 100% growth inhibition at 10 μM NMI treatment. The in vitro efficacy of NMI determined by growth inhibition (GI₅₀ and TGI) and lethal doses (LC₅₀) has been further studied in various cell lines of CNS cancer, prostate cancer, and non-small cell lung cancer (NSCLC), these three cancers showed increased MAO A expression in tumors compared to normal tissues. Based on the waterfall plots and the 3D scatter plot of GI₅₀, TGI, and LC₅₀ data, NMI showed higher potency to several CNS cancer and NSCLC cell lines than prostate cancer cell lines. In vitro efficacy of NMI outperformed FDA-approved drugs for CNS cancer, prostate cancer, and NSCLC, respectively. The Pairwise Pearson Correlation Coefficient (PCC) showed that NMI has a unique mechanism compared to the existing anticancer drugs. This study shows that NMI is a novel theragnostic drug with high potency and unique mechanisms for brain, prostate, NSCLC, and other cancers.

The role of 5-HT metabolism in cancer

Serotonin (5-hydroxytryptamine, 5-HT) metabolism has long been linked to tumorigenesis and tumor progression. Numerous studies have shown the functions of 5-HT and its metabolites in the regulation of tumor biological processes like cell proliferation, invasion, metastasis, tumor angiogenesis and immunomodulatory through multi-step complex mechanisms. Reprogramming of 5-HT metabolism has been revealed in various tumors paving way for development of drugs that target enzymes, metabolites or receptors involved in 5-HT metabolic pathway. However, information on the role of 5-HT metabolism in cancer is scanty. This review briefly describes the main metabolic routes of 5-HT, the role of 5-HT metabolism in cancer and systematically summarizes the most recent advances in 5-HT metabolism-targeted cancer therapy.

The Use of Heptamethine Cyanine Dyes as Drug-Conjugate Systems in the Treatment of Primary and Metastatic Brain Tumors

Effective cancer therapeutics for brain tumors must be able to cross the blood-brain barrier (BBB) to reach the tumor in adequate quantities and overcome the resistance conferred by the local tumor microenvironment. Clinically approved chemotherapeutic agents have been investigated for brain neoplasms, but despite their effectiveness in peripheral cancers, failed to show therapeutic success in brain tumors. This is largely due to their poor bioavailability and specificity towards brain tumors. A targeted delivery system might improve the efficacy of the candidate compounds by increasing the retention time in the tumor tissue, and minimizing the numerous side effects associated with the non-specific distribution of the chemotherapy agent. Heptamethine cyanine dyes (HMCDs) are a class of near-infrared fluorescence (NIRF) compounds that have recently emerged as promising agents for drug delivery. Initially explored for their use in imaging and monitoring neoplasms, their tumor-targeting properties have recently been investigated for their use as drug carrier systems. This review will explore the recent developments in the tumour-targeting properties of a specific group of NIRF cyanine dyes and the preclinical evidence for their potential as drug-delivery systems in the treatment of primary and metastatic brain tumors.

Synthesis of Mitochondria-Anchored Nitroimidazoles with a Versatile NIR Fluorophore for Hypoxic Tumor-Targeting Imaging and Chemoradiotherapy

Nitroimidazoles are one of the most common radiosensitizers investigated to combat hypoxia-induced resistance to cancer radiotherapy. However, due to poor selectivity distinguishing cancer cells from normal cells, effective doses of radiosensitization are much closer to the doses of toxicity induced by nitroimidazoles, limiting their clinical application. In this work, a tumor-targeting near-infrared (NIR) cyanine dye (IR-808) was utilized as a targeting ligand and an NIR fluorophore tracer to chemically conjugate with different structures of hypoxia-affinic nitroimidazoles. One of the NIR fluorophore-conjugated nitroimidazoles (808-NM2) was identified to preferentially accumulate in hypoxic tumor cells, sensitively outline the tumor contour, and effectively inhibit tumor growth synergistically by chemotherapy and radiotherapy. More importantly, nitroimidazoles were successfully taken into cancer cell mitochondria via 808-NM2 conjugate to exert the synergistic effect of chemoradiotherapy. Regarding the important roles of mitochondria on cancer cell survival and metastasis under hypoxia, 808-NM2 may be hopeful to fight against hypoxic tumors.

Near-Infrared Monoamine Oxidase Inhibitor Biodistribution in a Glioma Mouse Model

PURPOSE

The biodistribution imaging kinetics of near-infrared monoamine oxidase inhibitor (NMI) are reported here.

METHODS

NMI was administered intravenously or orally to mice and detected by NIR fluorescence optical imaging within minutes and the longitudinal signal distribution was measured for up to 1 week after a single dose.

RESULTS

NMI rapidly reached 3.7-fold higher ventral and 3.2-fold higher brain region fluorescent signal intensity compared to oral route at 24 h. Similar patterns of NMI biodistribution were found in mice with or without intracranial implanted GL26 brain tumors. NMI was highly associated with tumors in contrast to adjacent non-tumor brain, confirming diagnostic utility. NMI 5 mg/kg imaging signal in brain at 48 h was optimal (tumor/non-tumor ratio > 3.5) with minimum off-target distribution. Intravenous NMI imaging signal peaked between 24 h and 48 h for lung, liver, kidney, blood, brain, and most other tissues. Clearance (signal weaker, but still present) from most tissues occurred by day 7. Intravenous low dose (0.5 mg/kg) minimally labeled tumor and other tissues, 5 mg/kg showed optimal imaging signal in glioma at a dose we previously reported as efficacious, and 50 mg/kg was tolerable but saturated the tissue signals beyond tumor specificity. Gel electrophoresis showed two major bands present in brain tumor and tissue protein lysates.

CONCLUSIONS

Intravenous 5 mg/kg was optimal dose to target brain tumor and identified off-target organs of concern: lungs, liver, and kidneys. These results demonstrate the biodistribution and optimal dose range of NMI for treatment and diagnostic monitoring of glioma.

Cyanine conjugates in cancer theranostics

Cyanine is a meritorious fluorogenic core for the construction of fluorescent probes and its phototherapeutic potential has been enthusiastically explored as well. Alternatively, the covalent conjugation of cyanine with other potent therapeutic agents not only boosts its therapeutic efficacy but also broadens its therapeutic modality. Herein, we summarize miscellaneous cyanine-therapeutic agent conjugates in cancer theranostics from literature published between 2014 and 2020. The application scenarios of such theranostic cyanine conjugates covered common cancer therapeutic modalities, including chemotherapy, phototherapy and targeted therapy. Besides, cyanine conjugates that serve as nanocarriers for drug delivery are introduced as well. In an additional section, we analyze the potential of these conjugates for clinical translation. Overall, this review is aimed to stimulate research interest in exploring unattempted therapeutic agents and novel conjugation strategies and hopefully, accelerate clinical translation in this field.

Monoamine oxidases in age-associated diseases: New perspectives for old enzymes

Population aging is one of the most significant social changes of the twenty-first century. This increase in longevity is associated with a higher prevalence of chronic diseases, further rising healthcare costs. At the molecular level, cellular senescence has been identified as a major process in age-associated diseases, as accumulation of senescent cells with aging leads to progressive organ dysfunction. Of particular importance, mitochondrial oxidative stress and consequent organelle alterations have been pointed out as key players in the aging process, by both inducing and maintaining cellular senescence. Monoamine oxidases (MAOs), a class of enzymes that catalyze the degradation of catecholamines and biogenic amines, have been increasingly recognized as major producers of mitochondrial ROS. Although well-known in the brain, evidence showing that MAOs are also expressed in a variety of peripheral organs stimulated a growing interest in the extra-cerebral roles of these enzymes. Besides, the fact that MAO-A and/or MAO-B are frequently upregulated in aged or dysfunctional organs has uncovered new perspectives on their roles in pathological aging. In this review, we will give an overview of the major results on the regulation and function of MAOs in aging and age-related diseases, paying a special attention to the mechanisms linked to the increased degradation of MAO substrates or related to MAO-dependent ROS formation.

Cyanine Nanocages Activated by Near-Infrared Light for the Targeted Treatment of Traumatic Brain Injury

Traumatic brain injury (TBI) is a common and prevalent condition that affects large numbers of people across a range of ages. Individuals engaging in physical activities and victims of accidents are at a higher risk for TBI. There is a lack of available treatment specifically for TBI. Given the difficulty to determine its precise location in the brain, TBI remains difficult to fully diagnose or treat. Herein, we disclose a novel strategy for directing therapeutic agents to TBI sites, without the need to determine the precise location of the TBI activity in the brain. This novel approach is based on the use of a cyanine dye nanocage carrying Gabapentin, a known TBI therapeutic agent. Upon exposure of the cyanine nanocage to near-infrared light, the local release of Gabapentin is triggered, selectively at the TBI-affected site.

Monoamine Oxidase A is a Major Mediator of Mitochondrial Homeostasis and Glycolysis in Gastric Cancer Progression

Objective

Monoamine oxidase A (MAO-A) is a mitochondrial protein involved in tumourigenesis in different types of cancer. However, the biological function of MAO-A in gastric cancer development remains unknown.

Methods

We examined MAO-A expression in gastric cancer tissues and in gastric cancer cell lines by immunohistochemistry and Western blot analyses. CCK8, FACS and bromodeoxyuridine incorporation assays were performed to assess the effects of MAO-A on gastric cancer cell proliferation. The role of MAO-A in mitochondrial function was determined through MitoSOX Red staining, ATP generation and glycolysis assays.

Results

In the present study, we observed that MAO-A was significantly upregulated in gastric cancer tissues and in AGS and MGC803 cells. The observed MAO-A inhibition indicated decreased cell cycle progression and proliferation. Silencing MAO-A expression was associated with suppressed migration and invasion of gastric cancer cells in vitro. Moreover, alleviated mitochondrial damage in these cells was demonstrated by decreased levels of mitochondrial reactive oxygen species and increased ATP generation. MAO-A knockdown also regulated the expression of the glycolysis rate-limiting enzymes hexokinase 2 and pyruvate dehydrogenase. Finally, we observed that the glycolysis-mediated effect was weakened in AGS and MGC803 cells when MAO-A was blocked.

Conclusion

The findings of the present study indicate that MAO-A is responsible for mitochondrial dysfunction and aerobic glycolysis, which in turn leads to the proliferation and metastasis of human gastric tumour cells.

PAMs inhibits monoamine oxidase a activity and reduces glioma tumor growth, a potential adjuvant treatment for glioma

BACKGROUND

Monoamine oxidase (MAO) A catalyzes oxidative deamination of monoamine neurotransmitters and dietary amines and regulates brain development and functions. Recently, we showed that MAO A mediates the progression and migration of glioma and MAO A inhibitors reduce glioma cell growth. Glioblastoma (GBM) is a common and most malignant brain tumor which is difficult to treat. Temozolomide (TMZ) is the current standard chemotherapy for glioma, but tumors usually become resistant and recur. So far, no effective therapy for TMZ-resistant glioma is available. Natural plant antimicrobial solution (PAMs) is a Chinese herbal medicine which has been used for decades without toxicity and has multiple medical functions including anti- inflammatory effects. Here, we report the effects of PAMs on glioblastoma growth.

METHODS

The growth of TMZ -sensitive (U251S),-resistant (U251R) human glioma cells, and mouse glioma cell line GL-26 were assessed by MTS colorimetric assay, colony formation, and cell migration assays. Male C57BL/6 mice were implanted subcutaneously or intracranial with luciferase-positive mouse glioma GL-26 cells and treated with vehicle; MAO A inhibitor clorgyline (10 mg/kg); TMZ (1 mg/kg); PAMs (48 mg/kg) alone or in combination with TMZ (1 mg/kg) for 14 days. At the end of the treatment, mice were sacrificed, MAO A catalytic activity in tumors was measured, and tumor sizes were determined by imaging and weight.

RESULTS

These results show that PAMs inhibits MAO A catalytic activity in all three glioma cell lines studied U251S, U251R, and GL-26. PAMs reduced glioma growth and has greater effects in combination with low dose of TMZ than PAMS or TMZ alone in all three cell lines as shown by MTS, colony formation, and cell migration assays. Using the subcutaneous or intracranial GL-26 glioma mouse model, PAMs reduced the tumor growth and MAO A activity, similar to the MAO A inhibitor clorgyline. Combining PAMs with non-toxic dose TMZ increased survival to a greater extent than those of PAMs or TMZ alone.

CONCLUSIONS

This is the first study which suggests that PAMs alone or co-administration with low doses of TMZ may be a potential adjuvant to reduce the toxicity of TMZ and to abrogate drug resistance for the effective treatment of glioma.

PARP inhibitor cyanine dye conjugate with enhanced cytotoxic and antiproliferative activity in patient derived glioblastoma cell lines

We describe the synthesis and in vitro activity of drug-dye conjugate 1, which is a combination of the PARP inhibitor rucaparib and heptamethine cyanine dye IR-786. The drug-dye conjugate 1 was evaluated in three different patient-derived glioblastoma cell lines and showed strong cytotoxic activity with nanomolar potency (EC₅₀: 128 nM), which was a 780 fold improvement over rucaparib itself. We also observe a synergistic effect of 1 with temozolomide (TMZ), the standard drug for treatment for glioblastoma even though these cell lines were resistant to TMZ treatment. We envisage such conjugates to be worth exploring for their utility in the treatment of various brain cancers.

A Self-Assembled "Albumin-Conjugate" Nanoprobe for Near Infrared Optical Imaging of Subcutaneous and Metastatic Tumors

The need for in situ accurate identification of tumor assisted real-time image-guided surgical resection calls for new near-infrared fluorescence agents with high tumor-sensitivity and excellent biocompatibility. Here, an albumin-conjugate nanoparticle system HSA-Er-RI-Cl was designed, synthesized, and applied in cancer imaging, which simultaneously achieved the EPR effect, hypoxia-targeting, and EGFR-targeting property. Our novel nanoprobe is composed of human serum albumin (HSA) and double-targeting small molecule conjugate (Er-RI-Cl): a hypoxia-targeting heptamethine carbocyanine dye (RI-Cl) conjugated with a clinic anti-EGFR antagonist (Erlotinib) by covalent bonding. This conjugate could bind to albumin proteins, forming albumin-conjugate complexes, and those complexes self-assemble into particles with diameters of approximately 100 nm in the aqueous solution. The tumor hypoxia and EGFR targeting specificity of HSA-Er-RI-Cl was, respectively, evaluated in vitro and in vivo. Using murine xenograft subcutaneous and brain metastatic tumor models, we demonstrated that HSA-Er-RI-Cl is a highly potent tumor-targeting NIR agent for noninvasive imaging with remarkable tumor localization and excellent pharmacokinetic properties.

Hypoxia-responsive nanoparticle based drug delivery systems in cancer therapy: An up-to-date review

Hypoxia is a salient feature observed in most solid malignancies that holds a pivotal role in angiogenesis, metastasis and resistance to conventional cancer therapeutic approaches, and thus enables cancer progression. However, the typical characteristics of hypoxic cells such as low oxygen levels and highly bio-reductive environment can offer stimuli-responsive drug release to aid in tumor-specific chemo, radio, photodyanamic and sonodynamic therapies. This approach based on targeting the poorly oxygenated tumor habitats offers the prospective to overcome the difficulties that arises due to heterogenic nature of tumor and could be possibly used in the design of diagnostic as well as therapeutic nanocarriers for targeting various types of solid cancers. Consequently, hypoxia triggered nanoparticle based drug delivery systems is a rapidly progressing research area in developing effective strategies to combat drug-resistance in solid tumors. The present review presents the recent advances in the development of hypoxia-responsive nanovehicles for drug delivery to heterogeneous tumors. The initial sections of the article provides insights into the development of hypoxia in growing cancer and its role in disease progression. The current limitations and the future prospective of hypoxia-stimulated nanomachines for cancer treatment are also discussed.

Synthesis and Biological Evaluation of Genistein-IR783 Conjugate: Cancer Cell Targeted Delivery in MCF-7 for Superior Anti-Cancer Therapy

The flavonoid-based natural product genistein is a biologically active compound possessing promising anti-oxidant and anti-cancer properties. Poor pharmacokinetics along with low potency limit however the therapeutic application of genistein in cancer therapy. In order to overcome those limitations and to expand its therapeutic window of efficacy, we sought to covalently attach genistein with a heptamethine cyanine dye—IR 783—for cancer cell targeting and enhanced delivery to tumors. Herein we report the synthesis, a selective detailed characterization and preliminary in vitro/in vivo biological evaluation of genistein-IR 783 conjugate 4. The conjugate 4 displayed improved potency against human breast cancer MCF-7 cells (10.4 ± 1.0 μM) as compared with the parent genistein (24.8 ± 0.5 μM) or IR 783 (25.7 ± 0.7 μM) and exhibited selective high uptake in MCF-7 as against the normal mammary gland MCF-10A cells in various assays. In the cell viability assay, conjugate 4 exhibited over threefold lower potency against MCF-10A cells (32.1 ± 1.1 μM) suggesting that the anti-cancer profile of parent genistein is significantly improved upon conjugation with the dye IR783. Furthermore, the genistein-IR783 conjugate 4 was shown to be especially accumulated in MCF-7 cancer cells by fluorescent intensity measurements and inverted fluorescence microscopy in fixed cells as well as in live cells with time via live cell confocal fluorescence imaging. The mechanism-based uptake inhibition of conjugate 4 was observed with OATPs inhibitor BSP and in part with amiloride, as a macropinocytosis inhibitor. For the first time we have shown amiloride inhibited uptake of cyanine dye by about ~40%. Finally, genistein-IR 783 conjugate 4 was shown to be localized in MCF-7 tumor xenografts of mice breast cancer model via in vivo near infrared fluorescence (NIRF) imaging. In conclusion, conjugation of genistein with cyanine dye IR783 indeed improved its pharmacological profile by cancer cell selective uptake and targeting and therefore warrants further investigations as a new anti-cancer therapeutics derived from natural product genistein.

A neutral water-soluble mitochondria-targeting polymer

We report the first neutral and water-soluble polymer capable of strong mitochondrial targeting in vitro and in vivo, zwitterionic poly[2-(N-oxide-N,N-diethylamino)ethyl methacrylate] (OPDEA). OPDEA is quickly internalized via macropinocytosis by various cancer cells and transferred into the mitochondria, which slightly lowers the mitochondrial membrane potential as determined by the JC-1 assay.

Conjugation of Dasatinib with MHI-148 Has a Significant Advantageous Effect in Viability Assays for Glioblastoma Cells

We hypothesized that conjugation of the near-infrared dye MHI-148 with the anti-leukemia drug dasatinib might produce a potential theranostic for glioblastoma. In fact, the conjugate was found to bind the kinases Src and Lyn, and to inhibit the viability of a glioblastoma cell line with significantly greater potency than dasatinib alone, MHI-148 alone, or a mixture of dasatinib and MHI-148 at the same concentration. It was also used to successfully image a subcutaneous glioblastoma tumor in vivo.

A Near-IR Fluorescent Dasatinib Derivative That Localizes in Cancer Cells

Kinase inhibitors (KIs) have had a huge impact on clinical treatment of various cancers, but they are far from perfect medicines. In particular, their efficacies are limited to certain cancer types and, in many cases, provide only temporary remission. This paper explores the possibility of covalently binding a fluorophore for in vivo optical imaging to the KI dasatinib where the particular fluorophore chosen for this study, a heptamethine cyanine (Cy) derivative, tends to accumulate in tumors. Thus, we hypothesized that the dasatinib-fluorophore conjugate might target tumor cells more effectively than the parent KI, give enhanced suppression of viability, and simultaneously serve as a probe for optical imaging. As far as we are aware, the dasatinib conjugate (1) is the first reported to contain this KI and a probe for near-IR imaging, and it is certainly the first conjugate of a tumor-targeting near-IR dye and a KI of any kind. Conjugate 1 suppressed the viability of liver cancer cells (HepG2) more effectively than dasatinib at the same concentration. In scratch assays, 1 prevented regrowth of the tumor cells. Conjugate 1 is cell permeable, and confocal imaging indicates the fluorescence of those cells is concentrated in the mitochondria than lysosomes. In general, this study suggests there is untapped potential for conjugates of KIs with tumor-targeting near-IR dyes in the development of theranostics for optical imaging and treatment of cancer.