Discovery of potent ureido tetrahydrocarbazole derivatives for cancer treatments through targeting tumor-associated macrophages

A Review on Carbazole and Its Derivatives as Anticancer Agents From 2013 to 2024

Carbazole, a natural alkaloid, has been recognized as an effective anticancer agent for over 40 years. However, only a limited number of carbazole-based compounds have received FDA approval for cancer treatment. Current cancer therapies are often associated with significant side effects, causing physical, emotional, and financial burdens for patients. Additionally, despite advancements, cancer prevention and treatment remain challenging due to suboptimal clinical outcomes. The development of new drugs is crucial for achieving safer and more effective cancer therapies. This review focuses on various carbazole derivatives and hybrid composites, highlighting their interactions with distinct receptors and their mechanisms of anticancer action, along with a general structure-activity relationship (SAR). It also emphasizes carbazole-based compounds employed in chemoprevention, which aim to delay or prevent malignant progression. By covering carbazole derivatives and their anticancer potential from 2013 to the present, along with their current clinical status, this study offers valuable insights and updates for researchers in the field.

Synthesis and biological evaluation of novel 3,6- amide and thioamide substituted- 2,3,4,9-tetrahydro-1H-carbazoles for anti-cancer activity

Herein, we report the synthesis of new compounds with demonstrated anticancer properties based on the 2,3,4,9-tetrahydro-1H-carbazole scaffold. The Fischer indolization method was used to close the heterocyclic motif. The synthesis method's scope and limitations were thoroughly assessed through a series of experiments. Biological assays revealed that two thioamide compounds exhibited significant anticancer activity against MCF-7, HTC116, and A596 cell lines. Comprehensive in vitro profiling included evaluation of cell cytotoxicity, morphological alterations, colony formation and cell adhesion in 3D cultures, cell cycle analysis, DNA damage induction, impact on mitochondria, and apoptosis. Ex ovo studies further demonstrated these compounds' potential to inhibit angiogenic processes. Our results indicate that the newly developed compounds activate processes leading to DNA damage and disruption of mitochondrial function.

Antifungal Tetrahydrocarbazole Compound CAR-8 Induces Endoplasmic Reticulum Stress in Candida albicans

The development of new effective antifungal agents is essential to combat fungal infections. Tetrahydrocarbazole has been exploited as a promising skeleton against various pathogenic microorganisms and is used to search for novel active antifungal compounds. In this study, a library composed of small tetrahydrocarbazole compounds was screened, and a potent antifungal agent, CAR-8, was identified with a minimum inhibitory concentration of 2-4 μg/mL against Candida albicans. CAR-8 showed strong fungicidal activities and killed almost all C. albicans within 3 h at a concentration of 16 μg/mL. At concentrations of 2 and 8 μg/mL, CAR-8 significantly inhibited the formation of hyphae and biofilms. Moreover, CAR-8 at 10 and 20 mg/kg reduced the fungal load and improved the survival in the C. albicans infection model in the invertebrate Galleria mellonella. Transcriptome analysis revealed significant changes in the expression of genes associated with protein processing in the endoplasmic reticulum (ER), ER-associated degradation, and unfolded protein response (UPR), which suggested that CAR-8 treatment induced ER stress. Moreover, CAR-8 treatment resulted in various phenotypes similar to tunicamycin, a classical ER stress inducer. These included nonconventional splicing of HAC1 mRNA, the fragmented morphology of ER, the distribution changes of GFP-Snc1 in Saccharomyces cerevisiae, and cell apoptosis probably caused by ER stress. More importantly, the disruption of IRE1 or HAC1 increased the sensitivity of C. albicans to CAR-8, confirming that the UPR signaling pathway was critical for CAR-8 resistance. Overall, our study identifies a potent ER stress-induced antifungal compound that will help the discovery of new antifungal drugs.

The cross-talk between macrophages and tumor cells as a target for cancer treatment

Macrophages represent an important component of the innate immune system. Under physiological conditions, macrophages, which are essential phagocytes, maintain a proinflammatory response and repair damaged tissue. However, these processes are often impaired upon tumorigenesis, in which tumor-associated macrophages (TAMs) protect and support the growth, proliferation, and invasion of tumor cells and promote suppression of antitumor immunity. TAM abundance is closely associated with poor outcome of cancer, with impediment of chemotherapy effectiveness and ultimately a dismal therapy response and inferior overall survival. Thus, cross-talk between cancer cells and TAMs is an important target for immune checkpoint therapies and metabolic interventions, spurring interest in it as a therapeutic vulnerability for both hematological cancers and solid tumors. Furthermore, targeting of this cross-talk has emerged as a promising strategy for cancer treatment with the antibody against CD47 protein, a critical macrophage checkpoint recognized as the "don't eat me" signal, as well as other metabolism-focused strategies. Therapies targeting CD47 constitute an important milestone in the advancement of anticancer research and have had promising effects on not only phagocytosis activation but also innate and adaptive immune system activation, effectively counteracting tumor cells' evasion of therapy as shown in the context of myeloid cancers. Targeting of CD47 signaling is only one of several possibilities to reverse the immunosuppressive and tumor-protective tumor environment with the aim of enhancing the antitumor response. Several preclinical studies identified signaling pathways that regulate the recruitment, polarization, or metabolism of TAMs. In this review, we summarize the current understanding of the role of macrophages in cancer progression and the mechanisms by which they communicate with tumor cells. Additionally, we dissect various therapeutic strategies developed to target macrophage-tumor cell cross-talk, including modulation of macrophage polarization, blockade of signaling pathways, and disruption of physical interactions between leukemia cells and macrophages. Finally, we highlight the challenges associated with tumor hypoxia and acidosis as barriers to effective cancer therapy and discuss opportunities for future research in this field.

Current scenario of pyrazole hybrids with in vivo therapeutic potential against cancers

Chemotherapeutics occupy a pivotal role in the medication of different types of cancers, but the prevalence and mortality rates of cancer remain high. The drug resistance and low specificity of current available chemotherapeutics are the main barriers for the effective cancer chemotherapy, evoking an immediate need for the development of novel anticancer agents. Pyrazole is a highly versatile five-membered heterocycle with two adjacent nitrogen atoms and possesses remarkable therapeutic effects and robust pharmacological potency. The pyrazole derivatives especially pyrazole hybrids have demonstrated potent in vitro and in vivo efficacies against cancers through multiple mechanisms, inclusive of apoptosis induction, autophagy regulation, and cell cycle disruption. Moreover, several pyrazole hybrids such as crizotanib (pyrazole-pyridine hybrid), erdafitinib (pyrazole-quinoxaline hybrid) and ruxolitinib (pyrazole-pyrrolo [2,3-d]pyrimidine hybrid) have already been approved for the cancer therapy, revealing that pyrazole hybrids are useful scaffolds to develop novel anticancer agents. The purpose of this review is to summarize the current scenario of pyrazole hybrids with potential in vivo anticancer efficacy along with mechanisms of action, toxicity, and pharmacokinetics, covering papers published in recent 5 years (2018-present), to facilitate further rational exploitation of more effective candidates.

The portrayal of macrophages as tools and targets: A paradigm shift in cancer management

Macrophages play a major role in maintaining an organism's physiology, such as development, homeostasis, tissue repair, and immunity. These immune cells are known to be involved in tumor progression and modulation. Monocytes can be polarized to two types of macrophages (M1 macrophages and pro-tumor M2 macrophages). Through this article, we aim to emphasize the potential of targeting macrophages in order to improve current strategies for tumor management. Various strategies that target macrophages as a therapeutic target have been discussed along with ongoing clinical trials. We have discussed the role of macrophages in various stages of tumor progression epithelial-to-mesenchymal transition (EMT), invasion, maintaining the stability of circulating tumor cells (CTCs) in blood, and establishing a premetastatic niche along with the role of various cytokines and chemokines involved in these processes. Intriguingly macrophages can also serve as drug carriers due to their tumor tropism along the chemokine gradient. They surpass currently explored nanotherapeutics in tumor accumulation and circulation half-life. We have emphasized on macrophage-based biomimetic formulations and macrophage-hitchhiking as a strategy to effectively target tumors. We firmly believe that targeting macrophages or utilizing them as an indigenous carrier system could transform cancer management.

Cancer-associated fibroblasts (CAFs) and tumor-associated macrophages (TAMs); where do they stand in tumorigenesis and how they can change the face of cancer therapy?

The tumor microenvironment (TME) and its components have recently attracted tremendous attention in cancer treatment strategies, as alongside the genetic and epigenetic alterations in tumor cells, TME could also provide a fertile background for malignant cells to survive and proliferate. Interestingly, TME plays a vital role in the mediation of cancer metastasis and drug resistance even against immunotherapeutic agents. Among different cells that are presenting in TME, tumor-associated macrophages (TAMs) and cancer-associated fibroblasts (CAFs) have shown to have significant value in the regulation of angiogenesis, tumor metastasis, and drug-resistance through manipulating the composition as well as the organization of extracellular matrix (ECM). Evidence has shown that the presence of both TAMs and CAFs in TME is associated with poor prognosis and failure of chemotherapeutic agents. It seems that these cells together with ECM form a shield around tumor cells to protect them from the toxic agents and even the adaptive arm of the immune system, which is responsible for tumor surveillance. Given this, targeting TAMs and CAFs seems to be an essential approach to potentiate the cytotoxic effects of anti-cancer agents, either conventional chemotherapeutic drugs or immunotherapies. In the present review, we aimed to take a deep look at the mechanobiology of CAFs and TAMs in tumor progression and to discuss the available therapeutic approaches for harnessing these cells in TME.

Indole Alkaloids, Synthetic Dimers and Hybrids with Potential In Vivo Anticancer Activity

Indole, a heterocyclic organic compound, is one of the most promising heterocycles found in natural and synthetic sources since its derivatives possess fascinating structural diversity and various therapeutic properties. Indole alkaloids, synthetic dimers and hybrids could act on diverse targets in cancer cells, and consequently, possess potential antiproliferative effects on various cancers both in vitro and in vivo. Vinblastine, midostaurin, and anlotinib as the representative of indole alkaloids, synthetic dimers and hybrids respectively, have already been clinically applied to treat many types of cancers, demonstrating indole alkaloids, synthetic dimers and hybrids are useful scaffolds for the development of novel anticancer agents. Covering articles published between 2010 and 2020, this review emphasizes the recent development of indole alkaloids, synthetic dimers and hybrids with potential in vivo therapeutic application for cancers.

Systematic approach in macrophage polarization experiments: Maintaining integrity and reproducibility using flow cytometry and sample preparation

Resolution of inflammation is an important physiological process following infection or injury. When inflammation fails to resolve, it can cause chronic inflammation, which exacerbates a myriad of diseases. Current anti-inflammatory treatment options are often inadequate to resolve inflammation, and as such, a key goal for drug discovery is to find natural products and novel compounds that can target immune resolution processes. In order to efficiently discovery new therapies, immune cell lines are often used, in conjunction with flow cytometry, to quickly and inexpensively screen potential drugs for immunomodulatory effects. However, seemingly minor or trivial differences in methodology can lead to inconsistent results across experiments and across laboratories. It was the goal of this project to examine the effects of those differences on the RAW 264.7 macrophage cell line, particularly as it relates to macrophage polarization experimentation. We found that the type of detachment method when preparing cells for flow cytometry can alter several key macrophage parameters, including markers for macrophage polarization, depending on the gating strategy used in identifying sub-populations of cells for analysis. Investigators need to incorporate best-practices in gating strategy in order to target viable cells that are not in aggregate to ensure consistent and reliable results for immunomodulatory drug discovery.

Tumor-associated macrophages: role in tumorigenesis and immunotherapy implications

Tumor-associated macrophages (TAMs) occupy an important position in the tumor microenvironment (TME), they are a highly plastic heterogeneous population with complex effects on tumorigenesis and development. TAMs secrete a variety of cytokines, chemokines, and proteases, which promote the remodeling of extracellular matrix, tumor cell growth and metastasis, tumor vessel and lymphangiogenesis, and immunosuppression. TAMs with different phenotypes have different effects on tumor proliferation and metastasis. TAMs act a pivotal part in occurrence and development of tumors, and are very attractive target to inhibit tumor growth and metastasis in tumor immunotherapy. This article reviews the interrelationship between TAMs and tumor microenvironment and its related applications in tumor therapy.

Targeting tumor-associated macrophages: A potential treatment for solid tumors

Tumor-associated macrophages (TAMs) in solid tumors exert protumor activities by releasing cytokines or growth factors into the tumor microenvironment. Increasing studies have also shown that TAMs play a key role in tumor progression, such as tumor angiogenesis, immunosuppression, cell proliferation, migration, invasion, and metastasis. A large body of evidence shows that the abundance of TAMs in solid tumors is correlated with poor disease prognosis and resistance to therapies. Therefore, targeting TAMs in solid tumors is considered to be a promising immunotherapeutic strategy. At present, the therapeutic strategies of targeting macrophages mainly include limiting monocyte recruitment, depletion strategies, promoting macrophage phagocytic activity, and induction of macrophage reprogramming. Additionally, targeting TAMs in combination with conventional therapies has been demonstrated to be a promising therapeutic strategy in solid tumors. In the present review, we summarized various TAMs-targeting therapeutic strategies for treating solid tumors. This review also discusses the challenges for targeting TAMs as tumor treatments, the obstacles in clinical trials, and the perspective for the future development of TAMs-targeting therapies for various cancers.