Novel Imidazopyridine Derivatives Possess Anti-Tumor Effect on Human Castration-Resistant Prostate Cancer Cells

Imidazopyridine Family: Versatile and Promising Heterocyclic Skeletons for Different Applications

In recent years, there has been increasing attention focused on various products belonging to the imidazopyridine family; this class of heterocyclic compounds shows unique chemical structure, versatile optical properties, and diverse biological attributes. The broad family of imidazopyridines encompasses different heterocycles, each with its own specific properties and distinct characteristics, making all of them promising for various application fields. In general, this useful category of aromatic heterocycles holds significant promise across various research domains, spanning from material science to pharmaceuticals. The various cores belonging to the imidazopyridine family exhibit unique properties, such as serving as emitters in imaging, ligands for transition metals, showing reversible electrochemical properties, and demonstrating biological activity. Recently, numerous noteworthy advancements have emerged in different technological fields, including optoelectronic devices, sensors, energy conversion, medical applications, and shining emitters for imaging and microscopy. This review intends to provide a state-of-the-art overview of this framework from 1955 to the present day, unveiling different aspects of various applications. This extensive literature survey may guide chemists and researchers in the quest for novel imidazopyridine compounds with enhanced properties and efficiency in different uses.

Identification of an Imidazopyridine-based Compound as an Oral Selective Estrogen Receptor Degrader for Breast Cancer Therapy

The pro-oncogenic activities of estrogen receptor alpha (ERα) drive breast cancer pathogenesis. Endocrine therapies that impair the production of estrogen or the action of the ERα are therefore used to prevent primary disease metastasis. Although recent successes with ERα degraders have been reported, there is still the need to develop further ERα antagonists with additional properties for breast cancer therapy. We have previously described a benzothiazole compound A4B17 that inhibits the proliferation of androgen receptor-positive prostate cancer cells by disrupting the interaction of the cochaperone BAG1 with the AR. A4B17 was also found to inhibit the proliferation of estrogen receptor-positive (ER+) breast cancer cells. Using a scaffold hopping approach, we report here a group of small molecules with imidazopyridine scaffolds that are more potent and efficacious than A4B17. The prototype molecule X15695 efficiently degraded ERα and attenuated estrogen-mediated target gene expression as well as transactivation by the AR. X15695 also disrupted key cellular protein-protein interactions such as BAG1-mortalin (GRP75) interaction as well as wild-type p53-mortalin or mutant p53-BAG2 interactions. These activities together reactivated p53 and resulted in cell-cycle block and the induction of apoptosis. When administered orally to in vivo tumor xenograft models, X15695 potently inhibited the growth of breast tumor cells but less efficiently the growth of prostate tumor cells. We therefore identify X15695 as an oral selective ER degrader and propose further development of this compound for therapy of ER+ breast cancers.

Significance

An imidazopyridine that selectively degrades ERα and is orally bioavailable has been identified for the development of ER+ breast cancer therapeutics. This compound also activates wild-type p53 and disrupts the gain-of-function tumorigenic activity of mutant p53, resulting in cell-cycle arrest and the induction of apoptosis.

Mono-, Bis-, and Tris-Chelate Zn(II) Complexes with Imidazo[1,5-a]pyridine: Luminescence and Structural Dependence

New mono-, bis-, and tris-chelate Zn(II) complexes have been synthesized starting from different Zn(II) salts and employing a fluorescent 1,3-substituted-imidazo[1,5-a]pyridine as a chelating ligand. The products have been characterized by single-crystal X-ray diffraction; mass spectrometry; and vibrational spectroscopy. The optical properties have been investigated to compare the performances of mono-, bis-, and tris-chelate forms. The collected data (in the solid state and in solution) elucidate an important modification of the ligand conformation upon metal coordination; which is responsible for a notable increase in the optical performance. An intense modification of the emission quantum yield along the series in the solid state is observed comparing mono-, bis-, and tris-chelate adducts; independently from the anionic ligand introduced by ionic exchange.

The Anticancer Effects of Novel Imidazo[1,2-a]Pyridine Compounds against HCC1937 Breast Cancer Cells

BACKGROUND

Anticancer drugs confront clinical obstacles such as drug resistance and adverse effects. Imidazo[1,2-a]pyridines (IPs) compounds have lately gained considerable interest as possible anticancer therapeutics due to their potent inhibitory function against cancers cells. This study was to determine the anticancer activities of three novel IPs (IP-5, IP-6, and IP-7) against the HCC1937 breast cancer cell line in vitro.

MATERIALS AND METHODS

The cytotoxic and anti-proliferative effects of IPs compounds in HCC1937 cells were determined by cell viability (MTT) assay, trypan blue assay, and clonogenic survival assay. Scratch motility assay was used to test the antimigration ability of the IPs. Western blot analysis was carried out to detect the level of apoptosis and cell cycle protein markers and to understand the mechanism of action of IPs compounds.

RESULTS

IP-5 and IP-6 have a strong cytotoxic impact against HCC1937 cells with IC50 values of 45µM and 47.7µM respectively. IP-7 possesses less cytotoxic effect against HCC1937 cells with IC50 of 79.6µM. Trypan blue assay showed that the three compounds induce significant cell death in the HCC1937 cells. Clonogenic and mammosphere assays demonstrated that IP-5 reduced the HCC1937 cells survival rate by more than 25.0% at 1000 cell concentrations. Western blotting analysis showed that IP-5 compound causes cell cycle arrest as noted by the increasing levels of p53 and p21 in treated cells. IP-5 induced an extrinsic apoptosis pathway as reveals from the increased activity of caspase 7, caspase 8, and the increasing level of PARP cleavage in treated cells. Also, IP-5 treated cells revealed segmented chromatin which is characteristic of apoptotic cells as shown by DAPI stain. Importantly, In comparison to control cells, IP-5-treated cells exhibited lower levels of pAKT.

CONCLUSIONS

The novel three IPs compounds represent potential active anticancer compounds against HCC1937 breast cancer cells in vitro.

A Novel Imidazo[1,2-a]pyridine Compound Reduces Cell Viability and Induces Apoptosis of HeLa Cells by p53/Bax-Mediated Activation of Mitochondrial Pathway

BACKGROUND

Despite emerging research on new treatment strategies, chemotherapy remains one of the most important therapeutic modalities for cancers. Imidazopyridines are important targets in organic chemistry and are worthy of attention given their numerous applications.

OBJECTIVE

To design and synthesize a novel series of imidazo[1,2-a]pyridine-derived compounds and investigate their antitumor effects and the underlying mechanisms.

METHODS

Imidazo[1,2-a]pyridine-derived compounds were synthesized with new strategies and conventional methods. The antitumor activities of the new compounds were evaluated by MTT assay. Flow cytometry and immunofluorescence were performed to examine the effects of the most effective antiproliferative compound on cell apoptosis. Western blot analysis was used to assess the expression of apoptotic proteins.

RESULTS

Fifty-two new imidazo[1,2-a]pyridine compounds were designed and successfully synthesized. The compound, 1-(imidazo[1,2-a]pyridin-3-yl)-2-(naphthalen-2-yl)ethane-1,2-dione, named La23, showed high potential for suppressing the viability of HeLa cells (IC50 15.32 μM). La23 inhibited cell proliferation by inducing cell apoptosis, and it reduced the mitochondrial membrane potential of HeLa cells. Moreover, treatment with La23 appeared to increase the expression of apoptotic-related protein P53, Bax, cleaved caspase-3, and cytochrome c at a low concentration range.

CONCLUSION

The novel imidazo[1,2-a]pyridine compound, La23, was synthesized and suppressed cell growth by inducing cell apoptosis via the p53/Bax mitochondrial apoptotic pathway.

Targeting treatment options for castration-resistant prostate cancer

Prostate cancer (PCa) is the most commonly diagnosed solid tumor and the second leading cause of cancer-related deaths in U.S. men in 2020. Androgen-deprivation therapy (ADT) is the standard of care for metastatic PCa. Unfortunately, PCa relapse often occurs one to two years after initiation of ADT, resulting in the development of castration-resistant PCa (CRPCa), a lethal disease. While several anticancer agents such as docetaxel, abiraterone acetate, and enzalutamide are currently utilized to extend a patient's life after development of CRPCa, patients will eventually succumb to the disease. Hence, while targeting androgen signaling and utilization of docetaxel remain the most crucial agents for many of these combinations, many studies are attempting to exploit other vulnerabilities of PCa cells, such as inhibition of key survival proteins, anti-angiogenesis agents, and immunotherapies. This review will focus on discussing recent advances on targeting therapy. Several novel small molecules will also be discussed.

Imidazo[1,5-a]pyridine derivatives: useful, luminescent and versatile scaffolds for different applications

In the last few years, imidazo[1,5-a]pyridine nuclei and derivatives have attracted growing attention due to their unique chemical structure and versatility, optical behaviours, and biological properties.

Novel imidazo[1,2-a]pyridine inhibits AKT/mTOR pathway and induces cell cycle arrest and apoptosis in melanoma and cervical cancer cells

The present study aimed to investigate the anti-cancer activity of imidazo[1,2-a]pyridine 5–7 in the A375 and WM115 melanoma and HeLa cervical cancer cell lines. The viability of cancer cells was analyzed by the MTT assay. Apoptosis was quantified by flow cytometry following staining of the cells with AnnexinV/propidium iodide (PI). The cell cycle was evaluated by flow cytometry after staining of cells with PI. The three compounds inhibited the proliferation of all cells for half maximal inhibitory concentration ranging from 9.7 to 44.6 µM following 48-h treatment. In addition, all cancer cells were more sensitive to compound 6 compared with the other compounds. Treatment with compound 6 induced G₂/M cell cycle arrest and a significant increased level of intrinsic apoptosis in all tested cells. Furthermore, compound 6 reduced the levels of phospho (p)-protein kinase B and p-mechanistic target of rapamycin, and increased levels of the cell cycle inhibitors p53 and p21 and of the apoptosis-associated proteins BCL2 associated X protein and active caspase-9. Silencing p53 in A375 melanoma cells reduced compound 6-induced apoptosis, which suggested that compound 6 may induce p53-partially mediated apoptosis. These results demonstrated that imidazo[1,2-a]pyridines 5–7 are potential effective compounds in the treatment of melanoma and cervical cancers.

Synthesis of novel imidazopyridines and their biological evaluation as potent anticancer agents: A promising candidate for glioblastoma

Novel imidazopyridine derivatives were synthesized according to a very simple protocol and then subjected to cytotoxicity testing against LN-405 cells. Two of the compounds exhibited antiproliferative effects on LN-405 cells at 10 and 75 µM and were selected as lead compounds for further study. Safety experiment for lead compounds on WS1 was carried out and IC₅₀ values were calculated as 480 and 844 µM. LN-405 cell line were incubated with the lead compounds and then tested for DNA damage by comet assay and effects on cell cycle using flow cytometry. The results of these two tests showed that both lead compounds affected the G0/G1 phase and did not allow the cells to reach the synthesis phase. The log BB (blood-brain barrier) and Caco-2 permeability of the synthesized molecules were calculated and it was shown that imidazopyridine derivatives taken orally are likely to pass through gastrointestinal membrane and the blood-brain barrier.

p66Shc regulates migration of castration-resistant prostate cancer cells

Metastatic castration-resistant (CR) prostate cancer (PCa) is a lethal disease for which no effective treatment is currently available. p66Shc is an oxidase previously shown to promote androgen-independent cell growth through generation of reactive oxygen species (ROS) and is elevated in clinical PCa and multiple CR PCa cell lines. We hypothesize p66Shc also increases the migratory activity of PCa cells through ROS and investigate the associated mechanism. Using the transwell assay, our study reveals that the level of p66Shc protein correlates with cell migratory ability across several PCa cell lines. Furthermore, we show hydrogen peroxide treatment induces migration of PCa cells that express low levels of p66Shc in a dose-dependent manner, while antioxidants inhibit migration. Conversely, PCa cells that express high levels of endogenous p66Shc or by cDNA transfection possess increased cell migration which is mitigated upon p66Shc shRNA transfection or expression of oxidase-deficient dominant-negative p66Shc W134F mutant. Protein microarray and immunoblot analyses reveal multiple proteins, including ErbB-2, AKT, mTOR, ERK, FOXM1, PYK2 and Rac1, are activated in p66Shc-elevated cells. Their involvement in PCa migration was examined using respective small-molecule inhibitors. The role of Rac1 was further validated using cDNA transfection and, significantly, p66Shc is found to promote lamellipodia formation through Rac1 activation. In summary, the results of our current studies clearly indicate p66Shc also regulates PCa cell migration through ROS-mediated activation of migration-associated proteins, notably Rac1.

Baicalein suppresses the androgen receptor (AR)-mediated prostate cancer progression via inhibiting the AR N-C dimerization and AR-coactivators interaction

BACKGROUND

Androgen receptor (AR) plays a critical role in prostate cancer (PCa) development and progression. Androgen deprivation therapy with antiandrogens to reduce androgen biosynthesis or prevent androgens from binding to AR are widely used to suppress AR-mediated PCa growth. However, most of ADT may eventually fail with development of the castration resistance after 12-24 months. Here we found that a natural product baicalein can effectively suppress the PCa progression via targeting the androgen-induced AR transactivation with little effect to AR protein expression.

METHODS

PCa cells including LNCaP, CWR22Rv1, C4-2, PC-3, and DU145, were treated with baicalein and luciferase assay was used to evaluate their effect on the AR transactivation. Cell growth and IC50 were determined by MTT assay after 48 hrs treatment. RT-PCR was used to evaluate the mRNA levels of AR target genes including PSA, TMPRSS2, and TMEPA1. Western blot was used to determine AR and PSA protein expression.

RESULTS

The natural product of baicalein can selectively inhibit AR transactivation with little effect on the other nuclear receptors, including ERα, and GR. At a low concentration, 2.5 μM of baicalein effectively suppresses the growth of AR-positive PCa cells, and has little effect on AR-negative PCa cells. Mechanism dissection suggest that baicalein can suppress AR target genes (PSA, TMPRSS2, and TMEPA1) expression in both androgen responsive LNCaP cells and castration resistant CWR22Rv1 cells, that may involve the inhibiting the AR N/C dimerization and AR-coactivators interaction.

CONCLUSIONS

Baicalein may be developed as an effective anti-AR therapy via its ability to inhibit AR transactivation and AR-mediated PCa cell growth.

Statin derivatives as therapeutic agents for castration-resistant prostate cancer

Despite recent advances in modern medicine, castration-resistant prostate cancer remains an incurable disease. Subpopulations of prostate cancer cells develop castration-resistance by obtaining the complete steroidogenic ability to synthesize androgens from cholesterol. Statin derivatives, such as simvastatin, inhibit cholesterol biosynthesis and may reduce prostate cancer incidence as well as progression to advanced, metastatic phenotype. In this study, we demonstrate novel simvastatin-related molecules SVA, AM1, and AM2 suppress the tumorigenicity of prostate cancer cell lines including androgen receptor-positive LNCaP C-81 and VCaP as well as androgen receptor-negative PC-3 and DU145. This is achieved through inhibition of cell proliferation, colony formation, and migration as well as induction of S-phase cell-cycle arrest and apoptosis. While the compounds effectively block androgen receptor signaling, their mechanism of inhibition also includes suppression of the AKT pathway, in part, through disruption of the plasma membrane. SVA also possess an added effect on cell growth inhibition when combined with docetaxel. In summary, of the compounds studied, SVA is the most potent inhibitor of prostate cancer cell tumorigenicity, demonstrating its potential as a promising therapeutic agent for castration-resistant prostate cancer.