Epidermal Growth Factor Receptor and its Trafficking Regulation by Acetylation: Implication in Resistance and Exploring the Newer Therapeutic Avenues in Cancer

Design, synthesis, and anticancer assessment of structural analogues of (E)-1-((3,4,5-trimethoxybenzylidene)amino)-4-(3,4,5-trimethoxyphenyl)imidazo[1,2-a]quinoxaline-2-carbonitrile (6b), an imidazo[1,2-a]quinoxaline-based non-covalent EGFR inhibitor

In our quest to find improved anticancer therapeutics, we expedite the lead optimization of (E)-1-((3,4,5-trimethoxybenzylidene)amino)-4-(3,4,5-trimethoxyphenyl)imidazo[1,2-a]quinoxaline-2-carbonitrile (6b), an EGFR inhibitor previously discovered in our laboratory through an in-house screening program. The lead optimization was rationally initiated considering the catalytic site of EGFR. We synthesized twenty-nine new analogues of 6b and assessed their anticancer activities. SAR studies highlighted the role of important groups in controlling anticancer activities. Among all, 5a and 5l were found to exhibit improved EGFR inhibition with anticancer asset potential. In silico studies corroborated with in vitro EGFR inhibitory results. The deeper analysis of 5a and 5l revealed that these synthetics could alter the MMP (ΔΨ m) and significantly reduce the ROS levels in lung cancer cells. This is a vital prerequisite for better plausible EGFR inhibitors devoid of cardiotoxicity. qPCR analysis further revealed that the investigational compounds 5a and 5l were able to downregulate the expression of key oncogenes, viz., KRAS, MAP2K, and EGFR. The downregulation of these genes suggests that the investigational compounds could interact and inhibit key players in the signalling cascade along with the EGFR, which may lead to the inhibition of the growth and prognosis of cancer cells via a holistic approach.

PRMT blockade induces defective DNA replication stress response and synergizes with PARP inhibition

Multiple cancers exhibit aberrant protein arginine methylation by both type I arginine methyltransferases, predominately protein arginine methyltransferase 1 (PRMT1) and to a lesser extent PRMT4, and by type II PRMTs, predominately PRMT5. Here, we perform targeted proteomics following inhibition of PRMT1, PRMT4, and PRMT5 across 12 cancer cell lines. We find that inhibition of type I and II PRMTs suppresses phosphorylated and total ATR in cancer cells. Loss of ATR from PRMT inhibition results in defective DNA replication stress response activation, including from PARP inhibitors. Inhibition of type I and II PRMTs is synergistic with PARP inhibition regardless of homologous recombination function, but type I PRMT inhibition is more toxic to non-malignant cells. Finally, we demonstrate that the combination of PARP and PRMT5 inhibition improves survival in both BRCA-mutant and wild-type patient-derived xenografts without toxicity. Taken together, these results demonstrate that PRMT5 inhibition may be a well-tolerated approach to sensitize tumors to PARP inhibition.

Targeting the Epidermal Growth Factor Receptor with Molecular Degraders: State-of-the-Art and Future Opportunities

Epidermal growth factor receptor (EGFR) is an oncogenic drug target and plays a critical role in several cellular functions including cancer cell growth, survival, proliferation, differentiation, and motility. Several small-molecule tyrosine kinase inhibitors (TKIs) and monoclonal antibodies (mAbs) have been approved for targeting intracellular and extracellular domains of EGFR, respectively. However, cancer heterogeneity, mutations in the catalytic domain of EGFR, and persistent drug resistance limited their use. Different novel modalities are gaining a position in the limelight of anti-EGFR therapeutics to overcome such limitations. The current perspective reflects upon newer modalities, importantly the molecular degraders such as PROTACs, LYTACs, AUTECs, and ATTECs, etc., beginning with a snapshot of traditional and existing anti-EGFR therapies including small molecule inhibitors, mAbs, and antibody drug conjugates (ADCs). Further, a special emphasis has been made on the design, synthesis, successful applications, state-of-the-art, and emerging future opportunities of each discussed modality.

In Vivo Anticancer Evaluation of 6b, a Non-Covalent Imidazo[1,2-a]quinoxaline-Based Epidermal Growth Factor Receptor Inhibitor against Human Xenograft Tumor in Nude Mice

Tyrosine kinase inhibitors are validated therapeutic agents against EGFR-mutated non-small cell lung cancer (NSCLC). However, the associated critical side effects of these agents are inevitable, demanding more specific and efficient targeting agents. Recently, we have developed and reported a non-covalent imidazo[1,2-a]quinoxaline-based EGFR inhibitor (6b), which showed promising inhibitory activity against the gefitinib-resistant H1975(L858R/T790M) lung cancer cell line. In the present study, we further explored the 6b compound in vivo by employing the A549-induced xenograft model in nude mice. The results indicate that the administration of the 6b compound significantly abolished the growth of the tumor in the A549 xenograft nude mice. Whereas the control mice bearing tumors displayed a declining trend in the survival curve, treatment with the 6b compound improved the survival profile of mice. Moreover, the histological examination showed the cancer cell cytotoxicity of the 6b compound was characterized by cytoplasmic destruction observed in the stained section of the tumor tissues of treated mice. The immunoblotting and qPCR results further signified that 6b inhibited EGFR in tissue samples and consequently altered the downstream pathways mediated by EGFR, leading to a reduction in cancer growth. Therefore, the in vivo findings were in corroboration with the in vitro results, suggesting that 6b possessed potential anticancer activity against EGFR-dependent lung cancer. 6b also exhibited good stability in human and mouse liver microsomes.

G protein pathway suppressor 2 suppresses gastric cancer by destabilizing epidermal growth factor receptor

G protein pathway suppressor 2 (GPS2) is expressed in most human tissues, including the stomach. However, the biological functions of GPS2 in cancer, as well as the underlying molecular mechanisms, remain poorly understood. Here, we report that GPS2 expression was aberrantly downregulated in gastric cancer (GC) tissues compared with control tissues. Clinicopathologic analysis showed that low GPS2 expression was significantly correlated with pathological grade, lymph node stage, and invasive depth. Kaplan-Meier analysis indicated that patients with low GPS2 expression showed poorer overall survival rates than those with high GPS2 expression. Moreover, GPS2 overexpression decreased GC cell proliferation, colony formation, tumorigenesis, and invasion. Overexpression of GPS2 reduced the protein expression of epidermal growth factor receptor (EGFR) and inhibited its downstream signaling in GC cells. Interestingly, GPS2 decreased EGFR protein expression, which was reversed by a lysosome inhibitor. Furthermore, GPS2 reduced EGFR protein stability by enhancing the binding of EGFR and an E3 ligase, c-Cbl, which promoted the ubiquitination of EGFR, ultimately leading to its degradation through the lysosomal pathway. Further analysis indicated that GPS2 activated autophagy and promoted the autophagic flux by destabilizing EGFR. Taken together, these results suggest that low GPS2 expression is associated with GC progression and provide insights into the applicability of the GPS2-EGFR axis as a potential therapeutic target in GC.

Hybridization of Imidazole with Various Heterocycles in Targeting Cancer: A Decade's Work

Cancer is the world‘s biggest global health concern. The prevalence and mortality rates of cancer remain high despite significant progress in cancer therapy. The search for more effective, as well as less toxic treatment methods for cancer, is at the focus of current studies. Approximately 24.6 million people are suffering from cancer across the world as per the world health organization (WHO). In the year 2020, approximately 10 million deaths were reported due to cancer which has emerged as the second leading cause of mortality across the globe. Anticancer medicines have played a pivotal role in the medication of different types of cancers; however, they are associated with several side effects and relevance of drug resistance which evoke an immediate need for designing of new anticancer agents with multitargeted effect. Imidazole is a heterocyclic compound privileged with considerable anticancer activities and some imidazole derivatives have already got approval to treat cancer. Many hybrid molecules are available that play an important role in the treatment of cancer like chalcone, pyrazole, purine, triazine etc., and their pharmacophore provide the anticancer drug with low drug resistance and high efficacy, with low chances of toxicity and side effects. This review provides various approaches for the drug development of new safe and efficient antitumor agents imidazole hybrids with other heterocyclic moieties. An attempt has been made to advancement of the anticancer potential of the derivatives and hybrids of imidazole having intact or condensed imidazole moiety in the last decade along with the structure‐activity relationship studies, and mechanism of action.

Design and Synthesis of Non-Covalent Imidazo[1,2-a]quinoxaline-Based Inhibitors of EGFR and Their Anti-Cancer Assessment

A series of 30 non-covalent imidazo[1,2-a]quinoxaline-based inhibitors of epidermal growth factor receptor (EGFR) were designed and synthesized. EGFR inhibitory assessment (against wild type) data of compounds revealed 6b, 7h, 7j, 9a and 9c as potent EGFRWT inhibitors with IC50 values of 211.22, 222.21, 193.18, 223.32 and 221.53 nM, respectively, which were comparable to erlotinib (221.03 nM), a positive control. Furthermore, compounds exhibited excellent antiproliferative activity when tested against cancer cell lines harboring EGFRWT; A549, a non-small cell lung cancer (NSCLC), HCT-116 (colon), MDA-MB-231 (breast) and gefitinib-resistant NSCLC cell line H1975 harboring EGFRL858R/T790M. In particular, compound 6b demonstrated significant inhibitory potential against gefitinib-resistant H1975 cells (IC50 = 3.65 μM) as compared to gefitinib (IC50 > 20 μM). Moreover, molecular docking disclosed the binding mode of the 6b to the domain of EGFR (wild type and mutant type), indicating the basis of inhibition. Furthermore, its effects on redox modulation, mitochondrial membrane potential, cell cycle analysis and cell death mode in A549 lung cancer cells were also reported.

Inhibition of histone deacetylases, topoisomerases and epidermal growth factor receptor by metal-based anticancer agents: Design & synthetic strategies and their medicinal attributes

Metal-based inhibitors of histone deacetylases (HDAC), DNA topoisomerases (Topos) and Epidermal Growth Factor Receptor (EGFR) have demonstrated their cytotoxic potential against various cancer types such as breast, lung, uterus, colon, etc. Additionally, these have proven their role in resolving the resistance issues, enhancing the affinity, lipophilicity, stability, and biocompatibility and therefore, emerged as potential candidates for molecularly targeted therapeutics. This review focusses on nature and role of metals and organic ligands in tuning the anticancer activity in multiple modes of inhibition considering HDACs, Topos or EGFR as one of the primary targets. The conceptual design and synthetic approaches of platinum and non-platinum metal complexes comprising of chiefly ruthenium, rhodium, palladium, copper, iron, nickel, cobalt, zinc metals coordinated with organic scaffolds, along with their biological activity profiles, structure-activity relationships (SARs), docking studies, possible modes of action, and their scope and limitations are discussed in detail.