The novel STAT3 inhibitor WZ-2-033 causes regression of human triple-negative breast cancer and gastric cancer xenografts

Discovery of novel STAT3 inhibitors with anti-breast cancer activity: structure-based virtual screening, molecular dynamics and biological evaluation

Triple negative breast cancer (TNBC) is a fatal type of breast cancer due to its high recurrence and metastatic potential. Persistent activation of signal transducer and activator of transcription 3 (STAT3) is crucial for TNBC progression, making it an attractive drug target. In this study, two new STAT3 inhibitors with significant anti-TNBC activity, d2 and d10, were identified from 1.67 million candidates through a rapid and cost-effective strategy integrating high-throughput virtual screening (HTVS), molecular mechanics/generalized born surface area (MM/GBSA), and binding pose metadynamics (BPMD) methods. In-depth mechanistic studies revealed that d2 and d10 significantly inhibited cell proliferation and colony formation, induced G1 phase arrest, and reduced migration and invasion of TNBC cells. Moreover, both d2 and d10 were found to inhibit the nuclear translocation and phosphorylation of STAT3. Molecular dynamics simulations further indicated that both compounds can stably bind to STAT3 in the SH2 domain. Additionally, protein-ligand interaction fingerprints (IFPs) of the screened compounds from HTVS were generated to better guide the design and structural optimization of STAT3 inhibitors.

Structural optimization and characterization of highly potent and selective STAT3 inhibitors for the treatment of triple negative breast cancer

Effective targeted treatments for triple-negative breast cancer (TNBC), which has the worst prognosis among various types of breast cancer, are lacking owing to its clinical heterogeneity and malignant nature. STAT3, a key transcription factor, regulates multiple physiological functions. Aberrant activation of STAT3 plays a pivotal role in the initiation and progression of TNBC and is closely associated with a poor prognosis. Therefore, targeting STAT3 is a promising potential therapeutic approach for TNBC. In this study, we further optimized the core structure of 6f, which our research group previously identified as a STAT3 inhibitor and treatment for osteosarcoma, to identify additional potential STAT3 inhibitors for TNBC treatment. We identified WR-S-462 as a high-binding affinity inhibitor of STAT3 that effectively suppresses its phosphorylation and biological functions in vitro. Notably, WR-S-462 significantly inhibits TNBC growth and metastasis in a dose-dependent manner, providing robust evidence for its potential as a clinical intervention for TNBC.

STAT3 Signaling Pathway in Health and Disease

Signal transducer and activator of transcription 3 (STAT3) is a critical transcription factor involved in multiple physiological and pathological processes. While STAT3 plays an essential role in homeostasis, its persistent activation has been implicated in the pathogenesis of various diseases, particularly cancer, bone-related diseases, autoimmune disorders, inflammatory diseases, cardiovascular diseases, and neurodegenerative conditions. The interleukin-6/Janus kinase (JAK)/STAT3 signaling axis is central to STAT3 activation, influencing tumor microenvironment remodeling, angiogenesis, immune evasion, and therapy resistance. Despite extensive research, the precise mechanisms underlying dysregulated STAT3 signaling in disease progression remain incompletely understood, and no United States Food and Drug Administration (USFDA)-approved direct STAT3 inhibitors currently exist. This review provides a comprehensive evaluation of STAT3's role in health and disease, emphasizing its involvement in cancer stem cell maintenance, metastasis, inflammation, and drug resistance. We systematically discuss therapeutic strategies, including JAK inhibitors (tofacitinib, ruxolitinib), Src Homology 2 domain inhibitors (S3I-201, STATTIC), antisense oligonucleotides (AZD9150), and nanomedicine-based drug delivery systems, which enhance specificity and bioavailability while reducing toxicity. By integrating molecular mechanisms, disease pathology, and emerging therapeutic interventions, this review fills a critical knowledge gap in STAT3-targeted therapy. Our insights into STAT3 signaling crosstalk, epigenetic regulation, and resistance mechanisms offer a foundation for developing next-generation STAT3 inhibitors with greater clinical efficacy and translational potential.

PRDX2 promotes gastric cancer progression by forming a feedback loop with PKM2/STAT3 axis

Peroxiredoxin 2 (PRDX2) is an antioxidant enzyme that has been reported to be overexpressed in various cancers. However, the role of PRDX2 in gastric cancer progression and its underlying mechanism remains unclear. Herein, we revealed the function of PRDX2 in gastric cancer progression and explored its molecule mechanism. We identified that PRDX2 was upregulated and associated with poor prognosis in gastric cancer. The knockdown of PRDX2 inhibited the proliferation, migration and invasion of gastric cancer cells in vitro and suppressed tumor growth in vivo. Mechanistically, PRDX2 interacted with PKM2 (pyruvate kinase isozyme type M2) and protected PKM2 from ubiquitination and degradation, which enhanced glycolysis in gastric cancer cells. The interaction between PRDX2 and PKM2 also enhanced the binding affinity between PKM2 and importin α5, which induced PKM2 nuclear translocation and activated STAT3 signaling pathway. In addition, STAT3 (signal transducer and activator of transcription 3) was identified to bind to PRDX2 gene promoter and upregulate PRDX2 expression, which forms a positive regulatory feedback loop in gastric cancer cells. The present study unravels the biological role of PRDX2 in cancer progression and illustrates the underlying molecular mechanism, which may provide a potential therapeutic target for gastric cancer.

Targeting STAT3 for Cancer Therapy: Focusing on Y705, S727, or Dual Inhibition?

BACKGROUND/OBJECTIVES

Signal Transducer and Activator of Transcription 3 (STAT3) is a transcription factor that is strongly implicated in various cancers. In its canonical signaling pathway, Janus kinases (JAKs) phosphorylate STAT3 at the Y705 residue in response to cytokines or growth factors, with pY705 serving as a key marker of STAT3 oncogenic activity. Elevated pY705 levels correlate with poor prognosis, and numerous small-molecule inhibitors have been developed to block this phosphorylation site. More recently, phosphorylation at the S727 residue (pS727) has emerged as a critical contributor to STAT3-mediated oncogenesis, particularly due to its role in mitochondrial translocation. Evidence suggests that pS727 may even surpass pY705 in driving oncogenic activity. These findings prompt an important question: Which residue should be prioritized for effective STAT3 inhibition in cancer therapy?

METHODS

This review compiles and critically analyzes the current literature on STAT3 inhibitors targeting pY705 and/or pS727, evaluating their therapeutic efficacy in vitro, in vivo, and in clinical trials. We assess the unique effects of targeting each residue on downstream signaling, toxicity, and clinical outcomes.

RESULTS

Our analysis indicates that inhibitors targeting both pY705 and pS727 achieve the greatest therapeutic effectiveness. However, pS727 targeting is associated with higher toxicity risks.

CONCLUSIONS

Comprehensive evaluation of STAT3 inhibitors underscores the importance of targeting pY705 for maximum therapeutic benefit. The analysis also shows that co-targeting pS727 may increase overall efficacy. However, pS727 inhibition should be approached with lower affinity to minimize toxicity and enhance the clinical feasibility of dual-targeting strategies.

The anti-cancer mechanism of Celastrol by targeting JAK2/STAT3 signaling pathway in gastric and ovarian cancer

BACKGROUND

Celastrol is a natural triterpene exhibiting significant and extensive antitumor activity in a wide range of cancer. Due to unfavorable toxicity profile and undefined mechanism, Celastrol's application in clinical cancer therapy remains limited. Herein, we elucidate the pharmacological mechanism of Celastrol's anticancer effects, with a focus on STAT3 signaling pathway in cancers with high incidence of metastasis.

METHODS

The safety profile of Celastrol were assessed in mice. In vitro analysis was performed in gastric cancer and ovarian cancer to assess the cytotoxicity, induction of reactive oxygen species (ROS) of Celastrol using STAT3 knockout cancer cells. Effects of Celastrol on STAT3 activation and transcription activity, JAK2/STAT3 signaling protein expression were assessed. Additionally, proteomic contrastive analysis was performed to explore the molecular association of Celastrol with STAT3 deletion in cancer cells.

RESULTS

Celastrol has no obvious toxic effect at 1.5 mg/kg/day in a 15 days' administration. Celastrol inhibits tumor growth and increases ROS in a STAT3 dependent manner in gastric and ovarian cancer celllines. On molecular level, it downregulates IL-6 level and inhibits the JAK2/STAT3 signaling pathway by suppressing STAT3' activation and transcription activity. Proteomic contrastive analysis suggests a similar cellular mechanism of action between Celastrol and STAT3 deletion on regulating cancer progression pathways related to migration and invasion.

CONCLUSION

Our research elucidates the anti-cancer mechanism of Celastrol through targeting the JAK2/STAT3 signaling pathway in cancer with high incidence of metastasis. This study provides a solid theoretical basis for the application of Celastrol in cancer therapy.

Induction, growth, drug resistance, and metastasis: A comprehensive summary of the relationship between STAT3 and gastric cancer

Gastric cancer is a prevalent and highly lethal malignancy that poses substantial challenges to healthcare systems globally. Owing to its often asymptomatic nature in early stages, diagnosis frequently occurs at advanced stages when surgical intervention is no longer a viable option, forcing most patients to rely on nonsurgical treatments such as chemotherapy, targeted therapies, and emerging immunotherapies. Unfortunately, the therapeutic response rates for these treatments are suboptimal, and even among responders, the eventual development of drug resistance remains a significant clinical hurdle. Signal transducer and activator of transcription 3 (STAT3) is a widely expressed cellular protein that plays crucial roles in regulating cellular processes such as growth, metabolism, and immune function. Aberrant activation of the STAT3 pathway has been implicated in the initiation, progression, and therapeutic resistance of several cancers, with gastric cancer being particularly affected. Dysregulated STAT3 signaling not only drives tumorigenesis but also facilitates the development of resistance to chemotherapy and targeted therapies, as well as promotes metastatic dissemination. In this study, we explored the critical role of the STAT3 signaling cascade in the pathogenesis of gastric cancer, its contribution to drug resistance, and its involvement in the metastatic process. Furthermore, we assess recent advances in the development of STAT3 inhibitors and their potential application as therapeutic agents in the treatment of gastric cancer. This work provides a comprehensive overview of the current understanding of STAT3 in gastric cancer and offers a foundation for future research aimed at improving therapeutic outcomes in this challenging disease.

Enhancing cancer therapy: The role of drug delivery systems in STAT3 inhibitor efficacy and safety

The signal transducer and activator of transcription 3 (STAT3), a member of the STAT family, resides in the nucleus to regulate genes essential for vital cellular functions, including survival, proliferation, self-renewal, angiogenesis, and immune response. However, continuous STAT3 activation in tumor cells promotes their initiation, progression, and metastasis, rendering STAT3 pathway inhibitors a promising avenue for cancer therapy. Nonetheless, these inhibitors frequently encounter challenges such as cytotoxicity and suboptimal biocompatibility in clinical trials. A viable strategy to mitigate these issues involves delivering STAT3 inhibitors via drug delivery systems (DDSs). This review delineates the regulatory mechanisms of the STAT3 signaling pathway and its association with cancer. It offers a comprehensive overview of the current application of DDSs for anti-STAT3 inhibitors and investigates the role of DDSs in cancer treatment. The conclusion posits that DDSs for anti-STAT3 inhibitors exhibit enhanced efficacy and reduced adverse effects in tumor therapy compared to anti-STAT3 inhibitors alone. This paper aims to provide an outline of the ongoing research and future prospects of DDSs for STAT3 inhibitors. Additionally, it presents our insights on the merits and future outlook of DDSs in cancer treatment.

WP1066, a small molecule inhibitor of STAT3, chemosensitizes paclitaxel-resistant ovarian cancer cells to paclitaxel by simultaneously inhibiting the activity of STAT3 and the interaction of STAT3 with Stathmin

Paclitaxel is widely used to treat cancer, however, drug resistance limits its clinical utility. STAT3 is constitutively activated in some cancers, and contributes to chemotherapy resistance. Currently, several STAT3 inhibitors including WP1066 are used in cancer clinical trials. However, whether WP1066 reverses paclitaxel resistance and the mechanismremains unknown. Here, we report that in contrast to paclitaxel-sensitive parental cells, the expressions of several pro-survival BCL2 family members such as BCL-2, BCL-XL and MCL-1 are higher in paclitaxel-resistant ovarian cancer cells. Meanwhile, STAT3 is constitutively activated while stathmin loses its activity in paclitaxel-resistant cells. Importantly, WP1066 amplifies the inhibition of cell proliferation, colony-forming ability and apoptosis of ovarian cancer cells induced by paclitaxel. Mechanistically, WP1066, on the one hand, interferes the STAT3/Stathmin interaction, causing unleash of STAT3/Stathmin from microtubule, thus destroying microtubule stability. This process results in reduction of Ac-α-tubulin, further causing MCL-1 reduction. On the other hand, WP1066 inhibits phosphorylation of STAT3 by JAK2, and blocks its nuclear translocation, therefore repressing the transcription of pro-survival targets such as BCL-2, BCL-XL and MCL-1. Finally, the two pathways jointly promote cell death. Our findings reveal a new mechanism wherein WP1066 reverses paclitaxel-resistance of ovarian cancer cells by dually inhibiting STAT3 activity and STAT3/Stathmin interaction, which may layfoundation for WP1066 combined with paclitaxel in treating paclitaxel-resistant ovarian cancer.

Comprehensive analysis revealed the immunoinflammatory targets of rheumatoid arthritis based on intestinal flora, miRNA, transcription factors, and RNA-binding proteins databases, GSEA and GSVA pathway observations, and immunoinfiltration typing

OBJECTIVE

Rheumatoid arthritis (RA) is a chronic inflammatory arthritis. This study aimed to identify potential biomarkers and possible pathogenesis of RA using various bioinformatics analysis tools.

METHODS

The GMrepo database provided a visual representation of the analysis of intestinal flora. We selected the GSE55235 and GSE55457 datasets from the Gene Expression Omnibus database to identify differentially expressed genes (DEGs) separately. With the intersection of these DEGs with the target genes associated with RA found in the GeneCards database, we obtained the DEGs targeted by RA (DERATGs). Subsequently, Disease Ontology, Gene Ontology, and the Kyoto Encyclopedia of Genes and Genomes were used to analyze DERATGs functionally. Gene Set Enrichment Analysis (GSEA) and Gene Set Variation Analysis (GSVA) were performed on the data from the gene expression matrix. Additionally, the protein-protein interaction network, transcription factor (TF)-targets, target-drug, microRNA (miRNA)-mRNA networks, and RNA-binding proteins (RBPs)-DERATGs correlation analyses were built. The CIBERSORT was used to evaluate the inflammatory immune state. The single-sample GSEA (ssGSEA) algorithm and differential analysis of DERATGs were used among the infiltration degree subtypes.

RESULTS

There were some correlations between the abundance of gut flora and the prevalence of RA. A total of 54 DERATGs were identified, mainly related to immune and inflammatory responses and immunodeficiency diseases. Through GSEA and GSVA analysis, we found pathway alterations related to metabolic regulations, autoimmune diseases, and immunodeficiency-related disorders. We obtained 20 hub genes and 2 subnetworks. Additionally, we found that 39 TFs, 174 drugs, 2310 miRNAs, and several RBPs were related to DERATGs. Mast, plasma, and naive B cells differed during immune infiltration. We discovered DERATGs' differences among subtypes using the ssGSEA algorithm and subtype grouping.

CONCLUSIONS

The findings of this study could help with RA diagnosis, prognosis, and targeted molecular treatment.

Integrated transcriptomic and proteomic analysis reveals Guizhi-Fuling Wan inhibiting STAT3-EMT in ovarian cancer progression

BACKGROUND

Ovarian cancer (OC) is the most lethal gynecological malignancy. Frequent peritoneal dissemination is the main cause of low survival rate. Guizhi-Fuling Wan (GZFL) is a classical traditional Chinese herbal formula that has been clinically used for treating ovarian cancer with good outcome. However, its therapeutic mechanism for treating OC has not been clearly elucidated.

PURPOSE

We aim to elucidate the potential mechanisms of GZFL in treating OC with a focus on STAT3 signaling pathway.

METHODS

In vivo efficacy of GZFL was assessed using an OC xenograft mouse model. Proteomics analysis in OC cells and RNA-seq analysis in mice tumors were performed to fully capture the translational and transcriptional signature of GZFL. Effects of GZFL on proliferation, spheroid formation and reactive oxygen species (ROS) were assessed using wildtype and STAT3 knockout OC cells in vitro. STAT3 activation and transcription activity, hypoxia and EMT-related protein expression were assessed to validate the biological activity of GZFL.

RESULTS

GZFL suppresses tumor growth with a safety profile in mice, while prevents cell growth, spheroid formation and accumulates ROS in a STAT3-dependent manner in vitro. GZFL transcriptionally and translationally affects genes involved in inflammatory signaling, EMT, cell migration, and cellular hypoxic stress response. In depth molecular study confirmed that GZFL-induced cytotoxicity and EMT suppression in OC cells are directly corelated to inhibition of STAT3 activation and transcription activity.

CONCLUSION

Our study provides the first evidence that GZFL inhibits OC progression through suppressing STAT3-EMT signaling. These results will further support its potential clinical use in OC.

Identification of Bulbocodin D and C as novel STAT3 inhibitors and their anticancer activities in lung cancer cells

Cancer stands as one of the predominant causes of mortality globally, necessitating ongoing efforts to develop innovative therapeutics. Historically, natural products have been foundational in the quest for anticancer agents. Bulbocodin D (BD) and Bulbocodin C (BC), two bibenzyls derived from Pleione bulbocodioides (Franch.) Rolfe, have demonstrated notable in vitro anticancer activity. In human lung cancer A549 cells, the IC50s for BD and BC were 11.63 and 11.71 μmol·L-1, respectively. BD triggered apoptosis, as evidenced by an upsurge in Annexin V-positive cells and elevated protein expression of cleaved-PARP in cancer cells. Furthermore, BD and BC markedly inhibited the migratory and invasive potentials of A549 cells. The altered genes identified through RNA-sequencing analysis were integrated into the CMap dataset, suggesting BD's role as a potential signal transducer and activator of transcription 3 (STAT3) inhibitor. SwissDock and MOE analyses further revealed that both BD and BC exhibited a commendable binding affinity with STAT3. Additionally, a surface plasmon resonance assay confirmed the direct binding affinity between these compounds and STAT3. Notably, treatment with either BD or BC led to a significant reduction in p-STAT3 (Tyr 705) protein levels, regardless of interleukin-6 stimulation in A549 cells. In addition, the extracellular signal-regulated kinase (ERK) was activated after BD or BC treatment. An enhancement in cancer cell mortality was observed upon combined treatment of BD and U0126, the MEK1/2 inhibitor. In conclusion, BD and BC emerge as promising novel STAT3 inhibitors with potential implications in cancer therapy.

Recent advances in targeted strategies for triple-negative breast cancer

Triple-negative breast cancer (TNBC), a highly aggressive subtype of breast cancer, negatively expresses estrogen receptor, progesterone receptor, and the human epidermal growth factor receptor 2 (HER2). Although chemotherapy is the main form of treatment for patients with TNBC, the effectiveness of chemotherapy for TNBC is still limited. The search for more effective therapies is urgent. Multiple targeted therapeutic strategies have emerged according to the specific molecules and signaling pathways expressed in TNBC. These include PI3K/AKT/mTOR inhibitors, epidermal growth factor receptor inhibitors, Notch inhibitors, poly ADP-ribose polymerase inhibitors, and antibody-drug conjugates. Moreover, immune checkpoint inhibitors, for example, pembrolizumab, atezolizumab, and durvalumab, are widely explored in the clinic. We summarize recent advances in targeted therapy and immunotherapy in TNBC, with the aim of serving as a reference for the development of individualized treatment of patients with TNBC in the future.

A Novel Ageladine A Derivative Acts as a STAT3 Inhibitor and Exhibits Potential Antitumor Effects

The Janus kinase/signal transducer and activator of the transcription 3 (JAK/STAT3) signaling pathway controls multiple biological processes, including cell survival, proliferation, and differentiation. Abnormally activated STAT3 signaling promotes tumor cell growth, proliferation, and survival, as well as tumor invasion, angiogenesis, and immunosuppression. Hence, JAK/STAT3 signaling has been considered a promising target for antitumor therapy. In this study, a number of ageladine A derivative compounds were synthesized. The most effective of these was found to be compound 25. Our results indicated that compound 25 had the greatest inhibitory effect on the STAT3 luciferase gene reporter. Molecular docking results showed that compound 25 could dock into the STAT3 SH2 structural domain. Western blot assays demonstrated that compound 25 selectively inhibited the phosphorylation of STAT3 on the Tyr705 residue, thereby reducing STAT3 downstream gene expression without affecting the expression of the upstream proteins, p-STAT1 and p-STAT5. Compound 25 also suppressed the proliferation and migration of A549 and DU145 cells. Finally, in vivo research revealed that 10 mg/kg of compound 25 effectively inhibited the growth of A549 xenograft tumors with persistent STAT3 activation without causing significant weight loss. These results clearly indicate that compound 25 could be a potential antitumor agent by inhibiting STAT3 activation.

Identification of marine natural product Pretrichodermamide B as a STAT3 inhibitor for efficient anticancer therapy

The Janus kinase (JAK)/signal transducer and activator of transcription 3 (STAT3) regulates the expression of various critical mediators of cancer and is considered as one of the central communication nodes in cell growth and survival. Marine natural products (MNP) represent great resources for discovery of bioactive lead compounds, especially anti-cancer agents. Through the medium-throughput screening of our in-house MNP library, Pretrichodermamide B, an epidithiodiketopiperazine, was identified as a JAK/STAT3 signaling inhibitor. Further studies identified that Pretrichodermamide B directly binds to STAT3, preventing phosphorylation and thus inhibiting JAK/STAT3 signaling. Moreover, it suppressed cancer cell growth, in vitro, at low micromolar concentrations and demonstrated efficacy in vivo by decreasing tumor growth in a xenograft mouse model. In addition, it was shown that Pretrichodermamide B was able to induce cell cycle arrest and promote cell apoptosis. This study demonstrated that Pretrichodermamide B is a novel STAT3 inhibitor, which should be considered for further exploration as a promising anti-cancer therapy.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-022-00162-x.

In Silico and In Vitro Study of Janus Kinases Inhibitors from Naphthoquinones

Janus kinases (JAKs) are involved in numerous cellular signaling processes related to immune cell functions. JAK2 and JAK3 are associated with the pathogenesis of leukemia and common lymphoid-derived illnesses. JAK2/3 inhibitors could reduce the risk of various diseases by targeting this pathway. Herein, the naphthoquinones were experimentally and theoretically investigated to identify novel JAK2/3 inhibitors. Napabucasin and 2'-methyl napabucasin exhibited potent cell growth inhibition in TF1 (IC₅₀ = 9.57 and 18.10 μM) and HEL (IC₅₀ = 3.31 and 6.65 μM) erythroleukemia cell lines, and they significantly inhibited JAK2/3 kinase activity (in a nanomolar range) better than the known JAK inhibitor, tofacitinib. Flow cytometric analysis revealed that these two compounds induced apoptosis in TF1 cells in a time and dose-dependent manner. From the molecular dynamics study, both compounds formed hydrogen bonds with Y931 and L932 residues and hydrophobically contacted with the conserved hinge region, G loop, and catalytic loop of the JAK2. Our obtained results suggested that napabucasin and its methylated analog were potential candidates for further development of novel anticancer drug targeting JAKs.

Nanomaterial-assisted CRISPR gene-engineering - A hallmark for triple-negative breast cancer therapeutics advancement

Triple-negative breast cancer (TNBC) is the most violent class of tumor and accounts for 20-24% of total breast carcinoma, in which frequently rare mutation occurs in high frequency. The poor prognosis, recurrence, and metastasis in the brain, heart, liver and lungs decline the lifespan of patients by about 21 months, emphasizing the need for advanced treatment. Recently, the adaptive immunity mechanism of archaea and bacteria, called clustered regularly interspaced short palindromic repeats (CRISPR) combined with nanotechnology, has been utilized as a potent gene manipulating tool with an extensive clinical application in cancer genomics due to its easeful usage and cost-effectiveness. However, CRISPR/Cas are arguably the efficient technology that can be made efficient via organic material-assisted approaches. Despite the efficacy of the CRISPR/Cas@nano complex, problems regarding successful delivery, biodegradability, and toxicity remain to render its medical implications. Therefore, this review is different in focus from past reviews by (i) detailing all possible genetic mechanisms of TNBC occurrence; (ii) available treatments and gene therapies for TNBC; (iii) overview of the delivery system and utilization of CRISPR-nano complex in TNBC, and (iv) recent advances and related toxicity of CRISPR-nano complex towards clinical trials for TNBC.

Boronic Acid: A Novel Pharmacophore Targeting Src Homology 2 (SH2) Domain of STAT3

SH2 domains have been recognized as promising targets for various human diseases. However, targeting SH2 domains with phosphopeptides or small-molecule inhibitors derived from bioisosteres of the phosphate group is still challenging. Identifying novel bioisosteres of the phosphate group to achieve favorable in vivo potency is urgently needed. Here, we report the feasibility of targeting the STAT3-SH2 domain with a boronic acid group and the identification of a highly potent inhibitor compound 7 by replacing the carboxylic acid of compound 4 with a boronic acid. Compound 7 shows higher binding affinity, better cellular potency, more favorable PK profiles, and higher in vivo antitumor activity than 4. The stronger anticancer effect of 7 partially stems from its covalent binding mode with the SH2 domain, verified by the washout experiments. The relatively high level of sequence conservation among SH2 domains makes the results presented here of general significance.

Role of Nrf2, STAT3, and Src as Molecular Targets for Cancer Chemoprevention

Cancer is a complex and multistage disease that affects various intracellular pathways, leading to rapid cell proliferation, angiogenesis, cell motility, and migration, supported by antiapoptotic mechanisms. Chemoprevention is a new strategy to counteract cancer; to either prevent its incidence or suppress its progression. In this strategy, chemopreventive agents target molecules involved in multiple pathways of cancer initiation and progression. Nrf2, STAT3, and Src are promising molecular candidates that could be targeted for chemoprevention. Nrf2 is involved in the expression of antioxidant and phase II metabolizing enzymes, which have direct antiproliferative action as well as indirect activities of reducing oxidative stress and eliminating carcinogens. Similarly, its cross-talk with NF-κB has great anti-inflammatory potential, which can be utilized in inflammation-induced/associated cancers. STAT3, on the other hand, is involved in multiple pathways of cancer initiation and progression. Activation, phosphorylation, dimerization, and nuclear translocation are associated with tumor cell proliferation and angiogenesis. Src, being the first oncogene to be discovered, is important due to its convergence with many upstream stimuli, its cross-talk with other potential molecular targets, such as STAT3, and its ability to modify the cell cytoskeleton, making it important in cancer invasion and metastasis. Therefore, the development of natural/synthetic molecules and/or design of a regimen that can reduce oxidative stress and inflammation in the tumor microenvironment and stop multiple cellular targets in cancer to stop its initiation or retard its progression can form newer chemopreventive agents.