Reprogramming of TAMs via the STAT3/CD47-SIRPα axis promotes acquired resistance to EGFR-TKIs in lung cancer.

Cross-talk between the tumor microenvironment (TME) and cancer cells plays an important role in acquired drug resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs). The role of tumor-associated macrophages (TAMs), the major component of the TME, in acquired resistance remains unclear. In this study, M2-like reprogramming of TAMs and reduced phagocytosis by macrophages were observed in gefitinib-resistant lung cancer cells and tumor xenografts. CD47 was upregulated in TKI-resistant lung cancer cells, and M2 macrophage polarization and cancer cell escape from macrophage phagocytosis were enhanced. Culture medium from TKI-resistant cells led to metabolic reprogramming of TAMs. STAT3 was associated with CD47 expression in TKI-resistant lung cancer cells. Genetic and pharmacological inhibition of STAT3 enhanced the phagocytic activity of TAMs and alleviated the acquired resistance to EGFR-TKIs via inhibiting the CD47-SIRPα signaling axis and M2 polarization in the co-culture system. Moreover, STAT3 transcriptionally regulated CD47 expression by binding to consensus DNA response elements in the intron of the CD47 gene. Furthermore, the combination of gefitinib with a STAT3 inhibitor and an anti-CD47 monoclonal antibody alleviated the acquired resistance to gefitinib in vitro and in vivo. Collectively, our study reveals the role of TAM reprogramming and the CD47-SIRPα axis in acquired EGFR-TKI resistance and provides a novel therapeutic strategy to overcome the acquired resistance to EGFR-TKIs in lung cancer.

Metabolic Reprogramming Driven by IGF2BP3 Promotes Acquired Resistance to EGFR Inhibitors in Non-Small Cell Lung Cancer.

Acquired resistance represents a bottleneck for effective molecular targeted therapy in lung cancer. Metabolic adaptation is a distinct hallmark of human lung cancer that might contribute to acquired resistance. In this study, we discovered a novel mechanism of acquired resistance to EGFR tyrosine kinase inhibitors (TKI) mediated by IGF2BP3-dependent cross-talk between epigenetic modifications and metabolic reprogramming through the IGF2BP3-COX6B2 axis. IGF2BP3 was upregulated in patients with TKI-resistant non-small cell lung cancer, and high IGF2BP3 expression correlated with reduced overall survival. Upregulated expression of the RNA binding protein IGF2BP3 in lung cancer cells reduced sensitivity to TKI treatment and exacerbated the development of drug resistance via promoting oxidative phosphorylation (OXPHOS). COX6B2 mRNA bound IGF2BP3, and COX6B2 was required for increased OXPHOS and acquired EGFR-TKI resistance mediated by IGF2BP3. Mechanistically, IGF2BP3 bound to the 3'-untranslated region of COX6B2 in an m6A-dependent manner to increase COX6B2 mRNA stability. Moreover, the IGF2BP3-COX6B2 axis regulated nicotinamide metabolism, which can alter OXPHOS and promote EGFR-TKI acquired resistance. Inhibition of OXPHOS with IACS-010759, a small-molecule inhibitor, resulted in strong growth suppression in vitro and in vivo in a gefitinib-resistant patient-derived xenograft model. Collectively, these findings suggest that metabolic reprogramming by the IGF2BP3-COX6B2 axis plays a critical role in TKI resistance and confers a targetable metabolic vulnerability to overcome acquired resistance to EGFR-TKIs in lung cancer. SIGNIFICANCE: IGF2BP3 stabilizes COX6B2 to increase oxidative phosphorylation and to drive resistance to EGFR inhibitors in lung cancer, which provides a therapeutic strategy to overcome acquired resistance by targeting metabolic transitions.

Targeting STAT3-VISTA axis to suppress tumor aggression and burden in acute myeloid leukemia.

The acute myeloid leukemia (AML) patients obtain limited benefits from current immune checkpoint blockades (ICBs), although immunotherapy have achieved encouraging success in numerous cancers. Here, we found that V-domain Ig suppressor of T cell activation (VISTA), a novel immune checkpoint, is highly expressed in primary AML cells and associated with poor prognosis of AML patients. Targeting VISTA by anti-VISTA mAb boosts T cell-mediated cytotoxicity to AML cells. Interestingly, high expression of VISTA is positively associated with hyperactive STAT3 in AML. Further evidence showed that STAT3 functions as a transcriptional regulator to modulate VISTA expression by directly binding to DNA response element of VISTA gene. We further develop a potent and selective STAT3 inhibitor W1046, which significantly suppresses AML proliferation and survival. W1046 remarkably enhances the efficacy of VISTA mAb by activating T cells via inhibition of STAT3 signaling and down-regulation of VISTA. Moreover, combination of W1046 and VISTA mAb achieves a significant anti-AML effect in vitro and in vivo. Overall, our findings confirm that VISTA is a potential target for AML therapy which transcriptionally regulated by STAT3 and provide a promising therapeutic strategy for immunotherapy of AML.

Structural optimization of Imidazo[1, 2-a]pyridine derivatives for the treatment of gastric cancer via STAT3 signaling pathway.

STAT3 is a promising therapeutic target for the treatment of gastric cancer, which is one of the most common solid tumors worldwide. In the previous works, we discovered a series of novel STAT3 inhibitors bearing an imidazo[1,2-a] pyridine scaffold. In order to improve the metabolic stability of these compounds, herein we performed a systematic structural optimization leading to a bioactive inhibitor 42, which demonstrated significant effects on inhibiting the growth, migration and invasion of human gastric cancer cells lines (AGS and MGC-803). Meanwhile, it was able to block the phosphorylation and dimerization of STAT3 at low micromolar concentration. Furthermore, compound 42 obviously suppressed tumor growth in MGC-803 derived xenograft mouse model, suggesting that it deserves further exploration as a promising anti-cancer agent for advanced gastric cancer.

Connexin 37 Regulates the Kv1.3 Pathway and Promotes the Development of Atherosclerosis.

Objective: To investigate the mechanism of Connexin 37 (Cx37) and Kv1.3 pathways in atherosclerosis (AS). Methods: ApoE-/- mice were given a high-fat diet to establish atherosclerosis (AS) model, and macrophages in mice were isolated and extracted to transfect Cx37 vectors with silencing or overexpressing, and Kv1.3 pathway blockers were used to inhibit the pathway activity. The indexes of body weight, blood glucose, and blood lipid of mice were collected. The protein and mRNA expression levels of Cx37 and Kv1.3 were detected by reverse transcription-PCR (RT-PCR), Western blot, and immunofluorescence technique. Oil red O staining was used to observe plaque area. Masson staining was used to detect collagen content. The concentrations of chemokine CCL7 were quantified using the ELISA kits. CCK8 was used to detect cell proliferation. Results: Cx37 and Kv1.3 were highly expressed in macrophages of AS mice, and the expression of Kv1.3 and CCL7 decreased after Cx37 was silenced, and the proliferation of macrophages was also decreased. Wild-type mice and AS model mice were treated with Cx37 overexpression vectors and Kv1.3 pathway blocking, and it was found that Cx37 overexpression could improve the blood lipid and blood glucose levels and increase the area of AS in AS mice. However, blocking the activity of Kv1.3 pathway can reduce the levels of blood lipid and blood glucose, increase the body weight of mice, and reduce the area of AS mice. Blocking the activity of Kv1.3 pathway can slow down the plaque development of AS mice and make its indexes close to wild-type mice. And the use of Kv1.3 pathway blockers on the basis of overexpression of Cx37 indicated that inhibition of Kv1.3 pathway activity did not affect the expression of Cx37, but could inhibit the collagen content in the plaque area of AS mice, inhibit the expression of chemokine CCL7, and reverse the effect of Cx37 overexpression. Conclusion: Cx37 can improve the activity of macrophages by regulating the expression of chemokines and the activity of Kv1.3 pathway in AS mice, and enrich macrophages in inflammatory tissues and expand the area of plaque formation.

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.

Discovery of small molecule Gαq/11 protein inhibitors against uveal melanoma.

Constitutively activated G proteins caused by specific mutations mediate the development of multiple malignancies. The mutated Gαq/11 are perceived as oncogenic drivers in the vast majority of uveal melanoma (UM) cases, making directly targeting Gαq/11 to be a promising strategy for combating UM. Herein, we report the optimization of imidazopiperazine derivatives as Gαq/11 inhibitors, and identified GQ262 with improved Gαq/11 inhibitory activity and drug-like properties. GQ262 efficiently blocked UM cell proliferation and migration in vitro. Analysis of the apoptosis-related proteins, extracellular signal-regulated kinase (ERK), and yes-associated protein (YAP) demonstrated that GQ262 distinctly induced UM cells apoptosis and disrupted the downstream effectors by targeting Gαq/11 directly. Significantly, GQ262 showed outstanding antitumor efficacy in vivo with good safety at the testing dose. Collectively, our findings along with the favorable pharmacokinetics of GQ262 revealed that directly targeting Gαq/11 may be an efficient strategy against uveal melanoma.

The Double-Edged Sword of SIRT3 in Cancer and Its Therapeutic Applications.

Reprogramming of cellular energy metabolism is considered an emerging feature of cancer. Mitochondrial metabolism plays a crucial role in cancer cell proliferation, survival, and metastasis. As a major mitochondrial NAD+-dependent deacetylase, sirtuin3 (SIRT3) deacetylates and regulates the enzymes involved in regulating mitochondrial energy metabolism, including fatty acid oxidation, the Krebs cycle, and the respiratory chain to maintain metabolic homeostasis. In this article, we review the multiple roles of SIRT3 in various cancers, and systematically summarize the recent advances in the discovery of its activators and inhibitors. The roles of SIRT3 vary in different cancers and have cell- and tumor-type specificity. SIRT3 plays a unique function by mediating interactions between mitochondria and intracellular signaling. The critical functions of SIRT3 have renewed interest in the development of small molecule modulators that regulate its activity. Delineation of the underlying mechanism of SIRT3 as a critical regulator of cell metabolism and further characterization of the mitochondrial substrates of SIRT3 will deepen our understanding of the role of SIRT3 in tumorigenesis and progression and may provide novel therapeutic strategies for cancer targeting SIRT3.

Inhibition of STAT3-ferroptosis negative regulatory axis suppresses tumor growth and alleviates chemoresistance in gastric cancer.

Chemotherapy is still one of the principal treatments for gastric cancer, but the clinical application of 5-FU is limited by drug resistance. Here, we demonstrate that ferroptosis triggered by STAT3 inhibition may provide a novel opportunity to explore a new effective therapeutic strategy for gastric cancer and chemotherapy resistance. We find that ferroptosis negative regulation (FNR) signatures are closely correlated with the progression and chemoresistance of gastric cancer. FNR associated genes (GPX4, SLC7A11, and FTH1) and STAT3 are upregulated in 5-FU resistant cells and xenografts. Further evidence demonstrates that STAT3 binds to consensus DNA response elements in the promoters of the FNR associated genes (GPX4, SLC7A11, and FTH1) and regulates their expression, thereby establishing a negative STAT3-ferroptosis regulatory axis in gastric cancer. Genetic inhibition of STAT3 activity triggers ferroptosis through lipid peroxidation and Fe2+ accumulation in gastric cancer cells. We further develop a potent and selective STAT3 inhibitor, W1131, which demonstrates significant anti-tumor effects in gastric cancer cell xenograft model, organoids model, and patient-derived xenografts (PDX) model partly by inducing ferroptosis, thus providing a new candidate compound for advanced gastric cancer. Moreover, targeting the STAT3-ferroptosis circuit promotes ferroptosis and restores sensitivity to chemotherapy. Our finding reveals that STAT3 acts as a key negative regulator of ferroptosis in gastric cancer through a multi-pronged mechanism and provides a new therapeutic strategy for advanced gastric cancer and chemotherapy resistance.

Amphiphilic small molecular mates match hydrophobic drugs to form nanoassemblies based on drug-mate strategy.

Nanomedicine has made great progress in the targeted therapy of cancer. Here, we established a novel drug-mate strategy by studying the formulation of nanodrugs at the molecular level. In the drug-mate combination, the drug is a hydrophobic drug that is poorly soluble in water, and the mate is an amphiphilic small molecule (SMA) that has both hydrophilic and lipophilic properties. We proposed that the hydrophobic drug could co-assemble with a suitable SMA on a nanoscale without additive agents. The proof-of-concept methodology and results were presented to support our hypothesis. We selected five hydrophobic drugs and more than ten amphiphilic small molecules to construct a library. Through molecular dynamic simulation and quantum chemistry computation, we speculated that the formation of nanoassemblies was related to the binding energy of the drug-mate, and the drug-mate interaction must overcome drug-drug interaction. Furthermore, the obtained SF/VECOONa nanoassemblieswas selected as a model, which had an ultra-high drug loading content (46%), improved pharmacokinetics, increased bioavailability, and enhanced therapeutic efficacy. In summary, the drug-mate strategy is an essential resource to design exact SMA for many hydrophobic drugs and provides a reference for the design of a carrier-free drug delivery system.

Structure-based discovery of potent and selective small-molecule inhibitors targeting signal transducer and activator of transcription 3 (STAT3).

STAT3 has been validated as an attractive anticancer target due to its important roles in cancer initiation and progression. However, discovery of potent and selective STAT3 small-molecule inhibitors with druglike properties is still challenging. In this study, two series of substituted 2-phenylquinolines and 2-arylimidazo[1,2-a]pyridines were designed through structure-based drug discovery approach by condensing the privileged structures of STX-119 and SH4-54. Our study has resulted in the discovery of a number of highly potent and selective STAT3 inhibitors, exemplified by compound 39 with the privileged structure of 2-phenylimidazo[1,2-a]pyridine, which selectively inhibits phosphorylation of STAT3 and suppresses subsequent signaling pathway. Moreover, 39 inhibits cell growth, migration and invasion of human triple negative breast cancer (TNBC) cells lines. Consistently, it achieves significant and dose-dependent tumor growth inhibition in both cell line-derived and patient-derived xenograft tumor models in mice. These results clearly indicate that 39 is a highly potent and selective STAT3 inhibitor.

A novel STAT3 inhibitor W2014-S regresses human non-small cell lung cancer xenografts and sensitizes EGFR-TKI acquired resistance.

Constitutive activation of signal transducer and activator of transcription 3 (STAT3) is a common feature in human non-small cell lung cancer (NSCLC). STAT3 plays an important role in cancer progression as a driver oncogene and acquired resistance of targeted therapies as an alternatively activated pathway. W2014-S with pharmacophore structure of imidazopyridine, which was firstly reported to be utilized in STAT3 inhibitor discovery, was screened out as a potent STAT3 inhibitor from a library of small molecules. The aim of this study is to investigate the antitumor activities and mechanisms of W2014-S in NSCLC and effect on epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) resistance in vitro and in vivo. Methods: SPR analysis, Co-immunoprecipitation, confocal microscope imaging, and luciferase report gene assays were utilized to determine the mechanisms. Cell viability, colonial survival, wound healing, cell invasion assay, human cancer cell xenografts and PDX tumor xenografts were used to determine antitumor activities. Results: W2014-S disrupted STAT3 dimerization and selectively inhibited aberrant STAT3 signaling in NSCLC cell line. W2014-S strongly suppressed proliferation, survival, migration and invasion of lung cancer cells with aberrant STAT3 activation and inhibited the growth of human NSCLC cell xenografts and PDX tumor xenografts in mouse model. Furthermore, W2014-S significantly sensitized resistant NSCLC cell line to gefitinib and erlotinib in vitro and enhances the anti-tumor effect of gefitinib in TKI-resistant lung cancer xenografts in vivo. Conclusions: Our study has provided a novel STAT3 inhibitor with significant anti-tumor activities in NSCLC and suggests that combination of STAT3 inhibitor such as W2014-S with gefitinib could serve as a promising strategy to overcome EGFR-TKIs acquired resistance in NSCLC patients.