Activation of Stat3 by receptor tyrosine kinases and cytokines regulates survival in human non-small cell carcinoma cells

IL-22: A key inflammatory mediator as a biomarker and potential therapeutic target for lung cancer

Lung cancer, one of the most prevalent cancers worldwide, stands as the primary cause of cancer-related deaths. As is well-known, the utmost crucial risk factor contributing to lung cancer is smoking. In recent years, remarkable progress has been made in treating lung cancer, particularly non-small cell lung cancer (NSCLC). Nevertheless, the absence of effective and accurate biomarkers for diagnosing and treating lung cancer remains a pressing issue. Interleukin 22 (IL-22) is a member of the IL-10 cytokine family. It exerts biological functions (including induction of proliferation and anti-apoptotic signaling pathways, enhancement of tissue regeneration and immunity defense) by binding to heterodimeric receptors containing type 1 receptor chain (R1) and type 2 receptor chain (R2). IL-22 has been identified as a pro-cancer factor since dysregulation of the IL-22-IL-22R system has been implicated in the development of different cancers, including lung, breast, gastric, pancreatic, and colon cancers. In this review, we discuss the differential expression, regulatory role, and potential clinical significance of IL-22 in lung cancer, while shedding light on innovative approaches for the future.

p27 specifically decreases in squamous carcinoma, and mediates NNK-induced transformation of human bronchial epithelial cells

Lung cancer remains the leading cause of cancer-related deaths, with cigarette smoking being the most critical factor, linked to nearly 90% of lung cancer cases. NNK, a highly carcinogenic nitrosamine found in tobacco, is implicated in the lung cancer-causing effects of cigarette smoke. Although NNK is known to mutate or activate certain oncogenes, its potential interaction with p27 in modulating these carcinogenic effects is currently unexplored. Recent studies have identified specific downregulation of p27 in human squamous cell carcinoma, in contrast to adenocarcinoma. Additionally, exposure to NNK significantly suppresses p27 expression in human bronchial epithelial cells. Subsequent studies indicates that the downregulation of p27 is pivotal in NNK-induced cell transformation. Mechanistic investigations have shown that reduced p27 expression leads to increased level of ITCH, which facilitates the degradation of Jun B protein. This degradation in turn, augments miR-494 expression and its direct regulation of JAK1 mRNA stability and protein expression, ultimately activating STAT3 and driving cell transformation. In summary, our findings reveal that: (1) the downregulation of p27 increases Jun B expression by upregulating Jun B E3 ligase ITCH, which then boosts miR-494 transcription; (2) Elevated miR-494 directly binds to 3'-UTR of JAK1 mRNA, enhancing its stability and protein expression; and (3) The JAK1/STAT3 pathway is a downstream effector of p27, mediating the oncogenic effect of NNK in lung cancer. These findings provide significant insight into understanding the participation of mechanisms underlying p27 inhibition of NNK induced lung squamous cell carcinogenic effect.

Associations Between Sex-Specific Reproductive Factors and Risk of New-Onset Lung Cancer Among Female Patients

BACKGROUND

Several characteristics distinguish lung cancer in female patients from that in male patients, with adenocarcinoma being more prevalent in female patients and occurring more frequently in female patients who do not smoke. Uncertainty surrounds the relationship between female-specific reproductive factors and lung cancer risk.

RESEARCH QUESTION

Are sex-specific reproductive factors associated with risk of lung cancer in different genetic risk groups and histologic types?

STUDY DESIGN AND METHODS

A Cox proportional hazard model was used to evaluate the association between multiple reproductive factors and the risk of lung cancer developing in a prospective cohort study involving 273,190 female individuals from the UK Biobank. Subgroup analyses stratified by age, smoking status, BMI, genetic risk, and histologic subtype were conducted to emphasize the modification effects further.

RESULTS

A total of 1,182 cases of lung cancer in female patients were recorded over a median follow-up period of 12.0 years in the cohort study. In multivariable-adjusted models, early menarche (age ≤ 11 years: hazard ratio [HR], 1.22; 95% CI, 1.03-1.46), early menopause (age ≤ 46 years: HR, 1.49; 95% CI, 1.19-1.86), a shorter reproductive span (≤ 32 years: HR, 1.42; 95% CI, 1.18-1.71; and 33-35 years: HR, 1.24; 95% CI, 1.00-1.53), and early age at first birth (age ≤ 20 years: HR, 1.63; 95% CI, 1.33-2.01) were associated with a higher risk of lung cancer. Stratified analysis revealed that several reproductive factors, including early age at menopause, shortened reproductive span, and early age at first birth, showed a substantially stronger relationship with an elevated risk of lung cancer, particularly of lung adenocarcinoma, in populations with high genetic risk and more detrimental behaviors.

INTERPRETATION

Early age at menopause, a shortened reproductive life span, and early age at first birth were associated with higher risks of lung cancer, particularly of lung adenocarcinoma, in a subpopulation with higher genetic susceptibility and detrimental behaviors. The evidence provided by this study emphasizes the significance of screening for multiple reproductive factors to prevent lung cancer among female individuals.

Synthesis and evaluation of [18F]FBNAF, a STAT3-targeting probe, for PET imaging of tumor microenvironment

BACKGROUND

Signal transducer and activator of transcription 3 (STAT3) is a protein that regulates cell proliferation and differentiation, and it is attracting attention as a new index for evaluating cancer pathophysiology, as its activation has been highly correlated with the development and growth of tumors. With the development of STAT3 inhibitors, the demand for imaging probes will intensify. Noninvasive STAT3 imaging can help determine the cancer status and predict the efficacy of STAT3 inhibitors. In this study, we aimed to develop an imaging probe targeting STAT3 and synthesized [18F]FBNAF, which was derived from a STAT3-selective inhibitor as the lead compound, followed by in vitro and in vivo evaluations of [18F]FBNAF in positron emission tomography for STAT3.

RESULTS

The results revealed that FBNAF concentration-dependently inhibited STAT3 phosphorylation, similar to the lead compound, thereby supporting radiosynthesis. [18F]FBNAF was easily synthesized from the pinacol boronate ester precursor with suitable radiochemical conversion (46%), radiochemical yield (6.0%), and radiochemical purity (> 97%). [18F]FBNAF exhibited high stability in vitro and in vivo, and radioactivity accumulated in tumor tissues expressing STAT3 with an increasing tumor/blood ratio over time, peaking at 2.6 ± 0.8 at 120 min after injection in tumor-bearing mice. Tumor radioactivity was significantly reduced by the coinjection of a STAT3-selective inhibitor. Furthermore, the localization of radioactivity was almost consistent with STAT3 expression based on ex vivo autoradiography and immunohistochemistry using adjacent tumor sections.

CONCLUSIONS

Thus, [18F]FBNAF could be the first promising STAT3-targeting probe for PET imaging. A STAT3 imaging probe provides meaningful information on STAT3-associated cancer conditions and in tumor microenvironment.

5-Methoxytryptophan enhances the sensitivity of sorafenib on the inhibition of proliferation and metastasis for lung cancer cells

BACKGROUND

Lung cancer is a leading cause of cancer-related mortality worldwide, and effective therapies are limited. Lung cancer is a leading cause of cancer-related mortality worldwide with limited effective therapy. Sorafenib is a multi-tyrosine kinase inhibitor frequently used to treat numerous types of malignant tumors. However, it has been demonstrated that sorafenib showed moderate antitumor activity and is associated with several side effects in lung cancer, which restricted its clinical application. This study aimed to examine the antitumor effect of the combination treatment of sorafenib and 5-methoxytryptophan (5-MTP) on cell growth and metastasis of Lewis lung carcinoma (LLC) cells.

METHOD

The anticancer effect of the combination treatment of sorafenib and 5-MTP was determined through cytotoxicity assay and colony forming assays. The mechanism was elucidated using flow cytometry and western blotting. Wound healing and Transwell assays were conducted to evaluate the impact of the combination treatment on migration and invasion abilities. An in vivo model was employed to analyze the effect of the combination treatment on the tumorigenic ability of LLC cells.

RESULT

Our results demonstrated that the sorafenib and 5-MTP combination synergistically reduced viability and proliferation compared to sorafenib or 5-MTP treatment alone. Reduction of cyclin D1 expression was observed in the sorafenib alone or combination treatments, leading to cell cycle arrest. Furthermore, the sorafenib-5-MTP combination significantly increased the inhibitory effect on migration and invasion of LLC cells compared to the single treatments. The combination also significantly downregulated vimentin and MMP9 levels, contributing to the inhibition of metastasis. The reduction of phosphorylated Akt and STAT3 expression may further contribute to the inhibitory effect on proliferation and metastasis. In vivo, the sorafenib-5-MTP combination further reduced tumor growth and metastasis compared to the treatment of sorafenib alone.

CONCLUSIONS

In conclusion, our data indicate that 5-MTP sensitizes the antitumor activity of sorafenib in LLC cells in vitro and in vivo, suggesting that sorafenib-5-MTP has the potential to serve as a therapeutic option for patients with lung cancer.

Interplay between signal transducers and activators of transcription (STAT) proteins and cancer: involvement, therapeutic and prognostic perspective

Signal transducers and activators of transcription or STAT are proteins that consist of various transcription factors that are responsible for activating genes regarding cell proliferation, differentiation, and apoptosis. They commonly activate several cytokine, growth, or hormone factors via the JAK-STAT signaling pathway by tyrosine phosphorylation which are responsible for giving rise to numerous immune responses. Mutations within the Janus-Kinases (JAKs) or the STATs can set off the commencement of various malfunctions of the immune system of the body; carcinogenesis being an inevitable outcome. STATs are known to act as both oncogenes and tumor suppressor genes which makes it a hot topic of investigation. Various STATs related mechanisms are currently being investigated to analyze its potential of serving as a therapeutic base for numerous immune diseases and cancer; a deeper understanding of the molecular mechanisms involved in the signaling pathways can contribute to the same. This review will throw light upon each STAT member in causing cancer malignancies by affecting subsequent signaling pathways and its genetic and epigenetic associations as well as various inhibitors that could be used to target these pathways thereby devising new treatment options. The review will also focus upon the therapeutic advances made in cancers that most commonly affect people and discuss how STAT genes are identified as prognostic markers.

Integration analysis using bioinformatics and experimental validation on the clinical and biological significance of TSLP in cancers

Thymic stromal lymphopoietin (TSLP) has significantly impacted the development and progression of various neoplastic disorders. To comprehensively evaluate the diverse significance of TSLP in malignant tumors, we first integrative analyze the TSLP expression level in paired and unpaired pan-cancer tissue and cell line, compared against the normal tissue. The correlation between TSLP expression, molecular subtypes, immune subtypes, diagnostic value, and prognostic value in pan-cancer was also investigated. We then explored the impact of TSLP expression on multifaced immune cell infiltration and subsequent clinical outcomes in lung adenocarcinoma (LUAD) patients. and conducted cellular experiments to functionally examine the effect of TSLP on cell proliferation, apoptosis, cell cycle, migration, and invasion in LUAD. The anti-neoplastic mechanism of TSLP was further investigated by qRT-PCR and western blotting. Our findings reveal that TSLP expression is abnormally low in various cancers compared to normal tissue and is associated with different molecular and immune subtypes of cancers. Moreover, ROC and survival analysis results suggest that TSLP expression is correlated with the diagnostic, prognostic, clinical features, and immune cells of LUAD patients. Cell experiments showed that overexpression of TSLP elicited a significant reduction in LUAD cell viability, promoted cell apoptosis, impeded cell cycle progression in the G2/M phase, and inhibited cell migration and invasion. In addition, TSLP inhibited LUAD progression through the JAK1/STAT3 signaling pathway. Therefore, targeting TSLP shows potential as a therapeutic strategy for pan-cancer, particularly for LUAD, and as a biomarker for predicting the prognosis of this malignancy.

Effect of plant produced Anti-hIL-6 receptor antibody blockade on pSTAT3 expression in human peripheral blood mononuclear cells

As a response to invasion by pathogens, the secretion of interleukin 6 (IL-6) which is a cytokine, activates IL-6/JAKs/STAT3 intracellular signaling via., phosphorylation. Over expression of pSTAT3 induces IL-6 positive feedback loop causing cytokine release syndrome or cytokine storm. Plants have gained momentum as an alternative expression system. Hence, this study aims to produce mAb targeting human IL-6 receptor (hIL-6R) in Nicotiana benthamiana for down regulating its cellular signaling thus, decreasing the expression of pSTAT3. The variable regions of heavy and light chains of anti-hIL-6R mAb were constructed in pBYK2e geminiviral plant expression vector and transiently co-expressed in N. benthamiana. The results demonstrate the proper protein assembly of anti-hIL-6R mAb with highest expression level of 2.24 mg/g FW at 5 dpi, with a yield of 21.4 µg/g FW after purification. The purity and N-glycosylation of plant produced antibody was analyzed, including its specificity to human IL-6 receptor by ELISA. Additionally, we investigated the effect to pSTAT3 expression in human PBMC's by flow cytometry wherein, the results confirmed lower expression of pSTAT3 with increasing concentrations of plant produced anti-hIL-6R mAb. Although, further in vivo studies are key to unveil the absolute functionality of anti-hIL-6R, we hereby show the potential of the plant platform and its suitability for the production of this therapeutic antibody.

Structural and Biological Features of G-Quadruplex Aptamers as Promising Inhibitors of the STAT3 Signaling Pathway

In this paper, we investigate the structural and biological features of G-quadruplex (G4) aptamers as promising antiproliferative compounds affecting the STAT3 signalling pathway. Targeting the STAT3 protein through high-affinity ligands to reduce its levels or activity in cancer has noteworthy therapeutic potential. T40214 (STAT) [(G₃C)₄] is a G4 aptamer that can influence STAT3 biological outcomes in an efficient manner in several cancer cells. To explore the effects of an extra cytidine in second position and/or of single site-specific replacements of loop residues in generating aptamers that can affect the STAT3 biochemical pathway, a series of STAT and STATB [GCG₂(CG₃)₃C] analogues containing a thymidine residue instead of cytidines was prepared. NMR, CD, UV, and PAGE data suggested that all derivatives adopt dimeric G4 structures like that of unmodified T40214 endowed with higher thermal stability, keeping the resistance in biological environments substantially unchanged, as shown by the nuclease stability assay. The antiproliferative activity of these ODNs was tested on both human prostate (DU145) and breast (MDA-MB-231) cancer cells. All derivatives showed similar antiproliferative activities on both cell lines, revealing a marked inhibition of proliferation, particularly at 72 h at 30 µM. Transcriptomic analysis aimed to evaluate STAT's and STATB's influence on the expression of many genes in MDA-MB-231 cells, suggested their potential involvement in STAT3 pathway modulation, and thus their interference in different biological processes. These data provide new tools to affect an interesting biochemical pathway and to develop novel anticancer and anti-inflammatory drugs.

The FGF/FGFR signalling mediated anti-cancer drug resistance and therapeutic intervention

ABSTRACT Fibroblast Growth Factor (FGF) ligands and their receptors are crucial factors driving chemoresistance in several malignancies, challenging the efficacy of currently available anti-cancer drugs. The Fibroblast growth factor/receptor (FGF/FGFR) signalling malfunctions in tumor cells, resulting in a range of molecular pathways that may impact its drug effectiveness. Deregulation of cell signalling is critical since it can enhance tumor growth and metastasis. Overexpression and mutation of FGF/FGFR induce regulatory changes in the signalling pathways. Chromosomal translocation facilitating FGFR fusion production aggravates drug resistance. Apoptosis is inhibited by FGFR-activated signalling pathways, reducing multiple anti-cancer medications' destructive impacts. Angiogenesis and epithelial-mesenchymal transition (EMT) are facilitated by FGFRs-dependent signalling, which correlates with drug resistance and enhances metastasis. Further, lysosome-mediated drug sequestration is another prominent method of resistance. Inhibition of FGF/FGFR by following a plethora of therapeutic approaches such as covalent and multitarget inhibitors, ligand traps, monoclonal antibodies, recombinant FGFs, combination therapy, and targeting lysosomes and micro RNAs would be helpful. As a result, FGF/FGFR suppression treatment options are evolving nowadays. To increase positive impacts, the processes underpinning the FGF/FGFR axis' role in developing drug resistance need to be clarified, emphasizing the need for more studies to develop novel therapeutic options to address this significant problem. Communicated by Ramaswamy H. Sarma.

Nintedanib induces senolytic effect via STAT3 inhibition

Selective removal of senescent cells, or senolytic therapy, has been proposed to be a potent strategy for overcoming age-related diseases and even for reversing aging. We found that nintedanib, a tyrosine kinase inhibitor, selectively induced the death of primary human dermal fibroblasts undergoing RS. Similar to ABT263, a well-known senolytic agent, nintedanib triggered intrinsic apoptosis in senescent cells. Additionally, at the concentration producing the senolytic effect, nintedanib arrested the cell cycle of nonsenescent cells in the G1 phase without inducing cytotoxicity. Interestingly, the mechanism by which nintedanib activated caspase-9 in the intrinsic apoptotic pathway differed from that of ABT263 apoptosis induction; specifically, nintedanib did not decrease the levels of Bcl-2 family proteins in senescent cells. Moreover, nintedanib suppressed the activation of the JAK2/STAT3 pathway, which caused the drug-induced death of senescent cells. STAT3 knockdown in senescent cells induced caspase activation. Moreover, nintedanib reduced the number of senescence-associated β-galactosidase-positive senescent cells in parallel with a reduction in STAT3 phosphorylation and ameliorated collagen deposition in a mouse model of bleomycin-induced lung fibrosis. Consistently, nintedanib exhibited a senolytic effect through bleomycin-induced senescence of human pulmonary fibroblasts. Overall, we found that nintedanib can be used as a new senolytic agent and that inhibiting STAT3 may be an approach for inducing the selective death of senescent cells. Our findings pave the way for expanding the senolytic toolkit for use in various aging statuses and age-related diseases.

The Potential Tumor-Suppressor DHRS7 Inversely Correlates with EGFR Expression in Prostate Cancer Cells and Tumor Samples

Simple Summary

Prostate cancer is one of the most common malignancies in men. Current therapies are initially effective but resistance often develops, leading to tumor recurrence and death. Further research on new players, mechanisms involved in prostate cancer, and therapy resistance is needed. We studied the role of DHRS7, a potential tumor suppressor with currently unknown physiological function, in prostate cancer cells using proteome and gene expression analyses. Despite the fact that DHRS7 can inactivate 5α-dihydrotestosterone, its effect on prostate cancer cells seems to be unrelated to androgen metabolism. When comparing three widely studied prostate cancer cell lines, we observed a negative correlation between DHRS7 and EGFR expression. DHRS7 knockdown enhanced EGFR expression, while knockdown of EGFR tended to increase DHRS7 expression. Importantly, DHRS7 expression negatively correlates with EGFR expression and positively with survival rates in prostate cancer patients. This study suggests a tumor-suppressor role for DHRS7 by modulating EGFR expression in prostate cancer.

Abstract

Prostate cancer (PCa), one of the most common malignancies in men, typically responds to initial treatment, but resistance to therapy often leads to metastases and death. The dehydrogenase/reductase 7 (DHRS7, SDR34C1) is an “orphan” enzyme without known physiological function. DHRS7 was previously found to be decreased in higher-stage PCa, and siRNA-mediated knockdown increased the aggressiveness of LNCaP cells. To further explore the role of DHRS7 in PCa, we analyzed the proteome of LNCaP cells following DHRS7 knockdown to assess potentially altered pathways. Although DHRS7 is able to inactivate 5α-dihydrotestosterone, DHRS7 knockdown did not affect androgen receptor (AR) target gene expression, and its effect on PCa cells seems to be androgen-independent. Importantly, proteome analyses revealed increased expression of epidermal growth factor receptor (EGFR), which was confirmed by RT-qPCR and Western blotting. Comparison of AR-positive LNCaP with AR-negative PC-3 and DU145 PCa cell lines revealed a negative correlation between DHRS7 and EGFR expression. Conversely, EGFR knockdown enhanced DHRS7 expression in these cells. Importantly, analysis of patient samples revealed a negative correlation between DHRS7 and EGFR expression, both at the mRNA and protein levels, and DHRS7 expression correlated positively with patient survival rates. These results suggest a protective role for DHRS7 in PCa.

Nifuroxazide-loaded cubosomes exhibit an advancement in pulmonary delivery and attenuate bleomycin-induced lung fibrosis by regulating the STAT3 and NF-κB signaling: A new challenge for unmet therapeutic needs

Pulmonary fibrosis (PF) is a chronic progressive disease that portends a very poor prognosis. It has been suggested that STAT3 is a potential target in PF. This study highlights the importance of cubosomes as a drug delivery system in enhancing the bioavailability of nifuroxazide (NXZD), a poorly soluble STAT3 inhibitor. NXZD-loaded cubosomes (NXZD-LC) were in vitro and in vivo evaluated. In vitro, cubosomes presented a poly-angular nanosized particles with a mean size and zeta potential of 223.73 ± 4.73 nm and - 20.93 ± 2.38 mV, respectively. The entrapment efficiency of nifuroxazide was 90.56 ± 4.25%. The in vivo pharmacokinetic study and the lung tissue accumulation of NXZD were performed by liquid chromatography-tandem mass spectrometry after oral administration to rats. The nanoparticles exhibited a two-fold increase and 1.33 times of bioavailability and lung tissue concentration of NXZD compared to NXZD dispersion, respectively. In view of this, NXZD-LC effectively attenuated PF by targeting STAT3 and NF-κB signals. As a result, NXZD-LC showed a potential anti-inflammatory effect as revealed by the significant decrease in MCP-1, ICAM-1, IL-6, and TNF-α and suppressed fibrogenic mediators as indicated by the significant reduction in TGF-β, TIMP-1, and PDGF-BB in lung tissues. Besides, NXZD-LC improved antioxidant defense mechanisms and decreased LDH and BALF total protein. These effects contributed to decreased collagen deposition. To conclude, cubosomes represent an advantageous pharmaceutical delivery system for enhancing pulmonary delivery of poorly soluble drugs. Additionally, repurposing NXZD as an antifibrotic agent is a promising challenge and new therapeutic approach for unmet therapeutic needs.

MFN2-driven mitochondria-to-nucleus tethering allows a non-canonical nuclear entry pathway of the mitochondrial pyruvate dehydrogenase complex

The mitochondrial pyruvate dehydrogenase complex (PDC) translocates into the nucleus, facilitating histone acetylation by producing acetyl-CoA. We describe a noncanonical pathway for nuclear PDC (nPDC) import that does not involve nuclear pore complexes (NPCs). Mitochondria cluster around the nucleus in response to proliferative stimuli and tether onto the nuclear envelope (NE) via mitofusin-2 (MFN2)-enriched contact points. A decrease in nuclear MFN2 levels decreases mitochondria tethering and nPDC levels. Mitochondrial PDC crosses the NE and interacts with lamin A, forming a ring below the NE before crossing through the lamin layer into the nucleoplasm, in areas away from NPCs. Effective blockage of NPC trafficking does not decrease nPDC levels. The PDC-lamin interaction is maintained during cell division, when lamin depolymerizes and disassembles before reforming daughter nuclear envelopes, providing another pathway for nPDC entry during mitosis. Our work provides a different angle to understanding mitochondria-to-nucleus communication and nuclear metabolism.

A Redox-Silent Analogue of Tocotrienol May Break the Homeostasis of Proteasomes in Human Malignant Mesothelioma Cells by Inhibiting STAT3 and NRF1

6-O-Carboxypropyl-alpha-tocotrienol (α-T3E) is a multi-target redox-silent analogue of tocotrienol that exhibits cytotoxicity against many cancer cells, including malignant mesothelioma (MM) cells. α-T3E has several molecular targets to effectively induce cytotoxicity against MM cells; however, the mechanisms underlying this cytotoxicity remain unclear. In the present study, we demonstrated that the α-T3E-dependent disruption of the homeostasis of proteasomes strongly induced endoplasmic reticulum (ER) stress, which resulted in effective cytotoxicity against MM cells. The α-T3E-dependent disruption of the homeostasis of proteasomes depended on decreases in proteasome subunits via the inactivation of signal transducer and activator of transcription 3 (STAT3) and nuclear factor erythroid 2 related factor-1 (NRF1), which inhibited protease activity, such as chymotrypsin-like activity, in proteasomes. The α-T3E-dependent inhibition of this activity also induced severe ER stress and ultimately resulted in effective cytotoxicity against MM cells with chemoresistance. The present results indicate that α-T3E acts as an effective anti-mesothelioma agent by disrupting the homeostasis of proteasomes through the simultaneous inactivation of STAT3 and NRF1.

EEF2K silencing inhibits tumour progression through repressing SPP1 and synergises with BET inhibitors in melanoma

BACKGROUND

Despite the remarkable breakthroughs achieved in the management of metastatic melanoma using immunotherapy and targeted therapies, long-term clinical efficacy is often compromised due to dose-limiting toxicity and innate or acquired resistance. Therefore, it is of vital importance to further explore the molecular mechanisms underlying melanoma progression and identify new targeted therapeutic approaches.

METHODS

The function of eukaryotic elongation factor-2 kinase (EEF2K) in melanoma were investigated in vitro and in vivo. RNA-seq and chromatin immunoprecipitation (ChIP) assay were undertaken to explore the mechanisms. The antitumor effect of bromodomain and extra terminal domain (BET) inhibitors combined with cytarabine were assessed in melanoma both in vitro and in vivo.

RESULTS

EEF2K silencing markedly attenuated the malignant phenotypes of melanoma cells, including proliferation, migration, invasion and metastasis. In contrast, EEF2K overexpression promoted melanoma cell proliferation, migration and invasion. Mechanistically, we demonstrated that EEF2K upregulates the phosphorylation of STAT3 (p-STAT3) at Tyr705, which binds to the promoter region of SPP1 and enhances its transcription, thus facilitating melanoma progression. Transfection-induced re-expression of SPP1 partly negated the inhibitory effect of EEF2K silencing on melanoma, whereas inhibition of SPP1 or STAT3 significantly abolished the efficacy of EEF2K on melanoma cells. Intriguingly, EEF2K silencing combined with BET inhibitor treatment further inhibited cell proliferation and promoted apoptosis in melanoma. We further screened the US FDA-approved antitumour drug library and identified cytarabine as a potential clinically applicable EEF2K inhibitor that could synergise with BET inhibitors in melanoma treatment.

CONCLUSION

EEF2K/p-STAT3/SPP1 may be a novel oncogenic pathway in melanoma progression, which could be a target for novel combination therapy for melanoma.

Oncogenic dependency on STAT3 serine phosphorylation in KRAS mutant lung cancer

The oncogenic potential of the latent transcription factor signal transducer and activator of transcription (STAT)3 in many human cancers, including lung cancer, has been largely attributed to its nuclear activity as a tyrosine-phosphorylated (pY705 site) transcription factor. By contrast, an alternate mitochondrial pool of serine phosphorylated (pS727 site) STAT3 has been shown to promote tumourigenesis by regulating metabolic processes, although this has been reported in only a restricted number of mutant RAS-addicted neoplasms. Therefore, the involvement of STAT3 serine phosphorylation in the pathogenesis of most cancer types, including mutant KRAS lung adenocarcinoma (LAC), is unknown. Here, we demonstrate that LAC is suppressed in oncogenic KrasG12D-driven mouse models engineered for pS727-STAT3 deficiency. The proliferative potential of the transformed KrasG12D lung epithelium, and mutant KRAS human LAC cells, was significantly reduced upon pS727-STAT3 deficiency. Notably, we uncover the multifaceted capacity of constitutive pS727-STAT3 to metabolically reprogramme LAC cells towards a hyper-proliferative state by regulating nuclear and mitochondrial (mt) gene transcription, the latter via the mtDNA transcription factor, TFAM. Collectively, our findings reveal an obligate requirement for the transcriptional activity of pS727-STAT3 in mutant KRAS-driven LAC with potential to guide future therapeutic targeting approaches.

Butein and Frondoside-A Combination Exhibits Additive Anti-Cancer Effects on Tumor Cell Viability, Colony Growth, and Invasion and Synergism on Endothelial Cell Migration

Despite the significant advances in targeted- and immuno-therapies, lung and breast cancer are at the top list of cancer incidence and mortality worldwide as of 2020. Combination therapy consisting of a mixture of different drugs taken at once is currently the main approach in cancer management. Natural compounds are extensively investigated for their promising anti-cancer potential. This study explored the anti-cancer potential of butein, a biologically active flavonoid, on two major solid tumors, namely, A549 lung and MDA-MB-231 breast cancer cells alone and in combination with another natural anti-cancer compound, frondoside-A. We demonstrated that butein decreases A549 and MDA-MB-231 cancer cell viability and colony growth in vitro in addition to tumor growth on chick embryo chorioallantoic membrane (CAM) in vivo without inducing any noticeable toxicity. Additionally, non-toxic concentrations of butein significantly reduced the migration and invasion of both cell lines, suggesting its potential anti-metastatic effect. We showed that butein anti-cancer effects are due, at least in part, to a potent inhibition of STAT3 phosphorylation, leading to PARP cleavage and consequently cell death. Moreover, we demonstrated that combining butein with frondoside-A leads to additive effects on inhibiting A549 and MDA-MB-231 cellular viability, induction of caspase 3/7 activity, inhibition of colony growth, and inhibition of cellular migration and invasion. This combination reached a synergistic effect on the inhibition of HUVECs migration in vitro. Collectively, this study provides sufficient rationale to further carry out animal studies to confirm the relevance of these compounds’ combination in cancer therapy.

Multicellular Effects of STAT3 in Non-small Cell Lung Cancer: Mechanistic Insights and Therapeutic Opportunities

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer and accounts for 85% of lung cancer cases. Aberrant activation of the Signal Transducer and Activator of Transcription 3 (STAT3) is frequently observed in NSCLC and is associated with a poor prognosis. Pre-clinical studies have revealed an unequivocal role for tumor cell-intrinsic and extrinsic STAT3 signaling in NSCLC by promoting angiogenesis, cell survival, cancer cell stemness, drug resistance, and evasion of anti-tumor immunity. Several STAT3-targeting strategies have also been investigated in pre-clinical models, and include preventing upstream receptor/ligand interactions, promoting the degradation of STAT3 mRNA, and interfering with STAT3 DNA binding. In this review, we discuss the molecular and immunological mechanisms by which persistent STAT3 activation promotes NSCLC development, and the utility of STAT3 as a prognostic and predictive biomarker in NSCLC. We also provide a comprehensive update of STAT3-targeting therapies that are currently undergoing clinical evaluation, and discuss the challenges associated with these treatment modalities in human patients.

Delivery of gefitinib in synergism with thymoquinone via transferrin-conjugated nanoparticle sensitizes gefitinib-resistant non-small cell lung carcinoma to control metastasis and stemness

Epidermal growth factor receptor (EGFR) normally over-expresses in non-small cell lung cancer (NSCLC) cells. Its mutations act as oncogenic drivers in the cellular signal transduction pathway, and induce the downstream activation of numerous key cellular events involved in cellular proliferation and survival. EGFR tyrosine kinase inhibitors (EGFR-TK inhibitors), such as gefitinib and erlotinib, have been used for a long time in the treatment of NSCLC. However, they fail to overcome the EGFR-TK mutation due to the acquisition of drug resistance. It is strongly believed that the epithelial-to-mesenchymal transition (EMT) is a key player for acquired resistance and consequent limitation of the clinical efficiency of EGFR-TKIs. Therefore, a new strategy needs to be developed to overcome the resistance in NSCLC. In this current study, we have disclosed for the first time the efficiency of transferrin-modified PLGA-thymoquinone-nanoparticles in combination with gefitinib (NP-dual-1, NP-dual-2 and NP-dual-3) towards gefitinib-resistant A549 cells. The gefitinib-resistant A549 cells (A549/GR) showed 12.3-fold more resistance to gefitinib in comparison to non-resistant A549 cells. The phenotypic alteration resembling spindle-cell shape and increased pseudopodia integuments featured the EMT phenomena in A549/GR cells. EMT in A549/GR was later coupled with the loss of Ecad and expansion of Ncad, along with upregulated vimentin expression, as compared to the control A549 cells. Moreover, the invasive nature and migration potential are more amplified in A549/GR cells. Pre-incubation of A549 cells with TGFβ1 also initiated EMT, leading to drug resistance. Conversely, treatment of A549 or A549/GR cells with NP-dual-3 effectively retrieved the sensitivity to gefitinib, restricted the EMT phenomenon, and impaired the TGFβ1-induced EMT. On unveiling the underlying mechanism of therapeutic action, we found that STAT3 and miR-21 were individually overexpressed in the A549/GR cells by transfection, and followed by treatment with NP-dual-3. Simultaneously, NP-dual-3 fragmented HIF1-α induced EMT in A549/GR cells and reduced the CSCs markers, viz., Oct-4, Sox-2, Nanog, and Aldh1. These data are self-sufficient to suggest that NP-dual-3 re-sensitizes the drug-resistant A549/GR cells to gefitinib, possibly by retrieving MET phenomena via modulation of STAT3/mir-21/Akt/PTEN/HIF1-α axis. Thus, TQ nanoparticles combined with TKI gefitinib may provide an effective platform to treat NSCLC.

FGF/FGFR-Dependent Molecular Mechanisms Underlying Anti-Cancer Drug Resistance

Simple Summary

Deregulation of the FGF/FGFR axis is associated with many types of cancer and contributes to the development of chemoresistance, limiting the effectiveness of current treatment strategies. There are several mechanisms involved in this phenomenon, including cross-talks with other signaling pathways, avoidance of apoptosis, stimulation of angiogenesis, and initiation of EMT. Here, we provide an overview of current research and approaches focusing on targeting components of the FGFR/FGF signaling module to overcome drug resistance during anti-cancer therapy.

Abstract

Increased expression of both FGF proteins and their receptors observed in many cancers is often associated with the development of chemoresistance, limiting the effectiveness of currently used anti-cancer therapies. Malfunctioning of the FGF/FGFR axis in cancer cells generates a number of molecular mechanisms that may affect the sensitivity of tumors to the applied drugs. Of key importance is the deregulation of cell signaling, which can lead to increased cell proliferation, survival, and motility, and ultimately to malignancy. Signaling pathways activated by FGFRs inhibit apoptosis, reducing the cytotoxic effect of some anti-cancer drugs. FGFRs-dependent signaling may also initiate angiogenesis and EMT, which facilitates metastasis and also correlates with drug resistance. Therefore, treatment strategies based on FGF/FGFR inhibition (using receptor inhibitors, ligand traps, monoclonal antibodies, or microRNAs) appear to be extremely promising. However, this approach may lead to further development of resistance through acquisition of specific mutations, metabolism switching, and molecular cross-talks. This review brings together information on the mechanisms underlying the involvement of the FGF/FGFR axis in the generation of drug resistance in cancer and highlights the need for further research to overcome this serious problem with novel therapeutic strategies.

SP2509, an inhibitor of LSD1, exerts potential antitumor effects by targeting the JAK/STAT3 signaling

Hyperactivation of Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling promotes tumorigenesis and cancer progression. STAT3 participates in the essential processes of cell proliferation, survival, and differentiation in many types of tumors. In the present study, SP2509 was identified as a potent inhibitor of the JAK/STAT3 signaling pathway by high-throughput drug screening based on a STAT3-driven luciferase expression system. Our results indicated that SP2509 inhibits constitutive STAT3 activation and the expression of STAT3-driven downstream genes. Bcl-xL, c-Myc, and Cyclin D1 were downregulated after treatment with SP2509. In addition, SP2509 specifically inhibits JAK activity, which could cause cell cycle arrest, inhibit cell growth, and induce apoptosis of various cancer cells. These results confirmed that SP2509 inhibits tumor progression by suppressing the expression of JAK/STAT3 signaling and STAT3-related downstream genes. Moreover, we demonstrated that SP2509 inhibits tumor growth in vivo and induces cell death in vitro. SP2509-mediated inhibition of STAT3 phosphorylation is dependent on its original target lysine-specific demethylase 1 in cancer cells. In summary, our results indicate that SP2509 is a novel inhibitor of JAK/STAT3 signaling.

Modified Natriuretic Peptides and their Potential Role in Cancer Treatment

The natriuretic peptide family (NPs) is a group of natural endocrine hormones, containing a 17-amino acid ring structure connected by disulfide bonds of two cysteines. In this review, the members of the natriuretic peptide family and their corresponding receptors as well as the anti-cancer effects are introduced. Four cardiac hormones of NPs (ANP, VD, KP and LANP) can effectively inhibit the growth of human small cell lung cancer, breast cancer and other tumors and significantly reduce tumor volume in vivo. The in vitro experiments also show that cardiac hormones, CNP and urodilatin can effectively inhibit the growth of most tumor cells. We then further summarized the anti-cancer mechanism of natriuretic peptides. Finally, we introduce several methods that modify natriuretic peptides, leading to enhance their stability and prolong the biological effects of these peptides, which might be helpful for the clinical application in the future. Peptide therapy is a very promising field for cancer treatments since they can induce the death of cancer cells without dramatically affecting normal cells. The synthesis of a useful and stable natriuretic peptide can enhance the effect of cancer treatments and significantly reduce drug resistance and toxicity.

Stat3 loss in mesenchymal progenitors causes Job syndrome-like skeletal defects by reducing Wnt/β-catenin signaling

Job syndrome is a rare genetic disorder caused by STAT3 mutations and primarily characterized by immune dysfunction along with comorbid skeleton developmental abnormalities including osteopenia, recurrent fracture of long bones, and scoliosis. So far, there is no definitive cure for the skeletal defects in Job syndrome, and treatments are limited to management of clinical symptoms only. Here, we have investigated the molecular mechanism whereby Stat3 regulates skeletal development and osteoblast differentiation. We showed that removing Stat3 function in the developing limb mesenchyme or osteoprogenitor cells in mice resulted in shortened and bow limbs with multiple fractures in long bones that resembled the skeleton symptoms in the Job Syndrome. However, Stat3 loss did not alter chondrocyte differentiation and hypertrophy in embryonic development, while osteoblast differentiation was severely reduced. Genome-wide transcriptome analyses as well as biochemical and histological studies showed that Stat3 loss resulted in down-regulation of Wnt/β-catenin signaling. Restoration of Wnt/β-catenin signaling by injecting BIO, a small molecule inhibitor of GSK3, or crossing with a Lrp5 gain of function (GOF) allele, rescued the bone reduction phenotypes due to Stat3 loss to a great extent. These studies uncover the essential functions of Stat3 in maintaining Wnt/β-catenin signaling in early mesenchymal or osteoprogenitor cells and provide evidence that bone defects in the Job Syndrome are likely caused by Wnt/β-catenin signaling reduction due to reduced STAT3 activities in bone development. Enhancing Wnt/β-catenin signaling could be a therapeutic approach to reduce bone symptoms of Job syndrome patients.

IL-23R in laryngeal cancer: a cancer immunoediting process that facilitates tumor cell proliferation and results in cisplatin resistance

Oncogenic pathogens can disturb tissue homeostasis and initiate immune responses for oncogenicity clearance and homeostasis restoration, while failed clearance and chronic inflammation may result in tumorigenesis. The primary tumor development will undergo a cancer immunoediting process, including three phases, termed elimination, equilibrium and escape. Importantly, immune-edited tumor cells can not only reduce immunogenic molecular expression but also manipulate cytokines within the tumor environment (TME) for immune evasion and tumor proliferation. Many studies have revealed that IL-23R performed an essential role in mucous inflammation and tumorigenesis, and the role of IL-23R, either in tumor-infiltrating lymphocytes (TILs) or within immune-edited tumor cells, remained largely unknown in laryngeal cancer (LC). Here, we separately analyzed the IL-23R expression in LC TILs and tumor cells and found that high IL-23R expression in tumor cells was associated with moderate and poor tumor differentiation and an unfavorable prognosis. Furthermore, the real-time quantitative polymerase chain reaction analysis revealed that human LC tissues overexpress signal transducers and activators of transcription 3 (STAT3), and the relevance analysis found this STAT3 overexpression had a significant correlation with IL-23R expression. Besides, we isolated and cultured IL-23R+ human tumor cells from the postoperation tumor sample of three LC patients, and found that rhIL-23 could phosphorylate STAT3 (pSTAT3, residue Y705), which resulted in cancer cell proliferation and cisplatin resistance. These results indicate that IL-23R was a Hallmark of cancer immunoediting process, and targeting IL-23 should be considered as a therapeutic option for laryngeal function preservation and survival improvement.

Sex Hormones and Lung Inflammation

Inflammation is a characteristic marker in numerous lung disorders. Several immune cells, such as macrophages, dendritic cells, eosinophils, as well as T and B lymphocytes, synthetize and release cytokines involved in the inflammatory process. Gender differences in the incidence and severity of inflammatory lung ailments including asthma, chronic obstructive pulmonary disease (COPD), pulmonary fibrosis (PF), lung cancer (LC), and infectious related illnesses have been reported. Moreover, the effects of sex hormones on both androgens and estrogens, such as testosterone (TES) and 17β-estradiol (E2), driving characteristic inflammatory patterns in those lung inflammatory diseases have been investigated. In general, androgens seem to display anti-inflammatory actions, whereas estrogens produce pro-inflammatory effects. For instance, androgens regulate negatively inflammation in asthma by targeting type 2 innate lymphoid cells (ILC2s) and T-helper (Th)-2 cells to attenuate interleukin (IL)-17A-mediated responses and leukotriene (LT) biosynthesis pathway. Estrogens may promote neutrophilic inflammation in subjects with asthma and COPD. Moreover, the activation of estrogen receptors might induce tumorigenesis. In this chapter, we summarize the most recent advances in the functional roles and associated signaling pathways of inflammatory cellular responses in asthma, COPD, PF, LC, and newly occurring COVID-19 disease. We also meticulously deliberate the influence of sex steroids on the development and progress of these common and severe lung diseases.

Metabolic Rewiring in Radiation Oncology Toward Improving the Therapeutic Ratio

To meet the anabolic demands of the proliferative potential of tumor cells, malignant cells tend to rewire their metabolic pathways. Although different types of malignant cells share this phenomenon, there is a large intracellular variability how these metabolic patterns are altered. Fortunately, differences in metabolic patterns between normal tissue and malignant cells can be exploited to increase the therapeutic ratio. Modulation of cellular metabolism to improve treatment outcome is an emerging field proposing a variety of promising strategies in primary tumor and metastatic lesion treatment. These strategies, capable of either sensitizing or protecting tissues, target either tumor or normal tissue and are often focused on modulating of tissue oxygenation, hypoxia-inducible factor (HIF) stabilization, glucose metabolism, mitochondrial function and the redox balance. Several compounds or therapies are still in under (pre-)clinical development, while others are already used in clinical practice. Here, we describe different strategies from bench to bedside to optimize the therapeutic ratio through modulation of the cellular metabolism. This review gives an overview of the current state on development and the mechanism of action of modulators affecting cellular metabolism with the aim to improve the radiotherapy response on tumors or to protect the normal tissue and therefore contribute to an improved therapeutic ratio.

Reduced SOCS1 Expression in Lung Fibroblasts from Patients with IPF Is Not Mediated by Promoter Methylation or Mir155

The interleukin (IL)-6 family of cytokines and exaggerated signal transducer and activator of transcription (STAT)3 signaling is implicated in idiopathic pulmonary fibrosis (IPF) pathogenesis, but the mechanisms regulating STAT3 expression and function are unknown. Suppressor of cytokine signaling (SOCS)1 and SOCS3 block STAT3, and low SOCS1 levels have been reported in IPF fibroblasts and shown to facilitate collagen production. Fibroblasts and lung tissue from IPF patients and controls were used to examine the mechanisms underlying SOCS1 down-regulation in IPF. A significant reduction in basal SOCS1 mRNA in IPF fibroblasts was confirmed. However, there was no difference in the kinetics of activation, and methylation of SOCS1 in control and IPF lung fibroblasts was low and unaffected by 5′-aza-2′-deoxycytidine’ treatment. SOCS1 is a target of microRNA-155 and although microRNA-155 levels were increased in IPF tissue, they were reduced in IPF fibroblasts. Therefore, SOCS1 is not regulated by SOCS1 gene methylation or microRNA155 in these cells. In conclusion, we confirmed that IPF fibroblasts had lower levels of SOCS1 mRNA compared with control fibroblasts, but we were unable to determine the mechanism. Furthermore, although SOCS1 may be important in the fibrotic process, we were unable to find a significant role for SOCS1 in regulating fibroblast function.

Development and biological applications of sulfur-triazole exchange (SuTEx) chemistry

Sulfur electrophiles constitute an important class of covalent small molecules that have found widespread applications in synthetic chemistry and chemical biology. Various electrophilic scaffolds, including sulfonyl fluorides and arylfluorosulfates as recent examples, have been applied for protein bioconjugation to probe ligand sites amenable for chemical proteomics and drug discovery. In this review, we describe the development of sulfonyl-triazoles as a new class of electrophiles for sulfur-triazole exchange (SuTEx) chemistry. SuTEx achieves covalent reaction with protein sites through irreversible modification of a residue with an adduct group (AG) upon departure of a leaving group (LG). A principal differentiator of SuTEx from other chemotypes is the selection of a triazole heterocycle as the LG, which introduces additional capabilities for tuning the sulfur electrophile. We describe the opportunities afforded by modifications to the LG and AG alone or in tandem to facilitate nucleophilic substitution reactions at the SO2 center in cell lysates and live cells. As a result of these features, SuTEx serves as an efficient platform for developing chemical probes with tunable bioactivity to study novel nucleophilic sites on established and poorly annotated protein targets. Here, we highlight a suite of biological applications for the SuTEx electrophile and discuss future goals for this enabling covalent chemistry.

Efficacy of combination treatment using YHO-1701, an orally active STAT3 inhibitor, with molecular-targeted agents on cancer cell lines

Signal transducer and activator of transcription 3 (STAT3) plays a critical role in regulating cell growth, survival, and metastasis. STAT3 signaling is constitutively activated in various types of hematologic or solid malignancies. YHO-1701 has been developed as an orally available STAT3 inhibitor. Herein, YHO-1701 in combination with molecular-targeted agents was evaluated. Additive or synergistic effects were observed in a broad spectrum of “combination treatment + cell line” pairs. Of particular interest was the synergistic effect observed when YHO-1701 was combined with imatinib or dasatinib [breakpoint cluster region-abelson (BCR-ABL) inhibitors], osimertinib [epidermal growth factor receptor (EGFR) inhibitor], crizotinib, alectinib, or ceritinib [anaplastic lymphoma kinase (ALK) inhibitors]. The results further showed a close relationship between these synergistic effects and the cellular levels of the key molecules involved in the target pathways for YHO-1701 and each combination drug. The combination of YHO-1701 with alectinib resulted in significantly greater antitumor activity without exhibiting body weight loss in an NCI-H2228 [echinoderm microtubule-associated protein-like 4 (EML4)-ALK fusion] xenograft mouse model. Our results strongly suggest that the logical strategy in combination with the novel STAT3 inhibitor YHO-1701 and other mechanistically different targeted agents, could be a promising approach in future clinical settings.

The Multifaced Role of STAT3 in Cancer and Its Implication for Anticancer Therapy

Signal transducer and activator of transcription (STAT) 3 is one of the most complex regulators of transcription. Constitutive activation of STAT3 has been reported in many types of tumors and depends on mechanisms such as hyperactivation of receptors for pro-oncogenic cytokines and growth factors, loss of negative regulation, and excessive cytokine stimulation. In contrast, somatic STAT3 mutations are less frequent in cancer. Several oncogenic targets of STAT3 have been recently identified such as c-myc, c-Jun, PLK-1, Pim1/2, Bcl-2, VEGF, bFGF, and Cten, and inhibitors of STAT3 have been developed for cancer prevention and treatment. However, despite the oncogenic role of STAT3 having been widely demonstrated, an increasing amount of data indicate that STAT3 functions are multifaced and not easy to classify. In fact, the specific cellular role of STAT3 seems to be determined by the integration of multiple signals, by the oncogenic environment, and by the alternative splicing into two distinct isoforms, STAT3α and STAT3β. On the basis of these different conditions, STAT3 can act both as a potent tumor promoter or tumor suppressor factor. This implies that the therapies based on STAT3 modulators should be performed considering the pleiotropic functions of this transcription factor and tailored to the specific tumor type.

AMPK alleviates oxidative stress‑induced premature senescence via inhibition of NF-κB/STAT3 axis-mediated positive feedback loop

Stress-induced premature senescence (SIPS) is characterized by the secretion of a variety of inflammatory cytokines, chemokines, and proteases, which are defined collectively as the senescence-associated secretory phenotype (SASP). AMP-activated protein kinase (AMPK) activation contributes to SIPS prevention, and the impact of AMPK on SASP may be included, but the mechanisms governing this phenomenon have not elucidated. In this study, we showed that SIPS is accompanied by a dynamic fluctuation of NF-κB activation, which induces SASP production, whilst reinforcing and amplifying local STAT3 signalling and subsequently enhancing downstream senescence. NF-κB and STAT3 inhibitors attenuate oxidative stress-induced senescence in a time-dependent manner. Conditioned medium (CM) from senescent cells rich in SASP factors can induce growth arrest and promote senescence in healthy cells; accordingly, a STAT3 inhibitor blunts the SASP-induced senescence, indicating a positive feedback mechanism via the NF-κB/STAT3 pathway that sustains SASP production and promotes senescence. In addition, we confirmed that AMPK negatively regulates SASP production and senescence development associated with NF-κB/STAT3 inhibition. In summary, our results suggest that AMPK prevents oxidative stress-induced senescence development via inhibiting the NF-κB/SASP/STAT3 signalling mediated positive feedback loop.

Effects of STAT3 polymorphisms and pharmacokinetics on the clinical outcomes of gefitinib treatment in patients with EGFR-mutation positive non-small cell lung cancer

WHAT IS KNOWN AND OBJECTIVE

We investigated the correlations among signal transducer and activator of transcription 3 (STAT3) rs4796793C >G polymorphism, gefitinib pharmacokinetics and clinical responses in Japanese patients with non-small cell lung cancer receiving gefitinib therapy.

METHODS

Forty-five patients were enrolled in this study. Plasma trough concentrations (C₀ ) of gefitinib at the steady-state were measured by high-performance liquid chromatography.

RESULTS AND DISCUSSION

Patients having a gefitinib C₀ of at least ≥200 ng/mL had significantly longer PFS than patients having a C₀ of <200 ng/mL (median [95% confidence interval (CI)] PFS: 11.0 [8.2-13.7] and 5.3 [0.0-12.0] months, respectively, P = .042). There were no significant differences in PFS between patients with STAT3 rs4796793C/C and G alleles; however, patients with STAT3 rs4796793C/C having a gefitinib C₀ of ≥ 200 ng/mL had significantly longer progression-free survival (PFS) and overall survival (OS) than those with a C₀ of <200 ng/mL (median [95% CI] PFS: 11.4 [4.1-18.6] and 3.0 [0.0-7.0] months, respectively, P = .008; median [95% CI] OS: 20.6 [7.4-33.7] and 12.6 [10.1-15.1] months, respectively, P = .042). In patients with the STAT3 rs4796793G allele, there were no significant differences in PFS and OS between the two gefitinib C₀ groups. In addition, there were no significant differences in PFS or OS according to smoking, presence of proton pump inhibitor combination, or onset of side effects.

WHAT IS NEW AND CONCLUSION

Clinical outcomes of gefitinib in patients with the STAT3 rs4796793C/C genotype depended on plasma concentrations of gefitinib. In addition to information regarding EGFR mutations, the STAT3 rs4796793C >G polymorphism and gefitinib C₀ may be potential predictors of clinical outcomes after beginning of gefitinib therapy.

STAT3: Versatile Functions in Non-Small Cell Lung Cancer

Signal Transducer and Activator of Transcription 3 (STAT3) activation is frequently found in non-small cell lung cancer (NSCLC) patient samples/cell lines and STAT3 inhibition in NSCLC cell lines markedly impairs their survival. STAT3 also plays a pivotal role in driving tumor-promoting inflammation and evasion of anti-tumor immunity. Consequently, targeting STAT3 either directly or by inhibition of upstream regulators such as Interleukin-6 (IL-6) or Janus kinase 1/2 (JAK1/2) is considered as a promising treatment strategy for the management of NSCLC. In contrast, some studies also report STAT3 being a tumor suppressor in a variety of solid malignancies, including lung cancer. Here, we provide a concise overview of STAT3‘s versatile roles in NSCLC and discuss the yins and yangs of STAT3 targeting therapies.

Identification of novel regulators of STAT3 activity

STAT3 mediates signalling downstream of cytokine and growth factor receptors where it acts as a transcription factor for its target genes, including oncogenes and cell survival regulating genes. STAT3 has been found to be persistently activated in many types of cancers, primarily through its tyrosine phosphorylation (Y705). Here, we show that constitutive STAT3 activation protects cells from cytotoxic drug responses of several drug classes. To find novel and potentially targetable STAT3 regulators we performed a kinase and phosphatase siRNA screen with cells expressing either a hyperactive STAT3 mutant or IL6-induced wild type STAT3. The screen identified cell division cycle 7-related protein kinase (CDC7), casein kinase 2, alpha 1 (CSNK2), discoidin domain-containing receptor 2 (DDR2), cyclin-dependent kinase 8 (CDK8), phosphatidylinositol 4-kinase 2-alpha (PI4KII), C-terminal Src kinase (CSK) and receptor-type tyrosine-protein phosphatase H (PTPRH) as potential STAT3 regulators. Using small molecule inhibitors targeting these proteins, we confirmed dose and time dependent inhibition of STAT3-mediated transcription, suggesting that inhibition of these kinases may provide strategies for dampening STAT3 activity in cancers.

STAT3 Regulates the Onset of Oxidant-induced Senescence in Lung Fibroblasts

Idiopathic pulmonary fibrosis (IPF) is a chronic lung disease of unknown cause with a median survival of only 3 years. Other investigators and we have shown that fibroblasts derived from IPF lungs display characteristics of senescent cells, and that dysregulated activation of the transcription factor signal transducer and activator of transcription 3 (STAT3) correlates with IPF progression. The question of whether STAT3 activation is involved in fibroblast senescence remains unanswered. We hypothesized that inhibiting STAT3 activation after oxidant-induced senescence would attenuate characteristics of the senescent phenotype. We aimed to characterize a model of oxidant-induced senescence in human lung fibroblasts and to determine the effect of inhibiting STAT3 activity on the development of senescence. Exposing human lung fibroblasts to 150 μM hydrogen peroxide (H₂O₂) resulted in increased senescence-associated β-galactosidase content and expression of p21 and IL-6, all of which are features of senescence. The shift into senescence was accompanied by an increase of STAT3 translocation to the nucleus and mitochondria. Additionally, Seahorse analysis provided evidence of increased mitochondrial respiration characterized by increased basal respiration, proton leak, and an associated increase in superoxide (O₂^-) production in senescent fibroblasts. Targeting STAT3 activity using the small-molecule inhibitor STA-21 attenuated IL-6 production, reduced p21 levels, decreased senescence-associated β-galactosidase accumulation, and restored normal mitochondrial function. The results of this study illustrate that stress-induced senescence in lung fibroblasts involves the activation of STAT3, which can be pharmacologically modulated.

The eEF2 kinase-induced STAT3 inactivation inhibits lung cancer cell proliferation by phosphorylation of PKM2

BACKGROUND

Eukaryotic elongation factor-2 kinase (eEF2K) is a Ca 2+ /calmodulin (CaM)-dependent protein kinase that inhibits protein synthesis. However, the role of eEF2K in cancer development was reported paradoxically and remains to be elucidated.

METHODS

Herein, A549 cells with eEF2K depletion or overexpression by stably transfected lentivirus plasmids were used in vitro and in vivo study. MTT and colony assays were used to detect cell proliferation and growth. Extracellular glucose and lactate concentration were measured using test kit. Immunoblot and co-immunoprecipitation assays were used to examine the molecular biology changes and molecular interaction in these cells. LC-MS/MS analysis and [γ- 32 P] ATP kinase assay were used to identify combining protein and phosphorylation site. Nude mice was utilized to study the correlation of eEF2K and tumor growth in vivo.

RESULTS

We demonstrated that eEF2K inhibited lung cancer cells proliferation and affected the inhibitory effects of EGFR inhibitor gefitinib. Mechanistically, we showed that eEF2K formed a complex with PKM2 and STAT3, thereby phosphorylated PKM2 at T129, leading to reduced dimerization of PKM2. Subsequently, PKM2 impeded STAT3 phosphorylation and STAT3-dependent c-Myc expression. eEF2K depletion promoted the nuclear translocation of PKM2 and increased aerobic glycolysis reflected by increased lactate secretion and glucose.

CONCLUSIONS

Our findings define a novel mechanism underlying the regulation of cancer cell proliferation by eEF2K independent of its role in protein synthesis, disclosing the diverse roles of eEF2K in cell biology, which lays foundation for the development of new anticancer therapeutic strategies.

STAT3 signaling in ovarian cancer: a potential therapeutic target

Accumulating evidence has shown that Signal Transducer and Activator of Transcription 3 (STAT3) is thought to be a promising target for cancer therapy as STAT3 is frequently overexpressed in a wide range of cancer cells as well as clinical specimens, promoting tumor progression. It is widely accepted that STAT3 regulates a variety of cellular processes, such as tumor cell growth, survival, invasion, cancer stem cell-like characteristic, angiogenesis and drug-resistance. In this review, we focus on the role of STAT3 in tumorigenesis in ovarian cancer and discuss the existing inhibitors of STAT3 signaling that can be promisingly developed as the strategies for ovarian cancer therapy.

Activation of STAT3 and STAT5 Signaling in Epithelial Ovarian Cancer Progression: Mechanism and Therapeutic Opportunity

Epithelial ovarian cancer (EOC) is the most lethal of all gynecologic malignancies. Despite advances in surgical and chemotherapeutic options, most patients with advanced EOC have a relapse within three years of diagnosis. Unfortunately, recurrent disease is generally not curable. Recent advances in maintenance therapy with anti-angiogenic agents or Poly ADP-ribose polymerase (PARP) inhibitors provided a substantial benefit concerning progression-free survival among certain women with advanced EOC. However, effective treatment options remain limited in most recurrent cases. Therefore, validated novel molecular therapeutic targets remain urgently needed in the management of EOC. Signal transducer and activator of transcription-3 (STAT3) and STAT5 are aberrantly activated through tyrosine phosphorylation in a wide variety of cancer types, including EOC. Extrinsic tumor microenvironmental factors in EOC, such as inflammatory cytokines, growth factors, hormones, and oxidative stress, can activate STAT3 and STAT5 through different mechanisms. Persistently activated STAT3 and, to some extent, STAT5 increase EOC tumor cell proliferation, survival, self-renewal, angiogenesis, metastasis, and chemoresistance while suppressing anti-tumor immunity. By doing so, the STAT3 and STAT5 activation in EOC controls properties of both tumor cells and their microenvironment, driving multiple distinct functions during EOC progression. Clinically, increasing evidence indicates that the activation of the STAT3/STAT5 pathway has significant correlation with reduced survival of recurrent EOC, suggesting the importance of STAT3/STAT5 as potential therapeutic targets for cancer therapy. This review summarizes the distinct role of STAT3 and STAT5 activities in the progression of EOC and discusses the emerging therapies specifically targeting STAT3 and STAT5 signaling in this disease setting.

Global targeting of functional tyrosines using sulfur-triazole exchange chemistry

Covalent probes serve as valuable tools for global investigation of protein function and ligand binding capacity. Despite efforts to expand coverage of residues available for chemical proteomics (e.g. cysteine and lysine), a large fraction of the proteome remains inaccessible with current activity-based probes. Here, we introduce sulfur-triazole exchange (SuTEx) chemistry as a tunable platform for developing covalent probes with broad applications for chemical proteomics. We show modifications to the triazole leaving group can furnish sulfonyl probes with ~5-fold enhanced chemoselectivity for tyrosines over other nucleophilic amino acids to investigate, for the first time, more than 10,000 tyrosine sites in lysates and live cells. We discover that tyrosines with enhanced nucleophilicity are enriched in enzymatic, protein-protein interaction, and nucleotide recognition domains. We apply SuTEx as a chemical phosphoproteomics strategy to monitor activation of phosphotyrosine sites. Collectively, we describe SuTEx as a biocompatible chemistry for chemical biology investigations of the human proteome.

PTPRT epigenetic silencing defines lung cancer with STAT3 activation and can direct STAT3 targeted therapies

Signal Transducers and Activators of Transcription-3 (STAT3), a potent oncogenic transcription factor, is constitutively activated in lung cancer, but mutations in pathway genes are infrequent. Protein Tyrosine Phosphatase Receptor-T (PTPRT) is an endogenous inhibitor of STAT3 and PTPRT loss-of-function represents one potential mechanism of STAT3 hyperactivation as observed in other malignancies. We determined the role of PTPRT promoter methylation and sensitivity to STAT3 pathway inhibitors in non-small cell lung cancer (NSCLC). TCGA and Pittsburgh lung cancer cohort methylation data revealed hypermethylation of PTPRT associated with diminished mRNA expression in a subset of NSCLC patients. We report frequent hypermethylation of the PTPRT promoter which correlates with transcriptional silencing of PTPRT and increased STAT3 phosphorylation (Y705) as determined by methylation-specific PCR (MSP) and real time quantitative reverse transcription (RT)-PCR in NSCLC cell lines. Silencing of PTPRT using siRNA in H520 lung cancer cell line resulted in increased pSTAT3_Tyr705 and upregulation of STAT3 target genes such as Cyclin D1 and Bcl-X_L expression. We show this association of PRPRT methylation with upregulation of the STAT3 target genes Cyclin D1 and Bcl-X_L in patient derived lung tumour samples. We further demonstrate that PTPRT promoter methylation associated with different levels of pSTAT3_Ty705 in lung cancer cell lines had selective sensitivity to STAT3 pathway small molecule inhibitors (SID 864,669 and SID 4,248,543). Our data strongly suggest that silencing of PTPRT by promoter hypermethylation is an important mechanism of STAT3 hyperactivation and targeting STAT3 may be an effective approach for the development of new lung cancer therapeutics.

MicroRNA‑4500 suppresses tumor progression in non‑small cell lung cancer by regulating STAT3

Research has revealed that microRNA (miR)-4500 is downregulated in non-small cell lung cancer (NSCLC), and miR-4500 suppresses tumor growth by targeting lin-28 homolog B and NRAS proto-oncogene, GTPase. In the present study, it was reported that signal transducer and activator of transcription 3 (STAT3) may function as a novel target gene for miR-4500 in NSCLC. The experiments conducted in the present study confirmed that the miR-4500 expression was decreased in NSCLC tissues and cells compared with adjacent normal tissues and a normal lung cell line. miR-4500 suppressed the cell proliferation, migration, invasion and promoted apoptosis of the human NSCLC cell lines A549 and H1975. Expression of STAT3 was negatively correlated with miR-4500 expression in vivo. A luciferase reporter assay suggested that miR-4500 directly targeted the 3′ untranslated region of STAT3. The tumor inhibition effect of small interfering RNA STAT3 in A549 and H1975 lines may be partially impaired by a miR-4500 inhibitor. The results of the present study suggests that miR-4500 may be a tumor suppressor and a potential therapeutic target in NSCLC.

BCR-ABL Independent Mechanisms of Resistance in Chronic Myeloid Leukemia

Not all chronic myeloid leukemia (CML) patients are cured with tyrosine kinase inhibitors (TKIs), and a proportion of them develop resistance. Recently, continuous BCR-ABL gene expression has been found in resistant cells with undetectable BCR-ABL protein expression, indicating that resistance may occur through kinase independent mechanisms, mainly due to the persistence of leukemia stem cells (LSCs). LSCs reside in the bone marrow niche in a quiescent state, and are characterized by a high heterogeneity in genetic, epigenetic, and transcriptional mechanisms. New approaches based on single cell genomics have offered the opportunity to identify distinct subpopulations of LSCs at diagnosis and during treatment. In the one hand, TKIs are not able to efficiently kill CML-LSCs, but they may be responsible for the modification of some LSCs characteristics, thus contributing to heterogeneity within the tumor. In the other hand, the bone marrow niche is responsible for the interactions between surrounding stromal cells and LSCs, resulting in the generation of specific signals which could favor LSCs cell cycle arrest and allow them to persist during treatment with TKIs. Additionally, LSCs may themselves alter the niche by expressing various costimulatory molecules and secreting suppressive cytokines, able to target metabolic pathways, create an anti-apoptotic environment, and alter immune system functions. Accordingly, the production of an immunosuppressant milieu may facilitate tumor escape from immune surveillance and induce chemo-resistance. In this review we will focus on BCR-ABL-independent mechanisms, analyzing especially those with a potential clinical impact in the management of CML patients.

Inhibition of Tyrosine-Phosphorylated STAT3 in Human Breast and Lung Cancer Cells by Manuka Honey is Mediated by Selective Antagonism of the IL-6 Receptor

Aberrantly high levels of tyrosine-phosphorylated signal transducer and activator of transcription 3 (p-STAT3) are found constitutively in ~50% of human lung and breast cancers, acting as an oncogenic transcription factor. We previously demonstrated that Manuka honey (MH) inhibits p-STAT3 in breast cancer cells, but the exact mechanism remained unknown. Herein, we show that MH-mediated inhibition of p-STAT3 in breast (MDA-MB-231) and lung (A549) cancer cell lines is accompanied by decreased levels of gp130 and p-JAK2, two upstream components of the IL-6 receptor (IL-6R) signaling pathway. Using an ELISA-based assay, we demonstrate that MH binds directly to IL-6Rα, significantly inhibiting (~60%) its binding to the IL-6 ligand. Importantly, no evidence of MH binding to two other cytokine receptors, IL-11Rα and IL-8R, was found. Moreover, MH did not alter the levels of tyrosine-phosphorylated or total Src family kinases, which are also constitutively activated in cancer cells, suggesting that signaling via other growth factor receptors is unaffected by MH. Binding of five major MH flavonoids (luteolin, quercetin, galangin, pinocembrin, and chrysin) was also tested, and all but pinocembrin could demonstrably bind IL-6Rα, partially (30-35%) blocking IL-6 binding at the highest concentration (50 μM) used. In agreement, each flavonoid inhibited p-STAT3 in a dose-dependent manner, with estimated IC50 values in the 3.5-70 μM range. Finally, docking analysis confirmed the capacity of each flavonoid to bind in an energetically favorable configuration to IL-6Rα at a site predicted to interfere with ligand binding. Taken together, our findings identify IL-6Rα as a direct target of MH and its flavonoids, highlighting IL-6R blockade as a mechanism for the anti-tumor activity of MH, as well as a viable therapeutic target in IL-6-dependent cancers.

Janus kinase JAK1 maintains the ovarian reserve of primordial follicles in the mouse ovary

STUDY QUESTION

Is the Janus kinase and signal transducer and activator of transcription (JAK-STAT) signalling pathway involved in ovarian follicle development and primordial follicle activation?

SUMMARY ANSWER

JAK1 is a key factor involved in the regulation of primordial follicle activation and maintenance of the ovarian reserve.

WHAT IS KNOWN ALREADY

A series of integrated, intrinsic signalling pathways (including PI3K/AKT, mTOR and KITL) are responsible for regulating the ovarian reserve of non-growing primordial follicles and ultimately female fertility. The JAK-STAT signal transduction pathway is highly conserved with established roles in cell division and differentiation. Key pathway members (specifically JAK1, STAT3 and SOCS4) have been previously implicated in early follicle development.

STUDY DESIGN, SIZE, DURATION

A laboratory animal study was undertaken using the C57Bl/6 inbred mouse strain as a model for human ovarian follicle development. To determine which Jak genes were most abundantly expressed during primordial follicle activation, mRNA expression was analysed across a developmental time-course, with ovaries collected from female mice at post-natal days 1 (PND1), 4 (PND4), 8 (PND8), as well as at 6 weeks (6WK) and 7 months (7MTH) (n ≥ 4). Functional analysis of JAK1 was performed on PND2 mouse ovaries subjected to in vitro explant culture treated with 12.5 μM Ruxolitinib (JAK inhibitor) or vehicle control (DMSO) for 48 h prior to histological assessment (n ≥ 4).

PARTICIPANTS/MATERIALS, SETTING, METHODS

The expression and localization of the JAK family during ovarian follicle development in the C57Bl/6 inbred mouse strain were evaluated using quantitative PCR, immunoblotting and immunolocalisation. Functional studies were undertaken using the JAK inhibitor Ruxolitinib to investigate the underpinning cellular mechanisms via biochemical in vitro inhibition and histological assessment of intact neonate ovaries. All experiments were replicated at least three times using tissue from different mice unless otherwise stated.

MAIN RESULTS AND THE ROLE OF CHANCE

Jak1 is the predominant Jak mRNA expressed in the C57Bl/6 mouse ovary across all developmental time-points assessed (P ≤ 0.05). Forty-eight hour inhibition of JAK1 with Ruxolitinib of PND2 ovaries in vitro demonstrated concomitant acceleration of primordial follicle activation and apoptosis (P ≤ 0.001) and upregulation of downstream JAK-STAT pathway members STAT3 and suppressors of cytokine signalling 4 (SOCS4).

LARGE-SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Results are shown in one species, the C57Bl/6 mouse strain as an established model of human ovary development. Ruxolitinib also inhibits JAK2, with decreased efficacy. However, Jak2 mRNA had limited expression in the mouse ovary, particularly at the neonatal stages of follicle development, thus any effect of Ruxolitinib on primordial follicle activation was unlikely to be mediated via this isoform.

WIDER IMPLICATIONS OF THE FINDINGS

This study supports a key role for JAK1 in the maintenance and activation of primordial follicles, with potential for targeting the JAK-STAT pathway as a method of regulating the ovarian reserve and female fertility.

STUDY FUNDING AND COMPETING INTEREST(S)

This project has been funded by the Australian National Health and Medical Research Council (G1600095) and The Hunter Medical Research Institute Bob and Terry Kennedy Children's Research Project Grant in Pregnancy & Reproduction (G1501433). All authors declare no conflict of interests.

Antitumor activity of novel pyrazole-based small molecular inhibitors of the STAT3 pathway in patient derived high grade glioma cells

Abnormal activation of signal transducer and activator of transcription 3 (STAT3) transcription factor has been observed in many human cancers with roles in tumor initiation, progression, drug resistance, angiogenesis and immunosuppression. STAT3 is constitutively activated in a variety of cancers including adult high grade gliomas (aHGGs) such as glioblastoma (GBM), and pediatric high grade gliomas (pHGG). Inhibiting STAT3 is a promising target-specific chemotherapeutic strategy for tumors with aberrant STAT3 signaling. Here we investigated the antitumor effects of novel pyrazole-based STAT3 pathway inhibitors named MNS1 (Mayo Neurosurgery 1) in both pediatric and adult HGG tumor cells. MNS1 compounds selectively decreased cell viability and proliferation in patient-derived HGG cells with minimal toxicity on normal human astrocytes. These inhibitors selectively blocked IL-6-induced STAT3 phosphorylation and nuclear localization of pSTAT3 without affecting other signaling molecules including Akt, STAT1, JAK2 or ERK1/2 phosphorylation. Functional analysis showed that MNS1 compounds induced apoptosis and decrease tumor migration. The anti-tumor effects extended into a murine pHGG (diffuse intrinsic pontine glioma) patient derived xenograft, and systemic toxicity was not evident during dose escalation in mice. These results support further development of STAT3 inhibitors for both pediatric and adult HGG.

Effects of LncRNA Lnc-LIF-AS on cell proliferation, migration and invasion in a human cervical cancer cell line

This study explored the effect of LncRNA Lnc-LIF-AS on cell proliferation, migration and invasion in the human cervical cancer (HCC) cell line SiHa. SiHa cells had the lowest expression of Lnc-LIF-AS in the 4 human cervical cancer cell lines (SiHa, ME-180, C-33A and HeLa) and were transfected and divided into the SiHa/con (transfected with pMIGRI) cell group, SiHa/Lnc-LIF-AS (transfected with pMIGRI-Lnc-LIF-AS) cell group, and SiHa/Lnc-LIF-AS-DN (transfected with pMIGRI-Lnc-LIF-AS-DN, in which the sequences overlapping with LIF mRNA was deleted) cell group. Overexpression of Lnc-LIF-AS could promote the proliferation, colony formation, invasion and migration in SiHa and ME-180 cells. And the low expression of Lnc-LIF-AS suppress the proliferation, colony formation invasion and migration in HeLa cells when the Lnc-LIF-AS expression has been suppressed. In the SiHa/Lnc-LIF-AS cells group, the cell cycle was mainly halted in the S phase and overexpression of Lnc-LIF-AS had no effect on the apoptosis of SiHa cells. Overexpression of Lnc-LIF-AS could promote the secretion of LIF in SiHa cells, and the supernatant from SiHa/Lnc-LIF-AS cells could promote cell proliferation in the SiHa/con cells. The STAT3 inhibitor could inhibit cell proliferation in the SiHa/Lnc-LIF-AS cells. The expression level of Lnc-LIF-AS in cervical cancer tissues was higher than that in normal tissues and the expression level of Lnc-LIF-AS was positively correlated with the level of LIF. In the SiHa/con and SiHa/Lnc-LIF-AS-DN cell groups, there were no significant differences in cell proliferation, cell migration and cell invasion. The overexpression of Lnc-LIF-AS can promote cell proliferation, migration and invasion in cervical cancer cells, and the core function domain of this lncRNA was located in the overlapping a 3'-UTR base sequence of LIF mRNA.

SHP2 Inhibition Overcomes RTK-Mediated Pathway Reactivation in KRAS-Mutant Tumors Treated with MEK Inhibitors

FGFR1 was recently shown to be activated as part of a compensatory response to prolonged treatment with the MEK inhibitor trametinib in several KRAS-mutant lung and pancreatic cancer cell lines. We hypothesize that other receptor tyrosine kinases (RTK) are also feedback-activated in this context. Herein, we profile a large panel of KRAS-mutant cancer cell lines for the contribution of RTKs to the feedback activation of phospho-MEK following MEK inhibition, using an SHP2 inhibitor (SHP099) that blocks RAS activation mediated by multiple RTKs. We find that RTK-driven feedback activation widely exists in KRAS-mutant cancer cells, to a less extent in those harboring the G13D variant, and involves several RTKs, including EGFR, FGFR, and MET. We further demonstrate that this pathway feedback activation is mediated through mutant KRAS, at least for the G12C, G12D, and G12V variants, and wild-type KRAS can also contribute significantly to the feedback activation. Finally, SHP099 and MEK inhibitors exhibit combination benefits inhibiting KRAS-mutant cancer cell proliferation in vitro and in vivo These findings provide a rationale for exploration of combining SHP2 and MAPK pathway inhibitors for treating KRAS-mutant cancers in the clinic.

Organic dust induces inflammatory gene expression in lung epithelial cells via ROS-dependent STAT-3 activation

Exposure to dust in agricultural and animal environments, known as organic dust, is associated with the development of respiratory symptoms and respiratory diseases. Inflammation is a key feature of lung pathologies associated with organic dust exposure, and exposure to organic dust induces the expression of several immune and inflammatory mediators. However, information on transcription factors and cellular and molecular mechanisms controlling the production of immune and inflammatory mediators induced by organic dust is limited. In this study, we have identified STAT-3 as an important transcription factor controlling the induction of expression of immune and inflammatory mediators by poultry dust extracts in airway epithelial cells and in mouse lungs and delineated the cellular pathway for STAT-3 activation. Poultry dust extract activated STAT-3 phosphorylation in Beas2B and normal human bronchial epithelial cells and in mouse lungs. Chemical inhibition and siRNA knockdown of STAT-3 suppressed induction of immune and inflammatory mediator expression. Antioxidants suppressed the increase of STAT-3 phosphorylation induced by poultry dust extract indicating that oxidative stress [elevated reactive oxygen species (ROS) levels] is important for the activation. Chemical inhibition and siRNA knockdown experiments demonstrated that STAT-3 activation is dependent on the activation of nonreceptor tyrosine-protein kinase 2 (TYK2) and epidermal growth factor receptor (EGFR) tyrosine kinases. Our studies show that poultry dust extract controls the induction of immune and inflammatory mediator expression via a cellular pathway involving oxidative stress-mediated STAT-3 activation by TYK2 and EGFR tyrosine kinases.