STAT3 signaling in prostate cancer progression and therapy resistance: An oncogenic pathway with diverse functions

pSTAT3 Expression is Increased in Advanced Prostate Cancer in Post-Initiation of Androgen Deprivation Therapy

BACKGROUND

The transcription factor Signal Transducer and Activator of Transcription 3 (STAT3) plays a role in carcinogenesis and is involved in processes, such as proliferation, differentiation, drug resistance and immunosuppression. STAT3 can be activated by phosphorylation of tyrosine at position 705 (pSTAT3Tyr705) or serine at 727 (pSTAT3Ser727). High expression levels of pSTAT3 are implicated in advanced stages of prostate cancer (PCa) and are known to interact with the androgen receptor signaling pathway. However, not much is known about how androgen deprivation therapy (ADT) in advanced disease affects pSTAT3 expression. The aim of this study was to determine the influence of ADT on pSTAT3 expression in PCa tissue.

METHODS

The study cohort came from a PCa tissue microarray resource containing prostate specimens from patients before and post-initiation of ADT. Tissue samples from 111 patients were immunostained for pSTAT3Tyr705 and pSTAT3Ser727. H-score was used to evaluate the intensity and the percentage of pSTAT3 expression in malignant epithelial and stromal compartments. Univariate and multivariable Cox regression analyses were used to assess pSTAT3Tyr705 and pSTAT3Ser727 as biomarkers of oncological outcome in patients undergoing ADT.

RESULTS

Post-ADT PCa samples demonstrated increased nuclear and cytoplasmic levels of pSTAT3Ser727 in the stroma compared to pre-ADT samples, whereas pSTAT3Tyr705 expression was increased significantly in both stromal and malignant epithelial compartments except for stromal cytoplasm. High cytoplasmic pSTAT3Ser727 in stromal compartments correlated with reduced overall survival, shorter time to castration-resistant PCa development, and decreased metastasis-free survival. An increase in nuclear and cytoplasmic pSTAT3Ser727 expression within the stromal compartment of post-ADT samples corresponded to a shorter time to CRPC development, which was not observed for pSTAT3Tyr705. Multivariable survival analysis using Cox's regression identified that high cytoplasmic pSTAT3Ser727 expression in the stroma of post-ADT samples and pT3 or pT4-stage were associated with worse overall survival and 5-year metastasis-free survival (MFS).

CONCLUSIONS

This study presents novel insights into the impact of ADT on the expression levels of pSTAT3Tyr705 and pSTAT3Ser727 in PCa. Cytoplasmic pSTAT3Ser727 status of cancer-associated stromal cells in post-ADT samples may serve as an independent prognostic marker for OS and 5-year MFS, identifying prostate cancer patients prone to developing resistance to ADT.

Enzymatic TET-1 inhibition highlights different epigenetic behaviours of IL-1β and TNFα in tumour progression of OS cell lines

Osteosarcoma (OS) is the most frequent primary malignant bone tumour, whose heterogeneity represents a major challenge for common antitumour therapies. Inflammatory cytokines are known to be necessary for OS progression. Therefore, to optimise therapy, it is important to discover reliable biomarkers by identifying the mechanism generating OS and investigating the inflammatory pathways that support the undifferentiated state. In this work, we highlight the differences of epigenetic activities of IL-1β and TNFα, and the susceptibility of TET-1 enzymatic inhibition, in tumour progression of three different OS cell lines. Investigating DNA methylation of IL-6 promoter and determining its expression, we found that TET enzymatic inhibition influences proliferation induced by inflammatory cytokines in OS cell lines. Moreover, Bobcat 339 treatment blocks IL-1β epigenetic action on IL-6 promoter, while only partially those of TNFα as well as inhibits IL-1β-dependent epithelial-mesenchymal transition (EMT) process, but only partially those of TNFα. In conclusion, this work highlights that IL-1β and TNFα have different effects on DNA demethylation in OS cell lines, making DNA methylation a potential biomarker of disease. Specifically, in IL-1β treatment, TET-1 inhibition completely blocks tumour progression, while in TNFα actions, it is only partially effective. Given that these two inflammatory pathways can be therapeutic targets for treating these tumours, knowledge of their distinct epigenetic behaviours can be useful for developing precise and specific therapeutic strategies for this disease.

Dysregulated expression of the suppressors of cytokine signaling (SOCS) contributes to the development of prostate cancer

Different types of cytokines, growth factors, or hormones present within the tumor microenvironment that can activate the JAK-STAT signaling pathway by binding to their specific cell surface receptors. The constitutive activation of the JAK-STAT pathway can promote uncontrolled cell proliferation and prevent apoptosis contributing to tumor development. Activation of the JAK-STAT pathway is controlled by several regulatory molecules, particularly the suppressor of cytokine signaling (SOCS) family consisting of eight members, which include SOCS1-SOCS7 and the cytokine-inducible SH2-containing (CIS) proteins. In prostate cancer cells, the irregular expression of the SOCS1-SOCS3, SOCS5-SOCS7 as well as CIS can similarly and differentially result in the initiation of various cellular signaling pathways (in particular JAK-STAT3, MAPK, ERK) that promote cell proliferation, migration, invasion and viability; cell cycle progression; epithelial-mesenchymal transition; angiogenesis; resistance to therapy; immune evasion; and chronic inflammation within the tumor microenvironment which lead to tumor progression, metastasis and poor prognosis. Epigenetic modifications, mainly due to DNA methylation, microRNAs, pro-inflammatory cytokines, growth factors and androgens can influence the expression of the SOCS molecules in prostate cancer cells. Using strategies to modulate, restore or enhance the expression of SOCS proteins, may help overcome treatment resistance and improve the efficacy of existing therapies. In this review, we provide a comprehensive explanation regarding SOCS dysregulation in prostate cancer to provide insights into the mechanisms underlying the dysregulation of SOCS proteins. This knowledge may pave the way for the development of novel therapeutic strategies to manage prostate cancer by restoring and modulating the expression of SOCS molecules.

PGC1α as a downstream effector of KDM5B promotes the progression of androgen receptor-positive and androgen receptor-negative prostate cancers

PPARγ coactivator-1α (PGC1α), as a co-activator, is known to optimize the action of several transcription factors, including androgen receptor (AR). However, the precise functions of PGC1α in prostate cancer, particularly those via the non-AR pathways, remain poorly understood. Meanwhile, our bioinformatics search suggested that PGC1α could be a direct downstream target of lysine-specific demethylase 5B (KDM5B/JARID1B/PLU1). We herein aimed to investigate how PGC1α induced prostate cancer outgrowth. Immunohistochemistry in radical prostatectomy specimens showed that the levels of PGC1α expression were significantly higher in prostatic adenocarcinoma [H-score (mean ± SD): 179.0 ± 111.6] than in adjacent normal-appearing tissue (16.7 ± 29.9, P<0.001) or high-grade prostatic intraepithelial neoplasia (79.0 ± 94.7, P<0.001). Although there were no strong associations of PGC1α expression with tumor grade or stage, outcome analysis revealed that patients with high PGC1α (H-score of ≥200) tumor had a significantly higher risk of postoperative biochemical recurrence even in a multivariable setting (hazard ratio 5.469, P=0.004). In prostate cancer LNCaP and C4-2 cells, PGC1α silencing resulted in considerable reduction in the levels of prostate-specific antigen expression. Interestingly, PGC1α silencing inhibited the cell viability of not only AR-positive LNCaP/C4-2/22Rv1 lines but also AR-negative PC3/DU145 lines. Chromatin immunoprecipitation assay further revealed the binding of KDM5B to the promoter region of PGC1α in these lines. Additionally, treatment with a KDM5 inhibitor KDM5-C70 considerably reduced the expression of PGC1α and prostate-specific antigen, as well as the cell viability of all the AR-positive and AR-negative lines examined. PGC1α silencing or KDM5-C70 treatment also down-regulated the expression of phospho-JAK2 and phospho-STAT3 in both AR-positive and AR-negative cells. These findings suggest the involvement of PGC1α, as a downstream effector of KDM5B, in prostate cancer progression via both AR-dependent and AR-independent pathways. KDM5B-PGC1α is thus a potential therapeutic target for both androgen-sensitive and castration-resistant tumors. Meanwhile, PGC1α overexpression may serve as a useful prognosticator in those undergoing radical prostatectomy.

Improvement of Docetaxel Efficacy through Simultaneous Blockade of Transcription Factors NF-κB and STAT-3 Using Pentoxifylline and Stattic in Prostate Cancer Cells

Prostate cancer (PCa) is a common and deadly disease in men. It is often diagnosed at advanced stages, at which point patients are treated mainly with docetaxel (DTX), which is effective but limited by resistance and side effects. Overactivation of the transcription factors NF-κB and STAT-3 plays a critical role in the development, progression, and chemoresistance of PCa. In this regard, the blockade of NF-κB with pentoxifylline (PTX) or STAT-3 with Stattic (STT) is known to increase the sensitivity of tumor cells to chemotherapy in both in vitro and in vivo models. We investigated whether simultaneous blockade with PTX and STT increases the efficacy of the DTX treatment in inducing apoptosis in metastatic castration-resistant PCa DU-145 cells. Our results showed that the combination of PTX + STT led to higher levels of apoptosis, regardless of whether or not DTX was present in the treatment. Determining caspases and ΔΨm indicates that the intrinsic caspase pathway of apoptosis is principally favored. In addition, this combination inhibited proliferation and colony formation and arrested the cell cycle in the G1 phase. These results indicate that the combination of the PTX + STAT-3 inhibitor could potentiate DTX effectively, opening the possibility of effective treatments in PCa.

Immunohistochemical analyses reveal FoxP3 expressions in spleen and colorectal cancer in mice treated with AOM/DSS, and their suppression by glycyrrhizin

We previously demonstrated that glycyrrhizin (GL) suppressed inflammation and carcinogenesis in an azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced murine model of colorectal cancer (CC). In this study, we found an accumulation of regulatory T cells (Tregs) in the spleen and suppression by GL in model mice. ICR mice were divided into four groups: Control, GL, CC, and GL-treated CC (CC+GL), and were sacrificed 20 weeks after AOM/DSS treatment. We measured spleen weight, areas of white and red pulp, and CD8+ T cells (cytotoxic T lymphocytes, CTL), and CD11c-positive cells (dendritic cells) in splenic tissues and forkhead box protein 3 (FoxP3)-positive cells (Tregs) in colorectal and splenic tissues. In all cases, the CC group showed a significant increase compared with those in Control group, and GL administration significantly attenuated this increase. These results indicate that Tregs accumulated in the spleen may participate in inflammation-related carcinogenesis by suppressing CTL. We also suggest that GL which binds to high-mobility group box 1 (HMGB1), suppresses carcinogenesis with decreasing Tregs in the spleen. Furthermore, there was an expression of FoxP3 in cancer cells, indicating that it may be involved in the malignant transformation of cancer cells.

SLC4A4 is a novel driver of enzalutamide resistance in prostate cancer

The androgen receptor signaling inhibitor (ARSI) enzalutamide (Enz) has shown critical efficacy in the treatment of advanced prostate cancer (PCa). However, the development of drug resistance is a significant factor contributing to mortality in PCa patients. We aimed to explore the key mechanisms of Enz-resistance. Through analysis of GEO databases, we identified SLC4A4 as a novel driver in Enz resistance. Long-term Enz treatment leads to the up-regulation of SLC4A4, which in turn mediates P53 lactylation via the NF-κB/STAT3/SLC4A4 axis, ultimately leading to the development of Enz resistance and progression of PCa. SLC4A4 knockdown overcomes Enz resistance both in vitro and in vivo. Hence, our results suggest that targeting SLC4A4 could be a promising therapeutic strategy for Enz resistance. STATEMENT OF SIGNIFICANCE: SLC4A4 is a novel driver of enzalutamide resistance.

The Specific ROCK2 Inhibitor KD025 Alleviates Glycolysis through Modulating STAT3-, CSTA- and S1PR3-Linked Signaling in Human Trabecular Meshwork Cells

To investigate the biological significance of Rho-associated coiled-coil-containing protein kinase (ROCK) 2 in the human trabecular meshwork (HTM), changes in both metabolic phenotype and gene expression patterns against a specific ROCK2 inhibitor KD025 were assessed in planar-cultured HTM cells. A seahorse real-time ATP rate assay revealed that administration of KD025 significantly suppressed glycolytic ATP production rate and increased mitochondrial ATP production rate in HTM cells. RNA sequencing analysis revealed that 380 down-regulated and 602 up-regulated differentially expressed genes (DEGs) were identified in HTM cells treated with KD025 compared with those that were untreated. Gene ontology analysis revealed that DEGs were more frequently related to the plasma membrane, extracellular components and integral cellular components among cellular components, and related to signaling receptor binding and activity and protein heterodimerization activity among molecular functions. Ingenuity Pathway Analysis (IPA) revealed that the detected DEGs were associated with basic cellular biological and physiological properties, including cellular movement, development, growth, proliferation, signaling and interaction, all of which are associated with cellular metabolism. Furthermore, the upstream regulator analysis and causal network analysis estimated IL-6, STAT3, CSTA and S1PR3 as possible regulators. Current findings herein indicate that ROCK2 mediates the IL-6/STAT3-, CSTA- and S1PR3-linked signaling related to basic biological activities such as glycolysis in HTM cells.

Chaga mushroom extract suppresses oral cancer cell growth via inhibition of energy metabolism

Oral cancer stands as a prevalent maligancy worldwide; however, its therapeutic potential is limited by undesired effects and complications. As a medicinal edible fungus, Chaga mushroom (Inonotus obliquus) exhibits anticancer effects across diverse cancers. Yet, the precise mechanisms underlying its efficacy remain unclear. We explored the detailed mechanisms underlying the anticancer action of Chaga mushroom extract in oral cancer cells (HSC-4). Following treatment with Chaga mushroom extracts, we analyzed cell viability, proliferation capacity, glycolysis, mitochondrial respiration, and apoptosis. Our findings revealed that the extract reduced cell viability and proliferation of HSC-4 cells while arresting their cell cycle via suppression of STAT3 activity. Regarding energy metabolism, Chaga mushroom extract inhibited glycolysis and mitochondrial membrane potential in HSC-4 cells, thereby triggering autophagy-mediated apoptotic cell death through activation of the p38 MAPK and NF-κB signaling pathways. Our results indicate that Chaga mushroom extract impedes oral cancer cell progression, by inhibiting cell cycle and proliferation, suppressing cancer cell energy metabolism, and promoting autophagy-mediated apoptotic cell death. These findings suggest that this extract is a promising supplementary medicine for the treatment of patients with oral cancer.

STAT3 mediates ECM stiffness-dependent progression in ovarian cancer

The treatment of ovarian cancer remains a medical challenge and its malignant progression is connected with obvious changes in both tissue and cell stiffness. However, the accurate mechanical-responsive molecules and mechanism remains unclear in ovarian cancer. Based on our previous results combined with the crucial regulatory role of STAT3 in the malignant progression of various cancer types, we want to investigate the relationship between STAT3 and matrix stiffness in ovarian cancer and further explore the potential mechanisms. Collagen-coated polyacrylamide gels (1, 6, and 60 kPa) were prepared to mimic soft or hard matrix stiffness. Western blotting, qRT-PCR, flow cytometry, IHC, EdU assays, and TEM were used to evaluate the effect of STAT3 in vitro under different matrix stiffnesses. Furthermore, a BALB/c nude mouse model was established to assess the relationship in vivo. Our results confirmed the differential expression of STAT3/p-STAT3 not only in normal and malignant ovarian tissues but also under different matrix stiffnesses. Furthermore, we verified that STAT3 was a mechanically responsive gene both in vitro and in vivo, and the mechanical response was carried out by altering the migration-related molecules (TNFAIP1) and adhesion-related molecules (LPXN, CNN3). The novel findings suggest that STAT3, a potential therapeutic target for clinical diagnosis and treatment, is a mechanically responsive gene that responds to matrix stiffness, particularly regulation in migration and adhesion in the progression of ovarian cancer.

Targeting the tumor microenvironment, a new therapeutic approach for prostate cancer

BACKGROUND

A growing number of studies have shown that in addition to adaptive immune cells such as CD8 + T cells and CD4 + T cells, various other cellular components within prostate cancer (PCa) tumor microenvironment (TME), mainly tumor-associated macrophages (TAMs), cancer-associated fibroblasts (CAFs) and myeloid-derived suppressor cells (MDSCs), have been increasingly recognized as important modulators of tumor progression and promising therapeutic targets.

OBJECTIVE

In this review, we aim to delineate the mechanisms by which TAMs, CAFs and MDSCs interact with PCa cells in the TME, summarize the therapeutic advancements targeting these cells and discuss potential new therapeutic avenues.

METHODS

We searched PubMed for relevant studies published through December 10 2023 on TAMs, CAFs and MDSCs in PCa.

RESULTS

TAMs, CAFs and MDSCs play a critical role in the tumorigenesis, progression, and metastasis of PCa. Moreover, they substantially mediate therapeutic resistance against conventional treatments including anti-androgen therapy, chemotherapy, and immunotherapy. Therapeutic interventions targeting these cellular components have demonstrated promising effects in preclinical models and several clinical trials for PCa, when administrated alone, or combined with other anti-cancer therapies. However, the lack of reliable biomarkers for patient selection and incomplete understanding of the mechanisms underlying the interactions between these cellular components and PCa cells hinder their clinical translation and utility.

CONCLUSION

New therapeutic strategies targeting TAMs, CAFs, and MDSCs in PCa hold promising prospects. Future research endeavors should focus on a more comprehensive exploration of the specific mechanisms by which these cells contribute to PCa, aiming to identify additional drug targets and conduct more clinical trials to validate the safety and efficacy of these treatment strategies.

Updated review on analysis of long non-coding RNAs as emerging diagnostic and therapeutic targets in prostate cancers

Despite advancements, prostate cancers (PCa) pose a significant global health challenge due to delayed diagnosis and therapeutic resistance. This review delves into the complex landscape of prostate cancer, with a focus on long-noncoding RNAs (lncRNAs). Also explores the influence of aberrant lncRNAs expression in progressive PCa stages, impacting traits like proliferation, invasion, metastasis and therapeutic resistance. The study elucidates how lncRNAs modulate crucial molecular effectors, including transcription factors and microRNAs, affecting signaling pathways such as androgen receptor signaling. Besides, this manuscript sheds light on novel concepts and mechanisms driving PCa progression through lncRNAs, providing a critical analysis of their impact on the disease's diverse characteristics. Besides, it discusses the potential of lncRNAs as diagnostics and therapeutic targets in PCa. Collectively, this work highlights state of art mechanistic comprehension and rigorous scientific approaches to advance our understanding of PCa and depict innovations in this evolving field of research.

Association of S19W polymorphism in APOA5 gene and serum lipid levels in patients with type 2 diabetic nephropathy

OBJECTIVES

Type 2 diabetic Mellitus (T2DM) is the most common systemic and endocrine disease in humans, and diabetic nephropathy is one of the most serious complications of this disorder. The polymorphisms in the apolipoprotein A5 (ApoA5) gene are strongly related to hypertriglyceridemia and are considered a predisposing factor for diabetic nephropathy. The current study proposed to examine the association of APOA5-S19W polymorphism with serum lipids levels in patients with type 2 diabetic nephropathy in Mazandaran province.

METHODS

This case-control study was designed to determine the association of APOA5-S19W polymorphism with plasma lipid profile in 161 T2DM patients with nephropathy (DN+), without nephropathy (DN-), and in 58 healthy individuals. Lipid profile values were measured using Pars Azmoun commercial kits. S19W variant, one of the polymorphisms of the APOA5 gene, was determined by PCR-restriction fragment length polymorphism (PCR-RFLP) and Taq1 restriction enzyme.

RESULTS

In comparison between the three groups, DN+ had a higher mean TG than DN- and the control group (p<0.001). The incidence of the G allele in DN+ was not significant compared to groups of DN-. Comparing the relationship between the mean of biochemical variables with CC and CG genotypes showed that the mean level of TG in people with CC genotype was increased compared to people with CG genotype in diabetic patients. However, this increase was not significant (p=0.19).

CONCLUSIONS

There was no association between SNP APOA5 S19W and serum lipids in diabetic patients with and without nephropathy.