Metformin reverses prostate cancer resistance to enzalutamide by targeting TGF-β1/STAT3 axis-regulated EMT

Immune Modulation During Treatment with Enzalutamide Alone or with Radium-223 in Patients with Castration Resistant Prostate Cancer

INTRODUCTION

Prostate cancer has been generally resistant to immunotherapy approaches. Radiation can be immunostimulatory, but the extent to which standard prostate cancer treatments induce immune activation has not been well described. The bone-targeted radiopharmaceutical Radium223 (Ra223) has been proposed to enrich immune function, but clinical studies have not fully delineated whether this is true, or by what mechanisms. Enzalutamide has been shown to increase PD-L1 expression on dendritic cells, which could impact immune activation, though the extent to which this is associated with other evidence of immune activation remains uncertain, and combination strategies remain of interest. We performed a randomized phase II trial to evaluate whether Radium223 (Ra223) added to enzalutamide would induce greater immune activation and clinical responses compared to enzalutamide alone in men with metastatic castration-resistant prostate cancer (mCRPC).

METHODS

Eligible patients were randomized 2:1 to Arm A (enzalutamide 160 mg PO daily + Ra223 55 kBq/kg IV q4 weeks × 6 doses) or Arm B (enzalutamide 160 mg PO daily). Blood was collected at treatment start and during treatment to measure soluble immune checkpoint biomarkers (BTLA, TIM3, HVEM, GITR, LAG3, PD-1, CTLA-4, PD-L1, PD-L2, ICOS). Immunophenotyping by mass cytometry time of flight (CyTOF) was performed to measure peripheral blood mononuclear cell populations before and after treatment. CyTOF was used to determine changes in circulating immune cell population subsets before and after treatment. Biopsies were performed of an active bone metastatic lesion prior to study treatment and after at least 3 months. IHC was subsequently performed to examine changes in immune cell population subsets before and after treatment, and changes in pSTAT3 levels.

RESULTS

In total, 30 patients were enrolled, with median age 68. The median duration of follow up was 36 months. PSA responses, PFS, and OS were not significantly different between the two arms; however, the study was not powered for clinical endpoints. Peripheral blood and bone biopsy specimens were analyzed for immune correlatives. Soluble receptor concentrations showed significantly increased expression of PDL-2 in the combination arm, but this was not seen on CyTOF. Otherwise, there were no significant differences in markers of immune activation/exhaustion or immune cell population subsets in the combination arm and enzalutamide monotherapy arm. IHC also did not show a significant difference in immune cell population subsets in bone biopsy specimens before and after treatment in both arms. However, treatment with the combination arm did show significantly increased levels of pSTAT3 (p = 0.04), which was not seen in the enzalutamide monotherapy arm.

CONCLUSIONS

Our study showed an overall lack of evidence for immune activation or cytokine induction with the combination, which does not make a strong case for combinatorial immunotherapy approaches. However, the combination did induce higher levels of pSTAT3, which has been implicated in radio-resistance. Therefore, the addition of a STAT3 inhibitor to the combination may be of interest to improve efficacy.

Dual-Responsive Immunomodulatory RNAi Nanoplatform for Effective Immune Checkpoint Blockade and Enhanced Cancer Immunotherapy

Immune checkpoint blockade (ICB) therapy has become the first-line treatment for cancer patients. However, the low response rate remains a clinical pain-point. Anti-hyperglycemic drug metformin has shown remarkable anticancer effect with the unique characteristic of modulating tumor immune microenvironment (TIME). Therefore, combining ICB with metformin could be a promising strategy for enhanced cancer immunotherapy, which however remains challenged due to the low bioavailability and severe adverse effects of metformin. This work herein designs an amphiphilic reduction-responsive metformin prodrug, which could complex small interfering RNA (siRNA) and then co-assemble with an endosomal pH-responsive PEGylated polymer to form a dual-responsive immunomodulatory RNAi nanoplatform. Using the orthotopic and metastatic breast cancer (BCa) tumor models, this work demonstrates that this RNAi nanoplatform could silence PD-L1 expression on BCa cells and suppress their proliferation via activating AMP-activated protein kinase (AMPK). Moreover, this AMPK activation could suppress the secretion of tumor-derived transforming growth factor β (TGF-β) and interleukin 6 (IL-6), which could enhance the maturation of dendritic cells (DCs) and activation of CD8+ T cells and impair the tumor infiltration of regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSCs), and tumor-associated macrophages (TAMs), ultimately achieving the goal of enhanced cancer immunotherapy and significant inhibition of BCa tumor growth.

Bone marrow adipocytes in cancer: Mechanisms, models, and therapeutic implications

Adipose tissue is the primary site of energy storage in the body and a key regulator of metabolism. However, different adipose depots exhibit distinct molecular and phenotypic characteristics that have yet to be fully unraveled. While initially considered inert, bone marrow adipocytes (BMAs) have been recognized as key regulators of bone homeostasis, and more recently bone pathologies, although many unknowns remain. In this review, we summarize the current knowledge on BMAs, focusing on their distinct characteristics, functional significance in bone physiology and metabolism, as well as their emerging role in cancer pathogenesis. We present and discuss the current methodologies for investigating BMA-cancer interactions, encompassing both in vitro 3D culture systems and in vivo models, and their limitations in accurately replicating the phenotypes and biological processes of the human species. We highlight the imperative for advancing towards humanized models to better mimic the complexities of human physiology and disease progression. Finally, therapeutic strategies targeting metabolism or BMA-secreted factors, such as anti-cholesterol drugs, hold considerable promise in cancer treatment. We present the synergistic avenue of combining conventional cancer therapies with agents targeting adipocyte signaling to amplify treatment efficacy. Developing preclinical models that more faithfully replicate human pathological and physiological processes will lead to more accurate mechanistic understanding of the role of BMAs in bone metastasis and lead to more relevant preclinical drug screening.

Metformin as an immunomodulatory agent in enhancing head and neck squamous cell carcinoma therapies

Head and neck squamous cell carcinoma (HNSCC) remains a significant clinical challenge due to its aggressive behavior and poor prognosis, making the development of novel therapeutics with enhanced efficacy and minimal side effects critical. Metformin, a widely used antidiabetic agent, has recently emerged as a potential adjunctive therapy for HNSCC, exhibiting both direct anti-tumor and immunomodulatory effects. This review comprehensively explores the multifaceted role of metformin in shaping the tumor immune microenvironment within HNSCC. We emphasize its pivotal role in modulating immune cell populations and its potential for synergistic action with immunotherapeutic strategies. Furthermore, we address the current challenges associated with optimizing dosing regimens, identifying predictive biomarkers, and integrating metformin with immunotherapy. By dissecting these aspects, this review aims to pave the way for the development of personalized HNSCC treatment strategies that fully exploit the therapeutic potential of metformin.

Metformin in overcoming enzalutamide resistance in castration-resistant prostate cancer

Androgen deprivation is the standard treatment for patients with prostate cancer. However, the disease eventually progresses as castration-resistant prostate cancer (CRPC). Enzalutamide, an androgen receptor inhibitor, is a typical drug for treating CRPC and with continuous reliance on the drug, can lead to enzalutamide resistance. This highlights the necessity for developing novel therapeutic targets to combat the gain of resistance. Metformin has been recently investigated for its potential antitumorigenic effects in many cancer types. In this study, we used enzalutamide and metformin in combination to explore the possible rescued efficacy of enzalutamide in the treatment of enzalutamide-resistant CRPC. We first tested the effects of this combination treatment on cell viability, drug synergy, and cell proliferation in enzalutamide-resistant CRPC cell lines. After combination treatment, we observed a decrease in cell proliferation and viability as well as a synergistic effect of both enzalutamide and metformin in vitro. Following these results, we sought to explore how combination treatment affected mitochondrial fitness using mitochondrial stress test analysis and mitochondrial membrane potential shifts due to metformin's action in inhibiting complex I of oxidative phosphorylation. We employed 2 different strategies for in vivo testing using 22Rv1 and LuCaP35CR xenograft models. Finally, RNA sequencing revealed a potential link in the downregulation of rat sarcoma-mitogen-activated protein kinase signaling following combination treatment. SIGNIFICANCE STATEMENT: Increasing evidence suggests that oxidative phosphorylation might play a critical role in the development of resistance to cancer therapy. This study showed that targeting oxidative phosphorylation with metformin can enhance the efficacy of enzalutamide in castration-resistant prostate cancer in vitro.

Impact of cell plasticity on prostate tumor heterogeneity and therapeutic response

Epithelial-mesenchymal transition (EMT) is a dynamic process of lineage plasticity in which epithelial cancer cells acquire mesenchymal traits, enabling them to metastasize to distant organs. This review explores the current understanding of how lineage plasticity and phenotypic reprogramming drive prostate cancer progression to lethal stages, contribute to therapeutic resistance, and highlight strategies to overcome the EMT phenotype within the prostate tumor microenvironment (TME). Emerging evidence reveals that prostate tumor cells can undergo lineage switching, adopting alternative growth pathways in response to anti-androgen therapies and taxane-based chemotherapy. These adaptive mechanisms support tumor survival and growth, underscoring the need for deeper insights into the processes driving prostate cancer differentiation, including neuroendocrine differentiation and lineage plasticity. A comprehensive understanding of these mechanisms will pave the way for innovative therapeutic strategies. Effectively targeting prostate cancer cells with heightened plasticity and therapeutic vulnerability holds promise for overcoming treatment resistance and preventing tumor recurrence. Such advancements are critical for developing effective approaches to prostate cancer treatment and improving patient survival outcomes.

Pan-cancer analysis of STAT3 indicates its potential prognostic value and correlation with immune cell infiltration in prostate cancer

BACKGROUND

Targeting the STAT3 signaling pathway is a promising therapeutic approach for cancer patients. However, the association between STAT3 expression, the tumor immune microenvironment, and genetic variation remains unclear across human cancers, especially prostate cancer.

METHODS

We used R software and other tools to analyze pan-cancer and mutation data from publicly available databases statistically. A comprehensive investigation was performed to assess the genetic heterogeneity and clinical relevance of STAT3 in various malignancies, with a specific focus on its role in the immune landscape and prognostic significance in prostate cancer. The findings were validated through immunohistochemistry (IHC) and multiplex immunofluorescence (mIF).

RESULTS

STAT3 expression is abnormal in the majority of cancer tissues, which is strongly correlated with these patients' prognosis. Eight measures of tumor heterogeneity and six measures of tumor stemness of multiple tumor types showed a strong correlation with STAT3 expression. Furthermore, in individuals with prostate cancer, STAT3 expression indicated the degree of immune cell infiltration and the advancement of the disease. IHC analysis revealed that STAT3 was down-regulated in prostate tumor tissues, while mIF analysis demonstrated that STAT3 signaling (p-STAT3) was extensively active in tumor tissues and positive lymph node tissues.

CONCLUSION

STAT3 may serve as a valuable prognostic biomarker and therapeutic target across various cancers, with particular relevance to prostate cancer.

Establishing a model predicting Gleason grade group upgrading in prostate cancer

Background

Gleason grade group (GG) upgrading is associated with increased biochemical recurrence (BCR), local progression, and decreased cancer-specific survival (CSS) in prostate cancer (PCa). However, descriptions of the risk factors of GG upgrading are scarce. The objective of this study was to identify risk factors and establish a model to predict GG upgrading.

Methods

There were 361 patients with PCa who underwent radical prostatectomy between May 2011 and February 2022 enrolled. Univariate and multivariate logistic regression analyses were identified and nomogram further narrowed down the contributing factors in GG upgrading. The correction curve and decision curve were used to assess the model.

Results

In the overall cohort, 141 patients had GG upgrading. But the subgroup cohort (GG ≤2) showed that 68 patients had GG upgrading. Multivariate logistic regression analysis showed that in the overall cohort, total prostate-specific antigen (tPSA) ≥10 ng/mL, systemic immune-inflammation index (SII) >379.50, neutrophil-lymphocyte ratio (NLR) >2.13, the GG of biopsy ≥3, the number of positive cores >3 were independent risk factors in GG upgrading. In the cohort of biopsy GG ≤2, multivariate logistic regression showed that the tPSA ≥10 ng/mL, SII >379.50 and the number of positive cores >3 were independent risk factors in GG upgrading. A novel model predicting GG upgrading was established based on these three parameters. The area under the curve (AUC) of the prediction model was 0.759. The C-index of the nomogram was 0.768. The calibration curves of the model showed good predictive performance. Clinical decision curves indicated clinical benefit in the interval of 20% to 90% of threshold probability and good clinical utility.

Conclusions

Combined levels of tPSA, SII and the positive biopsy cores distinguish patients with high-risk GG upgrading in the group of biopsy GG ≤2 and are helpful in the decision of treatment plans.

Metformin: A Dual-Role Player in Cancer Treatment and Prevention

Cancer continues to pose a significant global health challenge, as evidenced by the increasing incidence rates and high mortality rates, despite the advancements made in chemotherapy. The emergence of chemoresistance further complicates the effectiveness of treatment. However, there is growing interest in the potential of metformin, a commonly prescribed drug for type 2 diabetes mellitus (T2DM), as an adjuvant chemotherapy agent in cancer treatment. Although the precise mechanism of action of metformin in cancer therapy is not fully understood, it has been found to have pleiotropic effects, including the modulation of metabolic pathways, reduction in inflammation, and the regulation of cellular proliferation. This comprehensive review examines the anticancer properties of metformin, drawing insights from various studies conducted in vitro and in vivo, as well as from clinical trials and observational research. This review discusses the mechanisms of action involving both insulin-dependent and independent pathways, shedding light on the potential of metformin as a therapeutic agent for different types of cancer. Despite promising findings, there are challenges that need to be addressed, such as conflicting outcomes in clinical trials, considerations regarding dosing, and the development of resistance. These challenges highlight the importance of further research to fully harness the therapeutic potential of metformin in cancer treatment. The aims of this review are to provide a contemporary understanding of the role of metformin in cancer therapy and identify areas for future exploration in the pursuit of effective anticancer strategies.

Molecular panorama of therapy resistance in prostate cancer: a pre-clinical and bioinformatics analysis for clinical translation

Prostate cancer (PCa) is a malignant disorder of prostate gland being asymptomatic in early stages and high metastatic potential in advanced stages. The chemotherapy and surgical resection have provided favourable prognosis of PCa patients, but advanced and aggressive forms of PCa including CRPC and AVPC lack response to therapy properly, and therefore, prognosis of patients is deteriorated. At the advanced stages, PCa cells do not respond to chemotherapy and radiotherapy in a satisfactory level, and therefore, therapy resistance is emerged. Molecular profile analysis of PCa cells reveals the apoptosis suppression, pro-survival autophagy induction, and EMT induction as factors in escalating malignant of cancer cells and development of therapy resistance. The dysregulation in molecular profile of PCa including upregulation of STAT3 and PI3K/Akt, downregulation of STAT3, and aberrant expression of non-coding RNAs are determining factor for response of cancer cells to chemotherapy. Because of prevalence of drug resistance in PCa, combination therapy including co-utilization of anti-cancer drugs and nanotherapeutic approaches has been suggested in PCa therapy. As a result of increase in DNA damage repair, PCa cells induce radioresistance and RelB overexpression prevents irradiation-mediated cell death. Similar to chemotherapy, nanomaterials are promising for promoting radiosensitivity through delivery of cargo, improving accumulation in PCa cells, and targeting survival-related pathways. In respect to emergence of immunotherapy as a new tool in PCa suppression, tumour cells are able to increase PD-L1 expression and inactivate NK cells in mediating immune evasion. The bioinformatics analysis for evaluation of drug resistance-related genes has been performed.

Expression profiling of extramedullary acute myeloid leukemia suggests involvement of epithelial-mesenchymal transition pathways

Extramedullary (EM) colonization is a rare complication of acute myeloid leukemia (AML), occurring in about 10% of patients, but the processes underlying tissue invasion are not entirely characterized. Through the application of RNAseq technology, we examined the transcriptome profile of 13 AMLs, 9 of whom presented an EM localization. Our analysis revealed significant deregulation within the extracellular matrix (ECM)-receptor interaction and focal-adhesion pathways, specifically in the EM sites. The transcription factor TWIST1, which is known to impact on cancer invasion by dysregulating epithelial-mesenchymal-transition (EMT) processes, was significantly upregulated in EM-AML. To test the functional impact of TWIST1 overexpression, we treated OCI-AML3s with TWIST1-siRNA or metformin, a drug known to inhibit tumor progression in cancer models. After 48 h, we showed downregulation of TWIST1, and of the EMT-related genes FN1 and SNAI2. This was associated with significant impairment of migration and invasion processes by Boyden chamber assays. Our study shed light on the molecular mechanisms associated with EM tissue invasion in AML, and on the ability of metformin to interfere with key players of this process. TWIST1 may configure as candidate marker of EM-AML progression, and inhibition of EMT-pathways may represent an innovative therapeutic intervention to prevent or treat this complication.

[Research Progress on the Combination Therapy of EGFR-TKIs and Metformin in Acquired Resistance to EGFR-TKIs in Non-small Cell Lung Cancer]

Epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) targeting EGFR are effective in EGFR mutation-positive non-small cell lung cancer (NSCLC) patients, but drug resistance is inevitable. With the application and expansion of individualized and combined therapy, more and more studies have shown that combined administration of Metformin effectively solves the problem of acquired drug resistance to EGFR-TKIs in clinical treatment and prolongs the survival of patients with NSCLC. EGFR-TKIs combined with Metformin is expected to be the treatment method of choice for NSCLC patients with EGFR-TKIs resistance. This paper intends to summarize the research progress of EGFR-TKIs combined with Metformin in the treatment of EGFR-TKIs acquired resistance in NSCLC, in order to provide a new idea for the treatment of NSCLC patients with acquired resistance to EGFR-TKIs.
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Pharmacophore mapping approach to find anti-cancer phytochemicals with metformin-like activities against transforming growth factor (TGF)-beta receptor I kinase: An in silico study

The most frequently prescribed first-line treatment for type II diabetes mellitus is metformin. Recent reports asserted that this diabetes medication can also shield users from cancer. Metformin induces cell cycle arrest in cancer cells. However, the exact mechanism by which this occurs in the cancer system is yet to be elucidated. Here, we investigated the impact of metformin on cell cycle arrest in cancer cells utilizing transforming growth factor (TGF)-beta pathway. TGF-ß pathway has significant effect on cell progression and growth. In order to gain an insight on the underlying molecular mechanism of metformin's effect on TGF beta receptor 1 kinase, molecular docking was performed. Metformin was predicted to interact with transforming growth factor (TGF)-beta receptor I kinase based on molecular docking and molecular dynamics simulations. Furthermore, pharmacophore was generated for metformin-TGF-ßR1 complex to hunt for novel compounds having similar pharmacophore as metformin with enhanced anti-cancer potentials. Virtual screening with 29,000 natural compounds from NPASS database was conducted separately for the generated pharmacophores in Ligandscout® software. Pharmacophore mapping showed 60 lead compounds for metformin-TGF-ßR1 complex. Molecular docking, molecular dynamics simulation for 100 ns and ADMET analysis were performed on these compounds. Compounds with CID 72473, 10316977 and 45140078 showed promising binding affinities and formed stable complexes during dynamics simulation with aforementioned protein and thus have potentiality to be developed into anti-cancer medicaments.

Targeting the STAT3 oncogenic pathway: Cancer immunotherapy and drug repurposing

Immune effector cells in the microenvironment tend to be depleted or remodeled, unable to perform normal functions, and even promote the malignant characterization of tumors, resulting in the formation of immunosuppressive microenvironments. The strategy of reversing immunosuppressive microenvironment has been widely used to enhance the tumor immunotherapy effect. Signal transducer and activator of transcription 3 (STAT3) was found to be a crucial regulator of immunosuppressive microenvironment formation and activation as well as a factor, stimulating tumor cell proliferation, survival, invasiveness and metastasis. Therefore, regulating the immune microenvironment by targeting the STAT3 oncogenic pathway might be a new cancer therapy strategy. This review discusses the pleiotropic effects of STAT3 on immune cell populations that are critical for tumorigenesis, and introduces the novel strategies targeting STAT3 oncogenic pathway for cancer immunotherapy. Lastly, we summarize the conventional drugs used in new STAT3-targeting anti-tumor applications.

Analysis of differential membrane proteins related to matrix stiffness-mediated metformin resistance in hepatocellular carcinoma cells

BACKGROUND

Our previous work shows that increased matrix stiffness not only alters malignant characteristics of hepatocellular carcinoma (HCC) cells, but also attenuates metformin efficacy in treating HCC cells. Here, we identified differential membrane proteins related to matrix stiffness-mediated metformin resistance for better understand therapeutic resistance of metformin in HCC.

METHODS

Differential membrane proteins in HCC cells grown on different stiffness substrates before and after metformin intervention were screened and identified using isobaric tags for relative and absolute quantification (iTRAQ) labeling coupled with the liquid chromatography-tandem mass spectrometry (LC-MS/MS), then bioinformatic analysis were applied to determine candidate membrane protein and their possible signaling pathway.

RESULTS

A total of 5159 proteins were identified and 354 differential membrane proteins and membrane associated proteins, which might be associated with matrix stiffness-mediated metformin resistance were discovered. Then 94 candidate membrane proteins including 21 up-regulated protein molecules and 73 down-regulated protein molecules were further obtained. Some of them such as Annexin A2 (ANXA2), Filamin-A (FLNA), Moesin (MSN), Myosin-9 (MYH9), Elongation factor 2 (eEF2), and Tax1 binding Protein 3 (TAX1BP3) were selected for further validation. Their expressions were all downregulated in HCC cells grown on different stiffness substrates after metformin intervention. More importantly, the degree of decrease was obviously weakened on the higher stiffness substrate compared with that on the lower stiffness substrate, indicating that these candidate membrane proteins might contribute to matrix stiffness-mediated metformin resistance in HCC.

CONCLUSIONS

There was an obvious change in membrane proteins in matrix stiffness-mediated metformin resistance in HCC cells. Six candidate membrane proteins may reflect the response of HCC cells under high stiffness stimulation to metformin intervention, which deserve to be investigated in the future.

Fulvestrant increases the susceptibility of enzalutamide-resistant prostate cancer cells to NK-mediated lysis

BACKGROUND

Enzalutamide, a next-generation antiandrogen agent, is approved for the treatment of metastatic castration-resistant prostate cancer (CRPC). While enzalutamide has been shown to improve time to progression and extend overall survival in men with CRPC, the majority of patients ultimately develop resistance to treatment. Immunotherapy approaches have shown limited clinical benefit in this patient population; understanding resistance mechanisms could help develop novel and more effective treatments for CRPC. One of the mechanisms involved in tumor resistance to various therapeutics is tumor phenotypic plasticity, whereby carcinoma cells acquire mesenchymal features with or without the loss of classical epithelial characteristics. This work investigated a potential link between enzalutamide resistance, tumor phenotypic plasticity, and resistance to immune-mediated lysis in prostate cancer.

METHODS

Models of prostate cancer resistant to enzalutamide were established by long-term exposure of human prostate cancer cell lines to the drug in culture. Tumor cells were evaluated for phenotypic features in vitro and in vivo, as well as for sensitivity to immune effector cell-mediated cytotoxicity.

RESULTS

Resistance to enzalutamide was associated with gain of mesenchymal tumor features, upregulation of estrogen receptor expression, and significantly reduced tumor susceptibility to natural killer (NK)-mediated lysis, an effect that was associated with decreased tumor/NK cell conjugate formation with enzalutamide-resistant cells. Fulvestrant, a selective estrogen receptor degrader, restored the formation of target/NK cell conjugates and increased susceptibility to NK cell lysis in vitro. In vivo, fulvestrant demonstrated antitumor activity against enzalutamide-resistant cells, an effect that was associated with activation of NK cells.

CONCLUSION

NK cells are emerging as a promising therapeutic approach in prostate cancer. Modifying tumor plasticity via blockade of estrogen receptor with fulvestrant may offer an opportunity for immune intervention via NK cell-based approaches in enzalutamide-resistant CRPC.

Genetic profiling of hormone-sensitive and castration-resistant prostate cancers and identification of genetic mutations prone to castration-resistant prostate cancer

BACKGROUND

Genetic profiling of patients with prostate cancer could potentially identify mutations prone to castration-resistant prostate cancer (CRPC). Here, we aimed to identify the differences in genetic profiles of patients with hormone-sensitive prostate cancer (HSPC) and CRPC and stratify HSPC patients to identify mutations associated with CRPC progression.

METHODS

A total of 103 samples were collected, including 62 DNA samples from the tumor tissues of 59 HSPC patients and 41 cell-free DNA (cfDNA) samples from prostate cancer patients at different cancer stages. Targeted sequence was conducted on both the tissue DNA and cfDNA. The associations between mutations and clinical outcomes (CRPC-free time) were analyzed using χ2 test, logistic regression analysis, Kaplan-Meier analysis, and Cox regression analysis.

RESULTS

By comparing to that of cfDNA sequencing, the results from DNA sequencing of 1-needle (80%) and mixed 12-needle (77.8%) biopsies are highly comparable. FOXA1 (30.5%), CDK12 (23.7%), and TP53 (22.0%) were the top 3 most frequently mutated genes in HSPC patients; 50.8% (30/59) and 44.1% (26/59) HSPC patients had mutations in DDR and HRR pathway, respectively. Mutations in AR and APC as well as the members involved in the regulation of stem cell pluripotency and EMT pathway were often observed in CRPC samples. We established a panel of four genetic mutations (MSH2, CDK12, TP53, and RB1) to predict the risk of CRPC early progression with concordance index = 0.609 and the area under curve of the ROC curve as 0.838.

CONCLUSIONS

In this study, we demonstrated that the cfDNA can be used in genetic profiling in prostate cancer and our newly established panel is capable of predicting which mHSPC patient has a high risk of early CRPC progression.

Overcoming Acquired Drug Resistance to Cancer Therapies through Targeted STAT3 Inhibition

Anti-neoplastic agents for cancer treatment utilize many different mechanisms of action and, when combined, can result in potent inhibition of cancer growth. Combination therapies can result in long-term, durable remission or even cure; however, too many times, these anti-neoplastic agents lose their efficacy due to the development of acquired drug resistance (ADR). In this review, we evaluate the scientific and medical literature that elucidate STAT3-mediated mechanisms of resistance to cancer therapeutics. Herein, we have found that at least 24 different anti-neoplastic agents-standard toxic chemotherapeutic agents, targeted kinase inhibitors, anti-hormonal agents, and monoclonal antibodies-that utilize the STAT3 signaling pathway as one mechanism of developing therapeutic resistance. Targeting STAT3, in combination with existing anti-neoplastic agents, may prove to be a successful therapeutic strategy to either prevent or even overcome ADR to standard and novel cancer therapies.

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

The categorization of cancers demonstrates that prostate cancer is the most common malignancy in men and it causes high death annually. Prostate cancer patients are diagnosed mainly via biomarkers such as PSA test and patients show poor prognosis. Prostate cancer cells rapidly diffuse into different parts of body and their metastasis is also a reason for death. Current therapies for prostate cancer patients include chemotherapy, surgery and radiotherapy as well as targeted therapy. The progression of prostate cancer cells is regulated by different factors that STAT3 signaling is among them. Growth factors and cytokines such as IL-6 can induce STAT3 signaling and it shows carcinogenic impact. Activation of STAT3 signaling occurs in prostate cancer and it promotes malignant behavior of tumor cells. Induction of STAT3 signaling increases glycolysis and proliferation of prostate cancer cells and prevents apoptosis. Furthermore, STAT3 signaling induces EMT mechanism in increasing cancer metastasis. Activation of STAT3 signaling stimulates drug resistance and the limitation of current works is lack of experiment related to role of STAT3 signaling in radio-resistance in prostate tumor. Calcitriol, capsazepine and β-elemonic are among the compounds capable of targeting STAT3 signaling and its inhibition in prostate cancer therapy. In addition to natural products, small molecules targeting STAT3 signaling have been developed in prostate cancer therapy.

Systematic review of antitumour efficacy and mechanism of metformin activity in prostate cancer models

Metformin, the first line pharmacotherapy for type 2 diabetes has demonstrated favourable effects in prostate cancer (PCa) across a range of studies evaluating PCa patient outcomes amongst metformin users. However, a lack of rigorously conducted prospective studies has stalled clinical use in this setting. Despite multiple studies evaluating the mechanisms underpinning antitumour effects of metformin in PCa, to date, no reviews have compared these findings. This systematic review and meta-analysis consolidates the mechanisms accounting for the antitumour effect of metformin in PCa and evaluates the antitumour efficacy of metformin in preclinical PCa studies. Data were obtained through Medline and EMBASE, extracted by two independent assessors. Risk of bias was assessed using the TOXR tool. Meta-analysis compared in vivo reductions of PCa tumour volume with metformin. In total, 447 articles were identified with 80 duplicates, and 261 articles excluded based on eligibility criteria. The remaining 106 articles were assessed and 71 excluded, with 35 articles included for systematic review, and eight included for meta-analysis. The mechanisms of action of metformin regarding tumour growth, viability, migration, invasion, cell metabolism, and activation of signalling cascades are individually discussed. The mechanisms by which metformin inhibits PCa cell growth are multimodal. Metformin regulates expression of multiple proteins/genes to inhibit cellular proliferation, cell cycle progression, and cellular invasion and migration. Published in vivo studies also conclusively demonstrate that metformin inhibits PCa growth. This highlights the potential of metformin to be repurposed as an anticancer agent, warranting further investigation of metformin in the setting of PCa.

Synergic Effect of Metformin and Everolimus on Mitochondrial Dynamics of Renal Cell Carcinoma

Renal cell carcinoma (RCC) frequently recurs or metastasizes after surgical resection. Everolimus, an mTOR inhibitor, is used as a second-line treatment, but the response of RCC to everolimus is insufficient. Metformin is an antidiabetic drug; recent reports have indicated its anti-cancer effects in various cancers, and it is known to have synergistic effects with other drugs. We investigated the possibility of coadministering everolimus and metformin as an effective treatment for RCC. RCC cells treated with a combination of the two drugs showed significantly inhibited cell viability, cell migration, and invasion, and increased apoptosis compared to those treated with each drug alone. An anti-cancer synergistic effect was also confirmed in the xenograft model. Transcriptome analysis for identifying the underlying mechanism of the combined treatment showed the downregulation of mitochondrial fusion genes and upregulation of mitochondrial fission genes by the combination treatment. Changes in mitochondrial dynamics following the combination treatment were observed using LysoTracker, LysoSensor, and JC-1 staining. In conclusion, the combination of everolimus and metformin inhibited RCC growth by disrupting mitochondrial dynamics. Therefore, we suggest that a treatment combining metformin and everolimus disrupts mitochondrial dynamics in RCC, and may be a novel strategy for RCC treatment.

Effects of metformin and statins on outcomes in men with castration-resistant metastatic prostate cancer: Secondary analysis of COU-AA-301 and COU-AA-302

BACKGROUND

The associations of metformin and statins with overall survival (OS) and prostate specific antigen response rate (PSA-RR) in trials in metastatic castration-resistant prostate cancer remain unclear.

OBJECTIVE

To determine whether metformin or statins ± abiraterone acetate plus prednisone/prednisolone (AAP) influence OS and PSA-RR.

DESIGN, SETTING AND PARTICIPANT

COU-AA-301 and COU-AA-302 patients were stratified by metformin and statin use. Cox proportional hazards models were used to estimate hazards ratio (HR) stratified by concomitant medications, and a random effects model was used to pool HR. We compared PSA-RR using Chi χ² test.

RESULTS

In COU-AA-301-AAP, metformin was associated with improved PSA-RR (41.1% versus 28.6%) but not prolonged OS. In COU-AA-301-placebo-P, there was no association between metformin and prolonged OS or PSA-RR. In COU-AA-302-AAP, metformin was associated with prolonged OS (adjHR 0.69, 95% CI 0.48-0.98) and improved PSA-RR (72.7% versus 60.0%). In COU-AA-302-P, metformin was associated with prolonged OS (adjHR 0.66, 95% CI 0.47-0.93). In pooled analysis, OS was prolonged among those treated with metformin (pooled HR 0.77, 95% CI 0.62-0.95).In COU-AA-301-AAP, statins were associated with an improved OS (adjHR 0.76, 95% CI 0.62-0.93), while there was no difference in COU-AA-301-P. There was no association with statins and OS in either COU-AA-302 groups. When pooling HR, OS was prolonged among those treated with statins (pooled HR 0.78, 95% CI 0.68-0.88).

CONCLUSION

Within the limitations of post-hoc sub-analyses, metformin and statins are associated with a prolonged OS and increased PSA-RR, particularly in combination with AAP.

Statin and metformin use and outcomes in patients with castration-resistant prostate cancer treated with enzalutamide: A meta-analysis of AFFIRM, PREVAIL and PROSPER

BACKGROUND

Statins and metformin are commonly prescribed for patients, including those with prostate cancer. Preclinical and epidemiologic studies of each agent have suggested anti-cancer properties.

METHODS

Patient data from three randomised, double-blind, placebo-controlled, phase III studies evaluating enzalutamide (AFFIRM, PREVAIL and PROSPER) in patients with castration-resistant prostate cancer were included in this analysis. This post hoc, retrospective study examined the association of statin and metformin on radiographic progression-free survival (rPFS), metastasis-free survival (MFS), toxicity and overall survival (OS). After adjusting for available clinical prognostic variables, multivariate analyses were performed on pooled data from AFFIRM and PREVAIL, all three trials pooled, and each trial individually, to assess differential efficacy in these end-points associated with the baseline use of these medications.

RESULTS

In the multivariate analysis of the individual trials, OS and rPFS/MFS were not significantly influenced by statin or metformin use in AFFIRM or PROSPER. However, in PREVAIL, OS was significantly influenced by statin (hazard ratio [HR] 0.72; 95% confidence interval [CI] 0.59-0.89) and rPFS was significantly influenced by metformin (HR, 0.48; 95% CI 0.34-0.70). In pooled analyses, improved OS was significantly associated with statin use but not metformin use for AFFIRM+PREVAIL trials (HR 0.83; 95% CI 0.72-0.96) and AFFIRM+PREVAIL+PROSPER (HR 0.75; 95% CI 0.66-0.85).

CONCLUSIONS

The association between statin or metformin use and rPFS, MFS and OS was inconsistent across three trials. Analyses of all three trials pooled and AFFIRM+PREVAIL pooled revealed that statin but not metformin use was significantly associated with a reduced risk of death in enzalutamide-treated patients. Additional prospective, controlled studies are warranted.

CLINICAL TRIAL REGISTRATION

AFFIRM (NCT00974311), PREVAIL (NCT01212991) and PROSPER (NCT02003924).

Selective estrogen receptor modulators contribute to prostate cancer treatment by regulating the tumor immune microenvironment

Prostate cancer (PC) has previously been established as a cold tumor and develops in an inert immunosuppressive environment. Current research focuses on altering the immune microenvironment of PC from cold to hot; thus, in the present review, the diverse roles of estrogen and estrogen receptor (ER) signaling was examined in the tumor cell and tumor immune microenvironment (TIM). We hypothesized that ERα promotes PC progression and ERβ impedes epithelial-mesenchymal transition in PC cells, while in the TIM, ERβ mediates the immunosuppressive environment, and low levels of ERα is associated with disease development. Selective estrogen receptor modulators (SERMs) or selective ER degraders play diverse roles in the regulation of ER isoforms. Patients with PC may benefit from the use of SERMs, including raloxifene, in combination with anti-PD1/PD-L1 checkpoint immunotherapy, or TGF-β or Wnt antagonists. The present review demonstrated that immunotherapy-based strategies combined with SERMs may be an option for the future of PC-targeting therapy.

Metformin and Cancer Hallmarks: Molecular Mechanisms in Thyroid, Prostate and Head and Neck Cancer Models

Metformin is the most used drug for type 2 diabetes (T2DM). Its antitumor activity has been described by clinical studies showing reduced risk of cancer development in T2DM patients, as well as management of T2DM compared with those receiving other glucose-lowering drugs. Metformin has a plethora of molecular actions in cancer cells. This review focused on in vitro data on the action mechanisms of metformin on thyroid, prostate and head and neck cancer. AMPK activation regulating specific downstream targets is a constant antineoplastic activity in different types of cancer; however, AMPK-independent mechanisms are also relevant. In vitro evidence makes it clear that depending on the type of tumor, metformin has different actions; its effects may be modulated by different cell conditions (for instance, presence of HPV infection), or it may regulate tissue-specific factors, such as the Na+/I- symporter (NIS) and androgen receptors. The hallmarks of cancer are a set of functional features acquired by the cell during malignant development. In vitro studies show that metformin regulates almost all the hallmarks of cancer. Interestingly, metformin is one of these therapeutic agents with the potential to synergize with other chemotherapeutic agents, with low cost, low side effects and high positive consequences. Some questions are still challenging: Are metformin in vitro data able to translate from bench to bedside? Does metformin affect drug resistance? Can metformin be used as a generic anticancer drug for all types of tumors? Which are the specific actions of metformin on the peculiarities of each type of cancer? Several clinical trials are in progress or have been concluded for repurposing metformin as an anticancer drug. The continuous efforts in the field and future in vitro studies will be essential to corroborate clinical trials results and to elucidate the raised questions.

Transforming growth factor-beta (TGF-β) in prostate cancer: A dual function mediator?

Transforming growth factor-beta (TGF-β) is a member of a family of secreted cytokines with vital biological functions in cells. The abnormal expression of TGF-β signaling is a common finding in pathological conditions, particularly cancer. Prostate cancer (PCa) is one of the leading causes of death among men. Several genetic and epigenetic alterations can result in PCa development, and govern its progression. The present review attempts to shed some light on the role of TGF-β signaling in PCa. TGF-β signaling can either stimulate or inhibit proliferation and viability of PCa cells, depending on the context. The metastasis of PCa cells is increased by TGF-β signaling via induction of EMT and MMPs. Furthermore, TGF-β signaling can induce drug resistance of PCa cells, and can lead to immune evasion via reducing the anti-tumor activity of cytotoxic T cells and stimulating regulatory T cells. Upstream mediators such as microRNAs and lncRNAs, can regulate TGF-β signaling in PCa. Furthermore, some pharmacological compounds such as thymoquinone and valproic acid can suppress TGF-β signaling for PCa therapy. TGF-β over-expression is associated with poor prognosis in PCa patients. Furthermore, TGF-β up-regulation before prostatectomy is associated with recurrence of PCa. Overall, current review discusses role of TGF-β signaling in proliferation, metastasis and therapy response of PCa cells and in order to improve knowledge towards its regulation, upstream mediators of TGF-β such as non-coding RNAs are described. Finally, TGF-β regulation and its clinical application are discussed.

Influence of Systemic Therapy on the Expression and Activity of Selected STAT Proteins in Prostate Cancer Tissue

Signal Transducer and Activator of Transcription (STAT) proteins have been identified as drivers of prostate cancer (PCa) progression and development of aggressive castration-resistant phenotypes. In particular, STAT3, 5, and 6 have been linked to resistance to androgen receptor inhibition and metastasis in in vitro and in vivo models. This descriptive study aimed to validate these preclinical data in tissue obtained from patients with PCa before and while under androgen-deprivation therapy. Therefore, STAT3, 5, and 6 expressions and activity were assessed by immunohistochemistry. The data revealed that STAT3 and 5 changed in PCa. However, there was no relationship between expression and survival. Moreover, due to the heterogeneous nature of PCa, the preclinical results could not be transferred congruently to the patient’s material. A pilot study with a longitudinal patient cohort could also show this heterogeneous influence of systemic therapy on STAT3, 5, and 6 expressions and activity. Even if the main mechanisms were validated, these data demonstrate the urge for better patient-near preclinical models. Therefore, these data reflect the need for investigations of STAT proteins in a longitudinal patient cohort to identify factors responsible for the diverse influence of system therapy on STAT expression.

TGF-β Signaling and Resistance to Cancer Therapy

The transforming growth factor β (TGF-β) pathway, which is well studied for its ability to inhibit cell proliferation in early stages of tumorigenesis while promoting epithelial-mesenchymal transition and invasion in advanced cancer, is considered to act as a double-edged sword in cancer. Multiple inhibitors have been developed to target TGF-β signaling, but results from clinical trials were inconsistent, suggesting that the functions of TGF-β in human cancers are not yet fully explored. Multiple drug resistance is a major challenge in cancer therapy; emerging evidence indicates that TGF-β signaling may be a key factor in cancer resistance to chemotherapy, targeted therapy and immunotherapy. Finally, combining anti-TGF-β therapy with other cancer therapy is an attractive venue to be explored for the treatment of therapy-resistant cancer.

Impact of STAT Proteins in Tumor Progress and Therapy Resistance in Advanced and Metastasized Prostate Cancer

Signal transducers and activators of transcription (STATs) are a family of transcription factors involved in several biological processes such as immune response, cell survival, and cell growth. However, they have also been implicated in the development and progression of several cancers, including prostate cancer (PCa). Although the members of the STAT protein family are structurally similar, they convey different functions in PCa. STAT1, STAT3, and STAT5 are associated with therapy resistance. STAT1 and STAT3 are involved in docetaxel resistance, while STAT3 and STAT5 are involved in antiandrogen resistance. Expression of STAT3 and STAT5 is increased in PCa metastases, and together with STAT6, they play a crucial role in PCa metastasis. Further, expression of STAT3, STAT5, and STAT6 was elevated in advanced and high-grade PCa. STAT2 and STAT4 are currently less researched in PCa. Since STATs are widely involved in PCa, they serve as potential therapeutic targets. Several inhibitors interfering with STATs signaling have been tested unsuccessfully in PCa clinical trials. This review focuses on the respective roles of the STAT family members in PCa, especially in metastatic disease and provides an overview of STAT-inhibitors evaluated in clinical trials.

ZNF507 affects TGF-β signaling via TGFBR1 and MAP3K8 activation in the progression of prostate cancer to an aggressive state

Background

The progression of prostate cancer (PC) to the highly aggressive metastatic castration-resistant prostate cancer (mCRPC) or neuroendocrine prostate cancer (NEPC) is a fatal condition and the underlying molecular mechanisms are poorly understood. Here, we identified the novel transcriptional factor ZNF507 as a key mediator in the progression of PC to an aggressive state.

Methods

We analyzed ZNF507 expression in the data from various human PC database and high-grade PC patient samples. By establishment of ZNF507 knockdown and overexpression human PC cell lines, we assessed in vitro PC phenotype changes including cell proliferation, survival, migration and invasion. By performing microarray with ZNF507 knockdown PC cells, we profiled the gene clusters affected by ZNF507 knockdown. Moreover, ZNF507 regulated key signal was evaluated by dual-luciferase reporter and chromatin immunoprecipitation (ChIP) assays. Finally, we performed xenograft and in vivo metastasis assay to confirm the effect of ZNF507 knockdown in PC cells.

Results

We found that ZNF507 expression was increased, particularly in the highly graded PC. ZNF507 was also found to be associated with metastatic PC of a high grade. Loss- or gain-of-function–based analysis revealed that ZNF507 promotes the growth, survival, proliferation, and metastatic properties of PC (e.g., epithelial-mesenchymal transition) by upregulating TGF-β signaling. Profiling of gene clusters affected by ZNF507 knockdown revealed that ZNF507 positively regulated the transcription of TGFBR1, MAP3K8, and FURIN, which in turn promoted the progression of PC to highly metastatic and aggressive state.

Conclusions

Our findings suggest that ZNF507 is a novel key regulator of TGF-β signaling in the progression of malignant PC and could be a promising target for studying the development of advanced metastatic PCs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02094-3.

Role of Calcium Homeostasis in Modulating EMT in Cancer

Calcium is essential for cells to perform numerous physiological processes. In cancer, the augmentation of calcium signaling supports the more proliferative and migratory cells, which is a characteristic of the epithelial-to-mesenchymal transition (EMT). By genetically and epigenetically modifying genes, channels, and entire signaling pathways, cancer cells have adapted to survive with an extreme imbalance of calcium that allows them to grow and metastasize in an abnormal manner. This cellular remodeling also allows for the evasion of immune surveillance and the development of drug resistance, which lead to poor prognosis in patients. Understanding the role calcium flux plays in driving the phenotypes associated with invasion, immune suppression, metastasis, and drug resistance remains critical for determining treatments to optimize clinical outcomes and future drug discovery.

Overexpression of CXCR7 is a Novel Indicator for Enzalutamide Resistance in Castration-Resistant Prostate Cancer Patients

Background

To evaluate whether the overexpression of chemokine receptor-7 (CXCR7) in prostatic tissues obtained from men with Castration-Resistant Prostate Cancer (CRPC) is associated with resistance to enzalutamide (Enza).

Methods

Based on the inclusion criteria of CRPC in EAU guidelines, all eligible patients treated in our hospital from January 2015 to December 2019 were included. Cases underwent radical prostatectomy, docetaxel-based chemotherapy, or new endocrine therapies (including Enza or abiraterone), and cases with severe cardiopulmonary disease or other malignant tumors were excluded. After immunohistochemical staining for CXCR7 expression in prostatic biopsy tissues, all enrolled cases were divided into two groups, namely, the CXCR7-positive group and the CXCR7-negative group. And then, PSA response to Enza treatment was recorded in detail and comparatively analyzed. In addition, the Cox proportional hazard modeling and the Kaplan-Meier analysis were used to determine PSA progression-free survival (PSAP-FS) and clinical or radiographic progression-free survival (CRP-FS) in this cohort.

Results

A total of 79 CRPC individuals were enrolled and evaluated in this study. Median follow-up durations were 24 months (range, 12-42) in the CXCR7-positive group (n = 47) and 28.5 months (range, 12-42) in the CXCR7-negative group (n = 32). The patients with lower CXCR7 expression showed much better PSA response to Enza treatment. There was 84.4% of CXCR7- cases showing decreasing PSA response, while there were 71.4% in the CXCR7/1+ group and 31.2% in the CXCR7/2+ group, respectively. All patients in the CXCR7/3+ group showed increasing PSA response to Enza treatment. And the percentage of patients whose PSA decreased over 50% is significantly higher in the CXCR7-negative group than in the CXCR7-positive group (68.8% vs. 8.5%, P < 0.001), and the percentage of patients whose PSA decreased over 90% is also remarkably higher in the CXCR7-negative group (43.8% vs. 0, P < 0.001). The Kaplan-Meier analysis demonstrated that the oncologic outcomes of CXCR7-negative patients were improved much significantly by Enza treatment in comparison with those of CXCR7-positive patients. Significantly increased median PSAP-FS (21 months vs. 6 months, P < 0.0001) and CRP-FS (27 months vs. 9 months, P < 0.0001) were obtained in the CXCR7-negative group. The further stratified analysis in all CXCR7-positive patients demonstrated that the patients with higher CXCR7 expression showed much worse outcome. The median time of PSAP-FS was 21 months in the CXCR7/1+ group, 9 months in the CXCR7/2+ group, and 6 months in the CXCR7/3+ group, while the median time of CRP-FS was 21 months in the CXCR7/1+ group, 12 months in the CXCR7/2+ group, and 6 months in the CXCR7/3+ group, respectively.

Conclusion

Overexpression of CXCR7 induced by an AR antagonist in CRPC patients displays much better treatment response to Enza. CXCR7 might be a novel therapeutic target gene for CRPC patients.

Construction of enzalutamide-resistant cell model of prostate cancer and preliminary screening of potential drug-resistant genes

Among many factors of causing castration-resistant prostate cancer (CRPC) progression, a growing number of evidences have shown androgen receptors play a critical role. Therefore, blocking androgen receptor remains a therapeutic goal of CRPC. However, resistance to androgen receptor inhibitors, for example, enzalutamide, limits therapeutic efficacy for many patients. In this study, to develop an enzalutamide-resistant cell model for molecular mechanism investigation of enzalutamide-resistance, we continuously treated C4-2B cells with multiplied concentrations of enzalutamide. The IC50 of resistant cells was identified as 14.7705 µM, and the resistance index was calculated as 12.4. In addition, we verified the resistance of resistant cells through experiments in vivo and found the genes in androgen receptor signaling pathway (androgen receptor, Jagged1, Notch1) and those in androgen receptor alternative signaling pathways behaved the opposite. For some of the former, their mRNA and protein expression reduced markedly while for the latter, for example, CXCR7, AKT, STAT3, FOXP3, they rose dramatically in the expression level of protein and mRNA. More importantly, the tumor volume, tumor wet weight, PSA and VEGF secretion level, positive staining rate of Ki67 nuclei in resistant strain heterogeneous tumor treated with enzalutamide were significantly higher than those of maternal cell heterogeneous tumor treated with enzalutamide, whereas no obvious difference was detected between resistant strain heterogeneous tumor treated with enzalutamide and those of the resistant strain treated with reference drug. Finally, we identified 654 differentially expression genes and 2 compounds (atracurium besilate, methotrexates) associated with the amelioration of enzalutamide-resistance. Overall, we successfully established an enzalutamide-resistance cell model and screened out some resistance genes and candidate small molecule drugs.

Biguanides drugs: Past success stories and promising future for drug discovery

Biguanides have attracted much attention a century ago and showed resurgent interest in recent years after a long period of dormancy. They constitute an important class of therapeutic agents suitable for the treatment of a wide spectrum of diseases. Therapeutic indications of biguanides include antidiabetic, antimalarial, antiviral, antiplaque, and bactericidal applications. This review presents an extensive overview of the biological activity of biguanides and different mechanisms of action of currently marketed biguanide-containing drugs, as well as their pharmacological properties when applicable. We highlight the recent developments in research on biguanide compounds, with a primary focus on studies on metformin in the field of oncology. We aim to provide a critical overview of all main bioactive biguanide compounds and discuss future perspectives for the design of new drugs based on the biguanide fragment.

Interplay of Epidermal Growth Factor Receptor and Signal Transducer and Activator of Transcription 3 in Prostate Cancer: Beyond Androgen Receptor Transactivation

Prostate cancer (PCa) is one of the most common cancers in the world and causes thousands of deaths every year. Conventional therapy for PCa includes surgery and androgen deprivation therapy (ADT). However, about 10-20% of all PCa cases relapse; there is also the further development of castration resistant adenocarcinoma (CRPC-Adeno) or neuroendocrine (NE) PCa (CRPC-NE). Due to their androgen-insensitive properties, both CRPC-Adeno and CRPC-NE have limited therapeutic options. Accordingly, this study reveals the inductive mechanisms of CRPC (for both CRPC-Adeno and CRPC-NE) and fulfils an urgent need for the treatment of PCa patients. Although previous studies have illustrated the emerging roles of epidermal growth factor receptors (EGFR), signal transducer, and activator of transcription 3 (STAT3) signaling in the development of CRPC, the regulatory mechanisms of this interaction between EGFR and STAT3 is still unclear. Our recent studies have shown that crosstalk between EGFR and STAT3 is critical for NE differentiation of PCa. In this review, we have collected recent findings with regard to the involvement of EGFR and STAT3 in malignancy progression and discussed their interactions during the development of therapeutic resistance for PCa.

Suppressive Effect and Molecular Mechanism of Houttuynia cordata Thunb. Extract against Prostate Carcinogenesis and Castration-Resistant Prostate Cancer

Simple Summary

This study explored the chemopreventive effects of Houttuynia cordata Thunb. (HCT) extracts against prostate carcinogenesis in both androgen-sensitive prostate cancer and castration-resistant prostate cancer (CRPC) using the Transgenic Rat for Adenocarcinoma of Prostate (TRAP) model, CRPC xenograft mice, and prostate cancer cell lines. HCT suppressed cell proliferation and stimulated apoptosis via inactivation of AKT/ERK/MAPK in both androgen-sensitive prostate cancer and CRPC cell lines. HCT also inhibited cell migration and EMT phenotypes through the STAT3/Snail/Twist pathway. One of the active compounds of HCT was identified as rutin. Consistent with in vitro study, the incidence of adenocarcinoma in the TRAP model and CRPC tumor growth in the xenograft model were suppressed by induction of apoptosis and inactivation of AKT/ERK/MAPK by HCT intake. Our data demonstrated that HCT attenuated androgen-sensitive prostate cancer and CRPC by mechanisms that may involve inhibition of cell growth and caspase-dependent apoptosis pathways.

Abstract

Houttuynia cordata Thunb. (HCT) is a well-known Asian medicinal plant with biological activities used in the treatment of many diseases including cancer. This study investigated the effects of HCT extract and its ethyl acetate fraction (EA) on prostate carcinogenesis and castration-resistant prostate cancer (CRPC). HCT and EA induced apoptosis in androgen-sensitive prostate cancer cells (LNCaP) and CRPC cells (PCai1) through activation of caspases, down-regulation of androgen receptor, and inactivation of AKT/ERK/MAPK signaling. Rutin was found to be a major component in HCT (44.00 ± 5.61 mg/g) and EA (81.34 ± 5.21 mg/g) in a previous study. Rutin had similar effects to HCT/EA on LNCaP cells and was considered to be one of the active compounds. Moreover, HCT/EA inhibited cell migration and epithelial-mesenchymal transition phenotypes via STAT3/Snail/Twist pathways in LNCaP cells. The consumption of 1% HCT-mixed diet significantly decreased the incidence of adenocarcinoma in the lateral prostate lobe of the Transgenic rat for adenocarcinoma of prostate model. Similarly, tumor growth of PCai1 xenografts was significantly suppressed by 1% HCT treatment. HCT also induced caspase-dependent apoptosis via AKT inactivation in both in vivo models. Together, the results of in vitro and in vivo studies indicate that HCT has inhibitory effects against prostate carcinogenesis and CRPC. This plant therefore should receive more attention as a source for the future development of non-toxic chemopreventive agents against various cancers.

Response to Androgens and Androgen Receptor Antagonists in the Presence of Cytokines in Prostate Cancer

Simple Summary

Prostate cancer is the most frequently diagnosed non-cutaneous tumor in men in the Western world. Therapy for non-organ confined prostate cancer includes anti-androgens such as bicalutamide, enzalutamide and darolutamide. The androgen receptor is expressed during tumor initiation and progression. Androgen receptor could be activated by interleukins, which are produced by blood cells and adjacent stroma. These cytokines may affect response of tumor cells to anti-androgenic drugs, which are commonly used in prostate cancer therapy. There are several experimental studies showing an effect of anti-cytokine therapies in prostate cancer. However, the clinical translation is limited and more clinical trials are needed to improve action of anti-androgens in prostate cells which are stimulated by cytokines.

Abstract

Non-steroidal anti-androgens have a major role in the treatment of non-localized prostate cancer. Interleukins are involved in the regulation of many cellular functions in prostate cancer and also modify cellular response to anti-androgens. A specific role of selected IL is presented in this review. IL-8 is a cytokine expressed in prostate cancer tissue and microenvironment and promotes proliferation and androgen receptor-mediated transcription. In contrast, IL-1 displays negative effects on expression of androgen receptor and its target genes. A subgroup of prostate cancers show neuroendocrine differentiation, which may be in part stimulated by androgen ablation. A similar effect was observed after treatment of cells with IL-10. Another cytokine which is implicated in regulation of androgenic response is IL-23, secreted by myeloid cells. Most studies on androgens and IL were carried out with IL-6, which acts through the signal transducer and activator of the transcription (STAT) factor pathway. IL-6 is implicated in resistance to enzalutamide. Activation of the STAT-3 pathway is associated with increased cellular stemness. IL-6 activation of the androgen receptor in some prostate cancers is associated with increased growth in vitro and in vivo. Molecules such as galiellalactone or niclosamide have an inhibitory effect on both androgen receptor and STAT-3 pathways.

Unravelling the molecular mechanisms of prostate cancer evolution from genotype to phenotype

Prostate cancer (PC) is the most frequently diagnosed cancer and the second leading cause of cancer-related death in men in the Western society. Unfortunately, although the vast majority of patients are initially responsive to androgen-deprivation therapy (ADT), most cases eventually develop from hormone-sensitive prostate cancer (HSPC) to castration-resistant prostate cancer (CRPC). The main reason is PC heterogeneity and evolution during therapy. PC evolution is a continuously progressive process with combination of genomic alterations including canonical AR, TMPRSS2-ERG fusion, SPOP/FOXA1, TP53/RB1/PTEN, BRCA2. Meanwhile, signaling pathways including PI3K, WNT/β-catenin, SRC, IL-6/STAT3 are activated, to promote epithelial mesenchymal transition (EMT), cancer stem cell (CSC)-like features/stemness and neuroendocrine differentiation (NED) of PC. These improve our understanding of the genotype-phenotype relationships. The identification of canonical genetic alterations and signaling pathway activation in PC has shed more insight into genetic background, molecular subtype and disease landscape of PC evolution, resulting in a more flexible role of individual therapies targeting diverse genotype and phenotype presentation.

Normal Basal Epithelial Cells Stimulate the Migration and Invasion of Prostate Cancer Cell RM-1 by TGF-β1/STAT3 Axis in vitro

Aim

Basal epithelial cells are absent in distant prostate cancer. This study aimed to investigate whether basal epithelial cells could suppress migration and invasion of prostate cancer cells to become a new treatment strategy for prostate cancer.

Main Methods

Basal epithelial cells were identified by immunofluorescence with anti-p63. Wound healing assays or transwell assays were used to explore the effects of basal epithelial cells, TGF-β1, SB431542 (inhibitor of TGF-β type I receptor) or stattic (inhibitor of phosphorylated STAT3) on migration or invasion of mouse prostate cancer cell (RM-1). Concentration of TGF-β1 was measured by ELISA assay. HE staining was used to investigate cell morphology. Immunocytochemistry with anti-p63 was used to identify basal epithelial cells. Levels of STAT3, p-STAT3 (Ser727) and proteins associated with EMT were measured with Western blot assay. Cell proliferation was measured with MTT or CCK8 assay.

Results

Normal basal epithelial cells acquired from mouse prostate were specific to anti-p63 and more than 90%. Basal epithelial cells and RM-1 could both secrete TGF-β1. Basal epithelial cells and TGF-β1 promoted the migration and invasion of RM-1 through changing the cell morphology and up-regulating expression of ZEB1, N-cadherin, vimentin, snail and p-STAT3 (Ser727), at the same time down-regulating E-cadherin of RM-1. SB431542 strongly suppressed migration, invasion as well as the expressions of EMT relevant proteins and p-STAT3 (Ser727) of co-cultured RM-1. In addition, stattic suppressed proliferation, migration and invasion of non-treated RM-1 and co-cultured RM-1.

Conclusion

Our study suggests that normal basal epithelial cells might stimulate the migration and invasion of RM-1 by TGF-β1/STAT3 axis which could be suppressed by inhibitor of TGF-β receptor and inhibitor of p-STAT3. So, basal epithelial cells might not become a treatment strategy for prostate cancer, but our results could provide some researching references for other diseases which include basal epithelial cells such as prostatic intraepithelial neoplasia, prostatic hyperplasia, cervical cancer, or urinary bladder cancer.

Communication Between Epithelial-Mesenchymal Plasticity and Cancer Stem Cells: New Insights Into Cancer Progression

The epithelial–mesenchymal transition (EMT) is closely associated with the acquisition of aggressive traits by carcinoma cells and is considered responsible for metastasis, relapse, and chemoresistance. Molecular links between the EMT and cancer stem cells (CSCs) have indicated that EMT processes play important roles in the expression of CSC-like properties. It is generally thought that EMT-related transcription factors (EMT-TFs) need to be downregulated to confer an epithelial phenotype to mesenchymal cells and increase cell proliferation, thereby promoting metastasis formation. However, the genetic and epigenetic mechanisms that regulate EMT and CSC activation are contradictory. Emerging evidence suggests that EMT need not be a binary model and instead a hybrid epithelial/mesenchymal state. This dynamic process correlates with epithelial–mesenchymal plasticity, which indicates a contradictory role of EMT during cancer progression. Recent studies have linked the epithelial–mesenchymal plasticity and stem cell-like traits, providing new insights into the conflicting relationship between EMT and CSCs. In this review, we examine the current knowledge about the interplay between epithelial–mesenchymal plasticity and CSCs in cancer biology and evaluate the controversies and future perspectives. Understanding the biology of epithelial–mesenchymal plasticity and CSCs and their implications in therapeutic treatment may provide new opportunities for targeted intervention.

Resistance to second-generation androgen receptor antagonists in prostate cancer

The introduction of second-generation androgen receptor antagonists (SG-ARAs) has greatly impacted the treatment of metastatic prostate cancer, providing tolerable and efficacious alternatives to chemotherapy. SG-ARAs provide similar therapeutic benefit to abiraterone, a potent CYP17 inhibitor, and do not require the co-administration of prednisone. Despite considerable improvements in clinical outcomes in the settings of both castration sensitivity and castration resistance, the durability of clinical response to the SG-ARAs enzalutamide, apalutamide and darolutamide, similar to abiraterone, is limited by inevitable acquired resistance. Genomic aberrations that confer resistance to SG-ARAs or provide potential alternative treatment modalities have been identified in numerous studies, including alterations of the androgen receptor, DNA repair, cell cycle, PI3K-AKT-mTOR and Wnt-β-catenin pathways. To combat resistance, researchers have explored approaches to optimizing the utility of available treatments, as well as the use of alternative agents with a variety of targets, including AR-V7, AKT, EZH2 and HIF1α. Ongoing research to establish predictive biomarkers for the treatment of tumours with resistance to SG-ARAs led to the approval of the PARP inhibitors olaparib and rucaparib in pre-treated metastatic castration-resistant prostate cancer. The results of ongoing studies will help to shape precision medicine in prostate cancer and further optimize treatment paradigms to maximize clinical outcomes.

STAMP2 Expression Mediated by Cytokines Attenuates Their Growth-Limiting Effects in Prostate Cancer Cells

Simple Summary

Prostate cancer (PCa) is the most common non-skin cancer and one of the leading causes of cancer death in men. Despite significant developments in therapy options with improved survival, no curative treatment is currently available. We have previously identified six transmembrane protein of prostate 2 (STAMP2) as an important factor for PCa growth and survival. We now show that STAMP2 expression is regulated by inflammatory signaling, which has recently been implicated in PCa. Two proinflammatory cytokines, interleukin 6 and interleukin 1 beta, synergize with each other to induce STAMP2 expression. Interestingly, STAMP2 knockdown increased the sensitivity of PCa cells to cytokine treatment. Thus, STAMP2 that acts as a survival factor in PCa, is both independently and synergistically regulated by inflammatory signaling that may affect disease progression.

Abstract

Inflammatory events and dysregulated cytokine expression are implicated in prostate cancer (PCa), but the underlying molecular mechanisms are poorly understood at present. We have previously identified six transmembrane protein of the prostate 2 (STAMP2, also known as STEAP4) as an androgen-regulated gene, as well as a key regulator of PCa growth and survival. STAMP2 is also regulated by, and participates in, inflammatory signaling in other tissues and pathologies. Here, we show that the proinflammatory cytokines interleukin 6 (IL-6) and Interleukin 1 beta (IL-1β) significantly increase and strongly synergize in promoting STAMP2 expression in PCa cells. The two cytokines increase androgen-induced STAMP2 expression, but not expression of other known androgen target genes, suggesting a unique interplay of androgens and cytokines in regulating STAMP2 expression. Interestingly, STAMP2 knockdown significantly increased the ability of IL-6 and IL-1β to inhibit PCa cell growth in vitro. These results suggest that STAMP2 may represent a unique node through which inflammatory events mediate their effects on PCa growth and survival.

Androgen Receptor-Dependent Mechanisms Mediating Drug Resistance in Prostate Cancer

Androgen receptor (AR) is a main driver of prostate cancer (PCa) growth and progression as well as the key drug target. Appropriate PCa treatments differ depending on the stage of cancer at diagnosis. Although androgen deprivation therapy (ADT) of PCa is initially effective, eventually tumors develop resistance to the drug within 2-3 years of treatment onset leading to castration resistant PCa (CRPC). Castration resistance is usually mediated by reactivation of AR signaling. Eventually, PCa develops additional resistance towards treatment with AR antagonists that occur regularly, also mostly due to bypass mechanisms that activate AR signaling. This tumor evolution with selection upon therapy is presumably based on a high degree of tumor heterogenicity and plasticity that allows PCa cells to proliferate and develop adaptive signaling to the treatment and evolve pathways in therapy resistance, including resistance to chemotherapy. The therapy-resistant PCa phenotype is associated with more aggressiveness and increased metastatic ability. By far, drug resistance remains a major cause of PCa treatment failure and lethality. In this review, various acquired and intrinsic mechanisms that are AR‑dependent and contribute to PCa drug resistance will be discussed.

Metformin and Androgen Receptor-Axis-Targeted (ARAT) Agents Induce Two PARP-1-Dependent Cell Death Pathways in Androgen-Sensitive Human Prostate Cancer Cells

We explored whether the anti-prostate cancer (PC) activity of the androgen receptor-axis-targeted agents (ARATs) abiraterone and enzalutamide is enhanced by metformin. Using complementary biological and molecular approaches, we determined the associated underlying mechanisms in pre-clinical androgen-sensitive PC models. ARATs increased androgren receptors (ARs) in LNCaP and AR/ARv7 (AR variant) in VCaP cells, inhibited cell proliferation in both, and induced poly(ADP-ribose) polymerase-1 (PARP-1) cleavage and death in VCaP but not LNCaP cells. Metformin decreased AR and ARv7 expression and induced cleaved PARP-1-associated death in both cell lines. Metformin with abiraterone or enzalutamide decreased AR and ARv7 expression showed greater inhibition of cell proliferation and greater induction of cell death than single agent treatments. Combination treatments led to increased cleaved PARP-1 and enhanced PARP-1 activity manifested by increases in poly(ADP-ribose) (PAR) and nuclear accumulation of apoptosis inducing factor (AIF). Enhanced annexin V staining occurred in LNCaP cells only with metformin/ARAT combinations, but no caspase 3 recruitment occurred in either cell line. Finally, metformin and metformin/ARAT combinations increased lysosomal permeability resulting in cathepsin G-mediated PARP-1 cleavage and cell death. In conclusion, metformin enhances the efficacy of abiraterone and enzalutamide via two PARP-1-dependent, caspase 3-independent pathways, providing a rationale to evaluate these combinations in castration-sensitive PC.

Metformin exerts anti-cancerogenic effects and reverses epithelial-to-mesenchymal transition trait in primary human intrahepatic cholangiocarcinoma cells

Intrahepatic cholangiocarcinoma (iCCA) is a highly aggressive cancer with marked resistance to chemotherapeutics without therapies. The tumour microenvironment of iCCA is enriched of Cancer-Stem-Cells expressing Epithelial-to-Mesenchymal Transition (EMT) traits, being these features associated with aggressiveness and drug resistance. Treatment with the anti-diabetic drug Metformin, has been recently associated with reduced incidence of iCCA. We aimed to evaluate the anti-cancerogenic effects of Metformin in vitro and in vivo on primary cultures of human iCCA. Our results showed that Metformin inhibited cell proliferation and induced dose- and time-dependent apoptosis of iCCA. The migration and invasion of iCCA cells in an extracellular bio-matrix was also significantly reduced upon treatments. Metformin increased the AMPK and FOXO3 and induced phosphorylation of activating FOXO3 in iCCA cells. After 12 days of treatment, a marked decrease of mesenchymal and EMT genes and an increase of epithelial genes were observed. After 2 months of treatment, in order to simulate chronic administration, Cytokeratin-19 positive cells constituted the majority of cell cultures paralleled by decreased Vimentin protein expression. Subcutaneous injection of iCCA cells previously treated with Metformin, in Balb/c-nude mice failed to induce tumour development. In conclusion, Metformin reverts the mesenchymal and EMT traits in iCCA by activating AMPK-FOXO3 related pathways suggesting it might have therapeutic implications.

Advancement and properties of circular RNAs in prostate cancer: An emerging and compelling frontier for discovering

Prostate cancer (PC) is the most common carcinoma among men worldwide which results in 26% of leading causes of cancer-related death. However, the ideal and effective molecular marker remains elusive. CircRNA, initially observed in plant-infected viruses and Sendai virus in 1979, is generated from pre-mRNA back-splicing and comes in to play by adequate expression. The differential expression in prostate tissues compared with the control reveals the promising capacity in modulating processes including carcinogenesis and metastasis. However, the biological mechanisms of regulatory network in PC needs to systemically concluded. In this review, we enlightened the comprehensive studies on the definite mechanisms of circRNAs affecting tumor progression and metastasis. What's more, we validated the potential clinical application of circRNAs serving as diagnostic and prognostic biomarker. The discussion and analysis in circRNAs will broaden our knowledge of the pathogenesis of PC and further optimize the current therapies against different condition.

The Chemosensitizing Role of Metformin in Anti-Cancer Therapy

Chemoresistance, which leads to the failure of chemotherapy and further tumor recurrence, presents the largest hurdle for the success of anti-cancer therapy. In recent years, metformin, a widely used first-line antidiabetic drug, has attracted increasing attention for its anti-cancer effects. A growing body of evidence indicates that metformin can sensitize tumor responses to different chemotherapeutic drugs, such as hormone modulating drugs, anti-metabolite drugs, antibiotics, and DNA-damaging drugs via selective targeting of Cancer Stem Cells (CSCs), improving the hypoxic microenvironment, and by suppressing tumor metastasis and inflammation. In addition, metformin may regulate metabolic programming, induce apoptosis, reverse Epithelial to Mesenchymal Transition (EMT), and Multidrug Resistance (MDR). In this review, we summarize the chemosensitization effects of metformin and focus primarily on its molecular mechanisms in enhancing the sensitivity of multiple chemotherapeutic drugs, through targeting of mTOR, ERK/P70S6K, NF-κB/HIF-1 α, and Mitogen- Activated Protein Kinase (MAPK) signaling pathways, as well as by down-regulating the expression of CSC genes and Pyruvate Kinase isoenzyme M2 (PKM2). Through a comprehensive understanding of the molecular mechanisms of chemosensitization provided in this review, the rationale for the use of metformin in clinical combination medications can be more systematically and thoroughly explored for wider adoption against numerous cancer types.>.

Mechanisms of enzalutamide resistance in castration-resistant prostate cancer and therapeutic strategies to overcome it

Prostate cancer is the second most common malignancy in men and androgen deprivation therapy is the first-line therapy. However, most cases will eventually develop castration-resistant prostate cancer after androgen deprivation therapy treatment. Enzalutamide is a second-generation androgen receptor antagonist approved by the Food and Drug Administration to treat patients with castration-resistant prostate cancer. Unfortunately, patients receiving enzalutamide treatment will ultimately develop resistance via various complicated mechanisms. This review examines the emerging information on these resistance mechanisms, including androgen receptor-related signalling pathways, glucocorticoid receptor-related pathways and metabolic effects. Notably, lineage plasticity and phenotype switching, gene polymorphisms and the relationship between microRNAs and drug resistance are addressed. Furthermore, potential therapeutic strategies for enzalutamide-resistant castration-resistant prostate cancer treatment are suggested, which can help discover more effective and specific regimens to overcome enzalutamide resistance.

Treatment and resistance mechanisms in castration-resistant prostate cancer: new implications for clinical decision making?

Introduction: The armamentarium of treatment options in metastatic and non-metastatic CRPC is rapidly evolving. However, the question of how individual treatment decisions should be balanced by available predictive clinical parameters, pharmacogenetic and drug interaction profiles, or compound-associated molecular biomarkers is a major challenge for clinical practice.Areas covered: We discuss treatment and resistance mechanisms in PC with regard to their association to drug efficacy and tolerability. Current efforts of combination treatment and putative predictive biomarkers of available and upcoming compounds are highlighted with regard to their implication on clinical decision-making.Expert opinion: Several treatment approaches are delineated, where identification of resistance mechanisms in CRPC may guide treatment selection. To date, most of these candidate biomarkers will however be found only in a small subset of patients. While current approaches of combination treatment in CRPC are proving synergistic effects on cancer biology, higher complexity with regard to biomarker analysis and interaction profiles of the respective compounds may be expected. Among other aspects of personalized treatment, consideration of drug-drug interaction and pharmacogenetics is an underrepresented issue. However, the non-metastatic castration resistant prostate cancer situation may be an example for treatment selection based on drug interaction profiles in the future.