Divergent androgen regulation of unfolded protein response pathways drives prostate cancer

Oxidative stress as a catalyst in prostate cancer progression: unraveling molecular mechanisms and exploring therapeutic interventions

Prostate cancer is the second most common malignancy among men worldwide, with its incidence and mortality rates steadily increasing. Although androgen deprivation therapy (ADT) combined with androgen receptor inhibitors has shown significant efficacy in treating prostate cancer, resistance to treatment remains a major challenge, particularly in patients with metastatic prostate cancer. Reactive oxygen species (ROS), a class of highly reactive molecules, can induce oxidative stress within cells, thereby affecting cellular survival and function. In cancer cells, elevated ROS levels not only promote proliferation and invasion but also contribute to the malignancy of tumors by modulating the tumor microenvironment, enhancing angiogenesis, and facilitating extracellular matrix remodeling. This review systematically explores the pathways of ROS generation in prostate cancer, their interaction with the androgen receptor signaling pathway, and the role of external factors such as obesity and aging in promoting ROS production. The findings highlight that ROS drive prostate cancer progression through multiple mechanisms, including altering the tumor microenvironment, activating the unfolded protein response (UPR), and regulating miRNA expression. By providing a comprehensive analysis of ROS-mediated mechanisms in prostate cancer, this review offers new insights into the development of targeted antioxidant therapeutic strategies.

DPH2 is a biomarker associated with cell death, immunity and prognosis based on pan-cancer analysis

OBJECTIVE

DPH2, also known as DPH2L2, is one of two human genes similar to yeast dph2. One DPH2 variant has been linked to diphthamide syndrome, a disorder affecting ribosome function. While studies on DPH2 in a single cancer type have been documented, no comprehensive investigations of DPH2 across pan-cancer have been reported, its role in tumor pathogenesis and development remains unclear.

METHODS

The predictive significance and immune and biological roles of DPH2 in 33 different cancer types were investigated. We conducted a comprehensive analysis of DPH2 in pan-cancer using various bioinformatics tools, including expression, prognosis, its association with immune infiltration, cell death, methylation, and many other aspects. In addition, qRT-PCR and immunohistochemistry experiments confirmed DPH2 expression in prostate adenocarcinoma (PRAD) tissues, DPH2 biological function in PRAD was assessed using in vitro experiments, and used immunofluorescence to validate the proteins associated with DPH2.

RESULTS

The DPH2 expression was high in most tumors and showed significant correlations with OS and PFI. Our experimental findings confirmed that DPH2 is highly expressed in PRAD, while DPH2 knockdown inhibited prostate cancer cell proliferation, invasion, and migration. Furthermore, our data suggest that DPH2 may significantly influence immune cell infiltration. DPH2 was significantly correlated with cell death-related genes. DPH2 can influence cancer progression through changes in DNA methylation levels, or N6-methyladenosine site modification. GSEA and GSVA revealed that DPH2 levels were significantly associated with enrichment for oncogenic and immune-related pathways. Drug sensitivity analysis revealed that the elevated DPH2 expression is linked to development of resistance against numerous anticancer medications.

CONCLUSION

DPH2 has potential as a novel prognostic biomarker that may significantly impact tumor onset and progression. Consequently, DPH2 could serve as a target for new cancer treatments.

Modulating Endoplasmic Reticulum Stress in Gastrointestinal Cancers: Insights from Traditional Chinese Medicine

Endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) play critical roles in tumorigenesis, cancer progression, and drug resistance. Persistent activation of the ER stress system enhances the survival capacities of malignant tumor cells, including increased proliferation, invasion, and resistance to treatment. Dysregulation of ER function and the resultant stress is a common cellular response to cancer therapies and may lead to cancer cell death. Currently, growing evidence suggests that Traditional Chinese medicine (TCM), either as a monotherapy or in combination with other treatments, offers significant advantages in preventing cancer, inhibiting tumor growth, reducing surgical complications, improving drug sensitivity, and mitigating drug-induced damage. Some of these natural products have even entered clinical trials as primary or complementary anticancer agents. In this review, we summarize the anticancer effects of TCM monomers/natural products on the gastrointestinal (GI) tumors and explore their mechanisms through ER stress modulation. We believe that ongoing laboratory research and the clinical development of TCM-based cancer therapies hold considerable potential for advancing future cancer treatments.

Targeting IRE1α reprograms the tumor microenvironment and enhances anti-tumor immunity in prostate cancer

Unfolded protein response (UPR) is a central stress response pathway that is hijacked by tumor cells for their survival. Here, we find that IRE1α signaling, one of the canonical UPR arms, is increased in prostate cancer (PCa) patient tumors. Genetic or small molecule inhibition of IRE1α in syngeneic mouse PCa models and an orthotopic model decreases tumor growth. IRE1α ablation in cancer cells potentiates interferon responses and activates immune system related pathways in the tumor microenvironment (TME). Single-cell RNA-sequencing analysis reveals that targeting IRE1α in cancer cells reduces tumor-associated macrophage abundance. Consistently, the small molecule IRE1α inhibitor MKC8866, currently in clinical trials, reprograms the TME and enhances anti-PD-1 therapy. Our findings show that IRE1α signaling not only promotes cancer cell growth and survival but also interferes with anti-tumor immunity in the TME. Thus, targeting IRE1α can be a promising approach for improving anti-PD-1 immunotherapy in PCa.

Mitochondrial Elongation and ROS-Mediated Apoptosis in Prostate Cancer Cells under Therapy with Apalutamide and Complex I Inhibitor

Metabolic reprogramming and mitochondrial dynamics are pivotal in prostate cancer (PCa) progression and treatment resistance, making them essential targets for therapeutic intervention. In this study, we investigated the effects of the androgen receptor antagonist apalutamide (ARN) and the mitochondrial electron transport chain complex I inhibitor IACS-010759 (IACS) on the mitochondrial network architecture and dynamics in PCa cells. Treatment with ARN and/or IACS induced significant changes in mitochondrial morphology, particularly elongation, in androgen-sensitive PCa cells. Additionally, ARN and IACS modulated the mitochondrial fission and fusion processes, indicating a convergence of metabolic and androgen-signaling pathways in shaping mitochondrial function. Notably, the combination treatment with ARN and IACS resulted in increased apoptotic cell death and mitochondrial oxidative stress selectively in the androgen-sensitive PCa cells. Our findings highlight the therapeutic potential of targeting mitochondrial metabolism in prostate cancer and emphasize the need for further mechanistic understanding to optimize treatment strategies and improve patient outcomes.

Adaptations of membrane trafficking in cancer and tumorigenesis

Membrane trafficking, a fundamental cellular process encompassing the transport of molecules to specific organelles, endocytosis at the plasma membrane and protein secretion, is crucial for cellular homeostasis and signalling. Cancer cells adapt membrane trafficking to enhance their survival and metabolism, and understanding these adaptations is vital for improving patient responses to therapy and identifying therapeutic targets. In this Review, we provide a concise overview of major membrane trafficking pathways and detail adaptations in these pathways, including COPII-dependent endoplasmic reticulum (ER)-to-Golgi vesicle trafficking, COPI-dependent retrograde Golgi-to-ER trafficking and endocytosis, that have been found in cancer. We explore how these adaptations confer growth advantages or resistance to cell death and conclude by discussing the potential for utilising this knowledge in developing new treatment strategies and overcoming drug resistance for cancer patients.

Targeting the IRE1α-XBP1s axis confers selective vulnerability in hepatocellular carcinoma with activated Wnt signaling

Liver-specific Ern1 knockout impairs tumor progression in mouse models of hepatocellular carcinoma (HCC). However, the mechanistic role of IRE1α in human HCC remains unclear. In this study, we show that XBP1s, the major downstream effector of IRE1α, is required for HCC cell survival both in vitro and in vivo. Mechanistically, XBP1s transactivates LEF1, a key co-factor of β-catenin, by binding to its promoter. Moreover, XBP1s physically interacts with LEF1, forming a transcriptional complex that enhances classical Wnt signaling. Consistently, the activities of XBP1s and LEF1 are strongly correlated in human HCC and with disease prognosis. Notably, selective inhibition of XBP1 splicing using an IRE1α inhibitor significantly repressed the viability of tumor explants as well as the growth of tumor xenografts derived from patients with distinct Wnt/LEF1 activities. Finally, machine learning algorithms developed a powerful prognostic signature based on the activities of XBP1s/LEF1. In summary, our study uncovers a key mechanistic role for the IRE1α-XBP1s pathway in human HCC. Targeting this axis could provide a promising therapeutic strategy for HCC with hyperactivated Wnt/LEF1 signaling.

Metabolic reprogramming directed by super-enhancers in tumors: An emerging landscape

Metabolic reprogramming is an essential hallmark of tumors, and metabolic abnormalities are strongly associated with the malignant phenotype of tumor cells. This is closely related to transcriptional dysregulation. Super-enhancers are extremely active cis-regulatory regions in the genome, and can amalgamate a complex set of transcriptional regulatory components that are crucial for establishing tumor cell identity, promoting tumorigenesis, and enhancing aggressiveness. In addition, alterations in metabolic signaling pathways are often accompanied by changes in super-enhancers. Presently, there is a surge in interest in the potential pathogenesis of various tumors through the transcriptional regulation of super-enhancers and oncogenic mutations in super-enhancers. In this review, we summarize the functions of super-enhancers, oncogenic signaling pathways, and tumor metabolic reprogramming. In particular, we focus on the role of the super-enhancer in tumor metabolism and its impact on metabolic reprogramming. This review also discusses the prospects and directions in the field of super-enhancer and metabolic reprogramming.

New mode of action of curcumin on prostate cancer cells: Modulation of endoplasmic reticulum-associated degradation mechanism and estrogenic signaling

Prostate cancer is leading to cancer-related mortality in numerous men each year worldwide. While there are several treatment options, acquired drug resistance mostly limits the success of treatments. Therefore, there is a need for the development of innovative treatments. Curcumin is one of the bioactive polyphenolic ingredients identified in turmeric and has numerous biological activities, such as anti-inflammatory and anticancer. In the present study, we investigated the effect of curcumin on the ER-associated degradation (ERAD) and estrogenic signaling in prostate cancer cells. The antiproliferative effect of curcumin on human androgen-dependent prostate cancer cell lines LNCaP and VCaP was estimated by WST-1 assay. Morphological alterations were investigated with an inverted microscope. We investigated the effect of curcumin on ERAD and estrogen signaling proteins by immunoblotting assay. To evaluate the impact of curcumin on endoplasmic reticulum (ER) protein quality-related, the expression level of 32 genes was analyzed by quantitative reverse transcription polymerase chain reaction. The nuclear translocation of estrogen receptor was examined by nuclear fractionation and immunofluorescence microscopy. We found that curcumin effectively reduced the proliferation rates of LNCaP and VCaP cells. ERAD proteins; Hrd1, gp78, p97/VCP, Ufd1 and Npl4 were strongly induced by curcumin. Also, the steady-state level of polyubiquitin was increased in a dose-dependent manner in both cell lines. Curcumin administration remarkably decreased the protein levels of estrogen receptor-alfa (Erα), whereas estrogen receptor-beta unaffected. Additionally, curcumin strongly restricted the nuclear translocation of Erα. Present data suggest that curcumin may be effectively used in therapeutic approaches associated with the targeting ER protein quality control mechanism and modulation of estrogen signaling in prostate cancer.

Proteome-Wide Profiling Using Sample Multiplexing of a Human Cell Line Treated with Cannabidiol (CBD) and Tetrahydrocannabinol (THC)

Cannabis has been used historically for both medicinal and recreational purposes, with the most notable cannabinoids being cannabidiol (CBD) and tetrahydrocannabinol (THC). Although their therapeutic effects have been well studied and their recreational use is highly debated, the underlying mechanisms of their biological effects remain poorly defined. In this study, we use isobaric tag-based sample multiplexed proteome profiling to investigate protein abundance differences in the human neuroblastoma SH-SY5Y cell line treated with CBD and THC. We identified significantly regulated proteins by each treatment and performed a pathway classification and associated protein-protein interaction analysis. Our findings suggest that these treatments may lead to mitochondrial dysfunction and induce endoplasmic reticulum stress. These data can potentially be interrogated further to investigate the potential role of CBD and THC in various biological and disease contexts, providing a foundation for future studies.

Estrogens drive the endoplasmic reticulum-associated degradation and promote proto-oncogene c-Myc expression in prostate cancer cells by androgen receptor/estrogen receptor signaling

The tumorigenic properties of prostate cancer are regulated by advanced hormonal regulation-mediated complex molecular signals. Therefore, characterizing the regulation of these signal transduction systems is crucial for understanding prostate cancer biology. Recent studies have shown that endoplasmic reticulum (ER)-localized protein quality control mechanisms, including ER-associated degradation (ERAD) and unfolded protein response (UPR) signaling contribute to prostate carcinogenesis and to the development of drug resistance. It has also been determined that these systems are tightly regulated by androgens. However, the role of estrogenic signaling in prostate cancer and its effects on protein quality control mechanisms is not fully understood. Herein, we investigated the regulatory effects of estrogens on ERAD and UPR and their impacts on prostate carcinogenesis. We found that estrogens strongly regulated the ERAD components and IRE1⍺ branch of UPR by Er⍺/β/AR axis. Besides, estrogenic signaling rigorously regulated the tumorigenicity of prostate cancer cells by promoting c-Myc expression and epithelial-mesenchymal transition (EMT). Moreover, estrogenic signal blockage significantly decreased the tumorigenic features of prostate cancer cells. Additionally, simultaneous inhibition of androgenic/estrogenic signals more efficiently inhibited tumorigenicity of prostate cancer cells, including proliferation, migration, invasion and colonial growth. Furthermore, computational-based molecular docking, molecular dynamics simulations and MMPBSA calculations supported the estrogenic stimulation of AR. Present findings suggested that ERAD components and IRE1⍺ signaling are tightly regulated by estrogen-stimulated AR and Er⍺/β. Our data suggest that treatment approaches targeting the co-inhibition of androgenic/estrogenic signals may pave the way for new treatment approaches to be developed for prostate cancer. The present model of the impact of estrogens on ERAD and UPR signaling in androgen-sensitive prostate cancer cells.

Prolyl 4-hydroxylase subunit beta (P4HB) could serve as a prognostic and radiosensitivity biomarker for prostate cancer patients

BACKGROUND

Prolyl 4-hydroxylase subunit beta (P4HB) has been reported as a suppressor in ferroptosis. However, no known empirical research has focused on exploring relationships between P4HB and prostate cancer (PCa). In this research, we initially examine the function of P4HB in PCa by thorough analysis of numerous databases and proliferation experiment.

METHODS

We analyzed the correlations of P4HB expression with prognosis, clinical features, mutation genes, tumor heterogeneity, stemness, tumor immune microenvironment and PCa cells using multiple databases and in vitro experiment with R 3.6.3 software and its suitable packages.

RESULTS

P4HB was significantly upregulated in tumor tissues compared to normal tissues and was closely related to biochemical recurrence-free survival. In terms of clinical correlations, we found that higher P4HB expression was significantly related to older age, higher Gleason score, advanced T stage and residual tumor. Surprisingly, P4HB had highly diagnostic accuracy of radiotherapy resistance (AUC 0.938). TGF beta signaling pathway and dorso ventral axis formation were upregulated in the group of low-expression P4HB. For tumor stemness, P4HB expression was positively related to EREG.EXPss and RNAss, but was negatively associated with ENHss and DNAss with statistical significance. For tumor heterogeneity, P4HB expression was positively related to MATH, but was negatively associated with tumor ploidy and microsatellite instability. For the overall assessment of TME, we observed that P4HB expression was negatively associated with all parameters, including B cells, CD4+ T cells, CD8+ T cells, neutrophils, macrophages, dendritic cells, stromal score, immune score and ESTIMATE score. Spearman analysis showed that P4HB expression was negatively related to TIDE score with statistical significance. In vitro experiment, RT-qPCR and western blot showed that three siRNAs of P4HB were effective on the knockdown of P4HB expression. Furthermore, we observed that the downregulation of P4HB had significant influence on the cell proliferation of six PCa cell lines, including LNCap, C4-2, C4-2B, PC3, DU145 and 22RV1 cells.

CONCLUSIONS

In this study, we found that P4HB might serve as a prognostic biomarker and predict radiotherapy resistance for PCa patients. Downregulation of P4HB expression could inhibit the cell proliferation of PCa cells.

Ultrastructural analysis of prostate cancer tissue provides insights into androgen-dependent adaptations to membrane contact site establishment

Membrane trafficking and organelle contact sites are important for regulating cell metabolism and survival; processes often deregulated in cancer. Prostate cancer is the second leading cause of cancer-related death in men in the developed world. While early-stage disease is curable by surgery or radiotherapy there is an unmet need to identify prognostic biomarkers, markers to treatment response and new therapeutic targets in intermediate-late stage disease. This study explored the morphology of organelles and membrane contact sites in tumor tissue from normal, low and intermediate histological grade groups. The morphology of organelles in secretory prostate epithelial cells; including Golgi apparatus, ER, lysosomes; was similar in prostate tissue samples across a range of Gleason scores. Mitochondrial morphology was not dramatically altered, but the number of membrane contacts with the ER notably increased with disease progression. A three-fold increase of tight mitochondria-ER membrane contact sites was observed in the intermediate Gleason score group compared to normal tissue. To investigate whether these changes were concurrent with an increased androgen signaling in the tissue, we investigated whether an anti-androgen used in the clinic to treat advanced prostate cancer (enzalutamide) could reverse the phenotype. Patient-derived explant tissues with an intermediate Gleason score were cultured ex vivo in the presence or absence of enzalutamide and the number of ER-mitochondria contacts were quantified for each matched pair of tissues. Enzalutamide treated tissue showed a significant reduction in the number and length of mitochondria-ER contact sites, suggesting a novel androgen-dependent regulation of these membrane contact sites. This study provides evidence for the first time that prostate epithelial cells undergo adaptations in membrane contact sites between mitochondria and the ER during prostate cancer progression. These adaptations are androgen-dependent and provide evidence for a novel hormone-regulated mechanism that support establishment and extension of MAMs. Future studies will determine whether these changes are required to maintain pro-proliferative signaling and metabolic changes that support prostate cancer cell viability.

Triiodothyronine positively regulates endoplasmic reticulum-associated degradation (ERAD) and promotes androgenic signaling in androgen-dependent prostate cancer cells

Thyroid hormones (THs) play crucial roles in numerous physiological processes of nearly all mammalian tissues, including differentiation and metabolism. Deterioration of TH signaling has been associated with several pathologies, including cancer. The effect of highly active triiodothyronine (T3) has been investigated in many in vivo and in vitro cancer models. However, the role of T3 on cancerous prostate tissue is controversial. Recent studies have focused on the characterization of the supportive roles of the endoplasmic reticulum-associated degradation (ERAD) and unfolded protein response (UPR) signaling in prostate cancer (PCa) and investigating new hormonal regulation patterns, including estrogen, progesterone and 1,25(OH)₂D₃. Additionally, androgenic signaling controlled by androgens, which are critical in PCa progression, has been shown to be regulated by other steroid hormones. While the effects of T3 on ERAD and UPR are unknown today, the impact on androgenic signaling is still not understood in PCa. Therefore, we aimed to investigate the molecular action of T3 on the ERAD mechanism and UPR signaling in PCa cells and also extensively examined the effect of T3 on androgenic signaling. Our data strongly indicated that T3 tightly regulates ERAD and UPR signaling in androgen-dependent PCa cells. We also found that T3 stimulates androgenic signaling by upregulating AR mRNA and protein levels and enhancing its nuclear translocation. Additionally, advanced computational studies supported the ligand binding effect of T3 on AR protein. Our data suggest that targeting thyroidal signaling should be considered in therapeutic approaches to be developed for prostate malignancy in addition to other steroidal regulations.

A novel IRE1 kinase inhibitor for adjuvant glioblastoma treatment

Inositol-requiring enzyme 1 (IRE1) is a major mediator of the unfolded protein response (UPR), which is activated upon endoplasmic reticulum (ER) stress. Tumor cells experience ER stress due to adverse microenvironmental cues, a stress overcome by relying on IRE1 signaling as an adaptive mechanism. Herein, we report the discovery of structurally new IRE1 inhibitors identified through the structural exploration of its kinase domain. Characterization in in vitro and in cellular models showed that they inhibit IRE1 signaling and sensitize glioblastoma (GB) cells to the standard chemotherapeutic, temozolomide (TMZ). Finally, we demonstrate that one of these inhibitors, Z4P, permeates the blood-brain barrier (BBB), inhibits GB growth, and prevents relapse in vivo when administered together with TMZ. The hit compound disclosed herein satisfies an unmet need for targeted, non-toxic IRE1 inhibitors and our results support the attractiveness of IRE1 as an adjuvant therapeutic target in GB.

Dexamethasone-stimulated glucocorticoid receptor signaling positively regulates the endoplasmic reticulum-associated degradation (ERAD) mechanism in hepatocellular carcinoma cells

Hepatocellular carcinoma is one of the most common types of primary liver cancer in adults and also it is the third leading cause of cancer-related deaths worldwide. Although there are various treatment options such as surgery, radiation, targeted drug therapy, immunotherapy and chemotherapy, most hepatocellular carcinomas are highly resistant to systemic treatments. Today, the molecular pathogenesis of hepatocellular carcinoma remains largely obscure. Therefore, there is a need for detailed research for the characterization of molecular signaling networks related to the development of hepatocellular carcinoma. Recent studies have attention to the hormonal regulation of hepatocellular carcinoma cells mediated by systemic hormones such as glucocorticoids. However, glucocorticoid-mediated regulation of endoplasmic reticulum-associated degradation (ERAD) and unfolded protein response (UPR), which are known to be important survival mechanisms for cancer cells remains unknown in hepatocellular carcinoma. In the present study, we showed that dexamethasone-induced glucocorticoid receptor signaling mediated advanced regulation of ERAD and UPR signaling in hepatocellular carcinoma cells. Glucocorticoid signaling positively regulates mRNA and protein levels of ERAD components and also protein kinase RNA-like ER Kinase (PERK) and inositol-requiring enzyme 1⍺ (IRE1⍺) branches of UPR signaling are accompanied the glucocorticoid signaling. In addition, putative glucocorticoid response elements (GREs) were determined in the promoter regions of ERAD members in in-silico analyses. Additionally, silencing of ERAD components significantly reduced the tumorigenic features of hepatocellular carcinoma cells, including cell proliferation, metastasis, invasion and 3D tumor formation. Collectively, these results reveal a novel pattern of regulation of ERAD components by glucocorticoid-mediated in human hepatocellular carcinoma cells.

Protein persulfidation: Rewiring the hydrogen sulfide signaling in cell stress response

The past few decades have witnessed significant progress in the discovery of hydrogen sulfide (H₂S) as a ubiquitous gaseous signaling molecule in mammalian physiology, akin to nitric oxide and carbon monoxide. As the third gasotransmitter, H₂S is now known to exert a wide range of physiological and cytoprotective functions in the biological systems. However, endogenous H₂S concentrations are usually low, and its potential biologic mechanisms responsible have not yet been fully clarified. Recently, a growing body of evidence has demonstrated that protein persulfidation, a posttranslational modification of cysteine residues (RSH) to persulfides (RSSH) elicited by H₂S, is a fundamental mechanism of H₂S-mediated signaling pathways. Persulfidation, as a biological switch for protein function, plays an important role in the maintenance of cell homeostasis in response to various internal and external stress stimuli and is also implicated in numerous diseases, such as cardiovascular and neurodegenerative diseases and cancer. In this review, the biological significance of protein persulfidation by H₂S in cell stress response is reviewed providing a framework for understanding the multifaceted roles of H₂S. A mechanism-guided perspective can help open novel avenues for the exploitation of therapeutics based on H₂S-induced persulfidation in the context of diseases.

Loss of ATF6α in a human carcinoma cell line is compensated not by its paralogue ATF6β but by sustained activation of the IRE1 and PERK arms for tumor growth in nude mice

To survive poor nutritional conditions, tumor cells activate the unfolded protein response, which is composed of the IRE1, PERK, and ATF6 arms, to maintain the homeostasis of the endoplasmic reticulum, where secretory and transmembrane proteins destined for the secretory pathway gain their correct three-dimensional structure. The requirement of the IRE1 and PERK arms for tumor growth in nude mice is established. Here we investigated the requirement for the ATF6 arm, which consists of ubiquitously expressed ATF6α and ATF6β, by constructing ATF6α-knockout (KO), ATF6β-KO, and ATF6α/β-double KO (DKO) in HCT116 cells derived from human colorectal carcinoma. Results showed that these KO cells grew similarly to wild-type (WT) cells in nude mice, contrary to expectations from our analysis of ATF6α-KO, ATF6β-KO, and ATF6α/β-DKO mice. We then found that the loss of ATF6α in HCT116 cells resulted in sustained activation of the IRE1 and PERK arms in marked contrast to mouse embryonic fibroblasts, in which the loss of ATF6α is compensated for by ATF6β. Although IRE1-KO in HCT116 cells unexpectedly did not affect tumor growth in nude mice, IRE1-KO HCT116 cells with ATF6α knockdown grew significantly more slowly than WT or IRE1-KO HCT116 cells. These results have unraveled the situation-dependent differential compensation strategies of ATF6α.

1,25(OH)2 D3 induced vitamin D receptor signaling negatively regulates endoplasmic reticulum-associated degradation (ERAD) and androgen receptor signaling in human prostate cancer cells

Steroid hormone signaling is critical in the tumor progression and the regulation of physiological mechanisms such as endoplasmic reticulum-associated degradation (ERAD) and unfolded protein response (UPR) in prostate cancer. 1,25(OH)₂ D₃ is an active metabolite of vitamin D classified as a steroid hormone. It exhibits anti-tumor effects, including angiogenesis and suppression of cell cycle progression. Moreover, progressively reducing expression levels of vitamin D receptor (VDR) are observed in many cancer types, including the prostate. In the present study, we investigated the molecular action of 1,25(OH)₂ D₃ on ERAD, UPR and androgenic signaling. We found that 1,25(OH)₂ D₃ negatively regulated the expression level of ERAD components and divergently controlled the inositol-requiring enzyme 1⍺ (IRE1⍺) and protein kinase RNA-like ER kinase (PERK) branches of UPR in LNCaP human prostate cancer cells. Also, similar results were obtained with another human prostate cancer cell line, 22Rv1. More strikingly, we found that androgenic signaling is negatively regulated by VDR signaling. Also, molecular docking supported the inhibitory effect of 1,25(OH)₂ D₃ on AR signaling. Moreover, we found VDR signaling suppressed tumor progression by decreasing c-Myc expression and reducing the epithelial-mesenchymal transition (EMT). Additionally, 1,25(OH)₂ D₃ treatment significantly inhibited the 3D-tumor formation of LNCaP cells. Our results suggest that further molecular characterization of the action of VDR signaling in other cancer types such as estrogenic signal in breast cancer will provide important contributions to a better understanding of the roles of steroid hormone receptors in carcinogenesis processes.

The functional implication of ATF6α in castration-resistant prostate cancer cells

Stress in the endoplasmic reticulum (ER) may perturb proteostasis and activates the unfolded protein response (UPR). UPR activation is frequently observed in cancer cells and is believed to fuel cancer progression. Here, we report that one of the three UPR sensors, ATF6α, was associated with prostate cancer (PCa) development, while both genetic and pharmacological inhibition of ATF6α impaired the survival of castration-resistance PCa (CRPC) cells. Transcriptomic analyses identified the molecular pathways deregulated upon ATF6α depletion, and also discovered considerable disparity in global gene expression between ATF6α knockdown and Ceapin-A7 treatment. In addition, combined analyses of human CRPC bulk RNA-seq and single-cell RNA-seq (scRNA-seq) public datasets confirmed that CRPC tumors with higher ATF6α activity displayed higher androgen receptor (AR) activity, proliferative and neuroendocrine (NE) like phenotypes, as well as immunosuppressive features. Lastly, we identified a 14-gene set as ATF6α NE gene signature with encouraging prognostic power. In conclusion, our results indicate that ATF6α is correlated with PCa progression and is functionally relevant to CRPC cell survival. Both specificity and efficacy of ATF6α inhibitors require further refinement and evaluation.

Progesterone regulates the endoplasmic reticulum-associated degradation and Unfolded Protein Response axis by mimicking the androgenic stimulation in prostate cancer cells

BACKGROUND

Today, androgen receptor (AR)-mediated signaling mechanisms in prostate cancer are intensively studied. However, the roles of other steroid hormones in prostate cancer and their effects on androgenic signaling still remain a mystery. Recent studies focused on the androgen-mediated regulation of protein quality control mechanisms such as endoplasmic reticulum-associated degradation (ERAD) and unfolded protein response (UPR) in prostate cancer cells. Present study, we investigated the action of progesterone signaling on ERAD and UPR mechanisms and analyzed the crosstalk of progesterone signaling with androgenic signal in prostate cancer cells.

METHODS AND RESULTS

The mode of action of progesterone on ERAD, UPR and AR signaling in prostate cancer was investigated by cell culture studies using LNCaP and 22Rv1 cells. To this aim qRT-PCR, western-blotting assay, immunofluorescent microscopy, nuclear fractionation and bioinformatic analysis were used. Our results indicated that progesterone positively regulates mRNA and protein levels of ERAD components in LNCaP cells. Also, it induced the IRE⍺ and PERK branches of UPR signaling. Progesterone receptor antagonist effectively antagonized the progesterone-induced responses. We also had similar results in 22Rv1 cells. Also, we tested the effect of the pharmacologically reducing of IRE⍺ and PERK signaling on progesterone-induced ERAD. Additionally, we determined the presence of putative progesterone response elements (PREs) in the promoter regions of ERAD members by bioinformatic tool. More strikingly, we found progesterone regulates AR signaling by modulating the nuclear transactivation of AR.

CONCLUSION

Herein, we defined that progesterone hormone positively regulates ERAD and UPR mechanisms in prostate cancer cells and that progesterone contributes to the molecular biology of prostate cancer by regulating androgenic signaling. Mode of Action of Progesteron on Androgen sensitive prostate cancer cells.

Discovery of toxoflavin, a potent IRE1α inhibitor acting through structure-dependent oxidative inhibition

Inositol-requiring enzyme 1α (IRE1α) is the most conserved endoplasmic reticulum (ER) stress sensor with two catalytic domains, kinase and RNase, in its cytosolic portion. IRE1α inhibitors have been used to improve existing clinical treatments against various cancers. In this study we identified toxoflavin (TXF) as a new-type potent small molecule IRE1α inhibitor. We used luciferase reporter systems to screen compounds that inhibited the IRE1α-XBP1s signaling pathway. As a result, TXF was found to be the most potent IRE1α RNase inhibitor with an IC50 value of 0.226 μM. Its inhibitory potencies on IRE1α kinase and RNase were confirmed in a series of cellular and in vitro biochemical assays. Kinetic analysis showed that TXF caused time- and reducing reagent-dependent irreversible inhibition on IRE1α, implying that ROS might participate in the inhibition process. ROS scavengers decreased the inhibition of IRE1α by TXF, confirming that ROS mediated the inhibition process. Mass spectrometry analysis revealed that the thiol groups of four conserved cysteine residues (CYS-605, CYS-630, CYS-715 and CYS-951) in IRE1α were oxidized to sulfonic groups by ROS. In molecular docking experiments we affirmed the binding of TXF with IRE1α, and predicted its binding site, suggesting that the structure of TXF itself participates in the inhibition of IRE1α. Interestingly, CYS-951 was just near the docked site. In addition, the RNase IC50 and ROS production in vitro induced by TXF and its derivatives were negative correlated (r = -0.872). In conclusion, this study discovers a new type of IRE1α inhibitor that targets a predicted new alternative site located in the junction between RNase domain and kinase domain, and oxidizes conserved cysteine residues of IRE1α active sites to inhibit IRE1α. TXF could be used as a small molecule tool to study IRE1α's role in ER stress.

A compendium of Androgen Receptor Variant 7 target genes and their role in Castration Resistant Prostate Cancer

Persistent androgen receptor (AR) signalling is the main driver of prostate cancer (PCa). Truncated isoforms of the AR called androgen receptor variants (AR-Vs) lacking the ligand binding domain often emerge during treatment resistance against AR pathway inhibitors such as Enzalutamide. This review discusses how AR-Vs drive a more aggressive form of PCa through the regulation of some of their target genes involved in oncogenic pathways, enabling disease progression. There is a pressing need for the development of a new generation of AR inhibitors which can repress the activity of both the full-length AR and AR-Vs, for which the knowledge of differentially expressed target genes will allow evaluation of inhibition efficacy. This review provides a detailed account of the most common variant, AR-V7, the AR-V7 regulated genes which have been experimentally validated, endeavours to understand their relevance in aggressive AR-V driven PCa and discusses the utility of the downstream protein products as potential drug targets for PCa treatment.

Growth Hormone-Releasing Hormone in Endothelial Inflammation

The discovery of hypothalamic hormones propelled exciting advances in pharmacotherapy and improved life quality worldwide. Growth hormone-releasing hormone (GHRH) is a crucial element in homeostasis maintenance, and regulates the release of growth hormone from the anterior pituitary gland. Accumulating evidence suggests that this neuropeptide can also promote malignancies, as well as inflammation. Our review is focused on the role of that 44 - amino acid peptide (GHRH) and its antagonists in inflammation and vascular function, summarizing recent findings in the corresponding field. Preclinical studies demonstrate the protective role of GHRH antagonists against endothelial barrier dysfunction, suggesting that the development of those peptides may lead to new therapies against pathologies related to vascular remodeling (eg, sepsis, acute respiratory distress syndrome). Targeted therapies for those diseases do not exist.

The endoplasmic reticulum stress response in prostate cancer

In order to proliferate in unfavourable conditions, cancer cells can take advantage of the naturally occurring endoplasmic reticulum-associated unfolded protein response (UPR) via three highly conserved signalling arms: IRE1α, PERK and ATF6. All three arms of the UPR have key roles in every step of tumour progression: from cancer initiation to tumour growth, invasion, metastasis and resistance to therapy. At present, no cure for metastatic prostate cancer exists, as targeting the androgen receptor eventually results in treatment resistance. New research has uncovered an important role for the UPR in prostate cancer tumorigenesis and crosstalk between the UPR and androgen receptor signalling pathways. With an improved understanding of the mechanisms by which cancer cells exploit the endoplasmic reticulum stress response, targetable points of vulnerability can be uncovered.

Comparative Transcriptomics and Proteomics of Cancer Cell Lines Cultivated by Physiological and Commercial Media

Aiming to reduce the gap between in vitro and in vivo environment, a complex culture medium, Plasmax, was introduced recently, which includes nutrients and metabolites with concentrations normally found in human plasma. Herein, to study the influence of this medium on cellular behaviors, we utilized Plasmax to cultivate two cancer cell lines, including one breast cancer cell line, MDA-MB-231BR, and one brain cancer cell line, CRL-1620. Cancer cells were harvested and prepared for transcriptomics and proteomics analyses to assess the discrepancies caused by the different nutritional environments of Plasmax and two commercial media: DMEM, and EMEM. Total RNAs of cells were extracted using mammalian total RNA extract kits and analyzed by next-generation RNA sequencing; proteomics analyses were performed using LC-MS/MS. Gene oncology and pathway analysis were employed to study the affected functions. The cellular invasion and cell death were inhibited in MDA-MB-231BR cell line when cultured in Plasmax compared to DMEM and EMEM, whereas the invasion, migration and protein synthesis of CRL-1620 cell line were activated in Plasmax in relative to both commercial media. The expression changes of some proteins were more significant compared to their corresponding transcripts, indicating that Plasmax has more influence upon regulatory processes of proteins after translation. This work provides complementary information to the original study of Plasmax, aiming to facilitate the selection of appropriate media for in vitro cancer cell studies.

The Interplay between Finasteride-Induced Androgen Imbalance, Endoplasmic Reticulum Stress, Oxidative Stress, and Liver Disorders in Paternal and Filial Generation

Finasteride (Fin) causes androgen imbalance by inhibiting the conversion of testosterone (T) to its more active metabolite, dihydrotestosterone (DHT). Androgen receptors (AR) are present (e.g., in hepatocytes), which have well-developed endoplasmic reticulum (ERet). Cellular protein quality control is carried out by ERet in two paths: (i) unfolded protein response (UPR) and/or (ii) endoplasmic reticulum associated degradation (ERAD). ERet under continuous stress can generate changes in the UPR and can direct the cell on the pathway of life or death. It has been demonstrated that genes involved in ERet stress are among the genes controlled by androgens in some tissues. Oxidative stress is also one of the factors affecting the functions of ERet and androgens are one of the regulators of antioxidant enzyme activity. In this paper, we discuss/analyze a possible relationship between androgen imbalance in paternal generation with ERet stress and liver disorders in both paternal and filial generation. In our rat model, hyperglycemia and subsequent higher accumulation of hepatic glycogen were observed in all filial generation obtained from females fertilized by Fin-treated males (F1:Fin). Importantly, genes encoding enzymes involved in glucose and glycogen metabolism have been previously recognized among UPR targets.

Ascendancy of unfolded protein response over glioblastoma: estimating progression, prognosis and survival

Glioblastoma (GBM) is presented with a poor prognosis. The endoplasmic reticulum stress (ERS) has been implicated as a major contributor to disease progression and chemoresistance in GBM. Triggering ERS by chemical agents or genetic modulations is identified as some of the reasons for regulating gene expression and the pathogenesis of GBM. ERS initiates unfolded protein response (UPR), an integrated system useful in restoring homeostasis or inducing apoptosis. Modulation of UPR might have positive outcomes in GBM treatment as UPR inducers have been shown to alter cell survival and migration. In the current review, we have utilized GSE7806, a publicly available dataset from Gene Expression Omnibus (GEO), to evaluate the genes expressed during 6.5 hr and 18 hr, which can be comparable to the early and late-onset of the disease. Subsequently, we have elucidated the prognosis and survival information whilst the expression of these genes in the GBM was noted in previous studies. This is the first of its kind review summarizing the most recent gene information correlating UPR and GBM.

Calreticulin Identified as One of the Androgen Response Genes That Trigger Full Regeneration of the Only Capable Mammalian Organ, the Deer Antler

Deer antlers are male secondary sexual characters that develop to become bone; they are unique appendages that, once lost, can fully regenerate from the permanent bony protuberances or pedicles. Pedicle periosteum (PP) is the tissue that gives rise to the regenerating antlers with three differentiation stages, namely, dormant (DoPP), potentiated (PoPP), and activated (AcPP). Thus far, the transition from the PoPP to the AcPP has not been studied. Our results showed that the AcPP cells maintained their original stem cell features by expressing mesenchymal stem cell (MSC) markers CD73, CD90, and CD105, although they had entered the proliferation mode. The differentially expressed genes (DEGs) in the AcPP compared with those of the PoPP were mainly involved in protein processing, cell cycle, and calcium signaling pathways. Calreticulin (CALR), an androgen response gene, was significantly differentially upregulated in the AcPP cells, and its expression level was negatively regulated by androgens, in contrast to the currently known model systems where all regulation is positive. The downregulation of CALR expression in the AcPP cells in vitro inhibited cell proliferation, induced apoptosis, and inhibited cell cycle progression at G1-S transition. Therefore, CALR is likely a downstream mediator of androgen hormones for triggering initiation of antler regeneration. We believe that the identification of CALR has not only discovered "one critical piece" of the "jigsaw puzzle" in the initiation of antler regeneration but also helps in revealing the mechanism underlying this unique mammalian epimorphic regeneration and has also opened a new avenue for the study of the nature of CALR regulation by androgen (putative binding partners), thus facilitating the identification of potential molecule(s) for investigation as targets for clinical evaluation.

ATF6α promotes prostate cancer progression by enhancing PLA2G4A-mediated arachidonic acid metabolism and protecting tumor cells against ferroptosis

BACKGROUND

Despite the clinical success of androgen receptor (AR)-targeted therapies, prostate cancer (PCa) inevitably progresses to castration-resistant prostate cancer (CRPC). Transcription factor 6 α (ATF6α), an effector of the unfolded protein response (UPR) that modulates the cellular response to endoplasmic reticulum (ER) stress, has been linked to tumor development, metastasis, and relapse. However, the role of ATF6α in CRPC remains unclear.

METHODS

The effect of ATF6α on the CRPC-like phenotype in PCa cells was evaluated by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carb-Oxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt (MTS), 5-Bromo-2-deoxyUridine (BrdU) incorporation analysis, and cell death assay. Mechanistically, bioinformatic analysis was utilized to evaluate the potential of PLA2G4A as the target of ATF6α. Moreover, Western blot analysis, real-time polymerase chain reaction, chromatin immunoprecipitation, arachidonic acid (AA), and prostaglandin E2 (PGE2) assays were performed to identify the regulatory effect of ATF6α on PLA2G4A.

RESULTS

In this study, we found that the increase of ATF6α expression in response to androgen deprivation generates PCa cells with a CRPC-like phenotype. PCa cells with high levels of ATF6α expression are resistant to ferroptosis, and genetic and pharmacological inhibition of ATF6α could, therefore, promote the ferroptotic death of tumor cells and delay PCa progression. Molecular analyses linked ATF6α regulation of ferroptosis to the PLA2G4A-mediated release of AA and the resulting increase in PGE2 production, the latter of which acts as an antiferroptotic factor.

CONCLUSIONS

This study defines ATF6α as a novel antiferroptotic regulator that exacerbates PCa progression. In addition, our data establish ATF6α-PLA2G4A signaling as an important pathological pathway in PCa, and targeting this pathway may be a novel treatment strategy.

A novel small-molecule activator of unfolded protein response suppresses castration-resistant prostate cancer growth

Androgen receptor-targeted therapy improves survival in castration-resistant prostate cancer (CRPC). However, almost all patients with CRPC eventually develop secondary resistance to these drugs. Therefore, alternative therapeutic approaches for incurable metastatic CRPC are urgently needed. Unfolded protein response (UPR) is regarded as a cytoprotective mechanism that removes misfolded proteins in rapidly proliferating tumor cells. However, acute activation of the UPR directly leads to tumor cell death. This study has shown that WJ-644A, a novel small molecule activator of UPR, potently inhibited the proliferation of prostate cancer cells and caused tumor regression with a good safety profile in multiple animal models. Mechanistically, we have identified that WJ-644A induced cell methuosis and autophagy upon UPR activation. Our study not only identifies the UPR as an actionable target for CRPC treatment, but also establishes WJ-644A as a novel UPR activator that has potential therapeutic value for CRPC.

XBP1s promotes the development of lung adenocarcinoma via the p‑JNK MAPK pathway

Spliced X-box binding protein 1 (XBP1s) has been reported to participate in the pathogenesis of numerous types of cancer; however, whether XBP1s plays a role in lung cancer remains to be elucidated. In the present study, bioinformatics analysis was performed to determine the mRNA expression level of XBP1 in lung cancer and adjacent normal tissues. Gene Ontology terms, pathway enrichment and Pearson's correlation analysis were performed to investigate the possible mechanism involved. Western blot and reverse transcription-quantitative PCR were performed to quantify the protein and mRNA expression level of target proteins, respectively. Small interfering RNA or overexpression plasmid were used to knockdown or overexpress the expression level of XBP1s. EdU staining, colony formation, Cell Counting Kit-8, Transwell and wound healing assays, and flow cytometry were performed to detect the proliferation, colony forming ability, cell viability, migration and invasion ability, and the apoptosis rate. The results showed that the mRNA and protein expression level of XBP1 was higher in tumor tissues compared with that in adjacent normal tissues using data from the TIMER2.0, ONCOMINE and UALCAN online databases. In addition, the mRNA expression level of XBP1 was also associated with clinical features, including age, smoking habit, individual cancer stage and nodal metastasis status. In the in vitro experiments, the mRNA and protein expression level of XBP1s was increased in the A549 cell line compared with that in the human bronchial epithelial (HBE), H1299, PC9 and H460 cell lines. Hypoxia further increased the protein expression level of XBP1s in the A549 cell line. Knockdown of XBP1s expression in the A549 cell line resulted in decreased proliferation, colony formation, cell viability, migration and invasion, and increased apoptosis. By contrast, overexpressing XBP1s in the HBE cell line led to the opposite results. To investigate the mechanism involved, proteins associated with XBP1 were analyzed using the LinkedOmics database. Pathway enrichment revealed the MAPK pathway to be the possible XBP1 downstream target. Furthermore, Pearson's correlation and western blot analyses verified that phosphorylated (p)-JNK rather than p-ERK or p-p38 was the downstream effector of XBP1s. Phosphorylation of JNK was decreased when XBP1s expression was knocked down in the A549 cell line under normoxic and hypoxic conditions. Inhibiting p-JNK with SP600125 reversed the increased prosurvival effects caused by XBP1s overexpression. The results from the present study suggest that XBP1s/p-JNK function as a prosurvival factors in the A549 cell line and could be a potential target for the treatment of lung adenocarcinoma.

Cellular stress responses and metabolic reprogramming in cancer progression and dormancy

Recurrent disease after prolonged cancer dormancy is a major cause of cancer associated mortality, yet many of the mechanisms that are engaged to initiate dormancy as well as later recurrence remain incompletely understood. It is known that cancer cells initiate adaptation mechanisms to adapt tightly regulated cellular processes to non-optimal growth environments; Recent investigations have begun to elucidate the contribution of these mechanisms to malignant progression, with intriguing studies now defining cellular stress as a key contributor to the development and maintenance of cancer dormancy. This review will focus on our current understanding of stress responses facilitating malignant cell adaptation and metabolic reprogramming to establish cancer dormancy.

TXNIP Links Anticipatory Unfolded Protein Response to Estrogen Reprogramming Glucose Metabolism in Breast Cancer Cells

Estrogen and estrogen receptor (ER) play a fundamental role in breast cancer. To support the rapid proliferation of ER+ breast cancer cells, estrogen increases glucose uptake and reprograms glucose metabolism. Meanwhile, estrogen/ER activates the anticipatory unfolded protein response (UPR) preparing cancer cells for the increased protein production required for subsequent cell proliferation. Here, we report that thioredoxin-interacting protein (TXNIP) is an important regulator of glucose metabolism in ER+ breast cancer cells, and estrogen/ER increases glucose uptake and reprograms glucose metabolism via activating anticipatory UPR and subsequently repressing TXNIP expression. In 2 widely used ER+ breast cancer cell lines, MCF7 and T47D, we showed that MCF7 cells express high TXNIP levels and exhibit mitochondrial oxidative phosphorylation (OXPHOS) phenotype, while T47D cells express low TXNIP levels and display aerobic glycolysis (Warburg effect) phenotype. Knockdown of TXNIP promoted glucose uptake and Warburg effect, while forced overexpression of TXNIP inhibited glucose uptake and Warburg effect. We further showed that estrogen represses TXNIP expression and activates UPR sensor inositol-requiring enzyme 1 (IRE1) via ER in the breast cancer cells, and IRE1 activity is required for estrogen suppression of TXNIP expression and estrogen-induced cell proliferation. Our study suggests that TXNIP is involved in estrogen-induced glucose uptake and metabolic reprogramming in ER+ breast cancer cells and links anticipatory UPR to estrogen reprogramming glucose metabolism.

Androgen receptor-mediated transcriptional repression targets cell plasticity in prostate cancer

Androgen receptor (AR) signaling remains the key therapeutic target in the management of hormone‐naïve‐advanced prostate cancer (PCa) and castration‐resistant PCa (CRPC). Recently, landmark molecular features have been reported for CRPC, including the expression of constitutively active AR variants that lack the ligand‐binding domain. Besides their role in CRPC, AR variants lead to the expression of genes involved in tumor progression. However, little is known about the specificity of their mode of action compared with that of wild‐type AR (AR‐WT). We performed AR transcriptome analyses in an androgen‐dependent PCa cell line as well as cross‐analyses with publicly available RNA‐seq datasets and established that transcriptional repression capacity that was marked for AR‐WT was pathologically lost by AR variants. Functional enrichment analyses allowed us to associate AR‐WT repressive function to a panel of genes involved in cell adhesion and epithelial‐to‐mesenchymal transition. So, we postulate that a less documented AR‐WT normal function in prostate epithelial cells could be the repression of a panel of genes linked to cell plasticity and that this repressive function could be pathologically abrogated by AR variants in PCa.

Single-cell analysis reveals androgen receptor regulates the ER-to-Golgi trafficking pathway with CREB3L2 to drive prostate cancer progression

Androgen receptor (AR) plays a central role in driving prostate cancer (PCa) progression. How AR promotes this process is still not completely clear. Herein, we used single-cell transcriptome analysis to reconstruct the transcriptional network of AR in PCa. Our work shows AR directly regulates a set of signature genes in the ER-to-Golgi protein vesicle-mediated transport pathway. The expression of these genes is required for maximum androgen-dependent ER-to-Golgi trafficking, cell growth, and survival. Our analyses also reveal the signature genes are associated with PCa progression and prognosis. Moreover, we find inhibition of the ER-to-Golgi transport process with a small molecule enhanced antiandrogen-mediated tumor suppression of hormone-sensitive and insensitive PCa. Finally, we demonstrate AR collaborates with CREB3L2 in mediating ER-to-Golgi trafficking in PCa. In summary, our findings uncover a critical role for dysregulation of ER-to-Golgi trafficking expression and function in PCa progression, provide detailed mechanistic insights for how AR tightly controls this process, and highlight the prospect of targeting the ER-to-Golgi pathway as a therapeutic strategy for advanced PCa.

Involvement of Kisspeptin in androgen-induced hypothalamic endoplasmic reticulum stress and its rescuing effect in PCOS rats

Endoplasmic reticulum (ER) stress, with adaptive unfolded protein response (UPR), is a key link between obesity, insulin resistance and type 2 diabetes, all of which are often present in the most common endocrine-metabolic disorder in women of reproductive age, polycystic ovary syndrome (PCOS), which is characterized with hyperandrogenism. However, the link between excess androgen and Endoplasmic reticulum (ER) stress/insulin resistance in patients with polycystic ovary syndrome (PCOS) is unknown. An unexpected role of kisspeptin was reported in the regulation of UPR pathways and its involvement in the androgen-induced ER stress in hypothalamic neuronal cells. To evaluate the relationship of kisspeptin and ER stress, we detected Kisspeptin and other factors in blood plasm of PCOS patients, rat models and hypothalamic neuronal cells. We detected higher testosterone and lower kisspeptin levels in the plasma of PCOS than that in non-PCOS women. We established a PCOS rat model by dihydrotestosterone (DHT) chronic exposure, and observed significantly downregulated kisspeptin expression and activated UPR pathways in PCOS rat hypothalamus compared to that in controls. Inhibition or knockdown of kisspeptin completely mimicked the enhancing effect of DHT on UPR pathways in a hypothalamic neuronal cell line, GT1-7. Kp10, the most potent peptide of kisspeptin, effectively reversed or suppressed the activated UPR pathways induced by DHT or thapsigargin, an ER stress activator, in GT1-7 cells, as well as in the hypothalamus in PCOS rats. Similarly, Kisspeptin attenuated thapsigargin-induced Ca²⁺ response and the DHT- induced insulin resistance in GT1-7 cells. Collectively, the present study has revealed an unexpected protective role of kisspeptin against ER stress and insulin resistance in the hypothalamus and provided a new treatment strategy targeting hypothalamic ER stress and insulin resistance with kisspeptin as a potential therapeutic agent.

IRE1α Expedites the Progression of Castration-Resistant Prostate Cancers via the Positive Feedback Loop of IRE1α/IL-6/AR

Castration-resistant prostate cancer (CRPC) is the lethal form of prostate cancer (PCa), and the underlying molecular mechanism has not been fully elucidated. Inositol requiring enzyme 1 alpha (IRE1α), a key regulator of unfolded protein response (UPR), is intimately associated with PCa progression. However, whether IRE1α is implicated in CRPC development remains unknown. Here, we showed that IRE1α expression was significantly increased in CRPC tissues and high-grade PCa tissues. Overexpression of IRE1α promoted PCa cell proliferation under the androgen deficiency condition in vitro and in vivo. Mechanistically, increased IRE1α expression induced IL-6 secretion via the IRE1α/XBP-1s signal pathway. IRE1α-induced IL-6 activated androgen receptor (AR), and the activation of AR by IL-6, in turn, promoted IRE1α expression. IRE1α formed a positive feedback loop with IL-6 and AR to promote prostate cancer cell proliferation under the androgen-deficient condition. In clinical PCa samples, high IRE1α expression correlated with elevated IL-6 and increased PSA expression. Our findings demonstrated a novel mechanism of CRPC progression and suggest targeting IRE1α may be a potential target for the prevention and treatment of CRPC.

Regulation of mRNA Translation by Hormone Receptors in Breast and Prostate Cancer

Breast and prostate cancer are the second and third leading causes of death amongst all cancer types, respectively. Pathogenesis of these malignancies is characterised by dysregulation of sex hormone signalling pathways, mediated by the estrogen receptor-α (ER) in breast cancer and androgen receptor (AR) in prostate cancer. ER and AR are transcription factors whose aberrant function drives oncogenic transcriptional programs to promote cancer growth and progression. While ER/AR are known to stimulate cell growth and survival by modulating gene transcription, emerging findings indicate that their effects in neoplasia are also mediated by dysregulation of protein synthesis (i.e., mRNA translation). This suggests that ER/AR can coordinately perturb both transcriptional and translational programs, resulting in the establishment of proteomes that promote malignancy. In this review, we will discuss relatively understudied aspects of ER and AR activity in regulating protein synthesis as well as the potential of targeting mRNA translation in breast and prostate cancer.

Stress-Mediated Reprogramming of Prostate Cancer One-Carbon Cycle Drives Disease Progression

One-carbon (1C) metabolism has a key role in metabolic programming with both mitochondrial (m1C) and cytoplasmic (c1C) components. Here we show that activating transcription factor 4 (ATF4) exclusively activates gene expression involved in m1C, but not the c1C cycle in prostate cancer cells. This includes activation of methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) expression, the central player in the m1C cycle. Consistent with the key role of m1C cycle in prostate cancer, MTHFD2 knockdown inhibited prostate cancer cell growth, prostatosphere formation, and growth of patient-derived xenograft organoids. In addition, therapeutic silencing of MTHFD2 by systemically administered nanoliposomal siRNA profoundly inhibited tumor growth in preclinical prostate cancer mouse models. Consistently, MTHFD2 expression is significantly increased in human prostate cancer, and a gene expression signature based on the m1C cycle has significant prognostic value. Furthermore, MTHFD2 expression is coordinately regulated by ATF4 and the oncoprotein c-MYC, which has been implicated in prostate cancer. These data suggest that the m1C cycle is essential for prostate cancer progression and may serve as a novel biomarker and therapeutic target. SIGNIFICANCE: These findings demonstrate that the mitochondrial, but not cytoplasmic, one-carbon cycle has a key role in prostate cancer cell growth and survival and may serve as a biomarker and/or therapeutic target.

Modulating the unfolded protein response with ONC201 to impact on radiation response in prostate cancer cells

Prostate cancer (PCa) is the most common non-cutaneous cancer in men and a notable cause of cancer mortality when it metastasises. The unfolded protein response (UPR) can be cytoprotective but when acutely activated can lead to cell death. In this study, we sought to enhance the acute activation of the UPR using radiation and ONC201, an UPR activator. Treating PCa cells with ONC201 quickly increased the expression of all the key regulators of the UPR and reduced the oxidative phosphorylation, with cell death occurring 72 h later. We exploited this time lag to sensitize prostate cancer cells to radiation through short-term treatment with ONC201. To understand how priming occurred, we performed RNA-Seq analysis and found that ONC201 suppressed the expression of cell cycle and DNA repair factors. In conclusion, we have shown that ONC201 can prime enhanced radiation response.

An Emerging Role for the Unfolded Protein Response in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is the most common form of pancreatic cancer and one of the leading causes of cancer-associated deaths in the world. It is characterised by dismal response rates to conventional therapies. A major challenge in treatment strategies for PDAC is the presence of a dense stroma that surrounds the tumour cells, shielding them from treatment. This unique tumour microenvironment is fuelled by paracrine signalling between pancreatic cancer cells and supporting stromal cell types including the pancreatic stellate cells (PSC). While our molecular understanding of PDAC is improving, there remains a vital need to develop effective, targeted treatments. The unfolded protein response (UPR) is an elaborate signalling network that governs the cellular response to perturbed protein homeostasis in the endoplasmic reticulum (ER) lumen. There is growing evidence that the UPR is constitutively active in PDAC and may contribute to the disease progression and the acquisition of resistance to therapy. Given the importance of the tumour microenvironment and cytokine signalling in PDAC, and an emerging role for the UPR in shaping the tumour microenvironment and in the regulation of cytokines in other cancer types, this review explores the importance of the UPR in PDAC biology and its potential as a therapeutic target in this disease.

Obesity, Diabetes and COVID-19: An Infectious Disease Spreading From the East Collides With the Consequences of an Unhealthy Western Lifestyle

The pandemic of COVID-19, caused by the coronavirus, SARS-CoV-2, has had a global impact not seen for an infectious disease for over a century. This acute pandemic has spread from the East and has been overlaid onto a slow pandemic of metabolic diseases of obesity and diabetes consequent from the increasing adoption of a Western-lifestyle characterized by excess calorie consumption with limited physical activity. It has become clear that these conditions predispose individuals to a more severe COVID-19 with increased morbidity and mortality. There are many features of diabetes and obesity that may accentuate the clinical response to SARS-CoV-2 infection: including an impaired immune response, an atherothrombotic state, accumulation of advanced glycation end products and a chronic inflammatory state. These could prime an exaggerated cytokine response to viral infection, predisposing to the cytokine storm that triggers progression to septic shock, acute respiratory distress syndrome, and multi-organ failure. Infection leads to an inflammatory response and tissue damage resulting in increased metabolic activity and an associated increase in the mechanisms by which cells ingest and degrade tissue debris and foreign materials. It is becoming clear that viruses have acquired an ability to exploit these mechanisms to invade cells and facilitate their own life-cycle. In obesity and diabetes these mechanisms are chronically activated due to the deteriorating metabolic state and this may provide an increased opportunity for a more profound and sustained viral infection.

Darolutamide antagonizes androgen signaling by blocking enhancer and super-enhancer activation

Prostate cancer (PCa) is one of the most frequent tumor types in the male Western population. Early-stage PCa and late-stage PCa are dependent on androgen signaling, and inhibitors of the androgen receptor (AR) axis represent the standard therapy. Here, we studied in detail the global impact of darolutamide, a newly approved AR antagonist, on the transcriptome and AR-bound cistrome in two PCa cell models. Darolutamide strongly depleted the AR from gene regulatory regions and abolished AR-driven transcriptional signaling. Enhancer activation was blocked at the chromatin level as evaluated by H3K27 acetylation (H3K27ac), H3K4 monomethylation (H3K4me1), and FOXA1, MED1, and BRD4 binding. We identified genomic regions with high affinities for the AR in androgen-stimulated, but also in androgen-depleted conditions. A similar AR affinity pattern was observed in healthy and PCa tissue samples. High FOXA1, BRD4, H3K27ac, and H3K4me1 levels were found to mark regions showing AR binding in the hormone-depleted setting. Conversely, low FOXA1, BRD4, and H3K27ac levels were observed at regulatory sites that responded strongly to androgen stimulation, and AR interactions at these sites were blocked by darolutamide. Beside marked loss of AR occupancy, FOXA1 recruitment to chromatin was also clearly reduced after darolutamide treatment. We furthermore identified numerous androgen-regulated super-enhancers (SEs) that were associated with hallmark androgen and cell proliferation-associated gene sets. Importantly, these SEs are also active in PCa tissues and sensitive to darolutamide treatment in our models. Our findings demonstrate that darolutamide is a potent AR antagonist blocking genome-wide AR enhancer and SE activation, and downstream transcription. We also show the existence of a dynamic AR cistrome that depends on the androgen levels and on high AR affinity regions present in PCa cell lines and also in tissue samples.

Pharmacological Targeting of IRE1 in Cancer

IRE1α (inositol requiring enzyme 1 alpha) is one of the main transducers of the unfolded protein response (UPR). IRE1α plays instrumental protumoral roles in several cancers, and high IRE1α activity has been associated with poorer prognoses. In this context, IRE1α has been identified as a potentially relevant therapeutic target. Pharmacological inhibition of IRE1α activity can be achieved by targeting either the kinase domain or the RNase domain. Herein, the recent advances in IRE1α pharmacological targeting is summarized. We describe the identification and optimization of IRE1α inhibitors as well as their mode of action and limitations as anticancer drugs. The potential pitfalls and challenges that could be faced in the clinic, and the opportunities that IRE1α modulating strategies may present are discussed.

Peptidomimetic-based identification of FDA-approved compounds inhibiting IRE1 activity

Inositol-requiring enzyme 1 (IRE1) is a bifunctional serine/threonine kinase and endoribonuclease that is a major mediator of the unfolded protein response (UPR) during endoplasmic reticulum (ER) stress. Tumour cells experience ER stress due to adverse environmental cues such as hypoxia or nutrient shortage and high metabolic/protein-folding demand. To cope with those stresses, cancer cells utilise IRE1 signalling as an adaptive mechanism. Here, we report the discovery of the FDA-approved compounds methotrexate, cefoperazone, folinic acid and fludarabine phosphate as IRE1 inhibitors. These were identified through a structural exploration of the IRE1 kinase domain using IRE1 peptide fragment docking and further optimisation and pharmacophore development. The inhibitors were verified to have an impact on IRE1 activity in vitro and were tested for their ability to sensitise human cell models of glioblastoma multiforme (GBM) to chemotherapy. We show that all molecules identified sensitise glioblastoma cells to the standard-of-care chemotherapy temozolomide (TMZ).

MYC and the unfolded protein response in cancer: synthetic lethal partners in crime?

The transcription factors of the MYC family play pivotal roles in the initiation and progression of human cancers. High oncogenic level of MYC invades low‐affinity sites and enhancer sequences, which subsequently alters the transcriptome, causes metabolic imbalance, and induces stress response. The endoplasmic reticulum (ER) not only plays a central role in maintaining proteostasis, but also contributes to other key biological processes, including Ca²⁺ metabolism and the synthesis of lipids and glucose. Stress conditions, such as shortage in glucose or oxygen and disruption of Ca²⁺ homeostasis, may perturb proteostasis and induce the unfolded protein response (UPR), which either restores homeostasis or triggers cell death. Crucial roles of ER stress and UPR signaling have been implicated in various cancers, from oncogenesis to treatment response. Here, we summarize the current knowledge on the interaction between MYC and UPR signaling, and its contribution to cancer development. We also discuss the potential of targeting key UPR signaling nodes as novel synthetic lethal strategies in MYC‐driven cancers.

Mechanism of inositol-requiring enzyme 1-alpha inhibition in endoplasmic reticulum stress and apoptosis in ovarian cancer cells

IRE1α endonuclease is a key regulator of endoplasmic reticulum (ER) stress that controls cell survival/apoptosis in cancers. Inhibition of IRE1α endonuclease leads to decreased splice XBP1 which decreases cell proliferation and increases cell death in cancer cells. Therefore, this study investigated the effects and mechanism of STF-083010 (an IRE1α inhibitor) on the cell growth/apoptosis of ovarian malignant cells via the XBP1-CHOP-Bim pathway following the induction of ER stress (ERS). ERS in OVCAR3 and SKOV3 cells was measured using Thioflavin T staining. The expression of ER stress response genes was evaluated by QRT-PCR. The levels of XBP1(s), PERK, phospho-PERK, p-PP2A, ATF4, BIP/GRP78, CHOP, and Bim proteins were evaluated using western blotting. Cell viability and apoptosis in STF-083010 and Tunicamycin (Tm) co-treated cells were assessed using BrdU, MTT, Annexin V-FITC/PI staining, and caspases-12 and -3 activity assays. The results showed increased XBP1, CHOP, and ATF-4 mRNA expression levels as well as high protein aggregation in STF-083010 and Tm co-treated cells. The IRE1α inhibitor down-regulated sXBP1 and BIP proteins, while XBP-1, p-PERK, ATF-4, CHOP, and Bim proteins were up-regulated. STF-083010 reduced cell proliferation and induced apoptosis through the activation of caspases-12 and -3 and Bax/Bcl-2 protein expression. In summary, the present data revealed the effects of STF-083010 in ER stress and apoptosis as well as signaling via XBP1/CHOP/Bim mediators. Thus, STF-083010 is proposed as a new target for the control of ERS in ovarian cancer cells.