Transcriptional regulation of core autophagy and lysosomal genes by the androgen receptor promotes prostate cancer progression

PGC-1α and ERRα in patients with endometrial cancer: a translational study for predicting myometrial invasion

BACKGROUND

PGC-1α and ERRα are closely related to tumor formation and progression. However, the mechanism underlying the involvement of PGC-1α/ERRα in regulating invasion and migration in endometrial cancer remains to be explored.

RESULTS

Elevated levels of PGC-1α and ERRα were associated with advanced myometrial invasion, and PGC-1α and Vimentin expression was related to the depth of myometrial invasion in premenopausal endometrial cancer. Silencing of PGC-1α reduced ERRα activation and inhibited epithelial-mesenchymal-transition phenotypes, resulting in significant inhibition of invasion and migration. Overexpression of ERRα led to enhanced PGC-1α expression and increased activity of TFEB, promoting epithelial-mesenchymal-transition in endometrial cancer cells.

CONCLUSIONS

PGC-1α and ERRα induce the epithelial-mesenchymal-transition therefore invasion and migration in endometrial cancer, and may be novel biomarkers to predict the risk of advanced myometrial invasion.

METHODS

PGC-1α, ERRα, and vimentin expression was analyzed in tissue microarrays using immunohistochemistry. PGC-1α and ERRα expression in endometrial cancer cell lines was investigated using quantitative PCR and western blotting analyses after infection with lentivirus-mediated small interfering RNA (siRNA) targeting PGC-1α (siRNA-PGC-1α) or overexpressing ERRα. E-cadherin and vimentin levels were determined using western blotting and cell immunouorescence analyses. Cell migration and invasiveness were evaluated using scratch and trans-well chamber assays.

Alternative splicing regulation by the androgen receptor in prostate cancer cells

The androgen receptor (AR) is a transcription factor that drives prostate cancer (PCa) by modulating the expression of thousands of genes to promote proliferation and survival and to reprogram metabolism. However, how AR activation controls alternative splicing is mostly unknown. Our objective was to define its role in the transcriptome-wide regulation of alternative splicing. Three human PCa models-LNCaP, LAPC4, and 22Rv1 cells-were treated with and without androgens, and RNA was purified for deep-sequencing analyses (RNA-seq). Several bioinformatic tools were then used to study alternative splicing. We demonstrate that in the absence of androgens, alternative splicing complexity is similar among AR-positive PCa cells, with 48 % of all transcripts having various levels of alternative splicing. We also describe alternative splicing differences among cell lines, such as specific splicing of AR, REST, TSC2, and CTBP1. Interestingly, AR activation changed the alternative splicing of thousands of genes in all the PCa cell lines tested. Overlap between AR-sensitive alternative splicing events revealed that genes linked to cell metabolism are major targets for this specific modulation. These genes encode metabolic enzymes such as the prostate-specific membrane antigen, encoded by FOLH1, and the malate dehydrogenase 1 (MDH1). Overall, our study presents a comprehensive analysis of the PCa cell transcriptome and its modulation by AR, revealing a significant enrichment of metabolic genes in this AR-dependent regulation of alternative splicing.

Long non‑coding RNA growth arrest‑specific 5 (GAS5) acts as a tumor suppressor by promoting autophagy in breast cancer

Growth arrest-specific 5 (GAS5) is a known tumor suppressor which negatively regulates cell survival and malignancy in several cancer cell types. The present study aimed to establish the correlation between GAS5 and unc-51 like autophagy activating kinase (ULK)1/2, two key regulators of autophagy initiation in breast cancer (BC). To address this, expression levels of these genes were quantitively analyzed in BC clinical samples by performing reverse transcription-quantitative PCR. GAS5 was downregulated in BC clinical samples compared with adjacent samples and was positively correlated with ULK1/2. Detection methods including cell cycle analysis, annexin V-FITC/PI double staining and flow cytometry analysis, Transwell cell invasion assay, transfection and western blotting were used for BC cells. In MCF-7 cells, it was also observed that overexpression of GAS5 upregulated ULK1/2 protein levels without disturbing other autophagy initiation-associated proteins and inhibited cell proliferation, invasion and tumor formation. These effects were reversed by blocking autophagy with 3-methyladenine (3-MA). These results demonstrated that the suppressive effects of overexpressed GAS5 were mediated via autophagy induction, at least in part. Overexpression of GAS5 induced chemoresistance to cisplatin, which was not reversed by 3-MA-mediated inhibition of autophagy, indicating that GAS5 promotes chemosensitivity in an autophagy-independent manner. Collectively, these results indicated that GAS5 contributes to the pathogenesis of BC potentially by promoting autophagy. However, the mechanism by which GAS5 functions as a tumor suppressor in an autophagy-independent manner remains unknown.

Cell-Clearing Systems Bridging Repeat Expansion Proteotoxicity and Neuromuscular Junction Alterations in ALS and SBMA

The coordinated activities of autophagy and the ubiquitin proteasome system (UPS) are key to preventing the aggregation and toxicity of misfold-prone proteins which manifest in a number of neurodegenerative disorders. These include proteins which are encoded by genes containing nucleotide repeat expansions. In the present review we focus on the overlapping role of autophagy and the UPS in repeat expansion proteotoxicity associated with chromosome 9 open reading frame 72 (C9ORF72) and androgen receptor (AR) genes, which are implicated in two motor neuron disorders, amyotrophic lateral sclerosis (ALS) and spinal-bulbar muscular atrophy (SBMA), respectively. At baseline, both C9ORF72 and AR regulate autophagy, while their aberrantly-expanded isoforms may lead to a failure in both autophagy and the UPS, further promoting protein aggregation and toxicity within motor neurons and skeletal muscles. Besides proteotoxicity, autophagy and UPS alterations are also implicated in neuromuscular junction (NMJ) alterations, which occur early in both ALS and SBMA. In fact, autophagy and the UPS intermingle with endocytic/secretory pathways to regulate axonal homeostasis and neurotransmission by interacting with key proteins which operate at the NMJ, such as agrin, acetylcholine receptors (AChRs), and adrenergic beta2 receptors (B2-ARs). Thus, alterations of autophagy and the UPS configure as a common hallmark in both ALS and SBMA disease progression. The findings here discussed may contribute to disclosing overlapping molecular mechanisms which are associated with a failure in cell-clearing systems in ALS and SBMA.

Mechanisms of Action of Autophagy Modulators Dissected by Quantitative Systems Pharmacology Analysis

Autophagy plays an essential role in cell survival/death and functioning. Modulation of autophagy has been recognized as a promising therapeutic strategy against diseases/disorders associated with uncontrolled growth or accumulation of biomolecular aggregates, organelles, or cells including those caused by cancer, aging, neurodegeneration, and liver diseases such as α1-antitrypsin deficiency. Numerous pharmacological agents that enhance or suppress autophagy have been discovered. However, their molecular mechanisms of action are far from clear. Here, we collected a set of 225 autophagy modulators and carried out a comprehensive quantitative systems pharmacology (QSP) analysis of their targets using both existing databases and predictions made by our machine learning algorithm. Autophagy modulators include several highly promiscuous drugs (e.g., artenimol and olanzapine acting as activators, fostamatinib as an inhibitor, or melatonin as a dual-modulator) as well as selected drugs that uniquely target specific proteins (~30% of modulators). They are mediated by three layers of regulation: (i) pathways involving core autophagy-related (ATG) proteins such as mTOR, AKT, and AMPK; (ii) upstream signaling events that regulate the activity of ATG pathways such as calcium-, cAMP-, and MAPK-signaling pathways; and (iii) transcription factors regulating the expression of ATG proteins such as TFEB, TFE3, HIF-1, FoxO, and NF-κB. Our results suggest that PKA serves as a linker, bridging various signal transduction events and autophagy. These new insights contribute to a better assessment of the mechanism of action of autophagy modulators as well as their side effects, development of novel polypharmacological strategies, and identification of drug repurposing opportunities.

Sex differences in autophagy-mediated diseases: toward precision medicine

Nearly all diseases in humans, to a certain extent, exhibit sex differences, including differences in the onset, progression, prevention, therapy, and prognosis of diseases. Accumulating evidence shows that macroautophagy/autophagy, as a mechanism for development, differentiation, survival, and homeostasis, is involved in numerous aspects of sex differences in diseases such as cancer, neurodegeneration, and cardiovascular diseases. Advances in our knowledge regarding sex differences in autophagy-mediated diseases have enabled an understanding of their roles in human diseases, although the underlying molecular mechanisms of sex differences in autophagy remain largely unexplored. In this review, we discuss current advances in our insight into the biology of sex differences in autophagy and disease, information that will facilitate precision medicine.Abbreviations: AD: Azheimer disease; AMBRA1: autophagy and beclin 1 regulator 1; APP: amyloid beta precursor protein; AR: androgen receptor; AMPK: AMP-activated protein kinase; ATG: autophagy related; ATP6AP2: ATPase H+ transporting accessory protein 2; BCL2L1: BCL2 like 1; BECN1: beclin 1; CTSD: cathepsin D; CYP19A1: cytochrome P450 family 19 subfamily A member 1; DSD: disorders of sex development; eALDI: enhancer alternate long-distance initiator; ESR1: estrogen receptor 1; ESR2: estrogen receptor 2; FYCO1: FYVE and coiled-coil domain autophagy adaptor 1; GABARAP: GABA type A receptor-associated protein; GLA: galactosidase alpha; GTEx: genotype-tissue expression; HDAC6: histone deacetylase 6; I-R: ischemia-reperfusion; LAMP2: lysosomal associated membrane protein 2; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MTOR: mechanistic target of rapamycin kinase; m6A: N6-methyladenosine; MYBL2: MYB proto-oncogene like 2; PIK3C3: phosphatidylinositol 3-kinase catalytic subunit type 3; PSEN1: presenilin 1; PSEN2: presenilin 2; RAB9A, RAB9A: member RAS oncogene family; RAB9B, RAB9B: member RAS oncogene family; RAB40AL: RAB40A like; SF1: splicing factor 1; SOX9: SRY-box transcription factor 9; SRY: sex determining region Y; TFEB: transcription factor EB; ULK1: unc-51 like autophagy activating kinase 1; UVRAG: UV radiation resistance associated; VDAC2: voltage dependent anion channel 2; WDR45: WD repeat domain 45; XPDS: X-linked parkinsonism and spasticity; YTHDF2: YTH N6-methyladenosine RNA binding protein 2.

Development of an autophagy-related gene expression signature for prognosis prediction in prostate cancer patients

Background

Prostate cancer (PCa) is one of the most prevalent cancers that occur in men worldwide. Autophagy-related genes (ARGs) may play an essential role in multiple biological processes of prostate cancer. However, ARGs expression signature has rarely been used to investigate the association between autophagy and prognosis in PCa. This study aimed to identify and assess prognostic ARGs signature to predict overall survival (OS) and disease-free survival (DFS) in PCa patients.

Methods

First, a total of 234 autophagy-related genes were obtained from The Human Autophagy Database. Then, differentially expressed ARGs were identified in prostate cancer patients based on The Cancer Genome Atlas (TCGA) database. The univariate and multivariate Cox regression analysis was performed to screen hub prognostic ARGs for overall survival and disease-free survival, and the prognostic model was constructed. Finally, the correlation between the prognostic model and clinicopathological parameters was further analyzed, including age, T status, N status, and Gleason score.

Results

The OS-related prognostic model was constructed based on the five ARGs (FAM215A, FDD, MYC, RHEB, and ATG16L1) and significantly stratified prostate cancer patients into high- and low-risk groups in terms of OS (HR = 6.391, 95% CI = 1.581– 25.840, P < 0.001). The area under the receiver operating characteristic curve (AUC) of the prediction model was 0.84. The OS-related prediction model values were higher in T3-4 than in T1-2 (P = 0.008), and higher in Gleason score  > 7 than  ≤ 7 (P = 0.015). In addition, the DFS-related prognostic model was constructed based on the 22 ARGs (ULK2, NLRC4, MAPK1, ATG4D, MAPK3, ATG2A, ATG9B, FOXO1, PTEN, HDAC6, PRKN, HSPB8, P4HB, MAP2K7, MTOR, RHEB, TSC1, BIRC5, RGS19, RAB24, PTK6, and NRG2), with AUC of 0.85 (HR = 7.407, 95% CI = 4.850–11.320, P < 0.001), which were firmly related to T status (P < 0.001), N status (P = 0.001), and Gleason score (P < 0.001).

Conclusions

Our ARGs based prediction models are a reliable prognostic and predictive tool for overall survival and disease-free survival in prostate cancer patients.

Tumour metabolism and its unique properties in prostate adenocarcinoma

Anabolic metabolism mediated by aberrant growth factor signalling fuels tumour growth and progression. The first biochemical descriptions of the altered metabolic nature of solid tumours were reported by Otto Warburg almost a century ago. Now, the study of tumour metabolism is being redefined by the development of new molecular tools, tumour modelling systems and precise instrumentation together with important advances in genetics, cell biology and spectroscopy. In contrast to Warburg's original hypothesis, accumulating evidence demonstrates a critical role for mitochondrial metabolism and substantial variation in the way in which different tumours metabolize nutrients to generate biomass. Furthermore, computational and experimental approaches suggest a dominant influence of the tissue-of-origin in shaping the metabolic reprogramming that enables tumour growth. For example, the unique metabolic properties of prostate adenocarcinoma are likely to stem from the distinct metabolism of the prostatic epithelium from which it emerges. Normal prostatic epithelium employs comparatively glycolytic metabolism to sustain physiological citrate secretion, whereas prostate adenocarcinoma consumes citrate to power oxidative phosphorylation and fuel lipogenesis, enabling tumour progression through metabolic reprogramming. Current data suggest that the distinct metabolic aberrations in prostate adenocarcinoma are driven by the androgen receptor, providing opportunities for functional metabolic imaging and novel therapeutic interventions that will be complementary to existing diagnostic and treatment options.

Endocrinotherapy resistance of prostate and breast cancer: Importance of the NF‑κB pathway (Review)

Prostate cancer (PCa) and breast cancer (BCa) are two common sex hormone‑related cancer types with high rates of morbidity, and are leading causes of cancer death globally in men and women, respectively. The biological function of androgen or estrogen is a key factor for PCa or BCa tumorigenesis, respectively. Nevertheless, after hormone deprivation therapy, the majority of patients ultimately develop hormone‑independent malignancies that are resistant to endocrinotherapy. It is widely recognized, therefore, that understanding of the mechanisms underlying the process from hormone dependence towards hormone independence is critical to discover molecular targets for the control of advanced PCa and BCa. This review aimed to dissect the important mechanisms involved in the therapeutic resistance of PCa and BCa. It was concluded that activation of the NF‑κB pathway is an important common mechanism for metastasis and therapeutic resistance of the two types of cancer; in particular, the RelB‑activated noncanonical NF‑κB pathway appears to be able to lengthen and strengthen NF‑κB activity, which has been a focus of recent investigations.

SIRT7 depletion inhibits cell proliferation and androgen-induced autophagy by suppressing the AR signaling in prostate cancer

BACKGROUND

Sirtuin-7 (SIRT7) is associated with the maintenance of tumorigenesis. However, its functional roles and oncogenic mechanisms in prostate cancer (PCa) are poorly understood. Here, we investigated the roles and underlying molecular mechanisms of SIRT7 in PCa cell growth and androgen-induced autophagy.

METHODS

The LNCap and 22Rv1 PCa cell lines were subjected to quantitative reverse transcription (RT)-PCR to characterize their genes encoding SIRT7, AR, and SMAD4. The proteins produced from these genes were quantified by western blotting and immunoprecipitation analysis. SIRT7-depleted cells were produced by transfection with plasmid vectors bearing short hairpin RNAs against SIRT7. The proliferation of each cell line was assessed by CCK8 and EdU assays. Autophagic flux was tracked by mRFP-GFP-LC3 adenovirus under an immunofluorescence microscope. Apoptosis was evaluated by flow cytometry. Tumors were induced in mouse axillae by injection of the cell lines into mice. Tumor morphology was examined by immunohistochemistry and relative tumor growth and metastases were compared by a bioluminescence-based in vivo imaging system.

RESULTS

SIRT7 depletion significantly inhibited cell proliferation, androgen-induced autophagy, and invasion in LNCap and 22Rv1 cells (in vitro) and mouse xenograft tumors induced by injection of these cells (in vivo). SIRT7 knockdown also increased the sensitivity of PCa cells to radiation. Immunohistochemical analysis of 93 specimens and bioinformatic analysis revealed that SIRT7 expression was positively associated with androgen receptor (AR). Moreover, the AR signal pathway participated in SIRT7-mediated regulation of PCa cell proliferation, autophagy, and invasion. SIRT7 depletion downregulated the AR signal pathway by upregulating the level of SMAD4 protein in PCa cells.

CONCLUSION

SIRT7 plays an important role in the development and progression of human PCa and may be a promising prognostic marker for prostate cancer.

DJ-1 inhibits autophagy activity of prostate cancer cells by repressing JNK-Bcl2-Beclin1 signaling

The regulation of DJ-1 on AR signaling plays an important role in the pathogenesis of prostate cancer (PCa). DJ-1 could alter autophagy and regulate Beclin1-involved autophagy response through JNK-dependent pathway. JNK is known to mediate autophagy through Bcl2-Beclin1 complex. Therefore, this study aimed to investigate the significance of autophagy in DJ-1-modulated PCa cells. The current studies showed that DJ-1 overexpression in LNCaP decreased LC3 transformation and autophagosome formation. However, DJ-1 knockdown exerted the opposite effect. Moreover, DJ-1 silencing inhibited survival and promoted death in LNCaP, which was recovered by autophagy inhibition with 3-MA. In addition, DJ-1 overexpression inhibited the phosphorylation of JNK and Bcl2, and the dissociation of Beclin1 and Bcl2; while the effect of silencing DJ-1 was completely opposite. More important, JNK activated by anisimycin inhibited the proliferation and promoted death of DJ-1-overexpressed LNCaP while increasing LC3 transformation and LC3-puncta formation, but these results were reversed by the decrease of Beclin1 (by spautin-1). In contrast, when DJ-1 was silenced, the death of LNCaP, LC3 transformation, and LC3-puncta formation were inhibited by JNK inhibitor SP600125, which promoted cell proliferation. However, Bcl2 inhibition (by ABT737) reversed all the effects of SP600125. Our results suggested that DJ-1 in PCa cells could promote the growth of PCa through autophagy inhibition, and JNK-Bcl2-Beclin1 signaling played an important role in it. The study provided new insights into the role of DJ-1 in the development of PCa.

Divergent Modulation of Proteostasis in Prostate Cancer

Proteostasis regulates key cellular processes such as cell proliferation, differentiation, transcription, and apoptosis. The mechanisms by which proteostasis is regulated are crucial and the deterioration of cellular proteostasis has been significantly associated with tumorigenesis since it specifically targets key oncoproteins and tumor suppressors. Prostate cancer (PCa) is the second most common cause of cancer death in men worldwide. Androgens mediate one of the most central signaling pathways in all stages of PCa via the androgen receptor (AR). In addition to their regulation by hormones, PCa cells are also known to be highly secretory and are particularly prone to ER stress as proper ER function is essential. Alterations in various complex signaling pathways and cellular processes including cell cycle control, transcription, DNA repair, apoptosis, cell adhesion, epithelial-mesenchymal transition (EMT), and angiogenesis are critical factors influencing PCa development through key molecular changes mainly by posttranslational modifications in PCa-related proteins, including AR, NKX3.1, PTEN, p53, cyclin D1, and p27. Several ubiquitin ligases like MDM2, Siah2, RNF6, CHIP, and substrate-binding adaptor SPOP; deubiquitinases such as USP7, USP10, USP26, and USP12 are just some of the modifiers involved in the regulation of these key proteins via ubiquitin-proteasome system (UPS). Some ubiquitin-like modifiers, especially SUMOs, have been also closely associated with PCa. On the other hand, the proteotoxicity resulting from misfolded proteins and failure of ER adaptive capacity induce unfolded protein response (UPR) that is an indispensable signaling mechanism for PCa development. Lastly, ER-associated degradation (ERAD) also plays a crucial role in prostate tumorigenesis. In this section, the relationship between prostate cancer and proteostasis will be discussed in terms of UPS, UPR, SUMOylation, ERAD, and autophagy.

On ATG4B as Drug Target for Treatment of Solid Tumours-The Knowns and the Unknowns

Autophagy is an evolutionary conserved stress survival pathway that has been shown to play an important role in the initiation, progression, and metastasis of multiple cancers; however, little progress has been made to date in translation of basic research to clinical application. This is partially due to an incomplete understanding of the role of autophagy in the different stages of cancer, and also to an incomplete assessment of potential drug targets in the autophagy pathway. While drug discovery efforts are on-going to target enzymes involved in the initiation phase of the autophagosome, e.g., unc51-like autophagy activating kinase (ULK)1/2, vacuolar protein sorting 34 (Vps34), and autophagy-related (ATG)7, we propose that the cysteine protease ATG4B is a bona fide drug target for the development of anti-cancer treatments. In this review, we highlight some of the recent advances in our understanding of the role of ATG4B in autophagy and its relevance to cancer, and perform a critical evaluation of ATG4B as a druggable cancer target.

TRPML1 and RAS-driven cancers - exploring a link with great therapeutic potential

Activating mutations in the RAS family of proto-oncogenes represent some of the leading causes of cancer. Unmitigated proliferation of cells harboring oncogenic RAS mutations is accompanied by a massive increase in cellular bioenergetic demands, which offers unique opportunities for therapeutic intervention. To withstand the steep requirements for metabolic intermediates, RAS-driven cancer cells enhance endolysosome and autophagosome biogenesis. By degrading cellular macromolecules into metabolites that can be used by biosynthetic pathways, endolysosomes permit continued proliferation and survival in otherwise detrimental conditions. We recently showed that human cancers with activating mutations in HRAS elevate the expression of MCOLN1, which encodes an endolysosomal cation channel called TRPML1. Increased TRPML1 activity in HRAS-driven cancer cells is needed for the restoration of plasma membrane cholesterol that gets collaterally internalized during endocytosis. Inhibition of TRPML1 or knockdown of MCOLN1 leads to mislocalization of cholesterol from the plasma membrane to endolysosomes, loss of oncogenic HRAS from the cell surface, and attenuation of downstream signaling. Here, we discuss the implications of our findings and suggest strategies to leverage pathways that impinge upon TRPML1 as novel anti-cancer treatments.

A Novel Salicylanilide Derivative Induces Autophagy Cell Death in Castration-Resistant Prostate Cancer via ER Stress-Activated PERK Signaling Pathway

Metastatic castration-resistant prostate cancer (CRPC) is currently incurable. Cancer growth and progression is intimately affected by its interaction with host microenvironment. Cotargeting of the stroma and prostate cancer is therefore an emerging therapeutic strategy for metastatic CRPC. Cancer-induced osteoclastogenesis is known to contribute to CRPC bone metastasis. This study is to extend pharmacologic value of our synthesized LCC03, a derivative of 5-(2',4'-difluorophenyl)-salicylanilide that has previously testified for its osteoclastogenesis activity, by exploring its additional cytotoxic properties and underlying mechanism in CRPC cells. LCC03 was chemically synthesized and examined for cell growth inhibition in a serial of CRPC cell lines. We demonstrated that LCC03 dose-dependently suppressed proliferation and retarded cell-cycle progression in CRPC cells. The classical autophagy features, including autophagosome formation and LC3-II conversion, were dramatically shown in LCC03-treated CRPC cells, and it was associated with the suppressed AKT/mTOR signaling pathways, a major negative regulator of autophagy. Moreover, an expanded morphology of the endoplasmic reticulum (ER), increased expression of the ER stress markers GRP78 and PERK, and eIF2α phosphorylation were observed. Blockage of autophagy and PERK pathways using small molecule inhibitors or shRNA knockdown reversed LCC03-induced autophagy and cell death, thus indicating that the PERK-eIF2α pathway contributed to the LCC03-induced autophagy. Furthermore, treatment of tumor-bearing mice with intraperitoneal administered LCC03 suppressed the growth of CRPC xenografts in mouse bone without systemic toxicity. The dual action of 5-(2',4'-difluorophenyl)-salicylanilide on targeting both the osteoclasts and the tumor cells strongly indicates that LCC03 is a promising anticancer candidate for preventing and treating metastatic CRPC.

Involvement of Actin in Autophagy and Autophagy-Dependent Multidrug Resistance in Cancer

Currently, autophagy in the context of cancer progression arouses a lot of controversy. It is connected with the possibility of switching the nature of this process from cytotoxic to cytoprotective and vice versa depending on the treatment. At the same time, autophagy of cytoprotective character may be one of the factors determining multidrug resistance, as intensification of the process is observed in patients with poorer prognosis. The exact mechanism of this relationship is not yet fully understood; however, it is suggested that one of the elements of the puzzle may be a cytoskeleton. In the latest literature reports, more and more attention is paid to the involvement of actin in the autophagy. The role of this protein is linked to the formation of autophagosomes, which are necessary element of the process. However, based on the proven effectiveness of manipulation of the actin pool, it seems to be an attractive alternative in breaking autophagy-dependent multidrug resistance in cancer.

The role of androgen in autophagy of granulosa cells from PCOS

Hyperandrogenism is one of the most common causes for anovulation in women and increases the risk for metabolic disorder in PCOS patients. Autophagy plays an important role in dysfunction of endocrine and anovulation. However, the relationship between hyperandrogenism and autophagy in human granulosa cells of PCOS patients remains unclear. By collecting granulosa cells from PCOS patients and non-PCOS patients, we found that the abundance of autophagy-related genes ATG5, ATG7, BECN1 mRNA and the ratio of autophagy marker protein light chain 3B II/I (LC3 II/I) were significantly increased whereas the abundance of the autophagy substrate SQSTM1/p62 was decreased in ovarian granulosa cells from PCOS patients. Furthermore, we demonstrated that BECN1 mRNA abundance in human granulosa cells positively correlated with the basal level of serum total testosterone and androgen up-regulated the abundance of BECN1 mRNA and the ratio of LC3II/LC3I in a dose-dependent manner in cultured granulosa cells. These observations indicated that androgen-induced activation of autophagy may play an important role in the development of PCOS and to explore the autophagy mechanisms involved in PCOS yield new insight into the pathophysiology and therapy of the disorder.

Mitochondrial Uncoupling: A Key Controller of Biological Processes in Physiology and Diseases

Mitochondrial uncoupling can be defined as a dissociation between mitochondrial membrane potential generation and its use for mitochondria-dependent ATP synthesis. Although this process was originally considered a mitochondrial dysfunction, the identification of UCP-1 as an endogenous physiological uncoupling protein suggests that the process could be involved in many other biological processes. In this review, we first compare the mitochondrial uncoupling agents available in term of mechanistic and non-specific effects. Proteins regulating mitochondrial uncoupling, as well as chemical compounds with uncoupling properties are discussed. Second, we summarize the most recent findings linking mitochondrial uncoupling and other cellular or biological processes, such as bulk and specific autophagy, reactive oxygen species production, protein secretion, cell death, physical exercise, metabolic adaptations in adipose tissue, and cell signaling. Finally, we show how mitochondrial uncoupling could be used to treat several human diseases, such as obesity, cardiovascular diseases, or neurological disorders.

Functional genomic studies reveal the androgen receptor as a master regulator of cellular energy metabolism in prostate cancer

Sex-steroid hormones have been investigated for decades for their oncogenic properties in hormone-dependent cancers. The increasing body of knowledge on the biological actions of androgens in prostate cancer has led to the development of several targeted therapies that still represent the standard of care for cancer patients to this day. In the prostate, androgens promote cellular differentiation and proper tissue development. These hormones also promote the aberrant proliferation and survival of prostate cancer cells. Over the past few years, sequencing technologies for functional genomic analyses have rapidly expanded, revealing novel functions of sex-steroid hormone receptors other than their classic roles. In this article, we will focus on transcriptomic- and genomic-based evidence that demonstrates the importance of the androgen receptor signaling in the regulation of prostate cancer cell metabolism. This is significant because the reprogramming of cell metabolism is a hallmark of cancer. In fact, it is clear now that the androgen receptor contributes to the reprogramming of specific cellular metabolic pathways that promote tumor growth and disease progression, including aerobic glycolysis, mitochondrial respiration, fatty acid ß-oxidation, and de novo lipid synthesis. Overall, beyond regulating development, differentiation, and proliferation, the androgen receptor is also a master regulator of cellular energy metabolism.

Autophagy in pulmonary hypertension: Emerging roles and therapeutic implications

Autophagy is an important mechanism for cellular self-digestion and basal homeostasis. This gene- and modulator-regulated pathway is conserved in cells. Recently, several studies have shown that autophagic dysfunction is associated with pulmonary hypertension (PH). However, the relationship between autophagy and PH remains controversial. In this review, we mainly introduce the effects of autophagy-related genes and some regulatory molecules on PH and the relationship between autophagy and PH under the conditions of hypoxia, monocrotaline injection, thromboembolic stress, oxidative stress, and other drugs and toxins. The effects of other autophagy-related drugs, such as chloroquine, 3-methyladenine, rapamycin, and other potential therapeutic drugs and targets, in PH are also described.

NCL1, A Highly Selective Lysine-Specific Demethylase 1 Inhibitor, Suppresses Castration-Resistant Prostate Cancer Growth via Regulation of Apoptosis and Autophagy

Recent studies have shown that epigenetic alterations lead to oncogenic activation, thus indicating that these are therapeutic targets. Herein, we analyzed the efficacy and therapeutic potential of our developed histone lysine demethylase 1 (LSD1) inhibitor, NCL1, in castration-resistant prostate cancer (CRPC). The CRPC cell lines 22Rv1, PC3, and PCai1CS were treated with NCL1, and LSD1 expression and cell viability were assessed. The epigenetic effects and mechanisms of NCL1 were also evaluated. CRPC cells showed strong LSD1 expression, and cell viability was decreased by NCL1 in a dose-dependent manner. Chromatin immunoprecipitation analysis indicated that NCL1 induced histone H3 lysine 9 dimethylation accumulation at promoters of P21. As shown by Western blot and flow cytometry analyses, NCL1 also dose-dependently induced caspase-dependent apoptosis. The stimulation of autophagy was observed in NCL1-treated 22Rv1 cells by transmission electron microscopy and LysoTracker analysis. Furthermore, WST-8 assay revealed that the anti-tumor effect of NCL1 was reinforced when autophagy was inhibited by chloroquine in 22Rv1 cells. Combination index analysis revealed that a concurrent use of these drugs had a synergistic effect. In ex vivo analysis, castrated nude mice were injected subcutaneously with PCai1 cells and intraperitoneally with NCL1. Tumor volume was found to be reduced with no adverse effects in NCL1-treated mice compared with controls. Finally, immunohistochemical analysis using consecutive human specimens in pre- and post-androgen deprivation therapy demonstrated that LSD1 expression levels in CRPC, including neuroendocrine differentiation cases, were very high, and identical to levels observed in previously examined prostate biopsy specimens. NCL1 effectively suppressed prostate cancer growth in vitro and ex vivo without adverse events via the regulation of apoptosis and autophagy, suggesting that NCL1 is a potential therapeutic agent for CRPC.

Recombinant adenoviruses expressing apoptin suppress the growth of MCF‑7 breast cancer cells and affect cell autophagy

Autophagy and apoptosis both promote cell death; however, the relationship between them is subtle, and they mutually promote and antagonize each other. Apoptin can induce apoptosis of various tumor cells; however, tumor cell death is not only caused by apoptosis. Whether apoptin affects tumor cell autophagy is poorly understood. Therefore, the present study aimed to explore the potential mechanisms underlying the effects of apoptin using recombinant adenoviruses expressing apoptin. Reverse transcription-quantitative polymerase chain reaction, immunoblotting, flow cytometry, fluorescence microscopy and proteomics analyses revealed that apoptin could induce autophagy in MCF-7 breast cancer cells. The results also suggested that apoptin affected autophagy in a time- and dose-dependent manner. During the early stage of apoptin stimulation (6 and 12 h), the expression levels of autophagy pathway-associated proteins, including Beclin-1, microtubule-associated protein 1A/1B-light chain 3, autophagy-related 4B cysteine peptidase and autophagy-related 5, were significantly increased, suggesting that apoptin promoted the upregulation of autophagy in MCF-7 cells. Conversely, after 12 h of apoptin stimulation, the expression levels of apoptosis-associated proteins were decreased, thus suggesting that apoptosis may be inhibited. Therefore, it was hypothesized that apoptin may enhance autophagy and inhibit apoptosis in MCF-7 cells at the early stage. In conclusion, apoptin-induced cell death may involve both autophagy and apoptosis. The induction of autophagy may inhibit apoptosis, whereas apoptosis may inhibit autophagy; however, occasionally both pathways operate at the same time and involve apoptin. This apoptin-associated selection between tumor cell survival and death may provide a potential therapeutic strategy for breast cancer.

MIR-1265 regulates cellular proliferation and apoptosis by targeting calcium binding protein 39 in gastric cancer and, thereby, impairing oncogenic autophagy

Increasing evidence indicates that microRNAs (miRNAs) play an important role in various tumors by regulating downstream target genes and diverse signaling pathways. Herein, we confirmed miR-1265 expression in gastric cancer (GC) using the Cancer Genome Atlas (TCGA) database and assessed the level of miR-1265 expression in clinical specimens and cell lines. We found that miR-1265 expression was negatively correlated with tumor size. Further functional analysis revealed that miR-1265 suppresses cellular proliferation and autophagy while inducing apoptosis in GC cells. A luciferase reporter assay was used to identify an miR-1265 targeted gene, calcium binding protein 39 (CAB39), which is an essential upstream regulator in the AMPK-mTOR signaling pathway. Upregulation or downregulation of CAB39 expression reversed the effects of miR-1265 overexpression or inhibition, respectively. Notably, the knockdown of autophagy-related gene 12 (ATG12) impaired the effects of miR-1265 inhibition or CAB39 overexpression in GC. MiR-1265 also suppressed the growth of GC cells in vivo and that of human gastric organoids. Altogether, our results show that miR-1265 suppresses GC progression and oncogenic autophagy by reducing CAB39 expression and regulating the AMPK-mTOR signaling pathway. Therefore, miR-1265 may represent a potential therapeutic target for GC.

Autophagy-Modulating Long Non-coding RNAs (LncRNAs) and Their Molecular Events in Cancer

Cancer is a global threat of health. Cancer incidence and death is also increasing continuously because of poor understanding of diseases. Although, traditional treatments (surgery, radiotherapy, and chemotherapy) are effective against primary tumors, death rate is increasing because of metastasis development where traditional treatments have failed. Autophagy is a conserved regulatory process of eliminating proteins and damaged organelles. Numerous research revealed that autophagy has dual sword mechanisms including cancer progressions and suppressions. In most of the cases, it maintains homeostasis of cancer microenvironment by providing nutritional supplement under starvation and hypoxic conditions. Over the past few decades, stunning research evidence disclosed significant roles of long non-coding RNAs (lncRNAs) in the regulation of autophagy. LncRNAs are RNA containing more than 200 nucleotides, which have no protein-coding ability but they are found to be expressed in most of the cancers. It is also proved that, autophagy-modulating lncRNAs have significant impacts on pro-survival or pro-death roles in cancers. In this review, we highlighted the recently identified autophagy-modulating lncRNAs, their signaling transduction in cancer and mechanism in cancer. This review will explore newly emerging knowledge of cancer genetics and it may provide novel targets for cancer therapy.

NPRL2 enhances autophagy and the resistance to Everolimus in castration-resistant prostate cancer

BACKGROUND

Nitrogen permease regulator-like 2 (NPRL2) is reported to be a tumor suppressor candidate gene and involved in the mTOR signaling and drug resistance in several cancers. However, the role of NPRL2 in regulating the resistance to Everolimus (EVS), an inhibitor of the mTOR, in castration-resistant prostate cancer (CRPC) is still unclear. Therefore, in present study, we evaluated the role of NPRL2 and its potential resistance to EVS in CRPC.

METHODS

NPRL2 expression levels in prostate tissues, including benign prostate hyperplasia (BPH) tissues, primary prostate cancer (PCa) tissues, CRPC tissues, and several PCa cell lines (LNCaP, PC3, and enzalutamide-resistant LNCaP, named LNPER) were be evaluated by immunohistochemistry, RT-PCR, and Western blot. Furthermore, we employed the loss or gain function of NPRL2 to determine the role of NPRL2 in regulating the proliferation, sensitivity to EVS, the mTOR signaling, autophagy in CRPC. Lastly, relationship between NPRL2 expression level and the efficacy of EVS were evaluated in mice tumor xenograft models.

RESULTS

NPRL2 expression level is upregulated in PCa, particularly in the CRPC. NPRL2 over-expression promoted the proliferation, resistance to EVS, and NPRL2 silencing inhibited proliferation, enhanced sensitivity to EVS in PC3 and LNPER cells. Moreover, NPRL2-silencing increased the activity of mTOR signaling, and the autophagy attenuation induced by NPRL2-silencing in EVS-treated CRPC cells was associated with the increase of apoptosis. In addition, the growth prevention of NPRL2-silencing LNPER tumors in mice induced by EVS-treatment was associated with the autophagy attenuation and apoptosis increase.

CONCLUSIONS

NPRL2 may act as a pro-growth factor in PCa. The high levels of NPRL2 expression in CRPC promote resistance to EVS by enhancing autophagy. NPRL2 may be a new therapeutic target for intervention of CRPC and a biomarker for predicting resistance to EVS in CRPC.

TFEB controls vascular development by regulating the proliferation of endothelial cells

Transcription factor TFEB is thought to control cellular functions—including in the vascular bed—primarily via regulation of lysosomal biogenesis and autophagic flux. Here, we report that TFEB also orchestrates a non‐canonical program that controls the cell cycle/VEGFR2 pathway in the developing vasculature. In endothelial cells, TFEB depletion halts proliferation at the G1‐S transition by inhibiting the CDK4/Rb pathway. TFEB‐deficient cells attempt to compensate for this limitation by increasing VEGFR2 levels at the plasma membrane via microRNA‐mediated mechanisms and controlled membrane trafficking. TFEB stimulates expression of the miR‐15a/16‐1 cluster, which limits VEGFR2 transcript stability and negatively modulates expression of MYO1C, a regulator of VEGFR2 trafficking to the cell surface. Altered levels of miR‐15a/16‐1 and MYO1C in TFEB‐depleted cells cause increased expression of plasma membrane VEGFR2, but in a manner associated with low signaling strength. An endothelium‐specific Tfeb‐knockout mouse model displays defects in fetal and newborn mouse vasculature caused by reduced endothelial proliferation and by anomalous function of the VEGFR2 pathway. These previously unrecognized functions of TFEB expand its role beyond regulation of the autophagic pathway in the vascular system.

The transcription factors TFE3 and TFEB amplify p53 dependent transcriptional programs in response to DNA damage

The transcription factors TFE3 and TFEB cooperate to regulate autophagy induction and lysosome biogenesis in response to starvation. Here we demonstrate that DNA damage activates TFE3 and TFEB in a p53 and mTORC1 dependent manner. RNA-Seq analysis of TFEB/TFE3 double-knockout cells exposed to etoposide reveals a profound dysregulation of the DNA damage response, including upstream regulators and downstream p53 targets. TFE3 and TFEB contribute to sustain p53-dependent response by stabilizing p53 protein levels. In TFEB/TFE3 DKOs, p53 half-life is significantly decreased due to elevated Mdm2 levels. Transcriptional profiles of genes involved in lysosome membrane permeabilization and cell death pathways are dysregulated in TFEB/TFE3-depleted cells. Consequently, prolonged DNA damage results in impaired LMP and apoptosis induction. Finally, expression of multiple genes implicated in cell cycle control is altered in TFEB/TFE3 DKOs, revealing a previously unrecognized role of TFEB and TFE3 in the regulation of cell cycle checkpoints in response to stress.

Overexpression of Ulk2 inhibits proliferation and enhances chemosensitivity to cisplatin in non-small cell lung cancer

The aim of the present study was to examine the function of unc-51 like autophagy activating kinase 2 (Ulk2) in non-small cell lung cancer (NSCLC). Western blotting was used to analyze the protein expression of Ulk2 in seven pairs of cancerous and adjacent non-cancerous NSCLC specimens. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis was used to determine the mRNA expression of Ulk2 in 20 pairs of tumor and adjacent normal tissues. Two NSCLC cell lines, A549 and H460, were transfected with an Ulk2 overexpression plasmid or empty vector; cell proliferation and chemosensitivity were measured using an MTT assay, and flow cytometry and western blotting were used to evaluate apoptosis. A nude mouse tumorigenesis experiment was used to assess tumor volume in vivo, using A549 cells stably overexpressing Ulk2 and control cells. The protein expression levels of Ulk2 were significantly lower in 6/7 (85.7%) cases of NSCLC compared with in non-cancerous tissues, as determined by western blotting (P<0.05). The mRNA expression levels of Ulk2 were significantly lower in 16/20 (70.0%) NSCLC specimens compared with in non-cancerous tissues, as revealed by RT-qPCR (P<0.05). Overexpression of Ulk2 significantly inhibited the proliferation of A549 and H460 cells (P<0.05) and sensitized the NSCLC cell lines to cisplatin- and etoposide-induced inhibition of proliferation, and to cisplatin-induced apoptosis, with a significant difference identified compared with the control group (P<0.05). Overexpression of Ulk2 significantly increased basal autophagy levels in A549 and H460 cells (P<0.05). Thus, Ulk2-induced enhanced chemosensitivity was suggested to be partly mediated through increased autophagy. The overexpression of Ulk2 significantly suppressed tumor volume in vivo (P<0.05). Overexpression of Ulk2 inhibits cancer cell proliferation and enhances chemosensitivity to cisplatin in NSCLC.

How does estrogen work on autophagy?

Macroautophagy/autophagy is vital for intracellular quality control and homeostasis. Therefore, careful regulation of autophagy is very important. In the past 10 years, a number of studies have reported that estrogenic effectors affect autophagy. However, some results, especially those regarding the modulatory effect of 17β-estradiol (E2) on autophagy seem inconsistent. Moreover, several clinical trials are already in place combining both autophagy inducers and autophagy inhibitors with endocrine therapies for breast cancer. Not all patients experience benefit, which further confuses and complicates our understanding of the main effects of autophagy in estrogen-related cancer. In view of the importance of the crosstalk between estrogen signaling and autophagy, this review summarizes the estrogenic effectors reported to affect autophagy, subcellular distribution and translocation of estrogen receptors, autophagy-targeted transcription factors (TFs), miRNAs, and histone modifications regulated by E2. Upon stimulation with estrogen, there will always be opposing functional actions, which might occur between different receptors, receptors on TFs, TFs on autophagy genes, or even histone modifications on transcription. The huge signaling network downstream of estrogen can promote autophagy and reduce overstimulated autophagy at the same time, which allows autophagy to be regulated by estrogen in a restricted range. To help understand how the estrogenic regulation of autophagy affects cell fate, a hypothetical model is presented here. Finally, we discuss some exciting new directions in the field. We hope this might help to better understand the multiple associations between estrogen and autophagy, the pathogenic mechanisms of many estrogen-related diseases, and to design novel and efficacious therapeutics. Abbreviations: AP-1, activator protein-1; HATs, histone acetyltransferases; HDAC, histone deacetylases; HOTAIR, HOX transcript antisense RNA.

Lysosomes contribute to radioresistance in cancer

Radiotherapy is one of the most widely used methods to treat human tumors. Efficacy is due mainly to the DNA damage it induces. However, tumor cells often develop responsive adaptiveness to radiation treatment to survive, which leads to radioresistance. Many cellular processes, such as DNA damage repair, cell cycle arrest and autophagy, are involved in the development of radioresistance. Few interventions to combat radioresistance exist to date. In recent years, the lysosome has been reported to contribute to chemo- and radioresistance. Although for many years, the lysosome was known as an organelle that degrades waste materials, we now know it is also involved in important signaling pathways regulating cellular homeostasis. Although an increasing number of preclinical studies show that lysosome-related factors promote radioresistance, the role of the lysosome in radioresistance has not been systematically demonstrated. Here, we combine an updated understanding of lysosomes with a review of current studies regarding the role of lysosomes in mediating radioresistance.

Endothelial cells promote metastasis of prostate cancer by enhancing autophagy

BACKGROUND

Prostate cancer is one of the most common malignancies. Increasing evidence suggested that endothelial cells may contribute to prostate cancer progression and metastasis. Most recently, autophagy has been proposed to plays a significant role in tumorigenesis and metastasis. Also, it is reported that downregulation of androgen receptor (AR) induces autophagy in prostate cancer cells. However, the underlying mechanisms remain unclear. Here, we aim to explore the role and mechanisms of endothelial cell in prostate cancer progression.

METHODS

The coculture system was established to test the effect of endothelial cells on prostate cancer cells. We performed antibody array and ELISA were used to profile the cytokine expression pattern of endothelial cells in supernatant. Western blot and RT-PCR were used to determine the mechanism by endothelial cells to promote invasion ability of prostate cancer cells. Maraviroc and chloroquine were used to block the CCL5/CCR5 and autophagy pathway respectively. Orthotopic xenograft mouse models and drug treatment study were conducted to determine the role of endothelial cells in promoting metastatic potential in vivo.

RESULTS

We use CPRC prostate cancer model and demonstrate that endothelial cells secrete large amount of CCL5 and induces autophagy by suppressing AR expression in prostate cancer cell lines. Consequently, elevated autophagy accelerates focal adhesions proteins disassembly and promoted prostate cancer invasion. Inhibition of both CCL5/CCR5 signaling and autophagy significantly reduces metastasis in vivo.

CONCLUSIONS

Together, our data establish the function for endothelial cells in tumor metastasis and propose new drug target for mCRPC.

TFEB dysregulation as a driver of autophagy dysfunction in neurodegenerative disease: Molecular mechanisms, cellular processes, and emerging therapeutic opportunities

Two decades ago, the recognition of protein misfolding and aggregate accumulation as defining features of neurodegenerative disease set the stage for a thorough examination of how protein quality control is maintained in neurons and in other non-neuronal cells in the central nervous system (CNS). Autophagy, a pathway of cellular self-digestion, has emerged as especially important for CNS proteostasis, and autophagy dysregulation has been documented as a defining feature of neurodegeneration in Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD). Transcription factor EB (TFEB) is one of the main transcriptional regulators of autophagy, as it promotes the expression of genes required for autophagosome formation, lysosome biogenesis, and lysosome function, and it is highly expressed in CNS. Over the last 7 years, TFEB has received considerable attention and TFEB dysfunction has been implicated in the pathogenesis of numerous neurodegenerative disorders. In this review, we delineate the current understanding of how TFEB dysregulation is involved in neurodegeneration, highlighting work done on AD, PD, HD, X-linked spinal & bulbar muscular atrophy, and amyotrophic lateral sclerosis. Because TFEB is a central node in defining autophagy activation status, efforts at understanding the basis for TFEB dysfunction are yielding insights into how TFEB might be targeted for therapeutic application, which may represent an exciting opportunity for the development of a treatment modality with broad application to neurodegeneration.

GLUT12 promotes prostate cancer cell growth and is regulated by androgens and CaMKK2 signaling

Despite altered metabolism being an accepted hallmark of cancer, it is still not completely understood which signaling pathways regulate these processes. Given the central role of androgen receptor (AR) signaling in prostate cancer, we hypothesized that AR could promote prostate cancer cell growth in part through increasing glucose uptake via the expression of distinct glucose transporters. Here, we determined that AR directly increased the expression of SLC2A12, the gene that encodes the glucose transporter GLUT12. In support of these findings, gene signatures of AR activity correlated with SLC2A12 expression in multiple clinical cohorts. Functionally, GLUT12 was required for maximal androgen-mediated glucose uptake and cell growth in LNCaP and VCaP cells. Knockdown of GLUT12 also decreased the growth of C4-2, 22Rv1 and AR-negative PC-3 cells. This latter observation corresponded with a significant reduction in glucose uptake, indicating that additional signaling mechanisms could augment GLUT12 function in an AR-independent manner. Interestingly, GLUT12 trafficking to the plasma membrane was modulated by calcium/calmodulin-dependent protein kinase kinase 2 (CaMKK2)-5'-AMP-activated protein kinase (AMPK) signaling, a pathway we previously demonstrated to be a downstream effector of AR. Inhibition of CaMKK2-AMPK signaling decreased GLUT12 translocation to the plasma membrane by inhibiting the phosphorylation of TBC1D4, a known regulator of glucose transport. Further, AR increased TBC1D4 expression. Correspondingly, expression of TBC1D4 correlated with AR activity in prostate cancer patient samples. Taken together, these data demonstrate that prostate cancer cells can increase the functional levels of GLUT12 through multiple mechanisms to promote glucose uptake and subsequent cell growth.

Delineation of the androgen-regulated signaling pathways in prostate cancer facilitates the development of novel therapeutic approaches

Although androgen deprivation therapy (ADT) is initially effective for the treatment of progressive prostate cancer, it inevitably fails due to the onset of diverse resistance mechanisms that restore androgen receptor (AR) signaling. Thus, AR remains a desired therapeutic target even in the relapsed stages of the disease. Given the difficulties in stopping all AR reactivation mechanisms, we propose that the identification of the driver signaling events downstream of the receptor offer viable, alternative therapeutic targets. Here, we summarize recently described, AR-regulated processes that have been demonstrated to promote prostate cancer. By highlighting these signaling events and describing some of the ongoing efforts to pharmacologically modulate these pathways, our goal is to advocate potential new therapeutic targets that would represent an alternative approach for blocking AR actions.

Androgen Receptor-CaMKK2 Axis in Prostate Cancer and Bone Microenvironment

The skeletal system is of paramount importance in advanced stage prostate cancer (PCa) as it is the preferred site of metastasis. Complex mechanisms are employed sequentially by PCa cells to home to and colonize the bone. Bone-resident PCa cells then recruit osteoblasts (OBs), osteoclasts (OCs), and macrophages within the niche into entities that promote cancer cell growth and survival. Since PCa is heavily reliant on androgens for growth and survival, androgen-deprivation therapy (ADT) is the standard of care for advanced disease. Although it significantly improves survival rates, ADT detrimentally affects bone health and significantly increases the risk of fractures. Moreover, whereas the majority patients with advanced PCa respond favorably to androgen deprivation, most experience a relapse of the disease to a hormone-refractory form within 1-2 years of ADT. The tumor adapts to surviving under low testosterone conditions by selecting for mutations in the androgen receptor (AR) that constitutively activate it. Thus, AR signaling remains active in PCa cells and aids in its survival under low levels of circulating androgens and additionally allows the cancer cells to manipulate the bone microenvironment to fuel its growth. Hence, AR and its downstream effectors are attractive targets for therapeutic interventions against PCa. Ca²⁺/calmodulin-dependent protein kinase kinase 2 (CaMKK2), was recently identified as a key downstream target of AR in coordinating PCa cell growth, survival, and migration. Additionally, this multifunctional serine/threonine protein kinase is a critical mediator of bone remodeling and macrophage function, thus emerging as an attractive therapeutic target downstream of AR in controlling metastatic PCa and preventing ADT-induced bone loss. Here, we discuss the role played by AR-CaMKK2 signaling axis in PCa survival, metabolism, cell growth, and migration as well as the cell-intrinsic roles of CaMKK2 in OBs, OCs, and macrophages within the bone microenvironment.

Cigarette Smoke Exposure Inhibits Bacterial Killing via TFEB-Mediated Autophagy Impairment and Resulting Phagocytosis Defect

INTRODUCTION

Cigarette smoke (CS) exposure is the leading risk factor for COPD-emphysema pathogenesis. A common characteristic of COPD is impaired phagocytosis that causes frequent exacerbations in patients leading to increased morbidity. However, the underlying mechanism is unclear. Hence, we investigated if CS exposure causes autophagy impairment as a mechanism for diminished bacterial clearance via phagocytosis by utilizing murine macrophages (RAW264.7 cells) and Pseudomonas aeruginosa (PA01-GFP) as an experimental model.

METHODS

Briefly, RAW cells were treated with cigarette smoke extract (CSE), chloroquine (autophagy inhibitor), TFEB-shRNA, CFTR(inh)-172, and/or fisetin prior to bacterial infection for functional analysis.

RESULTS

Bacterial clearance of PA01-GFP was significantly impaired while its survival was promoted by CSE (p < 0.01), autophagy inhibition (p < 0.05; p < 0.01), TFEB knockdown (p < 0.01; p < 0.001), and inhibition of CFTR function (p < 0.001; p < 0.01) in comparison to the control group(s) that was significantly recovered by autophagy-inducing antioxidant drug, fisetin, treatment (p < 0.05; p < 0.01; and p < 0.001). Moreover, investigations into other pharmacological properties of fisetin show that it has significant mucolytic and bactericidal activities (p < 0.01; p < 0.001), which warrants further investigation.

CONCLUSIONS

Our data suggests that CS-mediated autophagy impairment as a critical mechanism involved in the resulting phagocytic defect, as well as the therapeutic potential of autophagy-inducing drugs in restoring is CS-impaired phagocytosis.

NOX2-Mediated TFEB Activation and Vacuolization Regulate Lysosome-Associated Cell Death Induced by Gypenoside L, a Saponin Isolated from Gynostemma pentaphyllum

Downregulation of apoptotic signal pathway and activation of protective autophagy mainly contribute to the chemoresistance of tumor cells. Therefore, exploring efficient chemotherapeutic agents or isolating novel natural products that can trigger nonapoptotic and nonautophagic cell death such as lysosome-associated death is emergently required. We have recently extracted a saponin, gypenoside L (Gyp-L), from Gynostemma pentaphyllum and showed that Gyp-L was able to induce nonapoptotic cell death of esophageal cancer cells associated with lysosome swelling. However, contributions of vacuolization and lysosome to cell death remain unclear. Herein, we reveal a critical role for NADPH oxidase NOX2-mediated vacuolization and transcription factor EB (TFEB) activation in lysosome-associated cell death. We found that Gyp-L initially induced the abnormal enlarged and alkalized vacuoles, which were derived from lipid rafts dependent endocytosis. Besides, NOX2 was activated to promote vacuolization and mTORC1-independent TFEB-mediated lysosome biogenesis. Finally, raising lysosome pH could enhance Gyp-L induced cell death. These findings suggest a protective role of NOX2-TFEB-mediated lysosome biogenesis in cancer drug resistance and the tight interaction between lipid rafts and vacuolization. In addition, Gyp-L can be utilized as an alternative option to overcome drug-resistance though inducing lysosome associated cell death.