Epidermal growth factor receptor expression escapes androgen regulation in prostate cancer: a potential molecular switch for tumour growth

Lapatinib antitumor effect is associated with PI3K and MAPK pathway: An analysis in human and canine prostate cancer cells

The aberrant activation of HER2 has a pivotal role in bone metastasis implantation and progression in several tumor types, including prostate cancer (PC). Trastuzumab and other anti-HER2 therapies, such as lapatinib, have been used in human breast cancer HER2 positive. Although HER2 overexpression has been reported in PC, anti-HER2 therapy response has revealed conflicting results. We investigated the potential of lapatinib in inhibiting cell migration and inducing apoptosis in two human (LNCaP and PC3) and two canine PC cell lines (PC1 and PC2). Cell migration and apoptosis were evaluated by Annexin V/PI analysis after lapatinib treatment. The transcriptome analysis of all cell lines before and after treatment with lapatinib was also performed. We found increased apoptosis and migration inhibition in LNCaP cells (androgen-sensitive cell line), while PC1, PC2, and PC3 cells showed no alterations after the treatment. The transcriptome analysis of LNCaP and PC3 cell lines showed 158 dysregulated transcripts in common, while PC1 and PC2 cell lines presented 82. At the doses of lapatinib used, we observed transcriptional modifications in all cell lines. PI3K/AKT/mTOR pathway were enriched in human PC cells, while canine PC cells showed enrichment of tyrosine kinase antitumor response and HER2-related pathways. In canine PC cells, the apoptosis failed after lapatinib treatment, possibly due to the downregulation of MAPK genes. Prostate cancer cells insensitive to androgens may be resistant to lapatinib through PI3K gene dysregulation. The association of lapatinib with PI3K inhibitors may provide a more effective antitumor response and clinical benefits to PC patients.

TNIK drives castration-resistant prostate cancer via phosphorylating EGFR

The development of castration-resistant prostate cancer (CRPC) is driven by intricate genetic and epigenetic mechanisms. Traf2- and Nck-interacting kinase (TNIK) has been reported as a serine/threonine kinase associated with tumor cell proliferation or unfavorable cancer behavior. The microarray approach revealed a substantial upregulation of TNIK expression levels, enabling us to investigate the functional behaviors of the TNIK gene in CRPC. Specifically, we discovered that AR suppresses TNIK gene transcription in LNCaP and C4-2 cells by forming a complex with H3K27me3. Following the reduction of AR levels induced by androgen deprivation therapy (ADT), TNIK is recruited to activate EGFR signaling through phosphorylation in C4-2 cells, thereby promoting CRPC progression. Our findings unveil a regulatory role of AR as a repressor for TNIK while also highlighting how TNIK activates the EGFR pathway via phosphorylation to drive CRPC progression. Consequently, targeting TNIK may represent an appealing therapeutic strategy for CRPC.

The effect of heat stress on the epidermal growth factor (EGF)-mediated intracellular signaling, and changes cell behavior on swine testicular cell

At present, high environmental temperature is the main factor endangering animal production, growth and development. Therefore, the harmful effects of heat stress led by hot environment on livestock have attracted much attention. In this work, the cellar property and signaling property of epidermal growth factor (EGF) below heat stress remains unclear in swine testicular cells. Here, the effect of heat stress on EGF-induced intracellular signaling and cell behavior was explored in the ST (a porcine testis cell line). A series of experiments were done to study the cellular behavior and signaling properties of EGF under heat stress. It can be discovered which high ambient temperature changed the cellular characteristics of EGF/EGFR. The eventuates displayed when cells were exposed to thermal environment, EGF/EGFR basically did not internalize, mainly gathered on the cell membrane. Our group also researched the effect of EGF's signaling properties, and the results showed that the ability of EGF to activate EGFR-mediated intracellular signaling decreased significantly under heat stress. Finally, this study illustrated that EGF's cell behavior and signaling profile are obviously altered, indicating that heat stress seriously affected the biological activity of EGF/EGFR, which establish a solid foundation for studying the effect of the EGF on testicular tissue under heat environment.

H19 in Serum Extracellular Vesicles Reflects Resistance to AR Axis-targeted Therapy Among CRPC Patients

BACKGROUND/AIM

We aimed to evaluate the changes of androgen receptor (AR) signaling-related long non-coding RNAs (lncRNAs) in serum extracellular vesicles (EVs) from prostate cancer (PC) patients, in order to identify novel biomarkers for AR axis-targeted therapy (ARAT)-resistance among castration-resistant PC (CRPC) patients.

PATIENTS AND METHODS

EVs were isolated from 2 patients before and after acquiring ARAT-resistance. RNA profiling of EVs was performed by RNA-sequencing. The expression levels of selected lncRNAs in EVs were analyzed by digital droplet PCR (ddPCR) in 58 localized and 14 metastatic PC patients at diagnosis, 7 ARAT-naïve and 6 ARAT-resistant CRPC patients. LncRNA H19 expression in PC tissue was examined using published data. In order to analyze the role of H19, the prognosis was analyzed in PC patients and proteomic analysis was performed in 22Rv1 PC cells.

RESULTS

RNA-sequencing revealed that AR-regulated RNAs were most enriched in EVs after acquiring ARAT-resistance. Among them, up-regulation of AR signaling-related lncRNAs (PCAT1, H19, HOXA-11AS, ZEB1-AS1, ARLNC1, PART1, CTBP1-AS and PCA3) was confirmed by ddPCR. H19 contained in EVs (EV-H19) was significantly increased among ARAT-resistant patients compared to ARAT-naïve CRPC or metastatic PC patients. In PC tissue, H19 was negatively correlated with AR protein and AR-activity score and up-regulated in neuroendocrine CRPC tissue with low AR expression. Furthermore, EV-H19 expression was significantly associated with worse outcome to androgen-deprivation therapy. Proteomic analysis demonstrated that H19 knockdown enhanced PC-related protein expression.

CONCLUSION

EV-H19 may negatively correlate with AR-signaling activity and could be a marker to diagnose ARAT-resistance among CRPC patients.

The Bone Microenvironment Soil in Prostate Cancer Metastasis: An miRNA Approach

Bone metastatic prostate cancer (PCa) is associated with a high risk of mortality. Changes in the expression pattern of miRNAs seem to be related to early aspects of prostate cancer, as well as its establishment and proliferation, including the necessary steps for metastasis. Here we compiled, for the first time, the important roles of miRNAs in the development, diagnosis, and treatment of bone metastasis, focusing on recent in vivo and in vitro studies. PCa exosomes are proven to promote metastasis-related events, such as osteoblast and osteoclast differentiation and proliferation. Aberrant miRNA expression in PCa may induce abnormal bone remodeling and support tumor development. Furthermore, miRNAs are capable of binding to multiple mRNA targets, a dynamic property that can be harnessed for the development of treatment tools, such as antagomiRs and miRNA mimics, which have emerged as promising candidates in PCa treatment. Finally, miRNAs may serve as noninvasive biomarkers, as they can be detected in tissue and bodily fluids, are highly stable, and show differential expression between nonmetastatic PCa and bone metastatic samples. Taken together, the findings underscore the importance of miRNA expression profiles and miRNA-based tools as rational technologies to increase the quality of life and longevity of patients.

Decursin inhibits EGFR-ERK1/2 signaling axis in advanced human prostate carcinoma cells

We have shown that decursin, a coumarin compound, induces cell cycle arrest and apoptosis in human prostate cancer cells (PCa); however, its molecular mechanisms are largely unexplored. We studied the mechanisms associated with its anticancer activity in advanced human prostate carcinoma cells. We found that decursin inhibited epidermal growth factor receptor (EGFR) signaling by inhibiting its activating phosphorylation at tyrosine 1068 residue in DU145 and 22Rv1 cells. This inhibition of EGFR was associated with the downregulation of ERK1/2 phosphorylation. Both EGFR and ERK1/2 are known to be deregulated/activated in many human malignancies. Consistent with our earlier study, decursin (25-100 µM) treatment for 24-72 h inhibited DU145 cell proliferation by 49%-87% (p < 0.001) which was associated with strong G1 phase arrest and cell death. It also decreased (p < 0.001) the number of surviving colonies. Decursin moderately increased the expression of Rb-related proteins p107 and p130 but decreased the levels of E2F family transcription factors including E2F-3, E2F-4 and E2F-5. Further, decursin strongly inhibited the growth of androgen-dependent prostate carcinoma 22Rv1 cells from 61% to 79% (p < 0.001) and arrested these cells at G1 phase via induction of cyclin-dependent kinase inhibitor p27/Kip1 and downregulation of CDK2 and CDK4 protein expression. Additionally, EGFR inhibitor erlotinib- and EGF ligand-modulated EGFR activation validated EGFR signaling as a target of decursin-mediated cell growth inhibition and cytotoxicity. Decursin decreased EGF ligand-induced phosphorylation of EGFR (Y-1068) as well as activation of its downstream mediator, ERK1/2. Furthermore, inhibitory targeting of EGFR-ERK1/2 axis by combinatorial treatment of decursin and erlotinib further sensitized DU145 cells for the decursin-induced growth inhibition and cell death. Overall, these findings strongly suggest that anticancer efficacy of decursin against human PCa involves inhibitory targeting of EGFR-ERK1/2 signaling axis, a pathway constitutively active in advanced PCa.

Modulating the Activity of Androgen Receptor for Treating Breast Cancer

The androgen receptor (AR) is a steroid hormone receptor widely detected in breast cancer. Evidence suggests that the AR might be a tumor suppressor in estrogen receptor alpha-positive (ERα+ve) breast cancer but a tumor promoter in estrogen receptor alpha-negative (ERα-ve) breast cancer. Modulating AR activity could be a potential strategy for treating breast cancer. For ERα+ve breast cancer, activation of the AR had been demonstrated to suppress the disease. In contrast, for ERα-ve breast cancer, blocking the AR could confer better prognosis to patients. These studies support the feasibility of utilizing AR modulators as anti-cancer drugs for different subtypes of breast cancer patients. Nevertheless, several issues still need to be addressed, such as the lack of standardization in the determination of AR positivity and the presence of AR splice variants. In future, the inclusion of the AR status in the breast cancer report at the time of diagnosis might help improve disease classification and treatment decision, thereby providing additional treatment strategies for breast cancer.

Knockdown of USP8 inhibits prostate cancer cell growth, proliferation, and metastasis and promotes docetaxel's activity by suppressing the NF-kB signaling pathway

Ubiquitin-specific protease 8 (USP8) has been recently reported to be involved in tumorigenesis. Prostate cancer (PCa) is the most diagnosed malignancy among men, but USP8's role in PCa is not yet investigated comprehensively. Therefore, the PCa cell lines DU145 and PC3 were transfected with USP8 siRNA or overexpressing vector together with or without docetaxel. The silencing USP8 and docetaxel treatment reduced cell viability and migration and promoted apoptosis. In contrast, USP8 knockdown was found to enhance docetaxel antitumor activity. In contrast, increased cell viability and migration were noticed upon USP8 overexpression, thereby decreasing apoptosis and suppressing docetaxel antitumor activity. Notably, although EGFR, PI3K, and NF-kB were found to be increased in both USP8 overexpression and docetaxel treatment, it significantly attenuated the effects in USP8 silencing followed by with or without docetaxel. Although EGFR silencing decreased PI3K and NF-kB activation, overexpression of USP8 was shown to counteract SiEGFR's effects on NF-kB signaling by increasing PI3K expression. Our findings revealed that USP8 plays an oncogenic role in PCa and can suppress docetaxel activity. Additionally, as EGFR/PI3K/NF-kB was previously reported to develop docetaxel resistance, the combination treatment of USP8 knockdown with docetaxel might be a potential PCa therapeutic.

Resistance to prostate cancer treatments

A review of the current treatment options for prostate cancer and the formation of resistance to these regimens has been compiled including primary, acquired, and cross-resistance. The diversification of the pathways involved and the escape routes the tumor is utilizing have been addressed. Whereas early stages of tumor can be cured, there is no treatment available after a point of no return has been reached, leaving palliative treatment as the only option. The major reasons for this outcome are the heterogeneity of tumors, both inter- and intra-individually and the nearly endless number of escape routes, which the tumor can select to overcome the effects of treatment. This means that more focus should be applied to the individualization of both diagnosis and therapy of prostate cancer. In addition to current treatment options, novel drugs and ongoing clinical trials have been addressed in this review.

N-glycosylation of GDF15 abolishes its inhibitory effect on EGFR in AR inhibitor-resistant prostate cancer cells

Castration-resistance of prostate cancer is one of the most challenging clinical problems. In the present study, we have performed proteomics and glycomics using LNCaP model. Growth differentiation factor-15 (GDF15) level is increased in androgen receptor (AR) inhibitor-resistant cells and the inhibitory effect of GDF15 on epithelial growth factor receptor (EGFR) pathway is relieved by GDF15 N70 glycosylation. Interference of GDF15 (siRNA or N70Q dominant negative) or EGFR pathway (inhibitor or siRNA for EGFR, SRC or ERK) decreases the resistant-cell survival in culture and tumor growth in mice. Our study reveals a novel regulatory mechanism of prostate cancer AR inhibitor resistance, raises the possibility of AR/SRC dual-targeting of castration-resistance of prostate cancer, and lays foundation for the future development of selective inhibitors of GDF15 glycosylation.

FBXW2 inhibits prostate cancer proliferation and metastasis via promoting EGFR ubiquitylation and degradation

FBXW2 is a poorly characterized F-box protein, as a tumor suppressor that inhibits growth and metastasis of lung cancer by promoting ubiquitylation and degradation of oncogenic proteins, including SKP2 and β-catenin. However, what the biological functions of FBXW2 in prostate cancer cells and whether FBXW2 targets other substrates to involve in progression of prostate cancer is still unclear. Here, we reported that overexpression of FBXW2 attenuated proliferation and metastasis of PCa models both in vitro and in vivo, while FBXW2 depletion exhibited the opposite effects. Intriguingly, FBXW2 was an E3 ligase for EGFR in prostate cancer. EGFR protein level and its half-life were extended by FBXW2 depletion, while EGFR protein level was decreased, and its half-life was shortened upon overexpression of FBXW2, but not its dominant-negative mutant. Importantly, FBXW2 bond to EGFR via its consensus degron motif (TSNNST), and ubiquitylated and degraded EGFR, resulting in repression of EGF function. Thus, our data uncover a novel that FBXW2 as a tumor suppressor of prostate cancer, inhibits EGFR downstream by promoting EGFR ubiquitination and degradation, resulting in repression of cell proliferation and metastasis.

Unravelling the Role of Kinases That Underpin Androgen Signalling in Prostate Cancer

The androgen receptor (AR) signalling pathway is the key driver in most prostate cancers (PCa), and is underpinned by several kinases both upstream and downstream of the AR. Many popular therapies for PCa that target the AR directly, however, have been circumvented by AR mutation, such as androgen receptor variants. Some upstream kinases promote AR signalling, including those which phosphorylate the AR and others that are AR-regulated, and androgen regulated kinase that can also form feed-forward activation circuits to promotes AR function. All of these kinases represent potentially druggable targets for PCa. There has generally been a divide in reviews reporting on pathways upstream of the AR and those reporting on AR-regulated genes despite the overlap that constitutes the promotion of AR signalling and PCa progression. In this review, we aim to elucidate which kinases—both upstream and AR-regulated—may be therapeutic targets and require future investigation and ongoing trials in developing kinase inhibitors for PCa.

Circulating tumor cell gene expression and plasma AR gene copy number as biomarkers for castration-resistant prostate cancer patients treated with cabazitaxel

BACKGROUND

Cabazitaxel improves overall survival (OS) in metastatic castration-resistant prostate cancer (mCRPC) patients progressing after docetaxel. In this prospective study, we evaluated the prognostic role of CTC gene expression on cabazitaxel-treated patients and its association with plasma androgen receptor (AR) copy number (CN).

METHODS

Patients receiving cabazitaxel 20 or 25 mg/sqm for mCRPC were enrolled. Digital PCR was performed to assess plasma AR CN status. CTC enrichment was assessed using the AdnaTest EMT-2/StemCell kit. CTC expression analyses were performed for 17 genes. Data are expressed as hazard ratio (HR) or odds ratio (OR) and 95% CI.

RESULTS

Seventy-four patients were fully evaluable. CTC expression of AR-V7 (HR=2.52, 1.24-5.12, p=0.011), AKR1C3 (HR=2.01, 1.06-3.81, p=0.031), AR (HR=2.70, 1.46-5.01, p=0.002), EPCAM (HR=3.75, 2.10-6.71, p< 0.0001), PSMA (HR=2.09, 1.19-3.66, p=0.01), MDK (HR=3.35, 1.83-6.13, p< 0.0001), and HPRT1 (HR=2.46, 1.44-4.18, p=0.0009) was significantly associated with OS. ALDH1 (OR=5.50, 0.97-31.22, p=0.05), AR (OR=8.71, 2.32-32.25, p=0.001), EPCAM (OR=7.26, 1.47-35.73, p=0.015), PSMA (OR=3.86, 1.10-13.50, p=0.035), MDK (OR=6.84, 1.87-24.98, p=0.004), and HPRT1 (OR=7.41, 1.82-30.19, p=0.005) expression was associated with early PD. AR CN status was significantly correlated with AR-V7 (p=0.05), EPCAM (p=0.02), and MDK (p=0.002) expression. In multivariable model, EPCAM and HPRT1 CTC expression, plasma AR CN gain, ECOG PS=2, and liver metastases and PSA were independently associated with poorer OS. In patients treated with cabazitaxel 20 mg/sqm, median OS was shorter in AR-V7 positive than negative patients (6.6 versus 14 months, HR=3.46, 1.47-8.17], p=0.004).

CONCLUSIONS

Baseline CTC biomarkers may be prognosticators for cabazitaxel-treated mCRPC patients. Cabazitaxel at lower (20 mg/sqm) dose was associated with poorer outcomes in AR-V7 positive patients compared to AR-V7 negative patients in a post hoc subgroup analysis.

TRIAL REGISTRATION

Clinicaltrials.gov NCT03381326 . Retrospectively registered on 18 December 2017.

KIF15 Promotes Progression of Castration Resistant Prostate Cancer by Activating EGFR Signaling Pathway

Castration-resistant prostate cancer (CRPC) continues to be a major clinical problem and its underlying mechanisms are still not fully understood. The epidermal growth factor receptor (EGFR) activation is an important event that regulates mitogenic signaling. EGFR signaling plays an important role in the transition from androgen dependence to castration-resistant state in prostate cancer (PCa). Kinesin family member 15 (KIF15) has been suggested to be overexpressed in multiple malignancies. Here, we demonstrate that KIF15 expression is elevated in CRPC. We show that KIF15 contributes to CRPC progression by enhancing the EGFR signaling pathway, which includes complex network intermediates such as mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K)/AKT pathways. In CRPC tumors, increased expression of KIF15 is positively correlated with EGFR protein level. KIF15 binds to EGFR, and prevents EGFR proteins from degradation in a Cdc42-dependent manner. These findings highlight the key role of KIF15 in the development of CRPC and rationalize KIF15 as a potential therapeutic target.

Role of PI3K-AKT-mTOR Pathway as a Pro-Survival Signaling and Resistance-Mediating Mechanism to Therapy of Prostate Cancer

Androgen deprivation therapy (ADT) and androgen receptor (AR)-targeted therapy are the gold standard options for treating prostate cancer (PCa). These are initially effective, as localized and the early stage of metastatic disease are androgen- and castration-sensitive. The tumor strongly relies on systemic/circulating androgens for activating AR signaling to stimulate growth and progression. However, after a certain point, the tumor will eventually develop a resistant stage, where ADT and AR antagonists are no longer effective. Mechanistically, it seems that the tumor becomes more aggressive through adaptive responses, relies more on alternative activated pathways, and is less dependent on AR signaling. This includes hyperactivation of PI3K-AKT-mTOR pathway, which is a central signal that regulates cell pro-survival/anti-apoptotic pathways, thus, compensating the blockade of AR signaling. The PI3K-AKT-mTOR pathway is well-documented for its crosstalk between genomic and non-genomic AR signaling, as well as other signaling cascades. Such a reciprocal feedback loop makes it more complicated to target individual factor/signaling for treating PCa. Here, we highlight the role of PI3K-AKT-mTOR signaling as a resistance mechanism for PCa therapy and illustrate the transition of prostate tumor from AR signaling-dependent to PI3K-AKT-mTOR pathway-dependent. Moreover, therapeutic strategies with inhibitors targeting the PI3K-AKT-mTOR signal used in clinic and ongoing clinical trials are discussed.

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

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

Cell Plasticity and Prostate Cancer: The Role of Epithelial-Mesenchymal Transition in Tumor Progression, Invasion, Metastasis and Cancer Therapy Resistance

Simple Summary

Although epithelial-to-mesenchymal transition (EMT) is a well-known cellular process involved during normal embryogenesis and wound healing, it also has a dark side; it is a complex process that provides tumor cells with a more aggressive phenotype, facilitating tumor metastasis and even resistance to therapy. This review focuses on the key pathways of EMT in the pathogenesis of prostate cancer and the development of metastases and evasion of currently available treatments.

Abstract

Prostate cancer, the second most common malignancy in men, is characterized by high heterogeneity that poses several therapeutic challenges. Epithelial–mesenchymal transition (EMT) is a dynamic, reversible cellular process which is essential in normal embryonic morphogenesis and wound healing. However, the cellular changes that are induced by EMT suggest that it may also play a central role in tumor progression, invasion, metastasis, and resistance to current therapeutic options. These changes include enhanced motility and loss of cell–cell adhesion that form a more aggressive cellular phenotype. Moreover, the reverse process (MET) is a necessary element of the metastatic tumor process. It is highly probable that this cell plasticity reflects a hybrid state between epithelial and mesenchymal status. In this review, we describe the underlying key mechanisms of the EMT-induced phenotype modulation that contribute to prostate tumor aggressiveness and cancer therapy resistance, in an effort to provide a framework of this complex cellular process.

Androgen Receptor-Dependent Mechanisms Mediating Drug Resistance in Prostate Cancer

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

LRIG1, a regulator of stem cell quiescence and a pleiotropic feedback tumor suppressor

LRIG1, leucine-rich repeats and immunoglobulin-like domains protein 1, was discovered more than 20 years ago and has been shown to be downregulated or lost, and to function as a tumor suppressor in several cancers. Another well-reported biological function of LRIG1 is to regulate and help enforce the quiescence of adult stem cells (SCs). In both contexts, LRIG1 regulates SC quiescence and represses tumor growth via, primarily, antagonizing the expression and activities of ERBB and other receptor tyrosine kinases (RTKs). We have recently reported that in treatment-naïve human prostate cancer (PCa), LRIG1 is primarily regulated by androgen receptor (AR) and is prominently overexpressed. In castration-resistant PCa (CRPC), both LRIG1 and AR expression becomes heterogeneous and, frequently, discordant. Importantly, in both androgen-dependent PCa and CRPC models, LRIG1 exhibits tumor-suppressive functions. Moreover, LRIG1 induction inhibits the growth of pre-established AR⁺ and AR⁻ PCa. Here, upon a brief introduction of the LRIG1 and the LRIG family, we provide an updated overview on LRIG1 functions in regulating SC quiescence and repressing tumor development. We further highlight the expression, regulation and functions of LRIG1 in treatment-naïve PCa and CRPC. We conclude by offering the perspectives of identifying novel cancer-specific LRIG1-interacting signaling partners and developing LRIG1-based anti-cancer therapeutics and diagnostic/prognostic biomarkers.

KRAS, BRAF, PIK3CA mutation frequency of radical prostatectomy samples and review of the literature

OBJECTIVE

The molecular basis of prostate cancer is highly heterogeneous. Our study aimed to perform the mutation analysis of KRAS, BRAF, PIK3CA, and immunohistochemical (IHC) evaluation of EGFR, HER2, p16, and PTEN to demonstrate new areas for targeted therapies.

METHODS

A total of 24 prostatectomy samples diagnosed with adenocarcinoma were analyzed by microarray hybridization. Also, these samples were IHC stained for EGFR, HER2, P16, and PTEN. The cases were divided into two groups based on low and high Gleason scores. All findings were compared with the clinicopathological parameters of the patients.

RESULTS

While KRAS mutation was in 3/24 (12.5%) of our cases, BRAF and PIK3CA mutations were not detected. There was no significant difference between the groups in terms of KRAS mutation frequency. HER2 was immunohistochemically negative in all samples. There was no correlation between EGFR, P16 immunopositivity, and clinicopathological features.

CONCLUSION

KRAS mutation frequency is similar to those in Asian populations. BRAF and PIK3CA mutation frequencies have been reported in the literature in the range of 0-15% and 0-10.4%, respectively, consistent with our study findings. HER2 immunoexpression is a controversial issue in the literature. EGFR and p16 expressions may not correlate with the stage.

EGFR as a stable marker of prostate cancer dissemination to bones

BACKGROUND

Prostate cancer (PCa) is among the most commonly diagnosed malignancies in men. Although 5-year survival in patients with localised disease reaches nearly 100%, metastatic disease still remains incurable. Therefore, there is a need for markers indicating metastatic dissemination.

METHODS

EGFR overexpression (EGFRover) was tracked in 1039 primary tumours, circulating tumour cells from 39 d'Amico high-risk patients and metastatic samples from 21 castration-resistant PCa cases. EGFR status was compared to clinical parameters and multiple molecular factors were assessed using immunohistochemistry and gene ontology analysis. The functional aspect of EGFR was evaluated by plating PC-3 cells on soft and rigid matrices.

RESULTS

EGFRover was found in 14% of primary tumours, where it was associated with shorter metastasis-free survival and was an independent indicator of worse overall survival. EGFRover correlated with a pro-migratory and pro-metastatic phenotype of tumour cells as well as rich collagen fibre content. All circulating tumour cells (detected in 13% of cases) were positive for EGFR, independent of their EMT-related phenotype. EGFRover was more prevalent in castration-resistant bone metastases (29% of patients) and supported growth of human PCa cells on rigid matrices mimicking bone stiffness.

CONCLUSIONS

EGFRover is a stable, EMT-independent marker of PCa disseminating to rigid organs, preferentially bones.

EGFR/FOXO3A/LXR-α Axis Promotes Prostate Cancer Proliferation and Metastasis and Dual-Targeting LXR-α/EGFR Shows Synthetic Lethality

Prostate cancer is the second leading cause of cancer-related death in men. Early prostate cancer has a high 5-year survival rate. However, the five-year survival rate is low in progressive prostate cancer, which manifests as bone metastasis. The EGF receptor overexpression increases during disease progression and in the development of castration-resistant disease, and may be a potential therapeutic target. Liver X receptors (LXRs) are ligand-dependent nuclear receptor transcription factors and consist of two subtypes, LXR-α and LXR-β, which can inhibit tumor growth in various cancer cells. We revealed that LXR-α, but not LXR-β, was reduced in prostate cancer tissues compared with adjacent normal tissues. LXRs' agonist GW3965 enhanced the inhibitory action of LXR-α on the proliferation and metastasis of prostate cancer cells. Furthermore, our results support the notion that LXR-α is regulated by the EGFR/AKT/FOXO3A pathway. As an EGFR inhibitor, Afatinib could weaken AKT activation and increase the expression level of FOXO3A in prostate cancer. In addition, we indicated that the combination of Afatinib and GW3965 simultaneously increased and activated LXR-α, which led to an increase of tumor suppressors, and eventually inhibited tumor progression. Therefore, the combination of EGFR inhibitor and LXRs agonist may become a potential treatment strategy for prostate cancer, especially metastatic prostate cancer.

EGFR-upregulated LIFR promotes SUCLG2-dependent castration resistance and neuroendocrine differentiation of prostate cancer

Neuroendocrine (NE) differentiation is a well-recognized phenotypic change of prostate cancer after androgen deprivation therapy (ADT), and it ultimately develops into an aggressive subset of this disease. However, the contribution of signaling pathways that lead to metabolic disorders and NE differentiation of prostate cancer remains unclear. In this study, we identified that ADT induced upregulation of the succinate-CoA ligase GDP-forming beta subunit (SUCLG2), which regulates succinate metabolism and NE differentiation of prostate cancer. We demonstrated a connection that upregulation of epidermal growth factor receptor (EGFR)-leukemia inhibitory factor receptor (LIFR) signaling induced SUCLG2 expression in prostate cancer cells. The LIFR is upregulated by nuclear EGFR, which acts as a transcriptional regulator, directly binds to the LIFR promoter, and drives NE differentiation and glycolysis of prostate cancer. LIFR upregulation is associated with SUCLG2, which increased succinate synthesis and enzymatic activities of mitochondrial nucleoside diphosphate kinase (NDPK) in prostate cancer cells. Knockdown of SUCLG2 suppressed NE differentiation in cultured cells and reduced prostate tumor growth in a xenograft model. Analysis of prostate tissue samples showed increased intensity of nuclear EGFR associated with the LIFR and SUCLG2 in castration-resistant prostate cancer tumors. Our study provides a mechanism whereby ADT upregulates EGFR-LIFR signaling that activates SUCLG2, which subsequently stimulates the metabolic changes associated with NE differentiation and aggressive prostate cancer phenotype.

Digging Deeper into Breast Cancer Epigenetics: Insights from Chemical Inhibition of Histone Acetyltransferase TIP60 In Vitro

Breast cancer is often sporadic due to several factors. Among them, the deregulation of epigenetic proteins may be involved. TIP60 or KAT5 is an acetyltransferase that regulates gene transcription through the chromatin structure. This pleiotropic protein acts in several cellular pathways by acetylating proteins. RNA and protein expressions of TIP60 were shown to decrease in some breast cancer subtypes, particularly in triple-negative breast cancer (TNBC), where a low expression of TIP60 was exhibited compared with luminal subtypes. In this study, the inhibition of the residual activity of TIP60 in breast cancer cell lines was investigated by using two chemical inhibitors, TH1834 and NU9056, first on the acetylation of the specific target, lysine 4 of histone 3 (H3K4) by immunoblotting, and second, by chromatin immunoprecipitation (ChIP)-qPCR (-quantitative Polymerase Chain Reaction). Subsequently, significant decreases or a trend toward decrease of H3K4ac in the different chromatin compartments were observed. In addition, the expression of 48 human nuclear receptors was studied with TaqMan Low-Density Array in these breast cancer cell lines treated with TIP60 inhibitors. The statistical analysis allowed us to comprehensively characterize the androgen receptor and NR3C2 receptors in TNBC cell lines after TH1834 or NU9056 treatment. The understanding of the residual activity of TIP60 in the evolution of breast cancer might be a major asset in the fight against this disease, and could allow TIP60 to be used as a biomarker or therapeutic target for breast cancer progression in the future.

Morphological Changes of Meibomian Glands in Men With Benign Prostate Hyperplasia

PURPOSE

Meibomian glands are subject to regulation by sex hormones. We have now investigated the possible relation between benign prostate hyperplasia (BPH) and meibomian gland dysfunction (MGD).

METHODS

Men diagnosed with BPH and receiving treatment with tamsulosin and age-matched male control subjects who attended Itoh Clinic, Saitama, Japan, were enrolled. An ocular symptom score, lid margin abnormality score, and superficial punctate keratopathy score as well as the meiboscore (0-6), meibum grade, breakup time of the tear film, and Schirmer test values were evaluated. Male pattern baldness was also graded according to the Hamilton-Norwood scale.

RESULTS

Forty-four eyes of 44 men with BPH (mean age ± SD, 76.1 ± 2.2 years) and 46 eyes of 46 control subjects (mean age ± SD, 75.3 ± 6.2 years) were enrolled. The meiboscore in the BPH group (4.5 ± 1.4) was significantly higher than that in the control group (1.8 ± 1.5, P < 0.0001). Breakup time of the tear film was significantly shorter (3.6 ± 1.7 vs. 5.6 ± 2.5 seconds, P < 0.0001), and Schirmer test value was significantly smaller (9.8 ± 4.8 vs. 13.3 ± 8.0 mm, P = 0.048) in the BPH group than that in the control group. Other ocular parameters did not differ significantly between the 2 groups. The proportion of men with androgenic alopecia was also higher in the BPH group than that in the control group.

CONCLUSIONS

BPH was associated with meibomian gland loss and instability of the tear film as well as with the presence of androgenic alopecia.

Cellular growth factors as prospective therapeutic targets for combination therapy in androgen independent prostate cancer (AIPC)

Cancer is the second leading cause of death worldwide, with prostate cancer, the second most commonly diagnosed cancer among men. Prostate cancer develops in the peripheral zone of the prostate gland, and the initial progression largely depends on androgens, the male reproductive hormone that regulates the growth and development of the prostate gland and testis. The currently available treatments for androgen dependent prostate cancer are, however, effective for a limited period, where the patients show disease relapse, and develop androgen-independent prostate cancer (AIPC). Studies have shown various intricate cellular processes such as, deregulation in multiple biochemical and signaling pathways, intra-tumoral androgen synthesis; AR over-expression and mutations and AR activation via alternative growth pathways are involved in progression of AIPC. The currently approved treatment strategies target a single cellular protein or pathway, where the cells slowly develop resistance and adapt to proliferate via other cellular pathways over a period of time. Therefore, an increased research aims to understand the efficacy of combination therapy, which targets multiple interlinked pathways responsible for acquisition of resistance and survival. The combination therapy is also shown to enhance efficacy as well as reduce toxicity of the drugs. Thus, the present review focuses on the signaling pathways involved in the progression of AIPC, comprising a heterogeneous population of cells and the advantages of combination therapy. Several clinical and pre-clinical studies on a variety of combination treatments have shown beneficial outcomes, yet further research is needed to understand the potential of combination therapy and its diverse strategies.

In silico docking of phytocompounds to identify potent inhibitors of signaling pathways involved in prostate cancer

Androgens and androgen receptors (AR) are the master regulators in the development of prostate cancer. Majority of the patients show positive response to surgical or medical castration, while many patients show disease relapse after the treatment. Genomic profiling has proven that the deregulated PI3K, Ras/Raf, MAPK and EGFR signaling pathways confer survival and invasion advantage to the cancer cells. Thus, modulation of these interlinked growth pathways along with androgen ablation may provide attractive therapeutic benefits. The current research is focused to identify the inhibitors of these pathways with bacosides and Piperine. The quantitative estimation of bacosides enriched standard extract of Bacopa monnieri by HPTLC showed 59.38% of Bacoside A and various active compounds with anti-oxidant, anti-cancer, anti-microbial, anti-inflammatory properties were also analyzed by GC-MS analysis. The in-vitro cytotoxic study against PC3 cell lines showed dose-dependent effect of Piperine and the extract. Further, in silico docking has shown bacosides with significant molecular interactions and binding score with growth factor receptors such as EGFR, PI3K, Akt and ERK, whereas Piperine exhibited interactions with AR. Hence, a simultaneous downregulation of interlinked signaling pathways of growth factors and AR with bacosides and Piperine may produce effective cytotoxic potential against the androgen-independent prostate cancer. Further in-vitro and in-vivo experimental investigations are necessary to determine the ultimate therapeutic utility. Communicated by Ramaswamy H. Sarma.

Validation of the four-miRNA biomarker panel MiCaP for prediction of long-term prostate cancer outcome

Improved prostate cancer prognostic biomarkers are urgently needed. We previously identified the four-miRNA prognostic biomarker panel MiCaP ((miR-23a-3p × miR-10b-5p)/(miR-133a-3p × miR-374b-5p)) for prediction of biochemical recurrence (BCR) after radical prostatectomy (RP). Here, we identified an optimal numerical cut-off for MiCaP dichotomisation using a training cohort of 475 RP patients and tested this in an independent cohort of 281 RP patients (PCA281). Kaplan–Meier, uni- and multivariate Cox regression analyses were conducted for multiple endpoints: BCR, metastatic-(mPC) and castration-resistant prostate cancer (CRPC), prostate cancer-specific (PCSS) and overall survival (OS). Functional effects of the four MiCaP miRNAs were assessed by overexpression and inhibition experiments in prostate cancer cell lines. We found the numerical value 5.709 optimal for MiCaP dichotomisation. This was independently validated in PCA281, where a high MiCaP score significantly [and independent of the Cancer of the Prostate Risk Assessment Postsurgical (CAPRA-S) score] predicted BCR, progression to mPC and CRPC, and PCSS, but not OS. Harrell’s C-index increased upon addition of MiCaP to CAPRA-S for all endpoints. Inhibition of miR-23a-3p and miR-10b-5p, and overexpression of miR-133a-3p and miR-374b-5p significantly reduced cell survival. Our results may promote future implementation of a MiCaP-based test for improved prostate cancer risk stratification.

Androgen receptor phosphorylation at serine 81 and serine 213 in castrate-resistant prostate cancer

BACKGROUND

Despite increases in diagnostics and effective treatments, over 300,000 men die from prostate cancer highlighting the need for specific and differentiating biomarkers. AR phosphorylation associates with castrate-resistance, with pAR^ser213 promoting transcriptional activity. We hypothesise that combined pAR^ser81 and pAR^ser213 reduces survival and would benefit from dual-targeting androgen-dependent and Akt-driven disease.

METHODS

Immunohistochemistry and immunofluorescence were performed on matched hormone-naive and castrate-resistant prostate cancer samples. TempO-Seq gene profiling was analysed using DESeq2 package. LNCaP-AI cells were stimulated with DHT or EGF. WST-1 assays were performed to determine effects of Enzalutamide and BKM120 on cell viability.

RESULTS

Following the development of castrate-resistance, pAR^ser81 expression reduced and pAR^ser213 expression increased. Castrate-resistance pAR^ser81 expression was not associated with survival but high pAR^ser213 expression was associated with reduced survival from relapse. Combined high pAR^ser81 and pAR^ser213 was associated with reduced survival from relapse. pAR^ser81 expression was induced by 10 nM DHT or 10 nM EGF and pAR^ser213 expression was induced by treatment with 10 nM EGF in LNCaP-AI cells. Cell viability was reduced following treatment with 10 nM Enzalutamide and 10 nM BKM120. Eight genes were differentially expressed between hormone-naive and castrate-resistant tumours and twenty-five genes were differentially expressed between castrate-resistant tumours with high and low pAR^ser213 expression.

CONCLUSION

Combined pAR^ser81 and pAR^ser213 provides a novel prognostic biomarker for castrate-resistant disease and a potential predictive and therapeutic target for prostate cancer. Further studies will be required to investigate the combined effects of targeting AR and PI3K/AKT signalling.

CMTM5-v1 inhibits cell proliferation and migration by downregulating oncogenic EGFR signaling in prostate cancer cells

Anomalous epidermal growth factor receptor (EGFR) signaling plays an important role in the progression of prostate cancer (PCa) and the transformation to castration-resistant PCa (CRPC). A novel tumor suppressor CKLF-like MARVEL transmembrane domain-containing member 5(CMTM5) has a MARVEL domain and may regulate transmembrane signaling. Thus, we postulated that CMTM5 could regulate EGFR and its downstream molecules to affect the biological behaviors of PCa cells. In this study, we found that CMTM5 was expressed in benign prostatic hyperplasia (BPH) tissues but was undetectable in PCa cells. However, the EGFR was upregulated in PCa cells, especially in two metastatic CRPC cell lines, PC3 and DU145. Furthermore, ectopic expression of CMTM5-v1 suppressed cell proliferation and migration and p-EGFR levels. Further investigation revealed that restoration of CMTM5-v1 inhibited not only EGF-mediated proliferation but also chemotactic migration by EGF in PC3 and DU145 cells. Moreover, mechanistic studies showed that CMTM5-v1 attenuated EGF-induced receptor signaling by repressing EGFR and Akt phosphorylation in PCa cells, which were essential for malignant features. Finally, CMTM5-v1can promote the sensitivity of PC3 cells to Gefetinib, a tyrosine kinase inhibitor (TKI) targeting the EGFR. These observations indicate that CMTM5-v1 suppressed PCa cells through EGFR signaling. The loss of CMTM5 may participate in the progression of PCa resulting from deregulated EGFR, and CMTM5 might be associated with the efficacy of TKIs in terms of their potent inhibition of EGFR and human epidermal growth factor-2 (HER2) activation.

Combined targeting of EGFR and HER2 against prostate cancer stem cells

Progression of prostate cancer has been associated with EGFR and HER2 activation and to tumor-initiating cells contribution toward chemotherapy resistance. We investigated the efficacy of a dual intervention against EGFR and HER2 to deplete the tumor-initiating cells, optimize the chemotherapy management and prevent the progression of castration-resistant prostate cancer (CRPC) cells. Using DU145, PC3, and 22Rv1 CRPC cell lines, biochemical analysis revealed activation of EGFR, HER2, MAPK, and STAT3 in DU145 and 22Rv1, and AKT and SRC in DU145 and PC-3. pSTAT3 nuclear staining was observed in DU145 xenografts and in 12 out of 14 CRPC specimens. The in vivo dual targeting of ErbB receptors with Cetuximab and Trastuzumab combined with chemotherapy caused an effective antitumor response in DU145 xenografted mice displaying STAT3 activation; conversely PC-3 bearing mice experienced tumor relapse. The potentiating of in vivo cytotoxic effect in DU145 model was accompanied by a significant decrease of prostatosphere-forming capacity assessed in vitro on residual tumor cells. Additionally, combined treatment in vitro with Cetuximab, Trastuzumab and chemotherapy negatively affected DU145 and 22Rv1 sphere formation, suggesting the critical function of ErbB receptors for tumor-initiating cells proliferation; no effect on PC-3 clonogenic potential was observed, indicating that other receptors than EGFR and HER2 may sustain PC3 tumor-initiating cells. These findings provided the preclinical evidence that the dual inhibition of EGFR and HER2 by targeting tumor-initiating cells may improve the efficacy of the current chemotherapy regimen, bringing benefits especially to castration-resistant patients with activated STAT3, and preventing disease progression.

miR-1272 Exerts Tumor-Suppressive Functions in Prostate Cancer via HIP1 Suppression

The development of novel therapies or the improvement of currently used approaches to treat prostate cancer (PCa), the most frequently diagnosed male tumor in developed countries, is an urgent need. In this regard, the functional characterization of microRNAs, molecules shown to regulate a number of cancer-related pathways, is instrumental to their possible clinical exploitation. Here, we demonstrate the tumor-suppressive role of the so far uncharacterized miR-1272, which we found to be significantly down-modulated in PCa clinical specimens compared to normal tissues. Through a gain-of-function approach using miRNA mimics, we showed that miR-1272 supplementation in two PCa cell models (DU145 and 22Rv1) reverted the mesenchymal phenotype by affecting migratory and invasive properties, and reduced cell growth in vitro and in vivo in SCID mice. Additionally, by targeting HIP1 encoding the endocytic protein HIP1, miR-1272 balanced EGFR membrane turnover, thus affecting the downstream AKT/ERK pathways, and, ultimately, increasing PCa cell response to ionizing radiation. Overall, our results show that miR-1272 reconstitution can affect several tumor traits, thus suggesting this approach as a potential novel therapeutic strategy to be pursued for PCa, with the multiple aim of reducing tumor growth, enhancing response to radiotherapy and limiting metastatic dissemination.

Therapies Targeted to Androgen Receptor Signaling Axis in Prostate Cancer: Progress, Challenges, and Hope

Prostate cancer is the mostly commonly diagnosed non-cutaneous malignancy and the second leading cause of cancer-related death affecting men in the United States. Moreover, it disproportionately affects the men of African origin, who exhibit significantly greater incidence and mortality as compared to the men of European origin. Since androgens play an important role in the growth of normal prostate and prostate tumors, targeting of androgen signaling has remained a mainstay for the treatment of aggressive prostate cancer. Over the years, multiple approaches have been evaluated to effectively target the androgen signaling pathway that include direct targeting of the androgens, androgen receptor (AR), AR co-regulators or other alternate mechanisms that impact the outcome of androgen signaling. Several of these approaches are currently in clinical practice, while some are still pending further development and clinical evaluation. This remarkable progress has resulted from extensive laboratory, pre-clinical and clinical efforts, and mechanistic learnings from the therapeutic success and failures. In this review, we describe the importance of androgen signaling in prostate cancer biology and advances made over the years to effectively target this signaling pathway. We also discuss emerging data on the resistance pathways associated with the failure of various androgen signaling- targeted therapies and potential of this knowledge for translation into future therapies for prostate cancer.

Integrated analysis of miRNA landscape and cellular networking pathways in stage-specific prostate cancer

Dysregulation of miRNAs has been demonstrated in several human malignancies including prostate cancer. Due to tissue limitation and variable disease progression, stage-specific miRNAs changes in prostate cancer is unknown. Using chip-based microarray, we investigated global miRNA expression in human prostate cancer LNCaP, PC3, DU145 and 22Rv1 cells representing early-stage, advanced-stage and castration resistant prostate cancer in comparison with normal prostate epithelial cells. A total of 292 miRNAs were differentially expressed with 125 upregulated and 167 downregulated. These miRNAs were involved in pathways including drug resistance drug-efflux, adipogenesis, epithelial-to-mesenchymal transition, bone metamorphosis, and Th1/Th2 signaling. Regulation of miRNAs were interlinked with upstream regulators such as Argonaut 2 (AGO2), Double-Stranded RNA-Specific Endoribonuclease (DICER1), Sjogren syndrome antigen B (SSB), neurofibromatosis 2 (NF2), and peroxisome proliferator activated receptor alpha (PPARA), activated during stage-specific disease progression. Candidate target genes and pathways dysregulated in stage-specific prostate cancer were identified using CS-miRTar database and confirmed in clinical specimens. Integrative network analysis suggested some genes targeted by miRNAs include miR-17, let7g, miR-146, miR-204, miR-205, miR-221, miR-301 and miR-520 having a major effect on their dysregulation in prostate cancer. MiRNA-microarray analysis further identified miR-130a, miR-181, miR-328, miR146 and miR-200 as a panel of novel miRNAs associated with drug resistance drug-efflux and epithelial-to-mesenchymal transition in prostate cancer. Our findings provide evidence on miRNA dysregulation and its association with key functional components in stage-specific prostate cancer.

DUSP22 suppresses prostate cancer proliferation by targeting the EGFR-AR axis

Dual-specificity phosphatases (DUSPs) regulate the activity of various downstream kinases through serine or threonine or tyrosine dephosphorylation. Loss of function and aberrant expression of DUSPs has been implicated in cancer progression and poor survival, yet the function of DUSP22 in prostate cancer (PCa) cells is not clear. Gene Expression Omnibus and cBioPortal microarray database analyses showed that DUSP22 expression was lower in PCa tissues than normal prostate tissues, and altered DUSP22 expression was associated with shorter progression-free and disease-free survival of patients with PCa. Exogenous DUSP22 expression in LNCaP, PC3, and C4-2B PCa cells inhibited cellular proliferation and colony formation, supporting a growth inhibitory role for DUSP22 in PCa cells. DUSP22 expression significantly attenuated epidermal growth factor (EGF) receptor (EGFR) and its downstream ERK1/2 signaling by dephosphorylation. However, DUSP22 failed to suppress the growth of CWR22Rv1 and DU145 cells with elevated phosphorylated (p-)ERK1/2 levels. A serine-to-alanine mutation at position 58, a potential ERK1/2-targeted phosphorylation site in DUSP22, was sufficient to suppress growth of CWR22Rv1 cells with elevated p-ERK1/2 levels, suggesting a mutually antagonistic relationship between DUSP22 and ERK1/2 dependent on phosphorylation status. We showed that DUSP22 can suppress prostate-specific antigen gene expression through phosphatase-dependent pathways, suggesting that DUSP22 is an important regulator of the androgen receptor (AR) in PCa cells. Mechanistically, DUSP22 can interact with AR as a regulatory partner and interfere with EGF-induced AR phosphorylation at Tyr534, suggesting that DUSP22 serves as a crucial suppressor of both EGFR and AR-dependent signaling in PCa cells via dephosphorylation. Our findings indicate that loss of function of DUSP22 in PCa cells leads to aberrant activation of both EGFR-ERKs and AR signaling and ultimately progression of PCa, supporting the potential for novel therapeutic design of harnessing DUSP22 in the treatment of PCa.-Lin, H.-P., Ho, H.-M., Chang, C.-W., Yeh, S.-D., Su, Y.-W., Tan, T.-H., Lin, W.-J. DUSP22 suppresses prostate cancer proliferation by targeting the EGFR-AR axis.

Trichostatin A inhibits proliferation of PC3 prostate cancer cells by disrupting the EGFR pathway

Prostate cancer (PC) is the most common type of malignancy to exist in men within developed countries. Androgen deprivation therapy is performed for metastatic and advanced PC. However, the majority of cases of prostate cancer become refractory during therapy, leading to castration-resistant PC (CRPC). Histone deacetylases (HDACs) are key factors in regulating gene transcription and have been associated with cancer development. In the present study the small molecule inhibitor trichostatin A (TSA), which targets HDACs, was demonstrated to inhibit the proliferation of CRPC PC3 cells by disrupting the epidermal growth factor receptor (EGFR)-STAT3 pathway. The expression of EGFR and STAT3 was downregulated following TSA treatment, and cell cycle arrest was induced by downregulating the expression of cyclin D1 and CDK6, and via retinoblastoma protein phosphorylation. Furthermore, the transcription of cyclin D1 and CDK6 was suppressed by TSA. Apoptosis of PC3 cells treated with TSA was also investigated, and it was revealed that TSA induced apoptosis by upregulating BAX and downregulating BCL-2. The combination of TSA with doxorubicin exerted a synergistic inhibitory effect on PC3 cell proliferation through the induction of apoptosis. The results of the present study revealed a promising epigenetic-based therapeutic strategy that could be implemented in cases of CRPC.

Limited short-term effects on human prostate cancer xenograft growth and epidermal growth factor receptor gene expression by the ghrelin receptor antagonist [D-Lys3]-GHRP-6

PURPOSE

The ghrelin axis regulates many physiological functions (including appetite, metabolism, and energy balance) and plays a role in disease processes. As ghrelin stimulates prostate cancer proliferation, the ghrelin receptor antagonist [D-Lys³]-GHRP-6 is a potential treatment for castrate-resistant prostate cancer and for preventing the metabolic consequences of androgen-targeted therapies. We therefore explored the effect of [D-Lys³]-GHRP-6 on PC3 prostate cancer xenograft growth.

METHODS

NOD/SCID mice with PC3 prostate cancer xenografts were administered 20 nmoles/mouse [D-Lys³]-GHRP-6 daily by intraperitoneal injection for 14 days and tumour volume and weight were measured. RNA sequencing of tumours was conducted to investigate expression changes following [D-Lys³]-GHRP-6 treatment. A second experiment, extending treatment time to 18 days and including a higher dose of [D-Lys³]-GHRP-6 (200 nmoles/mouse/day), was undertaken to ensure repeatability.

RESULTS

We demonstrate here that daily intraperitoneal injection of 20 nmoles/mouse [D-Lys³]-GHRP-6 reduces PC3 prostate cancer xenograft tumour volume and weight in NOD/SCID mice at two weeks post treatment initiation. RNA-sequencing revealed reduced expression of epidermal growth factor receptor (EGFR) in these tumours. Further experiments demonstrated that the effects of [D-Lys³]-GHRP-6 are transitory and lost after 18 days of treatment.

CONCLUSIONS

We show that [D-Lys³]-GHRP-6 has transitory effects on prostate xenograft tumours in mice, which rapidly develop an apparent resistance to the antagonist. Although further studies on [D-Lys³]-GHRP-6 are warranted, we suggest that daily treatment with the antagonist is not a suitable treatment for advanced prostate cancer.

Inhibition of EGFR signaling with Spautin-1 represents a novel therapeutics for prostate cancer

Background

Prostate cancer (PCa) remains a challenge worldwide. Due to the development of castration-resistance, traditional first-line androgen deprivation therapy (ADT) became powerlessness. Epidermal growth factor receptor (EGFR) is a well characterized therapeutic target to treat colorectal carcinoma and non-small cell lung cancer. Increasing studies have unraveled the significance of EGFR and its downstream signaling in the progression of castration-resistant PCa.

Method

MTS, colony formation and Edu staining assays were used to analyze the cell proliferation of PCa cells. Flow cytometry was used to analyze PCa cell cycle distribution and cell apoptosis. Western blot was used to measure the expression of key proteins associated with cell cycle progression, apoptosis and EGFR signaling pathways. Transfection of exogenous small interfering RNA (siRNA) or plasmid was used to intervene specific gene expression. Nude mouse model was employed to test the in vivo effect of Spautin-1.

Results

The current study reveals that Spautin-1, a known inhibitor of ubiquitin-specific peptidase 10 (USP10) and USP13, inhibits EGFR phosphorylation and the activation of its downstream signaling. Inhibition of EGFR signaling induced by Spautin-1 leads to cell cycle arrest and apoptosis of PCa in a USP10/USP13 independent manner. The application of Spautin-1 reduces the expression of glucose transporter 1 (Glut1) and dramatically induces cell death under glucose deprivation condition. In vivo experiments show a potent anti-tumor effect of Spautin-1 alone and in combination with Enzalutamide.

Conclusion

This study demonstrates the therapeutic potential of EGFR signaling inhibition by the use of Spautin-1 for PCa treatment.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1165-4) contains supplementary material, which is available to authorized users.

Skin tissue engineering: wound healing based on stem-cell-based therapeutic strategies

Normal wound healing is a dynamic and complex multiple phase process involving coordinated interactions between growth factors, cytokines, chemokines, and various cells. Any failure in these phases may lead wounds to become chronic and have abnormal scar formation. Chronic wounds affect patients' quality of life, since they require repetitive treatments and incur considerable medical costs. Thus, much effort has been focused on developing novel therapeutic approaches for wound treatment. Stem-cell-based therapeutic strategies have been proposed to treat these wounds. They have shown considerable potential for improving the rate and quality of wound healing and regenerating the skin. However, there are many challenges for using stem cells in skin regeneration. In this review, we present some sets of the data published on using embryonic stem cells, induced pluripotent stem cells, and adult stem cells in healing wounds. Additionally, we will discuss the different angles whereby these cells can contribute to their unique features and show the current drawbacks.

Harnessing the potential of therapeutic agents to safeguard bone health in prostate cancer

Background

Patients with prostate cancer are at risk of impaired bone health. Prostate cancer has a propensity to metastasize to bone, after which patients are at risk of skeletal-related events (SREs). These complications are associated with increased mortality, substantial pain, and reduced quality of life. Patients are also at risk of bone loss due to androgen deprivation therapy (ADT), which can be compounded in elderly patients with reduced bone density. It is essential, therefore, that aspects of bone health and therapies able to prevent the occurrence of SREs are considered throughout the clinical course of prostate cancer.

Methods

We reviewed the literature regarding the molecular mechanisms underpinning bone lesion formation, the modes of action of therapies that prevent SREs, and the efficacy and safety of these therapies in patients with hormone-sensitive or castration-resistant prostate cancer (CRPC).

Results

Therapies such as denosumab (a RANKL inhibitor) and zoledronic acid (a bisphosphonate) were indicated for prevention of SREs. Radium-223 dichloride also has proven efficacy in delaying symptomatic SREs, as well as in improving overall survival through effects on bone metastases. Before development of bone metastases, low-dose denosumab may also be used for treatment of ADT-associated bone loss. Denosumab may also have the potential to delay bone metastases development in patients with CRPC, although this is not currently an approved indication. The safety profile of therapies to prevent SREs should be considered. This review consolidates the available evidence on use of denosumab and bisphosphonates in prostate cancer, differentiated by hormone-sensitive and castration-resistant disease.

Conclusions

There is convincing evidence to support the use of denosumab and bisphosphonates to maintain bone health in patients with prostate cancer. Clinicians should be mindful of the adverse event risk profile of these therapies.

Decline in arylsulfatase B expression increases EGFR expression by inhibiting the protein-tyrosine phosphatase SHP2 and activating JNK in prostate cells

Epidermal growth factor receptor (EGFR) has a crucial role in cell differentiation and proliferation and cancer, and its expression appears to be up-regulated when arylsulfatase B (ARSB or GalNAc-4-sulfatase) is reduced. ARSB removes 4-sulfate groups from the nonreducing end of dermatan sulfate and chondroitin 4-sulfate (C4S), and its decreased expression has previously been reported to inhibit the activity of the ubiquitous protein-tyrosine phosphatase, nonreceptor type 11 (SHP2 or PTPN11). However, the mechanism by which decline in ARSB leads to decline in SHP2 activity is unclear. Here, we show that SHP2 binds preferentially C4S, rather than chondroitin 6-sulfate, and confirm that SHP2 activity declines when ARSB is silenced. The reduction in ARSB activity, and the resultant increase in C4S, increased the expression of EGFR (Her1/ErbB1) in human prostate stem and epithelial cells. The increased expression of EGFR occurred after 1) the decline in SHP2 activity, 2) enhanced c-Jun N-terminal kinase (JNK) activity, 3) increased nuclear DNA binding by c-Jun and c-Fos, and 4) EGFR promoter activation. In response to exogenous EGF, there was increased bromodeoxyuridine incorporation, consistent with enhanced cell proliferation. These findings indicated that ARSB and chondroitin 4-sulfation affect the activation of an important dual phosphorylation threonine-tyrosine kinase and the mRNA expression of a critical tyrosine kinase receptor in prostate cells. Restoration of ARSB activity with the associated reduction in C4S may provide a new therapeutic approach for managing malignancies in which EGFR-mediated tyrosine kinase signaling pathways are active.

Restoration of microRNA-130b expression suppresses osteosarcoma cell malignant behavior in vitro

The alteration of microRNA (miR)-130b expression has been associated with promoting or suppressing numerous types of human cancer. A previous study evaluated the expression level of miR-130b in osteosarcoma tissues, and subsequently investigated the effects of miR-130b on the regulation of osteosarcoma cells malignant behavior in vitro. The study revealed that miR-130b expression levels were significantly reduced in osteosarcoma tissues and cell lines, compared with in adjacent tissues or normal cell lines. The expression of miR-130b inhibited the proliferation of osteosarcoma U-2OS and Saos-2 cells and impaired their ability to migrate, invade and form colonies. Furthermore, analysis using TargetScan and a dual-luciferase reporter assay demonstrated that miR-130b directly interacted with the 3′-untranslated region of transforming growth factor α (TGFA) and suppressed TGFA expression. TGFA and miR-130b were also inversely expressed in osteosarcoma tissues. In addition, expression of TGFA was able to alter miR-130-regulated osteosarcoma cell proliferation, migration and invasion. Thus, the present study demonstrated that miR-130b was downregulated in osteosarcoma tissues and cell lines, whereas the expression of miR-130b suppressed osteosarcoma cell malignant behavior. At the gene level, miR-130 directly targets and inhibits TGFA expression, in addition to phosphorylated protein kinase B and epidermal growth factor receptor expression levels. Further study is required to evaluate miR-130b antitumor activity in osteosarcoma.

Disruption of ETV6 leads to TWIST1-dependent progression and resistance to epidermal growth factor receptor tyrosine kinase inhibitors in prostate cancer

BACKGROUND

ETS variant gene 6 (ETV6) is a putative tumor suppressor and repressed by epidermal growth factor receptor (EGFR) signaling in prostate cancer. Since EGFR antagonists seem ineffective in castration-resistant prostate cancer (CRPC), we aim to study the role of ETV6 in the development of drug resistance.

METHODS

Etv6 target gene was validated by ChIP and promoter reporter assays. Correlation of ETV6 and TWIST1 was analyzed in human clinical datasets and tissue samples. Migration, invasion, and metastasis assays were used to measure the cellular responses after perturbation of ETV6 -TWIST1 axis. Proliferation and tumor growth in xenograft model were performed to evaluate the drug sensitivities of EGFR-tyrosine kinase inhibitors (TKIs).

RESULTS

ETV6 inhibits TWIST1 expression and disruption of ETV6 promotes TWIST1-dependent malignant phenotypes. Importantly, ETV6 is required to the anti-proliferation effects of EGFR-TKIs, partly due to the inhibitory function of ETV6 on TWIST1. We also found that EGFR-RAS signaling is tightly controlled by ETV6, supporting its role in TKI sensitivity.

CONCLUSIONS

Our study demonstrates that disruption of ETV6 contributes to EGFR-TKI resistance, which is likely due to derepression of TWIST1 and activation of EGFR-RAS signaling. Our results implicate ETV6 as a potential marker for predicting efficacy of an EGFR-targeted anticancer approach. Combination treatment of TWIST1 inhibitors could sensitize the anti-proliferation effects of EGFR-TKIs.

Multigene Profiling of CTCs in mCRPC Identifies a Clinically Relevant Prognostic Signature

The trend toward precision-based therapeutic approaches dictated by molecular alterations offers substantial promise for men with metastatic castration-resistant prostate cancer (mCRPC). However, current approaches for molecular characterization are primarily tissue based, necessitating serial biopsies to understand changes over time and are limited by the challenges inherent to extracting genomic material from predominantly bone metastases. Therefore, a circulating tumor cell (CTC)-based assay was developed to determine gene expression across a panel of clinically relevant and potentially actionable prostate cancer-related genes. CTCs were isolated from the whole blood of mCRPC patients (n = 41) and multiplex qPCR was performed to evaluate expression of prostate cancer-related target genes (n = 78). A large fraction of patients (27/41, 66%) had detectable CTCs. Increased androgen receptor (AR) expression (70% of samples) and evidence of Wnt signaling (67% of samples) were observed. The TMPRSS2:ERG fusion was expressed in 41% of samples, and the aggressive prostate cancer-associated long noncoding RNA SChLAP1 was upregulated in 70%. WNT5a [HR 3.62, 95% confidence interval (CI), 1.63-8.05, P = 0.002], AURKA (HR 5.56, 95% CI, 1.79-17.20, P = 0.003), and BMP7 (HR 3.86, 95% CI, 1.60-9.32, P = 0.003) were independently predictive of overall survival (FDR < 10%) after adjusting for a panel of previously established prognostic variables in mCRPC (Halabi nomogram). A model including Halabi, WNT5a, and AURKA expression, termed the miCTC score, outperformed the Halabi nomogram alone (AUC = 0.89 vs. AUC = 0.70). Understanding the molecular landscape of CTCs has utility in predicting clinical outcomes in patients with aggressive prostate cancer and provides an additional tool in the arsenal of precision-based therapeutic approaches in oncology.Implications: Analysis of CTC gene expression reveals a clinically prognostic "liquid biopsy" signature in patients with metastatic castrate-resistance prostate cancer. Mol Cancer Res; 16(4); 643-54. ©2018 AACR.

Androgen receptor expression on circulating tumor cells in metastatic breast cancer

Purpose

Methods

Results

Conclusions

Combination of Carmustine and Selenite Inhibits EGFR Mediated Growth Signaling in Androgen-Independent Prostate Cancer Cells

Although aberrant androgen receptor (AR) signaling is a central mechanism for castration resistant prostate cancer (CRPC) progression, AR-independent growth signaling is also present in CRPC. The current therapeutic options for patients with CRPC are limited and new drugs are desperately needed to eliminate these crucial growth signaling pathways. We have previously shown that combination of carmustine and selenite effectively induces apoptosis and growth inhibition by targeting AR and AR-variants in CRPC cells. High levels of EGFR expression present in the CRPC cells mediates the cell proliferation via AR-independent growth signaling mechanisms. Therefore, in this study, we investigated whether the combination of carmustine and selenite could inhibit EGFR mediated growth signaling and induce apoptosis in androgen independent-AR negative prostate cancer cells. EGF exposure dose and time dependently increased phospho-EGFR (Tyr845, Tyr1068, and Tyr1045), pAkt (Ser473), and pERK1/2 (Thr204/Tyr202) protein expression levels in AIPC cells. Combination of carmustine and selenite treatment markedly suppressed EGF-stimulated proliferation and survival of AIPC cells and effectively induced apoptosis. The ROS generated by the combination of carmustine and selenite exhibited a strong inhibition on EGF stimulated EGFR and its downstream signaling molecules such as Akt, NF-kB, ERK1/2, and Cyclin D1. Individual agent treatment showed only partial effect. Overall, our findings demonstrated that the combination of carmustine and selenite treatment dramatically inhibits EGFR signaling, proliferation, and induces apoptosis in AIPC cells, suggesting a potential candidate for the treatment of CRPC. The results of the study further suggest that the combination of carmustine and selenite treatment can overcome EGFR mediated AR-independent growth response in CRPC during anti-androgen therapy. J. Cell. Biochem. 118: 4331-4340, 2017. © 2017 Wiley Periodicals, Inc.

Dissecting major signaling pathways in prostate cancer development and progression: Mechanisms and novel therapeutic targets

Prostate cancer (PCa) is the most frequently diagnosed non-cutaneous malignancy and leading cause of cancer mortality in men. At the initial stages, prostate cancer is dependent upon androgens for their growth and hence effectively combated by androgen deprivation therapy (ADT). However, most patients eventually recur with an androgen deprivation-resistant phenotype, referred to as castration-resistant prostate cancer (CRPC), a more aggressive form for which there is no effective therapy presently available. The current review is an attempt to cover and establish an understanding of some major signaling pathways implicated in prostate cancer development and castration-resistance, besides addressing therapeutic strategies that targets the key signaling mechanisms.