Heat shock protein 27 confers resistance to androgen ablation and chemotherapy in prostate cancer cells through eIF4E

Protein translation: biological processes and therapeutic strategies for human diseases

Protein translation is a tightly regulated cellular process that is essential for gene expression and protein synthesis. The deregulation of this process is increasingly recognized as a critical factor in the pathogenesis of various human diseases. In this review, we discuss how deregulated translation can lead to aberrant protein synthesis, altered cellular functions, and disease progression. We explore the key mechanisms contributing to the deregulation of protein translation, including functional alterations in translation factors, tRNA, mRNA, and ribosome function. Deregulated translation leads to abnormal protein expression, disrupted cellular signaling, and perturbed cellular functions- all of which contribute to disease pathogenesis. The development of ribosome profiling techniques along with mass spectrometry-based proteomics, mRNA sequencing and single-cell approaches have opened new avenues for detecting diseases related to translation errors. Importantly, we highlight recent advances in therapies targeting translation-related disorders and their potential applications in neurodegenerative diseases, cancer, infectious diseases, and cardiovascular diseases. Moreover, the growing interest lies in targeted therapies aimed at restoring precise control over translation in diseased cells is discussed. In conclusion, this comprehensive review underscores the critical role of protein translation in disease and its potential as a therapeutic target. Advancements in understanding the molecular mechanisms of protein translation deregulation, coupled with the development of targeted therapies, offer promising avenues for improving disease outcomes in various human diseases. Additionally, it will unlock doors to the possibility of precision medicine by offering personalized therapies and a deeper understanding of the molecular underpinnings of diseases in the future.

Castration-Resistant Prostate Cancer: From Uncovered Resistance Mechanisms to Current Treatments

Prostate cancer (PC) is the second most common cancer in men worldwide. Despite recent advances in diagnosis and treatment, castration-resistant prostate cancer (CRPC) remains a significant medical challenge. Prostate cancer cells can develop mechanisms to resist androgen deprivation therapy, such as AR overexpression, AR mutations, alterations in AR coregulators, increased steroidogenic signaling pathways, outlaw pathways, and bypass pathways. Various treatment options for CRPC exist, including androgen deprivation therapy, chemotherapy, immunotherapy, localized or systemic therapeutic radiation, and PARP inhibitors. However, more research is needed to combat CRPC effectively. Further investigation into the underlying mechanisms of the disease and the development of new therapeutic strategies will be crucial in improving patient outcomes. The present work summarizes the current knowledge regarding the underlying mechanisms that promote CRPC, including both AR-dependent and independent pathways. Additionally, we provide an overview of the currently approved therapeutic options for CRPC, with special emphasis on chemotherapy, radiation therapy, immunotherapy, PARP inhibitors, and potential combination strategies.

Untangling the complexity of heat shock protein 27 in cancer and metastasis

Heat shock protein 27 is a type of molecular chaperone whose expression gets up-regulated due to reaction towards different stressful triggers including anticancer treatments. It is known to be a major player of resistance development in cancer cells, whereby cells are sheltered against the therapeutics that normally activate apoptosis. Heat shock protein 27 (HSP27) is one of the highly expressed proteins during various cellular insults and is a strong tumor survival factor. HSP27 influences various cellular pathways associated with cancer cell survival and growth such as apoptosis, autophagy, metastasis, angiogenesis, epithelial to mesenchymal transition, etc. HSP27 is molecular machinery which prevents the clumping of numerous substrates or client proteins which get mutated in cancer. It has been reported in several studies that targeting HSP27 is difficult because of its dynamic structure and absence of an ATP-binding site. Here, in this review, we have summarized different modulators of HSP27 and their mechanism of action as well. Effect of deregulated HSP27 in various cancer models, limitations of targeting HSP27, resistance against the conventional drugs generated due to the overexpression of HSP27, and measures to counteract this effect have also been discussed here in detail.

DDX5 mRNA-targeting antisense oligonucleotide as a new promising therapeutic in combating castration-resistant prostate cancer

The heat shock protein 27 (Hsp27) has emerged as a principal factor of the castration-resistant prostate cancer (CRPC) progression. Also, an antisense oligonucleotide (ASO) against Hsp27 (OGX-427 or apatorsen) has been assessed in different clinical trials. Here, we illustrate that Hsp27 highly regulates the expression of the human DEAD-box protein 5 (DDX5), and we define DDX5 as a novel therapeutic target for CRPC treatment. DDX5 overexpression is strongly correlated with aggressive tumor features, notably with CRPC. DDX5 downregulation using a specific ASO-based inhibitor that acts on DDX5 mRNAs inhibits cell proliferation in preclinical models, and it particularly restores the treatment sensitivity of CRPC. Interestingly, through the identification and analysis of DDX5 protein interaction networks, we have identified some specific functions of DDX5 in CRPC that could contribute actively to tumor progression and therapeutic resistance. We first present the interactions of DDX5 and the Ku70/80 heterodimer and the transcription factor IIH, thereby uncovering DDX5 roles in different DNA repair pathways. Collectively, our study highlights critical functions of DDX5 contributing to CRPC progression and provides preclinical proof of concept that a combination of ASO-directed DDX5 inhibition with a DNA damage-inducing therapy can serve as a highly potential novel strategy to treat CRPC.

The role of heat shock proteins in metastatic colorectal cancer: A review

Heat shock proteins (HSPs) are a large molecular chaperone family classified by their molecular weights, including HSP27, HSP40, HSP60, HSP70, HSP90, and HSP110. HSPs are likely to have antiapoptotic properties and participate actively in various processes such as tumor cell proliferation, invasion, metastases, and death. In this review, we discuss comprehensively the functions of HSPs associated with the progression of colorectal cancer (CRC) and metastasis and resistance to cancer therapy. Taken together, HSPs have numerous clinical applications as biomarkers for cancer diagnosis and prognosis and potential therapeutic targets for CRC and its related metastases.

Heat shock proteins: Biological functions, pathological roles, and therapeutic opportunities

The heat shock proteins (HSPs) are ubiquitous and conserved protein families in both prokaryotic and eukaryotic organisms, and they maintain cellular proteostasis and protect cells from stresses. HSP protein families are classified based on their molecular weights, mainly including large HSPs, HSP90, HSP70, HSP60, HSP40, and small HSPs. They function as molecular chaperons in cells and work as an integrated network, participating in the folding of newly synthesized polypeptides, refolding metastable proteins, protein complex assembly, dissociating protein aggregate dissociation, and the degradation of misfolded proteins. In addition to their chaperone functions, they also play important roles in cell signaling transduction, cell cycle, and apoptosis regulation. Therefore, malfunction of HSPs is related with many diseases, including cancers, neurodegeneration, and other diseases. In this review, we describe the current understandings about the molecular mechanisms of the major HSP families including HSP90/HSP70/HSP60/HSP110 and small HSPs, how the HSPs keep the protein proteostasis and response to stresses, and we also discuss their roles in diseases and the recent exploration of HSP related therapy and diagnosis to modulate diseases. These research advances offer new prospects of HSPs as potential targets for therapeutic intervention.

Revisiting the Old Data of Heat Shock Protein 27 Expression in Squamous Cell Carcinoma: Enigmatic HSP27, More Than Heat Shock

Initially discovered to be induced by heat shock, heat shock protein 27 (HSP27, also called HSPB1), a member of the small HSP family, can help cells better withstand or avoid heat shock damage. After years of studies, HSP27 was gradually found to be extensively engaged in various physiological or pathophysiological activities. Herein, revisiting the previously published data concerning HSP27, we conducted a critical review of the literature regarding its role in squamous cell carcinoma (SCC) from the perspective of clinicopathological and prognostic significance, excluding studies conducted on adenocarcinoma, which is very different from SCC, to understand the enigmatic role of HSP27 in the tumorigenesis of SCC, including normal mucosa, dysplasia, intraepithelial neoplasm, carcinoma in situ and invasive SCC.

The Role of Hsp27 in Chemotherapy Resistance

Heat shock protein (Hsp)-27 is a small-sized, ATP-independent, chaperone molecule that is overexpressed under conditions of cellular stress such as oxidative stress and heat shock, and protects proteins from unfolding, thus facilitating proteostasis and cellular survival. Despite its protective role in normal cell physiology, Hsp27 overexpression in various cancer cell lines is implicated in tumor initiation, progression, and metastasis through various mechanisms, including modulation of the SWH pathway, inhibition of apoptosis, promotion of EMT, adaptation of CSCs in the tumor microenvironment and induction of angiogenesis. Investigation of the role of Hsp27 in the resistance of various cancer cell types against doxorubicin, herceptin/trastuzumab, gemcitabine, 5-FU, temozolomide, and paclitaxel suggested that Hsp27 overexpression promotes cancer cell survival against the above-mentioned chemotherapeutic agents. Conversely, Hsp27 inhibition increased the efficacy of those chemotherapy drugs, both in vitro and in vivo. Although numerous signaling pathways and molecular mechanisms were implicated in that chemotherapy resistance, Hsp27 most commonly contributed to the upregulation of Akt/mTOR signaling cascade and inactivation of p53, thus inhibiting the chemotherapy-mediated induction of apoptosis. Blockage of Hsp27 could enhance the cytotoxic effect of well-established chemotherapeutic drugs, especially in difficult-to-treat cancer types, ultimately improving patients' outcomes.

Overcoming prostate cancer drug resistance with a novel organosilicon small molecule

A major challenge to the treatment of advanced prostate cancer (PCa) is the development of resistance to androgen-deprivation therapy (ADT) and chemotherapy. It is imperative to discover effective therapies to overcome drug resistance and improve clinical outcomes. We have developed a novel class of silicon-containing compounds and evaluated the anticancer activities and mechanism of action using cellular and animal models of drug-resistant PCa. Five organosilicon compounds were evaluated for their anticancer activities in the NCI-60 panel and established drug-resistant PCa cell lines. GH1504 exhibited potent in vitro cytotoxicity in a broad spectrum of human cancer cells, including PCa cells refractory to ADT and chemotherapy. Molecular studies identified several potential targets of GH1504, most notably androgen receptor (AR), AR variant 7 (AR-v7) and survivin. Mechanistically, GH1504 may promote the protein turnover of AR, AR-v7 and survivin, thereby inducing apoptosis in ADT-resistant and chemoresistant PCa cells. Animal studies demonstrated that GH1504 effectively inhibited the in vivo growth of ADT-resistant CWR22Rv1 and chemoresistant C4-2B-TaxR xenografts in subcutaneous and intraosseous models. These preclinical results indicated that GH1504 is a promising lead that can be further developed as a novel therapy for drug-resistant PCa.

Menin inhibition suppresses castration-resistant prostate cancer and enhances chemosensitivity

Disease progression and therapeutic resistance of prostate cancer (PC) are linked to multiple molecular events that promote survival and plasticity. We previously showed that heat shock protein 27 (HSP27) acted as a driver of castration-resistant phenotype (CRPC) and developed an oligonucleotides antisense (ASO) against HSP27 with evidence of anti-cancer activity in men with CRPC. Here, we show that the tumor suppressor Menin (MEN1) is highly regulated by HSP27. Menin is overexpressed in high-grade PC and CRPC. High MEN1 mRNA expression is associated with decreased biochemical relapse-free and overall survival. Silencing Menin with ASO technology inhibits CRPC cell proliferation, tumor growth, and restores chemotherapeutic sensitivity. ChIP-seq analysis revealed differential DNA binding sites of Menin in various prostatic cells, suggesting a switch from tumor suppressor to oncogenic functions in CRPC. These data support the evaluation of ASO against Menin for CRPC.

In silico screening and exploration into phenotypic alterations of deleterious oncogenic single nucleotide polymorphisms in HSPB1 gene

A small heat shock protein, HSP27, encoded by HSPB1 gene strongly favors survival, proliferation and metastasis of cancer cells and its expression is dependent on post-translational modifications like phosphorylation. This study performed an extensive in silico screening of 20 deleterious non-synonymous SNPs in the coding region of HSPB1 gene, among which four were identified to be cancer associated. The SNP variant I181S introduced a new phosphorylation site in position 181, which might elevate the protein's activation potential. Emergence of other post-translational modifications was also observed in SNP variants: L144P and E130K.Significant conformational changes were observed in I181S, L144P and E130K SNP variants with respect to wild-type HSP27. These SNPs appear in one among 10⁵ individuals, making them more susceptible towards cancer. This study would therefore, instigate development of novel biomarkers for cancer risk detection and would provide a detailed understanding towards varied cancer susceptibility of human population.

The Role of RNA Modifications and RNA-modifying Proteins in Cancer Therapy and Drug Resistance

The advent of new genome-wide sequencing technologies has uncovered abnormal RNA modifications and RNA editing in a variety of human cancers. The discovery of reversible RNA N6-methyladenosine (RNA: m⁶A) by fat mass and obesity-associated protein (FTO) demethylase has led to exponential publications on the pathophysiological functions of m⁶A and its corresponding RNA modifying proteins (RMPs) in the past decade. Some excellent reviews have summarized the recent progress in this field. Compared to the extent of research into RNA: m⁶A and DNA 5-methylcytosine (DNA: m⁵C), much less is known about other RNA modifications and their associated RMPs, such as the role of RNA: m⁵C and its RNA cytosine methyltransferases (RCMTs) in cancer therapy and drug resistance. In this review, we will summarize the recent progress surrounding the function, intramolecular distribution and subcellular localization of several major RNA modifications, including 5' cap N7-methylguanosine (m7G) and 2'-O-methylation (Nm), m⁶A, m⁵C, A-to-I editing, and the associated RMPs. We will then discuss dysregulation of those RNA modifications and RMPs in cancer and their role in cancer therapy and drug resistance.

Nucleoside-Lipid-Based Nanoparticles for Phenazine Delivery: A New Therapeutic Strategy to Disrupt Hsp27-eIF4E Interaction in Castration Resistant Prostate Cancer

Heat shock protein 27 (Hsp27) has an established role in tumor progression and chemo-resistance of castration-resistant prostate cancer (CRPC). Hsp27 protects eukaryotic translation initiation factor 4E (eIF4E) from degradation, thereby maintaining survival during treatment. Phenazine derivative compound #14 was demonstrated to specifically disrupt Hsp27/eIF4E interaction and significantly delay castration-resistant tumor progression in prostate cancer xenografts. In the present work, various strategies of encapsulation of phenazine #14 with either DOTAU (N-[5′-(2′,3′-dioleoyl)uridine]-N′,N′,N′-trimethylammonium tosylate) and DOU-PEG₂₀₀₀ (5′-PEG2000-2′,3′-dioleoyluridine) nucleolipids (NLs) were developed in order to improve its solubilization, biological activity, and bioavailability. We observed that NLs-encapsulated phenazine #14-driven Hsp27-eIF4E interaction disruption increased cytotoxic effects on castration-resistant prostate cancer cell line and inhibited tumor growth in castration-resistant prostate cancer cell xenografted mice compared to phenazine #14 and NLs alone. Phenazine #14 NL encapsulation might represent an interesting nanostrategy for CRPC therapy.

Small-Molecule HSP27 Inhibitor Abolishes Androgen Receptors in Glioblastoma

Androgen receptor (AR) contributes to the progression of glioblastoma (GBM), and antiandrogen agents have the potential to be used for the treatment of GBM. However, AR mutation commonly happens in GBM, which makes the antiandrogen agents less effective. Heat shock 27 kDa protein (HSP27) is a well-documented chaperone protein to stabilize ARs. Inhibition of HSP27 results in AR degradation regardless of the mutation status of ARs, which makes HSP27 a good target to abolish ARs in GBM. Compound I is a HSP27 inhibitor that significantly induces AR degradation in GBM cells via the proteasomal pathway, and it selectively inhibits AR-overexpressed GBM cell growth with IC50 values around 5 nM. The compound also significantly inhibits in vivo GBM xenograft at 20 mg/kg and does not cause toxicity to mice up to 80 mg/kg. These results suggest that targeting HSP27 to induce AR degradation in GBM is a promising and novel treatment.

Novel aryltriazole acyclic C-azanucleosides as anticancer candidates

Nucleoside analogues represent an important class of drug candidates. With the aim of searching for novel bioactive nucleosides, we developed an efficient synthetic way to construct a series of aryl 1,2,3-triazole acyclic C-azanucleosides via Huisgen 1,3-dipolar cycloaddition. The aryl 1,2,3-triazole motifs within these azanucleosides showed coplanar features, suggesting they could act as surrogates for large planar aromatic systems or nucleobases. Moreover, several aryltriazole acyclic C-azanucleosides bearing long alkyl chains exhibited potent antiproliferative activity against various cancer cell lines via induction of apoptosis. Most interestingly, the lead compound significantly down-regulated the key proteins involved in the heat shock response pathway, representing the first anticancer acyclic azanucleoside with such a mode of action. These novel aryl 1,2,3-triazole cyclic C-azanucleosides therefore serve as promising paradigms for further exploring anticancer drug candidates.

A critical update on the strategies towards modulators targeting androgen receptors

Prostate cancer is the most common carcinoma of the male urinary system in developed countries. Androgen deprivation therapy has been commonly used in the treatment of prostate cancer for decades, but most patients will inevitably develop into more aggressive castration-resistant prostate cancer. Therefore, novel strategies are urgent to address this resistance mechanism. In this review, we discussed some new strategies for targeting androgen receptors through degradation pathways as potential treatments for prostate cancer.

Novel triazole nucleoside analogues promote anticancer activity via both apoptosis and autophagy

Novel triazole nucleosides developed by the strategy of “terminal N,N-dimethylation” displayed anticancer activity mediated via apoptosis and autophagy.

Particle filter de-noising of voxel-specific time-activity-curves in personalized 177Lu therapy

BACKGROUND

Currently, there is a high interest in ¹⁷⁷Lu targeted radionuclide therapies, which could be attributed to favorable results obtained from ¹⁷⁷Lu compounds targeting neuro-endocrine and prostate tumors. SPECT based dosimetry could be used for deriving dose values for individual voxels, as is the standard in external-beam radiation-therapy (EBRT). For this a time-activity-curve (TAC) at voxel resolution and also a voxel-wise modeling of radiation energy deposition are necessary. But a voxel-wise determination of TACs is problematic, since several confounding factors exist, such as e.g. poor count-statistics or registration inaccuracies, which add noise to the observed activity states. A particle filter (PF) is a class of methods which applies regularization based on a model of the temporal evolution of activity states. The aim of this study is to introduce the application of PFs for de-noising of per-voxel time-activity curves.

METHODS

We applied a PF for de-noising the TACs of 26 patients, who underwent ¹⁷⁷Lu-DOTATOC or -PSMA therapy. The TACs were obtained from fully-quantitative, serial SPECT(/CT) data, acquired at 4h, 24h, 48h, 72h p.i. The model used in the PF was a mono-exponential decay and its free parameters were determined based on objective criteria. The time-integrated activities (TIA) resulting from the PF (PFF) were compared to the results of a mono-exponential fit (SF) of individual voxels in several volumes of interest (kidneys, spleen, tumors). Additionally, an organ-averaged TIA was derived from whole-organ VOIs and subsequent curve-fitting. This whole-organ TIA was also compared to the whole-organ TIAs obtained from summation of the voxel-wise TIAs from PFF and SF.

RESULTS

The number of particles was set to 1000. Optimal values for noise of observations and noise of the model were 0.25 and 0.5, respectively. The deviation of whole-organ TIAs from conventional organ-based dosimetry and the summation of the voxel-wise TIAs was substantial for SF (kidneys -22.3%, spleen -49.6%, tumor -60.0%), as well as for PFF (kidneys -37.1%, spleen -57.9%, tumor -70.9%). The distribution of voxel-wise half-lives resulting from the PFF method was considerably closer to the organ-averaged value, and the number of implausibly long half-lives (>physical HL) was reduced.

CONCLUSION

The PFF leads to voxel-wise half-lives, which are more plausible than those resulting from SF. However, one has to admit that voxel-wise fitting generally leads to considerable deviations from the organ-averaged TIA as obtained by conventional whole-organ evaluation. Unfortunately, we did not have ground-truth TIA of our patient data and proper ground-truth could even be impossible to obtain. Nevertheless, there are strong indicators that particle filtering can be used for reducing voxel-wise TAC noise.

The Multiple Roles and Therapeutic Potential of Molecular Chaperones in Prostate Cancer

Prostate cancer (PCa) is one of the most common cancer types in men worldwide. Heat shock proteins (HSPs) are molecular chaperones that are widely implicated in the pathogenesis, diagnosis, prognosis, and treatment of many cancers. The role of HSPs in PCa is complex and their expression has been linked to the progression and aggressiveness of the tumor. Prominent chaperones, including HSP90 and HSP70, are involved in the folding and trafficking of critical cancer-related proteins. Other members of HSPs, including HSP27 and HSP60, have been considered as promising biomarkers, similar to prostate-specific membrane antigen (PSMA), for PCa screening in order to evaluate and monitor the progression or recurrence of the disease. Moreover, expression level of chaperones like clusterin has been shown to correlate directly with the prostate tumor grade. Hence, targeting HSPs in PCa has been suggested as a promising strategy for cancer therapy. In the current review, we discuss the functions as well as the role of HSPs in PCa progression and further evaluate the approach of inhibiting HSPs as a cancer treatment strategy.

Eukaryotic initiation factor 4E (eIF4E): A recap of the cap-binding protein

Eukaryotic initiation factor 4E (eIF4E), a fundamental effector and rate limiting element of protein synthesis, binds the 7-methylguanosine cap at the 5' end of eukaryotic messenger RNA (mRNA) specifically as a constituent of eIF4F translation initiation complex thus facilitating the recruitment of mRNA to the ribosomes. This review focusses on the engagement of signals contributing to growth factor originated maxim and their role in the activation of eIF4E to achieve a collective influence on cellular growth, with a key focus on conjuring vital processes like protein synthesis. The review invites considerable interest in elevating the appeal of eIF4E beyond its role in regulating translation viz a viz cancer genesis, attributed to its phosphorylation state that improves the prospect for the growth of the cancerous cell. This review highlights the latest studies that have envisioned to target these pathways and ultimately the translational machinery for therapeutic intervention. The review also brings forward the prospect of eIF4E to act as a converging juncture for signaling pathways like mTOR/PI3K and Mnk/MAPK to promote tumorigenesis.

Silencing Heat Shock Protein 27 Inhibits the Progression and Metastasis of Colorectal Cancer (CRC) by Maintaining the Stability of Stromal Interaction Molecule 1 (STIM1) Proteins

The incidence of colorectal cancer (CRC) has significantly increased in recent decades, and this disease has become an important health issue worldwide. Currently, there is no useful prognostic or diagnostic biomarker for CRC. Heat shock protein 27 (HSP27) is a chaperone that interacts with many proteins. HSP27 has been shown to be overexpressed in many cancers, including colon cancer, and its overexpression is related to poor disease outcome. Although the importance of HSP27 as a biomarker cannot be underrated, its detailed mechanisms in colon cancer are still unclear. In vitro studies have indicated that silencing HSP27 reduces the proliferation, migration and invasion of colon cancer cells, and xenograft models have shown that silencing HSP27 decreases tumor progression. Tissue array results showed that colon cancer patients with high expression of HSP27 exhibited poor prognosis. In addition, we found a reduction of calcium influx through a decrease in STIM1 protein after HSP27 was abolished. The formation of puncta was decreased in HSP27 knockdown (HSP27KD) cells after thapsigargin (TG) treatment. Finally, we confirmed that the reduction of STIM1 after HSP27 silencing may be due to a loss of STIM1 stability instead of transcription. HSP27 may interact with STIM1 but not Orai1, as shown by immunoprecipitation assays. HSP27 and STIM1 were co-expressed in CRC specimens. Our study showed that HSP27 is a key mediator in the progression and metastasis of CRC by regulating the store-operated calcium entry. This novel pathway may provide a new direction for development of therapeutic strategies for CRC.

Interference with the androgen receptor protein stability in therapy-resistant prostate cancer

The androgen receptor (AR) plays a central role in the pathogenesis of prostate cancer (PCa). Most PCa cases develop eventually from an androgen-dependent stage to castration-resistant prostate cancer (CRPC) with AR-signaling still being active. Thus, inhibition of AR remains a well-established promising drug target in CRPC. However, despite the improvements of current treatment for CRPC by targeting the AR, the evolution of adaptive AR-signaling leads to therapy-resistant CRPC. Treatment failure is based mostly on the inability to keep AR under long-term restraint due to adaptive responses of AR-signaling. One underlying mechanism appears to be the increased AR protein stability. Therefore, the regulation of AR protein stability and its degradation is another interesting path that could enhance our knowledge of carcinogenesis and tumor evolution possibly leading to novel therapeutic targets. In this review, we discuss various molecular mechanisms and factors that stabilize AR protein levels directly or indirectly. We summarize novel approaches to interfere with AR stability including targeting the glucocorticoid receptor (GR), heat shock proteins, and co-chaperones as well as E3-ligases using small chimeric molecules. These novel approaches in combination with antiandrogen treatment inhibit PCa growth through the regulation of AR protein levels.

Hsp27 regulates epithelial mesenchymal transition, metastasis and proliferation in colorectal carcinoma

The primary factor associated with poor survival rate in patients with colorectal carcinoma (CRC) is the presence of metastasis. The underlying molecular mechanisms of CRC metastasis are yet to be fully elucidated. The present study investigated the function of heat shock protein 27 (Hsp27) on the invasion and proliferation of CRC cells. The clinical significance of Hsp27 was evaluated using tissue microarray analysis (n=81). Invasion and metastasis assays were used to determine the function of Hsp27 in CRC metastasis in vitro and in vivo using RNA interference and the ectopic expression of Hsp27. The upregulation of Hsp27 has been frequently identified in CRC tissues. Patients with CRC and a high expression level of Hsp27 have a reduced overall survival rate. Silencing Hsp27 inhibited the growth and invasion of CRC cells in vitro and in vivo, whereas ectopic overexpression of Hsp27 promoted the proliferation and invasion of CRC cells in vitro. Furthermore, depletion of Hsp27 expression inhibited the epithelial-to-mesenchymal transition (EMT), whilst ectopic overexpression of Hsp27 induced EMT. The results of the present study indicated that Hsp27 serves an important function in the aggressiveness of CRC through inducing EMT. Hsp27 suppression may represent a potential therapeutic option for the suppression of CRC progression.

eIF4E Phosphorylation in Prostate Cancer

Prostate cancer (PCa) progression involves a shift from endocrine to paracrine and eventually autocrine control resulting from alterations in molecular mechanisms in the cells. Deregulation of RNA translation is crucial for tumor cells to grow and proliferate; therefore, overactivation of the translation machinery is often observed in cancer. The two most important signal transduction pathways regulating PCa progression are PI3K/Akt/mTOR and Ras/MAPK. These two pathways converge on the eukaryotic translation initiation factor 4E (eIF4E) which binds to the protein scaffold eIF4G upon mechanistic target of rapamycin (mTOR) activation and is phosphorylated by the mitogen-activated protein kinase (MAPK) interacting protein kinases (Mnk1/2). This review describes the role of eIF4E in mRNA translation initiation mediated by its binding to the methylated 5′ terminal structure (m7G-cap) of many mRNAs, and the ability of many tumor cells to bypass this mechanism. Hormonal therapy and chemotherapy are two of the most prevalent therapies used in patients with advanced PCa, and studies have implicated a role for eIF4E phosphorylation in promoting resistance to both these therapies. It appears that eIF4E phosphorylation enhances the rate of translation of oncogene mRNAs to increase tumorigenicity.

A TRAMP-derived orthotopic prostate syngeneic (TOPS) cancer model for investigating anti-tumor treatments

BACKGROUND

Patients with advanced prostate cancer have limited curative options, therefore new treatments are needed. Mouse models play a pivotal role in the discovery and development of new treatments. In the present study, a TRAMP-derived Orthotopic Prostate Syngeneic (TOPS) mouse model was developed and found to provide a consistent means of monitoring tumor and metastatic responses to novel treatments.

METHODS

The mouse TOPS model was generated using luciferase transduced TRAMP-C2 prostate cancer cells that were orthotopically injected into Bl6 mice by ultrasound guidance. Tumor growth and development was monitored using ultrasound and bioluminescence imaging.

RESULTS

Tumors and metastases were consistently established and increases in tumor size correlated with increases in bioluminescence. In addition, when mice with an established tumor were castrated, tumor progression mirrored clinical progression. We further treated the TOPS model with an oncolytic Herpes Simplex virus and showed that we were able to monitor the therapeutic effect of the orthotopic tumor after virus treatment through IVIS imaging system.

CONCLUSION

We have developed a powerful animal model to advance the current selection of effective treatments for patients with advanced prostate cancer.

Noxa/HSP27 complex delays degradation of ubiquitylated IkBα in airway epithelial cells to reduce pulmonary inflammation

IFN-γ is known as a pro-inflammatory cytokine, but can also block inflammation in certain chronic diseases although the underlying mechanisms are poorly understood. We found that IFN-γ rapidly induced Noxa expression and that extent of inflammation by repeated house dust mite exposure was enhanced in noxa^-/- compared with noxa^+/+ mice. Noxa expression blocked transforming necrosis factor alpha (TNF-α)-induced nuclear translocation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and the production of pro-inflammatory cytokines. Noxa did not affect TNF-α-induced IκBα phosphorylation but the degradation of 48-chain-ubiquitylated IκBα. The Cys25 of Noxa was cross-linked with Cys137 of phospho-HSP27 and both proteins were required for blocking the degradation of ubiquitylated IκBα. Because phospho-HSP27 is present in airway epithelial cells and not in fibroblasts or thymocytes, we generated transgenic mice that inducibly expressed Noxa in airway epithelia. These mice showed protection from allergen-induced inflammation and mucous cell metaplasia by blocking nuclear translocation of NF-κB. Further, we identified a Noxa-derived peptide that prolonged degradation of 48-chain-ubiquitylated IκBα, blocked nuclear translocation of NF-κB, and reduced allergen-induced inflammation in mice. These results suggest that the anti-inflammatory role of the Noxa protein may be restricted to airway epithelial cells and the use of Noxa for therapy of chronic lung diseases may be associated with reduced side effects.

Overcoming HSP27-mediated resistance by altered dimerization of HSP27 using small molecules

Heat shock protein 27 (HSP27, HSPB1) is an anti-apoptotic protein characterized for its tumorigenic and metastatic properties, and now referenced as a major therapeutic target in many types of cancer. The biochemical properties of HSP27 rely on a structural oligomeric and dynamic organization that is important for its chaperone activity. Down-regulation by small interfering RNA or inhibition with a dominant-negative mutant efficiently counteracts the anti-apoptotic and protective properties of HSP27. However, unlike other HSPs such as HSP90 and HSP70, small molecule approaches for neutralization of HSP27 are not well established because of the absence of an ATP binding domain. Previously, we found that a small molecule, zerumbone (ZER), induced altered dimerization of HSP27 by cross linking the cysteine residues required to build a large oligomer, led to sensitization in combination with radiation. In this study, we identified another small molecule, a xanthone compound, more capable of altering dimeric HSP27 than ZER and yielding sensitization in human lung cancer cells when combined with HSP90 inhibitors or standard anticancer modalities such as irradiation and cytotoxic anticancer drugs. Therefore, altered dimerization of HSP27 represents a good strategy for anticancer therapy in HSP27-overexpressing cancer cells.

Sensitization of lung cancer cells by altered dimerization of HSP27

Heat shock protein 27 (HSP27, HSPB1) induces resistance to anticancer drugs in various cancer types, including non-small cell lung cancer (NSCLC). Therefore, pharmacological inhibition of HSP27 in NSCLC may be a good strategy for anticancer therapy. Unlike other HSPs such as HSP90 and HSP70, small molecule approaches for neutralization of HSP27 are not well established because of the absence of an ATP binding domain. Previously, small molecules with altered cross linking activity of HSP27, were identified to inhibit building a large oligomer led to sensitization in combination with radiation and chemotherapeutic drugs. In this study, a chromene compound, J2 that exhibited better cross-linking activity of HSP27 than xanthone compound, SW15 which was previously identified, was yielding sensitization to NSCLC cells with high expression of HSP27 when combined with HSP90 inhibitor and standard anticancer modalities such as taxol and cisplatin. In vivo xenograft system also showed sensitization activity of J2, as well as in vitro cell viability, cell death or apoptosis detection assay. For better druggability, several quinolone compounds, an (bio) isostere of chromone and one of well-known core in many marketed medicine, was designed and synthesized by replacement of oxygen with nitrogen in 4-pyron structure of J2. However, the cross linking activity of HSP27 disappeared by quinolone compounds and the sensitizing effects on the anticancer drugs disappeared as well, suggesting oxygene moiety of 4-pyron structure of J2 may be a pharmacophore for induction of cross linking of HSP27 and sensitization to cancer cells. In conclusion, combination of chemotherapy with small molecules that induces altered cross-linking of HSP27 may be a good strategy to overcome the resistance of anticancer drugs in HSP27-over-expressing cancer cells.

HSPB1 facilitates ERK-mediated phosphorylation and degradation of BIM to attenuate endoplasmic reticulum stress-induced apoptosis

BIM, a pro-apoptotic BH3-only protein, is a key regulator of the intrinsic (or mitochondrial) apoptosis pathway. Here, we show that BIM induction by endoplasmic reticulum (ER) stress is suppressed in rat PC12 cells overexpressing heat shock protein B1 (HSPB1 or HSP27) and that this is due to enhanced proteasomal degradation of BIM. HSPB1 and BIM form a complex that immunoprecipitates with p-ERK1/2. We found that HSPB1-mediated proteasomal degradation of BIM is dependent on MEK-ERK signaling. Other studies have shown that several missense mutations in HSPB1 cause the peripheral neuropathy, Charcot-Marie-Tooth (CMT) disease, which is associated with nerve degeneration. Here we show that cells overexpressing CMT-related HSPB1 mutants exhibited increased susceptibility to ER stress-induced cell death and high levels of BIM. These findings identify a novel function for HSPB1 as a negative regulator of BIM protein stability leading to protection against ER stress-induced apoptosis, a function that is absent in CMT-associated HSPB1 mutants.

Targeting Hsp27/eIF4E interaction with phenazine compound: a promising alternative for castration-resistant prostate cancer treatment

The actual strategy to improve current therapies in advanced prostate cancer involves targeting genes activated by androgen withdrawal, either to delay or prevent the emergence of the castration-refractory phenotype. However, these genes are often implicated in several physiological processes, and long-term inhibition of survival proteins might be accompanied with cytotoxic effects. To avoid this problem, an alternative therapeutic strategy relies on the identification and use of compounds that disrupt specific protein-protein interactions involved in androgen withdrawal. Specifically, the interaction of the chaperone protein Hsp27 with the initiation factor eIF4E leads to the protection of protein synthesis initiation process and enhances cell survival during cell stress induced by castration or chemotherapy. Thus, in this work we aimed at i) identifying the interaction site of the Hsp27/eIF4E complex and ii) interfere with the relevant protein/protein association mechanism involved in castration-resistant progression of prostate cancer. By a combination of experimental and modeling techniques, we proved that eIF4E interacts with the C-terminal part of Hsp27, preferentially when Hsp27 is phosphorylated. We also observed that the loss of this interaction increased cell chemo-and hormone-sensitivity. In order to find a potential inhibitor of Hsp27/eIF4E interaction, BRET assays in combination with molecular simulations identified the phenazine derivative 14 as the compound able to efficiently interfere with this protein/protein interaction, thereby inhibiting cell viability and increasing cell death in chemo- and castration-resistant prostate cancer models in vitro and in vivo.

Heat Shock Protein 27, a Novel Regulator of Transforming Growth Factor β Induced Resistance to Cisplatin in A549 Cell

Lung cancer is one of the major causes of cancer morbidity and mortality around the world, and the resistance to cisplatin is a critical issue to chemotherapy in lung cancer patients. Transforming growth factor β (TGF-β) signal pathway abnormality is widely observed in drug resistance during lung cancer chemotherapy. Here, we investigated the effects of heat-shock protein 27 (HSP27) in the TGF-β-induced cisplatin resistance in lung cancer cell. In this study, our results indicated that the mRNA and protein expression of HSP27 were significantly increased in human lung cancer tissues. TGF-β induced the mRNA and protein expression of HSP27 in human lung cancer cell (A549). Treatment of TGF-β-induced cisplatin resistance in A549 cell through blocking the cisplatin-induced apoptosis and cell death, which characterized as the increasing of cell viability and decreasing of PARP and caspase3 cleavage in the cisplatin-treated cell. Knockdown of SMAD3 attenuated the TGF-β-induced HSP27 expression and restored the TGF-β-induced cisplatin resistance in A549 cell. Additionally, the knockdown of HSP27 blocked TGF-β-induced cisplatin resistance via decreasing cell viability and increasing cell apoptosis in A549 cell. These data therefore suggested that HSP27 is critical to lung cancer progression and TGF-β-induced cisplatin resistance in human lung cancer cell, and may provide an effective clinical strategy in lung cancer patients with resistance to chemotherapy.

Heat-shock protein 27 (HSP27, HSPB1) is synthetic lethal to cells with oncogenic activation of MET, EGFR and BRAF

The small heat-shock protein of 27 kDa (HSP27) is highly expressed in many cancers and is associated with aggressive tumour behaviour, metastasis, poor prognosis and resistance to chemotherapy. We aimed at assessing the role of HSP27 in modulating responses to target therapies. We selected several oncogene-addicted cancer cell lines, which undergo either cell cycle blockade or cell death in response to agents that target the specific oncogene. Surprisingly, HSP27 suppression alone resulted in the apoptotic death of MET-addicted EBC-1 lung cancer cells, epidermal growth factor receptor (EGFR)-addicted colorectal carcinoma (CRC) DiFi cells and BRAF-addicted CRC COLO205 and OXCO-1 and melanoma COLO741 cells, all of which also undergo death when treated with the specific targeted agent. In other cell lines, such as MET-addicted gastric carcinoma MKN45 and EGFR-addicted CRC SW48 lines, where oncogene inhibition only blocked proliferation, HSP27 knockdown made targeted agents switch from cytostatic to cytotoxic activity. Mechanistically, the more the cells were susceptible to HSP27 suppression, the more they were primed for death, as demonstrated by increased levels of mitochondrial outer membrane permeabilization. Priming for death was accompanied by the increase in pro-apoptotic proteins of the BCL2 family and of active caspase-3 and lamin B. Together, these data suggest that oncogene-addicted cells require HSP27 for survival and that HSP27 might interfere with the effectiveness of targeted agents.

Copalic acid analogs down-regulate androgen receptor and inhibit small chaperone protein

Copalic acid, one of the diterpenoid acids in copaiba oil, inhibited the chaperone function of α-crystallin and heat shock protein 27kD (HSP27). It also showed potent activity in decreasing an HSP27 client protein, androgen receptor (AR), which makes it useful in prostate cancer treatment or prevention. To develop potent drug candidates to decrease the AR level in prostate cancer cells, more copalic acid analogs were synthesized. Using the level of AR as the readout, 15 of the copalic acid analogs were screened and two compounds were much more potent than copalic acid. The compounds also dose-dependently inhibited AR positive prostate cancer cell growth. Furthermore, they inhibited the chaperone activity of α-crystallin as well.

MicroRNA-455-3p functions as a tumor suppressor by targeting eIF4E in prostate cancer

MicroRNAs (miRNAs) are strongly implicated in various cancers, including prostate cancer. Recently, microRNA-455-3p (miR-455-3p) has been shown to be aberrantly expressed in many tumor tissues, but its functions in tumorigenesis remain unknown. In this study, we investigated the role of miR-455-3p in prostate cancer. We found that miR-455-3p is markedly downregulated in prostate cancer cell lines and clinical tumor specimens. Gain-of-function and loss-of-function studies showed that miR-455-3p promotes prostate cancer cell growth both in vitro and in vivo. Bioinformatics analysis and Luciferase reporter assays demonstrated that miR-455-3p directly targets and suppresses eIF4E, the rate-limiting factor for cap-dependent translation, which plays important roles in the initiation and progression of prostate cancers. Further studies demonstrated that miR-455-3p inhibits cap-dependent translation and the proliferation of prostate cancer cells through targeting eIF4E. Taken together, our findings suggest that miR-455-3p functions as a tumor suppressor by directly targeting eIF4E in prostate carcinogenesis and may be used as a potential target for therapeutic intervention in prostate cancer.

mTORC1 signalling and eIF4E/4E-BP1 translation initiation factor stoichiometry influence recombinant protein productivity from GS-CHOK1 cells

Many protein-based biotherapeutics are produced in cultured Chinese hamster ovary (CHO) cell lines. Recent reports have demonstrated that translation of recombinant mRNAs and global control of the translation machinery via mammalian target of rapamycin (mTOR) signalling are important determinants of the amount and quality of recombinant protein such cells can produce. mTOR complex 1 (mTORC1) is a master regulator of cell growth/division, ribosome biogenesis and protein synthesis, but the relationship between mTORC1 signalling, cell growth and proliferation and recombinant protein yields from mammalian cells, and whether this master regulating signalling pathway can be manipulated to enhance cell biomass and recombinant protein production (rPP) are not well explored. We have investigated mTORC1 signalling and activity throughout batch culture of a panel of sister recombinant glutamine synthetase-CHO cell lines expressing different amounts of a model monoclonal IgG4, to evaluate the links between mTORC1 signalling and cell proliferation, autophagy, recombinant protein expression, global protein synthesis and mRNA translation initiation. We find that the expression of the mTORC1 substrate 4E-binding protein 1 (4E-BP1) fluctuates throughout the course of cell culture and, as expected, that the 4E-BP1 phosphorylation profiles change across the culture. Importantly, we find that the eIF4E/4E-BP1 stoichiometry positively correlates with cell productivity. Furthermore, eIF4E amounts appear to be co-regulated with 4E-BP1 amounts. This may reflect a sensing of either change at the mRNA level as opposed to the protein level or the fact that the phosphorylation status, as well as the amount of 4E-BP1 present, is important in the co-regulation of eIF4E and 4E-BP1.

Heat shock protein 27 is a potential indicator for response to YangZheng XiaoJi and chemotherapy agents in cancer cells

Heat shock protein 27 (HSP27) is a member of the heat shock protein family which has been linked to tumour progression and, most interestingly, to chemotherapy resistance in cancer patients. The present study examined the potential interplay between HSP27 and YangZheng XiaoJi, a traditional Chinese medicine used in cancer treatment. A range of cell lines from different tumour types including pancreatic, lung, gastric, colorectal, breast, prostate and ovarian cancer (both wild-type and resistant) were used. Levels and activation of HSP27 and its potential associated signalling pathways were evaluated by protein array and western blotting. Knockdown of HSP27 in cancer cells was achieved using siRNA. Localisation and co-localisation of HSP27 and other proteins were carried out by immunofluorescence. Cell growth and migration were evaluated in their response to a range of chemotherapeutic agents. The present study first identified, by way of protein array, that YangZheng XiaoJi was able to inhibit the phosphorylation of HSP27 protein in cancer cells. We further demonstrated that HSP27, which is co-localised with caspase-9, can be blocked from localising in focal adhesions and co-localising with caspase-9 by YangZheng XiaoJi. The study also demonstrated that YangZheng XiaoJi was able to sensitise cancer cells including those cells that were resistant to chemotherapy, to chemotherapeutic agents. Finally, knocking down HSP27 markedly reduced the migration of cancer cells and increased the sensitivity of cancer cells to the inhibitory effect on cellular migration by YangZheng XiaoJi. YangZheng XiaoJi can act as an agent in first sensitising cancer cells to chemotherapy and secondly to overcome, to some degree, chemoresistance when used in an appropriate fashion in patients who have active HSP27.

Pre-clinical Orthotopic Murine Model of Human Prostate Cancer

To study the multifaceted biology of prostate cancer, pre-clinical in vivo models offer a range of options to uncover critical biological information about this disease. The human orthotopic prostate cancer xenograft mouse model provides a useful alternative approach for understanding the specific interactions between genetically and molecularly altered tumor cells, their organ microenvironment, and for evaluation of efficacy of therapeutic regimens. This is a well characterized model designed to study the molecular events of primary tumor development and it recapitulates the early events in the metastatic cascade prior to embolism and entry of tumor cells into the circulation. Thus it allows elucidation of molecular mechanisms underlying the initial phase of metastatic disease. In addition, this model can annotate drug targets of clinical relevance and is a valuable tool to study prostate cancer progression. In this manuscript we describe a detailed procedure to establish a human orthotopic prostate cancer xenograft mouse model.

Phase I and II therapies targeting the androgen receptor for the treatment of castration resistant prostate cancer

INTRODUCTION

Prostate cancer is the most common cancer in elderly males. Regardless of the initial hormonal treatment in metastatic disease, a significant proportion of patients develop castration resistant prostate cancer (CRPC). A better understanding of the molecular mechanisms behind castration resistance has led to the approval of oral medications such as abiraterone acetate and enzalutamide. Relevant research is accelerated with numerous agents being tested for the management of CRPC.

AREAS COVERED

The authors present Phase I and II studies targeting the androgen receptor for the treatment of CRPC. Three groups of agents are identified according to the mechanism of action. These include the CYP-17 modulators (Orteronel, Galeterone, VT-464 and CFG-920), novel antiandrogens (Apatorsen, ARN-509, ODM-201, EZN-4176, AZD-3514) and bipolar androgen therapy.

EXPERT OPINION

Further understanding of the mechanisms leading to castration resistance in prostate cancer can reveal potential targets for the development of novel anti-cancer agents. Except for the development of novel antiandrogens and CYP-17 modulators, bipolar androgen therapy is an interesting therapeutic approach. The combinations of the novel agents tested in Phase I and II studies with established agents is another field of interest. The real challenge is to distinguish a novel anti-cancer agent with acceptable tolerability and the best outcome.

Cell type-specific abundance of 4EBP1 primes prostate cancer sensitivity or resistance to PI3K pathway inhibitors

Pharmacological inhibitors against the PI3K-AKT-mTOR (phosphatidylinositol 3-kinase-AKT-mammalian target of rapamycin) pathway, a frequently deregulated signaling pathway in cancer, are clinically promising, but the development of drug resistance is a major limitation. We found that 4EBP1, the central inhibitor of cap-dependent translation, was a critical regulator of both prostate cancer initiation and maintenance downstream of mTOR signaling in a genetic mouse model. 4EBP1 abundance was distinctly different between the epithelial cell types of the normal prostate. Of tumor-prone prostate epithelial cell types, luminal epithelial cells exhibited the highest transcript and protein abundance of 4EBP1 and the lowest protein synthesis rates, which mediated resistance to both pharmacologic and genetic inhibition of the PI3K-AKT-mTOR signaling pathway. Decreasing total 4EBP1 abundance reversed resistance in drug-insensitive cells. Increased 4EBP1 abundance was a common feature in prostate cancer patients who had been treated with the PI3K pathway inhibitor BKM120; thus, 4EBP1 may be associated with drug resistance in human tumors. Our findings reveal a molecular program controlling cell type-specific 4EBP1 abundance coupled to the regulation of global protein synthesis rates that renders each epithelial cell type of the prostate uniquely sensitive or resistant to inhibitors of the PI3K-AKT-mTOR signaling pathway.

The Effects of HSP27 on Gemcitabine-Resistant Pancreatic Cancer Cell Line Through Snail

OBJECTIVES

To evaluate the regulation mechanism of heat shock protein 27 (HSP27) on gemcitabine (GEM) resistance of pancreatic cancer cell.

METHODS

The expression vectors pEGFP-C1-HSP27 and the vectors of MicroRNA targeting Snail were introduced into GEM-sensitive pancreatic cancer SW1990 cells, and the vectors of small hairpin RNA targeting HSP27 were transfected into SW1990 and GEM-resistant SW1990/GEM cells. The expressions of HSP27, p-HSP27 (Ser82), Snail, ERCC1, and E-cadherin were evaluated by Western blotting. The sensitivity of transfected cells to GEM was detected by CCK-8 assay and Annexin V-FITC apoptosis assay.

RESULTS

As compared to SW1990, SW1990/GEM showed significantly increased expressions of HSP27, p-HSP27, Snail and ERCC1 with decreased expression of E-cadherin. By increasing HSP27 expression, we found increase of Snail and ERCC1 with reduction of E-cadherin expressions, while reduction of HSP27 expression caused reduction of Snail and ERCC1 but increase of E-cadherin expressions. Downregulation of Snail resulted in the reduction of ERCC1 expression and increase of E-cadherin. Furthermore, downregulation of HSP27 or snail caused increased GEM sensitivity of pancreatic cancer cells, and upregulation of HSP27 showed the opposite results.

CONCLUSIONS

There is an inverse correlation between HSP27 expression and GEM sensitivity of SW1990 cells, which might be realized by regulating E-cadherin and ERCC1 expressions through Snail.

C-terminal heat shock protein 90 modulators produce desirable oncogenic properties

The cellular protection mechanism, the heat shock response, is only activated by classical heat shock 90 inhibitors (Hsp90) that "target" the N-terminus of the protein, but not by those that modulate the C-terminus. Significant differences in cytotoxicity (nanomolar) for classical inhibitors versus their ability to modulate Hsp90 (low micromolar) are discussed. In contrast, molecules that modulate Hsp90's C-terminus show similar IC50 values for cytotoxicity and Hsp90 inhibition. A comparison between the two types of Hsp90 inhibitors suggests that classical inhibitors may be modulating an alternative biological target that stresses the cell rather directly inhibiting Hsp90, whereas C-terminal modulators are most likely acting by directly inhibiting Hsp90.

The hallmarks of castration-resistant prostate cancers

Prostate cancer has become a real public health issue in industrialized countries, mainly due to patients' relapse by castration-refractory disease after androgen ablation. Castration-resistant prostate cancer is an incurable and highly aggressive terminal stage of prostate cancer, seriously jeopardizing the patient's quality of life and lifespan. The management of castration-resistant prostate cancer is complex and has opened new fields of research during the last decade leading to an improved understanding of the biology of the disease and the development of new therapies. Most advanced tumors resistant to therapy still maintain the androgen receptor-pathway, which plays a central role for survival and growth of most castration-resistant prostate cancers. Many mechanisms induce the emergence of the castration resistant phenotype through this pathway. However some non-related AR pathways like neuroendocrine cells or overexpression of anti-apoptotic proteins like Hsp27 are described to be involved in CRPC progression. More recently, loss of expression of tumor suppressor gene, post-transcriptional modification using miRNA, epigenetic alterations, alternatif splicing and gene fusion became also hallmarks of castration-resistant prostate cancer. This review presents an up-to-date overview of the androgen receptor-related mechanisms as well as the latest evidence of the non-AR-related mechanisms underlying castration-resistant prostate cancer progression.

Medical implications of understanding the functions of human small heat shock proteins

Small heat shock proteins (sHsps) are ubiquitous molecular chaperones that are implicated in a variety of diseases. Upon stress, they stabilize unfolding proteins and prevent them from aggregating. However, under physiological conditions without severe stress, some sHsps interact with other proteins. In a perspective view, their ability to bind specific client proteins might allow them to fine-tune the availability of the client for other, client-dependent cellular processes. Additionally, some sHsps seem to interact with specific co-chaperones. These co-chaperones are usually part of large protein machineries that are functionally modulated upon sHsps interaction. Finally, secreted human sHsps seem to interact with receptor proteins, potentially as signal molecules transmitting the stress status from one cell to another. This review focuses on the mechanistic description of these different binding modes for human sHsps and how this might help to understand and modulate the function of sHsps in the context of disease.

Hsp27 Inhibition with OGX-427 Sensitizes Non-Small Cell Lung Cancer Cells to Erlotinib and Chemotherapy

Non-small cell lung cancer (NSCLC) is the most frequent cause of death from cancer worldwide. Despite the availability of active chemotherapy regimens and EGFR tyrosine kinase inhibitors, all advanced patients develop recurrent disease after first-line therapy. Although Hsp27 is a stress-induced chaperone that promotes acquired resistance in several cancers, its relationship to treatment resistance in NSCLC has not been defined. Understanding adaptive responses of acquired resistance will help guide new strategies to control NSCLC. Hsp27 levels were evaluated in an HCC827 erlotinib-resistant-derived cell line (HCC-827Resistant), and sensitivity to erlotinib was examined in Hsp27-overexpressing A549 cells. The role of Hsp27 in both erlotinib and cytotoxic treatment resistance was evaluated in HCC-827 and A549 NSCLC cells using the Hsp27 antisense drug OGX-427. The effect of OGX-427 in combination with erlotinib was also assessed in mice bearing A549 xenografts. Hsp27 is induced by erlotinib and protects NSCLC cells from treatment-induced apoptosis, whereas OGX-427 sensitizes NSCLC cells to erlotinib. Interestingly, increased resistance to erlotinib was observed when Hsp27 was increased either in HCC827 erlotinib-resistant or overexpressing A549 cells. Combining OGX-427 with erlotinib significantly enhanced antitumor effects in vitro and delayed A549 xenograft growth in vivo. OGX-427 also significantly enhanced the activity of cytotoxic drugs used for NSCLC. These data indicate that treatment-induced Hsp27 contributes to the development of resistance, and provides preclinical proof-of-principle that inhibition of stress adaptive pathways mediated by Hsp27 enhances the activity of erlotinib and chemotherapeutics.

The Eukaryotic Translation Initiation Factor 4E (eIF4E) as a Therapeutic Target for Cancer

Cancer cells depend on cap-dependent translation more than normal tissue. This explains the emergence of proteins involved in the cap-dependent translation as targets for potential anticancer drugs. Cap-dependent translation starts when eIF4E binds to mRNA cap domain. This review will present eIF4E's structure and functions. It will also expose the use of eIF4E as a therapeutic target in cancer.