Spermine is a natural suppressor of AR signaling in castration-resistant prostate cancer

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PRPF6 promotes androgen receptor/androgen receptor-variant 7 actions in castration-resistant prostate cancer cells

Androgen receptor (AR) and its variants play vital roles in development and progression of prostate cancer. To clarify the mechanisms involved in the enhancement of their actions would be crucial for understanding the process in prostate cancer and castration-resistant prostate cancer transformation. Here, we provided the evidence to show that pre-mRNA processing factor 6 (PRPF6) acts as a key regulator for action of both AR full length (AR-FL) and AR variant 7 (AR-V7), thereby participating in the enhancement of AR-FL and AR-V7-induced transactivation in prostate cancer. In addition, PRPF6 is recruited to cis-regulatory elements in AR target genes and associates with JMJD1A to enhance AR-induced transactivation. PRPF6 also promotes expression of AR-FL and AR-V7. Moreover, PRPF6 depletion reduces tumor growth in prostate cancer-derived cell lines and results in significant suppression of xenograft tumors even under castration condition in mouse model. Furthermore, PRPF6 is obviously highly expressed in human prostate cancer samples. Collectively, our results suggest PRPF6 is involved in enhancement of oncogenic AR signaling, which support a previously unknown role of PRPF6 during progression of prostate cancer and castration-resistant prostate cancers.     

HMGB1 release promotes paclitaxel resistance in castration-resistant prostate cancer cells via activating c-Myc expression

Paclitaxel (PTX) is one of standard chemotherapy drug for patients with metastatic castration-resistant prostate cancer (mCRPC). However, PTX resistance leads to treatment failures, for which the underlying molecular mechanisms remain exclusive. In this study, we reported that PTX-induced constant HMGB1 expression and release confers to PTX resistance in mCRPC cells via activating and sustaining c-Myc signaling. PTX upregulated HMGB1 expression and triggered its release in human mCRPC cells. Silencing HMGB1 by RNAi and blocking HMGB1 release by glycyrrhizin or HMGB1 neutralizing antibody sensitized the response of PTX-resistant mCRPC cells to PTX. Release HMGB1 activated c-Myc expression. Inhibiting c-Myc expression by RNAi or c-MyC inhibitor significantly enhance the sensitivity of PTX-resistant CRPC cells to PTX. Therefore, HMGB1/c-Myc axis is critical in the development of PTX resistance, and targeting HMGB1/c-Myc axis would counteract PTX resistance in mCRPC cells.     

Targeting NPRL2 to enhance the efficacy of Olaparib in castration-resistant prostate cancer

Castration-resistant prostate cancer (CRPC) lacks effective treatment, and studies have shown that PARPi inhibitors, such as Olaparib, are somewhat effective; however, the efficacy of Olaparib in CRPC still needs to be further improved. Nitrogen permease regulator-like 2 (NPRL2) is reported to be a tumor suppressor candidate gene and is closely related to the DNA repair pathway, which can affect the sensitivity of many chemotherapeutic drugs. However, there is no research on whether NPRL2 is associated with sensitivity to Olaparib. Hence, in the present study, we examined the NPRL2 expression levels in several PCa cell lines (LNCaP, PC3, and enzalutamide-resistant LNCaP, named LNPER) by Western blot. In addition, we investigated the role of NPRL2 expression and silencing in cell proliferation and in the regulation of ataxia telangiectasia mutated (ATM), which can mediate DNA repair and sensitivity to Olaparib. Furthermore, we performed in vitro and in vivo experiments to determine the mechanism of action of NPRL2 in adjusting Olaparib sensitivity. Our findings demonstrated that the NPRL2 expression level was upregulated in PCa cells, especially CRPC cells. NPRL2 overexpression promoted growth and resistance to Olaparib, and NPRL2 silencing inhibited proliferation, enhanced sensitivity to Olaparib, and increased CRRL2 expression in PCa cells. In addition, the Olaparib-induced growth delay in NPRL2-silenced PC3 tumors in mice correlated with ATM signaling downregulation, an apoptosis increase and migration/invasion suppression. Our results indicate that NPRL2 silencing enhances sensitivity to Olaparib treatment in CRPC and that NPRL2 may serve as a potential therapeutic target and predict resistance to Olaparib in CRPC.     

Phospho-MED1-enhanced UBE2C locus looping drives castration-resistant prostate cancer growth

The UBE2C oncogene is overexpressed in many types of solid tumours including the lethal castration-resistant prostate cancer (CRPC). The underlying mechanisms causing UBE2C gene overexpression in CRPC are not fully understood. Here, we show that CRPC-specific enhancers drive UBE2C overexpression in both AR-negative and -positive CRPC cells. We further show that co-activator MED1 recruitment to the UBE2C enhancers is required for long-range UBE2C enhancer/promoter interactions. Importantly, we find that the molecular mechanism underlying MED1-mediated chromatin looping involves PI3K/AKT phosphorylated MED1-mediated recruitment of FoxA1, RNA polymerase II and TATA binding protein and their subsequent interactions at the UBE2C locus. MED1 phosphorylation leads to UBE2C locus looping, UBE2C gene expression and cell growth. Our results not only define a causal role of a post-translational modification (phosphorylation) of a co-activator (MED1) in forming or sustaining an active chromatin structure, but also suggest that development of specific therapies for CRPC should take account of targeting phosphorylated MED1.     

Androgens as therapy for androgen receptor-positive castration-resistant prostate cancer

Prostate cancer is the most frequently diagnosed non-cutaneous tumor of men in Western countries. While surgery is often successful for organ-confined prostate cancer, androgen ablation therapy is the primary treatment for metastatic prostate cancer. However, this therapy is associated with several undesired side-effects, including increased risk of cardiovascular diseases. Shortening the period of androgen ablation therapy may benefit prostate cancer patients. Intermittent Androgen Deprivation therapy improves quality of life, reduces toxicity and medical costs, and delays disease progression in some patients. Cell culture and xenograft studies using androgen receptor (AR)-positive castration-resistant human prostate cancers cells (LNCaP, ARCaP, and PC-3 cells over-expressing AR) suggest that androgens may suppress the growth of AR-rich prostate cancer cells. Androgens cause growth inhibition and G1 cell cycle arrest in these cells by regulating c-Myc, Skp2, and p27^Kip via AR. Higher dosages of testosterone cause greater growth inhibition of relapsed tumors. Manipulating androgen/AR signaling may therefore be a potential therapy for AR-positive advanced prostate cancer.     

p66Shc regulates migration of castration-resistant prostate cancer cells

Metastatic castration-resistant (CR) prostate cancer (PCa) is a lethal disease for which no effective treatment is currently available. p66Shc is an oxidase previously shown to promote androgen-independent cell growth through generation of reactive oxygen species (ROS) and is elevated in clinical PCa and multiple CR PCa cell lines. We hypothesize p66Shc also increases the migratory activity of PCa cells through ROS and investigate the associated mechanism. Using the transwell assay, our study reveals that the level of p66Shc protein correlates with cell migratory ability across several PCa cell lines. Furthermore, we show hydrogen peroxide treatment induces migration of PCa cells that express low levels of p66Shc in a dose-dependent manner, while antioxidants inhibit migration. Conversely, PCa cells that express high levels of endogenous p66Shc or by cDNA transfection possess increased cell migration which is mitigated upon p66Shc shRNA transfection or expression of oxidase-deficient dominant-negative p66Shc W134F mutant. Protein microarray and immunoblot analyses reveal multiple proteins, including ErbB-2, AKT, mTOR, ERK, FOXM1, PYK2 and Rac1, are activated in p66Shc-elevated cells. Their involvement in PCa migration was examined using respective small-molecule inhibitors. The role of Rac1 was further validated using cDNA transfection and, significantly, p66Shc is found to promote lamellipodia formation through Rac1 activation. In summary, the results of our current studies clearly indicate p66Shc also regulates PCa cell migration through ROS-mediated activation of migration-associated proteins, notably Rac1.     

Androgen receptor variants and prostate cancer in humanized AR mice

Androgen, acting via the androgen receptor (AR), is central to male development, differentiation and hormone-dependent diseases such as prostate cancer. AR is actively involved in the initiation of prostate cancer, the transition to androgen independence, and many mechanisms of resistance to therapy. To examine genetic variation of AR in cancer, we created mice by germ-line gene targeting in which human AR sequence replaces that of the mouse. Since shorter length of a polymorphic N-terminal glutamine (Q) tract has been linked to prostate cancer risk, we introduced alleles with 12, 21 or 48 Qs to test this association. The three “humanized” AR mouse strains (h/mAR) are normal physiologically, as well as by cellular and molecular criteria, although slight differences are detected in AR target gene expression, correlating inversely with Q tract length. However, distinct allele-dependent differences in tumorigenesis are evident when these mice are crossed to a transgenic prostate cancer model. Remarkably, Q tract variation also differentially impacts disease progression following androgen depletion. This finding emphasizes the importance of AR function in androgen-independent as well as androgen-dependent disease. These mice provide a novel genetic paradigm in which to dissect opposing functions of AR in tumor suppression versus oncogenesis.     

Inhibition of Plk1 represses androgen signaling pathway in castration-resistant prostate cancer

Prostate cancer (PCa) is the second leading cause of cancer-related death in males in the United States. Majority of prostate cancers are originally androgen-dependent and sensitive to androgen-deprivation therapy (ADT), however, most of them eventually relapse and progress into incurable castration-resistant prostate cancer (CRPC). Of note, the activity of androgen receptor (AR) is still required in CRPC stage. The mitotic kinase polo-like kinase 1 (Plk1) is significantly elevated in PCa and its expression correlates with tumor grade. In this study, we assess the effects of Plk1 on AR signaling in both androgen-dependent and androgen-independent PCa cells. We demonstrate that the expression level of Plk1 correlated with tumorigenicity and that inhibition of Plk1 caused reduction of AR expression and AR activity. Furthermore, Plk1 inhibitor BI2536 down-regulated SREBP-dependent expression of enzymes involved in androgen biosynthesis. Of interest, Plk1 level was also reduced when AR activity was inhibited by the antagonist MDV3100. Finally, we show that BI2536 treatment significantly inhibited tumor growth in LNCaP CRPC xenografts. Overall, our data support the concept that Plk1 inhibitor such as BI2536 prevents AR signaling pathway and might have therapeutic potential for CRPC patients.     

Mxi2 promotes stimulus-independent ERK nuclear translocation

Spatial regulation of ERK1/2 MAP kinases is an essential yet largely unveiled mechanism for ensuring the fidelity and specificity of their signals. Mxi2 is a p38alpha isoform with the ability to bind ERK1/2. Herein we show that Mxi2 has profound effects on ERK1/2 nucleocytoplasmic distribution, promoting their accumulation in the nucleus. Downregulation of endogenous Mxi2 by RNAi causes a marked reduction of ERK1/2 in the nucleus, accompanied by a pronounced decline in cellular proliferation. We demonstrate that Mxi2 functions in nuclear shuttling of ERK1/2 by enhancing the nuclear accumulation of both phosphorylated and unphosphorylated forms in the absence of stimulation. This process requires the direct interaction of both proteins and a high-affinity binding of Mxi2 to ERK-binding sites in nucleoporins, In this respect, Mxi2 acts antagonistically to PEA15, displacing it from ERK1/2 complexes. These results point to Mxi2 as a key spatial regulator for ERK1/2 and disclose an unprecedented stimulus-independent mechanism for ERK nuclear import.     

Ack1-mediated androgen receptor phosphorylation modulates radiation resistance in castration-resistant prostate cancer

Androgen deprivation therapy has been the standard of care in prostate cancer due to its effectiveness in initial stages. However, the disease recurs, and this recurrent cancer is referred to as castration-resistant prostate cancer (CRPC). Radiotherapy is the treatment of choice; however, in addition to androgen independence, CRPC is often resistant to radiotherapy, making radioresistant CRPC an incurable disease. The molecular mechanisms by which CRPC cells acquire radioresistance are unclear. Androgen receptor (AR)-tyrosine 267 phosphorylation by Ack1 tyrosine kinase (also known as TNK2) has emerged as an important mechanism of CRPC growth. Here, we demonstrate that pTyr(267)-AR is recruited to the ATM (ataxia telangiectasia mutated) enhancer in an Ack1-dependent manner to up-regulate ATM expression. Mice engineered to express activated Ack1 exhibited a significant increase in pTyr(267)-AR and ATM levels. Furthermore, primary human CRPCs with up-regulated activated Ack1 and pTyr(267)-AR also exhibited significant increase in ATM expression. The Ack1 inhibitor AIM-100 not only inhibited Ack1 activity but also was able to suppress AR Tyr(267) phosphorylation and its recruitment to the ATM enhancer. Notably, AIM-100 suppressed Ack1 mediated ATM expression and mitigated the growth of radioresistant CRPC tumors. Thus, our study uncovers a previously unknown mechanism of radioresistance in CRPC, which can be therapeutically reversed by a new synergistic approach that includes radiotherapy along with the suppression of Ack1/AR/ATM signaling by the Ack1 inhibitor, AIM-100.     

TACC2 is an androgen-responsive cell cycle regulator promoting androgen-mediated and castration-resistant growth of prostate cancer

Despite the existence of effective antiandrogen therapy for prostate cancer, the disease often progresses to castration-resistant states. Elucidation of the molecular mechanisms underlying the resistance for androgen deprivation in terms of the androgen receptor (AR)-regulated pathways is a requisite to manage castration-resistant prostate cancer (CRPC). Using a ChIP-cloning strategy, we identified functional AR binding sites (ARBS) in the genome of prostate cancer cells. We discovered that a centrosome- and microtubule-interacting gene, transforming acidic coiled-coil protein 2 (TACC2), is a novel androgen-regulated gene. We identified a functional AR-binding site (ARBS) including two canonical androgen response elements in the vicinity of TACC2 gene, in which activated hallmarks of histone modification were observed. Androgen-dependent TACC2 induction is regulated by AR, as confirmed by AR knockdown or its pharmacological inhibitor bicalutamide. Using long-term androgen-deprived cells as cellular models of CRPC, we demonstrated that TACC2 is highly expressed and contributes to hormone-refractory proliferation, as small interfering RNA-mediated knockdown of TACC2 reduced cell growth and cell cycle progression. By contrast, in TACC2-overexpressing cells, an acceleration of the cell cycle was observed. In vivo tumor formation study of prostate cancer in castrated immunocompromised mice revealed that TACC2 is a tumor-promoting factor. Notably, the clinical significance of TACC2 was demonstrated by a correlation between high TACC2 expression and poor survival rates. Taken together with the critical roles of TACC2 in the cell cycle and the biology of prostate cancer, we infer that the molecule is a potential therapeutic target in CRPC as well as hormone-sensitive prostate cancer.     

Multiplexed quantum dot labeling of activated c-Met signaling in castration-resistant human prostate cancer

The potential application of multiplexed quantum dot labeling (MQDL) for cancer detection and prognosis and monitoring therapeutic responses has attracted the interests of bioengineers, pathologists and cancer biologists. Many published studies claim that MQDL is effective for cancer biomarker detection and useful in cancer diagnosis and prognosis, these studies have not been standardized against quantitative biochemical and molecular determinations. In the present study, we used a molecularly characterized human prostate cancer cell model exhibiting activated c-Met signaling with epithelial to mesenchymal transition (EMT) and lethal metastatic progression to bone and soft tissues as the gold standard, and compared the c-Met cell signaling network in this model, in clinical human prostate cancer tissue specimens and in a castration-resistant human prostate cancer xenograft model. We observed c-Met signaling network activation, manifested by increased phosphorylated c-Met in all three. The downstream survival signaling network was mediated by NF-κB and Mcl-1 and EMT was driven by receptor activator of NF-κB ligand (RANKL), at the single cell level in clinical prostate cancer specimens and the xenograft model. Results were confirmed by real-time RT-PCR and western blots in a human prostate cancer cell model. MQDL is a powerful tool for assessing biomarker expression and it offers molecular insights into cancer progression at both the cell and tissue level with high degree of sensitivity.     

Calmodulin regulates the translocation of Grb7 into the nucleus

We describe in this report the presence of a nuclear localization signal (NLS) overlapping the calmodulin-binding domain (CaM-BD) of the growth factor receptor bound protein 7 (Grb7). We show that deletion of the CaM-BD of Grb7 prevents its nuclear localization, and that its Src homology 2 (SH2) domain might participate as well in the translocation process. Also, treating cells with the CaM antagonist N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) enhances the presence of Grb7 in the nucleus. We propose that CaM inhibits the translocation of Grb7 to the nucleus after binding to its CaM-BD and therefore occluding its overlapping NLS.     

PARP inhibitors and metastatic castration-resistant prostate cancer: uture directions and pitfalls

PARP inhibitors (PARPi) gained major interest among prostate cancer researchers in the last few years, thanks to the outstanding results coming from the PROfound an TRITON2 studies. Following that, PARPi gained approval also in metastatic, castration-resistant prostate cancer (mCRPC) with mutations in homologous repair (HR) – related genes. Nevertheless, some questions still remain unanswered concerning the management of drug resistance and PARPi-sensitivity in patients harboring alterations in various DNA damage response (DDR) related genes, not only BRCA1 and BRCA2.In this perspective article we focus on the key issues concerning PARPi in mCRPC, specifically those related to drug sensitivity and resistance mechanisms, exploring the possible role of combination therapeutic approaches and trying to depict potential future addresses in translational oncology research.

Perspective Article (max: 1200 words)The DNA damage repair (DDR) pathway gained major interest between cancer researchers since 2005, when emerging studies demonstrated that the simultaneous inhibition of both Poly(ADP-ribose) polymerase 1 (PARP1) and tumor suppressors Breast Related Cancer Antigens 1 and 2 (BRCA1 and BRCA2) generates excessive DNA instability and, ultimately, leads to cellular death. This process, called synthetic lethal theory, constituted the rationale for the development of drugs targeting PARP1 in BRCA1/2 deficient clones, the PARP inhibitors (PARPi) [1, 2].In normal conditions, PARP1 plays a key role as regulator of multiple cellular processes, including DDR. When a DNA damage occurs, the activation of PARP1 results in the recruitment of several DNA repair factors, including BRCA1 and BRCA2, leading to the restoration of single-strand (SSBs) and double-strand DNA breaks (DSBs) [1,2]^. Particularly, BRCA1 and BRCA2 act downstream the PARP1 cascade in one of the two major pathways for DSBs repair, largely error free: the homologous repair (HR). Another crucial mechanism, which sees the synergic contribution of PARP1, BRCA1 and BRCA 2, is the stabilization of replication fork during the S phase of the cell cycle [2]. As a consequence of that, heterozygous germline mutations in DDR genes, especially BRCA1 and BRCA2, dramatically increase the risk of developing multiple neoplasms (e.g. breast, ovarian, prostate and pancreatic cancers )². In addition, somatic and germline mutations in one of these genes confer a strong sensitivity to DNA-damaging agents (e.g. platinum salts): these fundamental observations led researchers to successfully study and test pharmacological inhibition of the DDR pathway, using PARPi [2].Of note, it has been calculated that approximately 12% of metastatic, castration-resistant prostate cancer (mCRPC) patients harbor germline DDR mutations, while 20–25% harbor somatic DDR mutations. Overall, it is estimated that in almost 22.7% of mCRPC patients could be identified mutations in DDR-related genes, making them a considerable number of people who could take an advantage from PARPi administration [3].In 2014, the U.S. Food and Drug Administration (FDA) granted approval to Olaparib as the first PARPi viable for women suffering from BRCA 1–2 mutated metastatic ovarian cancer both for cases previously treated with three or more lines of chemotherapy, and also as maintenance therapy following platinum-based chemotherapy [2]. Since that, following the consistent results described by subsequent clinical trials, Olaparib and other PARPi (e.g. Rucaparib, Niraparib) gained approval for different clinical settings in ovarian cancer and for BRCA-mutated breast, pancreatic and prostate cancer [2].In 2020, thanks to the outstanding results of the PROFound trial, the FDA approved the administration of Olaparib in patients with metastatic castration-resistant prostate cancer (mCRPC) progressing after therapy with enzalutamide or abiraterone and harboring mutations in HR-related genes [4]. Later the same year, the European Medicines Agency (EMA) recommended Olaparib in the same setting, with a slight but substantial difference: the main requirement was the identification of a BRCA 1 and BRCA 2 mutation (somatic or germline) in prostate cancer patients who have progressed to a prior therapy that included a new hormonal agent [5].Similarly, Rucaparib received the FDA accelerated approval after the publication of the TRITON2 study, that showed consistent overall response rate (ORR) and Prostate Specific Antigen (PSA) response rate values in patients with BRCA 1 and BRCA2 alterations [6].Nevertheless, it is well known that DDR mechanisms, including homologous repair (HR), are characterized by the interplay of a huge number of enzymes, co-factors, and molecules, not only BRCA1 and BRCA2 [2,5]. Specifically, HR requires the intervention of co-factors as PALB2 (Partner And Localizer Of BRCA2) and RAD51 (RAD51 Recombinase) to perform an accurate repair of double strand DNA breaks. In addition, BRCA1 and BRCA2 exhibit a crucial role during the S phase of the cell cycle, as protectors of the replication fork from the degradation activity carried out by nucleases. This is why, although PARPi seem to be more effective against BRCA1 and 2 mutations, data extrapolated from clinical trials suggest a benefit also for people harboring alterations in others genes, such as PALB2, RAD51 and ATM (Ataxia-Telangectasia Mutated) [2]. The PROFound trial, considered as a milestone, enlightened this aspect and its possible implications in prostate cancer: administering Olaparib to the whole cohort of HR-deficient patients could extend the survival benefit to a significant number of people, albeit the subgroup of BRCA1 and BRCA2 mutated cohort might have generated an overestimation of this effect in that trial [7]. Further studies need to be carried out in order to perform a correct prognostic and predictive gene-signature based stratification of patients.One of major concerns related to anti-cancer drugs, particularly targeted therapies, is drug-resistance. Even PARPi, although frequently characterized by initial good responses, ultimately loose their effectiveness, leading to disease relapse [2]. The reason is that cancerous cells learn how to escape from the pharmacological attack of PARPi via several mechanisms: upregulation of drug efflux pumps; mutations of the drug target; recovery of BRCA1 and BRCA2 function; re-establishment of replication fork stability [2,8]. The deep knowledge of these mechanisms could lead to overcome drug resistance: the most appealing hypothesis to get through this barrier appears to combine PARPi with agents affecting HR from other sides, such as Vascular Endothelial Growth Factor (VEGF) inhibitors, for which some encouraging data have been published in a cohort of ovarian cancer patients [2]. An interesting observation is also that HR deficient cancers might exhibit a high tumor mutational burden, often associated with an improved sensitivity to immunotherapy. Thus, clinical trials are now investigating the combination of PARPi and immune check-point inhibitors (ICIs) in mCRPC [9].Furthermore, several trials are ongoing to evaluate the efficacy of the combination of PARPi and new hormone agents (i.e. Abiraterone acetate, Enzalutamide) for metastatic prostate cancer, both in the hormone-sensitive and castration-resistant phases.Unfortunately, most of data concerning combination therapies were extrapolated from preliminary analyses of clinical trials, with many open issues still remaining. Firstly, drug safety: as previously stated in a phase I/II clinical trial, the addition of ICIs to PARPi seems to be well tolerated with no significant increase of severe adverse effects; at the same time, the administration of PARPi plus Abiraterone in mCRPC patients was investigated in a randomized, double-blind, placebo controlled phase II clinical trial, obtaining promising results in term of safety and also efficacy [2,10]. Another major concern regards the need to identify reliable biomarkers predictive of drug response, and this must be one of the addresses of future researches [1,2]. The last issue involves health care costs of such combinations therapies, again emphasizing the importance to perform a thorough stratification of mCRPC patients. [2]. These might be some branches for future researches, to explore where and when to combine PARPi with other agents, and in which patients subgroup [1,2,9].We have now several weapons in our hands, ready to be used, the most important represented by genomic analyses techniques [2]. In addition, following that principle of synthetic lethality, we need to hit cellular DNA repairing system from many sides, employing old and new drugs. The only way to cope with this huge amount of data is to team up with different professional figures (e.g. biotechnologists, pharmacologists, biostatisticians), constructing a cooperative network system. Only by doing this we will make it up to the mountain.

CC chemokine ligand 2 (CCL2) promotes prostate cancer tumorigenesis and metastasis

CCL2 is a chemokine known to recruit monocytes and macrophages to sites of inflammation. A growing body of research suggests CCL2 is progressively overexpressed in tumor beds and may play a role in the clinical progression of solid tumors. Cancer cells derived from several solid tumor types demonstrate functional receptors for CCL2, suggesting this chemokine may achieve tumorigenicity through direct effects on malignant cells; however, a variety of normal host cells that co-exist with cancer in the tumor microenvironment also respond to CCL2. These cells include macrophages, osteoclasts, endothelial cells, T-lymphocytes, and myeloid-derived immune suppressor cells (MDSCs). CCL2 mediated interactions between normal and malignant cells in the tumor microenvironment and plays a multi-faceted role in tumor progression.     

Interaction between AR signalling and CRKL bypasses casodex inhibition in prostate cancer

The underlying mechanism of failed androgen ablation therapy is unknown. It is recognised that under therapeutic conditions the androgen receptor (AR) remains functionally active independent of hormone stimulation and may function through an alternative pathway. We report a novel cooperative interaction between CRKL (an intracellular signalling adaptor protein) and the AR. We demonstrate by biochemical and genetic approaches that CRKL is associated with the AR complex and is localised in the nucleus of prostate cancer cells and patient tissue biopsies. The interaction between CRKL and the AR is functionally relevant as demonstrated by its presence on the enhancer region of an androgen regulated gene (human Kallikrein-2), its upregulation of PSA, and reduction in AR transactivation following its disruption by siRNA knockdown. In the presence of the AR inhibitor casodex, the expression of CRKL co-stimulated by growth factors is able to rescue AR activity independent of hormone. Our data provides insight on how a non-nuclear factor such as CRKL may interact with the AR complex to bypass hormone dependency by using an alternative growth factor signalling pathway in advanced prostate cancer.