Dynamic process of prostate cancer metastasis to bone

Clival Metastases: Single-Center Retrospective Case Series and Literature Review

Background/Objectives: Clivus metastases from distant neoplasms are uncommon occurrences both in clinical practice and the neurosurgical literature. Surgical management is debated, particularly about the role of surgery and the preferable approach. The aim of this study was to report our surgical experience and review the concerning literature. Methods: Our institutional registry was retrospectively reviewed, and patients who underwent surgical treatment for clival metastasis from 1998 to 2023 were included. A PRISMA systematic review of the literature was performed. Results: Four patients were enrolled, and all of them underwent an endoscopic endonasal approach (EEA). Three presented with cranial nerve (CN) VI palsy. The aim of surgery was biopsy in all cases. No complications were reported. Mean overall survival (OS) was 6 ± 1 months. The systematic review retrieved 27 papers reporting 39 patients who underwent the surgical treatment of clivus metastases. Most of them (79.5%) presented with CN palsies, and EEA was the preferred approach in 92.3% of the cases, to perform a biopsy in most patients (59%). Two hemorrhagic complications (5.1%) were reported, and the mean OS was 9.4 ± 5.6 months. Conclusions: Clival metastases are uncommonly observed, in most cases, during advanced stages of oncological disease. The aim of surgery should be the confirmation of diagnosis and symptomatic relief, balancing the risk-benefit ratio in a multidisciplinary context. EEA is the approach of choice, and it should be carried out in experienced tertiary skull base centers.

GRP78 promotes bone metastasis of prostate cancer by regulating bone microenvironment through Sonic hedgehog signaling

Bone metastasis is the leading cause of tumor-related deaths in patients with prostate cancer (PCa). The interactions between PCa and the bone microenvironment form a vicious cycle. However, the complex molecular mechanism by which PCa regulates the bone microenvironment remains unclear. To determine the role of glucose-regulated protein (GRP78) in bone metastasis and growth, we established intracardiac injection and tibial injection models, and performed their histological staining. To assess the effect of GRP78 on the differentiation of osteoblasts and osteoclasts, we performed cell co-culture, enzyme-linked immunosorbent assay, alizarin red staining, and tartrate-resistant acid phosphatase staining. We found that GRP78 is upregulated in PCa tissues and that its upregulation is associated with PCa progression in patients. Functional experiments showed that GRP78 overexpression in PCa cells considerably promotes bone metastasis and induces bone microstructure changes. Silencing GRP78 substantially inhibits the migration and invasion of PCa cells in vitro and bone metastasis and tumor growth in vivo. Mechanistically, GRP78 promotes the migration and invasion of PCa cells via the Sonic hedgehog (Shh) signaling pathway. Cell co-culture showed that GRP78 promotes the differentiation of osteoblasts and osteoclasts through Shh signaling. Our findings suggest that tumor-bone matrix interactions owing to GRP78-activated paracrine Shh signaling by PCa cells regulate the differentiation of osteoblasts and osteoclasts. This process promotes bone metastasis and the proliferation of PCa cells in the bone microenvironment. Targeting the GRP78/Shh axis can serve as a therapeutic strategy to prevent bone metastasis and improve the quality of life of patients with PCa.

Three-dimensional amide proton transfer-weighted and intravoxel incoherent motion imaging for predicting bone metastasis in patients with prostate cancer: A pilot study

PURPOSE

To explore the value of 3-dimensional amide proton transfer-weighted (APTw) and intravoxel incoherent motion (IVIM) imaging in predicting bone metastasis (BM) of prostate cancer (PCa) in addition to routine diffusion-weighted imaging (DWI).

METHODS

The clinical and imaging data of 39 PCa patients who were pathologically confirmed in our hospital from March 2019 to February 2022 were retrospectively analyzed, and they were divided into BM-negative (27 patients) and BM-positive (12 patients) groups. MR examination included APTw, DWI and IVIM imaging. The IVIM data was fitted by single-exponential IVIM model (IVIM_mono) and double-exponential IVIM model (IVIM_bi), respectively. The APTw, ADC, IVIM_mono (D_mono, D*_mono, and f_mono), and IVIM_bi (D_bi, D*_bi, and f_bi) parameters were independently measured by two radiologists. The synthetic minority oversampling technique (SMOTE) was conducted to balance the minority group. Mann-Whitney U test or Student's t-test was used to compare above values between the BM-negative and BM-positive groups. The diagnostic performance was evaluated with receiver operating characteristic (ROC) analysis of each parameter and their combination. The Delong test was used for ROC curve comparison.The relationship between APTw and IVIM was explored through Spearman's rank correlation analysis.

RESULTS

The APTw and D*_mono values were higher, and the ADC, f_mono, and f_bi values were lower in the BM-positive group than in the BM-negative group (all P < 0.05). Among the individual parameters, the AUC of f_mono was the highest (AUC = 0.865), and AUC (f_mono) was significantly higher than AUC (f_bi), AUC (D*_mono), and AUC (ADC) (all P < 0.05). The AUC (IVIM_mono) was higher than the AUC (IVIM_bi) (P = 0.0068). The combination of APTw and IVIM_mono further improved diagnostic capability, and the AUC of APTw+IVIM_mono was significantly higher than those of APTw and DWI (all P < 0.05). No correlation was found between IVIM-derived parameters and APTw value.

CONCLUSION

Both 3D APTw and IVIM imaging could predict BM of PCa. IVIM showed better performance than APTw and DWI, and the single-exponential IVIM model was superior to the double-exponential IVIM model. The combination of APTw and IVIM could further improve diagnostic performance.

LncNAP1L6 activates MMP pathway by stabilizing the m6A-modified NAP1L2 to promote malignant progression in prostate cancer

Malignant progression such as bone metastasis, which is associated with pathologic fractures, pain and reduced survival frequently occurs in prostate cancer (PCa) patients at advanced stages. Accumulating evidence has supported that long non-coding RNAs (lncRNAs) participate in multiple biological processes. Nevertheless, the functions of most lncRNAs in PCa malignant progression remain largely unclear. Our current study is to elucidate the influence of lncRNA lncNAP1L6 on PCa malignant progression and uncover the possible regulatory mechanism. Firstly, RT-qPCR analysis was to detect lncNAP1L6 expression and suggested that lncNAP1L6 was markedly upregulated in PCa cells. Functional assays manifested that silencing of lncNAP1L6 hampered cell migration, invasion, and epithelial-mesenchymal transition (EMT) while overexpression of lncNAP1L6 exacerbated cell migration, invasion and EMT. In addition, mechanism assays were to determine the latent regulatory mechanism of lncNAP1L6. It turned out that METTL14/METTL3 complex mediated m6A methylation of NAP1L2 mRNA. Besides, lncNAP1L6 recruited HNRNPC to m6A-modified NAP1L2, leading to stabilization of NAP1L2 mRNA. Moreover, NAP1L6 interacted with YY1 to promote the transcription of MMP2 and MMP9 and activate MMP signaling pathway. In summary, lncNAP1L6 was identified as an oncogene in PCa, which revealed that lncNAP1L6 might be used as potential therapeutic target in PCa.

Isolipoic acid-linked gold nanoparticles bearing the thomsen friedenreich tumor-associated carbohydrate antigen: Stability and in vitro studies

We have previously prepared gold nanoparticles (AuNPs) bearing the Thomsen-Friedenreich antigen disaccharide (TF_ag), a pan-carcinoma, Tumor-Associated Carbohydrate Antigen (TACA), as tools for various assays and biological applications. Conjugation to AuNPs typically involves the use of thiols due to the affinity of sulfur for the gold surface of the nanoparticle. While a use of a single thiol-containing ligand bound to the gold surface is standard practice, several studies have shown that ligands bearing multiple thiols can enhance the strength of the conjugation in a nearly linear fashion. (R)-(+)-α-Lipoic acid (LA), a naturally occurring disulfide-containing organic acid that is used as a cofactor in many enzymatic reactions, has been used as a linker to conjugate various molecules to AuNPs through its branched di-thiol system to enhance nanoparticle stability. We sought to use a similar system to increase nanoparticle stability that was devoid of the chiral center in (R)-(+)-α-lipoic acid. Isolipoic acid, an isomer of LA, where the exocyclic pentanoic acid chain is shifted by one carbon on the dithiolane ring to produce an achiral acid, was thought to act similarly as LA without the risk of any contaminating (L)-(−) isomer. We synthesized AuNPs with ligands of both serine and threonine glycoamino acids bearing the TF_ag linked to isolipoic acid and examined their stability under various conditions. In addition, these particles were shown to bind to Galectin-3 and inhibit the interaction of Galectin-3 with a protein displaying copies of the TF_ag. These agents should prove useful in the design of potential antimetastatic therapeutics that would benefit from achiral linkers that are geometrically linear and achiral.

An Integrative Multi-Omics Analysis Based on Nomogram for Predicting Prostate Cancer Bone Metastasis Incidence

Background

The most common site of prostate cancer metastasis is bone tissue with many recent studies having conducted genomic and clinical research regarding bone metastatic prostate cancer. However, further work is needed to better define those patients that are at an elevated risk of such metastasis.

Methods

SEER and TCGA databases were searched to develop a nomogram for predicting prostate cancer bone metastasis.

Results

Herein, we leveraged the Surveillance, Epidemiology, and End Results (SEER) database to construct a predictive nomogram capable of readily and accurately predicted the odds of bone metastasis in prostate cancer patients. This nomogram was utilized to assign patients with prostate cancer included in The Cancer Genome Atlas (TCGA) to cohorts at a high or low risk of bone metastasis (HRBM and LRBM, respectively). Comparisons of these LRBM and HRBM cohorts revealed marked differences in mutational landscapes between these patient cohorts, with increased frequencies of gene fusions, somatic copy number variations (CNVs), and single nucleotide variations (SNVs), particularly in the P53 gene, being evident in the HRBM cohort. We additionally identified lncRNAs, miRNAs, and mRNAs that were differentially expressed between these two patient cohorts and used them to construct a competing endogenous RNA (ceRNA) network. Moreover, three weighted gene co-expression network analysis (WGCNA) modules were constructed from the results of these analyses, with KIF14, MYH7, and COL10A1 being identified as hub genes within these modules. We further found immune response activity levels in the HRBM cohort to be elevated relative to that in the LRBM cohort, with single sample gene enrichment analysis (ssGSEA) scores for the immune checkpoint signature being increased in HRBM patient samples relative to those from LRBM patients.

Conclusion

We successfully developed a nomogram capable of readily detecting patients with prostate cancer at an elevated risk of bone metastasis.

Spatio-temporal analysis of prostate tumors in situ suggests pre-existence of treatment-resistant clones

The molecular mechanisms underlying lethal castration-resistant prostate cancer remain poorly understood, with intratumoral heterogeneity a likely contributing factor. To examine the temporal aspects of resistance, we analyze tumor heterogeneity in needle biopsies collected before and after treatment with androgen deprivation therapy. By doing so, we are able to couple clinical responsiveness and morphological information such as Gleason score to transcriptome-wide data. Our data-driven analysis of transcriptomes identifies several distinct intratumoral cell populations, characterized by their unique gene expression profiles. Certain cell populations present before treatment exhibit gene expression profiles that match those of resistant tumor cell clusters, present after treatment. We confirm that these clusters are resistant by the localization of active androgen receptors to the nuclei in cancer cells post-treatment. Our data also demonstrates that most stromal cells adjacent to resistant clusters do not express the androgen receptor, and we identify differentially expressed genes for these cells. Altogether, this study shows the potential to increase the power in predicting resistant tumors.

A study of gene expression by RNA-seq in patients with prostate cancer and in patients with Parkinson disease: an example of inverse comorbidity

BACKGROUND

Prostate cancer (PCa) is one of the leading causes of death in Western countries. Environmental and genetic factors play a pivotal role in PCa etiology. Timely identification of the genetic causes is useful for an early diagnosis. Parkinson's disease (PD) is the most frequent neurodegenerative movement disorder; it is associated with the presence of Lewy bodies and genetic factors are involved in its pathogenesis. Several studies have indicated that the expression of target genes in patients with PD is inversely related to cancer development; this phenomenon has been named "inverse comorbidity". The present study was undertaken to evaluate whether a genetic dysregulation occurs in opposite directions in patients with PD or PCa.

METHODS AND RESULTS

In the present study, next-generation sequencing transcriptome analysis was used to assess whether a genetic dysregulation in opposite directions occurs in patients with PD or PCa. The genes SLC30A1, ADO, SRGAP2C, and TBC1D12 resulted up-regulated in patients with PD compared to healthy donors as controls and down-regulated in patients with PCa compared with the same control group.

CONCLUSIONS

These results support the hypothesis of the presence of inverse comorbidity between PD and PCa.

Automatic identification of suspicious bone metastatic lesions in bone scintigraphy using convolutional neural network

Background

We aimed to construct an artificial intelligence (AI) guided identification of suspicious bone metastatic lesions from the whole-body bone scintigraphy (WBS) images by convolutional neural networks (CNNs).

Methods

We retrospectively collected the ^99mTc-MDP WBS images with confirmed bone lesions from 3352 patients with malignancy. 14,972 bone lesions were delineated manually by physicians and annotated as benign and malignant. The lesion-based differentiating performance of the proposed network was evaluated by fivefold cross validation, and compared with the other three popular CNN architectures for medical imaging. The average sensitivity, specificity, accuracy and the area under receiver operating characteristic curve (AUC) were calculated. To delve the outcomes of this study, we conducted subgroup analyses, including lesion burden number and tumor type for the classifying ability of the CNN.

Results

In the fivefold cross validation, our proposed network reached the best average accuracy (81.23%) in identifying suspicious bone lesions compared with InceptionV3 (80.61%), VGG16 (81.13%) and DenseNet169 (76.71%). Additionally, the CNN model's lesion-based average sensitivity and specificity were 81.30% and 81.14%, respectively. Based on the lesion burden numbers of each image, the area under the receiver operating characteristic curve (AUC) was 0.847 in the few group (lesion number n ≤ 3), 0.838 in the medium group (n = 4–6), and 0.862 in the extensive group (n > 6). For the three major primary tumor types, the CNN-based lesion identifying AUC value was 0.870 for lung cancer, 0.900 for prostate cancer, and 0.899 for breast cancer.

Conclusion

The CNN model suggests potential in identifying suspicious benign and malignant bone lesions from whole-body bone scintigraphic images.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12880-021-00662-9.

Aluminum exposure promotes the metastatic proclivity of human colorectal cancer cells through matrix metalloproteinases and the TGF-β/Smad signaling pathway

Human exposure to aluminum (Al) mainly occurs through food intake. However, influences of Al on the gastrointestinal tract have been rarely reported. In particular, the effect of Al on the metastasis and angiogenesis of colorectal cancer cells has not been studied. Thus, we investigated the effect of Al on the metastatic proclivity using the human colorectal cancer cell line, HT-29. Cells were exposed to 1-16 mM AlCl₃ for 3-72 h. The effects of AlCl₃ on HT-29 cells for migration/invasion/adhesion, and metastasis-associated protein and gene expression were evaluated. AlCl₃ promoted cell migration and invasion, whereas it suppressed cell adhesion. AlCl₃-exposed cells showed decreased E-cadherin and increased vimentin and Snail. AlCl₃ increased transforming growth factor-beta (TGF-β) mRNA expression and Smad2/3 nuclear translocation. AlCl₃-treated cells had a higher mRNA expression of matrix metalloproteinase (MMP)-7 and -9 than the control. Particularly, AlCl₃-treated HT-29 cells promoted the angiogenesis of endothelial cells via increasing the secretion of vascular endothelial growth factor. Taken together, AlCl₃ can promote the metastatic proclivity of colorectal cancer cells through MMP-7, -9, and TGF-β/Smad2/3 pathway. Our data suggest that Al exposure of the gastrointestinal tract may be a risk factor for metastasis initiation in colorectal cancer cells.

MicroRNAs as Regulators of Prostate Cancer Metastasis

Prostate cancer causes significant morbidity in men and metastatic disease is a major cause of cancer related deaths. Prostate metastasis is controlled by various cellular intrinsic and extrinsic factors, which are often under the regulatory control of various metastasis-associated genes. Given the dynamic nature of metastatic cancer cells, the various factors controlling this process are themselves regulated by microRNAs which are small non-coding RNAs. Significant research work has shown differential microRNA expression in primary and metastatic prostate cancer suggesting their importance in prostate pathogenesis. We will review the roles of different microRNAs in controlling the various steps in prostate metastasis.

Liver Metastasis Is Facilitated by the Adherence of Circulating Tumor Cells to Vascular Fibronectin Deposits

The interaction between circulating tumor cells (CTC) and endothelial cells during extravasation is a critical process during metastatic colonization, but its mechanisms remain poorly characterized. Here we report that the luminal side of liver blood vessels contains fibronectin deposits that are enriched in mice bearing primary tumors and are also present in vessels from human livers affected with metastases. Cancer cells attached to endothelial fibronectin deposits via talin1, a major component of focal adhesions. Talin1 depletion impaired cancer cell adhesion to the endothelium and transendothelial migration, resulting in reduced liver metastasis formation in vivo Talin1 expression levels in patient CTC's correlated with prognosis and therapy response. Together, our findings uncover a new mechanism for liver metastasis formation involving an active contribution of hepatic vascular fibronectin and talin1 in cancer cells. Cancer Res; 77(13); 3431-41. ©2017 AACR.

Computational modeling of radiobiological effects in bone metastases for different radionuclides

PURPOSE

Computational simulation is a simple and practical way to study and to compare a variety of radioisotopes for different medical applications, including the palliative treatment of bone metastases. This study aimed to evaluate and compare cellular effects modelled for different radioisotopes currently in use or under research for treatment of bone metastases using computational methods.

METHODS

Computational models were used to estimate the radiation-induced cellular effects (Virtual Cell Radiobiology algorithm) post-irradiation with selected particles emitted by Strontium-89 (⁸⁹Sr), Samarium-153 (¹⁵³Sm), Lutetium-177 (¹⁷⁷Lu), and Radium-223 (²²³Ra).

RESULTS

Cellular kinetics post-irradiation using ⁸⁹Sr β^- particles, ¹⁵³Sm β^-particles, ¹⁷⁷Lu β^-particles and ²²³Ra α particles showed that the cell response was dose- and radionuclide-dependent. ¹⁷⁷Lu beta minus particles and, in particular, ²²³Ra alpha particles, yielded the lowest survival fraction of all investigated particles.

CONCLUSIONS

²²³Ra alpha particles induced the highest cell death of all investigated particles on metastatic prostate cells in comparison to irradiation with β^-radionuclides, two of the most frequently used radionuclides in the palliative treatment of bone metastases in clinical routine practice. Moreover, the data obtained suggest that the used computational methods might provide some perception about cellular effects following irradiation with different radionuclides.

Nanoparticle Targeting CD44-Positive Cancer Cells for Site-Specific Drug Delivery in Prostate Cancer Therapy

Prostate cancer is one of the leading causes of cancer death in adult men and is a multistage disease with therapeutic challenges of local recurrent advanced tumors and distant metastatic disease. CD44 is a multifunctional and multistructural cell surface glycoprotein that is involved in cell-cell interactions, cell proliferation, and cell migration. In the study, we produced negatively charged and biocompatible hyaluronic acid-based nanoparticles as a therapeutic system for targeting CD44-positive cancer cells. Subsequently, we confirmed the delivery of bioactive epigallocatechin-3-gallate and site-specific inhibition of prostate tumor growth. In this study, hyaluronic acid-based nanoparticles successfully encapsulated epigallocatechin-3-gallate and were efficiently internalized into cancer cells via CD44 ligand receptor recognition, induced cell cycle arrest at G2/M phase, and inhibited prostate cancer cell growth. Furthermore, in vivo assays indicated that these nanoparticles specifically bind CD44 receptors and increase apoptosis of cancer cells, leading to significant decreases in prostate tumor activity and tumor tissue inflammation.

Nemo-like kinase as a negative regulator of nuclear receptor Nurr1 gene transcription in prostate cancer

Background

Nurr1, a member of the orphan receptor family, plays an important role in several types of cancer. Our previous work demonstrated that increased expression of Nurr1 plays a significant role in the initiation and progression of prostate cancer (PCa), though the mechanisms for regulation of Nurr1 expression remain unknown. In this study, we investigated the hypothesis that Nemo-like kinase (NLK) is a key regulator of Nurr1 expression in PCa.

Methods

Immunohistochemistry and Western blot analysis were used to evaluate levels of NLK and Nurr1 in prostatic tissues and cell lines. The effects of overexpression or knockdown of Nurr1 were evaluated in PCa cells through use of PCR, Western blots and promoter reporter assays. The role of Nurr1 promoter cis element was studied by creation of two mutant Nurr1 promoter luciferase constructs, one with a mutated NF-κB binding site and one with a mutated CREB binding site. In addition, three specific inhibitors were used to investigate the roles of these proteins in transcriptional activation of Nurr1, including BAY 11–7082 (NF-κB inhibitor), KG-501 (CREB inhibitor) and ICG-001 (CREB binding protein, CBP, inhibitor). The function of CBP in NLK-mediated regulation of Nurr1 expression was investigated using immunofluorescence, co-immunoprecipitation (Co-IP) and chromatin immunoprecipitation assays (ChIPs).

Results

NLK expression was inversely correlated with Nurr1 expression in prostate cancer tissues and cell lines. Overexpression of NLK suppressed Nurr1 promoter activity, leading to downregulation of Nurr1 expression. In contrast, knockdown of NLK demonstrated opposite results, leading to upregulation of Nurr1. When compared with the wild-type Nurr1 promoter, mutation of NF-κB- and CREB-binding sites of the Nurr1 promoter region significantly reduced the upregulation of Nurr1 induced by knockdown of NLK in LNCaP cells; treatment with inhibitors of CREB, CBP and NF-κB led to similar results. We also found that NLK directly interacts with CBP, that knockdown of NLK significantly increases the recruitment of CBP to both NF-κB- and CREB-binding sites, and that regulation of NLK on Nurr1 expression is abrogated by knockdown of CBP.

Conclusions

Our results suggest that NLK inhibits transcriptional activation of Nurr1 gene by impeding CBP’s role as a co-activator of NF-κB and CREB in prostate cancer.

PPARγ activation reduces ischemia/reperfusion-induced metastasis in a murine model of hepatocellular carcinoma

Ischemia/reperfusion (I/R) injury during liver resection or transplantation for the treatment of hepatocellular carcinoma (HCC) may increase the risk of metastasis. Peroxisome proliferator-activated receptor-γ (PPARγ) activation has been observed to exert a protective effect against hepatic I/R injury. However, whether PPARγ activation exerts a protective effect against I/R-associated liver metastasis remains unknown. Therefore, the present study aimed to investigate the effects of the PPAR agonist rosiglitazone and the specific PPARγ antagonist GW9662 on tumor metastasis following hepatic I/R. An experimental mouse model of hepatic I/R-induced HCC metastasis was designed in order to determine the effects of I/R on tumor metastasis in the liver. Four groups were established: Sham, control (I/R), rosiglitazone (Ro) and rosiglitazone with GW9662 (Ro + GW) groups. In the latter two groups, the treatments were administered intravenously 1 h prior to the induction of ischemia. Tumor load was measured 12 days after the procedure. Furthermore, tissue analyses were conducted to determine the expression levels of alanine aminotransferase, myeloperoxidase (MPO), matrix metalloproteinase (MMP)-9, vascular cell adhesion molecule (VCAM)-1, nuclear factor (NF)-κB and PPARγ. Rosiglitazone pretreatment appeared to significantly mitigate hepatic I/R injury, as indicated by serological and histological analysis. The levels of VCAM-1, MPO and MMP-9 expression in the Ro group were significantly reduced at 8 h following ischemia compared with those in the control and Ro + GW groups. In addition, rosiglitazone inhibited the I/R-induced activation of NF-κB, and GW9662 attenuated the inhibitory effect. To the best of our knowledge, the present study is the first to report on the expression and the functional roles of PPARγ in I/R-associated metastasis. Short-term treatment of mice with rosiglitazone, a potent PPARγ agonist, confers protective effects against hepatic I/R-associated metastasis. Thus, PPARγ may be a potential therapeutic target for the protection of the liver against I/R-associated metastasis.

Cancer-Osteoblast Interaction Reduces Sost Expression in Osteoblasts and Up-Regulates lncRNA MALAT1 in Prostate Cancer

Dynamic interaction between prostate cancer and the bone microenvironment is a major contributor to metastasis of prostate cancer to bone. In this study, we utilized an in vitro co-culture model of PC3 prostate cancer cells and osteoblasts followed by microarray based gene expression profiling to identify previously unrecognized prostate cancer–bone microenvironment interactions. Factors secreted by PC3 cells resulted in the up-regulation of many genes in osteoblasts associated with bone metabolism and cancer metastasis, including Mmp13, Il-6 and Tgfb2, and down-regulation of Wnt inhibitor Sost. To determine whether altered Sost expression in the bone microenvironment has an effect on prostate cancer metastasis, we co-cultured PC3 cells with Sost knockout (Sost^KO) osteoblasts and wildtype (WT) osteoblasts and identified several genes differentially regulated between PC3-Sost^KO osteoblast co-cultures and PC3-WT osteoblast co-cultures. Co-culturing PC3 cells with WT osteoblasts up-regulated cancer-associated long noncoding RNA (lncRNA) MALAT1 in PC3 cells. MALAT1 expression was further enhanced when PC3 cells were co-cultured with Sost^KO osteoblasts and treatment with recombinant Sost down-regulated MALAT1 expression in these cells. Our results suggest that reduced Sost expression in the tumor microenvironment may promote bone metastasis by up-regulating MALAT1 in prostate cancer.

Exosomes secreted under hypoxia enhance invasiveness and stemness of prostate cancer cells by targeting adherens junction molecules

Hypoxic conditions in prostate cancer (PCA) are associated with poor prognosis; however, precise mechanism/s through which hypoxia promotes malignant phenotype remains unclear. Here, we analyzed the role of exosomes from hypoxic PCA cells in enhancing the invasiveness and stemness of naïve PCA cells, as well as in promoting cancer-associated fibroblast (CAF) phenotype in prostate stromal cells (PrSC). Human PCA LNCaP and PC3 cells were exposed to hypoxic (1% O2 ) or normoxic (21% O2 ) conditions, and exosomes secreted under hypoxic (Exo(Hypoxic) ) and normoxic (Exo(Normoxic) ) conditions were isolated from conditioned media. Nanoparticle tracking analysis revealed that Exo(Hypoxic) have smaller average size as compared to Exo(Normoxic) . Immunoblotting results showed a higher level of tetraspanins (CD63 and CD81), heat shock proteins (HSP90 and HSP70), and Annexin II in Exo(Hypoxic) compared to Exo(Normoxic) . Co-culturing with Exo(Hypoxic) increased the invasiveness and motility of naïve LNCaP and PC3 cells, respectively. Exo(Hypoxic) also promoted prostasphere formation by both LNCaP and PC3 cells, and enhanced α-SMA (a CAF biomarker) expression in PrSC. Compared to Exo(Normoxic) , Exo(Hypoxic) showed higher metalloproteinases activity and increased level of diverse signaling molecules (TGF-β2, TNF1α, IL6, TSG101, Akt, ILK1, and β-catenin). Furthermore, proteome analysis revealed a higher number of proteins in Exo(Hypoxic) (160 proteins) compared to Exo(Normoxic) (62 proteins), primarily associated with the remodeling of epithelial adherens junction pathway. Importantly, Exo(Hypoxic) targeted the expression of adherens junction proteins in naïve PC3 cells. These findings suggest that Exo(Hypoxic) are loaded with unique proteins that could enhance invasiveness, stemness, and induce microenvironment changes; thereby, promoting PCA aggressiveness.

miR-25 Modulates Invasiveness and Dissemination of Human Prostate Cancer Cells via Regulation of αv- and α6-Integrin Expression

Altered microRNA (miRNA; miR) expression is associated with tumor formation and progression of various solid cancers. A major challenge in miRNA expression profiling of bulk tumors is represented by the heterogeneity of the subpopulations of cells that constitute the organ, as well as the tumor tissue. Here, we analyzed the expression of miRNAs in a subpopulation of epithelial stem/progenitor-like cells in human prostate cancer [prostate cancer stem cell (PCSC)] and compared their expression profile to more differentiated cancer cells. In both cell lines and clinical prostate cancer specimens, we identified that miR-25 expression in PCSCs was low/absent and steadily increased during their differentiation into cells with a luminal epithelial phenotype. Functional studies revealed that overexpression of miR-25 in prostate cancer cell lines and selected subpopulation of highly metastatic and tumorigenic cells (ALDH(high)) strongly affected the invasive cytoskeleton, causing reduced migration in vitro and metastasis via attenuation of extravasation in vivo. Here, we show, for the first time, that miR-25 can act as a tumor suppressor in highly metastatic PCSCs by direct functional interaction with the 3'-untranslated regions of proinvasive αv- and α6-integrins. Taken together, our observations suggest that miR-25 is a key regulator of invasiveness in human prostate cancer through its direct interactions with αv- and α6-integrin expression.

SNAI1 is critical for the aggressiveness of prostate cancer cells with low E-cadherin

BACKGROUND

A better molecular understanding of prostate carcinogenesis is warranted to devise novel targeted preventive and therapeutic strategies against prostate cancer (PCA), a major cause of mortality among men. Here, we examined the role of two epithelial-to-mesenchymal transition (EMT) regulators, the adherens junction protein E-cadherin and its transcriptional repressor SNAI1, in regulating the aggressiveness of PCA cells.

METHODS

The growth rate of human prostate carcinoma PC3 cells with stable knock-down of E-cadherin (ShEC-PC3) and respective control cells (Sh-PC3) was compared in MTT and clonogenic assays in cell culture and in nude mouse xenograft model in vivo. Stemness of ShEC-PC3 and Sh-PC3 cells was analyzed in prostasphere assay. Western blotting and immunohistochemistry (IHC) were used to study protein expression changes following E-cadherin and SNAI1 knock-down. Small interfering RNA (siRNA) technique was employed to knock- down SNAI1 protein expression in ShEC-PC3 cells.

RESULTS

ShEC-PC3 cells exerted higher proliferation rate both in cell culture and in athymic nude mice compared to Sh-PC3 cells. ShEC-PC3 cells also formed larger and a significantly higher number of prostaspheres suggesting an increase in the stem cell-like population with E-cadherin knock-down. Also, ShEC-PC3 prostaspheres disintegration, in the presence of serum and attachment, generated a bigger mass of proliferating cells as compared to Sh-PC3 prostaspheres. Immunoblotting/IHC analyses showed that E-cadherin knock-down increases the expression of regulators/biomarkers for stemness (CD44, cleaved Notch1 and Egr-1) and EMT (Vimentin, pSrc-tyr416, Integrin β3, β-catenin, and NF-κB) in cell culture and xenograft tissues. The expression of several bone metastasis related molecules namely CXCR4, uPA, RANKL and RunX2 was also increased in ShEC-PC3 cells. Importantly, we observed a remarkable increase in SNAI1 expression in cytoplasmic and nuclear fractions, prostaspheres and xenograft tissues of ShEC-PC3 cells. Furthermore, SNAI1 knock-down by specific siRNA strongly inhibited the prostasphere formation, clonogenicity and invasiveness, and decreased the level of pSrc-tyr416, total Src and CD44 in ShEC-PC3 cells. Characterization of RWPE-1, WPE1-NA22, WPE1-NB14 and DU-145 cells further confirmed that low E-cadherin is associated with higher SNAI1 expression and prostasphere formation.

CONCLUSIONS

Together, these results suggest that E-cadherin loss promotes SNAI1 expression that controls the aggressiveness of PCA cells.

Targeting tumor microenvironment with silibinin: promise and potential for a translational cancer chemopreventive strategy

Tumor microenvironment (TME) refers to the dynamic cellular and extra-cellular components surrounding tumor cells at each stage of the carcinogenesis. TME has now emerged as an integral and inseparable part of the carcinogenesis that plays a critical role in tumor growth, angiogenesis, epithelial to mesenchymal transition (EMT), invasion, migration and metastasis. Besides its vital role in carcinogenesis, TME is also a better drug target because of its relative genetic stability with lesser probability for the development of drug-resistance. Several drugs targeting the TME (endothelial cells, macrophages, cancer-associated fibroblasts, or extra-cellular matrix) have either been approved or are in clinical trials. Recently, non-steroidal anti-inflammatory drugs targeting inflammation were reported to also prevent several cancers. These exciting developments suggest that cancer chemopreventive strategies targeting both tumor and TME would be better and effective towards preventing, retarding or reversing the process of carcinogenesis. Here, we have reviewed the effect of a well established hepatoprotective and chemopreventive agent silibinin on cellular (endothelial, fibroblast and immune cells) and non-cellular components (cytokines, growth factors, proteinases etc.) of the TME. Silibinin targets TME constituents as well as their interaction with cancer cells, thereby inhibiting tumor growth, angiogenesis, inflammation, EMT, and metastasis. Silibinin is already in clinical trials, and based upon completed studies we suggest that its chemopreventive effectiveness should be verified through its effect on biological end points in both tumor and TME. Overall, we believe that the chemopreventive strategies targeting both tumor and TME have practical and translational utility in lowering the cancer burden.

Is prostate cancer changing?: evolving patterns of metastatic castration-resistant prostate cancer

BACKGROUND

Metastatic castration-resistant prostate cancer (mCRPC) most commonly metastasizes to the bone, and less commonly to nonosseous sites (eg, lymph nodes, liver, lung). With new therapies extending survival in mCRPC, it was hypothesized that the pattern of metastases is changing over time. The pattern of metastatic disease was evaluated in men with mCRPC, as reported in baseline characteristics of prospective clinical trials over 2 decades.

METHODS

This study identified all phase 2 and 3 therapeutic studies in men with mCRPC in PubMed and American Society of Clinical Oncology abstracts from 1990 to 2012. Studies were excluded if they did not report demographic data and sites of metastasis, or excluded patients with a specific site of metastatic disease (except brain). For each type of metastasis, weighted least squares linear regression models were used to evaluate temporal trends.

RESULTS

A total of 290 eligible studies (270 phase 2 studies and 20 phase 3 studies) involving 19,110 patients were identified. Between 1990 and 2012, the rate of nonosseous metastasis increased significantly at 1.6% per year (P < .0001), whereas the rate of osseous metastasis decreased at 0.5% per year (P < .0001). The rate of lymph node metastasis increased at 1.4% per year (P < .0001), but the rate of liver and lung metastasis remained relatively stable.

CONCLUSIONS

A notable change was found in the pattern of metastasis in patients with mCRPC. Because these evolving patterns may have important implications in treatment selection and prognosis, it is crucial that future clinical trials of patients with mCRPC define patients with a uniform reporting of nonosseous metastasis.

Increased expression of putative cancer stem cell markers in the bone marrow of prostate cancer patients is associated with bone metastasis progression

BACKGROUND

The number of cells positive for the α-6 and α-2 integrin subunits and the c-Met receptor in primary tumors and bone biopsies from prostate cancer patients has been correlated with metastasis and disease progression. The objective of this study was to quantify disseminated tumour cells present in bone marrow in prostate cancer patients using specific markers and determine their correlation with metastasis and survival.

METHODS

Patients were included at different stage of prostate cancer disease, from localised to metastatic castration-resistant prostate cancer. Healthy men were used as a control group. Bone marrow samples were collected and nucleated cells separated. These were stained for CD45, α-2, α-6 integrin subunits and c-Met and samples were processed for analysis and quantification of CD45-/α2+/α6+/c-met + cells using flow cytometry. Clinical and pathological parameters were assessed and survival measured. Statistical analyses were made of associations between disease specific parameters, bone marrow flow cytometry data, prostate-specific antigen (PSA) progression free survival and bone metastases progression free survival.

RESULTS

For all markers, the presence of more than 0.1% positive cells in bone marrow aspirates was significantly associated with the risk of biochemical progression, the risk of developing metastasis and death from prostate cancer.

CONCLUSIONS

Quantification of cells carrying putative stem cell markers in bone marrow is a potential indicator of disease progression. Functional studies on isolated cells are needed to show more specifically their property for metastatic spread in prostate cancer.

Epigallocatechin gallate inhibits growth and epithelial-to-mesenchymal transition in human thyroid carcinoma cell lines

Well-differentiated papillary and follicular thyroid carcinoma are the most frequent types of thyroid cancer and the prognosis is generally favorable however, a number of patients develops recurrences. Epigallocatechin-3-gallate (EGCG), a major catechin in green tea, was shown to possess remarkable therapeutic potential against various types of human cancers, although data on thyroid cancer cells are still lacking. The aim of this study was to investigate the effect of EGCG on the proliferation and motility of human thyroid papillary (FB-2) and follicular (WRO) carcinoma cell lines. Our results demonstrate that EGCG (10, 40, 60 μM) treatment inhibited the growth of FB-2 and WRO cells in a dose-dependent manner. These changes were associated with reduced cyclin D1, increased p21 and p53 expression. Furthermore, EGCG suppressed phosphorylation of AKT and ERK1/2. In addition EGCG treatment results in reduction of cell motility and migration. Changes in motility and migration in FB-2 were associated with modulation in the expression of several proteins involved in cell adhesion and reorganization of actin cytoskeleton. After 24 h EGCG caused an increase of the E-cadherin expression and a concomitant decrease of SNAIL, ZEB and the basic helix-loop-helix transcription factor TWIST. Besides expression of Vimentin, N-cadherin and α5-integrin was down-regulated. These data well correlate with a reduction of MMP9 activity as evidenced by gelatin zymography. Our findings support the inhibitory role of EGCG on thyroid cancer cell proliferation and motility with concomitant loss of epithelial-to-mesenchymal cell transition markers.

Suppression of interactions between prostate tumor cell-surface integrin and endothelial ICAM-1 by simvastatin inhibits micrometastasis

Cancer micrometastasis relies on the ability of cancer cells to secrete angiogenic modulators, to interact with the vascular endothelium, and to overcome the resistance offered by the endothelial-barrier. Being an essential step prior to metastasis, blockage of micrometastasis can have potential applications in cancer therapy and metastasis prevention. Due to poorly known molecular mechanisms leading to micrometastasis, developing therapeutic strategies to target prostate cancer utilizing drugs that block micrometastasis is far from reality. Here, we demonstrate the potential benefits of simvastatin in the inhibition of prostate cancer micrometastasis and reveal the novel molecular mechanisms underlying this process. First, we showed that simvastatin inhibited the ability of human PC3 prostate cancer cells for transendothelial migration in vitro. Second, our data indicated that simvastatin modulates the expression of tumor-derived factors such as angiopoietins and VEGF-A at the mRNA and protein levels by the PC3 cells, thus preventing endothelial-barrier disruption. Third, simvastatin directly activated endothelial cells and enhances endothelial-barrier resistance. Apart from this, our study revealed that simvastatin-mediated effect on PC3 micrometastasis was mediated through inhibition of integrin αv β3 activity and suppression of interaction between prostate cancer cell integrin αv β3 with endothelial ICAM-1.

The impaired viability of prostate cancer cell lines by the recombinant plant kallikrein inhibitor

BACKGROUND

Kallikreins play a pivotal role in establishing prostate cancer.

RESULTS

In contrast to the classical Kunitz plant inhibitor SbTI, the recombinant kallikrein inhibitor (rBbKIm) led to prostate cancer cell death, whereas fibroblast viability was not affected.

CONCLUSION

rBbKIm shows selective cytotoxic effect and angiogenesis inhibition against prostate cancer cells.

SIGNIFICANCE

New actions of rBbKIm may contribute to understanding the mechanisms of prostate cancer. Prostate cancer is the most common type of cancer, and kallikreins play an important role in the establishment of this disease. rBbKIm is the recombinant Bauhinia bauhinioides kallikreins inhibitor that was modified to include the RGD/RGE motifs of the inhibitor BrTI from Bauhinia rufa. This work reports the effects of rBbKIm on DU145 and PC3 prostate cancer cell lines. rBbKIm inhibited the cell viability of DU145 and PC3 cells but did not affect the viability of fibroblasts. rBbKIm caused an arrest of the PC3 cell cycle at the G0/G1 and G2/M phases but did not affect the DU145 cell cycle, although rBbKIm triggers apoptosis and cytochrome c release into the cytosol of both cell types. The differences in caspase activation were observed because rBbKIm treatment promoted activation of caspase-3 in DU145 cells, whereas caspase-9 but not caspase-3 was activated in PC3 cells. Because angiogenesis is important to the development of a tumor, the effect of rBbKIm in this process was also analyzed, and an inhibition of 49% was observed in in vitro endothelial cell capillary-like tube network formation. In summary, we demonstrated that different properties of the protease inhibitor rBbKIm may be explored for investigating the androgen-independent prostate cancer cell lines PC3 and DU145.

Cancer of the prostate presenting with diffuse osteolytic metastatic bone lesions: a case report

INTRODUCTION

Prostate cancer is the second most common cancer in men and the fifth most common cancer worldwide. In the USA it is more common in African-American men than in Caucasian men. Prostate cancer frequently metastasizes to bone and the lesions appear osteoblastic on radiographs. Presentation with diffuse osteolytic bone lesions is rare. We describe an unusual presentation of metastatic prostate cancer with diffuse osteolytic bone lesions.

CASE PRESENTATION

A 65-year-old Namibian man presented with anemia, thrombocytopenia and worsening back pains. In addition he had complaints of effort intolerance, palpitations, dysuria and mild symptoms of bladder outlet obstruction. On examination he was found to be anemic, had a swollen tender right shoulder joint and spine tenderness to percussion. On digital rectal examination he had asymmetrical enlargement of the prostate which felt nodular and hard with diffuse firmness in some parts. His prostate-specific antigen was greater than 100ng/mL and he had diffuse osteolytic lesions involving the right humerus, and all vertebral, femur and pelvic bones. His screen for multiple myeloma was negative and the prostate biopsy confirmed prostate cancer.

CONCLUSION

Prostate cancer rarely presents with diffuse osteolytic bone lesions and should be considered in the differential diagnosis when evaluating male patients with osteolytic bone lesions.

Inhibition of prostate cancer bone metastasis by synthetic TF antigen mimic/galectin-3 inhibitor lactulose-L-leucine

Currently incurable, prostate cancer metastasis has a remarkable ability to spread to the skeleton. Previous studies demonstrated that interactions mediated by the cancer-associated Thomsen-Friedenreich glycoantigen (TF-Ag) and the carbohydrate-binding protein galectin-3 play an important role in several rate-limiting steps of cancer metastasis such as metastatic cell adhesion to bone marrow endothelium, homotypic tumor cell aggregation, and clonogenic survival and growth. This study investigated the ability of a synthetic small-molecular-weight nontoxic carbohydrate-based TF-Ag mimic lactulose-L-leucine (Lac-L-Leu) to inhibit these processes in vitro and, ultimately, prostate cancer bone metastasis in vivo. Using an in vivo mouse model, based on intracardiac injection of human PC-3 prostate carcinoma cells stably expressing luciferase, we investigated the ability of Lac-L-Leu to impede the establishment and growth of bone metastasis. Parallel-flow chamber assay, homotypic aggregation assay, modified Boyden chamber assay, and clonogenic growth assay were used to assess the effects of Lac-L-Leu on tumor cell adhesion to the endothelium, homotypic tumor cell aggregation, transendothelial migration, and clonogenic survival and growth, respectively. We report that daily intraperitoneal administration of Lac-L-Leu resulted in a three-fold (P < .05) decrease in metastatic tumor burden compared with the untreated control. Mechanistically, the effect of Lac-L-Leu, which binds and inhibits galectins by mimicking essential structural features of the TF-Ag, was associated with a dose-dependent inhibition of prostate cancer cell adhesion to bone marrow endothelium, homotypic aggregation, transendothelial migration, and clonogenic growth. We conclude that small-molecular-weight carbohydrate-based compounds targeting β-galactoside-mediated interactions could provide valuable means for controlling and preventing metastatic prostate cancer spread to the skeleton.

Targeting of α(v)-integrins in stem/progenitor cells and supportive microenvironment impairs bone metastasis in human prostate cancer

Acquisition of an invasive phenotype by cancer cells is a requirement for bone metastasis. Transformed epithelial cells can switch to a motile, mesenchymal phenotype by epithelial-mesenchymal transition (EMT). Recently, it has been shown that EMT is functionally linked to prostate cancer stem cells, which are not only critically involved in prostate cancer maintenance but also in bone metastasis. We showed that treatment with the non-peptide α(v)-integrin antagonist GLPG0187 dose-dependently increased the E-cadherin/vimentin ratio, rendering the cells a more epithelial, sessile phenotype. In addition, GLPG0187 dose-dependently diminished the size of the aldehyde dehydrogenase high subpopulation of prostate cancer cells, suggesting that α(v)-integrin plays an important role in maintaining the prostate cancer stem/progenitor pool. Our data show that GLPG0187 is a potent inhibitor of osteoclastic bone resorption and angiogenesis in vitro and in vivo. Real-time bioluminescent imaging in preclinical models of prostate cancer demonstrated that blocking α(v)-integrins by GLPG0187 markedly reduced their metastatic tumor growth according to preventive and curative protocols. Bone tumor burden was significantly lower in the preventive protocol. In addition, the number of bone metastases/mouse was significantly inhibited. In the curative protocol, the progression of bone metastases and the formation of new bone metastases during the treatment period was significantly inhibited. In conclusion, we demonstrate that targeting of integrins by GLPG0187 can inhibit the de novo formation and progression of bone metastases in prostate cancer by antitumor (including inhibition of EMT and the size of the prostate cancer stem cell population), antiresorptive, and antiangiogenic mechanisms.

Evaluation of the expression of integrins and cell adhesion molecules through tissue microarray in lymph node metastases of prostate cancer

Background:

Integrins and adhesion molecules are responsible for the maintenance of the epithelial phenotype. Cell culture studies have reported the correlation between adhesion molecule expression and prostate carcinoma, but their role in the metastatic process is not yet known. Our aim is to study the expression profiles of these molecules and evaluate their association with the metastatic behavior of prostate adenocarcinoma.

Materials and Methods:

A Tissue Microarray containing two samples from 19 primary tumors and one from their corresponding lymph node metastases was constructed and subjected to immunohistochemical analysis of the expression of integrins, E-cadherin and β and γ-catenins. Within each case, paired analyses were also performed to evaluate gains or losses in metastasis compared to its primary tumor.

Results:

The expression of αv, αvβ3, α2β1 and γ-catenin were abnormal in almost every case. Marked loss of E-cadherin and β4 integrin was found in primary and metastatic lesions. β-catenin was normal in all primary cases and in 94% of metastases. α6 was normal in all primary tumors and metastases. α3 and α3β1 were normal in 32% of primary cases and in 53% and 6% of metastases, respectively. In paired analyses, loss of E-cadherin, β4, αv, α3β1 and αvβ3 was found in 65%, 71%, 59%, 53% and 47% of patients, respectively. Catenins and α2β1 showed maintenance of expression in most of the cases.

Conclusions:

In this preliminary study we have shown that the loss of cell adhesion molecules can be considered a characteristic of the metastatic phenotype in prostate cancer. Larger series should be evaluated in order to confirm our findings.

Preventing bone complications in advanced prostate cancer

The diagnosis and treatment of prostate cancer have steadily been improving since the late 1980s. However, clinicians still confront a large group of men developing disease metastatic to bone. Adequate control of bone complications plays a fundamental role in achieving control of symptoms and quality of life in this group. Androgen deprivation therapy, the standard treatment for advanced prostate cancer, increases the risk of various complications, including bone disease. This review addresses the prevention of bone complications related not only to prostate cancer metastases but also to impaired bone integrity caused by androgen deprivation therapy.

Role of E-cadherin in antimigratory and antiinvasive efficacy of silibinin in prostate cancer cells

The epithelial-to-mesenchymal transition (EMT) in prostate cancer (PCA) cells is considered prerequisite for acquiring migratory/invasive phenotype, and subsequent metastasis. We hypothesized that promoting the E-cadherin expression in PCA cells by using nontoxic phytochemicals, like silibinin, would prevent EMT and consequently invasiveness. Our results showed that silibinin treatment (5-90 μmol/L) significantly inhibits migratory and invasive potential of advance human PCA PC3, PC3MM2, and C4-2B cells in in vitro assays. Importantly, the antimigratory/antiinvasive efficacy of silibinin was not due to its cytotoxicity toward PCA cells. Molecular analyses showed that silibinin increases E-cadherin level that was localized mainly at cellular membrane as evidenced by subcellular fractional and confocal analyses in PC3 cells, which might be responsible for morphologically observed shift toward epithelial character. Silibinin also decreased the levels of Slug, Snail, phospho-Akt(ser(473)), nuclear β-catenin, phospho-Src(tyr(419)) and Hakai; together they play an important role in regulating E-cadherin expression/function and EMT. Similar silibinin effects on E-cadherin, β-catenin, phospho-Src(tyr(419)), and Hakai levels were also observed in PC3MM2 and C4-2B PCA cells. Selective Src inhibition by dasatinib also showed increased E-cadherin expression in PC3 cells suggesting a possible involvement of Src inhibition in silibinin-caused increase in E-cadherin level. Additional studies in PC3 cells with stable knock-down of E-cadherin expression revealed that antimigratory/antiinvasive efficacy of silibinin is in-part dependent on E-cadherin expression. Together, our results showing antimigratory/antiinvasive effects of silibinin and associated mechanisms suggest that silibinin should be tested further in clinically relevant animal models toward exploiting its potential benefits against metastatic PCA.

Novel α(2)β(1) integrin-targeted peptide probes for prostate cancer imaging

Accumulating experimental evidence indicates that overexpression of α(2)β(1) integrin may correlate with progression in human prostate cancer. The objective of this study was to design a novel imaging probe based on the Asp-Gly-Glu-Ala (DGEA) peptide for near-infrared-fluorescent (NIRF) imaging of α(2)β(1) integrin expression in prostate cancer. The peptides were conjugated with appropriate fluorescent dyes, and the binding affinity of these probes was evaluated by flow cytometry in three human prostate cell lines (PC-3, CWR-22, and LNCaP). In vivo NIRF imaging of the α(2)β(1)-positive PC-3 xenograft model was performed to evaluate the α(2)β(1) targeted probe. In vitro immunofluorescence staining was carried out to confirm the α(2)β(1) integrin expression level. Flow cytometry analysis showed that PC-3 had the highest probe uptake, followed by CWR-22 and LNCaP tumor cells. In the subcutaneous PC-3 model, the tumor demonstrated prominent uptake with good tumor to background contrast. Immunohistochemistry staining also supported the in vivo optical imaging results. DGEA-based optical agents have been developed for specific imaging of α(2)β(1) integrin expression. In vitro and in vivo localization demonstrated the potential of this agent to identify tumor subtypes amenable to anti-α(2)β(1) integrin treatment and potentially provide prognostic information regarding tumor progression.

Design, synthesis and validation of integrin α2β1-targeted probe for microPET imaging of prostate cancer

PURPOSE

The ability of PET to aid in the diagnosis and management of recurrent and/or disseminated metastatic prostate cancer may be enhanced by the development of novel prognostic imaging probes. Accumulating experimental evidence indicates that overexpression of integrin α(2)β(1) may correlate with progression in human prostate cancer. In this study, (64)Cu-labeled integrin α(2)β(1)-targeted PET probes were designed and evaluated for the imaging of prostate cancer.

METHODS

DGEA peptides conjugated with a bifunctional chelator (BFC) were developed to image integrin α(2)β(1) expression with PET in a subcutaneous PC-3 xenograft model. The microPET images were reconstructed by a two-dimensional ordered subsets expectation maximum algorithm. The average radioactivity accumulation within a tumor or an organ was quantified from the multiple region of interest volumes.

RESULTS

The PET tracer demonstrated prominent tumor uptake in the PC-3 xenograft (integrin α(2)β(1)-positive). The receptor specificity was confirmed in a blocking experiment. Moreover, the low tracer uptake in a CWR-22 tumor model (negative control) further confirmed the receptor specificity.

CONCLUSION

The sarcophagine-conjugated DGEA peptide allows noninvasive imaging of tumor-associated α(2)β(1) expression, which may be a useful PET probe for evaluating the metastatic potential of prostate cancer.

Significance of talin in cancer progression and metastasis

Upon detachment from the extracellular matrix, tumor epithelial cells and tumor-associated endothelial cells are capable of overcoming anoikis, gain survival benefits, and hence contribute to the process of metastasis. The focal-adhesion complex formation recruits the association of key adaptor proteins such as FAK (focal-adhesion kinase). Vimentin, paxillin, and talin are responsible for mediating the interaction between the actin cytoskeleton and integrins. Talin is an early-recruited focal-adhesion player that is of structural and functional significance in mediating interactions with integrin cytoplasmic tails leading to destabilization of the transmembrane complex and resulting in rearrangements in the extracellular integrin compartments that mediate integrin activation. Talin-mediated integrin activation plays a definitive role in integrin-mediated signaling and induction of downstream survival pathways leading to protection from anoikis and consequently resulting in cancer progression to metastasis. We recently reported that talin expression is significantly increased in prostate cancer compared with benign and normal prostate tissue and that this overexpression correlates with progression to metastatic disease implicating a prognostic value for talin during tumor progression. At the molecular level, talin is functionally associated with enhanced survival and proliferation pathways and confers anoikis resistance and metastatic spread of primary tumor cells via activation of the Akt survival pathway. In this review, we discuss the growing evidence surrounding the value of talin as a prognostic marker of cancer progression to metastasis and as therapeutic target in advanced prostate cancer, as well as the current understanding of mechanisms regulating its signaling activity in cancer.

Antimetastatic efficacy of silibinin: molecular mechanisms and therapeutic potential against cancer

Cancer is a major health problem around the world. Research efforts in the last few decades have been successful in providing better and effective treatments against both early stage and localized cancer, but clinical options against advanced metastatic stage/s of cancer remain limited. The high morbidity and mortality in most of the cancers are attributed to their metastatic spread to distant organs. Due to its extreme clinical relevance, metastasis has been extensively studied and is now understood as a highly complex biological event that involves multiple steps including acquisition of invasiveness by cancer cells, intravasation into circulatory system, survival in the circulation, arrest in microvasculature, extravasation, and growth at distant organs. The increasing understanding of molecular underpinnings of these events has provided excellent opportunity to target metastasis especially through nontoxic and biologically effective nutraceuticals. Silibinin, a popular dietary supplement isolated from milk thistle seed extracts, is one such natural agent that has shown biological efficacy through pleiotropic mechanisms against a variety of cancers and is currently in clinical trials. Recent preclinical studies have also shown strong efficacy of silibinin to target cancer cell's migratory and invasive characteristics as well as their ability to metastasize to distant organs. Detailed mechanistic analyses revealed that silibinin targets signaling molecules involved in the regulation of epithelial-to-mesenchymal transition, proteases activation, adhesion, motility, invasiveness as well as the supportive tumor-microenvironment components, thereby inhibiting metastasis. Overall, the long history of human use, remarkable nontoxicity, and preclinical efficacy strongly favor the clinical use of silibinin against advanced metastatic cancers.

Increased potency of the PHSCN dendrimer as an inhibitor of human prostate cancer cell invasion, extravasation, and lung colony formation

Activated alpha5beta1 integrin occurs specifically on tumor cells and on endothelial cells of tumor-associated vasculature, and plays a key role in invasion and metastasis. The PHSCN peptide (Ac-PHSCN-NH(2)) preferentially binds activated alpha5beta1, to block invasion in vitro, and inhibit growth, metastasis and tumor recurrence in preclinical models of prostate cancer. In Phase I clinical trial, systemic Ac-PHSCN-NH(2) monotherapy was well tolerated, and metastatic disease progression was prevented for 4-14 months in one-third of treated patients. We have developed a significantly more potent derivative, the PHSCN-polylysine dendrimer (Ac-PHSCNGGK-MAP). Using in vitro invasion assays with naturally serum-free basement membranes, we observed that the PHSCN dendrimer was 130- to 1900-fold more potent than the PHSCN peptide at blocking alpha5beta1-mediated invasion by DU 145 and PC-3 human prostate cancer cells, whether invasion was induced by serum, or by the Ac-PHSRN-NH(2) peptide, under serum-free conditions. The PHSCN dendrimer was also approximately 800 times more effective than PHSCN peptide at preventing DU 145 and PC-3 extravasation in the lungs of athymic mice. Chou-Talalay analysis suggested that inhibition of both invasion in vitro and extravasation in vivo by the PHSCN dendrimer are highly synergistic. We found that many extravasated DU 145 and PC-3 cells go onto develop into metastatic colonies, and that a single pretreatment with the PHSCN dendrimer was 100-fold more affective than the PHSCN peptide at reducing lung colony formation. Since many patients newly diagnosed with prostate cancer already have locally advanced or metastatic disease, the availability of a well-tolerated, nontoxic systemic therapy, like the PHSCN dendrimer, which prevents metastatic progression by inhibiting invasion, could be very beneficial.

Cilengitide (EMD 121974, NSC 707544) in asymptomatic metastatic castration resistant prostate cancer patients: a randomized phase II trial by the prostate cancer clinical trials consortium

BACKGROUND

Integrins are involved in prostate cancer metastasis by regulating cell adhesion, migration, invasion, motility, angiogenesis and bone metabolism. We evaluated the efficacy of two dose levels of cilengitide in patients (pts) with castrate resistant prostate cancer (CRPC).

METHODS

Chemotherapy-naïve, asymptomatic metastatic CRPC pts were randomized to cilengitide 500 mg or 2,000 mg IV twice weekly using parallel 2-stage design. The primary endpoint was rate of objective clinical progression at 6-months. Secondary endpoints included clinical and PSA response rates, safety and effects of cilengitide treatment on circulating tumor cells (CTCs) and bone remodeling markers.

RESULTS

Forty-four pts were accrued to first stage (22/arm). Median number of cycles was three in both arms (500 mg arm: 1-8; 2,000 mg arm: 1-15). At 6 months, two pts (9%) on the 500 mg arm and five pts (23%) on the 2,000 mg arm had not progressed. Best objective response was stable disease (SD) in seven pts for 9.9[8.1,20.9] months. There were three grade 3 and no grade 4 toxicities. At 12 weeks, analysis of bone markers did not reveal significant trends. At progression, bone specific alkaline phosphatase and N-telopeptide increased in all pts, less so in pts on the 2,000 mg arm and in pts on both arms who obtained SD at 6 months. CTCs increased over time in both arms.

CONCLUSION

Cilengitide was well tolerated with modest clinical effect in favor of the higher dose. The unique trial design including a shift from response rate to objective progression as the endpoint, and not acting on PSA increases was feasible.

Activation of Rap1 promotes prostate cancer metastasis

Elucidating the mechanisms of prostate cancer (CaP) survival and metastasis are critical to the discovery of novel therapeutic targets. The monomeric G protein Rap1 has been implicated in cancer tumorigenesis. Rap1 signals to pathways involved in cell adhesion, migration, and survival, suggesting Rap1 may promote several processes associated with cancer cell metastasis. Examination of CaP cell lines revealed cells with a high metastatic ability exhibited increased Rap1 activity and reduced expression of the negative regulator Rap1GAP. Rap1 can be further stimulated in these cells by stromal-derived factor (SDF-1), an agonist known to regulate tumor cell metastasis and tropism to bone. Activation of Rap1 increased CaP cell migration and invasion, and inhibition of Rap1A activity via RNAi-mediated knockdown or ectopic expression of Rap1GAP markedly impaired CaP cell migration and invasion. Additional studies implicate integrins alpha4, beta3, and alphavbeta3 in the mechanism of Rap1-mediated CaP migration and invasion. Extending the effect of Rap1 activity in CaP metastasis in vivo, introduction of activated Rap1 into CaP cells dramatically enhanced the rate and incidence of CaP metastasis in a xenograft mouse model. These studies provide compelling evidence to support a role for aberrant Rap1 activation in CaP progression, and suggest that targeting Rap1 signaling could provide a means to control metastatic progression of this cancer.

[The natural history of metastatic prostate cancer]

Prostate cancer is a pathology which progress with successive stages directly dependant on hormonosensitivity. When metastasis occur, cell modifications and biologic transformations lead to disease diffusion. PSA is useful to practically follow the evolution of the prostate cancer but it is probably the molecular biology which probably will be necessary to get prognostic and predictive markers of metastasis power. At each step of the metastatic cascade, it is possible to imagine a specific targeted therapy for this disease which is today non curable.

Integrins in prostate cancer progression

Integrins, which are transmembrane receptors for extracellular matrix proteins, play a key role in cell survival, proliferation, migration, gene expression, and activation of growth factor receptors. Their functions and expression are deregulated in several types of cancer, including prostate cancer. In this article, we review the role of integrins in prostate cancer progression and their potential as therapeutic targets.

Reduced growth and integrin expression of prostate cells cultured with lycopene, vitamin E and fish oil in vitro

Integrins are transmembrane proteins that facilitate the interaction of cells with the extracellular environment. They have also been implicated in cancer progression. The effects of nutrients thought to be involved in the prevention of prostate cancer on integrin expression have not been determined. Prostate cancer cell lines representing a range of malignancy from normal (RWPE-1) to highly invasive phenotypes (22Rv1 < LNCaP < PC-3) were cultured with or without lycopene (10 nm), vitamin E (5 μm) or fish oil (100 μm) for 48 h. Growth and integrin (α2β1, αvβ3 and αvβ5) expression were assessed using Trypan Blue exclusion and monoclonal antibodies combined with flow cytometry. Vitamin E enhanced (P < 0·001) whereas fish oil reduced the growth of all the cell lines tested (P < 0·001). Lycopene had no effect on growth. All the malignant cell lines exhibited lower expression of α2β1 with the addition of lycopene to culture media. Supplemental fish oil reduced α2β1 in most invasive cell lines (LNCaP and PC-3). Each nutrient at physiological levels reduced integrins αvβ3 and αvβ5 in most invasive cell lines (PC-3). The results suggest that integrins may represent an additional target of bioactive nutrients and that the effects of nutrients may be dependent on the type of cell line used.

Cadherin-11 promotes the metastasis of prostate cancer cells to bone

Bone is the most common site of metastases from prostate cancer. The mechanism by which prostate cancer cells metastasize to bone is not fully understood, but interactions between prostate cancer cells and bone cells are thought to initiate the colonization of metastatic cells at that site. Here, we show that cadherin-11 (also known as osteoblast-cadherin) was highly expressed in prostate cancer cell line derived from bone metastases and had strong homophilic binding to recombinant cadherin-11 in vitro. Down-regulation of cadherin-11 in bone metastasis-derived PC3 cells with cadherin-11-specific short hairpin RNA (PC3-shCad-11) significantly decreased the adhesion of those cells to cadherin-11 in vitro. In a mouse model of metastasis, intracardiac injection of PC3 cells led to metastasis of those cells to bone. However, the incidence of PC3 metastasis to bone in this model was reduced greatly when the expression of cadherin-11 by those cells was silenced. The clinical relevance of cadherin-11 in prostate cancer metastases was further studied by examining the expression of cadherin-11 in human prostate cancer specimens. Cadherin-11 was not expressed by normal prostate epithelial cells but was detected in prostate cancer, with its expression increasing from primary to metastatic disease in lymph nodes and especially bone. Cadherin-11 expression was not detected in metastatic lesions that occur in other organs. Collectively, these findings suggest that cadherin-11 is involved in the metastasis of prostate cancer cells to bone.

ADAM15 supports prostate cancer metastasis by modulating tumor cell-endothelial cell interaction

Using human tumor and cDNA microarray technology, we have recently shown that the ADAM15 disintegrin is significantly overexpressed during the metastatic progression of human prostate cancer. In the current study, we used lentiviral-based short hairpin RNA (shRNA) technology to down-regulate ADAM15 in the metastatic prostate cancer cell line, PC-3. ADAM15 down-regulation dramatically attenuated many of the malignant characteristics of PC-3 cells in vitro and prevented the s.c. growth of PC-3 cells in severe combined immunodeficient (SCID) mice. By inhibiting the expression of ADAM15 in PC-3 cells, we showed decreased cell migration and adhesion to specific extracellular matrix proteins. This was accompanied by a reduction in the cleavage of N-cadherin by ADAM15 at the cell surface. Fluorescence-activated cell sorting analysis revealed reduced cell surface expression of the metastasis-associated proteins alpha(v) integrin and CD44. Furthermore, matrix metalloproteinase 9 secretion and activity were abrogated in response to ADAM15 reduction. In an in vitro model of vascular invasion, loss of ADAM15 reduced PC-3 adhesion to, and migration through, vascular endothelial cell monolayers. Using an SCID mouse model of human prostate cancer metastasis, we found that the loss of ADAM15 significantly attenuated the metastatic spread of PC-3 cells to bone. Taken together, these data strongly support a functional role for ADAM15 in prostate tumor cell interaction with vascular endothelium and the metastatic progression of human prostate cancer.