SOX9 is expressed in human fetal prostate epithelium and enhances prostate cancer invasion

Activation of c-MET induces a stem-like phenotype in human prostate cancer

Prostate cancer consists of secretory cells and a population of immature cells. The function of immature cells and their mutual relation with secretory cells are still poorly understood. Immature cells either have a hierarchical relation to secretory cells (stem cell model) or represent an inducible population emerging upon appropriate stimulation of differentiated cells. Hepatocyte Growth Factor (HGF) receptor c-MET is specifically expressed in immature prostate cells. Our objective is to determine the role of immature cells in prostate cancer by analysis of the HGF/c-MET pathway.Gene-expression profiling of DU145 prostate cancer cells stimulated with HGF revealed induction of a molecular signature associated with stem cells, characterized by up-regulation of CD49b, CD49f, CD44 and SOX9, and down-regulation of CD24 ('stem-like signature'). We confirmed the acquisition of a stem-like phenotype by quantitative PCR, FACS analysis and Western blotting. Further, HGF led to activation of the stem cell related Notch pathway by up-regulation of its ligands Jagged-1 and Delta-like 4. Small molecules SU11274 and PHA665752 targeting c-MET activity were both able to block the molecular and biologic effects of HGF. Knock-down of c-MET by shRNA infection resulted in significant reduction and delay of orthotopic tumour-formation in male NMRI mice. Immunohistochemical analysis in prostatectomies revealed significant enrichment of c-MET positive cells at the invasive front, and demonstrated co-expression of c-MET with stem-like markers CD49b and CD49f.In conclusion, activation of c-MET in prostate cancer cells induced a stem-like phenotype, indicating a dynamic relation between differentiated and stem-like cells in this malignancy. Its mediation of efficient tumour-formation in vivo and predominant receptor expression at the invasive front implicate that c-MET regulates tumour infiltration in surrounding tissues putatively by acquisition of a stem-like phenotype.

cGMP-dependent protein kinases as potential targets for colon cancer prevention and treatment

In recent years, several antitumor signaling pathways mediated by the cGMP-dependent protein kinases have been identified in colon cancer cells. This review aims to present the mounting evidence in favor of cGMP/protein kinase G (PKG) signaling as a therapeutic strategy in colon cancer. The homeostatic and tumor suppressive effects of cGMP in the intestine are uncontested, but the signaling details are not understood. PKG is the central cGMP effector, and can block proliferation and tumor angiogenesis by inhibiting β-catenin/TCF and SOX9 signaling. Therapeutic activation of cGMP/PKG offers a promising avenue for the prevention and treatment of colon cancer, but additional preclinical studies are needed to fully understand the potential of this system.

Reprogramming transcription by distinct classes of enhancers functionally defined by eRNA

Mammalian genomes are populated with thousands of transcriptional enhancers that orchestrate cell-type-specific gene expression programs, but how those enhancers are exploited to institute alternative, signal-dependent transcriptional responses remains poorly understood. Here we present evidence that cell-lineage-specific factors, such as FoxA1, can simultaneously facilitate and restrict key regulated transcription factors, exemplified by the androgen receptor (AR), to act on structurally and functionally distinct classes of enhancer. Consequently, FoxA1 downregulation, an unfavourable prognostic sign in certain advanced prostate tumours, triggers dramatic reprogramming of the hormonal response by causing a massive switch in AR binding to a distinct cohort of pre-established enhancers. These enhancers are functional, as evidenced by the production of enhancer-templated non-coding RNA (eRNA) based on global nuclear run-on sequencing (GRO-seq) analysis, with a unique class apparently requiring no nucleosome remodelling to induce specific enhancer-promoter looping and gene activation. GRO-seq data also suggest that liganded AR induces both transcription initiation and elongation. Together, these findings reveal a large repository of active enhancers that can be dynamically tuned to elicit alternative gene expression programs, which may underlie many sequential gene expression events in development, cell differentiation and disease progression.

Androgen regulation of epithelial-mesenchymal transition in prostate tumorigenesis

Prostate cancer patient mortality is ascribed to the spread of cancerous cells to areas outside the prostate gland and the inability of current treatment strategies to effectively block progression to metastasis. Understanding the cellular mechanisms contributing to the dissemination of malignant cells and metastasis is critically significant to the generation of effective therapeutic modalities for improved patient survival while combating therapeutic resistance. In recent years, the phenomenon of epithelial-mesenchymal transitions (EMTs) has received considerable attention due to accumulating evidence indicating a role for this developmentally conserved process in tumorigenesis. Cancer cells at the invasive edges of tumors undergo EMT under the influence of contextual signals that they receive from the microenvironment, such as TGF-β. Also derived from developmental studies is the fact that EMT induction is reversible; thus, upon removal of EMT-inducing signals, cells occasionally revert to the epithelial state of their cellular ancestors via the process of mesenchymal-epithelial transition. This article discusses the current evidence supporting a central role for EMT and its reverse process, mesenchymal-epithelial transition, in the metastatic progression of prostate cancer to advanced disease and the involvement of androgen signaling in its regulation towards the development of castration-resistant prostate cancer.

An EGFR-ERK-SOX9 signaling cascade links urothelial development and regeneration to cancer

Like many carcinomas, urothelial carcinoma (UroCa) is associated with chronic injury. A better understanding of this association could inform improved strategies for preventing and treating this disease. We investigated the expression, regulation, and function of the transcriptional regulator SRY-related high-mobility group box 9 (Sox9) in urothelial development, injury repair, and cancer. In mouse bladders, Sox9 levels were high during periods of prenatal urothelial development and diminished with maturation after birth. In adult urothelial cells, Sox9 was quiescent but was rapidly induced by a variety of injuries, including exposure to the carcinogen cyclophosphamide, culture with hydrogen peroxide, and osmotic stress. Activation of extracellular signal-regulated kinases 1/2 (ERK1/2) was required for Sox9 induction in urothelial injury and resulted from activation of the epidermal growth factor receptor (Egfr) by several Egfr ligands that were dramatically induced by injury. In UroCa cell lines, SOX9 expression was constitutively upregulated and could be suppressed by EGFR or ERK1/2 blockade. Gene knockdown showed a role for SOX9 in cell migration and invasion. Accordingly, SOX9 protein levels were preferentially induced in invasive human UroCa tissue samples (n = 84) compared with noninvasive cancers (n = 56) or benign adjacent urothelium (n = 49). These results identify a novel, potentially oncogenic signaling axis linking urothelial injury to UroCa. Inhibiting this axis is feasible through a variety of pharmacologic approaches and may have clinical utility.

Prognostic significance of cytoplasmic SOX9 in invasive ductal carcinoma and metastatic breast cancer

SOX9, a high mobility group (HMG) box transcription factor, is required for development, differentiation and lineage commitment. It is known to exert its effects through nuclear translocation, such as cell cycle changes in response to retinoic acid treatment in breast cancer cells. However, it is not known whether SOX9 has prognostic significance in human breast cancer. Over-expression and cytoplasmic sequestration of nuclear proteins are implicated in tumor progression. To determine whether SOX9 has any prognostic significance in human breast cancer, its expression and subcellular localization were analyzed in more than 200 human breast carcinomas (BCs). SOX9 mRNA expression data for human BCs were computed from microarray studies available in public databases and correlated with known poor prognostic parameters of BCs. SOX9 protein expression and its correlation with Ki-67 staining in human BCs were assessed using immunohistochemistry. Higher SOX9 mRNA levels were significantly associated with estrogen receptor negative (P ≤ 0.001) and higher grade (P ≤ 0.01) human breast tumors. Patients with higher SOX9 mRNA level had significantly shorter overall survival (P ≤ 0.0001). SOX9 protein, which is normally nuclear, was instead localized in the cytoplasm of 25-30% invasive ductal carcinomas (IDCs) and lymph node metastases. Its cytoplasmic accumulation significantly correlated with enhanced proliferation in breast tumors (Kendall's tau = 0.337 with a P value < 0.0001). Cytoplasmic SOX9 can serve as a valuable prognostic marker for IDCs and metastatic breast cancer. Its significant correlation with breast tumor cell proliferation implies that SOX9 directly contributes to the poor clinical outcomes associated with invasive breast cancer.

Prognostic significance of Sox4 expression in human cutaneous melanoma and its role in cell migration and invasion

The Sox4 transcription factor is involved in various cellular processes, such as embryonic development and differentiation. Deregulated expression of Sox4 in several human cancers has been reported to date, but its role in melanoma is unknown. We explored the role of Sox4 in melanoma pathogenesis in vivo and in vitro. Using tissue microarray, we evaluated Sox4 expression in 180 melanocytic lesions and investigated its role in melanoma cell migration and invasion. Sox4 expression was remarkably reduced in metastatic melanoma compared with dysplastic nevi (P < 0.05) and primary melanoma (P < 0.01). This reduction was correlated with a poorer disease-specific survival of melanoma patients (P = 0.039). Multivariate Cox regression analysis revealed that reduced Sox4 expression is an independent prognostic factor (P = 0.049). Knockdown of Sox4 enhanced melanoma cell invasion, migration, and stress fiber formation. The increased migration and invasion on Sox4 knockdown depends on the presence of nuclear factor (NF)-κB p50 and is abrogated when p50 is knocked down. We further observed inhibition of NF-κB p50 transcription by Sox4, in addition to a reverse pattern of expression of Sox4 and NF-κB p50 in different stages of melanocytic lesions. Our results suggest that Sox4 regulates melanoma cell migration and invasion in an NF-κB p50-dependent manner and may serve as a prognostic marker and potential therapeutic target for human melanoma.

Cancer biomarker discovery: the entropic hallmark

Background

It is a commonly accepted belief that cancer cells modify their transcriptional state during the progression of the disease. We propose that the progression of cancer cells towards malignant phenotypes can be efficiently tracked using high-throughput technologies that follow the gradual changes observed in the gene expression profiles by employing Shannon's mathematical theory of communication. Methods based on Information Theory can then quantify the divergence of cancer cells' transcriptional profiles from those of normally appearing cells of the originating tissues. The relevance of the proposed methods can be evaluated using microarray datasets available in the public domain but the method is in principle applicable to other high-throughput methods.

Methodology/Principal Findings

Using melanoma and prostate cancer datasets we illustrate how it is possible to employ Shannon Entropy and the Jensen-Shannon divergence to trace the transcriptional changes progression of the disease. We establish how the variations of these two measures correlate with established biomarkers of cancer progression. The Information Theory measures allow us to identify novel biomarkers for both progressive and relatively more sudden transcriptional changes leading to malignant phenotypes. At the same time, the methodology was able to validate a large number of genes and processes that seem to be implicated in the progression of melanoma and prostate cancer.

Conclusions/Significance

We thus present a quantitative guiding rule, a new unifying hallmark of cancer: the cancer cell's transcriptome changes lead to measurable observed transitions of Normalized Shannon Entropy values (as measured by high-througput technologies). At the same time, tumor cells increment their divergence from the normal tissue profile increasing their disorder via creation of states that we might not directly measure. This unifying hallmark allows, via the the Jensen-Shannon divergence, to identify the arrow of time of the processes from the gene expression profiles, and helps to map the phenotypical and molecular hallmarks of specific cancer subtypes. The deep mathematical basis of the approach allows us to suggest that this principle is, hopefully, of general applicability for other diseases.

Siah2-dependent concerted activity of HIF and FoxA2 regulates formation of neuroendocrine phenotype and neuroendocrine prostate tumors

Neuroendocrine (NE) phenotype, seen in >30% of prostate adenocarcinomas (PCa), and NE prostate tumors are implicated in aggressive prostate cancer. Formation of NE prostate tumors in the TRAMP mouse model was suppressed in mice lacking the ubiquitin ligase Siah2, which regulates HIF-1alpha availability. Cooperation between HIF-1alpha and FoxA2, a transcription factor expressed in NE tissue, promotes recruitment of p300 to transactivate select HIF-regulated genes, Hes6, Sox9, and Jmjd1a. These HIF-regulated genes are highly expressed in metastatic PCa and required for hypoxia-mediated NE phenotype, metastasis in PCa, and the formation of NE tumors. Tissue-specific expression of FoxA2 combined with Siah2-dependent HIF-1alpha availability enables a transcriptional program required for NE prostate tumor development and NE phenotype in PCa.

Genomic profiling of tumor initiating prostatospheres

Background

The cancer stem cell (CSC) hypothesis proposes that a population of tumor cells bearing stem cell properties is responsible for the origin and maintenance of tumors. Normal and cancer stem cells possess the ability to grow in vitro as self-renewing spheres, but the molecular basis of this phenotype remains largely unknown. We intended to establish a comprehensive culture system to grow prostatospheres (PSs) from both cancer cell lines and patient tumors. We then used gene expression microarrays to gain insight on the molecular pathways that sustain the PS tumor initiating cell (TIC) phenotype.

Results

Traditional stem cell medium (SCM) supplemented with Knockout™SR (KO) allows the propagation of monoclonal PSs from cell lines and primary cells. PSs display gene expression and tumorigenicity hallmarks of TICs. Gene expression analysis defined a gene signature composed of 66 genes that characterize LNCaP and patient PSs. This set includes novel prostate TIC growth factors (NRP1, GDF1, JAG1), proteins implicated in cell adhesion and cytoskeletal maintenance, transcriptional regulators (MYCBP, MYBL1, ID1, ID3, FOS, ELF3, ELF4, KLF2, KLF5) and factors involved in protein biosynthesis and metabolism. Meta-analysis in Oncomine reveals that some of these genes correlate with prostate cancer status and/or progression. Reporter genes and inhibitors indicate that the Notch pathway contributes to prostatosphere growth.

Conclusions

We have developed a model for the culture of PSs, and provide a genomic profile that support CSCs identity. This signature identifies novel markers and pathways that are predicted to correlate with prostate cancer evolution.

Oral administration of the anti-proliferative substance taurolidine has no impact on dextran sulfate sodium induced colitis-associated carcinogenesis in mice

Background:

New chemopreventive strategies for ulcerative colitis (UC)-associated dysplasia and cancer have to be evaluated. Taurolidine (TRD) has anti-inflammatory, anti-proliferative and anti-neoplastic properties with almost absent toxicity. The aim of the study was to determine whether TRD decreases dysplasia in the well-characterized Dextran Sulfate Sodium – Azoxymethane (DSS-AOM) animal model for UC-associated carcinogenesis.

Material and Methods:

The DSS-AOM model of carcinogenesis was induced in female inbred C57BL/6 mice. Half of the mice were treated with TRD, the other served as control. After 100 days macroscopic, histological and immunhistochemical (β-Catenin, E-Cadherin, SOX9, Ki-67, Cyclin-D1) examination of the colon was performed.

Results:

Incidence, multiplicity, grading and growth pattern of adenomas did not differ significantly between TRD and control group. In all animals, inflammatory changes were absent. Immunhistochemistry revealed increased expression of Ki-67, β-catenin, SOX9 and Cyclin-D1 in adenomas compared to normal mucosa – without significant difference between TRD and control treatment.

Conclusion:

Oral administration of TRD has no impact on DSS-induced colitis-associated carcinogenesis. However, SOX9 and Cyclin-D1 representing key members of the Wnt pathway have not yet been described in the DSS-AOM model of carcinogenesis – underlining the importance of this oncogenic pathway in this setting.

SOX9 elevation in the prostate promotes proliferation and cooperates with PTEN loss to drive tumor formation

Dysregulation of tissue development pathways can contribute to cancer initiation and progression. In murine embryonic prostate epithelia, the transcription factor SOX9 is required for proper prostate development. In this study, we examined a role for SOX9 in prostate cancer in mouse and human. In Pten and Nkx3.1 mutant mice, cells with increased levels of SOX9 appeared within prostate epithelia at early stages of neoplasia, and higher expression correlated with progression at all stages of disease. In transgenic mice, SOX9 overexpression in prostate epithelia increased cell proliferation without inducing hyperplasia. In transgenic mice that were also heterozygous for mutant Pten, SOX9 overexpression quickened the induction of high-grade prostate intraepithelial neoplasia. In contrast, Sox9 attenuation led to a decrease proliferating prostate epithelia cells in normal and homozygous Pten mutant mice with prostate neoplasia. Analysis of a cohort of 880 human prostate cancer samples showed that SOX9 expression was associated with increasing Gleason grades and higher Ki67 staining. Our findings identify SOX9 as part of a developmental pathway that is reactivated in prostate neoplasia where it promotes tumor cell proliferation.

Androgen receptor regulates a distinct transcription program in androgen-independent prostate cancer

The evolution of prostate cancer from an androgen-dependent state to one that is androgen-independent marks its lethal progression. The androgen receptor (AR) is essential in both, though its function in androgen-independent cancers is poorly understood. We have defined the direct AR-dependent target genes in both androgen-dependent and -independent cancer cells by generating AR-dependent gene expression profiles and AR cistromes. In contrast to what is found in androgen-dependent cells, AR selectively upregulates M-phase cell-cycle genes in androgen-independent cells, including UBE2C, a gene that inactivates the M-phase checkpoint. We find that epigenetic marks at the UBE2C enhancer, notably histone H3K4 methylation and FoxA1 transcription factor binding, are present in androgen-independent cells and direct AR-enhancer binding and UBE2C activation. Thus, the role of AR in androgen-independent cancer cells is not to direct the androgen-dependent gene expression program without androgen, but rather to execute a distinct program resulting in androgen-independent growth.

Cyclic GMP-dependent protein kinase II inhibits cell proliferation, Sox9 expression and Akt phosphorylation in human glioma cell lines

Earlier we used a glioma model to identify loci in the mouse genome, which were repeatedly targeted by platelet-derived growth factor (PDGF)-containing Moloney murine leukemia viruses. The gene Prkg2, encoding cyclic guanosine monophosphate (cGMP)-dependent protein kinase II, cGKII, was tagged by retroviral insertions in two brain tumors. The insertions were both situated upstream of the kinase domain and suggested creating a truncated form of the cGKII protein. We transfected different human glioma cell lines with Prkg2 and found an overall reduction in colony formation and cell proliferation compared with controls transfected with truncated Prkg2 (lacking the kinase domain) or empty vector. All glioma cells transfected with the cGKII phosphorylate vasodilator-stimulated phosphoprotein, VASP, after cGMP analog treatment. Glioma cell lines positive for the Sox9 transcription factor showed reduced Sox9 expression when Prkg2 was stably transfected. When cGKII was activated by cGMP analog treatment, Sox9 was phosphorylated, Sox9 protein expression was suppressed and the glioma cell lines displayed loss of cell adhesion, inhibition of Akt phosphorylation and G1 arrest. Sox9 repression by siRNA was similarly shown to reduce glioma cell proliferation. Expression analysis of stem and glial lineage cell markers also suggests that cGKII induces differentiation of glioma cell lines. These findings describe an anti-proliferative role of cGKII in human glioma biology and would further explain the retroviral tagging of the cGKII gene during brain tumor formation in PDGF-induced tumors.

The significance of monoamine oxidase-A expression in high grade prostate cancer

PURPOSE

Gleason grade 4/5 prostate cancer is a determinant for recurrence following radical prostatectomy. Monoamine oxidase-A is over expressed in grade 4/5 compared to grade 3 cancer. Monoamine oxidase-A is also expressed by normal basal cells and in vitro studies suggest that its function is to repress secretory differentiation. Therefore, monoamine oxidase-A in grade 4/5 cancer might reflect dedifferentiation to a basal cell-like phenotype. We investigated whether monoamine oxidase-A expression correlates with another basal cell protein, CD44, in high grade cancer and whether either is associated with an aggressive phenotype.

MATERIALS AND METHODS

A total of 133 grade 4/5 archival cancers from a cohort previously used to evaluate the prognostic significance of histomorphological variables were scored for monoamine oxidase-A and CD44 immunohistochemical labeling. Spearman rank correlations of the proteins, and histomorphological and clinical variables were determined. The univariate and multivariate value of each variable as a determinant of biochemical recurrence was assessed by logistic regression.

RESULTS

Monoamine oxidase-A expression correlated with CD44. Neither was prognostic for biochemical recurrence. However, monoamine oxidase-A expression positively correlated with preoperative serum prostate specific antigen and the percent of grade 4/5 cancer.

CONCLUSIONS

Concurrent expression of monoamine oxidase-A and CD44 suggests that grade 4/5 cancer may be basal cell-like in nature, despite the absence of other classic basal cell biomarkers such as cytokeratins 5 and 14, and p63. The correlation of monoamine oxidase-A expression with prostate specific antigen and the percent of grade 4/5 cancer suggests that monoamine oxidase-A may contribute to growth of high grade cancer and that antidepressant drugs that target monoamine oxidase-A may have applications in treating prostate cancer.

Molecular signature and therapeutic perspective of the epithelial-to-mesenchymal transitions in epithelial cancers

The mechanisms involved in the epithelial to mesenchymal transition (EMT) are integrated in concert with master developmental and oncogenic pathways regulating in tumor growth, angiogenesis, metastasis, as well as the reprogrammation of specific gene repertoires ascribed to both epithelial and mesenchymal cells. Consequently, it is not unexpected that EMT has profound impacts on the neoplastic progression, patient survival, as well as the resistance of cancers to therapeutics (taxol, vincristine, oxaliplatin, EGF-R targeted therapy and radiotherapy), independent of the "classical" resistance mechanisms linked to genotoxic drugs. New therapeutic combinations using genotoxic agents and/or EMT signaling inhibitors are therefore expected to circumvent the chemotherapeutic resistance of cancers characterized by transient or sustained EMT signatures. Thus, targeting critical orchestrators at the convergence of several EMT pathways, such as the transcription pathways NF-kappaB, AKT/mTOR axis, MAPK, beta-catenin, PKC and the AP-1/SMAD factors provide a realistic strategy to control EMT and the progression of human epithelial cancers. Several inhibitors targeting these signaling platforms are already tested in preclinical and clinical oncology. In addition, upstream EMT signaling pathways induced by receptor and nonreceptor tyrosine kinases (e.g. EGF-R, IGF-R, VEGF-R, integrins/FAK, Src) and G-protein-coupled receptors (GPCR) constitute practical options under preclinical research, clinical trials or are currently used in the clinic for cancer treatment: e.g. small molecule inhibitors (Iressa: targeting selectively the EGF-R; CP-751,871, AMG479, NVP-AEW541, BMS-536924, PQIP, AG1024: IGF-R; AZD2171, ZD6474: VEGF-R; AZD0530, BMS-354825, SKI606: Src; BIM-46174: GPCR; rapamycin, CCI-779, RAD-001: mTOR) and humanized function blocking antibodies (Herceptin: ErbB2; Avastin: VEGF-A; Erbitux: EGF-R; Abegrin: alphavbeta3 integrins). We can assume that silencing RNA and adenovirus-based gene transfer of therapeutic miR and dominant interferring expression vectors targeting EMT pathways and signaling elements will bring additional ways for the treatment of epithelial cancers. Identification of the factors that initiate, modulate and effectuate EMT signatures and their underlying upstream oncogenic pathways should provide the basis of more efficient strategies to fight cancer progression as well as genetic and epigenetic forms of drug resistance. This goal can be accomplished using global screening of human clinical tumors by EMT-associated cDNA, proteome, miRome, and tissue arrays.