Metastasis suppressor proteins: discovery, molecular mechanisms, and clinical application

Mechanisms of action of NME metastasis suppressors - a family affair

Metastatic progression is regulated by metastasis promoter and suppressor genes. NME1, the prototypic and first described metastasis suppressor gene, encodes a nucleoside diphosphate kinase (NDPK) involved in nucleotide metabolism; two related family members, NME2 and NME4, are also reported as metastasis suppressors. These proteins physically interact with members of the GTPase dynamin family, which have key functions in membrane fission and fusion reactions necessary for endocytosis and mitochondrial dynamics. Evidence supports a model in which NDPKs provide GTP to dynamins to maintain a high local GTP concentration for optimal dynamin function. NME1 and NME2 are cytosolic enzymes that provide GTP to dynamins at the plasma membrane, which drive endocytosis, suggesting that these NMEs are necessary to attenuate signaling by receptors on the cell surface. Disruption of NDPK activity in NME-deficient tumors may thus drive metastasis by prolonging signaling. NME4 is a mitochondrial enzyme that interacts with the dynamin OPA1 at the mitochondria inner membrane to drive inner membrane fusion and maintain a fused mitochondrial network. This function is consistent with the current view that mitochondrial fusion inhibits the metastatic potential of tumor cells whereas mitochondrial fission promotes metastasis progression. The roles of NME family members in dynamin-mediated endocytosis and mitochondrial dynamics and the intimate link between these processes and metastasis provide a new framework to understand the metastasis suppressor functions of NME proteins.

Extracellular Vesicle-Mediated Metastasis Suppressors NME1 and NME2 Modify Lipid Metabolism in Fibroblasts

Simple Summary

Communication between cancer and stromal cells involves paracrine signalling mediated by extracellular vesicles (EVs). EVs transmit essential factors among cells of the tumour microenvironment. EVs derived from both cancer and stromal cells have been implicated in tumour progression. In this study, we focused on the first identified metastasis suppressor NME1, and on its close homolog NME2, and investigated their function in EVs in the interplay between cancer and stromal cells.

Abstract

Nowadays, extracellular vesicles (EVs) raise a great interest as they are implicated in intercellular communication between cancer and stromal cells. Our aim was to understand how vesicular NME1 and NME2 released by breast cancer cells influence the tumour microenvironment. As a model, we used human invasive breast carcinoma cells overexpressing NME1 or NME2, and first analysed in detail the presence of both isoforms in EV subtypes by capillary Western immunoassay (WES) and immunoelectron microscopy. Data obtained by both methods showed that NME1 was present in medium-sized EVs or microvesicles, whereas NME2 was abundant in both microvesicles and small-sized EVs or exosomes. Next, human skin-derived fibroblasts were treated with NME1 or NME2 containing EVs, and subsequently mRNA expression changes in fibroblasts were examined. RNAseq results showed that the expression of fatty acid and cholesterol metabolism-related genes was decreased significantly in response to NME1 or NME2 containing EV treatment. We found that FASN (fatty acid synthase) and ACSS2 (acyl-coenzyme A synthetase short-chain family member 2), related to fatty acid synthesis and oxidation, were underexpressed in NME1/2-EV-treated fibroblasts. Our data show an emerging link between NME-containing EVs and regulation of tumour metabolism.

Small extracellular ring domain is necessary for CD82/KAI1'anti-metastasis function

The peptide mimicking small extracellular loop of CD82/KAI1 has been reported to inhibit tumor cell migration and metastasis. This provides an evidence that small extracellular loop domain should be important for the function of CD82/KAI1. In this paper, to investigate the structure basis for the function of EC1 mimic peptide, we systematically analyzed the effects of each amino acid residue in EC1 mimic peptide on its bioactivity. We found that the interfering with the folding of secondary structure with proline, a potent breaker of secondary structure, completely abolished the migration and metastasis-inhibitory activity of EC1 mimic peptide. This means that the bioactivity of EC1 mimic peptide was conformation-dependent. Next, we substitute with proline for amino acid residues in the small extracellular ring region of CD82/KAI1 by the site-specific mutations to disrupting secondary structure and detected its effect on the function of CD82/KAI1. The results showed that the disturbing the secondary structure of small extracellular ring completely abolished the migration and metastasis-inhibitory activity of CD82/KAI1. These results further provide direct evidence that the small extracellular ring is an important function region of CD82/KAI1.

The peptide mimicking small extracellular ring domain of CD82 inhibits tumor cell migration in vitro and metastasis in vivo

BACKGROUND

Tetraspanin KAI1/CD82, a tumor metastasis suppressor, has emerged as a promising molecular target for the management of metastatic disease. However, the peptide mimicking small extracellular ring domain (EC1) of CD82 has not been fully investigated for the function of inhibiting cell migration in vitro and tumor metastasis in vivo.

METHODS

Different cancer cells were treated with EC1 mimic peptide in order to detect migration and invasion by the healing assay and transwell. Cell aggregation and adhesion assays were used to investigate the function of homotypic cell-cell aggregation and adhesion to tissue culture plates. Then, we established syngeneic and xenograft animal models to assess the metastasis inhibitory effect of EC1 mimic peptide in vivo.

RESULTS

In vitro studies, the EC1 mimic peptide had been showed to promote homotypic cell-cell aggregation, suppress cell migration, invasion and adherence in multiple tumor cell types. In vivo metastasis assays, the EC1 mimic peptide could strongly inhibit the pulmonary metastasis of LCC in syngeneic mice model and SW620 and H1299 in xenograft mice model.

CONCLUSION

This novel finding will improve our understanding of the mechanism by which CD82 inhibits metastasis, and suggests that EC1 mimic peptide may be a promising candidate for developing anti-metastasis drugs.

The isolated C-terminal nuclear localization sequence of the breast cancer metastasis suppressor 1 is disordered

BRMS1 is a 246-residue-long protein belonging to the family of metastasis suppressors. It is a predominantly nuclear protein, although it can also function in the cytoplasm. At its C terminus, it has a region that is predicted to be a nuclear localization sequence (NLS); this region, NLS2, is necessary for metastasis suppression. We have studied in vitro and in silico the conformational preferences in aqueous solution of a peptide (NLS2-pep) that comprises the NLS2 of BRMS1, to test whether it has a preferred conformation that could be responsible for its function. Our spectroscopic (far-UV circular dichroism, DOSY-NMR and 2D-NMR) and computational (all-atom molecular dynamics) results indicate that NLS2-pep was disordered in aqueous solution. Furthermore, it did not acquire a structure even when experiments were performed in a more hydrophobic environment, such as the one provided by 2,2,2-trifluoroethanol (TFE). The hydrodynamic radius of the peptide in water was identical to that of a random-coil sequence, in agreement with both our molecular simulations and other theoretical predictions. Thus, we suggest that NLS2 is a disordered region, with non pre-formed structure, that participates in metastasis suppression.

Prognostic value and clinicopathologic significance of nm23 in various cancers: A systematic review and meta-analysis

OBJECTIVE

Extensive studies have been carried out to investigate the association between nm23 expression and the prognosis and clinicopathologic significance of various tumors.

METHODS AND MATERIALS

Eligible studies were searched from Embase, China National Knowledge Infrastructure (CNKI), PubMed and Web of Science up to May 2017. In this study, we calculated the pooled hazard ratios (HRs) with 95% confidence intervals (95%CIs) to determine the association between nm23 expression and the prognosis of various tumors.

RESULTS

A total of 49 studies were finally included in the meta-analysis. The pooled HRs were 2.00 (95% CIs: 1.44-2.78) for overall survival (OS), 1.23 (95% CIs: 1.04-1.46) for disease-specific survival or progression-free survival (DFS/PFS), and 2.21 (95% CIs: 1.38-3.57) for survival of recurrence-free survival or metastasis-free survival (RFS/MFS). Moreover, the results indicated that low nm23 expression was significantly correlated with the lymph node metastasis (P = 0.002). For the subgroup analysis, the expression of nm23 in patients at N0 stage was obviously higher than the patients with breast carcinoma at N1-N3 stage [Odds ratio (OR) = 2.07, 95%CI (1.31, 3.26), P = 0.002]. Moreover, the expression of nm23 in the patients at N0 stage was remarkably higher than those at N1-N3 stages in the Chinese patients with breast carcinoma and those with nasopharyngeal carcinoma (P < 0.05). Whereas, no statistical difference was noticed in the expression of nm23 in patients of various age, gender, T stage, histological degree, TNM stage, respectively (P > 0.05).

CONCLUSION

Our study suggests that down-regulation of nm23 is related to poor prognosis in many cancers. The expression of nm23 in cancer tissues may serve as an important factor for evaluating the presence of lymph node metastasis.

10 Year Biochemical Failure Free Survival of Men with CD82 Positive Primary Circulating Prostate Cells Treated by Radical Prostatectomy

Objective:

The biological characteristics of circulating prostate cells (CPCs) are probably more important than their mere presence. CD82 is a tumor suppressor, we present the outcome of radical prostatectomy (RP) in men with CD82 positive CPCs.

Methods and Patients:

consecutive men treated with RP were studied, age, total PSA, Gleason, stage, the presence of extra-capsular extension, positive surgical margens and infiltration of the seminal vesicles and lymph nodes were registered. Biochemical failure was defined as a PSA >0.2ng/ml. Immediately before the RP, 8ml of venous blood was taken to detect CPCs. Mononuclear cells were separated using differential gel centrifugation and CPCs identified using immunocytochemistry with anti-PSA and anti-CD82. The men were divided into three groups; 1) CPC (-), 2) CPC (+) CD82 (+) and 3) CPC (+) CD82 (-). The groups were compared with respect to clinical-pathological findings and biochemical free survival using Kaplan Meier and Cox regression models.

Results:

285 men, mean age 65.9 years participated, 61 (21%) were CPC (-); 57 (20%) were CPC (+) CD82 (+) and 167 (59%) were CPC (+) CD82 (-). Group 1 had low grade small volume cancer, in Group 2, low grade but a larger volume than Group 1 and Group 3 high grade cancer. Kaplan Meier biochemical free survival curves at 36, 60 and 120 months were; Group 1 98%, 96% and 90%; for Group 2 93%, 93% and 69% and for Group 3 62%, 44% and 16% respectively.

Conclusions:

Kaplan Meier survival curves for Group 1 and Group 2 were similar, although Group 2 men had higher PSA values, more advanced staging but a similar Gleason score. Group 3 men had a worse prognosis. The results support that biological characteristics of CPCs are more important than their mere presence identifying men with a high risk of biochemical failure.

Inhibition of cell-adhesion protein DPYSL3 promotes metastasis of lung cancer

BACKGROUND

Our previous screening study suggested that the cell-adhesions protein Dihydropyrimidinase-like 3 (DPYSL3) was a candidate metastatic lung cancer related molecule. This study aimed to analyze the correlation between DPYSL3 and metastatic lung cancer.

METHODS

Stable DPYSL3 knockdown Lewis lung carcinoma (LLC) cells were constructed with a retroviral system. Cell migration and invasion assays were performed to determine the role of DPYSL3 in LLC cells' migration and invasion changes. A metastatic lung tumor model in which the stable DPYSL3 knockdown LLC cells were injected through tail vein was used to analyze the role of DPYSL3 in tumor metastasis in vivo. The correlation between DPYSL3 expression and the survival time of lung cancer patients were analyzed in KMPLOT database.

RESULTS

Knockdown of DPYSL3 promoted the migratory and invasive of LLC cells compared to the control group. Meanwhile, the motility of LLC cells was also increased with the inhibition of DPYSL3. The TGFβ-induced EMT increased when DPYSL3 was inhibited. The expression of EMT markers, TWIST1 and N-cadherin, significantly increased to almost two times with the knockdown of DPYSL3. Furthermore, inhibition of DPYSL3 promoted the progression of metastatic xenograft in C57BL/6 mice. The expression level of DPYSL3 decreased in lung cancer patients with distant metastasis.

CONCLUSIONS

Knockdown of DPYSL3 promoted the metastatic ability of LLC cells in vitro and in vivo.

The NDPK/NME superfamily: state of the art

Nucleoside diphosphate kinases (NDPK) are nucleotide metabolism enzymes encoded by NME genes (also called NM23). Given the fact that not all NME-encoded proteins are catalytically active NDPKs and that NM23 generally refers to clinical studies on metastasis, we use here NME/NDPK to denote the proteins. Since their discovery in the 1950's, NMEs/NDPKs have been shown to be involved in multiple physiological and pathological cellular processes, but the molecular mechanisms have not been fully determined. Recent progress in elucidating these underlying mechanisms has been presented by experts in the field at the 10th International Congress on the NDPK/NME/AWD protein family in October 2016 in Dubrovnik, Croatia, and is summarized in review articles or original research in this and an upcoming issue of Laboratory Investigation. Within this editorial, we discuss three major cellular processes that involve members of the multi-functional NME/NDPK family: (i) cancer and metastasis dissemination, (ii) membrane remodeling and nucleotide channeling, and iii) protein histidine phosphorylation.

RCAN1-4 is a thyroid cancer growth and metastasis suppressor

Metastasis suppressors are key regulators of tumor growth, invasion, and metastases. Loss of metastasis suppressors has been associated with aggressive tumor behaviors and metastatic progression. We previously showed that regulator of calcineurin 1, isoform 4 (RCAN1-4) was upregulated by the KiSS1 metastatic suppression pathway and could inhibit cell motility when overexpressed in cancer cells. To test the effects of endogenous RCAN1-4 loss on thyroid cancer in vivo, we developed RCAN1-4 knockdown stable cells. Subcutaneous xenograft models demonstrated that RCAN1-4 knockdown promotes tumor growth. Intravenous metastasis models demonstrated that RCAN1-4 loss promotes tumor metastases to the lungs and their subsequent growth. Finally, stable induction of RCAN1-4 expression reduced thyroid cancer cell growth and invasion. Microarray analysis predicted that nuclear factor, erythroid 2-like 3 (NFE2L3) was a pivotal downstream effector of RCAN1-4. NFE2L3 overexpression was shown to be necessary for RCAN1-4-mediated enhanced growth and invasiveness and NEF2L3 overexpression independently increased cell invasion. In human samples, NFE2L3 was overexpressed in TCGA thyroid cancer samples versus normal tissues and NFE2L3 overexpression was demonstrated in distant metastasis samples from thyroid cancer patients. In conclusion, we provide the first evidence to our knowledge that RCAN1-4 is a growth and metastasis suppressor in vivo and that it functions in part through NFE2L3.

The role and potential mechanisms of LncRNA-TATDN1 on metastasis and invasion of non-small cell lung cancer

The invasion and metastasis of malignant tumor cells lead to normal tissue destruction and are major prognostic factors for many malignant cancers. Long non-coding RNA (LncRNA) is associated with occurrence, development and prognoses of non-small cell lung cancer (NSCLC), but its mechanisms of action involved in tumor invasion and metastasis are not clear. In this study, we screened and detected the expression of LncRNA in two NSCLC lines 95D and 95C by using high throughput LncRNA chip. We found that TATDN1 (Homo sapiens TatD DNase domain containing 1, TATDN1), one of LncRNAs, was highly expressed in 95D cells and NSCLC tumor tissues compared to 95C cells. Knockdown of TATDN1–1 by shRNA significantly inhibited cell proliferation, adhesion, migration and invasion in 95D cells. Further mechanism study showed that TATDN1 knockdown suppressed the expression of E-cadherin, HER2, β-catenin and Ezrin. Moreover, knockdown TATDN1 also inhibited tumor growth and metastasis in a 95D mouse model in vivo by inhibiting β-catenin and Ezrin. These data indicate that TATDN1 expression is associated with 95D cells' higher potential of invasion and metastasis, and suggest that TATDN1 may be a potential prognostic factor and therapeutic target for NSCLCs.

Metastasis suppressor proteins in cutaneous squamous cell carcinoma

Cutaneous squamous cell carcinomas (cSCCs) are common human carcinomas. Despite having metastasizing capacities, they usually show less aggressive progression compared to squamous cell carcinoma (SCC) of other organs. Metastasis suppressor proteins (MSPs) are a group of proteins that control and slow-down the metastatic process. In this study, we established the importance of seven well-defined MSPs including NDRG1, NM23-H1, RhoGDI2, E-cadherin, CD82/KAI1, MKK4, and AKAP12 in cSCCs. Protein expression levels of the selected MSPs were detected in 32 cSCCs, 6 in situ SCCs, and two skin cell lines (HaCaT, A-431) by immunohistochemistry. The results were evaluated semi-quantitatively using the HSCORE system. In addition, mRNA expression levels were detected by qRT-PCR in the cell lines. The HSCOREs of NM23-H1 were similar in cSCCs and normal skin tissues, while RGHOGDI2, E-cadherin and AKAP12 were significantly downregulated in cSCCs compared to normal skin. The levels of MKK4, NDRG1 and CD82 were partially conserved in cSCCs. In stage I SCCs, nuclear staining of NM23-H1 (NM23-H1nuc) was significantly lower than in stage II/III SCCs. Only nuclear staining of MKK4 (MKK4nuc) showed significantly higher scores in in situ carcinomas compared to invasive SCCs. In conclusion, similar to other human tumors, we have demonstrated complex differential expression patterns for the MSPs in in-situ and invasive cSCCs. This complex MSP signature warrants further biological and experimental pathway research.

Simultaneous topographic and recognition imaging of epidermal growth factor receptor (EGFR) on single human breast cancer cells

Epidermal growth factor receptor (EGFR) plays an important role in signaling pathway of the development of breast cancer cells. Since EGFR overexpresses in most breast cancer cells, it is regarded as a biomarker molecule of breast cancer cells. Here we demonstrated a new AFM technique-topography and recognition (TREC) imaging-to simultaneously obtain highly sensitive and specific molecular recognition images and high-resolution topographic images of EGFR on single breast cancer cells.

A novel genome-wide in vivo screen for metastatic suppressors in human colon cancer identifies the positive WNT-TCF pathway modulators TMED3 and SOX12

The progression of tumors to the metastatic state involves the loss of metastatic suppressor functions. Finding these, however, is difficult as in vitro assays do not fully predict metastatic behavior, and the majority of studies have used cloned cell lines, which do not reflect primary tumor heterogeneity. Here, we have designed a novel genome-wide screen to identify metastatic suppressors using primary human tumor cells in mice, which allows saturation screens. Using this unbiased approach, we have tested the hypothesis that endogenous colon cancer metastatic suppressors affect WNT-TCF signaling. Our screen has identified two novel metastatic suppressors: TMED3 and SOX12, the knockdown of which increases metastatic growth after direct seeding. Moreover, both modify the type of self-renewing spheroids, but only knockdown of TMED3 also induces spheroid cell spreading and lung metastases from a subcutaneous xenograft. Importantly, whereas TMED3 and SOX12 belong to different families involved in protein secretion and transcriptional regulation, both promote endogenous WNT-TCF activity. Treatments for advanced or metastatic colon cancer may thus not benefit from WNT blockers, and these may promote a worse outcome.

Non-metastatic 2 (NME2)-mediated suppression of lung cancer metastasis involves transcriptional regulation of key cell adhesion factor vinculin

Tumor metastasis refers to spread of a tumor from site of its origin to distant organs and causes majority of cancer deaths. Although >30 metastasis suppressor genes (MSGs) that negatively regulate metastasis have been identified so far, two issues are poorly understood: first, which MSGs oppose metastasis in a tumor type, and second, which molecular function of MSG controls metastasis. Herein, integrative analyses of tumor-transcriptomes (n = 382), survival data (n = 530) and lymph node metastases (n = 100) in lung cancer patients identified non-metastatic 2 (NME2) as a key MSG from a pool of >30 metastasis suppressors. Subsequently, we generated a promoter-wide binding map for NME2 using chromatin immunoprecipitation with promoter microarrays (ChIP-chip), and transcriptome profiling. We discovered novel targets of NME2 which are involved in focal adhesion signaling. Importantly, we detected binding of NME2 in promoter of focal adhesion factor, vinculin. Reduced expression of NME2 led to enhanced transcription of vinculin. In comparison, NME1, a close homolog of NME2, did not bind to vinculin promoter nor regulate its expression. In line, enhanced metastasis of NME2-depleted lung cancer cells was found in zebrafish and nude mice tumor models. The metastatic potential of NME2-depleted cells was remarkably diminished upon selective RNA-i-mediated silencing of vinculin. Together, we demonstrate that reduced NME2 levels lead to transcriptional de-repression of vinculin and regulate lung cancer metastasis.

Regulation of the metastasis suppressor Nm23-H1 by tumor viruses

Metastasis is the most common cause of cancer mortality. To increase the survival of patients, it is necessary to develop more effective methods for treating as well as preventing metastatic diseases. Recent advancement of knowledge in cancer metastasis provides the basis for development of targeted molecular therapeutics aimed at the tumor cell or its interaction with the host microenvironment. Metastasis suppressor genes (MSGs) are promising targets for inhibition of the metastasis process. During the past decade, functional significance of these genes, their regulatory pathways, and related downstream effector molecules have become a major focus of cancer research. Nm23-H1, first in the family of Nm23 human homologues, is a well-characterized, anti-metastatic factor linked with a large number of human malignancies. Mounting evidence to date suggests an important role for Nm23-H1 in reducing virus-induced tumor cell motility and migration. A detailed understanding of the molecular association between oncogenic viral antigens with Nm23-H1 may reveal the underlying mechanisms for tumor virus-associated malignancies. In this review, we will focus on the recent advances to our understanding of the molecular basis of oncogenic virus-induced progression of tumor metastasis by deregulation of Nm23-H1.

Cooperation of tyrosine kinase receptor TrkB and epidermal growth factor receptor signaling enhances migration and dispersal of lung tumor cells

TrkB mediates the effects of brain-derived neurotrophic factor (BDNF) in neuronal and nonnneuronal cells. Based on recent reports that TrkB can also be transactivated through epidermal growth-factor receptor (EGFR) signaling and thus regulates migration of early neurons, we investigated the role of TrkB in migration of lung tumor cells. Early metastasis remains a major challenge in the clinical management of non-small cell lung cancer (NSCLC). TrkB receptor signaling is associated with metastasis and poor patient prognosis in NSCLC. Expression of this receptor in A549 cells and in another adenocarcinoma cell line, NCI-H441, promoted enhanced migratory capacity in wound healing assays in the presence of the TrkB ligand BDNF. Furthermore, TrkB expression in A549 cells potentiated the stimulatory effect of EGF in wound healing and in Boyden chamber migration experiments. Consistent with a potential loss of cell polarity upon TrkB expression, cell dispersal and de-clustering was induced in A549 cells independently of exogeneous BDNF. Morphological transformation involved extensive cytoskeletal changes, reduced E-cadherin expression and suppression of E-cadherin expression on the cell surface in TrkB expressing tumor cells. This function depended on MEK and Akt kinase activity but was independent of Src. These data indicate that TrkB expression in lung adenoma cells is an early step in tumor cell dissemination, and thus could represent a target for therapy development.

Associations of nm23H1, VEGF-C, and VEGF-3 receptor in human prostate cancer

We studied the expression of the non-metastatic clone 23 type 1 (nm23H1) gene, vascular endothelial growth factor (VEGF)-C, and its receptor VEGFR-3 using an in situ hybridization technique and immunohistochemical analyses with prostate cancer tissues and adjacent benign tissues of 52 human archival cases. The association between VEGF-C expression, microlymphatic count (MLC), and staining intensity for nm23H1 and VEGFR-3 was used to evaluate tumor metastasis and survival rate. MLC values were significantly higher in tumorous tissue than in non-cancerous tissue. VEGF-C mRNA, VEGFR-3, and nm23H1 were highly expressed in tumorous tissue. VEGFR-3 expression was greater in VEGF-C mRNA-positive tumors than in VEGF-C mRNA-negative tumors. The association of VEGFR-3 expression with VEGF-C mRNA and MLC suggested that the poor prognosis and tumor metastasis associated with VEGFR-3 expression may be due, in part, to its role in promoting angiogenesis. VEGF-C expression was significantly associated with tumor lymphangiogenesis, angiogenesis, and immune response as a potent multifunctional stimulating factor in prostate cancer. Expression of nm23H1 was significantly inversely correlated with lymph node metastasis. Furthermore, there was a strong negative correlation between the expression of nm23H1, VEGF-C mRNA, and MLC. These findings provide important information for prophylactic, diagnostic, and therapeutic strategies for prostate cancer.

Prognostic Significance of β-Catenin, E-Cadherin, and SOX9 in Colorectal Cancer: Results from a Large Population-Representative Series

Robust biomarkers that can precisely stratify patients according to treatment needs are in great demand. The literature is inconclusive for most reported prognostic markers for colorectal cancer (CRC). Hence, adequately reported studies in large representative series are necessary to determine their clinical potential. We investigated the prognostic value of three Wnt signaling-associated proteins, β-catenin, E-cadherin, and SOX9, in a population-representative single-hospital series of 1290 Norwegian CRC patients by performing immunohistochemical analyses of each marker using the tissue microarray technology. Loss of membranous or cytosolic β-catenin and loss of cytosolic E-cadherin protein expression were significantly associated with reduced 5-year survival in 903 patients who underwent major resection (722 evaluable tissue cores) independently of standard clinicopathological high-risk parameters. Pre-specified subgroup analyses demonstrated particular effect for stage IV patients for β-catenin membrane staining (P = 0.018; formal interaction test P = 0.025). Among those who underwent complete resection (714 patients, 568 evaluable), 5-year time-to-recurrence analyses were performed, and stage II patients with loss of cytosolic E-cadherin were identified as an independent high-risk subgroup (P = 0.020, formal interaction test was not significant). Nuclear β-catenin and SOX9 protein, regardless of intracellular location, were not associated with prognosis. In conclusion, the protein expression level of membranous or cytosolic β-catenin and E-cadherin predicts CRC patient subgroups with inferior prognosis.

Nm23-h1 binds to gelsolin and inactivates its actin-severing capacity to promote tumor cell motility and metastasis

Nm23-H1 has been identified as a metastasis suppressor gene, but its protein interactions have yet to be understood with any mechanistic clarity. In this study, we evaluated the proteomic spectrum of interactions made by Nm23-H1 in 4T1 murine breast cancer cells derived from tissue culture, primary mammary tumors, and pulmonary metastases. By this approach, we identified the actin-severing protein Gelsolin as binding partner for Nm23-H1, verifying their interaction by coimmunoprecipitation in 4T1 cells as well as in human MCF7, MDA-MB-231T, and MDA-MB-435 breast cancer cells. In Gelsolin-transfected cells, coexpression of Nm23-H1 abrogated the actin-severing activity of Gelsolin. Conversely, actin severing by Gelsolin was abrogated by RNA interference-mediated silencing of endogenous Nm23-H1. Tumor cell motility was negatively affected in parallel with Gelsolin activity, suggesting that Nm23-H1 binding inactivated the actin-depolymerizing function of Gelsolin to inhibit cell motility. Using indirect immunoflourescence to monitor complexes formed by Gelsolin and Nm23-H1 in living cells, we observed their colocalization in a perinuclear cytoplasmic compartment that was associated with the presence of disrupted actin stress fibers. In vivo analyses revealed that Gelsolin overexpression increased the metastasis of orthotopically implanted 4T1 or tail vein-injected MDA-MB-231T cells (P = 0.001 and 0.04, respectively), along with the proportion of mice with diffuse liver metastases, an effect ablated by coexpression of Nm23-H1. We observed no variation in proliferation among lung metastases. Our findings suggest a new actin-based mechanism that can suppress tumor metastasis.

Nm23-h1 binds to gelsolin and inactivates its actin-severing capacity to promote tumor cell motility and metastasis

Nm23-H1 has been identified as a metastasis suppressor gene, but its protein interactions have yet to be understood with any mechanistic clarity. In this study, we evaluated the proteomic spectrum of interactions made by Nm23-H1 in 4T1 murine breast cancer cells derived from tissue culture, primary mammary tumors, and pulmonary metastases. By this approach, we identified the actin-severing protein Gelsolin as binding partner for Nm23-H1, verifying their interaction by coimmunoprecipitation in 4T1 cells as well as in human MCF7, MDA-MB-231T, and MDA-MB-435 breast cancer cells. In Gelsolin-transfected cells, coexpression of Nm23-H1 abrogated the actin-severing activity of Gelsolin. Conversely, actin severing by Gelsolin was abrogated by RNA interference-mediated silencing of endogenous Nm23-H1. Tumor cell motility was negatively affected in parallel with Gelsolin activity, suggesting that Nm23-H1 binding inactivated the actin-depolymerizing function of Gelsolin to inhibit cell motility. Using indirect immunoflourescence to monitor complexes formed by Gelsolin and Nm23-H1 in living cells, we observed their colocalization in a perinuclear cytoplasmic compartment that was associated with the presence of disrupted actin stress fibers. In vivo analyses revealed that Gelsolin overexpression increased the metastasis of orthotopically implanted 4T1 or tail vein-injected MDA-MB-231T cells (P = 0.001 and 0.04, respectively), along with the proportion of mice with diffuse liver metastases, an effect ablated by coexpression of Nm23-H1. We observed no variation in proliferation among lung metastases. Our findings suggest a new actin-based mechanism that can suppress tumor metastasis.

Loss of the metastasis suppressor gene KiSS1 is associated with lymph node metastasis and poor prognosis in human colorectal cancer

Cancer research is currently focused on blocking the metastatic process at its early steps. Some particularly attractive targets are metastasis suppressor genes, which control cancer cell dissemination. The aim of this study was to clarify the relationship between the expression of KiSS1, a metastasis suppressor gene, and disease progression in colorectal cancer patients. One-hundred and seventy-five patients who underwent surgery for colorectal cancer were enrolled in this study. We analyzed KiSS1 mRNA expression by real-time reverse transcription PCR in colorectal cancer tissue and paired adjacent normal mucosa. KiSS1 protein expression in early- and advanced-stage colorectal cancer samples was determined by immunohistochemical analysis. Decreased KiSS1 expression was significantly associated with lymph node metastasis and was an independent prognostic factor. Logistic regression analysis revealed that decreased KiSS1 expression was an independent risk factor for lymph node metastasis. Immunohistochemical analysis indicated that KiSS1 was highly expressed in the cell cytoplasm of early-stage colorectal cancer cells. The loss of KiSS1 appears to correlate with the progression of lymph node metastasis. An assessment of KiSS1 expression may assist in the accurate colorectal cancer diagnosis and may contribute to predict clinical outcomes.

MDM2 binding protein, a novel metastasis suppressor

MDM2 binding protein (MTBP) is a protein that interacts with oncoprotein murine double minute (MDM2), a major inhibitor of the tumor suppressor p53. Overexpression of MTBP leads to p53-independent cell proliferation arrest, which is in turn blocked by simultaneous overexpression of MDM2. Importantly, reduced expression of MTBP in mice increases tumor metastasis and enhances migratory potential of mouse embryonic fibroblasts regardless of the presence of p53. Clinically, loss of MTBP expression in head and neck squamous cell carcinoma is associated with reduced patient survival, and is shown to serve as an independent prognostic factor when p53 is mutated in tumors. These results indicate the involvement of MTBP in suppressing tumor progression. Our recent findings demonstrate that overexpression of MTBP in human osteosarcoma cells lacking wild-type p53 inhibits metastasis, but not primary tumor growth, when cells are transplanted in femurs of immunocompromised mice. These data indicate that MTBP functions as a metastasis suppressor independent of p53 status. Furthermore, overexpression of MTBP suppresses cell migration and filopodia formation, in part, by inhibiting function of an actin crosslinking protein α-actinin-4. Thus, increasing evidence indicates the significance of MTBP in tumor progression. We summarize published results related to MTBP function and discuss caveats and future directions in this review article.

Suppression of tumor and metastasis progression through the scaffolding functions of SSeCKS/Gravin/AKAP12

Scaffolding proteins such as SSeCKS/Gravin/AKAP12 ("AKAP12") are thought to control oncogenic signaling pathways by regulating key mediators in a spatiotemporal manner. The downregulation of AKAP12 in many human cancers, often associated with promoter hypermethylation, or the loss of its locus at 6q24-25.2, correlates with progression to malignancy and metastasis. The forced re-expression of AKAP12 in cancer cell lines suppresses in vitro parameters of oncogenic growth, invasiveness, and cell motility through its ability to scaffold protein kinase C (PKC), F-actin, cyclins, Src, and phosphoinositides, and possibly through additional scaffolding domains for PKA, calmodulin, β1,4-galactosyltransferase-polypeptide-1, β2-adrenergic receptors, and cAMP-specific 3',5'-cyclic phosphodiesterase 4D. Moreover, AKAP12 re-expression in tumor models results in metastasis suppression through the inhibition of Src-regulated, VEGF-mediated neovascularization at distal sites. The current review will describe the emerging understanding of how AKAP12 regulates cellular senescence and oncogenic progression at the level of tumor cells and tumor-associated microenvironment via its multiple scaffolding functions.

Nm23-H1 nuclear expression is associated with a more favourable prognosis in laryngeal carcinoma: univariate and multivariate analysis

AIMS

To use image analysis and multivariate analysis to investigate the prognostic significance of Nm23-H1 subcellular localization in a large cohort of laryngeal squamous cell carcinomas (LSCCs).

METHODS AND RESULTS

Nm23-H1 total and nuclear levels were immunohistochemically determined and calculated with an image analysis system in 104 consecutively operated LSCCs. The mean follow-up was 58.3 ± 35.1 months (median 45 months). Total Nm23-H1 levels correlated only with patient stratification by pT (P=0.01). Mean nuclear Nm23-H1 levels were lower in patients with recurrent disease (P=0.01), and disease-free survival (DFS) was longer in patients whose nuclear levels of Nm23-H1 were >2.0% than in those with levels ≤ 2.0% (P=0.019). On multivariate analysis, Nm23-H1 nuclear expression [hazard ratio (HR) 2.59, P=0.005] and N stage (HR 3.60, P=0.0001) were prognostically significant in relation to DFS.

CONCLUSIONS

In LSCC, Nm23-H1 nuclear expression may be useful for identifying patients at higher risk of recurrence after treatment and who might be considered for more aggressive therapy. Further investigations are needed before Nm23-H1 can be considered for use in targeted treatments for LSCC.

Effect of inhibition of the lysophosphatidic acid receptor 1 on metastasis and metastatic dormancy in breast cancer

BACKGROUND

Previous studies identified the human nonmetastatic gene 23 (NME1, hereafter Nm23-H1) as the first metastasis suppressor gene. An inverse relationship between Nm23-H1 and expression of lysophosphatidic acid receptor 1 gene (LPAR1, also known as EDG2 or hereafter LPA1) has also been reported. However, the effects of LPA1 inhibition on primary tumor size, metastasis, and metastatic dormancy have not been investigated.

METHODS

The LPA1 inhibitor Debio-0719 or LPA1 short hairpinned RNA (shRNA) was used. Primary tumor size and metastasis were investigated using the 4T1 spontaneous metastasis mouse model and the MDA-MB-231T experimental metastasis mouse model (n = 13 mice per group). Proliferation and p38 intracellular signaling in tumors and cell lines were determined by immunohistochemistry and western blot to investigate the effects of LPA1 inhibition on metastatic dormancy. An analysis of variance-based two-tailed t test was used to determine a statistically significant difference between treatment groups.

RESULTS

In the 4T1 spontaneous metastasis mouse model, Debio-0719 inhibited the metastasis of 4T1 cells to the liver (mean = 25.2 liver metastases per histologic section for vehicle-treated mice vs 6.8 for Debio-0719-treated mice, 73.0% reduction, P < .001) and lungs (mean = 6.37 lesions per histologic section for vehicle-treated mice vs 0.73 for Debio-0719-treated mice, 88.5% reduction, P < .001), with no effect on primary tumor size. Similar results were observed using the MDA-MB-231T experimental pulmonary metastasis mouse model. LPA1 shRNA also inhibited metastasis but did not affect primary tumor size. In 4T1 metastases, but not primary tumors, expression of the proliferative markers Ki67 and pErk was reduced by Debio-0719, and phosphorylation of the p38 stress kinase was increased, indicative of metastatic dormancy.

CONCLUSION

The data identify Debio-0719 as a drug candidate with metastasis suppressor activity, inducing dormancy at secondary tumor sites.

The rationale for targeting the LOX family in cancer

The therapeutic targeting of extracellular proteins is becoming hugely attractive in light of evidence implicating the tumour microenvironment as pivotal in all aspects of tumour initiation and progression. Members of the lysyl oxidase (LOX) family of proteins are secreted by tumours and are the subject of much effort to understand their roles in cancer. In this Review we discuss the roles of members of this family in the remodelling of the tumour microenvironment and their paradoxical roles in tumorigenesis and metastasis. We also discuss how targeting this family of proteins might lead to a new avenue of cancer therapeutics.

Metastasis suppressor NM23-H1 promotes repair of UV-induced DNA damage and suppresses UV-induced melanomagenesis

Reduced expression of the metastasis suppressor NM23-H1 is associated with aggressive forms of multiple cancers. Here, we establish that NM23-H1 (termed H1 isoform in human, M1 in mouse) and two of its attendant enzymatic activities, the 3'-5' exonuclease and nucleoside diphosphate kinase, are novel participants in the cellular response to UV radiation (UVR)-induced DNA damage. NM23-H1 deficiency compromised the kinetics of repair for total DNA polymerase-blocking lesions and nucleotide excision repair of (6-4) photoproducts in vitro. Kinase activity of NM23-H1 was critical for rapid repair of both polychromatic UVB/UVA-induced (290-400 nm) and UVC-induced (254 nm) DNA damage, whereas its 3'-5' exonuclease activity was dominant in the suppression of UVR-induced mutagenesis. Consistent with its role in DNA repair, NM23-H1 rapidly translocated to sites of UVR-induced (6-4) photoproduct DNA damage in the nucleus. In addition, transgenic mice hemizygous-null for nm23-m1 and nm23-m2 exhibited UVR-induced melanoma and follicular infundibular cyst formation, and tumor-associated melanocytes displayed invasion into adjacent dermis, consistent with loss of invasion-suppressing activity of NM23 in vivo. Taken together, our data show a critical role for NM23 isoforms in limiting mutagenesis and suppressing UVR-induced melanomagenesis.

Emerging Roles for SSeCKS/Gravin/AKAP12 in the Control of Cell Proliferation, Cancer Malignancy, and Barriergenesis

Emerging data suggest that SSeCKS/Gravin/AKAP12 ("AKAP12"), originally identified as an autoantigen in cases of myasthenia gravis, controls multiple biological processes through its ability to scaffold key signaling proteins such as protein kinase (PK) C and A, calmodulin, cyclins, phosphoinositides, "long" β-1,4 galactosyltransferase (GalTase) isoform, Src, as well as the actin cytoskeleton in a spatiotemporal manner. Specialized functions attributed to AKAP12 include the suppression of cancer malignancy, especially aspects of metastatic progression, regulation of blood-brain and blood-retina barrier formation, and resensitization of β2-adrenergic pain receptors. Recent data identify a direct role for AKAP12 in cytokinesis completion, further suggesting a function as a negative regulator of cell senescence. The current review will discuss the emerging knowledge base of AKAP12-related biological roles and how the factors that affect AKAP12 expression or that interact with AKAP12 at the protein level control cancer progression and blood-tissue barrier formation.

Functional modulation of the metastatic suppressor Nm23-H1 by oncogenic viruses

Evidence over the last two decades from a number of disciplines has solidified some fundamental concepts in metastasis, a major contributor to cancer associated deaths. However, significant advances have been made in controlling this critical cellular process by focusing on targeted therapy. A key set of factors associated with this invasive phenotype is the nm23 family of over twenty metastasis-associated genes. Among the eight known isoforms, Nm23-H1 is the most studied potential anti-metastatic factor associated with human cancers. Importantly, a growing body of work has clearly suggested a critical role for Nm23-H1 in limiting tumor cell motility and progression induced by several tumor viruses, including Epstein-Barr virus (EBV), Kaposi's sarcoma associated herpes virus (KSHV) and human papilloma virus (HPV). A more in depth understanding of the interactions between tumor viruses encoded antigens and Nm23-H1 will facilitate the elucidation of underlying mechanism(s) which contribute to virus-associated cancers. Here, we review recent studies to explore the molecular links between human oncogenic viruses and progression of metastasis, in particular the deregulation of Nm23-H1 mediated suppression.

The structure of BRMS1 nuclear export signal and SNX6 interacting region reveals a hexamer formed by antiparallel coiled coils

We present here the first structural report derived from breast cancer metastasis suppressor 1 (BRMS1), a member of the metastasis suppressor protein group, which, during recent years, have drawn much attention since they suppress metastasis without affecting the growth of the primary tumor. The relevance of the predicted N-terminal coiled coil on the molecular recognition of some of the BRMS1 partners, on its cellular localization and on the role of BRMS1 biological functions such as transcriptional repression prompted us to characterize its three-dimensional structure by X-ray crystallography. The structure of BRMS1 N-terminal region reveals that residues 51-98 form an antiparallel coiled-coil motif and, also, that it has the capability of homo-oligomerizing in a hexameric conformation by forming a trimer of coiled-coil dimers. We have also performed hydrodynamic experiments that strongly supported the prevalence in solution of this quaternary structure for BRMS1(51-98). This work explores the structural features of BRMS1 N-terminal region to help clarify the role of this area in the context of the full-length protein. Our crystallographic and biophysical results suggest that the biological function of BRMS1 may be affected by its ability to promote molecular clustering through its N-terminal coiled-coil region.

Meta-analysis of multiple microarray datasets reveals a common gene signature of metastasis in solid tumors

Background

Metastasis is the number one cause of cancer deaths. Expression microarrays have been widely used to study metastasis in various types of cancer. We hypothesize that a meta-analysis of publicly available gene expression datasets in various tumor types can identify a signature of metastasis that is common to multiple tumor types. This common signature of metastasis may help us to understand the shared steps in the metastatic process and identify useful biomarkers that could predict metastatic risk.

Methods

We identified 18 publicly available gene expression datasets in the Oncomine database comparing distant metastases to primary tumors in various solid tumors which met our eligibility criteria. We performed a meta-analysis using a modified permutation counting method in order to obtain a common gene signature of metastasis. We then validated this signature in independent datasets using gene set expression comparison analysis with the LS-statistic.

Results

A common metastatic signature of 79 genes was identified in the metastatic lesions compared with primaries with a False Discovery Proportion of less than 0.1. Interestingly, all the genes in the signature, except one, were significantly down-regulated, suggesting that overcoming metastatic suppression may be a key feature common to all metastatic tumors. Pathway analysis of the significant genes showed that the genes were involved in known metastasis-associated pathways, such as integrin signaling, calcium signaling, and VEGF signaling. To validate the signature, we used an additional six expression datasets that were not used in the discovery study. Our results showed that the signature was significantly enriched in four validation sets with p-values less than 0.05.

Conclusions

We have modified a previously published meta-analysis method and identified a common metastatic signature by comparing primary tumors versus metastases in various tumor types. This approach, as well as the gene signature identified, provides important insights to the common metastatic process and a foundation for future discoveries that could have broad application, such as drug discovery, metastasis prediction, and mechanistic studies.

Mechanisms of non-metastatic 2 (NME2)-mediated control of metastasis across tumor types

Non-metastatic 23 [NM23/nucleoside diphosphate kinases (NDPK)] genes are the first discovered metastasis suppressor genes. More than two decades of research has demonstrated their roles in a variety of biological processes with NME1 and NME2 being most studied in the context of metastasis suppression. Although NME1 and NME2 share >85% homology at amino acid level, they show redundant as well as unique molecular functions. Phenotypic analyses of knockout (KO) mice for NM23 members (NDPK-A, B) and compound KO (A as well as B) showed requirement of both proteins in hematopoiesis suggesting shared functions in development disease. Several reviews have discussed NME1, however the role of NME2 appears to be relatively less understood in the context of metastasis suppression. Here, we focus on NME2 and by meta-analysis of gene expression from multiple tumor types, and survey of in vivo and vitro studies, suggest the possibility that NME2 may be one of the key factors in metastasis. This along with the relevance of normal physiological functions of NME2 in the context of metastasis is discussed. We further examined the genetic and epigenetic features of NME2 and NME1 gene promoters and found aspects of transcription control that could be unique to NME2/NME1. Findings on signaling pathways and small molecules which regulate the expression of NME2 that could be therapeutically important are also discussed.

Metastasis-suppressor genes in clinical practice: lost in translation?

Over the past 25 years, an expanding set of metastasis-suppressor genes (MSGs) has been identified that specifically regulate metastasis formation without affecting primary growth. MSGs are involved in diverse molecular processes in multiple tumor types. Given the wealth of metastasis biology that underlies their functions, treatment strategies based on MSGs have an unparalleled potential to improve patient care. Using NM23 as a prime example, we discuss how specific MSGs have been used as prognostic markers, tools for predicting response to treatment, and targets for the development of novel therapies. Barriers specific to the translation of MSG biology into clinical practice are reviewed and future research directions necessary for clinical advances are delineated. Although to date the impact of MSGs on patient care is limited, it is an expanding field with vast potential to help develop new treatments and identify patients who will most benefit from them.

Metastasis suppressor genes at the interface between the environment and tumor cell growth

The molecular mechanisms and genetic programs required for cancer metastasis are sometimes overlapping, but components are clearly distinct from those promoting growth of a primary tumor. Every sequential, rate-limiting step in the sequence of events leading to metastasis requires coordinated expression of multiple genes, necessary signaling events, and favorable environmental conditions or the ability to escape negative selection pressures. Metastasis suppressors are molecules that inhibit the process of metastasis without preventing growth of the primary tumor. The cellular processes regulated by metastasis suppressors are diverse and function at every step in the metastatic cascade. As we gain knowledge into the molecular mechanisms of metastasis suppressors and cofactors with which they interact, we learn more about the process, including appreciation that some are potential targets for therapy of metastasis, the most lethal aspect of cancer. Until now, metastasis suppressors have been described largely by their function. With greater appreciation of their biochemical mechanisms of action, the importance of context is increasingly recognized especially since tumor cells exist in myriad microenvironments. In this chapter, we assemble the evidence that selected molecules are indeed suppressors of metastasis, collate the data defining the biochemical mechanisms of action, and glean insights regarding how metastasis suppressors regulate tumor cell communication to-from microenvironments.

Sponge non-metastatic Group I Nme gene/protein - structure and function is conserved from sponges to humans

Background

Nucleoside diphosphate kinases NDPK are evolutionarily conserved enzymes present in Bacteria, Archaea and Eukarya, with human Nme1 the most studied representative of the family and the first identified metastasis suppressor. Sponges (Porifera) are simple metazoans without tissues, closest to the common ancestor of all animals. They changed little during evolution and probably provide the best insight into the metazoan ancestor's genomic features. Recent studies show that sponges have a wide repertoire of genes many of which are involved in diseases in more complex metazoans. The original function of those genes and the way it has evolved in the animal lineage is largely unknown. Here we report new results on the metastasis suppressor gene/protein homolog from the marine sponge Suberites domuncula, NmeGp1Sd. The purpose of this study was to investigate the properties of the sponge Group I Nme gene and protein, and compare it to its human homolog in order to elucidate the evolution of the structure and function of Nme.

Results

We found that sponge genes coding for Group I Nme protein are intron-rich. Furthermore, we discovered that the sponge NmeGp1Sd protein has a similar level of kinase activity as its human homolog Nme1, does not cleave negatively supercoiled DNA and shows nonspecific DNA-binding activity. The sponge NmeGp1Sd forms a hexamer, like human Nme1, and all other eukaryotic Nme proteins. NmeGp1Sd interacts with human Nme1 in human cells and exhibits the same subcellular localization. Stable clones expressing sponge NmeGp1Sd inhibited the migratory potential of CAL 27 cells, as already reported for human Nme1, which suggests that Nme's function in migratory processes was engaged long before the composition of true tissues.

Conclusions

This study suggests that the ancestor of all animals possessed a NmeGp1 protein with properties and functions similar to evolutionarily recent versions of the protein, even before the appearance of true tissues and the origin of tumors and metastasis.

Regulation of Nm23-H1 and cell invasiveness by Kaposi's sarcoma-associated herpesvirus

The Kaposi's sarcoma-associated herpesvirus (KSHV) is the causative agent of Kaposi's sarcoma (KS), and the induction of an invasive cellular phenotype by KSHV following de novo infection is an important pathogenic component mediating tumor progression. The metastasis suppressor gene known as Nm23-H1 regulates tumor cell invasiveness, but whether KSHV itself regulates Nm23-H1 expression or subcellular localization, and whether this impacts cell invasiveness, has not been established. We found that KSHV increases expression and nuclear translocation of Nm23-H1 and that nuclear translocation of Nm23-H1 is regulated by the KSHV-encoded latency-associated nuclear antigen (LANA). Moreover, activation of the Ras-BRaf-MAPK (mitogen-activated protein kinase) signal transduction pathway, secretion of promigratory factors associated with this pathway, and cell invasiveness are dependent on KSHV regulation of Nm23-H1. Finally, induction of cytoplasmic overexpression of Nm23-H1 using a pharmacologic inhibitor of DNA methylation reduced KSHV-associated Ras-BRaf-MAPK pathway activation and suppressed KSHV-induced invasiveness. These data provide the first evidence for KSHV regulation of Nm23-H1 as a mechanism for KSHV induction of an invasive cellular phenotype and support the potential utility of targeting Nm23-H1 as a therapeutic approach for the treatment of KS.

The relationship of palliative transurethral resection of the prostate with disease progression in patients with prostate cancer

OBJECTIVES

To test, in a prostate-cancer population-based database, the validity of the finding that in single-institution series, palliative transurethral resection of prostate (TURP) is associated with an increased risk of progression.

PATIENTS AND METHODS

Using the Surveillance Epidemiology and END Results Registry, we identified men who had a TURP subsequent to their diagnosis of prostate cancer, from 1998 or 1999. The outcome of interest was disease progression, as defined by the initiation of androgen-deprivation therapy or procedures indicating progressive urinary obstruction. Multivariable logistic regression analysis was used to assess the adjusted odds of signal events related to disease progression adjusting for the concurrent effect of the covariates.

RESULTS

There were 29,361 men with prostate cancer and 2742 (9.3%) had a TURP after the diagnosis. These men had a mean age of 75 years and were unlikely to undergo definitive primary treatment. Men receiving TURP were more likely to undergo orchidectomy than men who did not have a TURP (odds ratio 1.64; 95% confidence interval 1.03-2.60) even after adjusting for differences in cancer-directed treatment, tumour stage and grade, prostate-specific antigen level, race, and age at diagnosis. These men were also more likely to have malignant urinary obstruction (ureteric and bladder outlet) than were men who did not have TURP.

CONCLUSION

The requirement for TURP is an adverse prognostic marker even when this is adjusted for classical tumour characteristics. Although the exact reasons for this finding are unclear, consideration should be given to adjuvant treatment in patients undergoing TURP.

Overexpression of KAI1 induces autophagy and increases MiaPaCa-2 cell survival through the phosphorylation of extracellular signal-regulated kinases

KAI1, a metastasis-suppressor gene belonging to the tetraspanin family, is known to inhibit cancer metastasis without affecting the primary tumorigenicity by inhibiting the epidermal growth factor (EGF) signaling pathway. Recent studies have shown that hypoxic conditions of solid tumors induce high-level autophagy and KAI1 expression. However, the relationship between autophagy and KAI1 remains unclear. By using transmission electron microscopy, confocal microscopy, and Western blotting, we found that KAI1 can induce autophagy in a dose- and time-dependent manner in the human pancreatic cell line MiaPaCa-2. KAI1-induced autophagy was confirmed by the expression of autophagy-related proteins LC3 and Beclin 1. KAI1 induces autophagy through phosphorylation of extracellular signal-related kinases rather than that of AKT. KAI1-induced autophagy protects MiaPaCa-2 cells from apoptosis and proliferation inhibition partially through the downregulation of poly [adenosine diphosphate (ADP)-ribose] polymerase (PARP) cleavage and caspase-3 activation.

The α₂β₁ integrin is a metastasis suppressor in mouse models and human cancer

Integrins regulate cell-cell and cell-matrix adhesion and thereby play critical roles in tumor progression and metastasis. Although work in preclinical models suggests that β1 integrins may stimulate metastasis of a number of cancers, expression of the β1 subunit alone has not been shown to be a useful prognostic indicator in human cancer patients. Here we have demonstrated that the α2β1 integrin suppresses metastasis in a clinically relevant spontaneous mouse model of breast cancer. These data are consistent with previous studies indicating high expression of α2β1 integrin in normal breast epithelium and loss of α2β1 in poorly differentiated breast cancer. They are also consistent with our systematic analysis of microarray databases of human breast and prostate cancer, which revealed that decreased expression of the gene encoding α2 integrin, but not genes encoding α1, α3, or β1 integrin, was predictive of metastatic dissemination and decreased survival. The predictive value of α2 expression persisted within both good-risk and poor-risk cohorts defined by estrogen receptor and lymph node status. Thus, the α2β1 integrin functionally inhibits breast tumor metastasis, and α2 expression may serve as an important biomarker of metastatic potential and patient survival.

KISS1 over-expression suppresses metastasis of pancreatic adenocarcinoma in a xenograft mouse model

Identifying molecular targets for treatment of pancreatic cancer metastasis is critical due to the high frequency of dissemination prior to diagnosis of this lethal disease. Because the KISS1 metastasis suppressor is expressed at reduced levels in advanced pancreatic cancer, we hypothesized that re-expression of KISS1 would reduce metastases. Highly metastatic S2VP10 cells expressing luciferase (S2VP10L) were transfected with a FLAG-tagged version of KISS1 (KFM), KFMΔSS (with deleted secretion signal sequence), or pcDNA3 control plasmid (CP) and expression was confirmed by RTQ-PCR. SCID mice were implanted orthotopically with S2VP10L cells or transfectants and tumor growth and metastases were monitored using bioluminescence imaging. Mice with S2VP10L-KISS1 tumors developed fewer liver (98%) and lung (99%) metastases than S2VP10L. Unexpectedly, mice with S2VP10L-KFMΔSS tumors also had reduced liver and lung metastases, but had more metastases than mice with S2VP10L-KISS. KISS1 protein was found in the cytoplasm of both KFMΔSS and KISS1-expressing orthotopic tumors by immunohistochemistry. Metastases were not found in lungs of mice with S2VP10L-KISS1 tumors; whereas, KFMΔSS lung sections had regions of concentrated KISS1 staining, suggesting that secretion of KISS1 is needed to reduce metastasis significantly. These data suggest induction of KISS1 expression has potential as an adjuvant treatment for pancreatic cancer.

Peroxiredoxin 6 interferes with TRAIL-induced death-inducing signaling complex formation by binding to death effector domain caspase

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising cancer therapeutic agent with cancer-selective apoptogenic activity. It evokes the canonical caspase-mediated cell death pathway through death-inducing signaling complex (DISC) formation. We identified that Peroxiredoxin 6 (Prx6) interacts with caspase-10 and caspase-8 via the death effector domain (DED). Prx6 suppresses TRAIL-mediated cell death in human cancer cells, but not that induced by intrinsic apoptosis inducers such as etoposide, staurosporine, or A23187. Among Prx1-6 members, only Prx6 binds to DED caspases and is most effective in suppressing TRAIL or DED caspase-induced cell death. The antiapoptotic activity of Prx6 against TRAIL is not likely associated with its peroxidase activity but is associated with its ability to bind to DED caspases. Increased expression of Prx6 enhances the binding of Prx6 to caspase-10 but reduces TRAIL-induced DISC formation and subsequently caspase activation. Interestingly, Prx6 is highly upregulated in metastatic gastric cancer cells, which are relatively resistant to TRAIL as compared with primary cancer cells. Downregulation of Prx6 sensitizes the metastatic cancer cells to TRAIL-induced cell death. Taken together, these results suggest that Prx6 modulates TRAIL signaling as a negative regulator of caspase-8 and caspase-10 in DISC formation of TRAIL-resistant metastatic cancer cells.

Expression profiling identifies new function of collapsin response mediator protein 4 as a metastasis-suppressor in prostate cancer

Metastasis is the chief cause of mortality from cancer, but the mechanisms leading to metastasis are poorly understood. We used a proteomics approach to screen for metastasis-associated proteins and found that collapsin response mediator protein-4 (CRMP4) expression was inversely associated with the lymph node metastasis of prostate cancer (PCa). Subsequent in vitro and in vivo studies revealed that overexpression of CRMP4 not only suppressed the invasion ability of PCa cells, but also strongly inhibited tumor metastasis in an animal model. Furthermore, methylation of a CpG island within the promoter region of the CRMP4 gene is responsible for downregulation of CRMP4 expression. Thus, in this study, we show new function of CRMP4 as a metastasis-suppressor in PCa. The findings provide new mechanistic insights into metastasis and therapeutic potential for this most common male cancer.

Selection in spatial stochastic models of cancer: migration as a key modulator of fitness

Background

We study the selection dynamics in a heterogeneous spatial colony of cells. We use two spatial generalizations of the Moran process, which include cell divisions, death and migration. In the first model, migration is included explicitly as movement to a proximal location. In the second, migration is implicit, through the varied ability of cell types to place their offspring a distance away, in response to another cell's death.

Results

In both models, we find that migration has a direct positive impact on the ability of a single mutant cell to invade a pre-existing colony. Thus, a decrease in the growth potential can be compensated by an increase in cell migration. We further find that the neutral ridges (the set of all types with the invasion probability equal to that of the host cells) remain invariant under the increase of system size (for large system sizes), thus making the invasion probability a universal characteristic of the cells selection status. We find that repeated instances of large scale cell-death, such as might arise during therapeutic intervention or host response, strongly select for the migratory phenotype.

Conclusions

These models can help explain the many examples in the biological literature, where genes involved in cell's migratory and invasive machinery are also associated with increased cellular fitness, even though there is no known direct effect of these genes on the cellular reproduction. The models can also help to explain how chemotherapy may provide a selection mechanism for highly invasive phenotypes.

Reviewers

This article was reviewed by Marek Kimmel and Glenn Webb.

Disrupting ovarian cancer metastatic colonization: insights from metastasis suppressor studies

Ovarian cancer affects approximately 25,000 women in the United States each year and remains one of the most lethal female malignancies. A standard approach to therapy is surgical cytoreduction, after which the remaining microscopic residual disease is treated with chemotherapy. The vast majority of patients have disease recurrence, underscoring the crucial need for approaches to control the regrowth, or colonization, of tissues after local treatment. Improved therapies require mechanistic information about the process of metastatic colonization, the final step in metastasis, in which cancer cells undergo progressive growth at secondary sites. Studies of metastasis suppressors are providing insights into events controlling metastatic colonization. This paper reviews our laboratory's approach to the identification, characterization, and functional testing of the JNKK1/MKK4 metastasis suppressor in ovarian cancer metastatic colonization. Specifically, we demonstrate that interaction of ovarian caner cells with the omental microenvironment activates JNKK1/MKK4 resulting in decreased proliferation without affecting apoptosis. The potential role of the omental microenvironment, specifically milky spot structures, is also described. It is our goal to provide this work as a usable paradigm that will enable others to study metastasis suppressors in clinical and experimental ovarian cancer metastases.

ErbB3 binding protein 1 represses metastasis-promoting gene anterior gradient protein 2 in prostate cancer

Dysregulation of the developmental gene anterior gradient protein 2 (AGR2) has been associated with a metastatic phenotype, but its mechanism of action and control in prostate cancers is unknown. In this study, we show that overexpression of AGR2 promotes the motility and invasiveness of nonmetastatic LNCaP tumor cells, whereas silencing of AGR2 in the metastatic derivative C4-2B blocks invasive behavior. ErbB3 binding protein 1 (EBP1), a putative repressor of AGR2, is attenuated in prostate cancer. We show that the anti-invasive effect of EBP1 occurs, at least in part, through its ability to inhibit AGR2 expression. Mechanistic investigations indicate that EBP1 downregulates Foxa1- and Foxa2-stimulated AGR2 transcription and decreases metastatic behavior. In contrast, EBP1 ablation upregulates AGR2 via Foxa1- and Foxa2-stimulated AGR2 promoter activity and increases metastatic behavior. In both prostate cell lines and primary tumors, we documented an inverse correlation between EBP1 and AGR2 levels. Collectively, our results reveal an EBP1-Foxa-AGR2 signaling circuit with functional significance in metastatic prostate cancer.