Suppressive subtractive hybridisation reveals differential expression of serglycin, sorcin, bone marrow proteoglycan and prostate-tumour-inducing gene I (PTI-1) in drug-resistant and sensitive tumour cell lines of haematopoetic origin

SRGN crosstalks with YAP to maintain chemoresistance and stemness in breast cancer cells by modulating HDAC2 expression

Background: Chemoresistance is a significant obstacle to the effective treatment of breast cancer (BC), resulting in more aggressive behavior and worse clinical outcome. The molecular mechanisms underlying breast cancer chemoresistance remain unclear. Our microarray analysis had identified the overexpression of a small molecular glycoprotein serglycin (SRGN) in multidrug-resistant BC cells. Here, we aimed to investigate the role of SRGN in chemoresistance of breast cancer and elucidate the underlying mechanisms. Methods: SRNG overexpression was identified using microarray analysis and its clinical relevance was analyzed. To investigate the role of SRGN, we performed various in vitro and in vivo studies, as well as characterization of serum and tissue samples from BC patients. Chemosensitivity measurement, gene expression interference, immunofluorescence staining, mammosphere assay, flow cytometry analysis, luciferase reporter assay, ChIP-qPCR, coimmunoprecipitation, and immunohistochemistry were performed to explore the potential functions and mechanisms of SRGN. Results: We confirmed overexpression of SRGN in chemoresistant BC cells and in serum and tissue samples from BC patients with poor response to chemotherapy. SRGN specifically predicted poor prognosis in BC patients receiving chemotherapy. Mechanistically, SRGN promoted chemoresistance both in vitro and in vivo by cross-talking with the transcriptional coactivator YES-associated protein (YAP) to maintain stemness in BC cells. Ectopic YAP expression restored the effects of SRGN knockdown. Inversely, YAP knockdown rescued the effects of SRGN overexpression. The secreted SRGN triggered ITGA5/FAK/CREB signaling to enhance YAP transcription. Reciprocally, YAP promoted SRGN transcription in a TEAD1-dependent manner to form a feed-forward circuit. Moreover, the YAP/RUNX1 complex promoted HDAC2 transcription to induce chemoresistance and stemness in BC cells. Importantly, the SRGN levels were positively correlated with the YAP and HDAC2 levels in chemoresistant BC tissues. YAP and HDAC2 acted downstream of SRNG and correlated with poor outcomes of BC patients receiving chemotherapy. Conclusions: Our findings clarify the roles and mechanisms of SRGN in mediating chemoresistance in breast cancer and suggest its use a potential biomarker for chemotherapeutic response. We believe that novel therapeutic strategies for breast cancer can be designed by targeting the signaling mediated by the crosstalk between SRGN and YAP.

Sorcin: a novel potential target in therapies of cancers

Soluble resistance-related calcium-binding protein (sorcin) is a member of the penta-EF-hand protein family. Sorcin is widely distributed in normal human tissues, such as the brain, heart, lymphocytes, kidneys, breast and skin. Findings suggest that sorcin is associated with the regulation of calcium homeostasis, cell cycle and vesicle trafficking. It has been reported that many types of non-neoplastic diseases such as diabetes, viral infection, infertility, and nervous system diseases were affected by the expression of sorcin. One of the main issues is the role of sorcin in neoplastic diseases. Research proved that sorcin can be found to overexpress in cells of several cancers, particularly in the case of multidrug-resistant cancers. Additionally, the researchers proposed that the expression of sorcin was significantly associated with the foundation of multidrug resistance (MDR). All the findings mentioned above emphasized the importance of studying sorcin. This review mainly includes the following aspects: functions of sorcin, role in non-neoplastic and neoplastic diseases, and research related to drugs. To sum up, sorcin is a potential novel target to be studied to deal with MDR.

Differential Expression of HSP90β in MDA-MB-231 and MCF-7 Cell Lines after Treatment with Doxorubicin

Background

Breast cancer is a complex, heterogeneous disease and one of the most common malignancies in women worldwide. The efficacy of chemotherapy as an important breast cancer treatment option has been severely limited because of the inherent or acquired resistance of cancer cells. The molecular chaperone heat shock protein 90 (HSP90) upregulated in response to cellular stress is required for functions such as conformational maturation, activation and stability in more than 200 client proteins, mostly of the signaling type. In this study, the expression of HSP90 isoforms including HSP90α and HSP90β in breast cancer cell lines before and after treatment with doxorubicin (DOX) was assessed.

Material and Methods

The cell cytotoxicity of DOX in MDA-MB-231 and MCF-7 cell lines was determined using the MTT assay. Immunofluorescence and western blotting techniques were used to determine the expression of HSP90β in the cell lines before and after DOX treatment. Immunofluorescence was also conducted to ascertain the expression of HSP90α.

Results

The MTT assay results showed that the MDA-MB- 231 cells (IC₅₀=14.521 μM) were more sensitive than the MCF-7 cells (IC₅₀=16.3315 μM) to DOX. The immunofluorescence results indicated that the expression of HSP90α in both cell lines decreased after exposure to DOX. The western blot and immunofluorescence analyses showed that HSP90β expression decreased in the MCF-7 cells but increased in the MDA-MB- 231 cells after DOX treatment. Conclusion: The obtained results suggested that HSP90α and HSP90β expression levels were reduced in the MCF-7 cells after exposure to DOX. In the MDA-MB-231 cells, HSP90α expression was reduced while HSP90β was found to be overexpressed following DOX treatment.

Multiple Roles of Glycans in Hematological Malignancies

The three types of blood cells (red blood cells for carrying oxygen, white blood cells for immune protection, and platelets for wound clotting) arise from hematopoietic stem/progenitor cells in the adult bone marrow, and function in physiological regulation and communication with local microenvironments to maintain systemic homeostasis. Hematological malignancies are relatively uncommon malignant disorders derived from the two major blood cell lineages: myeloid (leukemia) and lymphoid (lymphoma). Malignant clones lose their regulatory mechanisms, resulting in production of a large number of dysfunctional cells and destruction of normal hematopoiesis. Glycans are one of the four major types of essential biological macromolecules, along with nucleic acids, proteins, and lipids. Major glycan subgroups are N-glycans, O-glycans, glycosaminoglycans, and glycosphingolipids. Aberrant expression of glycan structures, resulting from dysregulation of glycan-related genes, is associated with cancer development and progression in terms of cell signaling and communication, tumor cell dissociation and invasion, cell-matrix interactions, tumor angiogenesis, immune modulation, and metastasis formation. Aberrant glycan expression occurs in most hematological malignancies, notably acute myeloid leukemia, myeloproliferative neoplasms, and multiple myeloma, etc. Here, we review recent research advances regarding aberrant glycans, their related genes, and their roles in hematological malignancies. Our improved understanding of the mechanisms that underlie aberrant patterns of glycosylation will lead to development of novel, more effective therapeutic approaches targeted to hematological malignancies.

Extracellular serglycin upregulates the CD44 receptor in an autocrine manner to maintain self-renewal in nasopharyngeal carcinoma cells by reciprocally activating the MAPK/β-catenin axis

Serglycin is a proteoglycan that was first found to be secreted by hematopoietic cells. As an extracellular matrix (ECM) component, serglycin promotes nasopharyngeal carcinoma (NPC) metastasis and serves as an independent, unfavorable NPC prognostic indicator. The detailed mechanism underlying the roles of serglycin in cancer progression remains to be clarified. Here, we report that serglycin knockdown in NPC cells inhibited cell sphere formation and tumor seeding abilities. Serglycin downregulation enhanced high-metastasis NPC cell sensitivity to chemotherapy. It has been reported that serglycin is a novel ligand for the stem cell marker CD44. Interestingly, we found a positive correlation between serglycin expression and CD44 in nasopharyngeal tissues and NPC cell lines. Further study revealed that CD44 was an ERK-dependent downstream effector of serglycin signaling, and serglycin activated the MAPK/β-catenin axis to induce CD44 receptor expression in a positive feedback loop. Taken together, our novel findings suggest that ECM serglycin upregulated CD44 receptor expression to maintain NPC stemness by interacting with CD44 and activating the MAPK/β-catenin pathway, resulting in NPC cell chemoresistance. These findings suggest that the intervention of serglycin/CD44 axis and downstream signaling pathway is a rational strategy for targeting NPC cancer stem cell therapy.

Overexpression of SORCIN is a Prognostic Biomarker for Multidrug-Resistant Pediatric Acute Lymphoblastic Leukemia and Correlates with Upregulated MDR1/P-gp

BACKGROUND

Multidrug resistance is one of the major causes of treatment failure in pediatric acute lymphoblastic leukemia (ALL), and SORCIN is an intracellular calcium modulator protein. The current study was designed to investigate the in vitro and in vivo relationships between the expression levels of SORCIN: in tumor cell lines and children with ALL; its possible correlation with MDR1/P-glycoprotein (P-gp), a multidrug resistance-related gene; and response to therapy.

MATERIALS AND METHODS

Childhood T-lymphoblastic leukemia (CCRF-CEM) cell lines resistant to methotrexate (MTX) were developed. Patient studies were performed by including 30 children with ALL at diagnosis, 3 children with bone marrow relapse, and 15 children with no symptoms of cancer. The mRNA expression profiles of SORCIN and MDR1/P-gp was assessed using quantitative polymerase chain reaction (qPCR). Minimal residual disease (MRD) was measured in the patient population, a year following the initial therapy using qPCR.

RESULTS

Cell line data analyses showed a positive correlation between SORCIN mRNA levels and resistance to MTX. The difference between patient and control groups for SORCIN expression levels was not significant. However, patients with a negative response to therapy showed an increase in SORCIN mRNA levels (up to 6.8-fold) compared with those with negative MRD. In addition, the results demonstrated a significant positive correlation between SORCIN and MDR1/P-gp gene expression levels.

CONCLUSION

The current study introduces, for the first time, a possible prognostic value of SORCIN in childhood ALL, which may be correlated with MDR1/P-gp gene expression in these patients.

Overexpression of sorcin in multidrug-resistant human breast cancer

Sorcin is a soluble resistance-related calcium-binding protein, which is expressed in normal mammalian tissues, such as the liver, lungs and heart. It has been observed to be elevated in a number of cancer types, including colorectal, gastric and breast cancer. Its upregulation is usually associated with the development of chemotherapeutic drug resistance. The aim of this study was to evaluate the sorcin expression levels in human serum samples of breast cancer subjects at various stages, and subsequently compare the outcome of neoadjuvant chemotherapy when the sorcin levels fluctuated. In total, 50 subjects were recruited from patients who were admitted to Yantai Yuhunagding Hospital (Yantai, China) and diagnosed with breast cancer. Blood samples prior to and following chemotherapy were assessed using two-dimensional gel electrophoresis (2-DE) and western blot analysis. The 2-DE analysis of the serum samples revealed that sorcin was upregulated in six out of 29 neoadjuvant chemotherapy (NAC)-sensitive patients and, in those who developed multidrug resistance, sorcin was upregulated in 15 out of 21 patients (P<0.01). The differential expression levels of sorcin were confirmed by western blot and immunohistochemical analysis. In conclusion, sorcin expression in the human serum of breast cancer patients who are resistant to NAC was elevated when compared with that of NAC-sensitive patients.

Increased expression of sorcin is associated with multidrug resistance in leukemia cells via up-regulation of MDR1 expression through cAMP response element-binding protein

Sorcin, a 22 kDa Ca(2+) binding protein, was first identified in a vincristine-resistant Chinese hamster lung cell line, and was later demonstrated to be involved in the development of multidrug-resistance (MDR) phenotypes in a variety of human cancer cell lines. However, the exact role of sorcin in MDR cells is yet to be fully elucidated. Here we explored the role of sorcin in the development of MDR in leukemia cells, and revealed that the expression level of sorcin was directly correlated to the expression of MDR1/P-glycoprotein (P-gp). In addition, it was shown that sorcin induced the expression of MDR1/P-gp through a cAMP response element (CRE) between -716 and -709 bp of the mdr1/p-gp gene. Furthermore, overexpression of sorcin increased the phosphorylation of CREB1 and the binding of CREB1 to the CRE sequence of mdr1/p-gp promoter, and induced the expression of MDR1/P-gp. These findings suggested that sorcin induces MDR1/P-gp expression markedly through activation of the CREB pathway and is associated with the MDR phenotype. The new findings may be helpful for understanding the mechanisms of MDR in human cancer cells, prompting its further investigation as a molecular target to overcome MDR.

Serglycin: at the crossroad of inflammation and malignancy

Serglycin has been initially characterized as an intracellular proteoglycan expressed by hematopoietic cells. All inflammatory cells highly synthesize serglycin and store it in granules, where it interacts with numerous inflammatory mediators, such as proteases, chemokines, cytokines, and growth factors. Serglycin is implicated in their storage into the granules and their protection since they are secreted as complexes and delivered to their targets after secretion. During the last decade, numerous studies have demonstrated that serglycin is also synthesized by various non-hematopoietic cell types. It has been shown that serglycin is highly expressed by tumor cells and promotes their aggressive phenotype and confers resistance against drugs and complement system attack. Apart from its direct beneficial role to tumor cells, serglycin may promote the inflammatory process in the tumor cell microenvironment thus enhancing tumor development. In the present review, we discuss the role of serglycin in inflammation and tumor progression.

Serglycin in human cancers

Serglycin belongs to a family of small proteoglycans with Ser-Gly dipeptide repeats, and it is modified with different types of glycosaminoglycan side chains. Intracellular serglycin affects the retention and secretion of proteases, chemokines, or other cytokines by physically binding to these factors in secretory granules. Extracellular serglycin has been found to be released by several types of human cancer cells, and it is able to promote the metastasis of nasopharyngeal carcinoma cells. Serglycin can bind to CD44, which is another glycoprotein located in cellular membrane. Serglycin's function of promoting cancer cell metastasis depends on glycosylation of its core protein, which can be achieved by autocrine as well as paracrine secretion mechanisms. Further investigations are warranted to elucidate serglycin signaling mechanisms with the goal of targeting them to prevent cancer cell metastasis.

Serglycin proteoglycan deletion in mouse platelets: physiological effects and their implications for platelet contributions to thrombosis, inflammation, atherosclerosis, and metastasis

Serglycin is found in all nucleated hematopoietic cells and platelets, blood vessels, various reproductive and developmental tissues, and in chondrocytes. The serglycin knockout mouse has demonstrated that this proteoglycan is required for proper generation and function of secretory granules in several hematopoietic cells. The effects on platelets are profound, and include diminishing platelet aggregation responses and formation of platelet thrombi. This chapter will review cell-specific aspects of serglycin structure, its gene regulation, cell and tissue localization, and the effects of serglycin deletion on hematopoietic cell granule structure and function. The effects of serglycin knockout on platelets are described and discussed in detail. Rationales for further investigations into the contribution of serglycin to the known roles of platelets in thrombosis, inflammation, atherosclerosis, and tumor metastasis are presented.

Transcriptional analysis of doxorubicin-induced cytotoxicity and resistance in human hepatocellular carcinoma cell lines

BACKGROUND/AIMS

Hepatoma is either intrinsically resistant to chemotherapy or response to it but later develop resistance. The aim of this study was to clarify the relationship of treatment with doxorubicin (Dox) in hepatoma HepG2 cells and drug resistance developed by Dox.

METHODS

We have analysed the bioactivities and gene expression profiles of multidrug resistant (MDR) HepG2/DR cell line and its parental HepG2 cell, which were exposure to Dox.

RESULTS

We confirmed that Dox-induced apoptosis of HepG2 cells in a time-dependent manner; cDNA microarray and hierarchical cluster analysis demonstrate that the features of the transcriptional programme of the later response to Dox in HepG2 cells and MDR HepG2/DR cells have a common character, which is upregulation of stress response, cytoskeleton, ubiquitin-proteasome pathway and repressed G-protein signal transduction system; differentially expressed genes in MDR HepG2/DR such as drug transporters and tumour-associated antigens were verified at the levels of mRNA by semiquantitative reverse transcriptase-polymerase chain reaction.

CONCLUSIONS

These results reveal novel co-ordinated changes that occurred in resistant HepG2 cells to survive from cell apoptosis elicited by Dox treatment.

Networking of differentially expressed genes in human cancer cells resistant to methotrexate

Background

The need for an integrated view of data obtained from high-throughput technologies gave rise to network analyses. These are especially useful to rationalize how external perturbations propagate through the expression of genes. To address this issue in the case of drug resistance, we constructed biological association networks of genes differentially expressed in cell lines resistant to methotrexate (MTX).

Methods

Seven cell lines representative of different types of cancer, including colon cancer (HT29 and Caco2), breast cancer (MCF-7 and MDA-MB-468), pancreatic cancer (MIA PaCa-2), erythroblastic leukemia (K562) and osteosarcoma (Saos-2), were used. The differential expression pattern between sensitive and MTX-resistant cells was determined by whole human genome microarrays and analyzed with the GeneSpring GX software package. Genes deregulated in common between the different cancer cell lines served to generate biological association networks using the Pathway Architect software.

Results

Dikkopf homolog-1 (DKK1) is a highly interconnected node in the network generated with genes in common between the two colon cancer cell lines, and functional validations of this target using small interfering RNAs (siRNAs) showed a chemosensitization toward MTX. Members of the UDP-glucuronosyltransferase 1A (UGT1A) family formed a network of genes differentially expressed in the two breast cancer cell lines. siRNA treatment against UGT1A also showed an increase in MTX sensitivity. Eukaryotic translation elongation factor 1 alpha 1 (EEF1A1) was overexpressed among the pancreatic cancer, leukemia and osteosarcoma cell lines, and siRNA treatment against EEF1A1 produced a chemosensitization toward MTX.

Conclusions

Biological association networks identified DKK1, UGT1As and EEF1A1 as important gene nodes in MTX-resistance. Treatments using siRNA technology against these three genes showed chemosensitization toward MTX.

Prostate-tumor-inducing gene-1 analysis in human prostate cancer cells and tissue in relation to Mycoplasma infection

The potential role of PTI-1, in the natural story of prostate adenocarcinoma remains to be fully determined. PTI-1 expression was evaluated in human prostate cancer cell lines and in paraffin-embedded archive tissues. PTI-1 expression was found in Mycoplasma infected but not in non-infected cells. The lack of PTI-1 expression was also confirmed in fixed and paraffin-embedded human cancer prostate biopsies. The overall data indicate that, in prostate tumor cell lines, PTI-1 presence parallels Mycoplasma infection suggesting that PTI-1 might not necessarily play a major role in the onset of prostate tumorigenesis.

Sorcin, an important gene associated with multidrug-resistance in human leukemia cells

Sorcin, or soluble resistance-related calcium-binding protein, is a 22kD calcium-binding protein initially identified in many mutli-drug resistant (MDR) cell lines. We previously observed by gene profiling that sorcin is significantly up-regulated in a doxorubicin-induced MDR leukemia cell line, K562/A02, over its parent cells. We have also demonstrated that the level of sorcin expression in leukemia patients correlates not only directly with that of the mdr1 gene, but also inversely with patients' response to chemotherapies and overall prognosis. In this report, we have carried out experiments to dissect out the contribution of sorcin by itself to drug resistant phenotype in K562 cells. Overexpression of sorcin protein by gene transfection in K562 cells resulted in increased drug resistance, from 4.1- to 22.5-fold, to a variety of chemotherapeutic agents, including doxorubicin, etoposide, homoharringtonine and vincristine. On the other hand, inhibition of sorcin expression in both MDR K562/A02 and the sorcin-transfected K562 cells with sorcin-targeting small interfering RNA led to varying extent of reversal of drug resistance. These results confirm that sorcin is an important gene associated with the development of MDR in leukemia cells.

Deconstructing PTI-1: PTI-1 is a truncated, but not mutated, form of translation elongatin factor 1A1, eEF1A1

The prostate tumor-inducing gene 1 (PTI-1) transcript is detected in various human carcinoma cells. PTI-1 is reported to consist of a 5' untranslated region (5' UTR) homologous to mycoplasma 23S rRNA and a coding region corresponding to a truncated and mutated form of the translation elongation factor 1A, eEF1A. We have found that the PTI-1 transcript may encode a truncated, but not mutated, form of the human isoform eEF1A1. Additionally, the 5' UTR sequence of PTI-1 from genomic DNA of different cell lines and blood samples varies from the original sequence. This 5' -UTR region of PTI-1 presents a fusion of E. coli and Mycoplasma hyorhinis 23S rRNA. We have overexpressed the potential PTI-1 protein in E. coli and various human cell lines. The resulting protein could be detected by western blotting using anti-eEF1A antibodies. However, we were unable to detect the PTI-1 protein in LNCaP cell extracts. The potential roles of the PTI-1 protein in carcinogenesis and the origin of the PTI-1 gene in the human genome are discussed.

Identification of genes with differential expression in acquired drug-resistant gastric cancer cells using high-density oligonucleotide microarrays

PURPOSE

A major obstacle in chemotherapy is treatment failure due to anticancer drug resistance. The emergence of acquired resistance results from host factors and genetic or epigenetic changes in the cancer cells. The purpose of this study was to identify differentially expressed genes associated with acquisition of resistance in human gastric cancer cells.

EXPERIMENTAL DESIGN

We performed global gene expression analysis in the acquired drug-resistant gastric cancer cell lines to the commonly used drugs 5-fluorouracil, doxorubicin, and cisplatin using Affymetrix HG-U133A microarray. The gene expression patterns of 10 chemoresistant gastric cancer cell lines were compared with those of four parent cell lines using fold-change and Wilcoxon's test for data analysis.

RESULTS

We identified over 250 genes differentially expressed in 5-fluorouracil-, cisplatin-, or doxorubicin-resistant gastric cancer cell lines. Our expression analysis also identified eight multidrug resistance candidate genes that were associated with resistance to two or more of the tested chemotherapeutic agents. Among these, midkine (MDK), a heparin-binding growth factor, was overexpressed in all drug-resistant cell lines, strongly suggesting that MDK might contribute to multidrug resistance in gastric cancer cells.

CONCLUSIONS

Our investigation provides comprehensive gene information associated with acquired resistance to anticancer drugs in gastric cancer cells and a basis for additional functional studies.

The role of protein elongation factor eEF1A2 in ovarian cancer

Frequent gains of chromosome 20q12-13 in ovarian tumors indicate that at least one important oncogene is found at that locus. One of the genes there is EEF1A2, which maps to 20q13.3 and encodes protein elongation factor eEF1A2. This review will focus on recent evidence indicating that EEF1A2 is an important ovarian oncogene and that the protein elongation network can activate tumorigenesis and inhibit apoptosis.

Overexpression of sorcin, a calcium-binding protein, induces a low level of paclitaxel resistance in human ovarian and breast cancer cells

Paclitaxel, an antimitotic, anticancer agent, induces cell cycle arrest in the mitotic phase by binding to the beta-tubulin subunit and forming highly stable microtubule polymers that resist depolymerization. The overexpression of the P-glycoprotein (P-gp) and/or alteration in the cellular microtubules is associated with the development of paclitaxel resistance. However, we have established a paclitaxel-resistant human ovarian carcinoma subline (2008/13/4) wherein the degree of resistance could not be correlated with overexpression of P-gp, alterations in the alpha- and beta-tubulin isotypes, or changes in the drug-binding affinity of the microtubules. mRNA differential display analysis revealed the overexpression of sorcin, a calcium-binding protein in the 2008/13/4 cells. However, no detectable changes in the intracellular calcium levels were detected in the parental and the paclitaxel-resistant variant. Furthermore, co-treatment with A23187, a calcium ionophore, did not alter the cytotoxicity of paclitaxel against the parental and the paclitaxel-resistant cells. Transfection of the parental 2008 cells with full-length sorcin cDNA induced a low level (3-5-fold) of paclitaxel resistance. In addition, transfection of human breast cancer cells with the full-length sorcin cDNA also led to the induction of a low level of paclitaxel resistance in the transfectants. Although the overexpression of sorcin did not produce high levels of paclitaxel resistance, the results obtained present compelling evidence of the involvement of sorcin in developing low-level paclitaxel resistance in a variety of tumor cells. The precise biochemical mechanism(s) by which sorcin overexpression induces low-level paclitaxel resistance is currently under investigation.

Molecular markers and determinants of prostate cancer metastasis

Although intensely studied, the molecular and biochemical determinants of prostate cancer development and progression remain ill-defined. Moreover, current markers and methodologies cannot distinguish between a tumor that will remain indolent and not impinge on patient survival, versus a tumor with aggressive traits culminating in metastatic spread and death. Once prostate cancer is confirmed the most significant threat to a patient's survival and quality of life involves tumor metastasis. Radical surgery notwithstanding, prostate cancer accounts for 10% of all cancer-related deaths primarily arising through development of metastasis. Metastasis markers demonstrating an acceptable level of reliability are an obvious necessity if disproportionate and costly treatment is to be avoided and a reasonably accurate determination of clinical prognosis and measure of successful response to treatment is to be made. Therapeutic strategies that specifically inhibit metastatic spread are not presently possible and may not become available in the immediate future. This is because, while localized tumorigenesis has been relatively amenable to detection, analysis and treatment, metastasis remains a relatively undefined, complex and underexplored area of prostate cancer research. New findings in the field such subclasses of genes called metastasis suppressors and cancer progression suppressors, have opened up exciting avenues of investigation. We review current methodological approaches, model experimental systems and genes presently known or having potential involvement in human prostate cancer metastasis.