KAI1, a new metastasis suppressor gene, is reduced in metastatic hepatocellular carcinoma

Role of Tetraspanins in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is characterized by high prevalence, morbidity, and mortality. Liver cancer is the sixth most common cancer worldwide; and its subtype, HCC, accounts for nearly 80% of cases. HCC progresses rapidly, and to date, there is no efficacious treatment for advanced HCC. Tetraspanins belong to a protein family characterized by four transmembrane domains. Thirty-three known tetraspanins are widely expressed on the surface of most nucleated cells and play important roles in different biological processes. In our review, we summarize the functions of tetraspanins and their underlying mechanism in the life cycle of HCC, from its initiation, progression, and finally to treatment. CD9, TSPAN15, and TSPAN31 can promote HCC cell proliferation or suppress apoptosis. CD63, CD151, and TSPAN8 can also facilitate HCC metastasis, while CD82 serves as a suppressor of metastasis. TSPAN1, TSPAN8, and CD151 act as prognosis indicators and are inversely correlated to the overall survival rate of HCC patients. In addition, we discuss the potential of role of the tetraspanin family proteins as novel therapeutic targets and as an approach to overcome drug resistance, and also provide suggestions for further research.

Gene expression analysis of human prostate cell lines with and without tumor metastasis suppressor CD82

BACKGROUND

Tetraspanin CD82 is a tumor metastasis suppressor that is known to down regulate in various metastatic cancers. However, the exact mechanism by which CD82 prevents cancer metastasis is unclear. This study aims to identify genes that are regulated by CD82 in human prostate cell lines.

METHODS

We used whole human genome microarray to obtain gene expression profiles in a normal prostate epithelial cell line that expressed CD82 (PrEC-31) and a metastatic prostate cell line that does not express CD82 (PC3). Then, siRNA silencing was used to knock down CD82 expression in PrEC-31 while CD82 was re-expressed in PC3 to acquire differentially-expressed genes in the respective cell line.

RESULTS

Differentially-expressed genes with a P < 0.05 were identified in 3 data sets: PrEC-31 (+CD82) vs PrEC-31(-CD82), PC3-57 (+CD82) vs. PC3-5 V (-CD82), and PC3-29 (+CD82) vs. PC3-5 V (-CD82). Top 25 gene lists did not show overlap within the data sets, except (CALB1) the calcium binding protein calbindin 1 which was significantly up-regulated (2.8 log fold change) in PrEC-31 and PC3-29 cells that expressed CD82. Other most significantly up-regulated genes included serine peptidase inhibitor kazal type 1 (SPINK1) and polypeptide N-acetyl galactosaminyl transferase 14 (GALNT14) and most down-regulated genes included C-X-C motif chemokine ligand 14 (CXCL14), urotensin 2 (UTS2D), and fibroblast growth factor 13 (FGF13). Pathways related with cell proliferation and angiogenesis, migration and invasion, cell death, cell cycle, signal transduction, and metabolism were highly enriched in cells that lack CD82 expression. Expression of two mutually inclusive genes in top 100 gene lists of all data sets, runt-related transcription factor (RUNX3) and trefoil factor 3 (TFF3), could be validated with qRT-PCR.

CONCLUSION

Identification of genes and pathways regulated by CD82 in this study may provide additional insights into the role that CD82 plays in prostate tumor progression and metastasis, as well as identify potential targets for therapeutic intervention.

Gangliosides and CD82 inhibit the motility of colon cancer by downregulating the phosphorylation of EGFR at different tyrosine sites and signaling pathways

Previous studies have shown that (GM3), a ganglioside, suppresses hepatoma cell motility and migration by inhibiting phosphorylation of EGFR and the activity of the PI3K/AKT signaling pathway. Therefore, the aim of the present study was to investigate whether the combined treatment of CD82 with gangliosides can exert a synergistic inhibitory effect on cell motility and migration. Epidermal growth factor receptor (EGFR) signaling was studied for its role in the mechanism through which CD82 and gangliosides synergistically inhibit the motility and migration of SW620 human colon adenocarcinoma cells. GM3 and/or GM2 treatment, and/or overexpression of CD82 was performed in SW620 cells. High-performance thin layer chromatography, reverse transcription-quantitative PCR, western blotting and flow cytometry assays were used to confirm the content changes of GM2, GM3 and CD82. In addition, the phosphorylation of EGFR, MAPK and Akt were evaluated by western blot analysis. SW620 cell motility was investigated using wound healing analysis and chemotaxis migration assay. The combination of GM3 and GM2 with CD82 was found to markedly suppress EGF-stimulated SW620 cell motility compared with the individual factors or combination of GM2 or GM3 with CD82 by inhibiting the phosphorylation of EGFR. The results suggested that CD82 in combination with either GM2 or GM3 can exert a synergistic inhibitory effect on cell motility and migration; however, the synergistic mechanisms elicited by GM2 or GM3 with CD82 differ.

Tspan15 Is a New Stemness-Related Marker in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the second cause of cancer-related deaths worldwide. A clearer understanding of the molecular mechanisms underlying tumor growth and invasiveness remains crucial for developing new therapies. Here, the expression of tetraspanins, a family of plasma membrane organizers involved in tumor progression, has been addressed. Integrative approaches combining transcriptomics and bioinformatics allow demonstrating the induced and heterogeneous expression of Tspan15 in HCC. Tspan15 positive tumors exhibit signatures related to hepatic progenitor cells as well as recurrence of cancer. Immunohistochemistry experiments confirm Tspan15 expression in the subset of HCC expressing stemness-related markers such as EpCAM and Cytokeratin-19. Functional networks reveal that most of these genes expressed in correlation to Tspan15 support cell proliferation. Furthermore, Tspan15 overexpression in the hepatoma cell line HepG2 significantly increases cell proliferation. A quantitative proteomic analysis of the secretome reveals a higher abundance of the protein connective tissue growth factor (CTGF), a pleiotropic matricellular signaling protein. Proteomic profiling of Tspan15 complexes allows identifying numerous membrane proteins including several growth factor receptors. Finally, Tspan15 increases ERK1/2 phosphorylation that directly controls CTGF expression and secretion. In conclusion, Tspan15 is a new stemness-related marker in HCC which exhibits high potential of tumor growth and recurrence.

Silencing of Kangai 1 C-terminal interacting tetraspanin suppresses progression of cholangiocarcinoma

Cholangiocarcinoma (CC) is the second most common primary hepatic malignancy. CC treatment options are very limited especially for patients with distant metastasis. Kangai 1 C-terminal interacting tetraspanin (KITENIN) is highly expressed in numerous cancers, but the role of KITENIN in CC remains unknown. Here, we have investigated for the first time the function of KITENIN in human CC cell lines (TFK-1, SZ-1), tissues and a CC mouse model (Alb-Cre/LSL-KRAS^G12D/p53^L/L). KITENIN was expressed in 92.2% of human CC tissues, in murine CC samples and also in human CC cell lines. Knockdown of KITENIN by small interfering RNA (siRNA) effectively reduced proliferation, migration, invasion and colony formation in both intra- and extra-hepatic CC cells. The expression of epithelial-mesenchymal transition (EMT) markers like N-cadherin, Vimentin, Snail and Slug were suppressed in KITENIN knockdown CC cells. Our results indicate that KITENIN is crucial for cholangiocarcinogenesis and it might become a potential therapeutic target for human CC treatment.

Metastasis suppressors: functional pathways

Metastasis is a complex process and a major contributor of death in cancer patients. Metastasis suppressor genes are identified by their ability to inhibit metastasis at a secondary site without affecting the growth of primary tumor. In this review, we have conducted a survey of the metastasis suppressor literature to identify common downstream pathways. The metastasis suppressor genes mechanistically target MAPK, G-protein-coupled receptor, cell adhesion, cytoskeletal, transcriptional regulatory, and metastasis susceptibility pathways. The majority of the metastasis suppressor genes are functionally multifactorial, inhibiting metastasis at multiple points in the cascade, and many operate in a context-dependent fashion. A greater understanding of common pathways/molecules targeted by metastasis suppressor could improve metastasis treatment strategies.

The lichen secondary metabolite atranorin suppresses lung cancer cell motility and tumorigenesis

Lichens are symbiotic organisms that produce various secondary metabolites. Here, different lichen extracts were examined to identify secondary metabolites with anti-migratory activity against human lung cancer cells. Everniastrum vexans had the most potent inhibitory activity, and atranorin was identified as an active subcomponent of this extract. Atranorin suppressed β-catenin-mediated TOPFLASH activity by inhibiting the nuclear import of β-catenin and downregulating β-catenin/LEF and c-jun/AP-1 downstream target genes such as CD44, cyclin-D1 and c-myc. Atranorin decreased KAI1 C-terminal interacting tetraspanin (KITENIN)-mediated AP-1 activity and the activity of the KITENIN 3′-untranslated region. The nuclear distribution of the AP-1 transcriptional factor, including c-jun and c-fos, was suppressed in atranorin-treated cells, and atranorin inhibited the activity of Rho GTPases including Rac1, Cdc42, and RhoA, whereas it had no effect on epithelial-mesenchymal transition markers. STAT-luciferase activity and nuclear STAT levels were decreased, whereas total STAT levels were moderately reduced. The human cell motility and lung cancer RT² Profiler PCR Arrays identified additional atranorin target genes. Atranorin significantly inhibited tumorigenesis in vitro and in vivo. Taken together, our results indicated that E. vexans and its subcomponent atranorin may inhibit lung cancer cell motility and tumorigenesis by affecting AP-1, Wnt, and STAT signaling and suppressing RhoGTPase activity.

Impact of KITENIN on tumor angiogenesis and lymphangiogenesis in colorectal cancer

Angiogenesis and lymphangiogenesis are involved in the dissemination of tumor cells from solid tumors to regional lymph nodes and various distant sites. KAI1 COOH-terminal interacting tetraspanin (KITENIN) contributes to tumor progression and poor clinical outcomes in various cancers including colorectal cancer. The aim of the present study was to evaluate whether KITENIN affects tumor angiogenesis and lymphangiogenesis in colorectal cancer. A KITENIN small interfering RNA vector was used to silence KITENIN expression in colorectal cancer cell lines including DLD1 and SW480 cells. To evaluate the ability of KITENIN to induce angiogenesis and lymphangiogenesis in human umbilical vein endothelial cells (HUVECs) and lymphatic endothelial cells (HLECs), we performed Matrigel invasion and tube formation assays. Immunohistochemistry was used to determine the expression of KITENIN in colorectal cancer tissues. Angiogenesis and lymphangiogenesis were evaluated by immunostaining with CD34 and D2-40 antibodies. KITENIN silencing inhibited both HUVEC invasion and tube formation in the DLD1 and SW480 cells. KITENIN silencing led to decreased expression of the angiogenic inducers vascular endothelial growth factor (VEGF)-A and hypoxia-inducible factor-1α and increased expression of the angiogenic inhibitor angiostatin. KITENIN silencing did not inhibit either HLEC invasion or tube formation in all tested cells, but it resulted in decreased expression of the lymphangiogenic inducer VEGF-C. KITENIN expression was significantly associated with tumor stage, depth of invasion, lymph node and distant metastases and poor survival. The mean microvessel density was significantly higher in the KITENIN-positive tumors than that in the KITENIN-negative tumors. However, the mean lymphatic vessel density of KITENIN-positive tumors was not significantly higher than that of the KITENIN-negative tumors. These results suggest that KITENIN promotes tumor progression by enhancing angiogenesis in colorectal cancer.

Clinicopathological significance of KAI1 expression and epithelial-mesenchymal transition in non-small cell lung cancer

Background

KAI1 and epithelial-mesenchymal transition (EMT) is related to both angiogenesis and lymphangiogenesis and is an important target in new cancer treatment strategies. We aimed to investigate the KAI1 and marker of EMT expression and correlation with lymph node metastasis (LNM) and explore their prognostic impact in non-small cell lung cancer (NSCLC).

Methods

Tumor tissue specimens from 312 resected patients with stage I–IIIA NSCLC were obtained. Immunohistochemistry was used to assess the expression of the molecular markers KAI1, E-cadherin (E-cad), vimentin, CD34, and D2-40.

Results

There were 153 N0 and 159 N+ patients. Tumor cell expression of KAI1and the marker of EMT, lymphatic vessel density (LVD), and microvessel density (MVD) were related to LNM. In multivariate analyses, the ages of patients, high tumor cell KAI1 expression, EMT, and the scores of MVD were independent factor of prognosis.

Conclusions

Tumor cell KAI1 expression, EMT, LVD, and MVD correlate with LNM. Thus, the detection of KAI1, expression of markers of EMT, and the scores of MVD may be used as a potential indicator of NSCLC prognosis.

Exosomes released from breast cancer carcinomas stimulate cell movement

For metastasis to occur cells must communicate with to their local environment to initiate growth and invasion. Exosomes have emerged as an important mediator of cell-to-cell signalling through the transfer of molecules such as mRNAs, microRNAs, and proteins between cells. Exosomes have been proposed to act as regulators of cancer progression. Here, we study the effect of exosomes on cell migration, an important step in metastasis. We performed cell migration assays, endocytosis assays, and exosome proteomic profiling on exosomes released from three breast cancer cell lines that model progressive stages of metastasis. Results from these experiments suggest: (1) exosomes promote cell migration and (2) the signal is stronger from exosomes isolated from cells with higher metastatic potentials; (3) exosomes are endocytosed at the same rate regardless of the cell type; (4) exosomes released from cells show differential enrichment of proteins with unique protein signatures of both identity and abundance. We conclude that breast cancer cells of increasing metastatic potential secrete exosomes with distinct protein signatures that proportionally increase cell movement and suggest that released exosomes could play an active role in metastasis.

Tetraspanin 7 (TSPAN7) expression is upregulated in multiple myeloma patients and inhibits myeloma tumour development in vivo

BACKGROUND

Increased expression of the tetraspanin TSPAN7 has been observed in a number of cancers; however, it is unclear how TSPAN7 plays a role in cancer progression.

METHODS

We investigated the expression of TSPAN7 in the haematological malignancy multiple myleoma (MM) and assessed the consequences of TSPAN7 expression in the adhesion, migration and growth of MM plasma cells (PC) in vitro and in bone marrow (BM) homing and tumour growth in vivo. Finally, we characterised the association of TSPAN7 with cell surface partner molecules in vitro.

RESULTS

TSPAN7 was found to be highly expressed at the RNA and protein level in CD138(+) MM PC from approximately 50% of MM patients. TSPAN7 overexpression in the murine myeloma cell line 5TGM1 significantly reduced tumour burden in 5TGM1/KaLwRij mice 4 weeks after intravenous adminstration of 5TGM1 cells. While TSPAN7 overexpression did not affect cell proliferation in vitro, TSPAN7 increased 5TGM1 cell adhesion to BM stromal cells and transendothelial migration. In addition, TSPAN7 was found to associate with the molecular chaperone calnexin on the cell surface.

CONCLUSION

These results suggest that elevated TSPAN7 may be associated with better outcomes for up to 50% of MM patients.

Tetraspanin-enriched microdomains and hepatocellular carcinoma progression

As in many tumors, heterogeneity within the cell population is one of the main features of hepatocellular carcinoma (HCC). Heterogeneity results from the ability of tumor to produce multiple subpopulations of cells with diverse genetic, biochemical and immunological characteristics. Little is known about how heterogeneity emerges and how it is maintained. Fluctuations in single cells can be masked or completely misrepresented when cell populations are analyzed. It has become exceedingly apparent that the utility of measurement based on the analysis of bulk specimens is limited by intra-tumor genetic and epigenetic heterogeneity, as characteristics of the most abundant cell type might not necessarily predict the properties of cell populations. Yet, such non-uniformities often unveil molecular patterns that can represent mechanisms of tumor progression. Interestingly, variability among single cells in a population may arise from different responses to intrinsic and extrinsic perturbations mainly mediated by the plasma membrane. The association of certain proteins, including tetraspanins, and lipids in specific location on the plasma membrane constitutes specialized structure called tetraspanin-enriched microdomains (TEMs). TEMs organization in cancer may reveal essential clues for understanding pathogenic mechanisms underlying cancer progression. Along these lines, TEMs and HCC progression represent a valuable paradigm for gaining a deeper understanding of such mechanisms.

Anti-miR-197 inhibits migration in HCC cells by targeting KAI 1/CD82

AIM

To investigate the metastatic effects and mechanisms of miR-197 in hepatocellular carcinoma (HCC).

METHODS AND RESULTS

The levels of miR-197 increased in HCC cells and tissues compared with a normal hepatic cell line (LO2) and adjacent nontumorous liver tissues, respectively. miR-197 expression negatively correlated with CD82 mRNA expression in these cell lines and tissues. Dual luciferase reporter assay and Western blot confirmed a direct interaction between miR-197 and CD82 3'UTR sequences. After miR-197 was silenced in HCC cells, CD82 expression increased. In the presence of human hepatocyte growth factor (HGF), cells silenced for anti-miR-197 exhibited elongated cellular tails and diminished lamellipodia due to reductions in both ROCK activity and the levels of Rac 1 protein. Downregulation of miR-197 along with the upregulation of CD82 in HCC cells resulted in the inhibition of HCC migration and invasion in vitro and in vivo.

CONCLUSION

Taken together, these data suggest that anti-miR-197 suppresses HCC migration and invasion by targeting CD82. The regulation of the miR-197/CD82 axis could be a novel therapeutic target in future HCC effective therapy.

The fibrotic microenvironment as a heterogeneity facet of hepatocellular carcinoma

It has long been recognized that hepatocellular carcinoma heterogeneity arises from variation in the microenvironment or from genomic alteration. Only recently it has become clear that non-genetic alterations, such as cytoskeletal rearrangement, protein localization and formation of protein complexes, are also involved in generating phenotype variability. These proteome fluctuations cause genetically identical cells to vary significantly in their responsiveness to microenvironment stimuli. In the cirrhotic liver pre-malignant hepatocytes are continuously exposed to abnormal microenvironments, such as direct contact with activated hepatic stellate cells (HSCs) and extracellular matrix components. These abnormal environments can have pronounced influences on the epigenetic aspects of cells, translating into abnormal phenotypes. Here we discuss non-genetic causes of phenotypic heterogeneity of hepatocellular carcinoma, with an emphasis on variability of membrane protein complexes and transferred functions raising important implications for diagnosis and treatment.

FXR controls the tumor suppressor NDRG2 and FXR agonists reduce liver tumor growth and metastasis in an orthotopic mouse xenograft model

The farnesoid X receptor (FXR) is expressed predominantly in tissues exposed to high levels of bile acids and controls bile acid and lipid homeostasis. FXR^−/− mice develop hepatocellular carcinoma (HCC) and show an increased prevalence for intestinal malignancies, suggesting a role of FXR as a tumor suppressor in enterohepatic tissues. The N-myc downstream-regulated gene 2 (NDRG2) has been recognized as a tumor suppressor gene, which is downregulated in human hepatocellular carcinoma, colorectal carcinoma and many other malignancies.

We show reduced NDRG2 mRNA in livers of FXR^−/− mice compared to wild type mice and both, FXR and NDRG2 mRNAs, are reduced in human HCC compared to normal liver. Gene reporter assays and Chromatin Immunoprecipitation data support that FXR directly controls NDRG2 transcription via IR1-type element(s) identified in the first introns of the human, mouse and rat NDRG2 genes. NDRG2 mRNA was induced by non-steroidal FXR agonists in livers of mice and the magnitude of induction of NDRG2 mRNA in three different human hepatoma cell lines was increased when ectopically expressing human FXR. Growth and metastasis of SK-Hep-1 cells was strongly reduced by non-steroidal FXR agonists in an orthotopic liver xenograft tumor model. Ectopic expression of FXR in SK-Hep1 cells reduced tumor growth and metastasis potential of corresponding cells and increased the anti-tumor efficacy of FXR agonists, which may be partly mediated via increased NDRG2 expression. FXR agonists may show a potential in the prevention and/or treatment of human hepatocellular carcinoma, a devastating malignancy with increasing prevalence and limited therapeutic options.

Expression of CD82 in human trophoblast and its role in trophoblast invasion

BACKGROUND

Well-controlled trophoblast invasion at maternal-fetal interface is a critical event for the normal development of placenta. CD82 is a member of transmembrane 4 superfamily, which showed important role in inhibiting tumor cell invasion and migration. We surmised that CD82 are participates in trophoblast differentiation during placenta development.

METHODOLOGY/PRINCIPAL FINDINGS

CD82 was found to be strongly expressed in human first trimester placental villous and extravillous trophoblast cells as well as in trophoblast cell lines. To investigate whether CD82 plays a role in trophoblast invasion and migration, we further utilized human villous explants culture model on matrigel and invasion/migration assay of trophoblast cell line HTR8/SVneo. CD82 siRNA significantly promoted outgrowth of villous explants in vitro (P<0.01), as well as invasion and migration of HTR8/SVneo cells (P<0.05), whereas the trophoblast proliferation was not affected. The enhanced effect of CD82 siRNA on invasion and migration of trophoblast cells was found associated with increased gelatinolytic activities of matrix metalloproteinase MMP9 while over-expression of CD82 markedly decreased trphoblast cell invasion and migration as well as MMP9 activities.

CONCLUSIONS/SIGNIFICANCE

These findings suggest that CD82 is an important negative regulator at maternal-fetal interface during early pregnancy, inhibiting human trophoblast invasion and migration.

Metastasis suppressor KAI1/CD82 attenuates the matrix adhesion of human prostate cancer cells by suppressing fibronectin expression and β1 integrin activation

KAI1/CD82, a tetraspanin membrane protein functions as a metastasis suppressor in many types of human cancers and has been shown to regulate cell adhesion properties. In the present study, we investigated the underlying mechanism of KAI1/CD82-mediated changes in cell adhesion to the extracellular matrix using human prostate cancer cells. We found that high KAI1/CD82 expression attenuated short-term cell adhesion to uncoated- or fibronectin-coated plates. Moreover, high KAI1/CD82 expression generated an extracellular environment unfavorable for cell adhesion as compared to low KAI1/CD82 expression, suggesting KAI1/CD82-dependent regulation of extracellular matrix (ECM) molecule(s) expression and/or secretion. Among ECM components examined, fibronectin exhibited decreased expression and secretion in high KAI1/CD82-expressing cells. Furthermore, high KAI1/CD82 expression interfered with the activation of β (1) integrin at the cell surface while total β (1) integrin levels remained unchanged, concomitant with reduced formation of focal adhesion complex and decreased bundling of actin filaments. Finally, high KAI1/CD82 expression significantly retarded cell motility in a scratch wound assay. Taken together, our results strongly suggest that KAI1/CD82 attenuates the activation of β (1) integrin, and thereby down-regulates outside-in signaling of β (1) integrin, leading to the reduction of focal adhesion formation and fibronectin expression/secretion, which subsequently interferes with cell adhesion properties and motility.

Celecoxib inhibits cell growth and up-regulates KAI1/CD82 protein expression in human hepatocellular carcinoma cell line HepG2

AIM: To investigate the effect of celecoxib on cell proliferation, apoptosis and KAI1/CD82 expression in human hepatocellular carcinoma cell line HepG2.

METHODS: After HepG2 cells were treated with different concentrations of celecoxib (12.5, 25.0, 50.0, 100.0, 200.0 μmol/L), cell proliferation was measured by CCK-8 assay, cell apoptosis was detected by flow cytometry, and the expression of KAI1/CD82 protein was detected by Western blot.

RESULTS: Treatment with celecoxib significantly inhibited the proliferation of HepG2 cells (P < 0.05) in a dose- and time-dependent manner, and the reduced rate of growth of HepG2 cells treated with 200.0 μmol/L celecoxib for 72 h was 69.23%. Treatment with celecoxib induced apoptosis of HepG2 cells in a dose-dependent manner. The apoptosis rates of cells treated with 12.5, 50.0, or 200.0 μmol/L celecoxib for 48 h were significantly higher than that of control cells (18.79% ± 2.37%, 46.94% ± 0.78%, 69.48% ± 0.63% vs 16.72% ± 1.54%, all P < 0.05). Treatment with celecoxib significantly up-regulated the expression of KAI1/CD82 protein in a dose-dependent manner (48 h: 0.394 ± 0.007, 0.886 ± 0.057, 1.099 ± 0.079 vs 0.321 ± 0.020, all P < 0.05).

CONCLUSION: Celecoxib inhibits cell proliferation and induces apoptosis possibly by up-regulating KAI1/CD82 protein expression in human hepatocellular carcinoma cell line HepG2.

KAI1/CD82 suppresses hepatocyte growth factor-induced migration of hepatoma cells via upregulation of Sprouty2

We conducted a study concerning the suppressive mechanism of KAI1/CD82 on hepatoma cell metastasis. Hepatocyte growth factor (HGF) induces the migration of hepatoma cells through activation of cellular sphingosine kinase 1 (SphK1). Adenovirus-mediated gene transfer of KAI1 (Ad-KAI1) downregulates the SphK1 expression and suppresses the HGF-induced migration of SMMC-7721 human hepatocellcular carcinoma cells. Overexpression of KAI1/CD82 significantly elevates Sprouty2 at the protein level. Ablation of Sprouty2 with RNA interference can block the KAI1/CD82-induced suppression of hepatoma cell migration and downregulation of SphK1 expression. It is demonstrated that KAI1/CD82 suppresses HGF-induced migration of hepatoma cells via upregulation of Sprouty2.

Loss of the eukaryotic initiation factor 3f in pancreatic cancer

Aberrant regulation of the translation initiation is known to contribute to tumorigenesis. eIF3 plays an important role in translation initiation. eIF3f is the p47 subunit of the eIF3 complex whose function in cancer is not clear. Initial studies from our group indicated that eIF3f expression is decreased in pancreatic cancer. Overexpression of eIF3f induces apoptosis in pancreatic cancer cells. The eIF3f gene is located at chromosome band region 11p15.4. Loss of 11p15.4 is a common event in many tumors including pancreatic cancer. In order to investigate the molecular mechanism of the decreased expression of eIF3f in pancreatic cancer, we performed loss of heterozygosity (LOH) analysis in 32 pancreatic cancer specimens using three microsatellite markers encompassing the eIF3f gene. We showed that the prevalence of LOH ranged from 71% to 93%. We also performed eIF3f gene copy number analysis using quantitative real time PCR to further confirm the specific allelic loss of eIF3f gene in pancreatic cancer. We demonstrated a statistically significant decrease of eIF3f gene copy number in pancreatic tumors compared with normal tissues with a tumor/normal ratio of 0.24. Furthermore, RNA in situ hybridization and tissue microarray immunohistochemistry analysis demonstrated that eIF3f expression is significantly decreased in human pancreatic adenocarcinoma tissues compared to normal pancreatic tissues. These data provides new insight into the understanding of the molecular pathogenesis of eIF3f during pancreatic tumorigenesis.

Overexpression and role of the ATPase and putative DNA helicase RuvB-like 2 in human hepatocellular carcinoma

Using a proteomic analysis of human hepatocellular carcinoma (HCC), we identified the overexpression in 4 tumors of RuvB-like 2 (RUVBL2), an ATPase and putative DNA helicase known to interact with beta-catenin and cellular v-myc myelocytomatosis viral oncogene homolog (c-myc). RUVBL2 expression was further analyzed in tumors with quantitative reverse-transcription polymerase chain reaction analysis and immunohistochemistry; in addition, RUVBL2 expression in a HuH7 cell line was silenced by small interfering RNA or increased with a lentiviral vector. RUVBL2 messenger RNA overexpression was confirmed in 72 of 96 HCC cases, and it was associated with poorly differentiated tumors (P = 0.02) and a poor prognosis (P = 0.02) but not with beta-catenin mutations or c-myc levels. Although RUVBL2 was strictly nuclear in normal hepatocytes, tumoral hepatocytes exhibited additional cytoplasmic staining. There was no mutation in the coding sequence of RUVBL2 in 10 sequenced cases. Silencing RUVBL2 in HuH7 HCC cells reduced cell growth (P < 0.001) and increased apoptosis, as shown by DNA fragmentation (P < 0.001) and caspase 3 activity (P < 0.005). This was associated with an increased expression of several proapoptotic genes and with an increased conformational activation of Bak-1 and Bax. On the other hand, HuH7 cells with an overexpression of RUVBL2 grew better in soft agar (P < 0.03), had increased resistance to C2 ceramide-induced apoptosis (P < 0.001), and gave rise to significantly larger tumors when injected into immunodeficient Rag2/gammac mice (P = 0.016).

CONCLUSION

RUVBL2 is overexpressed in a large majority of HCCs. RUVBL2 overexpression enhances tumorigenicity, and RUVBL2 is required for tumor cell viability. These results argue for a major role of RUVBL2 in liver carcinogenesis.

Nm23/NDP kinases in hepatocellular carcinoma

One of the most aggressive cancers is hepatocellular carcinoma, which is associated with a very poor patient outcome due to a high recurrence rate and metastatic spread. NM23, the first metastasis suppressor gene to be identified, has been widely studied in human cancers. However, conflicting results have been obtained depending on the tumor type and the evaluation protocol. The current knowledge of NM23 as a diagnostic and/or prognostic marker in hepatocellular carcinoma is reviewed herein. Most studies demonstrate an inverse association between the expression of NM23-H1 and the metastatic potential, which is not observed with the closely related NM23-H2 isoform. Transfection of metastatic hepatoma cells with NM23 reduced their metastatic potential, as for other tumor cell lines. The demonstration of a causative role of NM23 in metastatic dissemination in a mouse model of hepatocarcinoma suggests that hepatocarcinoma-derived cells could be good models for the analysis of the molecular mechanisms involved in NM23 action.

KAI1/CD82, a tumor metastasis suppressor

Tetraspanin KAI1/CD82 is a wide-spectrum tumor metastasis suppressor. KAI1/CD82 suppresses tumor metastasis by primarily inhibiting cancer cell motility and invasiveness. In tetraspanin-enriched microdomain, KAI1/CD82 associates with the proteins important for cell migration such as cell adhesion molecule, growth factor receptor, and signaling molecule. Likely, KAI1/CD82 down-regulates the functions of these motility-related proteins to inhibit cell migration. The loss of KAI1/CD82 expression in invasive and metastatic cancers is due to a complex, epigenetic mechanism that probably involves transcription factors such as NFkappaB, p53, and beta-catenin.

Chromosome 18 suppresses tumorigenic properties of human prostate cancer cells

Although prostate cancer is still the most diagnosed cancer in men, most genes implicated in its progression are yet to be identified. Chromosome abnormalities have been detected in human prostate tumors, many of them associated with prostate cancer progression. Indeed, alterations (including deletions or amplifications) of more than 15 human chromosomes have been reported in prostate cancer. We hypothesized that transferring normal human chromosomes into human prostate cancer cells would interfere with their tumorigenic and/or metastatic properties. We used microcell-mediated chromosome transfer to introduce human chromosomes 10, 12, 17, and 18 into highly tumorigenic (PC-3M-Pro4) and highly metastatic (PC-3M-LN4) PC-3-derived cell lines. We tested the in vitro and in vivo properties of these hybrids. Introducing chromosome 18 into the PC-3M-LN4 prostate cancer cell line greatly reduced its tumorigenic phenotype. We observed retarded growth in soft agar, decreased invasiveness through Matrigel, and delayed tumor growth into nude mice, both subcutaneously and orthotopically. This phenotype is associated with a marker in the 18q21 region. Combined with the loss of human chromosome 18 regions often seen in patients with advanced prostate cancer, our results show that chromosome 18 encodes one or more tumor-suppressor genes whose inactivation contributes to prostate cancer progression.

Expression profiling in hepatocellular carcinoma with intrahepatic metastasis: identification of high-mobility group I(Y) protein as a molecular marker of hepatocellular carcinoma metastasis

Hepatocellular carcinoma (HCC) is one of the most common and aggressive human malignancies. Its high mortality rate is mainly a result of intra-hepatic metastases. To investigate the detailed genetic mechanisms in cancer metastasis, we compared the expression profiles of 20 HCCs with intrahepatic metastasis and 10 HCCs without intrahepatic metastasis using an oligonucleotide array. Of the approximately 12,600 genes that were analyzed, we identified 34 genes whose expression levels were significantly correlated with intrahepatic metastasis (P<0:05). Of these genes, we further investigated the expression of high-mobility group I(Y) [HMG-I(Y)] protein. Real-time quantitative reverse transcription polymerase chain reaction (RT-PCR) confirmed that HMG-I(Y) was upregulated in HCC with intrahepatic metastasis, compared to its level in HCC without intrahepatic metastasis. Further immunohistochemical examination of HMG-I(Y) revealed a significant overexpression in HCC with intrahepatic metastasis, compared with that in HCC without intrahepatic metastasis (P<0:05). These results indicate that the molecular signatures of HCC with intrahepatic metastasis and of HCC without intrahepatic metastasis are clearly different. HMG-I(Y) expression was associated with intrahepatic metastasis and may be a predictive marker of HCC intrahepatic metastasis.

Downregulation of KAI1 mRNA in localised prostate cancer and its bony metastases does not correlate with p53 overexpression

Recent data have proposed that transcription of the KAI1 metastasis suppressor gene is directly mediated by p53 and that loss of KAI1 expression in advanced prostate cancer is simply due to loss of p53 function after mutation. To investigate this possibility, we have examined KAI1 mRNA (by in situ hybridisation) and p53 protein expression (by immunohistochemistry) as an indicator of wildtype or mutant p53, in a series of 77 paraffin-embedded prostate tissue samples, including post-mortem normal prostates (2), benign prostatic hyperplasia (10), localised cancer (grades 4-6, 25; grades 7-9, 21) and prostate-derived bony metastases (19). Overall, we confirmed that expression of KAI1 mRNA decreased from normal tissue, through localised cancer to bony metastases (P=0.055, tending to significance), while levels of p53 staining significantly increased with cancer progression (P=0.046). These were consistent with the possibility that loss of p53 function might be responsible for loss of KAI1 mRNA. However, by close examination of KAI1 and p53 in adjacent tissue sections, we found no correlation between decreased levels of KAI1 mRNA and overexpression of p53 protein (P=0.497). In addition, high levels of KAI1 mRNA could be identified in samples irrespective of p53 staining. Our data suggest that mutation of p53 is independent of the loss of KAI1 mRNA, and do not support a role for p53 in regulating the expression of KAI1.

Co-downregulation of PTEN, KAI-1, and nm23-H1 tumor/metastasis suppressor proteins in non-small cell lung cancer

The multistep process of carcinogenesis implies the accumulation of multiple molecular defects. Alteration of tumor suppressor and metastasis suppressor genes are the important steps. Increasing experimental evidence indicates that decreased expression of tumor-metastasis/suppressor genes and gene products are involved in the progression of a variety of human malignancies. In the present study, we have extended this analysis to non-small cell lung carcinomas (NSCLC). The expression and prognostic significance of the tumor suppressor gene PTEN and metastasis suppressor genes nm23-H1 and KAI-1 was evaluated in NSCLCs. Immunohistochemical staining was performed on formalin-fixed, paraffin-embedded tissues from 53 bronchogenic adenocarcinomas and 51 squamous cell carcinomas using monoclonal antibodies against PTEN, nm23H-1, and KAI-1 proteins. Immunohistochemical results were correlated with tumor stage, grade, lymph nodes positivity, metastasis, and patient survival. Significant co-expression of PTEN, nm23-H1 and KAI-1 was observed in NSCLC (P<.001 to .002). The immunohistochemical expression of these proteins was significantly higher in stages 1 and 2 compared with stages 3 and 4 (P=.04 for PTEN and KAI-1, P=.039 for nm23-H1). When all stages were considered together, loss of immunoreactivity for PTEN, nm23-H1 and KAI-1 was found in advanced NCSCLs (P=.015 for PTEN, P=.001 for KAI-1, P=.004 for nm23-H1), which is suggestive of co-downregulation of these proteins in the process of tumor progression. On multivariate analysis, negative staining for PTEN (P=.014), KAI-1 (P=.034), and nm23-H1 (a trend toward association for nm23-H1 reached near significance P=.08) correlated with disease-related death. Positive lymph node status was associated with negative immunostaining for PTEN (P=.007) but no correlation was observed for nm23-H1 and KAI-1. Loss of expression was linked to distant metastasis (P=.006 for PTEN, P=.002 for nm23H1, P=.001 for KAI-1). On multivariate analysis, co-downregulation of PTEN (P=.009), KAI-1 (P=.02), and nm23-H1 (P=.011) independently predicted shortened survival in NSCLC. Although NSCLC exhibits strong co-expression of PTEN, nm23-H1 and KAI-1, there is a loss of these proteins in high-stage tumors. Co-downregulation of PTEN, KAI-1, and nm23-H1 significantly correlates with distant metastasis and predicts shortened survival. Our study supports a role of these tumor suppressor and metastasis suppressor genes in the evolution and progression of NSCLC.

KAI1 expression in thyroid neoplasms: its linkage with clinicopathologic features in papillary carcinoma

KAI1 is a metastasis suppressor gene located on human chromosome 11p11.2. Previous studies have shown that the down-regulation of KAI1 mRNA and decreased expression of its gene product are significantly linked to carcinoma progression, including metastatic ability. In this study, we investigated KAI1 protein expression in thyroid neoplasms. KAI1 overexpression was observed in 64.0% of papillary carcinoma cases, and the incidence was significantly higher than in cases of follicular carcinoma (20.0%) (p = 0.0001). In papillary carcinomas, decreased KAI1 expression was frequently observed in cases invading beyond the thyroid capsule (p = 0.001), as well as in lymph node metastases (p = 0.0047) and poorly differentiated lesions (p = 0.0299). Furthermore, in anaplastic carcinoma, the incidence of KAI1 overexpression was lower than in papillary carcinoma (p < 0.0001), and only 4.2% of the cases overexpressed this gene. These results suggest that KAI1 down-regulation is significantly related to the progression of papillary carcinoma, including lymph node metastasis, and its anaplastic transformation.

Possible involvement of tetraspanin CO-029 in hematogenous intrahepatic metastasis of liver cancer cells

BACKGROUND AND AIM

A correlation between overexpression of tetraspanin CO-029 and the intrahepatic spread of hepatocellular carcinoma (HCC) has been observed in surgically resected specimens from humans. However, the cellular mechanisms involved in CO-029 protein modulation of the metastatic phenotype are unknown. In the present study, CO-029 cDNA was stably transfected into a non-metastatic human HCC cell line to investigate whether it could directly promote metastasis.

METHODS

We constructed a human HCC cell line that stably overexpressed CO-029 and mock transfectants. Using these transfectants, we examined cell proliferation characteristics in monolayer culture and the ability to adhere to culture plates coated with laminin, fibronectin, vitronectin and collagen type-I or type-IV. Orthotopic implantation of these transfectants to SCID mice was also performed.

RESULTS

Several clones of CO-029 transfectants and mock transfectants were established. The growth rates and adhesive properties to the extracellular matrix did not differ between CO-029 and mock transfectants. When orthotopically implanted, the size of the primary tumor in the liver did not differ between CO-029 and the mock transfectants. However, only CO-029 positive clones developed intrahepatic metastatic lesions.

CONCLUSION

These results suggest that CO-029 might be involved in hematogenous intrahepatic metastasis, although the precise cellular mechanisms involved remain unknown.

Effects of KAI1 gene on KAI1 protein expression in MHCC97-H hepatocellular carcinoma cells with high metastatic potential

AIM

To construct sense and antisense KAI1 expression plasmids and to explore their effects on KAI1 protein expression in MHCC97-H hepatocellular carcinoma cells with high metastatic potential.

METHODS

Sense and antisense KAI1 expression plasmids were constructed using subclone technique and transfected into MHCC97-H cells by DOTAP liposome system. KAI1 protein expression in transfected MHCC97-H cells was analyzed with immunocytochemical SP method.

RESULTS

Analysis of restriction endonuclease indicated the structure of two recombinants was consistent with the expected results of sense and antisense KAI1 expression plasmids. Compared with MHCC97-H cells, KAI1 protein staining in the MHCC97-H-S cells transfected with sense KAI1 expression plasmid was obviously enhanced(Integra Oculus Dehter ,IOD 20.127±5.099 vs 12.675±1.921,P <0.05).However, KAI1 expression in the MHCC97-H-AS cells transfected with KAI1 antisense gene was obviously weakened (IOD 8.681±2.472 vs 12.675±1.921, P <0.05).

CONCLUSION

We successfully constructed sense and antisense KAI1 expression plasmids. Sense KAI1 gene can upregulate the expression of KAI1 protein in MHCC97-H cells. On the other hand, antisense KAI1 gene can downregulate the expression of KAI1 protein in MHCC97-H cells.

Molecular cloning and characterization of LAPTM4B, a novel gene upregulated in hepatocellular carcinoma

Lysosomal-associated protein transmembrane-4 beta (LAPTM4B), a novel gene upregulated in hepatocellular carcinoma (HCC), was cloned using fluorescence differential display, RACE, and RT-PCR. It contains seven exons and encodes a 35-kDa protein with four putative transmembrane regions. Both the N- and C-termini of the protein are proline-rich, and may serve as potential ligands for the SH3 domain. Immunohistochemical analysis localized the protein predominantly to intracellular membranes. Northern blot showed that the LAPTM4B mRNAs were remarkably upregulated in HCC (87.3%) and correlated inversely with differentiation status. LAPTM4B was also overexpressed in many HCC-derived cell lines. It was also highly expressed in fetal livers and certain adult normal tissues including the heart, skeletal muscle, testis, and ovary. Promoter function assays showed a distinct difference in the gene's activities between BEL7402 and HLE cell lines, suggesting that the transcription factors responsible for regulation of the gene in the two cell lines are different, and that possible negative regulatory cis-elements may exist upstream of the promoter region. It was demonstrated that the N-terminus of LAPTM4B was essential for survival of the cells. Cells harboring the full-length LAPTM4B cDNA expression clone displayed a slightly increased efficiency in colony formation. These results suggest that LAPTM4B is a potential protooncogene, whose overexpression is involved in carcinogenesis and progression of HCC. In normal cells, it may also play important roles such as regulation of cell proliferation and survival.

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Predicting hepatitis B virus-positive metastatic hepatocellular carcinomas using gene expression profiling and supervised machine learning

Hepatocellular carcinoma (HCC) is one of the most common and aggressive human malignancies. Its high mortality rate is mainly a result of intra-hepatic metastases. We analyzed the expression profiles of HCC samples without or with intra-hepatic metastases. Using a supervised machine-learning algorithm, we generated for the first time a molecular signature that can classify metastatic HCC patients and identified genes that were relevant to metastasis and patient survival. We found that the gene expression signature of primary HCCs with accompanying metastasis was very similar to that of their corresponding metastases, implying that genes favoring metastasis progression were initiated in the primary tumors. Osteopontin, which was identified as a lead gene in the signature, was over-expressed in metastatic HCC; an osteopontin-specific antibody effectively blocked HCC cell invasion in vitro and inhibited pulmonary metastasis of HCC cells in nude mice. Thus, osteopontin acts as both a diagnostic marker and a potential therapeutic target for metastatic HCC.

Invasion and metastasis in pancreatic cancer

Pancreatic cancer remains a challenging disease with an overall cumulative 5-year survival rate below 1%. The process of cancer initiation, progression and metastasis is still not understood well. Invasion and tumor metastasis are closely related and both occur within a tumour-host microecology, where stroma and tumour cells exchange enzymes and cytokines that modify the local extracellular matrix, stimulate cell migration, and promote cell proliferation and tumor cell survival. During the last decade considerable progress has been made in understanding genetic alterations of genes involved in local and systemic tumor growth. The most important changes occur in genes which regulate cell cycle progression, extracellular matrix homeostasis and cell migration. Furthermore, there is growing evidence that epigenetic factors including angiogenesis and lymphangiogenesis may participate in the formation of tumor metastasis. In this review we highlight the most important genetic alterations involved in tumor invasion and metastasis and further outline the role of tumor angiogenesis and lymphangiogenesis in systemic tumor dissemination.

KAI1/CD82 protein expression in primary prostate cancer and in BPH associated with cancer

Current prognostic methods in primary prostate cancer cannot accurately identify patients with clinically significant disease at highest risk of developing metastases. This study examined KAI1/CD82 metastasis suppressor expression by quantitative immunohistochemical analysis of benign prostatic hyperplasia (BPH) and prostate cancer specimens. Altogether, prostate cancers exhibited significant KAI1 overexpression compared to BPH not associated with cancer (P = 0.022). Increased KAI1 expression in well and moderately differentiated cancers, above levels seen in BPH, with decreased expression in poorly differentiated cancers was observed. Interestingly, KAI1 expression in BPH associated with cancers was significantly higher than in BPH not associated with cancer (P = 0.009). Thus, KAI1 overexpression may restrain onset and early stage prostate cancer development, whilst its loss may predispose the patient to more aggressive cancer behaviour. Altered KAI1 expression in prostate cancers and BPH associated with cancer may have important diagnostic roles.

Pancreatic cancer: factors regulating tumor development, maintenance and metastasis

Pancreatic cancer has one of the poorest prognoses of all gastrointestinal malignancies. Today, it is the fourth or fifth leading cause of cancer-related deaths in Western industrialized countries, and the incidence has been increasing throughout the past decades. Insensitivity to growth-inhibitory and apoptotic signals as well as self-sufficiency of growth-promoting factors are hallmarks of the pathogenesis of this malignancy. In pancreatic cancer, a variety of growth factors and their receptors are expressed at increased levels. For example, the concomitant presence of the epidermal growth factor (EGF) receptor and its ligand EGF is associated with enhanced tumor aggressiveness and shorter survival following tumor resection. Furthermore, a number of other growth factors and their receptors, such as nerve growth factor and its receptor, are overexpressed in pancreatic cancer and contribute to its malignant phenotype. Besides factors which directly promote cell proliferation, a variety of other factors such as galectins are upregulated, which influences the tumor environment and the invasiveness of pancreatic cancer cells. In addition, tumor suppressor genes such as KAI1 are expressed at reduced levels, thereby enhancing the ability of pancreatic cells to form metastases. A complex disturbance of factors is present in pancreatic cancer, resulting in a distinct growth advantage which clinically results in rapid tumor progression and poor patient survival.

Genetic mechanisms of hepatocarcinogenesis

The development of hepatocellular carcinoma (HCC) is a multistep process associated with changes in host gene expression, some of which correlate with the appearance and progression of tumor. Preneoplastic changes in gene expression result from altered DNA methylation, the actions of hepatitis B and C viruses, and point mutations or loss of heterozygosity (LOH) in selected cellular genes. Tumor progression is characterized by LOH involving tumor suppressor genes on many chromosomes and by gene amplification of selected oncogenes. The changes observed in different HCC nodules are often distinct, suggesting heterogeneity on the molecular level. These observations suggest that there are multiple, perhaps redundant negative growth regulatory pathways that protect cells against transformation. An understanding of the molecular pathogenesis of HCC may provide new markers for tumor staging, for assessment of the relative risk of tumor formation, and open new opportunities for therapeutic intervention.

Loss of KAI1/CD82 expression in bone and soft tissue tumors is not associated with lung metastasis

The KAI1 gene has been identified as a metastasis suppressor gene in human prostate cancer. Decrease or loss of KAI1/CD82 expression has been shown to be associated with poorer prognosis and metastasis in carcinomas of various organs. The purpose of this study was to examine whether KAI1/CD82 is expressed in bone and soft tissue tumors, and whether it is associated with metastasis to the lungs. Immunohistochemically, KAI1/CD82 expression in benign and malignant soft tissue tumors was noted in 83% and 37% of cases, respectively. KAI1/CD82 was- also expressed in benign bone tumors and osteosarcomas in 67% and 36% of the cases, respectively. Four (40%) of 10 osteosarcoma cases with no lung metastasis and one (25%) of four osteosarcoma cases with lung metastasis were positive for KAI1/CD82, respectively. Metastasis of osteosarcoma cells to the lungs was not correlated with the loss of KAI1/CD82 in osteosarcoma cells.

Regulatory role of tetraspanin CD9 in tumor-endothelial cell interaction during transendothelial invasion of melanoma cells

Heterotypic interaction among tumor cells (TCs) and endothelial cells (ECs) may play a critical role during the vascular dissemination of neoplastic cells and during pathologic angiogenesis in tumors. To identify molecules involved in these processes, the distribution of vascular junctional proteins was first studied by immunofluorescence at sites of heterologous intercellular contact using TC-EC mosaic monolayers grown on 2-dimensional collagen. Several members of the tetraspanin superfamily, including CD9, CD81, and CD151, were found to localize at the TC-EC contact area. The localization of tetraspanins to the TC-EC heterologous contact area was also observed during the active transmigration of TCs across EC monolayers grown onto 3-dimensional collagen matrices. Dynamic studies by time-lapse immunofluorescence confocal microscopy showed an active redistribution of endothelial CD9 to points of melanoma insertion. Anti-CD9 monoclonal antibodies were found to specifically inhibit the transendothelial migration of melanoma cells; the inhibitory effect was likely caused by a strengthening of CD9-mediated heterotypic interactions of TCs to the EC monolayer. These data support a novel mechanism of tetraspanin-mediated regulation of TC transcellular migration independent of TC motility and growth during metastasis and a role for these molecules in the formation of TC-EC mosaic monolayers during tumor angiogenesis.

KAI1 metastasis suppressor gene is frequently down-regulated in cervical carcinoma

KAI1 is a metastasis suppressor gene located on human chromosome 11p11.2. It belongs to a structurally distinct family of cell surface glycoproteins. Decreased KAI1 expression has been observed in several common solid epithelial tumors, including prostatic, pancreatic, lung, hepatic, colorectal, ovarian, and esophageal cancers. A recent study also observed frequent loss of KAI1 expression in a number of squamous cell carcinomas of the cervix by immunohistochemical technique. To further confirm whether this gene is altered in this malignancy, we analyzed KAI1 expression in various stages of cervical carcinoma by a molecular method. Total cellular RNA was extracted from 84 primary invasive cervical carcinomas and 6 metastatic or recurrent lesions. cDNA was synthesized and was used for real-time quantitative polymerase chain reaction analysis. The level of KAI1 expression was obtained as the value of threshold cycle (Ct) and was quantitated with a comparative Ct method. In addition, paraffin blocks of the tumors were selected and prepared for immunohistochemical study with an anti-KAI1 polyclonal antibody, C-16. Both the real-time quantitative polymerase chain reaction method and immunohistochemical study revealed a frequent decrease in KAI1 expression in invasive cervical cancers and metastatic or recurrent lesions. However, the reduction in KAI1 was not related to progression of the disease. When tumor cell differentiation was analyzed, poorly differentiated tumors showed a greater decrease in KAI1 expression than well or moderately differentiated tumors (P < 0.001). Histologically, KAI1 loss was observed equally in both squamous cell carcinoma and adeno-/adenosquamous carcinoma. Since down-regulation of KAI1 occurs in both early and late stages of cervical cancer, we suggest that its involvement in the progression of this malignancy is an early event.

Overexpression of tetraspanin CO-029 in hepatocellular carcinoma

BACKGROUND/AIMS

The molecules involved in the progression of hepatocellular carcinoma (HCC) are not fully understood. The aim of this study was to elucidate the crucial genes involved in cancer progression and metastasis.

METHODS

Selectively expressed genes were screened using differential display analysis, and then further analyzed by real-time quantitative reverse-transcription polymerase chain reaction (RT-PCR) and immunohistochemistry.

RESULTS

Tetraspanin CO-029 was found to be frequently and significantly overexpressed in HCC. Real-time quantitative RT-PCR showed that the CO-029 mRNA level was 1.7 times higher (P=0.030) in cancerous tissues than in non-cancerous tissues. mRNA expression of the other tetraspanins, CD9 and CD82, was downregulated in HCC, especially in tumors with intrahepatic spreading (portal vein invasion and/or intrahepatic metastasis). In contrast, mRNA expression of CO-029 tended to be increased in cancerous tissue showing intrahepatic spreading compared with tumors without such spreading. Immunohistochemical analysis revealed that CO-029 was overexpressed in poorly differentiated HCCs compared with well to moderately differentiated tumors (P<0.001), and in HCCs showing intrahepatic spreading compared with those without spreading (P=0.019).

CONCLUSIONS

Our findings suggest that CO-029 has some roles in the promotion of metastasis of HCC.

Hepatocellular carcinoma--cause, treatment and metastasis

In the recent decades, the incidence of hepatocellular carcinoma (HCC) has been found to be increasing in males in some countries. In China, HCC ranked second of cancer mortality since 1990s. Hepatitis B and C viruses (HBV and HCV) and dietary aflatoxin intake remain the major causative factors of HCC. Surgery plays a major role in the treatment of HCC, particularly for small HCC. Down-staging unresectable huge HCC to smaller HCC and followed by resection will probably be a new approach for further study. Liver transplantation is indicated for small HCC, however, some issues remain to be solved. Different modes of regional cancer therapy for HCC have been tried. Systemic chemotherapy has been disappointing in the past but the future can be promising. Biotherapy, such as cytokines, differentiation inducers, anti-angiogenic agents, gene therapy and tumor vaccine will probably play a role, particularly in the prevention of tumor recurrence. HCC invasiveness is currently the major target of study. Tremendous works have been done at the molecular level, which will provide clues for biomarker of HCC progression as well as targets for intervention.

Differential expression of metastasis-associated genes in papilla of vater and pancreatic cancer correlates with disease stage

PURPOSE

Papilla of Vater cancer has a much better prognosis than pancreatic cancer. It is not known whether this is the result of differences in the tumor biology of the two malignancies. Because metastasis formation is a critical step in tumor progression and a negative prognostic factor, we compared the expression of nm23-H1 and KAI1, two metastasis-suppressing genes, in papilla of Vater cancer and pancreatic cancer.

PATIENTS AND METHODS

Analysis was performed in nine normal human papilla of Vater samples, 27 papilla of Vater cancers, 16 normal pancreatic samples, and 29 pancreatic cancers. Expression of nm23-H1 and KAI1 was analyzed by Northern blot analysis and in situ hybridization. In addition, immunohistochemistry was performed to localize the respective proteins.

RESULTS

There was no difference in nm23-H1 and KAI1 mRNA expression levels in normal versus cancerous papilla of Vater samples. In contrast, nm23-H1 and KAI1 RNA expression was upregulated in early tumor stages of pancreatic cancer and reduced in advanced tumor stages. When expression of nm23-H1 and KAI1 RNA was analyzed by use of in situ hybridization, normal epithelial cells of the papilla of Vater exhibited mRNA staining intensity similar to that of papilla of Vater cancer cells. Similar levels of nm23-H1 and KAI1 immunoreactivity also were observed in these samples. In contrast, early stage pancreatic cancer samples exhibited stronger nm23-H1 and KAI1 immunoreactivity than normal controls. Furthermore, early pancreatic cancer stages exhibited higher KAI1 and nm23-H1 immunostaining than advanced tumor stages.

CONCLUSION

Differences in the expression patterns of the two tumor suppressor genes nm23-H1 and KAI1 may contribute to the different prognoses of papilla of Vater cancer and pancreatic cancer. Our findings support the hypothesis that biologic differences rather than earlier diagnosis influence the different outcomes of these two tumor entities.

Establishment of rat hepatocellular carcinoma cell lines with differing metastatic potential in nude mice

For better understanding of cancer metastasis, we have established an in vivo model for induction of highly metastatic hepatocellular carcinomas (HCC) in male F344 rats. From 1 tumor, 4 cell lines with differing metastatic potential (C1, C2, C6, C5F) were established by subcloning using the limited-dilution cloning technique. Two other lines, N1 and L2, arose from another primary HCC and a lung metastatic lesion, respectively. Although cell adhesion of each cell line in culture medium was different, tumors developing in the subcutis of nude mice after transplantation were all moderately differentiated HCC with a trabecular pattern. On subcutaneous injection into nude mice, all 6 cell lines proved to be tumorigenic in the injection site and C5F was highly metastatic to the lung. With injection into the tail vein, N1 and L2 formed frequent metastases in the lung as well as in lymph nodes. Using intraperitoneal injection, C1, C6, N1 and L2 showed marked disseminated growth in the abdominal cavity with bloody ascitis. Northern blot analysis revealed expression of known metastasis-related genes, KAI1 and heparanase, to be decreased in C5F, but no differences in expression of nm23-H1 were evident. A point mutation in the GSK-3beta phosphorylation site of the beta-catenin gene was found in L2. These transplantable HCC cell lines that have different metastatic ability should be useful for elucidation of mechanisms of metastasis.

KAI1 gene is differently expressed in papillary and pancreatic cancer: influence on metastasis

AIM:To compare KAI1 in cancer of papilla of Vater and pancreas to evaluate whether there are differences in biologic behavior which might account for prognosis.METHODS:We compared the expression in 24 papillay and 29 pancreatic cancers using Northern blot analysis, immunochemical assay and in situ hybridization, and investigated whether early diagnosis or molecular differences predict the outcome in these tumor entities.RESULTS:By Northern blot analysis there is no statistical difference of KAI1 levels in normal and cancerous papilla. No association between KAI1 mRNA expression and tumor stage or tumor differentiation was found in the tumors. By immunohistochemical assay, KAI1 staining in cytoplasm of papillary cancer cells was similar to that of normal papillary cells. By in situ hybridization, the results of KAI1 mRNA expression in normal and cancerous papilla were similar to those with immunohistochemical assay. The normal and cancerous pancreas tissues were also analyzed by the methods used in papillary samples.CONCLUSION:Although the biologic roles of KAI1 have not been clarified, our results suggest that KAI1 may restrict the progression of malignant papillary cancer, but its expression might not have any effect on the characteristics of papillary tumor, whereas by the analysis of KAI1 gene, its reduced expression is closely related to the progression and metastases of pancreatic cancer.