KAI1 gene suppresses invasion and metastasis of hepatocellular carcinoma MHCC97-H cells in vitro and in animal models

KAI1/CD82 gene and autotaxin-lysophosphatidic acid axis in gastrointestinal cancers

The KAI1/CD82 gene inhibits the metastasis of most tumors and is remarkably correlated with tumor invasion and prognosis. Cell metabolism dysregulation is an important cause of tumor occurrence, development, and metastasis. As one of the important characteristics of tumors, cell metabolism dysregulation is attracting increasing research attention. Phospholipids are an indispensable substance in the metabolism in various tumor cells. Phospholipid metabolites have become important cell signaling molecules. The pathological role of lysophosphatidic acid (LPA) in tumors was identified in the early 1990s. Currently, LPA inhibitors have entered clinical trials but are not yet used in clinical treatment. Autotaxin (ATX) has lysophospholipase D (lysoPLD) activity and can regulate LPA levels in vivo. The LPA receptor family and ATX/lysoPLD are abnormally expressed in various gastrointestinal tumors. According to our recent pre-experimental results, KAI1/CD82 might inhibit the migration and metastasis of cancer cells by regulating the ATX-LPA axis. However, no relevant research has been reported. Clarifying the mechanism of ATX-LPA in the inhibition of cancer metastasis by KAI1/CD82 will provide an important theoretical basis for targeted cancer therapy. In this paper, the molecular compositions of the KAI1/CD82 gene and the ATX-LPA axis, their physiological functions in tumors, and their roles in gastrointestinal cancers and target therapy are reviewed.

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.

Role of a metastatic suppressor gene KAI1/CD82 in the diagnosis and prognosis of breast cancer

Globally, breast cancer is the most common type of cancer in females and is one of the leading causes of cancer death in women. The advancement in the targeted therapies and the slight understanding of the molecular cascades of the disease have led to small improvement in the rate of survival of breast cancer patients. However, metastasis and resistance to the current drugs still remain as challenges in the management of breast cancer patients. Metastasis, potentially, leads to failure of the available treatment, and thereby, makes the research on metastatic suppressors a high priority. Tumor metastasis suppressors are several genes and their protein products that have the capability of arresting the metastatic process without affecting the tumor formation. The metastasis suppressors KAI1 (also known as CD82) has been found to inhibit tumor metastasis in various types of solid cancers, including breast cancer. KAI1 was identified as a metastasis suppressor that inhibits the process of metastasis by regulating several mechanisms, including cell motility and invasion, induction of cell senescence, cell–cell adhesion and apoptosis. KAI1 is a member of tetraspanin membrane protein family. It interacts with other tetraspanins, chemokines and integrins to control diverse signaling pathways, which are crucial for protein trafficking and intracellular communication. It follows that better understanding of the molecular events of such genes is needed to develop prognostic biomarkers, and to identify specific therapies for breast cancer patients. This review aims to discuss the role of KAI1/CD82 as a prognosticator in breast cancer.

The Inhibitory Effects of Recombinant Hespintor Combined with Sorafenib on Transplanted Human Hepatoma in Nude Mice, and Transcriptional Regulation of Hespintor Based on RNA-Seq

Objective: As targeted drugs, exogenous serpins could be introduced to patients to restore body balance. This study aimed to observe further the inhibitory effects of recombinant Hespintor (a Kazal-type serpin) combined with Sorafenib on transplanted human hepatoma tumors in nude mice specimens and to explore the possible transcriptional regulation by Hespintor. Methods: A model of human hepatoma tumors transplanted in nude mice was established, and the medication was administrated to observe the growth of the tumors. Four weeks after the drug administration, the tumors were removed to evaluate the inhibition effects of Hespintor on in-situ tumor growth and liver metastasis. The expression levels of MMP2, MMP9, Bax, Bcl-2, and caspase-3 in the tumor organizations were detected with Western blot. The target genes of the Hespintor were screened based on tissue RNA-Seq, and the regulatory network was constructed. Results: It was found that the recombinant Hespintor displayed a significant antitumor effect on the subcutaneous growth of MHCC97-H cells. Moreover, the therapeutic effects of the combination therapy were significantly better than those of single therapy. 10 target genes with significantly different expression by Hespintoron tumor tissue were identified. Finally, a visual regulatory networkwas constructed for target mRNA-pathway. Conclusions: The antitumor effect of Hespintor combined with Sorafenib in treating the subcutaneously implanted hepatocellular carcinoma tumors in nude mice was significant. The possible transcriptional regulation by Hespintor involved multiple signaling pathways, and it was not just the antitumor effect of uPA via its extracellular inhibitions.

Study on the hepatocellular carcinoma model with metastasis

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related death around the world due to advanced clinical stage at diagnosis, high incidence of recurrence and metastasis after surgical treatment. It is in urgent need to create appropriate animal models to explore the mechanism, patterns, risk factors, and therapeutic strategies of HCC metastasis and recurrence. However, most of the established models lack the phenotype of invasion and metastasis in patient, or have unstable phenotype. To establish HCC models with stable metastasis phenotype requires profound understanding in cancer metastasis biology and scientific methodology. Over the past 3 decades, HCC models with stable metastasis have been extensively studied. This paper reviewed the history and development of HCC animal models and cell models, focusing on the screening and maintaining of metastatic potential and phenotype. In-depth studies using these models vastly promote the understanding of cellular and molecular mechanisms and development of therapeutic strategies on HCC metastasis.

Establishment of rat liver cancer cell lines with different metastatic potential

The gloomy outcome of liver cancer is mainly due to the high rates of metastasis and recurrence, even after curative resection for early stage liver cancer. Our study was conducted to find the animal model suitable for the study of liver cancer metastasis. In our study, two liver cancer cells were obtained from N-nitrosodiethylamine (DEN) and N-nitrosomorpholine (NMOR) induced rats, and they were cultivated, screened and cloning cultivated. Bionomics of cells was analyzed. The results show that 2 cells had different metastatic potentiality. They were named Wrh-f2 and Wrh-s2, and they have the characteristics of Hepatocellular carcinoma cells. The bionomics of 2 cells showed: (1) The chromosome karyotype analysis showed that the mode of Wrh-f2 was 80–83 and Wrh-s2 was 55–57; (2) AFP positive cytoplasmic staining was observed in Wrh-f2 and Wrh-s2. Cytokeratin (CK) 7 and CK8 positive staining was present in Wrh-f2. CK8 positive staining was present in Wrh-s2; (3) The numbers of Wrh-f2 and Wrh-s2 that passed through the Transwells were 98 ± 12 and 55 ± 15;(4) Wrh-f2 had the significant higher colony formation (78%) than Wrh-s2(8%) (P < 0.01). (5) The animal models generated solid tumours when 2 cells were inoculated to nude mouse and rat. And Wrh-f2 developed stable pulmonary metastasis. The established cell lines with different metastatic potential showed obvious advantages over liver cancer in mimicking the biological properties of malignant liver cancer tumors. It provided a suitable model for the mechanism of liver cancer metastasis in vivo and in vitro.

The metastasis suppressor CD82/KAI1 represses the TGF-β 1 and Wnt signalings inducing epithelial-to-mesenchymal transition linked to invasiveness of prostate cancer cells

BACKGROUND

The epithelial-to-mesenchymal transition (EMT) is closely associated with cancer invasion and metastasis. Since the transforming growth factor β (TGF-β) and Wnt signals induce EMT in various epithelial cell types, we examined whether and how the CD82/KAI1 metastasis suppressor affects the TGF-β and Wnt signal-dependent EMT in human prostate cancer cells.

METHODS

The invasiveness of cancer cells was evaluated by examining their ability to pass through the basement membrane matrigel. The subcellular localizations of Smad4 and β-catenin proteins were respectively examined by confocal microscopy following immunofluorescence antibody staining and immunoblotting analysis following subcellular fractionation. The transcriptional activities of the TGF-β₁ -responsive TRE and Wnt-responsive Tcf/Lef promoters were determined by a luciferase reporter assay following transfection of the recombinant reporter vector into the cell.

RESULTS

TGF-β₁ and Wnt3a treatments of human prostate cancer cells without CD82 expression resulted in not only increased invasiveness but also EMT involving the development of motile structures, downregulation of E-cadherin, and upregulation of the mesenchymal proteins. However, in the cells with high levels of CD82, the TGF-β₁ and Wnt3a stimulations neither elevated invasiveness nor induced EMT. Furthermore, the TGF-β₁ signaling events occurring in the CD82-deficient cells, such as phosphorylation of Smad2, nuclear translocation of Smad4, and transactivation of the TRE promoter, did not take place in the high CD82-expressing cells. Further, high CD82 expression interfered with the Wnt signal-dependent alterations in the phosphorylation pattern of glycogen synthase kinase 3β (GSK-3β) in prostate cancer cells, which allowed GSK-3β to continue phosphorylating β-catenin, thereby attenuating the Wnt signaling effects on the nuclear translocation of β-catenin and subsequent transactivation of the Tcf/Lef promoter.

CONCLUSIONS

The results of the present study suggest that CD82/KAI1 functions in suppressing TGF-β₁ - and Wnt-induced EMT in prostate cancer cells by inhibiting the TGF-β₁ /Smad and Wnt/β-catenin pathways. Therefore, loss or decrease of CD82 expression is likely to render prostate cancer cells prone to respond to the TGF-β₁ and Wnt signals with EMT, resulting in the development of a motile and invasive mesenchymal phenotype related to the initiation of the metastatic cascade.

Tetraspanin CD82 represses Sp1-mediated Snail expression and the resultant E-cadherin expression interrupts nuclear signaling of β-catenin by increasing its membrane localization

Tetraspanin membrane proteins form physical complexes with signaling molecules and have been suggested to influence the signaling events of associated molecules. Of the tetraspanin proteins, CD82 has been shown to promote homotypic cell-cell adhesion, which partially accounts for its role in suppressing cancer invasion and metastasis. We found here that CD82-induced cell-cell adhesion is attributed to increased E-cadherin expression through CD82-mediated downregulation of the E-cadherin repressor Snail. The Snail repression by CD82 resulted from the reduced binding of the Sp1 transcription factor to the Snail gene promoter. Notably, high CD82 expression did not allow the fibronectin matrix to induce Sp1 phosphorylation, implicating CD82 inhibition of the fibronectin-integrin signaling-dependent Sp1 activation. Meanwhile, E-cadherin upregulated by CD82 pulled β-catenin up to the membrane region, and consequently reduced the amount of cytoplasmic β-catenin that was able to move into to the nucleus. The Wnt signal-induced nuclear translocation of β-catenin was also inhibited by the CD82 function of upregulating E-cadherin. Overall, high CD82 expression was likely to suppress fibronectin adhesion-induced Sp1 activation signaling for Snail expression, resulting in continuous E-cadherin expression, which contributed not only to the maintenance of strong cell-cell adhesion but also to the blockage of nuclear β-catenin signaling.

The metastasis suppressor CD82/KAI1 inhibits fibronectin adhesion-induced epithelial-to-mesenchymal transition in prostate cancer cells by repressing the associated integrin signaling

The transmembrane protein CD82/KAI1 suppresses the metastatic potential of various cancer cell types. Moreover, decrease or loss of CD82 expression is closely associated with malignancy and poor prognosis in many human cancers including prostate cancer. Despite intense scrutiny, the mechanisms underlying the metastasis-suppressing role of CD82 are still not fully understood. Here, we found that a fibronectin matrix induced mesenchymal phenotypes in human prostate cancer cells with no or low CD82 expression levels. However, high CD82 expression rendered prostate cancer cells to have intensified epithelial characteristics upon fibronectin engagement, along with decreased cell motility and invasiveness. The CD82 function of inhibiting fibronectin-induced epithelial-to-mesenchymal transition (EMT) was dependent not only on CD82 interactions with fibronectin-binding α₃β₁/α₅β₁ integrins but also on the integrin-mediated intracellular signaling events. Notably, CD82 attenuated the FAK-Src and ILK pathways downstream of the fibronectin-receptor integrins. Immunofluorescence staining of human prostate cancer tissue specimens illustrated a negative association of CD82 with EMT-related gene expression as well as prostate malignancy. Altogether, these results suggest that CD82 suppresses EMT in prostate cancer cells adhered to the fibronectin matrix by repressing adhesion signaling through lateral interactions with the associated α₃β₁ and α₅β₁ integrins, leading to reduced cell migration and invasive capacities.

Differential tumor biological role of the tumor suppressor KAI1 and its splice variant in human breast cancer cells

The tetraspanin and tumor suppressor KAI1 is downregulated or lost in many cancers which correlates with poor prognosis. KAI1 acts via physical/functional crosstalk with other membrane receptors. Also, a splice variant of KAI1 (KAI1-SP) has been identified indicative of poor prognosis. We here characterized differential effects of the two KAI1 variants on tumor biological events involving integrin (αvß3) and/or epidermal growth factor receptor (EGF-R). In MDA-MB-231 and -435 breast cancer cells, differential effects were documented on the expression levels of the tumor biologically relevant integrin αvß3 which colocalized with KAI1-WT but not with KAI1-SP. Cellular motility was assessed by video image processing, including motion detection and vector analysis for the quantification and visualization of cell motion parameters. In MDA-MB-231 cells, KAI1-SP provoked a quicker wound gap closure and higher closure rates than KAI1-WT, also reflected by different velocities and average motion amplitudes of singular cells. KAI1-SP induced highest cell motion adjacent to the wound gap borders, whereas in MDA-MB-435 cells a comparable induction of both KAI1 variants was noticed. Moreover, while KAI1-WT reduced cell growth, KAI1-SP significantly increased it going along with a pronounced EGF-R upregulation. KAI1-SP-induced cell migration and proliferation was accompanied by the activation of the focal adhesion and Src kinase. Our findings suggest that splicing of KAI1 does not only abrogate its tumor suppressive functions, but even more, promotes tumor biological effects in favor of cancer progression and metastasis.

The metastasis suppressor CD82/KAI1 regulates cell migration and invasion via inhibiting TGF-β 1/Smad signaling in renal cell carcinoma

The tetraspanin KAI1/CD82 was identified as a tumor metastasis suppressor that downregulated in various malignant cell types. However, the function of CD82 and its underlying anti-metastasis role in renal cell carcinoma (RCC) is still unraveled. Here, we investigated the expression of CD82 in RCC and explored its regulatory mechanism in RCC cell lines. We found that CD82 was down-regulated in RCC tissues and cells and its expression was significantly associated with histological grade(p=0.041), tumour stage (p=0.036) and tumor size(p=0.020) by analyzing tissue microarrays. After upregulation of CD82 through lentivirus, reduced ability of migration and invasion in Caki-1 cells were detected. In contrast, gene silencing of CD82 by small interfering RNA promoted metastatic and invasive potential of 786-O cells. Furthermore, Western blot was performed to identify the influence of CD82 on MMP family and TGF-β1/Smad pathway in RCC. Subsequently, upregulating protein level of TGF-β1 with the overexpression of CD82 could rescue the malignant behaviors inhibited by CD82 which indicated that CD82 played its inhibitory role in RCC partially by attenuating the expression of TGF-β1. Taken together, CD82 played a prominent role in migration and invasion of RCC cells and it might exhibit its inhibitory role in RCC metastasis via block TGF-β1/Smad signaling pathway.

Overexpression of KAI1 inhibits retinoblastoma metastasis in vitro

The present study aimed to investigate the expression of cluster of differentiation 82 (KAI1), a gene involved in the suppression of tumor metastasis, in human retinoblastoma (RB) tissue and to study the effect of KAI1 expression on RB cell migration and invasion. KAI1 expression was examined in 26 patients with non-invasive and invasive retinoblastoma using reverse transcription-quantitative polymerase chain reaction and western blot analysis. A lentiviral vector containing KAI1 cDNA was used to transfect the two RB cell lines, HXO-Rb44-Gl and Y79. Following successful transfection, the migratory and invasive capacity of the two RB cell lines was evaluated using a Transwell^® migration assay. KAI1 expression was observed to be downregulated in invasive RB compared to non-invasive RB. The migratory and invasive capacities of KAI1 transfected cell lines were significantly decreased compared to those of the control cells. KAI1 may be involved in retinoblastoma metastasis, and increased expression of KAI1 significantly inhibits the metastatic ability of RB cells in vitro.

Promoter CpG-Site Methylation of the KAI1 Metastasis Suppressor Gene Contributes to Its Epigenetic Repression in Prostate Cancer

BACKGROUND

Repression of the KAI1 metastasis suppressor gene is closely associated with malignancy and poor prognosis in many human cancer types including prostate cancer. Since gene repression in human cancers frequently results from epigenetic alterations by DNA methylation and histone modifications, we examined whether the KAI1 gene becomes silenced through these epigenetic mechanisms in prostate cancer.

METHODS

KAI1 mRNA and protein levels were determined by RT-PCR and immunoblotting analyses, respectively. Methylation status of the KAI1 promoter DNA in prostate cancer cell lines and tissues was evaluated by methylation-specific PCR analysis of bisulfite-modified genomic DNAs. Methylated CpG sites in the KAI1 promoter were identified by sequencing the PCR clones of the bisulfite-modified KAI1 promoter DNA. KAI1 protein levels in human prostate cancer tissue samples were examined by immunofluorescence staining of the tissues with an anti-KAI1 antibody.

RESULTS

Among the three human prostate cancer cell lines examined, PC3 and DU145 cells exhibited markedly decreased levels of KAI1 mRNA and protein as compared to LNCaP cells, even though the exogenous KAI1 promoter not being methylated was normally functional in all these cell lines. Treatment of the low KAI1-expressing cell lines with a demethylating agent, 5'-aza-2'-deoxycytidine, significantly elevated KAI1 expression levels, implicating the involvement of DNA methylation in KAI1 downregulation. Methylation of CpG islands within the KAI1 promoter region was observed in the low KAI1-expressing cells, but not in the high KAI1-expressing cells. Also, methyl CpG-binding proteins such as MBD2 and MeCP2 were complexed to the KAI1 promoter in the low KAI1-expressing cells. Bisulfite sequencing analysis identified the intensively methylated CpG residues in the KAI1 promoter clones derived from prostate cancer cells and tissues with no or low KAI1 expression. As in prostate cancer cell lines, prostate cancer tissues from patients also displayed a negative association between KAI1 expression levels and methylation status of the KAI1 promoter.

CONCLUSIONS

The present data suggest that the KAI1 gene might be repressed by epigenetic alterations through the promoter CpG-site methylation during prostate cancer progression. This epigenetic mechanism could provide a clue for understanding how the KAI1 gene was silenced in metastatic prostate cancers. Prostate 77: 350-360, 2017. © 2016 Wiley Periodicals, Inc.

Tetraspanin CD82: a suppressor of solid tumors and a modulator of membrane heterogeneity

Tetraspanin CD82 suppresses the progression and metastasis of a wide range of solid malignant tumors. However, its roles in tumorigenesis and hematopoietic malignancy remain unclear. Ubiquitously expressed CD82 restrains cell migration and cell invasion by modulating both cell-matrix and cell-cell adhesiveness and confining outside-in pro-motility signaling. This restraint at least contributes to, if not determines, the metastasis-suppressive activity and, also likely, the physiological functions of CD82. As a modulator of cell membrane heterogeneity, CD82 alters microdomains, trafficking, and topography of the membrane by changing the membrane molecular landscape. The functional activities of membrane molecules and the cytoskeletal interaction of the cell membrane are subsequently altered, followed by changes in cellular functions. Given its pathological and physiological importance, CD82 is a promising candidate for clinically predicting and blocking tumor progression and metastasis and also an emerging model protein for mechanistically understanding cell membrane organization and heterogeneity.

Alternative splicing of KAI1 abrogates its tumor-suppressive effects on integrin αvβ3-mediated ovarian cancer biology

Loss or downregulation of the tumor-suppressor KAI1 correlates with poor cancer patient prognosis. KAI1 functions by interacting with other proteins, including integrin cell adhesion and signaling receptors. We previously showed that KAI1 physically and functionally crosstalks with the tumor-biologically relevant integrin αvβ3, thereby suppressing ovarian cancer cell migration and proliferation. Interestingly, in metastases, a KAI1 splice variant had been identified, indicating poor patient prognosis. Thus, we here characterized differential effects of the two KAI1 proteins upon their cellular restoration. Opposite to KAI1, KAI1-splice reduced αvβ3-mediated cell adhesion, thereby inducing cell migration. This was accompanied by elevated αvβ3 levels and drastically elevated focal adhesion kinase activation, however, without any obvious colocalization with αvβ3, as observed for KAI1. Moreover, codistribution of KAI1 with the cell/cell-adhesion molecule E-cadherin was abrogated in KAI1-splice. Whereas KAI1 diminished cell proliferative activity, KAI1-splice prominently enhanced cell proliferation concomitant with elevated transcription and cell-surface expression of the epidermal growth factor receptor. Thus KAI1-splice does not only counteract the tumor-suppressive actions of KAI1, but - beyond that - promotes αvβ3-mediated biological functions in favor of tumor progression and metastasis.

Double lethal effects of fusion gene of wild-type p53 and JunB on hepatocellular carcinoma cells

This study explored the double lethal effects of pEGFP-C1-wtp53/junB fusion gene on hepatocellular carcinoma (HCC) cells. wtp53/junB fusion gene was constructed and transformed into HepG2 cell line. Expression of KAI1 was detected by quantitative real-time PCR and Western blotting, cells apoptosis rate was detected by flow cytometry, proliferation of cells was detected byMTT chromometry, cell transmigration was detected by using transwell systems. The results showed that after transformation with pEGFP-C1-wtp53/JunB, the expression level of KAI1 protein was up-regulated, being 8.13 times the blank control group in HepG2 cells and significantly higher than 2.87 times which transformed with pEGFP-C1-JunB, 3.11 times which transformed with pEGFP-C1-wtp53 (P<0.001). Apoptosis rate of HepG2 cells transformed with pEGFP-C1-wtp53/JunB was significantly higher than that of other groups (P<0.001), and invasive ability of HepG2 cells transformed with pEGFP-C1-wtp53/JunB was significantly lower than other groups(P<0.001). It was concluded that the fusion gene of wtp53 and JunB could not only inhibit the growth of hepatoma cells and promote tumor cell apoptosis, but also suppress the invasive ability of tumor cells by up-regulating the expression of KAI1.

Expression characteristics of KAI1 and vascular endothelial growth factor and their diagnostic value for hepatocellular carcinoma

BACKGROUND/AIMS

We tried to investigate the expression characteristics of KAI1, a suppressor of wide-spectrum tumor metastasis, and vascular endothelial growth factor (VEGF), the most common angiogenesis factor, and then to analyze their diagnostic value for hepatocellular carcinoma (HCC).

METHODS

The protein and mRNA expression levels of KAI1 or VEGF in HCC tissues and in self-controlled para-carcinoma tissues were analyzed by Western blot and real-time polymerase chain reaction, respectively. Serum levels of KAI1 and VEGF in the patients with HCC, benign liver disease or in healthy controls were quantitatively detected by enzyme-linked immunosorbent assay.

RESULTS

The expression level of KAI1 was downregulated, while the expression level of VEGF was upregulated in the tissues or serum of the patients with HCC. The expression level of serum KAI1 in HCC patients was correlated with TNM staging, intrahepatic metastasis, lymph node or peritoneal metastasis, and portal vein thrombus. In addition to the factors that were correlated with KAI1 expression, VEGF expression was also closely related to the α-fetoprotein level of the patients. The area under the receiver operating characteristic curve for the diagnosis of HCC was 0.907 for KAI1 and 0.779 for VEGF. The sensitivity of serum KAI1 levels in the diagnosis of HCC was 86.96%; the accuracy was 83.06%, while the sensitivity, the accuracy and the negative predictive value were improved to 91.86%, 84.68%, and 78.79% according to the combined detection of KAI1 and VEGF, respectively.

CONCLUSIONS

A combined detection of KAI1 and VEGF may greatly improve the efficiency of diagnosis and form a reliable panel of diagnostic markers for HCC.

Expression characteristics of KAI1 and vascular endothelial growth factor and their diagnostic value for hepatocellular carcinoma

BACKGROUND/AIMS

We tried to investigate the expression characteristics of KAI1, a suppressor of wide-spectrum tumor metastasis, and vascular endothelial growth factor (VEGF), the most common angiogenesis factor, and then to analyze their diagnostic value for hepatocellular carcinoma (HCC).

METHODS

The protein and mRNA expression levels of KAI1 or VEGF in HCC tissues and in self-controlled para-carcinoma tissues were analyzed by Western blot and real-time polymerase chain reaction, respectively. Serum levels of KAI1 and VEGF in the patients with HCC, benign liver disease or in healthy controls were quantitatively detected by enzyme-linked immunosorbent assay.

RESULTS

The expression level of KAI1 was downregulated, while the expression level of VEGF was upregulated in the tissues or serum of the patients with HCC. The expression level of serum KAI1 in HCC patients was correlated with TNM staging, intrahepatic metastasis, lymph node or peritoneal metastasis, and portal vein thrombus. In addition to the factors that were correlated with KAI1 expression, VEGF expression was also closely related to the α-fetoprotein level of the patients. The area under the receiver operating characteristic curve for the diagnosis of HCC was 0.907 for KAI1 and 0.779 for VEGF. The sensitivity of serum KAI1 levels in the diagnosis of HCC was 86.96%; the accuracy was 83.06%, while the sensitivity, the accuracy and the negative predictive value were improved to 91.86%, 84.68%, and 78.79% according to the combined detection of KAI1 and VEGF, respectively.

CONCLUSIONS

A combined detection of KAI1 and VEGF may greatly improve the efficiency of diagnosis and form a reliable panel of diagnostic markers for HCC.

Amplification of MPZL1/PZR promotes tumor cell migration through Src-mediated phosphorylation of cortactin in hepatocellular carcinoma

We have previously identified 1 241 regions of somatic copy number alterations (CNAs) in hepatocellular carcinoma (HCC). In the present study, we found that a novel recurrent focal amplicon, 1q24.1-24.2, targets the MPZL1 gene in HCC. Notably, there is a positive correlation between the expression levels of MPZL1 and intrahepatic metastasis of the HCC specimens. MPZL1 can significantly enhance the migratory and metastatic potential of the HCC cells. Moreover, we found that one of the mechanisms by which MPZL1 promotes HCC cell migration is by inducing the phosphorylation and activation of the pro-metastatic protein, cortactin. Additionally, we found that Src kinase mediates the phosphorylation and activation of cortactin induced by MPZL1 overexpression. Taken together, these findings suggest that MPZL1 is a novel pro-metastatic gene targeted by a recurrent region of copy number amplification at 1q24.1-24.2 in HCC.

Papillary carcinoma of the thyroid: high expression of COX-2 and low expression of KAI-1/CD82 are associated with increased tumor invasiveness

BACKGROUND

We have previously demonstrated that expression of COX-2 is upregulated by hepatocyte growth factor in thyroid papillary carcinoma (TPC) cells and is associated with increased invasiveness of tumor cells. COX-2 upregulation was associated with downregulation of KAI-1/CD82, a metastasis suppressor molecule that has been associated with the metastatic potential of several solid tumors. In the present study, we have investigated the possibility that downregulation of KAI-1/CD82 may contribute to the invasiveness of papillary carcinoma cells.

METHODS

Expression of KAI-1/CD82 and its relation to COX-2 levels were investigated in 6 primary cultures of TPC, in 2 tumor cell lines (TPC-1 and K1), and in 55 tumor samples of TPC. The biological role of KAI-1/CD82 in regulating tumor invasiveness was investigated in TPC cell lines and primary cultures transfected with a pCDNA3.1/Hygro.KAI-1; transfected cells were tested in functional studies of cell migration and invasiveness. Finally, the role of KAI-1/CD82 in influencing TPC metastasis was investigated in vivo using nu/nu mice injected with K1-transfected cells.

RESULTS

We provide evidence that COX-2 and KAI-1/CD82 are inversely regulated in TPC primary cultures and in TPC-1 tumor cells. In fact, inhibition of COX-2 with NS398 is associated with a 2-9-fold upregulation of KAI-1/CD82 RNA. Moreover, a possible relation between COX-2 and KAI-1/CD82 was confirmed by the presence of a statistically significant inverse correlation in the expression of the two genes in 55 tumor samples of TPC (r = -0.513; p = 0.001). In 36 of 55 cases, tumor areas contained lower levels of KAI-1/CD82 RNA as compared with the corresponding normal tissue. Low expression of KAI-1/CD82 RNA in the tumor area was associated with extrathyroid extension of the disease in 16 of 19 cases (p < 0.04) and with lymph node metastasis in 11 of 14 cases (not significant). KAI-1/CD82 re-expression in tumor cells was associated with a significant decrease in their migratory (50-76% reduction) and invasive (46-65% reduction) capacity, even after hepatocyte growth factor stimulation. Finally, nu/nu mice injected with KAI-1/CD82-transfected K1 TPC cells developed fewer and smaller metastasis as compared with mice injected with vector-transfected K1 cells (p=0.016).

CONCLUSION

Our findings raise the possibility that downregulation of KAI-1/CD82 in TPC cells is one of the molecular mechanisms regulating their invasive and metastatic potential.

Identification of the tetraspanin CD82 as a new barrier to xenotransplantation

Significant immunological obstacles are to be negotiated before xenotransplantation becomes a clinical reality. An initial rejection of transplanted vascularized xenograft is attributed to Galα1,3Galβ1,4GlcNAc-R (Galα1,3-Gal)-dependent and -independent mechanisms. Hitherto, no receptor molecule has been identified that could account for Galα1,3-Gal-independent rejection. In this study, we identify the tetraspanin CD82 as a receptor molecule for the Galα1,3-Gal-independent mechanism. We demonstrate that, in contrast to human undifferentiated myeloid cell lines, differentiated cell lines are capable of recognizing xenogeneic porcine aortic endothelial cells in a calcium-dependent manner. Transcriptome-wide analysis to identify the differentially expressed transcripts in these cells revealed that the most likely candidate of the Galα1,3-Gal-independent recognition moiety is the tetraspanin CD82. Abs to CD82 inhibited the calcium response and the subsequent activation invoked by xenogeneic encounter. Our data identify CD82 on innate immune cells as a major "xenogenicity sensor" and open new avenues of intervention to making xenotransplantation a clinical reality.

Dissecting the diverse functions of the metastasis suppressor CD82/KAI1

The recent identification of metastasis suppressor genes, the products of which inhibit metastasis but not primary tumor growth, distinguishes oncogenic transformation and tumor suppression from a hallmark of malignancy, the ability of cancer cells to invade sites distant from the primary tumor. The metastasis suppressor CD82/KAI1 is a member of the tetraspanin superfamily of glycoproteins. CD82 suppresses metastasis by multiple mechanisms including inhibition of cell motility and invasion, promotion of cell polarity as well as induction of senescence and apoptosis in response to extracellular stimuli. A common feature of these diverse effects is CD82 regulation of membrane organization as well as protein trafficking and interactions, which affects cellular signaling and intercellular communication.

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.

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

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

Novel role for epidermal growth factor-like domain 7 in metastasis of human hepatocellular carcinoma

Epidermal growth factor-like domain 7 (Egfl7) is a recently identified secreted protein that is believed to be primarily expressed in endothelial cells (ECs). Although its expression was reported elevated during tumorigenesis, whether and how Egfl7 contributes to human malignancies remains unknown. In the present study overexpression of Egfl7 was found predominantly in hepatocellular carcinoma (HCC) cells in HCC tissues and closely correlated with poor prognosis of HCC. The expression of Egfl7 in cancer cells was further verified with HCC cell lines including HepG2, MHCC97-L, and HCCLM3, and the Egfl7 expression levels positively correlated with metastatic potential of HCC cell lines was tested. To functionally characterize Egfl7 in HCC, we depleted its expression in HCCLM3 cells by using small interfering RNA. Interestingly, reduction of Egfl7 expression resulted in significant inhibition of migration but not growth of HCCLM3 cells. Biochemical analysis indicated that Egfl7 could facilitate the phosphorylation of focal adhesion kinase (FAK) and therefore promote the migration of HCCLM3 cells. In addition, this effect was almost completely blocked by inhibition of epidermal growth factor receptor (EGFR), indicating that the activation of FAK by Egfl7 is mediated through EGFR. Finally, we used a mouse model to demonstrate that down-regulation of Egfl7 was associated with suppression of intrahepatic and pulmonary metastases of HCC. Collectively, our study shows for the first time that overexpression of Egfl7 in HCC and Egfl7 promotes metastasis of HCC by enhancing cell motility through EGFR-dependent FAK phosphorylation.

CONCLUSION

Our study suggests Egfl7 as a novel prognostic marker for metastasis of HCC and a potential therapeutic target.

Screening and identification of novel B cell epitopes in human heparanase and their anti-invasion property for hepatocellular carcinoma

BACKGROUND

The aim of this study was to screen and identify novel B cell epitopes within the human heparanase protein and to investigate the impact of self-developed anti-heparanase polypeptide antibodies on growth and invasion of HCCLM6 human hepatocellular carcinoma cells in vitro.

METHODS

The flexible regions of secondary structure and the B cell epitopes of the human heparanase amino acid sequence were predicted by DNAStar and Bcepred software.The multiple antigenic peptides (MAP) of the epitopes were synthesized in eight-branched form. Rabbits were immunized with the eight-branched MAPs mixed with the universal T-helper epitope human IL-1beta peptide (VQGEESNDK, amino acid 163-171). The immunogenicity of the synthesized peptides was evaluated by ELISA, western blot and immunohistochemistry. The impact of the self-developed rabbit anti-heparanase polyclonal antibodies on growth and invasion ability of HCCMLM6 cells were analyzed in a cell culture model. The cells were first treated with one of the three antibodies, respectively, and then measured by using MTT, flow cytometry, plate clone formation, invasion assay and heparan sulfate degrading enzyme assay.

RESULTS

The three amino acid sequences 1-15 (MAP1), 279-293 (MAP2), and 175-189 (MAP3) in the large subunit of the human heparanase protein were predicted as its most potential epitopes. ELISA, western blot and immunohistochemistry analysis showed that all three MAPs were capable to induce high titer of serum antibodies. Antibodies induced by MAP1 and MAP2 were high specific. Furthermore, anti-MAP2 antibodies showed the strongest avidity towards liver cancer tissues. Under the treatment with the three anti-heparanase antibodies, respectively, the growth, cell cycle and clone formation of the cells remained unchanged when compared with a treatment with normal rabbit IgG. However, an inhibition of cell invasiveness and heparanase activity could be detected under the treatment with anti-MAP1- or anti-MAP2-antibody (with a terminal concentration of 100 mug/ml). The cell invasiveness was decreased by 54 and 38%, respectively, the heparanase activity by 43 and 39%, respectively.

CONCLUSION

The multiple antigenic peptides MAP1 (AC 1-15) and MAP2 (AC 279-293) may be the dominant B cell epitopes in the human heparanase protein. The induced polypeptide antibodies can effectively inhibit the heparanase activity of HCCLM6 liver cancer cells and therefore influence their invasion ability, which provides a theoretic basis for the development of anti-heparanase antibodies and their clinical use as vaccine.

The complex biology of autocrine motility factor/phosphoglucose isomerase (AMF/PGI) and its receptor, the gp78/AMFR E3 ubiquitin ligase

Phosphoglucose isomerase (PGI) is a glycolytic enzyme that exhibits a dual function as an extracellular cytokine, under the name autocrine motility factor (AMF). Its cell surface receptor, gp78/AMFR, is also localized to the endoplasmic reticulum where it functions as an E3 ubiquitin ligase. Expression of both AMF/PGI and gp78/AMFR is associated with cancer and, in this review, we will discuss various aspects of the biology of this ligand-receptor complex and its role in tumor progression.

Expression profiling of supraglottic carcinoma: PTEN and thrombospondin 2 are associated with inhibition of lymphatic metastasis

CONCLUSION

Down-regulation of metastasis inhibitor genes PTEN and thrombospondin 2 may play a role in the lymphatic metastasis of supraglottic carcinoma.

OBJECTIVES

To investigate differentially expressed genes in supraglottic squamous cell carcinoma with and without lymphatic metastasis using cDNA microarray.

MATERIALS AND METHODS

cDNA microarray was used to detect the expression profiles of supraglottic carcinoma and the results were validated with real-time PCR.

RESULTS

Compared with normal laryngeal tissues, the expression of 15.6% (15/96) genes including cathepsin B, cathepsin D, cathepsin L, Ets1, c-Ets2, and PEA3 were up-regulated in both cases of supraglottic carcinoma. Compared with the supraglottic carcinoma with no lymph node metastasis, the expression of metastasis inhibitor genes PTEN and thrombospondin 2 was down-regulated in the supraglottic carcinoma tissue with lymph node metastasis.

Controlling cell surface dynamics and signaling: how CD82/KAI1 suppresses metastasis

The recent identification of metastasis suppressor genes, uniquely responsible for negatively controlling cancer metastasis, are providing inroads into the molecular machinery involved in metastasis. While the normal function of a few of these genes is known; the molecular events associated with their loss that promotes tumor metastasis is largely not understood. KAI1/CD82, whose loss is associated with a wide variety of metastatic cancers, belongs to the tetraspanin family. Despite intense scrutiny, many aspects of how CD82 specifically functions as a metastasis suppressor and its role in normal biology remain to be determined. This review will focus on the molecular events associated with CD82 loss, the potential impact on signaling pathways that regulate cellular processes associated with metastasis, and its relationship with other metastasis suppressor genes.