Broad-spectrum metastasis suppressing compounds and therapeutic uses thereof in human tumors

Previously, we have identified a novel human metastasis-inducing lncRNA (named SKAI1BC), that suppresses the KAI1/CD82 metastasis-suppressing gene and is upregulated in triple negative breast cancer and melanoma derived cell lines. Modeling of the SKAI1BC lncRNA secondary structure and its potential interaction with Inforna compounds, led us to identify several compounds that might bind the SKAI1BC lncRNA. We found that these compounds inhibit metastasis invasion and cell migration in culture, in all eight types of solid human cancers tested: several of which are the most lethal and/or frequent human malignancies. Moreover, in most cases, the mechanism of action of several of our compounds involves enhancement of KAI1/CD82 RNA level depending on the specific compound and the human tumor type. With the epigenetic inactivation of KAI1/CD82 in at least ten additional solid human cancers, this implies a very good chance to broaden the spectrum of human cancers affected by our compounds. This is the first time that modeling of a large lncRNA (> 700 bp) secondary structure followed by its potential interaction with Inforna like compounds database has led to the identification of potential biologically active small molecule drugs.

miRNA-633 and KAI1 as Potential Biomarkers of Malignant Melanoma with Gastric Cancer

OBJECTIVE

Malignant melanoma with gastric cancer is one of the most malignant tumors. However, there have been no reports on the effects of KAI1 and miRNA-633 on the survival and prognosis of patients with malignant melanoma with gastric cancer.

METHODS

Fifty patients with malignant melanoma and gastric cancer were collected from October 2017 to December 2019. The clinical parameters included clinical information, such as sex, age, tumor size, and tumor staging. RT-qPCR was used to detect the expression of KAI1 and miRNA- 633. The role of KAI1 and miRNA-633 on the overall survival of melanoma was explored by the Pearson chi-square test, Spearman-rho correlation test, Univariate and multivariate cox regression analyses, and Kaplan-Meier method. Furthermore, the bioinformatic analysis was used to verify the role of KAI1 and miRNA-633 on malignant melanoma with gastric cancer.

RESULTS

The expression of KAI1 and miRNA-633 was significantly related with the tumor size and staging of tumor (p<0.05) based on the Pearson chi-square test. Spearman's correlation coefficient displayed that KAI1 was significantly correlated with the miRNA-633 (ρ=-0.439, p=0.001). The result of multivariate cox proportional regression analysis showed that KAI1 (HR =0.109, 95% CI: 0.031-0.375, p< 0.001), and miRNA-633 (HR = 13.315, 95% CI: 3.844-46.119, p<0.001) were significantly associated with overall survival.

CONCLUSION

The low expression level of KAI1 and high expression of miRNA-633 are significantly correlated with the poor overall survival prognosis of malignant melanoma with gastric cancer, to provide a basis for KAI1 and miRNA-633 to become novel molecular targets for malignant melanoma with gastric cancer.

KAI1(CD82) is a key molecule to control angiogenesis and switch angiogenic milieu to quiescent state

BACKGROUND

Little is known about endogenous inhibitors of angiogenic growth factors. In this study, we identified a novel endogenous anti-angiogenic factor expressed in pericytes and clarified its underlying mechanism and clinical significance.

METHODS

Herein, we found Kai1 knockout mice showed significantly enhanced angiogenesis. Then, we investigated the anti-angiogenic roll of Kai1 in vitro and in vivo.

RESULTS

KAI1 was mainly expressed in pericytes rather than in endothelial cells. It localized at the membrane surface after palmitoylation by zDHHC4 enzyme and induced LIF through the Src/p53 pathway. LIF released from pericytes in turn suppressed angiogenic factors in endothelial cells as well as in pericytes themselves, leading to inhibition of angiogenesis. Interestingly, KAI1 had another mechanism to inhibit angiogenesis: It directly bound to VEGF and PDGF and inhibited activation of their receptors. In the two different in vivo cancer models, KAI1 supplementation significantly inhibited tumor angiogenesis and growth. A peptide derived from the large extracellular loop of KAI1 has been shown to have anti-angiogenic effects to block the progression of breast cancer and retinal neovascularization in vivo.

CONCLUSIONS

KAI1 from PC is a novel molecular regulator that counterbalances the effect of angiogenic factors.

Differential HLA Association of GAD65 and IA2 Autoantibodies in North Indian Type 1 Diabetes Patients

The human leucocyte antigen (HLA) association with type 1 diabetes (T1D) is well known but there are limited studies investigating the association between β-cell autoantibodies and HLA genes. We evaluated the prevalence of GAD65 and IA-2 autoantibodies (GADA and IA2A) in 252 T1D patients from North India and investigated the genetic association of GADA and IA2A with HLA class I and class II genes/haplotypes. GADA and IA2A were detected in 50.79% and 15.87% of T1D patients, respectively, while only 8.73% had both GADA and IA2A. HLA-DRB1^∗03 was observed to be significantly higher in GADA+ T1D patients as compared to GADA- (91.41% vs. 66.13%, Bonferroni-corrected P (P _c) = 1.11 × 10^-5; OR = 5.45; 95% CI: 2.67-11.08). Similarly, HLA-DQB1^∗02 was found to be significantly increased in GADA+ patients (94.53%, P _c = 2.19 × 10^-5; OR = 6.27; 95% CI: 2.7-14.49) as compared to GADA- (73.39%). The frequencies of HLA-DRB1^∗04 and DQB1^∗03 were increased in IA2A+ patients (45.0% and 52.5%, respectively) as compared to that in IA2A- (25.94% and 33.96%, respectively). Further, the frequency of DRB1^∗03-DQB1^∗02 haplotype was found to be significantly increased in GADA+ T1D patients as compared to GADA- (60.55% vs. 41.94%, P = 3.94 × 10^-5; OR = 2.13; 95%CI = 1.49-3.03). Similarly, HLA-DRB1^∗04-DQB1^∗03 haplotype was found to be significantly increased in IA2A+ T1D patients compared to IA2A- patients (22.5% vs. 12.97%; P = 0.041; OR = 1.95; 95%CI = 1.08-3.52). None of the HLA class I genes (HLA-A, B, and Cw) was found to be associated with GADA or IA2A in people with T1D. Our findings suggest that HLA-DRB1^∗03/DQB1^∗02 and HLA-DRB1^∗04/DQB1^∗03 might play an important role in the development of GADA and IA2A, respectively.

Metabolomic Detection Between Pancreatic Cancer and Liver Metastasis Nude Mouse Models Constructed by Using the PANC1-KAI1/CD82 Cell Line

Background: Pancreatic cancer (PC) has a poor prognosis and is prone to liver metastasis. The KAI1/CD₈₂ gene inhibits PC metastasis. This study aimed to explore differential metabolites and enrich the pathways in serum samples between PC and liver metastasis nude mouse models stably expressing KAI1/CD₈₂. Methods: KAI1/CD₈₂-PLV-EF1α-MCS-IRES-Puro vector and PANC1 cell line stably expressing KAI1/CD₈₂ were constructed for the first time. This cell line was used to construct 3 PC nude mouse models and 3 liver metastasis nude mouse models. The different metabolites and Kyoto encyclopedia of genes and genomes (KEGG) and human metabolome database (HMDB) enrichment pathways were analyzed using the serum samples of the 2 groups of nude mouse models on the basis of untargeted ultra-performance liquid chromatography-tandem mass spectrometry platform. Results: KAI1/CD₈₂-PLV-EF1α-MCS-IRES-Puro vector and PANC1 cell line stably expressing KAI1/CD₈₂ were constructed successfully, and all nude mouse models survived and developed cancers. Among the 1233 metabolites detected, 18 metabolites (9 upregulated and 9 downregulated) showed differences. In agreement with the literature data, the most significant differences between both groups were found in the levels of bile acids (taurocholic acid, chenodeoxycholic acid), glycine, prostaglandin E2, vitamin D, guanosine monophosphate, and inosine. Bile recreation, primary bile acid biosynthesis, and purine metabolism KEGG pathways and a series of HMDB pathways (P < .05) contained differential metabolites that may be associated with liver metastasis from PC. However, the importance of these metabolites on PC liver metastases remains to be elucidated. Conclusions: Our findings suggested that the metabolomic approach may be a useful method to detect potential biomarkers in PC.

Tetraspanin CD82 drives acute myeloid leukemia chemoresistance by modulating protein kinase C alpha and β1 integrin activation

A principal challenge in treating acute myeloid leukemia (AML) is chemotherapy refractory disease. As such, there remains a critical need to identify key regulators of chemotherapy resistance in AML. In this study, we demonstrate that the membrane scaffold, CD82, contributes to the chemoresistant phenotype of AML. Using an RNA-seq approach, we identified the increased expression of the tetraspanin family member, CD82, in response to the chemotherapeutic, daunorubicin. Analysis of the TARGET and BEAT AML databases identifies a correlation between CD82 expression and overall survival of AML patients. Moreover, using a combination of cell lines and patient samples, we find that CD82 overexpression results in significantly reduced cell death in response to chemotherapy. Investigation of the mechanism by which CD82 promotes AML survival in response to chemotherapy identified a crucial role for enhanced protein kinase c alpha (PKCα) signaling and downstream activation of the β1 integrin. In addition, analysis of β1 integrin clustering by super-resolution imaging demonstrates that CD82 expression promotes the formation of dense β1 integrin membrane clusters. Lastly, evaluation of survival signaling following daunorubicin treatment identified robust activation of p38 mitogen-activated protein kinase (MAPK) downstream of PKCα and β1 integrin signaling when CD82 is overexpressed. Together, these data propose a mechanism where CD82 promotes chemoresistance by increasing PKCα activation and downstream activation/clustering of β1 integrin, leading to AML cell survival via activation of p38 MAPK. These observations suggest that the CD82-PKCα signaling axis may be a potential therapeutic target for attenuating chemoresistance signaling in AML.

Melanoblast transcriptome analysis reveals pathways promoting melanoma metastasis

Cutaneous malignant melanoma is an aggressive cancer of melanocytes with a strong propensity to metastasize. We posit that melanoma cells acquire metastatic capability by adopting an embryonic-like phenotype, and that a lineage approach would uncover metastatic melanoma biology. Using a genetically engineered mouse model to generate a rich melanoblast transcriptome dataset, we identify melanoblast-specific genes whose expression contribute to metastatic competence and derive a 43-gene signature that predicts patient survival. We identify a melanoblast gene, KDELR3, whose loss impairs experimental metastasis. In contrast, KDELR1 deficiency enhances metastasis, providing the first example of different disease etiologies within the KDELR-family of retrograde transporters. We show that KDELR3 regulates the metastasis suppressor, KAI1, and report an interaction with the E3 ubiquitin-protein ligase gp78, a regulator of KAI1 degradation. Our work demonstrates that the melanoblast transcriptome can be mined to uncover targetable pathways for melanoma therapy.

Evaluation of the correlation of vasculogenic mimicry, Notch4, DLL4, and KAI1/CD82 in the prediction of metastasis and prognosis in non-small cell lung cancer

Vasculogenic mimicry (VM) is a new blood supply style in tumors and has long been treated as a useful factor in malignant tumor metastasis and prognosis. Notch4 (a marker of Notch signaling pathway receptors), DLL4 (a marker of Notch signaling pathway ligands) and KAI1/CD82 (a suppressor gene of tumor metastasis) are all effective predictive factors for tumor metastasis. In this study, we analyzed correlations among VM, Notch4, DLL4, and KAI1/CD82 in non-small cell lung cancer (NSCLC), and their respective associations with patients' clinicopathological parameters and survival rate in NSCLC.Positive rates of VM, Notch4, DLL4, and KAI1/CD82 in 189 whole NSCLC specimens were detected by histochemical and immunohistochemical staining. Moreover, patients' clinicopathological information was also collected.Positive rates of VM, Notch4, and DLL4 were significantly higher, and levels of KAI1/CD82 were significantly lower in NSCLC than in normal lung tissues. Positive rates of VM, Notch4, and DLL4 were positively associated with tumor size, lymph node metastasis (LNM), distant metastasis (DM) and tumor-node-metastasis (TNM) stage, and inversely with patients, overall survival (OS) time and positive rate of DLL4 were positively associated with tumor grade. Levels of KAI1/CD82 were negatively associated with tumor size, LNM, DM, and TNM stage. The KAI1/CD82+ subgroup had significantly longer OS time than did the KAI1/CD82- subgroup. In multivariate analysis, high VM, Notch4, DLL4 levels, tumor size, LNM, DM, TNM stage, and low KAI1/CD82 levels were potential to be independent prognostic factors for overall survival time (OST) in NSCLC patients.VM and the expression of Notch4, DLL4, and KAI1/CD82 represent promising markers for tumor metastasis and prognosis, and maybe potential therapeutic targets for NSCLC.

Differential expression of tetraspanin superfamily members in dendritic cell subsets

Dendritic cells (DCs), which are essential for initiating immune responses, are comprised of different subsets. Tetraspanins organize dendritic cell membranes by facilitating protein-protein interactions within the so called tetraspanin web. In this study we analyzed expression of the complete tetraspanin superfamily in primary murine (CD4+, CD8+, pDC) and human DC subsets (CD1c+, CD141+, pDC) at the transcriptome and proteome level. Different RNA and protein expression profiles for the tetraspanin genes across human and murine DC subsets were identified. Although RNA expression levels of CD37 and CD82 were not significantly different between human DC subsets, CD9 RNA was highly expressed in pDCs, while CD9 protein expression was lower. This indicates that relative RNA and protein expression levels are not always in agreement. Both murine CD8α+ DCs and its regarded human counterpart, CD141+ DCs, displayed relatively high protein levels of CD81. CD53 protein was highly expressed on human pDCs in contrast to the relatively low protein expression of most other tetraspanins. This study demonstrates that tetraspanins are differentially expressed by human and murine DC subsets which provides a valuable resource that will aid the understanding of tetraspanin function in DC biology.

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.

Lichen Secondary Metabolite, Physciosporin, Inhibits Lung Cancer Cell Motility

Lichens produce various unique chemicals that can be used for pharmaceutical purposes. To screen for novel lichen secondary metabolites showing inhibitory activity against lung cancer cell motility, we tested acetone extracts of 13 lichen samples collected in Chile. Physciosporin, isolated from Pseudocyphellaria coriacea (Hook f. & Taylor) D.J. Galloway & P. James, was identified as an effective compound and showed significant inhibitory activity in migration and invasion assays against human lung cancer cells. Physciosporin treatment reduced both protein and mRNA levels of N-cadherin with concomitant decreases in the levels of epithelial-mesenchymal transition markers such as snail and twist. Physciosporin also suppressed KITENIN (KAI1 C-terminal interacting tetraspanin)-mediated AP-1 activity in both the absence and presence of epidermal growth factor stimulation. Quantitative real-time PCR analysis showed that the expression of the metastasis suppressor gene, KAI1, was increased while that of the metastasis enhancer gene, KITENIN, was dramatically decreased by physciosporin. Particularly, the activity of 3’-untranslated region of KITENIN was decreased by physciosporin. Moreover, Cdc42 and Rac1 activities were decreased by physciosporin. These results demonstrated that the lichen secondary metabolite, physciosporin, inhibits lung cancer cell motility through novel mechanisms of action.

Loss of tumor suppressors KAI1 and p27 identifies a unique subgroup of primary melanoma patients with poor prognosis

Primary melanoma, a highly aggressive malignancy, exhibits heterogeneity in biologic behaviors, clinical characteristics, metastasis potential and mortality. The present study sought to identify the molecular signatures that define a subgroup of primary melanomas with high risks of metastasis and mortality. First, we identified the markers that best differentiated metastatic melanomas from primary melanomas by examining the expression of seven previously reported biomarkers (BRAF, Dicer, Fbw7, KAI1, MMP2, p27 and Tip60) in a training cohort consisting of 145 primary melanomas and 105 metastatic melanomas. KAI1 and p27, both tumor suppressors, emerged as best candidates. Loss of both tumor suppressors occurred in the majority (74.29%) of metastatic melanomas. Further, a subset (metastatic like, or "ML", 33.10%) of primary melanomas also lost these two tumor suppressors. Kaplan-Meier analysis indicated that ML subgroup of primary melanoma patients had much worse 5 year survival compared with other primary melanoma patients (P = 0.002). The result was confirmed in an independent validation cohort with 92 primary melanomas (P = 0.030) and in the combined cohort with 237 melanoma patients (P = 3.00E-4). Additionally, compared to KAI1 and p27 as an individual prognostic marker, the combined signature is more closely associated with melanoma patient survival (P = 0.025, 0.264 and 0.009, respectively). In conclusion, loss of both KAI1 and p27 defines a subgroup of primary melanoma patients with poor prognosis. This molecular signature may help in metastatic melanoma diagnosis and may provide information useful in identifying high-risk primary melanoma patients for more intensive clinical surveillance in the future.

A Novel Function of CD82/KAI1 in Sialyl Lewis Antigen-Mediated Adhesion of Cancer Cells: Evidence for an Anti-Metastasis Effect by Down-Regulation of Sialyl Lewis Antigens

We have recently elucidated a novel function for CD82 in E-cadherin-mediated homocellular adhesion; due to this function, it can inhibit cancer cell dissociation from the primary cancer nest and limit metastasis. However, the effect of CD82 on selectin ligand-mediated heterocellular adhesion has not yet been elucidated. In this study, we focused on the effects of the metastasis suppressor CD82/KAI1 on heterocellular adhesion of cancer cells to the endothelium of blood vessels in order to further elucidate the function of tetraspanins. The over-expression of CD82 in cancer cells led to the inhibition of experimentally induced lung metastases in mice and significantly inhibited the adhesion of these cells to human umbilical vein epithelial cells (HUVECs) in vitro. Pre-treatment of the cells with function-perturbing antibodies against sLe^a/x significantly inhibited the adhesion of CD82-negative cells to HUVECs. In addition, cells over-expressing CD82 exhibited reduced expression of sLe^a/x compared to CD82-negative wild-type cells. Significant down-regulation of ST3 β-galactoside α-2, 3-sialyltransferase 4 (ST3GAL4) was detected by cDNA microarray, real-time PCR, and western blotting analyses. Knockdown of ST3GAL4 on CD82-negative wild-type cells inhibited expression of sLe^x and reduced cell adhesion to HUVECs. We concluded that CD82 decreases sLe^a/x expression via the down-regulation of ST3GAL4 expression and thereby reduces the adhesion of cancer cells to blood vessels, which results in inhibition of metastasis.

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.

Overexpression of MTA1 and loss of KAI-1 and KiSS-1 expressions are associated with invasion, metastasis, and poor-prognosis of gallbladder adenocarcinoma

AIMS AND BACKGROUND

Over 90% of patients with gallbladder cancer have invasion and/or metastasis when they are diagnosed at the clinic. Such patients usually have an extremely poor prognosis. The molecular mechanism responsible for the high prevalence of invasion and metastasis remains unknown.

METHODS

We investigated the expression of two metastasis-suppression genes--KAI-1 and KiSS-1--and a metastasis-associated gene--MTA1--in 108 adenocarcinomas, 15 gallbladder polyps, 35 chronic cholecystitis tissues, and 46 peritumoral tissues using in situ hybridization or immunohistochemistry.

RESULTS

We demonstrated that positive MTA1 expression was significantly higher whereas positive expressions of KAI-1 and KiSS-1 genes were significantly lower in gallbladder adenocarcinoma than in peritumoral tissues, polyps, and chronic cholecystitis. Positive MTA1 expression was significantly lower, but positive KAI-1 and KiSS-1 expressions were significantly higher in cases with well-differentiated adenocarcinoma, smaller tumor mass, no metastasis of lymph node, and no invasion of regional tissues than in cases having poorly differentiated adenocarcinoma, larger tumor mass, metastasis and invasion. Univariate Kaplan-Meier analysis showed that increased expression of MTA1 and lowered expression of KAI-1 and KiSS-1 were significantly associated with decreased overall survival. Cox regression analysis showed that tumor mass, lymph node metastasis, invasion, and MTA1 expression levels negatively correlated with survival.

CONCLUSIONS

Our study suggested that KAI-1, KiSS-1, and MTA1 might be important biological markers involved in the carcinogenesis, metastasis, and invasion of gallbladder adenocarcinoma, but MTA1 is an independent factor of prognosis.

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.

KAI1/CD82 and cyclin D1 as biomarkers of invasion, metastasis and prognosis of laryngeal squamous cell carcinoma

OBJECTIVE

This study aimed to investigate the expressions and significance of KAI1/CD82 and cyclin D1 in laryngeal squamous cell carcinoma (LSCC).

METHODS

Real-time quantitative PCR (Q-PCR) and Western blot assay were employed to detect the expressions of KAI1/CD82 and cyclin D1 in the laryngeal tissues of 86 LSCC patients, 32 patients with laryngeal polyp and 38 patients with laryngeal leukoplakia, and the influence of both proteins on the clinicopathological features and survival of LSCC patients.

RESULTS

The changes in mRNA and protein expressions of KAI1/CD82 and cyclin D1 were consistent in three groups, and the expressions of KAI1/CD82 and cyclin D1 were significantly different among three groups (P<0.01 or <0.05). The KAI1/CD82 expression in patients with TNM stage III-IV LSCC, poorly differentiated LSCC, clinical stage III-IV LSCC or lymph node metastasis was markedly lower than that in those with TNM stage I-II LSCC, well differentiated LSCC, clinical stage I-II LSCC or no lymph node metastasis (P<0.01 or <0.05). However, there was no marked difference in KAI1/CD82 expression between males and females and among patients in different age groups (P>0.05). In LSCC patients positive for KAI1/CD82 protein expression, the median survival time was 76 months, which was significantly longer than that in LSCC patients negative for KAI1/CD82 protein expression (48 months; X(2)=16.293, P=0.000). The Cyclin D1 expression in patients with TNM stage III-IV LSCC, poorly differentiated LSCC, or clinical stage III-IV LSCC was dramatically higher than that in patients with TNM stage I-II LSCC, well differentiated LSCC, or clinical stage I-II LSCC (P<0.01 or <0.05). However, no marked difference was noted in cyclin D1 expression between males and females, among patients in different age groups and between patients with and without lymph node metastasis (P>0.05). In LSCC patients positive for cyclin D1 protein expression, the median survival time was 40 months, which was markedly shorter than that in LSCC patients negative for cyclin D1 protein expression (X(2)=9.517, P=0.02). In LSCC patients, there was a negative correlation between KAI1/CD82 expression and cyclin D1 expression (X(2)=7.86, P<0.01).

CONCLUSION

KAI1/CD82 affects cell cycle. Both KAI1/CD82 and cyclin D1 are involved in the occurrence and development of LSCC, and may provide clinical information for evaluation of invasiveness, metastasis and prognosis of LSCC. Thus, KAI1/CD82 and cyclin D1 may serve as markers for determination of invasiveness, metastasis and prognosis of LSCC.

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.

CsA improves the trophoblasts invasiveness through strengthening the cross-talk of trophoblasts and decidual stromal cells mediated by CXCL12 and CD82 in early pregnancy

Our previous work has demonstrated that cyclosporin A (CsA) up-regulates but CD82 down-regulates the invasiveness of human trophoblasts. In the present study, we further investigated whether CsA can modulate the trophoblasts invasion through regulating the expression of CD82 in decidual stromal cells (DSCs). A co-culture model was established to investigate the effect of CsA on trophoblasts invasiveness. In-cell Western was performed to evaluate the expression of CD82, p53, β-catenin and the phosphorylation level of NF-κB p50 in DSCs. The secretion of CXCL12 of trophoblasts and DSCs was determined by enzyme-linked immunosorbent assay (ELISA). We found that CsA could not directly change the expression of CD82 in DSCs, but the CsA-treated trophoblasts significantly enhanced CD82 expression, NF-κB p50 phosphorylation and p53 expression, and decreased β-catenin expression in DSCs, and these effects could be abolished by anti-CXCL12 or CXCR4 neutralizing antibody. In addition, the invasiveness of trophoblast cells was markedly decreased after blocking CXCR4 of trophoblasts. Interestingly, when DSCs were pretreated with anti-CXCR4 neutralizing antibody, the invasiveness of trophoblast cells was enhanced in the coculture unit, and blocking CXCR4 on DSCs could reverse the decrease of trophoblasts invasiveness induced by CD82. Moreover, CsA further amplified these effects mediated by CXCL12 and CD82. Our results suggest that CsA not only promotes the trophoblasts invasiveness through stimulating the secretion of CXCL12, but also limits the invasiveness of trophoblasts by indirectly up-regulating the expression CD82. Therefore, CsA may contribute to the appropriate invasiveness of trophoblasts via strengthening the crosstalk between trophoblasts and DSCs.

Tetraspanins regulate the protrusive activities of cell membrane

Tetraspanins have gained increased attention due to their functional versatility. But the universal cellular mechanism that governs such versatility remains unknown. Herein we present the evidence that tetraspanins CD81 and CD82 regulate the formation and/or development of cell membrane protrusions. We analyzed the ultrastructure of the cells in which a tetraspanin is either overexpressed or ablated using transmission electron microscopy. The numbers of microvilli on the cell surface were counted, and the radii of microvillar tips and the lengths of microvilli were measured. We found that tetraspanin CD81 promotes the microvillus formation and/or extension while tetraspanin CD82 inhibits these events. In addition, CD81 enhances the outward bending of the plasma membrane while CD82 inhibits it. We also found that CD81 and CD82 proteins are localized at microvilli using immunofluorescence. CD82 regulates microvillus morphogenesis likely by altering the plasma membrane curvature and/or the cortical actin cytoskeletal organization. We predict that membrane protrusions embody a common morphological phenotype and cellular mechanism for, at least some if not all, tetraspanins. The differential effects of tetraspanins on microvilli likely lead to the functional diversification of tetraspanins and appear to correlate with their functional propensity.

CD82 gene suppression in endometrial stromal cells leads to increase of the cell invasiveness in the endometriotic milieu

Tetraspanin CD82 is a wide-spectrum tumor metastasis suppressor that inhibits motility and invasiveness of cancer cells. Endometriosis is a benign gynecological disorder, but appears malignant behaviors including invasion, ectopic implantation and recurrence. This study is to elucidate the role of CD82 expression regulation in the pathogenesis of endometriosis. The short interfering RNA silence was established to analyze the roles of CD82, chemokine CCL2, and its receptor CCR2 in the invasiveness of endometrial stromal cells (ESCs). We have found that the mRNA and protein levels of CD82 in the primary normal ESCs from endometrium without endometriosis are significantly higher than that of the primary ESCs from eutopic endometrium and ectopic tissue. CD82 inhibits the invasiveness of ESCs by downregulating CCL2 secretion and CCR2 expression via mitogen-activated protein kinase (MAPK) and integrinβ1 signal pathway, and in turn upregulating the expression of TIMP1 and TIMP2 in an autocrine manner. The combination of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) with 17β-estradiol can promote the invasion of ESCs via suppressing CD82 expression and stimulating CCL2 secretion and CCR2 expression, and the enhanced interaction of CCL2-CCR2 recruits more macrophages into the ectopic milieu in a paracrine manner, which further downregulates CD82 expression in the ectopic ESCs. Our study has demonstrated for the first time that the abnormal lower CD82 expression in ESCs induced by TCDD and estrogen may be an important molecular basis of endometriosis pathogenesis through enhancing the CCL2 secretion and CCR2 expression and the invasion of ESCs via MAPK and integrinβ1 signal pathway.

KAI1 gene is engaged in NDRG1 gene-mediated metastasis suppression through the ATF3-NFkappaB complex in human prostate cancer

NDRG1 and KAI1 belong to metastasis suppressor genes, which impede the dissemination of tumor cells from primary tumors to distant organs. Previously, we identified the metastasis promoting transcription factor, ATF3, as a downstream target of NDRG1. Further analysis revealed that the KAI1 promoter contained a consensus binding motif of ATF3, suggesting a possibility that NDRG1 suppresses metastasis through inhibition of ATF3 expression followed by activation of the KAI1 gene. In this report, we found that ectopic expression of NDRG1 was able to augment endogenous KAI1 gene expression in prostate cancer cell lines, whereas silencing NDRG1 was accompanied with significant decrease in KAI1 expression in vitro and in vivo. In addition, our results of ChIP analysis indicate that ATF3 indeed bound to the promoter of the KAI1 gene. Importantly, our promoter-based analysis revealed that ATF3 modulated KAI1 transcription through cooperation with other endogenous transcription factor as co-activator (ATF3-JunB) or co-repressor (ATF3-NFκB). Moreover, loss of KAI1 expression significantly abrogated NDRG1-mediated metastatic suppression in vitro as well as in a spontaneous metastasis animal model, indicating that KA11 is a functional downstream target of the NDRG1 pathway. Our result of immunohistochemical analysis showed that loss of NDRG1 and KAI1 occurs in parallel as prostate cancer progresses. We also found that a combined expression status of these two genes serves as a strong independent prognostic marker to predict metastasis-free survival of prostate cancer patients. Taken together, our result revealed a novel regulatory network of two metastasis suppressor genes, NDRG1 and KAI1, which together concerted metastasis-suppressive activities through an intrinsic transcriptional cascade.

Lack of germ line changes in KISS1 and KAI1 genes in sporadic head and neck cancer patients of Pakistani origin

BACKGROUND

Head and neck cancer is included among the top five most commonly prevailing cancers worldwide. Abnormalities of either genetic or epigenetic factors are found responsible for the development and progression of head and neck cancer. Metastasis is the leading cause of death in patients with head and neck cancer. Down regulation of metastasis suppressor genes (MSGs) expression have been frequently observed in advanced tumours.

METHODOLOGY

The present study was designed to screen two of the most frequently down-regulated MSGs (KISS1 and KAI1) for mutations in 120 diagnosed head and neck cancer affected Pakistani patients. The questionnaire was filled for basic information about age, gender, smoking habits and area of cancer affected and other relevant details. Primers for both genes were designed using "Primer 3" software in such a way that both intron exon boundaries were included in this region. DNA isolation and estimation was done by using organic method and agarose gel electrophoresis. Single Strand conformational polymorphism technique was used after amplification of the respective genes. Mobility patterns were analyzed using BioDoc Analyzer.

RESULTS

Data of patients were analyzed on the basis of age, sex and type of cancer as variables. The mean age of patients and controls was 44 years. There were 53% females and 47% males in this group of study, 63% nonsmokers and 37% smokers and larynx cancer was found to be most frequent type of cancer with a percentage of 64. Lack of germ line mutation was observed in the entire coding region in both coding regions as well as splice sites of the respective genes.

CONCLUSION

Germ line mutations in KISS1 and KAI1 are thus considered to be a less frequent event in head and neck cancer patients. However, two polymorphisms in intronic region of exon 3 and exon 9 of KAI1 gene were observed in 1% of patients. In non coding region downstream of exon 3 (KAI1), there was a C 29166 T substitution and in intronic region upstream exon 9 of KAI1 gene, a C 52840 A substitution was observed. Both patients were females with ages 47 and 50 years respectively. A detailed analysis of regulatory mechanism is required to explore the genetic basis of down regulation of these MSGs for a better understanding of head and neck cancer progression.

Expressional alterations and transcript isoforms of metastasis suppressor genes (KAI1 and KiSS1) in breast cancer patients

BACKGROUND

Metastasis suppressor genes are involved in the inhibition of a cancer cell's ability to metastasize. Down expression of such genes may contribute to pathogenesis of breast cancer. The aim of current study was firstly to evaluate expression of two examples, KAI1 and KISS1, and then to determine relationships with stages of breast cancer in a Pakistani population.

METHODOLOGY

Fresh biopsy tissues were collected from different hospitals and oncology research institutes. The semi quantitative reverse transcriptase polymerase chain reaction was used to investigate KAI1 and KISS1 expression in 25 breast tumor tissues and 25 normal tissues. Statistical analysis was performed to explore its association with breast cancer risk.

RESULTS

The present study revealed that KAI1 and KISS1 mRNA expression was markedly reduced in tissues of breast cancer compared to adjacent normal tissue. In present study a splice variant of KAI1 during a screen for its expression analysis was also observed. This splice variant has not been reported previously.

CONCLUSIONS

Metastasis suppressor genes demonstrate reduced expression in breast cancers in Pakistan.

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.

Effect of expressional alteration of KAI1 on breast cancer cell growth, adhesion, migration and invasion

KAI1, also known as CD82, is a candidate metastasis suppressor gene and has been indicated in the disease progression of certain solid tumours, including those of breast cancer. The present study aimed to investigate the importance of KAI1 as a potential metastasis suppressor in breast cancer cells. MDA-MB-231 and MCF-7 sublines with different patterns of KAI1 expression were created by way of anti-KAI1 transgene or transfection of KAI1 expression construct. Cell adhesion was markedly increased in cancer cells showing increased expression of KAI1 (MCF-7(KAI1EXP), p=0.021 vs. control cells), while it was significantly reduced in the KAI1 knockout subline, MDA-MB-231(KAI1KO) (p=0.002 and 0.0004, respectively). Significant increase of cell migration of MCF-7(KAI1EXP) cells (p=0.024 vs. control) and restricted motility of MDA-MB-231(KAI1KO) cells (p=0.003) were observed. Furthermore, MCF-7(KAI1EXP) cells also showed reduced cell invasion (p=0.022), while MDA-MB-231(KAI1KO) cell line showed a significant increase in invasion (p=0.0063 and p=0.007, respectively). KAI1 did not affect cell growth. It is concluded therefore that KAI1 plays an important role in cell adhesion, invasion and migration of breast cancer cells, in vitro, and is a potential metastasis suppressor gene in breast cancer.

Learning therapeutic lessons from metastasis suppressor proteins

Metastasis suppressor proteins regulate multiple steps in the metastatic cascade, including cancer cell invasion, survival in the vascular and lymphatic circulation, and colonization of distant organ sites. Understanding the biology of metastasis suppressors provides valuable mechanistic insights that may translate to therapeutic opportunities. Several reports have explored novel strategies for restoring metastasis suppressor function, including gene transfer, induction of previously suppressed gene expression and exogenous administration of gene product. Pathways activated downstream of metastasis suppressor loss can also be targeted. Although none of these strategies are yet in routine clinical use, several are being tested preclinically and in clinical trials.

Transcriptional and translational modulation of KAI1 expression in ductal carcinoma of the breast and the prognostic significance

KAI1, also known as CD82, has been shown to have a potential impact on the invasiveness of cancer cells. In the present study, expression pattern of KAI1, both at transcription and translation levels and the potential clinical value of the expression were explored in a cohort of normal and ductal mammary cancer tissues (n=71). A marked reduction of KAI1 transcript was observed in invasive ductal breast tumours as compared to normal tissues. Expression of KAI1 protein was higher in normal tissues as compared to tumour samples. Though no significant difference of KAI1 expression between different grades of tumour was observed (p=0.064), significant correlation of TNM staging with KAI1 expression has been observed in invasive ductal breast cancer patients (p=0.045). Additionally, it was also observed that patients showing higher expression of KAI1 had a longer 10-year survival rate as compared to a low level or completely negative expression KAI1 (p=0.0136). KAI1 inverse correlation with tumour progression may be used as a strong prognostic marker.

Decreased expression of KAI1/CD82 metastasis suppressor gene is associated with loss of heterozygosity in melanoma cell lines

KAI1/CD82, a metastasis suppressor gene of prostate cancer, is located on the human chromosome 11p11.2. Down-regulation of KAI1/CD82 during tumor progression and metastasis has been reported in several cancers, but the mechanism of this down-regulation remains unknown. The relationship between down-regulation of KAI1/CD82 mRNA expression and KAI1/CD82 gene alterations in human melanoma cell lines were investigated. The promoter methylation status was examined after a 331-bp GC-rich fragment of the promoter region was amplified in G361, SK-MEL-24 and SK-MEL-28 cell lines treated with bisulfite. In order to detect methylated CpGs in all three cell lines, 331-bp fragments were sequenced. To examine the restoration of KAI1/CD82 mRNA and protein expression, the cells were exposed to methylase inhibitor, 5-aza-2'-deoxycytidine (5-AzaC). Bisulfite-sequencing data showed no methylation in G361 and SK-MEL-24 cells, and slight methylation in SK-MEL-28 cells at CpG sites 23-26 in the promoter. Real-time PCR and flow cytometry analysis showed that 5-AzaC-treated cells restored KAI1/CD82 mRNA and protein expression in SK-MEL-24 and SK-MEL-28 cells, compared to the controls. The restoration of KAI1/CD82 mRNA and protein expression detected no significant difference between SK-MEL-24 and SK-MEL-28 cells. This means that 5-AzaC did not affect the methylated cells only. Loss of heterozygosity (LOH) at polymorphic microsatellite loci on the human chromosome 11 in the human melanoma cells was also examined. Microsatellite analysis showed LOH at D11S1344 in SK-MEL-24 and SK-MEL-28 cells, and G361 showed allelic imbalance. In conclusion, this study suggests that down-regulation of KAI1/CD82 mRNA expression in human melanoma cell lines is related to LOH or allelic imbalance, but not to methylation of the KAI1/CD82 gene region.

[Role of KAI1 gene expression and loss of heterozygosity of KAI1 in metastatic potential and prognosis of pancreatic cancer]

OBJECTIVE

To investigate the role of KAI1 gene expression and loss of heterozygosity (LOH) of KAI1 in metastatic potential and prognosis of pancreatic cancer.

METHODS

The expression of KAI1 gene was studied by immunohistochemistry for CD82 on paraffin-embedded tumor tissues. The LOH of KAI1 gene was detected by microdissection, polymerase chain reaction (PCR) and denaturing high performance liquid chromatography (DHPLC).

RESULTS

The positivity rate of CD82 in primary pancreatic cancer was 76% (47/62). CD82 expression was significantly higher (P < 0.01) in earlier tumor stages (I and II), as compared to the advanced tumor stages ( III and IV) in which nodal or distant metastases were present. The expression rate of CD82 in patients who survived for more than one year was higher than that in patients who survived for less than one year (P < 0.05). The percentage of LOH at D11S1344 and D11S1326 loci was 17%.

CONCLUSIONS

The abnormal expression of CD82 which participates in malignant progression of pancreatic cancer is probably associated with LOH of KAI1 gene. Detection of CD82 expression and LOH of KAI1 gene may carry potential clinical significance in evaluating the metastatic potential and prognosis of pancreatic cancer.

[Effect of metastasis suppressor gene KAI1 on the proliferation and invasive ability of cervical carcinoma cells]

OBJECTIVE

To explore the effect of metastasis suppressor gene KAI1 on the proliferation and invasive ability of cervical cancer cell line CaSki.

METHODS

pCMV-KAI1 cDNA plasmid was transferred into cervical carcinoma cell line CaSki by liposome, which had low level of endogenous KAI1 expression. The expressions of KAI1 protein and mRNA were determined by immunohistochemistry and real-time fluorescence quantitative PCR (RT-PCR), the proliferation of KAI1-transfected CaSki cells was investigated by MTT assay and the invasive ability of these cells was evaluated by in vitro invasion assays.

RESULTS

After the transfection of pCMV-KAI1 cDNA, the level of KAI1 mRNA and protein expression in CaSki cell were increased (P < 0.05), while the cell proliferation was suppresssed, and the migrative ability of passing through the membrane filte also decreased evidently (P < 0.05).

CONCLUSION

The KAI1 metastasis suppressor gene suppressed the ability of proliferation and invasion of cervical cancer cell CaSki in vitro.

An alternatively spliced KAI1 mRNA is expressed at low levels in human bladder cancers and bladder cancer cell lines and is not associated with invasive behaviour

Levels of the KAI1 metastasis suppressor are reduced in advanced stages of many human cancers, leading to the loss of KAI1 function. A recent study has suggested that the loss of KAI1 function may also occur via alternative splicing of KAI1 mRNA which deletes an exon encoding a critical 28 amino acids from the protein. Using PCR, 20 bladder tumours at differing stage and grade, a non-tumourigenic urothelial cell line (SV-HUC-1) and 17 bladder cancer cell lines were examined for expression of this alternatively spliced (AS) KAI1 mRNA. Full-length KAI1 mRNA was present in all tumour samples and low levels of AS KAI1 mRNA in 15/20 samples. There was no association between the presence or absence of AS mRNA and clinicopathological characteristics of these tumours. Low levels of AS KAI1 mRNA were present in SV-HUC-1 and 14/17 bladder cancer cell lines. There was no association between the presence or absence of AS KAI1 mRNA and tumourigenicity, or in vivo invasive abilities of these cell lines. In all cell lines expressing AS KAI1 mRNA, levels were 3- to 5-fold lower than levels of wild-type mRNA, irrespective of wild-type mRNA levels. Low levels of an alternatively spliced form of KAI1 mRNA are present in most bladder cancer tumours and tumour cell lines, but are not associated with invasive behaviour.

Regulation of c-Met signaling by the tetraspanin KAI-1/CD82 affects cancer cell migration

It has been proposed that the metastasis suppressor CD82/KAI-1, which is a member of the tetraspanin superfamily, regulates biological activity by associating with cell surface receptors or proteins. We show a novel association between CD82 and the hepatocyte growth factor (HGF) receptor c-Met. Although ectopic expression of CD82 in nonsmall cell lung carcinoma cells did not affect the tyrosine phosphorylation of c-Met, these cells showed significant suppression of HGF-induced lamellipodial protrusion and cell migration. CD82 selectively attenuated c-Met signaling via the Ras-Cdc42/Rac and the phosphatidylinositol 3-kinase/Cdc42/Rac pathways. In contrast, another c-Met signaling pathway that involves phosphatidylinositol 3-kinase/Akt and phosphatidylinositol 3-kinase/mitogen activated protein kinase was not affected by CD82. Signaling adapter proteins for c-Met, such as Grb2 and p85, exhibited reduced association with c-Met in cells that ectopically expressed CD82. These results indicate that the CD82-c-Met complex inhibits HGF-induced cancer cell migration by the inactivation of small GTP-binding proteins of the Rho family via c-Met adapter proteins.

[Inhibitory effect of KAI1 gene on breast cancer cell growth in vitro]

OBJECTIVE

To explore the inhibitory effect of KAI1 gene on breast cancer cell growth in vitro.

METHODS

Highly metastatic human breast cancer cell line MDA-MB-231 was transfected with pCMV-KAI1 or mock transfected plasmid pCMV with lipofectamine. Western blot was used to determine the expression of target protein of KAI1. The proliferative ability of cells was tested by MTT assay and colony-forming test. The cell cycle pattern was assayed by flow cytometry. The metastatic ability was investigated by cell adhesion and invasion assays.

RESULTS

A stable cell clone transfected with KAI1 gene was obtained and over-expression of KAI1 protein was observed. There was a significant decline in cell proliferative ability of pCMV-KAI1 transfected MDA-MB-231 cells in comparison with the mock-transfected ones and non-transfected ones, revealed by MTT assay and colony-forming test (P < 0.05). The ability of adherence and invasion of pCMV-KAI1 transfected cells was significantly reduced in comparison with the other two groups (P < 0.05). Also, flow cytometry analysis revealed that in KAI1 transfected cell group the number of cells in G0/G1 phase increased markedly from 36.78% +/- 0.61% to 64.00% +/- 7.56%, while the number of cells in G2/M phase decreased from 17.88% +/- 0.76% to 7.63% +/- 0.60%, comparing with the non-transfected ones.

CONCLUSION

KAI1 gene suppresses the invasive ability of human breast cancer cells in vitro and may inhibit the proliferative ability by changing the cell cycle pattern.

Genistein induces the metastasis suppressor kangai-1 which mediates its anti-invasive effects in TRAMP cancer cells

Previous studies demonstrated a direct correlation with loss of kangai-1 (KAI1), a metastasis suppressor, and poor prognosis in human prostate and other cancers. In this study, we have characterized the age-dependent downregulation of KAI1 in the TRAMP model which was reversed when mice were fed a genistein-enriched diet. We demonstrated here that doses of genistein (5 and 10 microM)--achievable by supplement intake--significantly induced the expression of KAI1, both at the mRNA and protein levels (up to 2.5-fold), and decreased the invasiveness of TRAMP-C2 cells >2.0-fold. We have pinpointed KAI1 as the invasion suppressor, since its knockdown by siRNA restored the invasive potential of genistein-treated TRAMP-C2 cells to control levels. This work provides the first evidence that genistein treatment may counteract KAI1 downregulation, which is observed in many cancer types and therefore, could be used in anti-metastatic therapies.

Reduced protein expression of metastasis-related genes (nm23, KISS1, KAI1 and p53) in lymph node and liver metastases of gastric cancer

PURPOSE

Metastasis remains an incurable common complication in patients with gastric cancer. A variety of theories have been proposed to explain the inefficiency of the metastatic process. To compare protein expression of metastasis-related genes (nm23, KISS1, KAI1 and p53) between primary tumours and metastatic tumours may be useful in illustrating these theories.

METHODS

Metastasis-related tissue microarrays (including normal tissues, primary tumours, nodal metastases and liver metastases) were constructed. The protein expression of nm23, KISS1, KAI1 and p53 in lymph node and liver metastases from advanced gastric cancer specimens was mainly examined by immunohistochemical staining in relation to primary tumours.

RESULTS

Immunohistochemical staining showed reduced protein expression of nm23, KISS1 and KAI1 in lymph node and liver metastases compared with primary tumours. Results for p53 were to the contrary.

CONCLUSIONS

Our investigations revealed a tendency of reduced protein expression of metastasis suppressor genes nm23, KISS1 and KAI1 in gastric cancer with the progress of metastasis. This means that the progression theory is an important determinant of metastatic efficiency.

Effect of KAI1/CD82 on the beta1 integrin maturation in highly migratory carcinoma cells

The KAI1/CD82 protein has been documented as the tumor metastasis suppressor in many types of human cancers. KAI1/CD82 regulates cell motility and invasiveness; however, the mechanism by which this occurs remains to be fully established. Several studies have shown that KAI1/CD82 modulates integrin-dependent signaling. It was suggested that KAI1/CD82 might function to attenuate the beta1 integrin function of inducing cellular migration. A wound-healing and modified Boyden chamber assays were performed to investigate the mechanism of the KAI1/CD82-mediated inhibition of cell migration. It was found that the migratory ability of H1299/CD82 was inhibited. The immunoblotting and biotinylation assays revealed that H1299/CD82 showed significantly decreased expression of the mature form of beta1, which was functional at the cell surface. It was confirmed that KAI1/CD82 regulates the maturation of the beta1 integrin using CD82-specific si-RNA. These results support a model in which KAI1/CD82 attenuates the maturation of the beta1 integrin precursor and thereby suppresses cell migration.

[In situ hybridization study on the expression of Kiss-1 and KAI-1 metastasis suppressor genes in gastric cancer]

OBJECTIVE

To investigate the mRNA levels of Kiss-1 and KAI-1 metastasis suppressor genes in gastric cancer, and to explore its clinical value.

METHODS

In situ hybridization was used on routinely paraffin-embedded sections of resected specimens of 49 cases with gastric cancer and 20 cases with pericancerous tissue.

RESULTS

The positive rates and the scores of Kiss-1 and KAI-1 mRNA in gastric cancer tissue were significantly lower than those in pericancerous tissue (P<0.01). The positive rates and scores in normal to mild-atypical hyperplasia cases were significantly higher than those in middle to severe-atypical hyperplasia of pericancerous tissue (P<0.05,P<0.01). The positive rates and scores of Kiss-1 and KAI-1 mRNA in patients with infiltrating depth T1~T2, without lymph node metastasis, with only first group of lymph node metastasis, and without distant organ metastasis were significantly higher than those in patients with infiltrating depth T3~T4, with lymph node metastasis, with second or third group of lymph node metastasis and with distant organ metastasis. A strong positive correlation was found between the expressive scores of Kiss-1 and KAI-1 mRNA in gastric cancer (r=0.53, P<0.01).

CONCLUSION

The expression of Kiss-1 and/or KAI-1 mRNA may be important biological markers of reflecting invasive and metastatic potential and prognosis in gastric cancer. The assays of Kiss-1 and/or KAI-1 mRNA expression level in benign lesions of stomach may have important clinical value for the protection and early-stage finding of gastric cancer.

[Effect of metastasis suppressor gene KAI1 on adhesion of hepatocellular carcinoma cell line MHCC97-H]

BACKGROUND & OBJECTIVE

Metastasis suppressor gene KAI1 can inhibit the metastasis potential of many malignant tumors. This study was to explore the effect of KAI1 gene on the adhesion of hepatocellular carcinoma cell line MHCC97-H with high metastatic potential, and to find the possible mechanism.

METHODS

The plasmid containing KAI1 gene was transfected into MHCC97-H cells. The growth status of the cells was observed. The changes of adhesion factors, soluble intercellular adhesive molecule-1 (sICAM-1) and E-cadherin, in the cells were detected by ELASA and Western blot. The character of cell adhesion was determined through plate colony formation test and cell adhesion test.

RESULTS

The morphology of MHCC97-H cells did not change markedly after transfection of KAI1 gene, but black granules in cytoplasm were increased. Four days after transfection, the expression of sICAM-1 and E-cadherin were decreased by 24.28% and 26.02%. The adhesion rate was decreased by 11.34% at 3 h after transfection, and by 24.00% at 4 h after transfection, but the cloning efficiency did not change much.

CONCLUSION

KAI1 gene could affect the growth pattern and proliferation of MHCC97-H cells, suppress sICAM-1 secretion and E-cadherin production, and inhibit adhesion of MHCC97-H cells.

Adenoviral transduction of MRP-1/CD9 and KAI1/CD82 inhibits lymph node metastasis in orthotopic lung cancer model

Conventional therapies still remain less effective for metastasis of lung cancer, thus leading to a poor prognosis for this disorder. Although the processes involved in metastasis have not yet been clearly elucidated, our previous studies have shown that higher expression levels of MRP-1/CD9 and KAI1/CD82 in cancer cells are significantly correlated with less metastatic potency. To determine whether the gene transfer of these tetraspanins into lung tumor cells may be a useful strategy to regulate metastasis, we adopted an orthotopic lung cancer model produced by the intrapulmonary implantation of Lewis lung carcinoma (LLC) cells and evaluated the metastatic growth in the mediastinal lymph nodes using two different methods of gene delivery as follows: (a) the implantation of LLC cells preinfected with adenovirus encoding either MRP-1/CD9 cDNA, KAI1/CD82 cDNA, or LacZ gene into the mouse lung and (b) the intratracheal administration of these adenoviruses into the mice orthotopically preimplanted with LLC cells. In both cases, we found that the delivery of either MRP-1/CD9 or KAI1/CD82 cDNA dramatically reduced the metastases to the mediastinal lymph nodes in comparison with those of LacZ gene delivery, without affecting the primary tumor growth at the implanted site. These results reemphasize the important role of MRP-1/CD9 and KAI1/CD82 in the suppression of the metastatic process and also show the feasibility of gene therapy when using these tetraspanins for lung cancer to prevent metastasis to the regional lymph nodes. This strategy may therefore be clinically applicable as a prophylactic treatment to suppress the occurrence of lymph node metastasis.

BCAR1 expression in prostate cancer: association with 16q23 LOH status, tumor progression and EGFR/KAI1 staining

BACKGROUND

The 16q23 locus has been recently suggested in both breast and prostate cancer to contain a gene involved in disease progression. The breast cancer antiestrogen resistance 1 (BCAR1) gene, located at 16q23, contributes to many cellular processes including migration and survival, and interacts in vitro with the growth factor receptor EGFR and the metastasis suppressor KAI1.

METHODS

BCAR1, EGFR, and KAI1 expression was studied by immunohistochemistry on a tissue microarray containing 100 localized prostate cancers (LPC), 15 hormone refractory prostate cancers (HRPC), and 15 lymph node metastasis (LNM). Forty eight of the LPC were also analyzed for 16q23 LOH status using microsatellite markers.

RESULTS

BCAR1 staining was present in 25% of LPC, associated with higher Gleason score, and in 60% and 80% of, respectively, LNM and HRPC. BCAR1 expression was inversely correlated with 16q23 LOH status (P < 0.001), and was associated with high EGFR staining (P < 0.02), and negative KAI1 expression (P < 0.01).

CONCLUSIONS

BCAR1 expression in LPC seems to be regulated at least in part by genetic events. The increased expression of BCAR1 with disease progression suggests a potential interest for both prognosis and treatment.

Expression of KAI1/CD82 and MRP-1/CD9 in transitional cell carcinoma of bladder

The expression of KAI1/CD82 and MRP-1/CD9 in transitional cell carcinoma of bladder (TCCB) and its clinical significance were investigated. Immunohistochemistry was used to detect KAI1/CD82 and MRP-1/CD9 protein expression in 52 TCCB specimens. Correlation between the expression of KAI1/CD82 and MRP-1/CD9 to clinicopathologic factors was statistically analyzed. The results showed that the positive rate of KAI1/CD82 and MRP-1/CD9 in TCCB was 50% and 61.5%, respectively. The MRP-1/CD9 and KAI1/CD82 expression was significantly associated with grade of TCCB (P<0.05), but no correlation was found between MRP-1/CD9 or KAI1/CD82 expression and clinical stage of TCCB (P>0.05). The expression level of MRP-1/CD9 and KAI1/CD82 in recurrent TCCB samples was lower than that in non-recurrent samples (P<0.05). Meanwhile, the correlation between the KAI1/CD82 expression and MRP-1/CD9 expression was statistically significant (r=0.316, P<0.05). It was concluded that KAI1/CD82 and MRP-1/CD9 expression may be important prognostic indicators and potentially useful for assessing the biological behavior of TCCB.

Analysis of vascular gene expression in arthritic synovium by laser-mediated microdissection

OBJECTIVE

In rheumatoid arthritis (RA), formation of new blood vessels is necessary to meet the nutritional and oxygen requirements of actively proliferating synovial tissue. The aim of this study was to analyze the specific synovial vascular expression profiles of several angiogenesis-related genes as well as CD82 in RA compared with osteoarthritis (OA), using laser-mediated microdissection (LMM).

METHODS

LMM and subsequent real-time polymerase chain reaction were used in combination with immunohistochemical analysis for area-specific analysis of messenger RNA (mRNA) and protein expression of vascular endothelial growth factor (VEGF), VEGF receptor 1 (VEGFR-1), VEGFR-2, hypoxia-inducible factor 1alpha (HIF-1alpha), HIF-2alpha, platelet-derived growth factor receptor alpha (PDGFRalpha), PDGFRbeta, inhibitor of DNA binding/differentiation 2 (Id2), and CD82 in RA and OA synovial microvasculature and synovial lining.

RESULTS

Expression of Id2 mRNA was significantly lower in RA synovial vessels compared with OA synovial vessels (P=0.0011), whereas expression of VEGFR-1 was significantly higher in RA (P=0.0433). No differences were observed for the other parameters. At the protein level, no statistically significant differences were observed for any parameter, although Id2 levels were 2.5-fold lower in RA (P=0.0952). However, the number of synovial blood vessels and the number of VEGFR-2-expressing blood vessels were significantly higher in RA compared with OA.

CONCLUSION

Our results underscore the importance of area-specific gene expression analysis in studying the pathogenesis of RA and support LMM as a robust tool for this purpose. Of note, our results indicate that previously described differences between RA and OA in the expression of angiogenic molecules are attributable to higher total numbers of synovial and vascular cells expressing these molecules in RA rather than higher expression levels in the individual cells.

The inner loop of tetraspanins CD82 and CD81 mediates interactions with human T cell lymphotrophic virus type 1 Gag protein

The tetraspanin superfamily proteins play important roles in organizing membrane protein complexes, modulating integrin function, and controlling T cell adhesion. Tetraspanins such as CD82 contain two extracellular loops with its N terminus, C terminus, and inner loop exposed to the cytoplasm. The matrix (MA) domain of human T cell lymphotrophic virus, type 1 (HTLV-1), Gag interacts with the cytoplasmic face of the plasma membrane and is concentrated at tetraspanin-enriched microdomains. To understand the basis of this association, we generated site-directed mutations in the various domains of CD82 and used coimmunoprecipitation and colocalization approaches to examine interactions with HTLV-1 MA. The large extracellular loop of CD82, which is important for interactions with integrins, was not required for the association with HTLV-1 MA. The cytoplasmic N terminus and C terminus of CD82 were also dispensable for CD82-MA interactions. In contrast, mutations of conserved amino acids in the inner loop of CD82 or of palmitoylated cysteines that flank the inner loop diminished CD82 association with MA. HTLV-1 MA also interacted with the inner loop of CD81. Thus, association of HTLV-1 Gag with tetraspanin-enriched microdomains is mediated by the inner loops of CD81 and CD82.

[Adenovirus-mediated overexpression of KAI1 suppresses sphingosine kinase activation and metastasis of pancreatic carcinoma cells]

OBJECTIVE

To investigate influence of KAI1 expression on the pancreatic carcinoma cell migration and its mechanisms.

METHODS

We construct an adenoviral vector carrying the full length cDNA of KAI1 (Ad-KAI1). The Ad-KAI1 virus was packed and amplified in 293 cells and was purified by Adeno-X Virus Purification Kit. The adenovirus-mediated KAI1 expression in human pancreatic carcinoma cell line (PANC I) was detected by flow cytometric analysis. Sphingosine kinase (SPK) activation was determined by [gamma-(32)P] incorporation. And cell migration was assayed by using transwell.

RESULTS

We constructed Ad-KAI1 vector successfully. The 86.3% of pancreatic cancer cells PANC I were identified and infected by Ad-KAI1 constructed by us. At same time, we found out higher concentration of SPK in the PANC I cancer cells without infection of Ad-KAI1 using RT-PCR. Overexpression of KAI1 significantly inhibited the activity of SPK and the migration ability of the PANC I cells, which was induced by activity of SPK.

CONCLUSIONS

Adenovirus-mediated overexpression of KAI1 suppresses sphingosine kinase activation and migration of pancreatic carcinoma cells. This research is helpful for elucidating the anti-metastasis mechanisms KAI1 in pancreatic carcinoma cells.

Roles of sumoylation of a reptin chromatin-remodelling complex in cancer metastasis

Defining the functional modules within transcriptional regulatory factors that govern switching between repression and activation events is a central issue in biology. Recently, we have reported the dynamic role of a beta-catenin-reptin chromatin remodelling complex in regulating a metastasis suppressor gene KAI1 (ref.1), which is capable of inhibiting the progression of tumour metastasis. Here, we identify signalling factors that confer repressive function on reptin and hence repress the expression of KAI1. Biochemical purification of a reptin-containing complex has revealed the presence of specific desumoylating enzymes that reverse the sumoylation of reptin that underlies its function as a repressor. Desumoylation of reptin alters the repressive function of reptin and its association with HDAC1. Furthermore, the sumoylation status of reptin modulates the invasive activity of cancer cells with metastatic potential. These data clearly define a functional model and provide a novel link for SUMO modification in cancer metastasis.

Characterization of an antibody that can detect the Kai1/CD82 murine metastasis suppressor

BACKGROUND

Kai1, also known as CD82, is a member of the tetraspanin family (TM4SF). The human homolog, KAI1, is an activation antigen of T-cells and is a metastasis suppressor for prostate and other cancers. Little is known about the mouse protein because of the lack of antibody reagents.

METHODS

Peptide immunized rabbits were used to generate polyclonal antibody to Kai1. The antibody was analyzed using immunoblotting, flow cytometry, and immunohistochemistry.

RESULTS

This antibody specifically recognizes murine Kai1 protein, crossreacts with rat Kai1 but not with human KAI1. The normal tissue distribution of this protein in mice is shown to be similar to that of the human homolog. Interestingly, mouse prostatic epithelium showed differential expression within the lobes.

CONCLUSION

This antibody, the first described that can specifically detect murine Kai1/CD82, should be very useful in addressing the mechanism of action of Kai1 in metastatic suppression.