Expression of a human cell adhesion molecule, MUC18, in prostate cancer cell lines and tissues

METCAM Is a Potential Biomarker for Predicting the Malignant Propensity of and as a Therapeutic Target for Prostate Cancer

Prostate cancer is the second leading cause of cancer-related death worldwide. This is because it is still unknown why indolent prostate cancer becomes an aggressive one, though many risk factors for this type of cancer have been suggested. Currently, many diagnostic markers have been suggested for predicting malignant prostatic carcinoma cancer; however, only a few, such as PSA (prostate-specific antigen), Prostate Health Index (PHI), and PCA3, have been approved by the FDA. However, each biomarker has its merits as well as shortcomings. The serum PSA test is incapable of differentiating prostate cancer from BPH and also has an about 25% false-positive prediction rate for the malignant status of cancer. The PHI test has the potential to replace the PSA test for the discrimination of BPH from prostate cancer and for the prediction of high-grade cancer avoiding unnecessary biopsies; however, the free form of PSA is unstable and expensive. PCA3 is not associated with locally advanced disease and is limited in terms of its prediction of aggressive cancer. Currently, several urine biomarkers have shown high potential in terms of being used to replace circulating biomarkers, which require a more invasive method of sample collection, such as via serum. Currently, the combined multiple tumor biomarkers may turn out to be a major trend in the diagnosis and assessment of the treatment effectiveness of prostate cancer. Thus, there is still a need to search for more novel biomarkers to develop a perfect cocktail, which consists of multiple biomarkers, in order to predict malignant prostate cancer and follow the efficacy of the treatment. We have discovered that METCAM, a cell adhesion molecule in the Ig-like superfamily, has great potential regarding its use as a biomarker for differentiating prostate cancer from BPH, predicting the malignant propensity of prostate cancer at the early premalignant stage, and differentiating indolent prostate cancers from aggressive cancers. Since METCAM has also been shown to be able to initiate the spread of prostate cancer cell lines to multiple organs, we suggest that it may be used as a therapeutic target for the clinical treatment of patients with malignant prostate cancer.

METCAM/MUC18 Plays a Tumor Suppressor Role in the Development of Nasopharyngeal Carcinoma Type I

From previous studies of negatively correlating the expression of human METCAM/MUC18 with the pathology of nasopharyngeal carcinoma (NPC), we have suggested that human METCAM/MUC18 (huMETCAM/MUC18) might play a tumor suppressor role in the development of nasopharyngeal carcinoma. To scrutinize this hypothesis, we investigated the effects of huMETCAM/MUC18′s over-expression on in vitro cellular behavior and on the in vivo tumorigenesis of one NPC cell line (NPC-TW01). HuMETCAM/MUC18 cDNA was first transfected into the NPC-TW01 cell line, which was established from NPC type I, and many G418-resistant clones were obtained. Then, two NPC-TW01 clones, which expressed high and medium levels of huMETCAM/MUC18, respectively, and one empty vector (control) clone were used to test the effects of huMETCAM/MUC18′s over-expression on in vitro behaviors and on in vivo tumorigenesis (via subcutaneous injection) in athymic nude mice (Balb/cAnN.Cg-Foxnl^nu/Cr1Nar1). The time course of tumor proliferation and the final tumor weights were determined. Tumor sections were used for the histology and immunohistochemistry (IHC) studies. Tumor lysates were used for determining the expression levels of huMETCAM/MUC18 and various downstream key effectors. HuMETCAM/MUC18′s over-expression reduced in vitro motility and invasiveness and altered growth behaviors in 3D basement membrane culture assays, and it decreased the in vivo tumorigenicity of the NPC-TW01 cells. The tumor cells from a high-expressing clone were clustered and confined in small areas, whereas those from a vector control clone were more spread out, suggesting that the tumor cells from the high-expressing clone appeared to stay dormant in micro-clusters. Expression levels of the proliferation index, an index of the metabolic switch to aerobic glycolysis, angiogenesis indexes, and survival pathway indexes were reduced, whereas the pro-apoptosis index increased in the corresponding tumors. The over-expression of huMETCAM/MUC18 in the NPC-TW01 cells decreased the epithelial-to-mesenchymal transition and the in vitro and in vitro tumorigenesis, suggesting that it plays a tumor suppressor role in the development of type I NPC, perhaps by increasing apoptosis and decreasing angiogenesis, proliferation, and the metabolic switch to aerobic glycolysis.

Validating METCAM/MUC18 as a Novel Biomarker to Predict the Malignant Potential of Prostate Cancer at an Early Stage by Using a Modified Gold Nanoparticles-Based Lateral Flow Immunoassay

(1) Background: To further validate METCAM/MUC18 as a diagnostic biomarker for prostate cancer, a modified Lateral Flow Immune Assay (LFIA) with increased sensitivity and specificity was designed by taking advantage of the extremely high affinity between biotin and streptavidin and used. (2) Methods: The combination of a commercial biotinylated rabbit antibody (EPP11278), or the home-made biotinylated chicken antibody, and the nano-gold conjugated home-made chicken antibody or a commercial rabbit antibody (EPP11278), had the higher sensitivity and specificity in this modified LFIA to establish calibration curves from the two recombinant METCAM/MUC18 proteins and were used for determining METCAM/MUC18 concentrations in serum specimens from normal individuals, benign prostatic hyperplasia (BPH) patients, prostatic intraepithelial neoplasia (PIN) patients, prostate cancer patients with various Gleason scores, and treated patients. (3) Results: Data obtained by this modified LFIA were statistically better than traditional LFIA and prostate-specific antigen (PSA) test. Interestingly, serum METCAM/MUC18 concentrations were higher in pre-malignant PIN patients than prostate cancer patients and both were higher than normal individuals, BPH patients, and treated patients. Serum METCAM/MUC18 concentrations were directly proportional to most serum PSA. (4) Conclusions: Elevated serum METCAM/MUC18 concentrations may be used for predicting the malignant potential of prostate cancer at an early premalignant (PIN) stage, which is not achievable by the current PSA test.

METCAM/MUC18 is a new early diagnostic biomarker for the malignant potential of prostate cancer: Validation with Western blot method, enzyme-linked immunosorbent assay and lateral flow immunoassay

BACKGROUND

METCAM/MUC18 expression was increased with the malignant progression of prostate cancer and also a bona fide metastatic gene, capable of initiating and driving the metastasis of a non-metastatic human prostate cancer cell line to multiple organs.

OBJECTIVE

We explored if METCAM/MUC18 was detectable in human serum and a novel biomarker to predict malignant propensity of prostate cancer.

MATERIALS AND METHODS

Two antibodies were identified by Western blot analysis having the highest sensitivity and specificity to establish calibration curves from the recombinant METCAM/MUC18 proteins. They were used in ELISA and LFIA to determine the METCAM/MUC18 concentrations in serum samples from 8 normal individuals, 4 BPH patients, 1 with PIN, 6 with high-grade prostate cancer, and 2 treated cancer patients.

RESULTS

Serum METCAM/MUC18 concentrations were statistically significantly higher in the patients with PIN and prostate cancer than those with BPH, the treated patients and normal individuals. The LFIA results were statistically better than ELISA and Western blot methods. Serum METCAM/MUC18 concentrations were in direct proportional to most of serum PSA concentrations.

A dermatan sulfate-functionalized biomimetic nanocarrier for melanoma targeted chemotherapy

Melanoma is a malignant tumor of melanocytes that is a serious threat to human health. Dermatan sulfate (DS) is a natural glycosaminoglycan. Inspired by the origin of DS, we report a DS-functionalized biomimetic chitosan nanocarrier (DCNP) for melanoma targeted chemotherapy. DS can anchor to the surface of the chitosan nanocarrier (CNP) by forming amide bond. The SN38/DCNP can rapidly release the anti-tumor drug under acidic conditions. The functionalization of DS not only promoted the specific uptake behavior of melanoma cells, but also up-regulated cleaved caspase-3 and PARP promote tumor cell apoptosis. In vivo model, DCNP reduced the non-specific distribution of SN38 in the circulation and other tissues, while shows superior tumor targeting ability. SN38/DCNP significantly inhibit tumor growth and improved the survival rate. Moreover, SN38/DCNP has a milder myelosuppressive effect. The above results indicated that DS could be used as an excellent targeting unit for the treatment of melanoma.

Soluble CD146, a cerebrospinal fluid marker for neuroinflammation, promotes blood-brain barrier dysfunction

The blood-brain barrier (BBB) dysfunction is an initial event of various neuroinflammatory diseases. However, the absence of reliable markers and mechanisms for BBB damage greatly limits the diagnosis and treatment of neuroinflammatory diseases. Soluble CD146 (sCD146) is mainly derived from vascular endothelial cells (ECs) and highly elevated in inflammatory settings. Based on a small cohort, our previous study showed that sCD146 is elevated in the cerebrospinal fluid (CSF) of multiple sclerosis (MS), which is accompanied with BBB damage. Nevertheless, whether sCD146 monitors and regulates the BBB dysfunction remains unknown.

Methods: Coupled serum and CSF samples from patients with or without neuroinflammatory diseases were collected via multicenter collaborations. sCD146 was measured by sandwich ELISA using anti-CD146 antibodies AA1 and AA98, both of which were generated in our laboratory. The correlations between sCD146 and other clinical parameters or inflammatory factors were analyzed by Spearman's correlation coefficient analysis. The role of sCD146 on BBB function was examined in an in vitro BBB model.

Results: Between July 20, 2011, and February 31, 2017, we collected coupled serum and CSF samples from 823 patients, of which 562 (68.3%) had neuroinflammatory diseases, 44 (5.3%) had remitting MS, and 217 (26.4%) had non-inflammatory neurological diseases (NIND). We found that sCD146 in CSF, but not in serum, is abnormally elevated in neuroinflammatory diseases (37.3 ± 13.3 ng/mL) compared with NIND (4.7 ± 2.9 ng/mL) and remitting MS (4.6 ± 3.5 ng/mL). Abnormally elevated CSF sCD146 is significantly correlated with the hyperpermeability-related clinical parameters of BBB and neuroinflammation-related factors. Moreover, CSF sCD146 shows higher sensitivity and specificity for evaluating BBB damage. Using an in vitro BBB model, we found that sCD146 impairs BBB function by promoting BBB permeability via an association with integrin αvβ1. Blocking integrin αvβ1 significantly attenuates sCD146-induced hyperpermeability of the BBB.

Conclusion: Our study provides convincing evidence that CSF sCD146 is a sensitive marker of BBB damage and neuroinflammation. Furthermore, sCD146 is actively involved in BBB dysfunction.

CD146 T cells in lung cancer: its function, detection, and clinical implications as a biomarker and therapeutic target

CD146 alternatively called melanoma cell adhesion molecule (MCAM), is a biomarker and therapeutic target of clinical significance. It is found on different cells including the endothelial cells and lymphocytes which participate in heterotypic and homotypic ligand-receptor. This review concentrated on the CD146 expression T cells (or lymphocytes) centering on Treg in lung cancer. Here, we have also considered the vigorous investigation of CD146 mainly acknowledged new roles, essential mechanisms and clinical implications of CD146 in cancer. CD146 has progressively become a significant molecule, particularly recognized as a novel biomarker, prognosis and therapy for cancer. Hence, targeting CD146 expression by utilization of methanol extracts of Calotropis procera leaf may be useful for the treatment of carcinogenesis.

CD146-mediated acquisition of stemness phenotype enhances tumour invasion and metastasis after EGFR-TKI resistance in lung cancer

INTRODUCTION

Tumours are more likely to metastasize after the development of resistance to EGFR-TKIs. CD146 is a multifunctional molecule and is implicated in tumour invasion and metastasis; however, its role in lung cancer has not been clearly established.

OBJECTIVE

Here, we aimed to explore the relationship between CD146 pathway and stem cell phenotype after EGFR-TKI resistance in lung cancer.

METHODS

EGFR-TKI-resistant cell lines were established by exposing parental cells to erlotinib/gefitinib. The CD146 level was measured by a western blot, RT-PCR and immunocytochemistry fluorescent. Cell migration was examined by the transwell assay and the scratch assay. Stemness phenotype genes were evaluated by RT-PCR and stem cell phenotype was observed by the microsphere formation assay.

RESULTS

CD146 and stemness phenotype genes increased while β-catenin decreased in acquired EGFR-TKI-resistant cell lines. CD146's over-expression induced the up-regulation of stemness-related genes and was inversely correlated with the β-catenin expression, which further increased the migration capability of resistant cancer cells. CD146's knockdown suppressed cell migration and stemness phenotype.

CONCLUSIONS

CD146 molecule contributes to the stemness phenotype and migration in EGFR-TKI-resistant cells. CD146 might be a potential therapeutic target for EGFR-TKI-resistant lung cancer or metastasis prevention.

Therapeutic Targeting of CD146/MCAM Reduces Bone Metastasis in Prostate Cancer

Prostate Cancer is the most common cancer and the second leading cause of cancer-related death in males. When prostate cancer acquires castration resistance, incurable metastases, primarily in the bone, occur. The aim of this study is to test the applicability of targeting melanoma cell adhesion molecule (MCAM; CD146) with a mAb for the treatment of lytic prostate cancer bone metastasis. We evaluated the effect of targeting MCAM using in vivo preclinical bone metastasis models and an in vitro bone niche coculture system. We utilized FACS, cell proliferation assays, and gene expression profiling to study the phenotype and function of MCAM knockdown in vitro and in vivo. To demonstrate the impact of MCAM targeting and therapeutic applicability, we employed an anti-MCAM mAb in vivo. MCAM is elevated in prostate cancer metastases resistant to androgen ablation. Treatment with DHT showed MCAM upregulation upon castration. We investigated the function of MCAM in a direct coculture model of human prostate cancer cells with human osteoblasts and found that there is a reduced influence of human osteoblasts on human prostate cancer cells in which MCAM has been knocked down. Furthermore, we observed a strongly reduced formation of osteolytic lesions upon bone inoculation of MCAM-depleted human prostate cancer cells in animal model of prostate cancer bone metastasis. This phenotype is supported by RNA sequencing (RNA-seq) analysis. Importantly, in vivo administration of an anti-MCAM human mAb reduced the tumor growth and lytic lesions. These results highlight the functional role for MCAM in the development of lytic bone metastasis and suggest that MCAM is a potential therapeutic target in prostate cancer bone metastasis. IMPLICATIONS: This study highlights the functional application of an anti-MCAM mAb to target prostate cancer bone metastasis.

Clinical significance of melanoma cell adhesion molecule CD146 and VEGFA expression in epithelial ovarian cancer

Ovarian cancer is the fifth most common type of cancer in females; however, its asymptomatic progression and the lack of an efficient screening strategy leads to late diagnosis. The present study aimed to investigate the expression levels of cluster of differentiation (CD)146 and vascular endothelial growth factor A (VEGFA) in epithelial ovarian cancer, and their clinical significance. A total of 52 ovarian samples were tested, of which 22 were from patients with epithelial ovarian cancer and 30 were from non-cancer patients. The relative gene expression of CD146 and VEGFA was quantified using reverse transcription-quantitative polymerase chain reaction analysis. Western blotting was used to determine the protein expression levels. The relative gene expression levels of CD146 and VEGFA in tumor tissues were significantly increased compared with the control (4.92±0.44 vs. 1.05±0.06 and 3.08±0.17 vs. 1.06±0.07, P<0.01). The protein expression levels of CD146 and VEGFA in tumor tissue were also significantly increased compared with the control (0.70±0.02 vs. 0.41±0.07 and 0.54±0.01 vs. 0.26±0.01, P<0.01). There was a positive correlation between the expression levels of CD146 and VEGFA genes (r=0.78) and between the two proteins (r=0.69). Dot density frequency analysis indicated that CD146 and VEGFA were specifically present in tumor tissues. In conclusion, CD146 and VEGFA are co-overexpressed in ovarian cancer; their potential as tumor biomarkers or therapeutic targets for the treatment of ovarian cancer requires further investigation.

Gene expression analysis of Atlantic salmon gills reveals mucin 5 and interleukin 4/13 as key molecules during amoebic gill disease

Amoebic gill disease (AGD) is one of the main diseases affecting Atlantic salmon (Salmo salar L.) mariculture. Hallmarks of AGD are hyperplasia of the lamellar epithelium and increased production of gill mucus. This study investigated the expression of genes involved in mucus secretion, cell cycle regulation, immunity and oxidative stress in gills using a targeted 21-gene PCR array. Gill samples were obtained from experimental and natural Neoparamoeba perurans infections, and sampling points included progressive infection stages and post-freshwater treatment. Up-regulation of genes related to mucin secretion and cell proliferation, and down-regulation of pro-inflammatory and pro-apoptotic genes were associated with AGD severity, while partial restoration of the gill homeostasis was detected post-treatment. Mucins and Th2 cytokines accoun ted for most of the variability observed between groups highlighting their key role in AGD. Two mucins (muc5, muc18) showed differential regulation upon disease. Substantial up-regulation of the secreted muc5 was detected in clinical AGD, and the membrane bound muc18 showed an opposite pattern. Th2 cytokines, il4/13a and il4/13b2, were significantly up-regulated from 2 days post-infection onwards, and changes were lesion-specific. Despite the differences between experimental and natural infections, both yielded comparable results that underline the importance of the studied genes in the respiratory organs of fish, and during AGD progression.

A novel anti-CD146 antibody specifically targets cancer cells by internalizing the molecule

CD146 is an adhesion molecule present on many tumors (melanoma, kidney, pancreas, breast, ...). In addition, it has been shown to be expressed on vascular endothelial and smooth muscle cells. Generating an antibody able to specifically recognize CD146 in cancer cells (designated as tumor CD146), but not in normal cells, would thus be of major interest for targeting tumor CD146 without affecting the vascular system.

We thus generated antibodies against the extracellular domain of the molecule produced in cancer cells and selected an antibody that specifically recognizes tumor CD146. This antibody (TsCD146 mAb) was able to detect CD146-positive tumors in human biopsies and in vivo, by PET imaging, in a murine xenograft model. In addition, TsCD146 mAb antibody was able to specifically detect CD146-positive cancer microparticles in the plasma of patients. TsCD146 mAb displayed also therapeutic effects since it was able to reduce the growth of human CD146-positive cancer cells xenografted in nude mice. This effect was due to a decrease in the proliferation and an increase in the apoptosis of CD146-positive cancer cells after TsCD146-mediated internalization of the cell surface CD146.

Thus, TsCD146 mAb could be of major interest for diagnostic and therapeutic strategies against CD146-positive tumors in a context of personalized medicine.

CD146, a novel target of CD44-signaling, suppresses breast tumor cell invasion

Background

We have previously validated three novel CD44-downstream positively regulated transcriptional targets, including Cortactin, Survivin and TGF-β2, and further characterized the players underlying their separate signaling pathways. In the present study, we identified CD146 as a potential novel target, negatively regulated by CD44. While the exact function of CD146 in breast cancer (BC) is not completely understood, substantial evidence from our work and others support the hypothesis that CD146 is a suppressor of breast tumor progression.

Methods

Therefore, using molecular and pharmacological approaches both in vitro and in breast tissues of human samples, the present study validated CD146 as a novel target of CD44-signaling suppressed during BC progression.

Results

Our results revealed that CD44 activation could cause a substantial decrease of CD146 expression with an equally notable converse effect upon CD44-siRNA inhibition. More interestingly, activation of CD44 decreased cellular CD146 and increased soluble CD146 through CD44-dependent activation of MMP.

Conclusion

Here, we provide a possible mechanism by which CD146 suppresses BC progression as a target of CD44-downstream signaling, regulating neovascularization and cancer cell motility.

Immunohistochemical Expression of MCAM/CD146 in Canine Melanoma

MCAM/CD146 (melanoma cell adhesion molecule/CD146) is a transmembrane immunoglobulin superfamily cell adhesion molecule involved in transendothelial migration and signal transduction. It is expressed in melanoma, squamous cell carcinoma, prostatic, ovarian, cervical and endometrial cancers and promotes tumour growth, angiogenesis and metastasis. Melanoma is the most common malignant oral tumour of dogs and also arises in the skin, nail bed and footpad. The aim of this study was to investigate the immunohistochemical expression of MCAM/CD146 in 51 canine melanomas, including oral, cutaneous and ocular tumours. Seventeen of the 51 (33.3%) cases were negative, eight (15.7%) were weakly positive, seven (13.7%) were moderately positive and 19 (37.3%) were strongly positive. MCAM/CD146 was expressed by both oral and cutaneous melanomas; however, the intensity and the extent of the immunoreactivity was higher in oral (P = 0.009) than in cutaneous tumours (P = 0.058). Most ocular melanomas did not express MCAM/CD146 (P = 0.256). Expression of MCAM/CD146 by canine melanomas may suggest the molecule as a target for treatment, especially in oral melanomas.

Evaluation of CD146 as Target for Radioimmunotherapy against Osteosarcoma

BACKGROUND

Osteosarcoma is a rare form of cancer but with a substantial need for new active drugs. There is a particular need for targeted therapies to combat metastatic disease. One possible approach is to use an antibody drug conjugate or an antibody radionuclide conjugate to target the osteosarcoma metastases and circulating tumor cells. Herein we have evaluated a radiolabeled monoclonal antibody targeting CD146 both in vitro and in vivo.

METHODS AND RESULTS

A murine monoclonal anti-CD146 IgG1 isotype antibody, named OI-3, was developed along with recombinant chimeric versions with human IgG1 or human IgG3 Fc sequences. Using flow cytometry, selective binding of OI-3 to human osteosarcoma cell lines OHS, KPDX and Saos-2 was confirmed. The results confirm a higher expression level of CD146 on human osteosarcoma cells than HER2 and EGFR; antigens targeted by commercially available therapeutic antibodies. The biodistribution of 125I-labeled OI-3 antibody variants was compared with 125I-labeled chimeric anti-EGFR antibody cetuximab in nude mice with subcutaneous OHS osteosarcoma xenografts. OI-3 was able to target CD146 expressing tumors in vivo and showed improved tumor to tissue targeting ratios compared with cetuximab. Subsequently, the three OI-3 variants were conjugated with p-SCN-Bn-DOTA and labeled with a more therapeutically relevant radionuclide, 177Lu, and their biodistributions were studied in the nude mouse model. The 177Lu-labeled OI-3 variants were stable and had therapeutically relevant biodistribution profiles. Dosimetry estimates showed higher absorbed radiation dose to tumor than all other tissues after administration of the chimeric IgG1 OI-3 variant.

CONCLUSION

Our results indicate that CD146 can be targeted in vivo by the radiolabeled OI-3 antibodies.

Frequent and increased expression of human METCAM/MUC18 in cancer tissues and metastatic lesions is associated with the clinical progression of human ovarian carcinoma

OBJECTIVES

Human METCAM/MUC18 (huMETCAM/MUC18), a cell adhesion molecule, plays an important role in the progression of several epithelial cancers; however, its role in the progression of epithelial ovarian cancers is unknown. To initiate the study we determined expression of this protein in normal and cancerous ovarian tissues, cystadenomas, metastatic lesions, and ovarian cancer cell lines.

MATERIALS AND METHODS

Immunoblotting and immunohistochemical (IHC) methods were used to determine huMETCAM/MUC18 expression in lysates of frozen and formalin-fixed, paraffin-embedded tissue sections of normal human ovaries, and ovarian (benign) cystadenomas, carcinomas and metastatic lesions. We also determined expression levels of several downstream effectors of METCAM/MUC18 in these tissues.

RESULTS

HuMETCAM/MUC18 levels in ovarian carcinomas and metastatic lesions were significantly higher than in normal tissues and cystadenomas. IHC results showed that expression of huMETCAM/MUC18 in normal tissues and cystadenomas was mostly absent from epithelial cells, but in carcinomas and metastatic lesions it was localized to epithelial cells. In higher pathological grades of ovarian cancer and metastatic lesions, the percentage of cells stained in IHC was increased. Thirty percent of normal tissues weakly expressed the huMETCAM/MUC18 antigen, but 70% of cancer tissues and 100% of metastatic lesions expressed the antigen. Expression levels of several downstream effectors of huMETCAM/MUC18, Bcl2, PCNA and VEGF, were elevated in cancerous tissues, however, not that of Bax. The phospho-AKT/AKT ratio was elevated in metastatic lesions.

CONCLUSION

Upexpression of huMETCAM/MUC18 may be a marker for the malignant potential of ovarian carcinomas. Progression of ovarian cancer may involve increased signaling in anti-apoptosis, proliferation, survival/proliferation pathway, and angiogenesis.

Exploring the role and diversity of mucins in health and disease with special insight into non-communicable diseases

Mucins are major glycoprotein components of the mucus that coats the surfaces of cells lining the respiratory, digestive, gastrointestinal and urogenital tracts. They function to protect epithelial cells from infection, dehydration and physical or chemical injury, as well as to aid the passage of materials through a tract i.e., lubrication. They are also implicated in the pathogenesis of benign and malignant diseases of secretory epithelial cells. In Human there are two types of mucins, membrane-bound and secreted that are originated from mucous producing goblet cells localized in the epithelial cell layer or in mucous producing glands and encoded by MUC gene. Mucins belong to a heterogeneous family of high molecular weight proteins composed of a long peptidic chain with a large number of tandem repeats that form the so-called mucin domain. The molecular weight is generally high, ranging between 0.2 and 10 million Dalton and all mucins contain one or more domains which are highly glycosylated. The size and number of repeats vary between mucins and the genetic polymorphism represents number of repeats (VNTR polymorphisms), which means the size of individual mucins can differ substantially between individuals which can be used as markers. In human it is only MUC1 and MUC7 that have mucin domains with less than 40% serine and threonine which in turn could reduce number of PTS domains. Mucins can be considered as powerful two-edged sword, as its normal function protects from unwanted substances and organisms at an arm's length while, malfunction of mucus may be an important factor in human diseases. In this review we have unearthed the current status of different mucin proteins in understanding its role and function in various non-communicable diseases in human with special reference to its organ specific locations. The findings described in this review may be of direct relevance to the major research area in biomedicine with reference to mucin and mucin associated diseases.

Significance of expression of human METCAM/MUC18 in nasopharyngeal carcinomas and metastatic lesions

Human METCAM/MUC18, a cell adhesion molecule (CAM) in the immunoglobulin-like gene super family, plays a dual role in the progression of several epithelium cancers; however, its role in the nasopharyngeal carcinoma (NPC) remains unclear. To initiate the study we determined human METCAM/MUC18 expression in tissue samples of normal nasopharynx (NP), NPCs, and metastatic lesions, and in two established NPC cell lines. Immunoblotting analysis was used for the determination in lysates of frozen tissues, and immunohistochemistry (IHC) for expression in formalin-fixed, paraffin-embedded tissue sections of 7 normal nasopharynx specimens, 94 NPC tissue specimens, and 3 metastatic lesions. Human METCAM/MUC18 was expressed in 100% of the normal NP, not expressed in 73% of NPC specimens (or expressed at very low levels in only about 27% of NPC specimens), and expressed again in all of the metastatic lesions. The level of human METCAM/MUC18 expression in NPC tissues was about one fifth of that in the normal NP and metastatic lesions. The low level of human METCAM/ MUC18 expression in NPC specimens was confirmed by a weak signal of RT-PCR amplification of the mRNA. Low expression levels of human METCAM/MUC18 in NPC tissues were also reflected in the seven established NPC cell lines. These findings provided the first evidence that diminished expression of human METCAM/MUC18 is an indicator for the emergence of NPC, but increased expression then occurs with metastatic progression, suggesting that huMETCAM/MUC18, perhaps similar to TGF-β, may be a tumor suppressor, but a metastasis promoter for NPC.

Quantitative proteomics reveals ER-α involvement in CD146-induced epithelial-mesenchymal transition in breast cancer cells

The cell adhesion molecule CD146 is a novel inducer of epithelial-mesenchymal transition (EMT), which was associated with triple-negative breast cancer (TNBC). To gain insights into the complex networks that mediate CD146-induced EMT in breast cancers, we conducted a triple Stable Isotope Labeling with Amino Acids in Cell Culture (SILAC), to analyze whole cell protein profiles of MCF-7 cells that had undergone gradual EMT upon CD146 expression from moderate to high levels. In this study, we identified 2293 proteins in total, of which 103 exhibited changes in protein abundance that correlated with CD146 expression levels, revealing extensive morphological and biochemical changes associated with EMT. Ingenuity Pathway Analysis (IPA) showed that estrogen receptor (ER) was the most significantly inhibited transcription regulator during CD146-induced EMT. Functional assays further revealed that ER-α expression was repressed in cells undergoing CD146-induced EMT, whereas re-expression of ER-α abolished their migratory and invasive behavior. Lastly, we found that ER-α mediated its effects on CD146-induced EMT via repression of the key EMT transcriptional factor Slug. Our study revealed the molecular details of the complex signaling networks during CD146-induced EMT, and provided important clues for future exploration of the mechanisms underlying the association between CD146 and TNBC as observed in the clinic.

BIOLOGICAL SIGNIFICANCE

This study used a proteomics screen to reveal molecular changes mediated by CD146-induced epithelial-mesenchymal transition (EMT) in breast cancer cells. Estrogen receptor (ER) was found to be the most significantly inhibited transcription regulator, which mediated its effects on CD146-induced EMT via repression of the transcriptional factor Slug. Elucidation of protein interaction networks and signal networks generated from 103 significantly changed proteins would facilitate future investigation into the mechanisms underlying CD146 induced-EMT in breast cancers.

CD146, a multi-functional molecule beyond adhesion

CD146 is a cell adhesion molecule (CAM) that is primarily expressed at the intercellular junction of endothelial cells. CD146 was originally identified as a tumor marker for melanoma (MCAM) due to its existence only in melanoma but not in the corresponding normal counterpart. However CD146 is not just a CAM for the inter-cellular and cell-matrix adhesion. Recent evidence indicates that CD146 is actively involved in miscellaneous processes, such as development, signaling transduction, cell migration, mesenchymal stem cells differentiation, angiogenesis and immune response. CD146 has increasingly become an important molecule, especially identified as a novel bio-marker for angiogenesis and for cancer. Here we have reviewed the dynamic research of CD146, particularly newly identified functions and the underlying mechanisms of CD146.

A novel function of MUC18: amplification of lung inflammation during bacterial infection

Bacterial infection plays a critical role in exacerbations of various lung diseases, including chronic pulmonary obstructive disease (COPD) and asthma. Excessive lung inflammation is a prominent feature in disease exacerbations, but the underlying mechanisms remain poorly understood. Cell surface glycoprotein MUC18 (alias CD146 or melanoma cell adhesion molecule) has been shown to promote metastasis in several tumors, including melanoma. We explored the function of MUC18 in lung inflammatory responses to bacteria (eg, Mycoplasma pneumoniae) involved in lung disease exacerbations. MUC18 expression was increased in alveolar macrophages from lungs of COPD and asthma patients, compared with normal healthy human subjects. Mouse alveolar macrophages also express MUC18. After M. pneumoniae lung infection, Muc18(-/-) mice exhibited lower levels of the lung proinflammatory cytokines KC and TNF-α and less neutrophil recruitment than Muc18(+/+) mice. Alveolar macrophages from Muc18(-/-) mice produced less KC than those from Muc18(+/+) mice. In Muc18(-/-) mouse alveolar macrophages, adenovirus-mediated MUC18 gene transfer increased KC production. MUC18 amplified proinflammatory responses in alveolar macrophages, in part through enhancing the activation of nuclear factor-κB (NF-κB). Our results demonstrate, for the first time, that MUC18 exerts a proinflammatory function during lung bacterial infection. Up-regulated MUC18 expression in lungs (eg, in alveolar macrophages) of COPD and asthma patients may contribute to excessive inflammation during disease exacerbations.

Dual Roles of METCAM in the Progression of Different Cancers

METCAM, an integral membrane cell adhesion molecule (CAM) in the Ig-like gene superfamily, is capable of performing typical functions of CAMs, such as mediating cell-cell and cell-extracellular interactions, crosstalk with intracellular signaling pathways, and modulating social behaviors of cells. METCAM is expressed in about nine normal cells/tissues. Aberrant expression of METCAM has been associated with the progression of several epithelial tumors. Further in vitro and in vivo studies show that METCAM plays a dual role in the progression of different tumors. It can promote the malignant progression of several tumors. On the other hand, it can suppress the malignant progression of other tumors. We suggest that the role of METCAM in the progression of different cancer types may be modulated by different intrinsic factors present in different cancer cells and also in different stromal microenvironment. Many possible mechanisms mediated by this CAM during early tumor development and metastasis are suggested.

CD146, an epithelial-mesenchymal transition inducer, is associated with triple-negative breast cancer

The epithelial-mesenchymal transition (EMT) plays an important role in breast cancer metastasis, especially in the most aggressive and lethal subtype, "triple-negative breast cancer" (TNBC). Here, we report that CD146 is a unique activator of EMTs and significantly correlates with TNBC. In epithelial breast cancer cells, overexpression of CD146 down-regulated epithelial markers and up-regulated mesenchymal markers, significantly promoted cell migration and invasion, and induced cancer stem cell-like properties. We further found that RhoA pathways positively regulated CD146-induced EMTs via the key EMT transcriptional factor Slug. An orthotopic breast tumor model demonstrated that CD146-overexpressing breast tumors showed a poorly differentiated phenotype and displayed increased tumor invasion and metastasis. We confirmed these findings by conducting an immunohistochemical analysis of 505 human primary breast tumor tissues and found that CD146 expression was significantly associated with high tumor stage, poor prognosis, and TNBC. CD146 was expressed at abnormally high levels (68.9%), and was strongly associated with E-cadherin down-regulation in TNBC samples. Taken together, these findings provide unique evidence that CD146 promotes breast cancer progression by induction of EMTs via the activation of RhoA and up-regulation of Slug. Thus, CD146 could be a therapeutic target for breast cancer, especially for TNBC.

Cell surface glycoproteomic analysis of prostate cancer-derived PC-3 cells

Most clinically approved biomarkers of cancer are glycoproteins, and those residing on the cell surface are of particular interest in biotherapeutics. We report a method for selective labeling, affinity enrichment, and identification of cell-surface glycoproteins. PC-3 cells and primary human prostate cancer tissue were treated with peracetylated N-azidoacetylgalactosamine, resulting in metabolic labeling of cell surface glycans with the azidosugar. We used mass spectrometry to identify over 70 cell surface glycoproteins and biochemically validated CD146 and integrin beta-4, both of which are known to promote metastatic behavior. These results establish cell-surface glycoproteomics as an effective technique for discovery of cancer biomarkers.

Up-regulation of MUC18 in airway epithelial cells by IL-13: implications in bacterial adherence

Airway bacterial infections are a major problem in lung diseases, including asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis. Increased Th2 cytokines, such as IL-13, are observed in lung diseases and may contribute to bacterial infections. How Th2 cytokines affect bacterial infection remains unknown. MUC18, an adhesion molecule shown to be involved in the pathogenesis of malignant melanoma, has been recently identified in airway epithelial cells of patients with COPD. We investigated MUC18 regulation by IL-13 and the role of MUC18 in bacterial adherence to epithelial cells. Human airway tissues, brushed bronchial epithelial cells from normal subjects and subjects with asthma, and epithelial cell lines (e.g., HEK293 cells) were used to study the regulation of MUC18 by IL-13 and the involvement of MUC18 in bacterial (e.g., Mycoplasma pneumoniae [Mp] and nontypeable Haemophilus influenzae [NTHi]) adherence to epithelial cells. Asthmatic bronchial epithelium expressed higher levels of MUC18 than normal bronchial epithelium. IL-13 increased MUC18 in cultured bronchial epithelial cells from normal subjects and particularly from subjects with asthma. IL-13-induced MUC18 expression may be modulated in part through transcription factor specificity protein 1. Overexpression of human MUC18 in HEK293 cells increased cell-associated Mp and NTHi levels. Moreover, MUC18 was shown to directly interact with Mp and NTHi. These results for the first time show that an allergic airway milieu (e.g., IL-13) increases MUC18 expression, which may contribute to increased bacterial infection/colonization in asthma and other lung diseases.

Characterization of dental pulp stem cells from impacted third molars cultured in low serum-containing medium

We isolated and expanded stem cells from dental pulp from extracted third molars using an innovative culture method consisting of low serum-containing medium supplemented with epidermal growth factor and platelet-derived growth factor BB. We evaluated the differentiation potential of these cells when they were growing either adherently or as micromass/spheroid cultures in various media. Undifferentiated and differentiated cells were analyzed by flow cytometry, immunocytochemistry and immunoblotting. The flow cytometry results showed that the dental pulp stem cells (DPSCs) were positive for mesenchymal stromal cell markers, but negative for hematopoietic markers. Immunocytochemical and/or immunoblotting analyses revealed the expression of numerous stem cell markers, including nanog, Sox2, nestin, Musashi-1 and nucleostemin, whereas they were negative for markers associated with differentiated neural, vascular and hepatic cells. Surprisingly, the cells were only slightly positive for α-smooth muscle actin, and a heterogeneous expression of CD146 was observed. When cultured in osteogenic media, they expressed osteonectin, osteopontin and procollagen I, and in micromass cultures, they produced collagen I. DPSCs cultured in TGF-β1/3-supplemented media produced extracellular matrix typical of cartilaginous tissue. The addition of vascular endothelial growth factor to serum-free media resulted in the expression of endothelial markers. Interestingly, when cultured in neurogenic media, DPSCs exhibited de novo or upregulated markers of undifferentiated and differentiated neural cells. Collectively, our data show that DPSCs are self-renewing and able to express markers of bone, cartilage, vascular and neural tissues, suggesting their multipotential capacity. Their easy accessibility makes these cells a suitable source of somatic stem cells for tissue engineering.

Immunocytochemistry of CD146 is useful to discriminate between malignant pleural mesothelioma and reactive mesothelium

Malignant pleural mesothelioma is a refractory tumor with poor prognosis associated with asbestos exposure. Pleural effusion is frequently observed in patients with malignant pleural mesothelioma, and cytological analysis is effective to detect malignant pleural mesothelioma. However, cytological discrimination between malignant pleural mesothelioma and reactive mesothelium is often difficult. Increased expression of CD146, a cell adhesion molecule, has been reported to be closely associated with an advanced stage of malignant melanoma, prostate cancer, and ovarian cancer. In this study, to evaluate the diagnostic utility of CD146 for discrimination between malignant pleural mesothelioma and reactive mesothelium, we examined immunocytochemical expression of CD146 in malignant pleural mesothelioma and reactive mesothelium using two clones of CD146 antibody, OJ79 and EPR3208, on smear specimens of effusion fluids. Immunocytochemical stains were semiquantitatively scored on the basis of immunostaining intensity (0, negative; 1, weak positive; 2, moderate positive; and 3, strong positive). CD146 expression was detected in 15 of 16 malignant pleural mesothelioma with median immunostaining score of 3 by OJ79, and in 19 of 21 malignant pleural mesothelioma with median immunostaining score of 2 by EPR3208. Strong immunoreactivity of CD146 was observed at the apposing surfaces of cell-cell interactions on the plasma membrane of mesothelioma cells. In addition, one OJ79-negative case of malignant pleural mesothelioma was positive for CD146 by EPR3208 and two EPR3208-negative cases of malignant pleural mesothelioma were CD146 positive by OJ79, showing that all 23 malignant pleural mesothelioma cases were positive for CD146 by either OJ79 or EPR3208. On the other hand, CD146 expression was undetectable in all reactive mesothelium cases by OJ79 and EPR3208. The sensitivity of OJ79 and EPR3208 was 94 and 90%, respectively, and the specificity was 100% for both clones. We propose that CD146 is a sensitive and specific immunocytochemical marker enabling differential diagnosis of malignant pleural mesothelioma from reactive mesothelium.

Synergistic killing effect between vorinostat and target of CD146 in malignant cells

PURPOSE

Although histone deacetylase inhibitors (HDACi) are emerging as a new class of anticancer agents, one of the most significant concerns is that interactions with a wide array of substrates using these agents might initiate both therapeutic and undesired protective responses. Here, we sought to identify the potential protective reactions initiated by HDACi and determine whether targeting these reactions would enhance the antitumoral activity of HDACi.

EXPERIMENTAL DESIGN

Gene expression profiles were analyzed by cDNA microarray in Molt-4 cells before and after treatment of vorinostat. Induction of CD146 by vorinostat was examined in a wide range of tumors and nonmalignant cells. AA98, an anti-CD146 monoclonal antibody, was used to target CD146 function. Synergistic antitumoral and antiangiogenic effects between AA98 and vorinostat were examined both in vitro and in vivo. The potential effect of combined AA98 and vorinostat treatment on the AKT pathway was determined by Western blotting.

RESULTS

The induction of CD146 is a common phenomenon in vorinostat-treated cancer but not in nonmalignant cells. Targeting of CD146 with AA98 substantially enhanced vorinostat-induced killing via the suppression of activation of AKT pathways in cancer cells. Moreover, AA98 in combination with vorinostat significantly inhibited angiogenesis. In vivo, AA98 synergized with vorinostat to inhibit tumor growth and metastasis.

CONCLUSION

The present study provided the first evidence that an undesired induction of CD146 could serve as a protective response to offset the antitumor efficacy of vorinostat. On the other hand, targeting CD146 in combination with vorinostat could be exploited as a novel strategy to more effectively kill cancer cells.

Towards understanding the mode of action of the multifaceted cell adhesion receptor CD146

CD146, also known as melanoma cell adhesion molecule or MCAM, is a key cell adhesion protein in vascular endothelial cell activity and angiogenesis. CD146 promotes tumor progression of many cancers including melanoma and prostate. Strikingly, its expression is frequently lost in breast carcinoma cells, and it may act as a suppressor of breast cancer progression. While upstream mechanisms regulating CD146 are well documented, our understanding of the downstream molecular events underlying its mode of action remains to be elucidated. This review aims to focus on the progress in understanding the signaling mechanisms and the functional relevance of CD146, a multifaceted molecule, in cancer with particular emphasis on its role in inhibiting breast cancer progression.

Hypermethylation of MCAM gene is associated with advanced tumor stage in prostate cancer

BACKGROUND

DNA methylation has emerged as a promising biomarker for prostate cancer detection. In this report, we screened 36 candidate genes generated by a bioinformatic analysis of the human genome, and found that the melanoma cell adhesion molecule (MCAM) was an excellent candidate for cancer-specific methylation in prostate cancer.

METHODS

Direct sequencing of bisulfite-treated genomic DNA, conventional methylation-specific PCR (MSP), real-time quantitative methylation-specific PCR, immunohistochemistry, colony formation assay, and statistical analysis.

RESULTS

We found that the melanoma cell adhesion molecule (MCAM) gene promoter was specifically methylated in prostate cancer cell lines and primary prostate cancer (PCa) but not in non-neoplastic prostate (BPH) tissues by direct sequencing of bisulfite-treated genomic DNA and conventional methylation-specific PCR (MSP). Further analysis with quantitative MSP showed greater hypermethylation of the MCAM promoter (80%, 70/88) in primary prostate cancer compared to 12.5% (3/24) in BPH. Prostatic intraepithelial neoplasias (PIN), potential precursors of prostate carcinoma, showed an intermediate methylation rate of 23% (7/30). We further observed that MCAM promoter methylation was directly correlated with tumor stage (pT3+pT4) (P = 0.001) and Gleason score (P = 0.018) in primary prostate carcinoma.

CONCLUSIONS

Our results suggest that MCAM promoter hypermethylation deserves further attention as a potential diagnostic prostatic DNA marker in human prostate cancer.

Expression and distribution of MUC18 in human uveal melanoma

The immunoglobulin superfamily protein MUC18 is involved in transendothelial migration and signal transduction, and is expressed in malignancies including cutaneous melanoma. Recent in vitro studies showed evidence of increased MUC18 protein in some uveal melanoma cell lines with an increased potential for invasion. We assessed seven uveal and three metastasis-derived melanoma cell lines for the expression of MUC18 mRNA and protein by RT-PCR, and immunoblotting and immunocytochemistry, respectively. We also examined the expression and distribution of MUC18 in paraffin sections of primary uveal melanomas (n = 23; 5/23 spindle; 18/23 mixed and epithelioid) and normal eyes (n = 3) using a polyclonal goat anti-human antibody to MUC18 visualized with peroxidase and Vector NovaRED. Distribution and intensity of immunostaining was graded semi-quantitatively (grade 0 to 3) by 2 independent observers. All cell lines expressed MUC18 mRNA and protein ( approximately 130 kDa), and showed punctate cell membrane MUC18 immunostaining. Primary melanomas displayed heterogeneous cell membrane and cytoplasmic MUC18, with moderate to strong immunolabelling (> or =grade 2) in approximately 70% of tumours. Vasculature in tumours and in retina and choroid of all melanoma-affected and normal eyes showed intense MUC18 immunostaining. These observations further suggest a role for MUC18 in uveal melanoma growth; moreover, interactions between MUC18-positive melanoma cells and vasculature may be important for the hematogenous spread of cells during metastases.

M-CAM expression as marker of poor prognosis in epithelial ovarian cancer

Currently available clinico-pathologic criteria provide an imperfect assessment of outcome for patients with advanced epithelial ovarian cancer (EOC). Identification of prognostic factors related to tumor biology might improve this assessment. We investigated the prognostic significance of the melanoma cell adhesion molecule (M-CAM) in EOC. Using the same antibody, M-CAM expression was tested by Western blotting in protein extracts and by immunohistochemestry in tissue microarrays generated from 133 consecutively resected, well characterized EOC samples. Fisher test, Kaplan-Meier method and Cox proportional hazards analysis were used to relate M-CAM expression to clinico-pathological variables and to time to progression (TTP) and overall survival (OS). In vitro biochemical analysis showed a progressively increased M-CAM expression from normal to malignant cells. M-CAM protein, detected immunohistochemically, was significantly associated with advanced tumor stage, serous and undifferentiated histotype, extent of residual disease and p53 accumulation. Presence or absence of M-CAM significantly divided patients according to their TTP (median, 22 vs. 79 months, respectively; log-rank p = 0.001) and OS (median, 42 vs. 131 months, respectively; log-rank p = 0.0003). In the subgroup of advanced stage patients who achieved complete response after front-line treatment, M-CAM expression and absence of residual disease were significantly associated with shorter TTP (p = 0.003, HR 5.25, 95% Cl 1.79-15.41 and p = 0.011, HR 3.77, 95% Cl 1.36-10.49 respectively) at the multivariate level. In the same sub-group of patients, M-CAM expression remained the only parameter significantly associated with OS (p = 0.005, HR 3.35, 95% Cl 1.42-6.88). M-CAM is a marker of early relapse and poorer outcome in EOC. In particular, M-CAM expression identifies a subgroup of front-line therapy-responding patients who undergo dramatic relapses, thus helping to better select patients who might benefit from new/alternative therapeutic modalities.

Oral treatment of the TRAMP mice with doxazosin suppresses prostate tumor growth and metastasis

BACKGROUND

We used the TRAMP mouse model for testing the effect of oral doxazosin treatment on the in vivo prostate tumor growth and metastasis.

METHODS

Five groups of TRAMP mice at different ages were orally fed with 1 mg/kg of doxazosin or DMSO for 45-196 days. At the end of oral treatment, tumor weight was determined, and metastasis to multiple organs examined. The levels of MUC18, Bcl-2, Bax, caspase-3, poly (ADP-ribose) polymerase (PARP), phospho (Ser473)-AKT, and Ki-67 in the mouse prostate tumors were determined.

RESULTS

Oral treatment of the TRAMP mice with doxazosin for 45-81 days did not decrease the size of preexisting prostate tumors, but it limited the metastasis to peri-aortic lymph nodes. A prolonged treatment of TRAMP mice with doxazosin (156-196 days), if administered early, decreased the prostate tumor weight and completely suppressed metastasis. The doxazosin treatment did not further decrease the expression of an already low level of Bcl-2 in all prostate tumors, but it increased the expression of Bax, and the activation of caspase-3, and the cleavage of a downstream substrate, PARP. The treatment reduced the expression of MUC18, phospho (Ser473)-AKT, and Ki-67. The treatment in the early phase appeared to promote prostate tumor growth and increased the expression of a proliferative index, Ki-67.

CONCLUSIONS

Doxazosin, if administered early, may be useful for preventing the prostate tumor formation, and also for limiting or completely suppressing the metastasis of prostate cancer in the TRAMP model. The mechanism of doxazosin is consistent with the established hypothesis.

INCREASED EXPRESSION OF MUC18 CORRELATES WITH THE METASTATIC PROGRESSION OF MOUSE PROSTATE ADENOCARCINOMA IN THE TRAMP MODEL

PURPOSE

The transgenic adenocarcinoma mouse prostate (TRAMP) model is a paradigm that closely mimics the progression of clinical prostate cancer. We have previously reported that MUC18, a cell adhesion molecule in the Ig gene superfamily, is a marker as well as an important mediator for the metastatic potential of human prostate cancer cells. In this study we investigated the possible correlation of increased MUC18 expression with the malignant progression of prostate cancer in the TRAMP model.

MATERIALS AND METHODS

We used immunohistochemistry, Western blot and reverse transcriptase-polymerase chain reaction analyses to determine MUC18 expression in the prostate gland of 178 to 282-day-old TRAMP positive males with a prostate tumor size of 0.4 to 12.7 gm. Eight normal prostates, 10 prostates with high grade prostatic intraepithelial neoplasia (PIN), 24 prostates with primary prostate cancer, 10 metastatic lesions from 50 pure C57BL/6 TRAMP mice (Wu colony) and 2 normal prostates, 2 prostates with high grade PIN, 6 prostates with primary prostate cancer and 4 metastatic lesions from 10 [C57BL/6 TRAMP x FVB] F1 mice (NMG colony) were used.

RESULTS

We found that mouse MUC18 was expressed in all (100%) high grade PIN, adenocarcinomas and metastatic lesions. All mice bearing primary prostate tumors had prostate cancer metastatic to the peri-aortic lymph nodes and some had it to other organs (liver, lung, kidney, testes, seminal vesicles and abdominal cavity). In contrast, prostates from 10 nontransgenic littermates did not have detectable MUC18 expression.

CONCLUSIONS

MUC18 expression is up-regulated in the TRAMP model and it correlates with the malignant progression of mouse prostate adenocarcinoma in this transgenic model. This further strengthens the hypothesis that MUC18 has an important role in increasing the metastatic potential of prostate cancer cells.

Identify lymphatic metastasis-associated genes in mouse hepatocarcinoma cell lines using gene chip

AIM: In order to obtain lymphogenous metastasis-associated genes, we compared the transcriptional profiles of mouse hepatocarcinoma cell lines Hca-F with highly lymphatic metastasis potential and Hca-P with low lymphatic metastasis potential.

METHODS: Total RNA was isolated from Hca-F and Hca-P cells and synthesized into double-stranded cDNA. In vitro transcription double-stranded cDNA was labeled with biotin (i.e., biotin-labeled cRNA, used as the probe). The cRNA probes hybridized with Affymetrix GeneChip^® MOE430A (containing 22690 transcripts, including 14500 known mouse genes and 4371 ESTs) respectively and the signals were scanned by the GeneArray Scanner. The results were then analyzed by bioinformatics.

RESULTS: Out of the 14500 known genes investigated, 110 (0.8%) were up regulated at least 2³ fold. Among the total 4371 ESTs, 17 ESTs (0.4%) (data were not presented) were up regulated at least 2³ fold. According to the Gene Ontology and TreeView analysis, the 110 genes were further classified into two groups: differential biological process profile and molecular function profile.

CONCLUSION: Using high-throughput gene chip method, a large number of genes and their cellular functions about angiogenesis, cell adhesion, signal transduction, cell motility, transport, microtubule-based process, cytoskeleton organization and biogenesis, cell cycle, transcription, chaperone activity, motor activity, protein kinase activity, receptor binding and protein binding might be involved in the process of lymphatic metastasis and deserve to be used as potential candidates for further investigation. Cyclin D1, Fosl1, Hsp47, EGFR and AR, and Cav-1 are selected as the possible candidate genes of the metastatic phenotype, which need to be validated in later experiments. ESTs (data were not presented) might indicate novel genes associated with lymphatic metastasis. Validating the function of these genes is helpful to identify the key or candidate gene/pathway responsible for lymphatic metastasis, which might be used as the diagnostic markers and the therapeutic targets for lymphatic metastasis.

Prostate cancer invasion is influenced more by expression of a CD44 isoform including variant 9 than by Muc18

The standard form of cell adhesion glycoprotein CD44 is a metastasis suppressor in prostate cancer. However, we previously showed by RT-PCR and Western blotting that cancer overexpresses unique CD44 variant v7-v10 isoforms. Muc18 is another cell adhesion marker reportedly overexpressed by prostate cancer. Matched frozen section-confirmed tumor and benign tissues were harvested from 10 prostatectomy specimens and tumor was microdissected from two lymph node metastases. Tissues were homogenized for RNA preparations, and RT-PCR was performed for the CD44v7-v10 sequence. In cultured prostate cancer cells, we caused RNA interference against CD44v9 and/or Muc18. We used PC3M cells and a derivative cell line called G(s)alpha, that constitutively expresses this G-protein and is more invasive. Lipofection was performed for a green fluorescent protein plasmid and for two 22-mer DNA fragments, cloned into a plasmid expression vector to generate hairpin, interfering dsRNA. Assays for invasion into Matrigel, a basement membrane matrix, were performed in 4-5 experiments. RT-PCR demonstrated expression of a 608 bp band representing CD44v7-v10 or a 638 bp band of CD44v6-v10 in prostate cancer tissues and metastases but not benign tissue. Cultured G(s)alpha cells overexpressed CD44v9 by comparison with PC3M cells. At 90 h after 6-hour lipofection, protein silencing was evident by Western blots. Silencing the CD44v9 expression reduced invasiveness into Matrigel to 21.6+/-7.0% in PC3M cells (P<0.001) and 31.2+/-18.3% in G(s)alpha cells (P=0.001), compared to cells exposed to transfection vehicle alone. Silencing Muc18 expression reduced invasiveness to 76.9+/-13.5% of the control value in PC3M cells (P<0.05) and 84.8+/-29.9% in G(s)alpha cells (P=0.18). Prostate cancer invasion is facilitated more by its overexpression of CD44 variant 9 than by Muc18. Its relative overexpression by G(s)alpha cells is a novel finding, suggesting a link between signal transduction and cell adhesion marker expression.

Ectopical expression of human MUC18 increases metastasis of human prostate cancer cells

MUC18, a cell adhesion molecule (CAM), has been reported to be a diagnostic marker for the early detection of the metastatic potential of prostate cancers as well as implicated to be an important determinant for mediating the tumorigenesis and metastasis of prostate cancer. To test the hypothesis, we further investigated the possible role of MUC18 in the malignant progression of human prostate cancer. The human MUC18-minus, non-metastatic human prostate cancer LNCaP cells were transfected with the human cytomegalovirus immediate-early gene (HCMV-IE) promoter-driven human MUC18 (huMUC18) cDNA. The G418-resistant (G418R)-LNCaP clones that expressed a high level of huMUC18 were selected and used for testing the effect of huMUC18 expression on the in vitro growth, motility, and invasiveness as well as on the in vivo metastasis (via orthotopical injection) in a xenograft nude mouse model. HuMUC18 expression increased by four- to fivefold of in vitro motility and invasiveness of LNCaP cells. Anti-huMUC18 antibody significantly inhibited the in vitro motility and invasiveness of huMUC18-expressing LNCaP clones, but not the control clones. We suggest that huMUC18 expression is responsible for increasing these behaviors of LNCaP cells. HuMUC18 expression also directly increased the in vivo metastatic abilities of the LNCaP cells from the prostate gland to multiple distant organs. Western blot and immunohistochemistry analyses showed that the prostatic tumors as well as metastatic lesions expressed high levels of MUC18, indicating that they originated from the injected huMUC18-expressing LNCaP cells. We therefore conclude that HuMUC18 is an important determinant in increasing metastasis of human prostate cancer LNCaP cells to distant organs in a nude mouse model.

Characterization of Gicerin/MUC18/CD146 in the rat nervous system

Gicerin is a cell adhesion molecule of an immunoglobulin (Ig) superfamily isolated from a chicken. It shows homophilic and heterophilic binding activities and has two isoforms. s-Gicerin which has small cytoplasmic domain and the same extracellular domain as l-gicerin shows stronger cell adhesion activity. In the chick nervous system, gicerin expression is only observed in the developmental stage when neurons extend neurites and migrate. In other tissues, gicerin participates in the tissue regeneration or oncogenesis. In this report, we identified two isoforms of rat gicerin corresponding to chicken and we concluded that gicerin is a homologue of human CD146/MUC18/MCAM. Next we generated antibody to characterize a rat gicerin in the nervous system. Gicerin is expressed in the hippocampal cells, Purkinje cells, and sensory neurons of a spinal chord of an adult rat, while expressed most abundantly in the lung. In addition to this, its expression in the hippocampus was increased by electroconvulsive shock, suggesting some role in the mature nervous system. And we also showed neurite promotion activity of gicerin from hippocampal neurons.

Use of real-time polymerase chain reaction to identify cell- and tissue-type-selective peptides by phage display

Phage display approaches are used increasingly in efforts to identify cancer-specific binding peptides and antibodies. Phage-derived reagents are likely to have broad applications in diagnostic and research pathology. A critical element in the identification of cell or tissue-type-specific phage is the ability to reproducibly quantify bound or eluted phage at various stages of panning and screening procedures. Traditional biological assays of phage numbers such as plaque counting are commonly applied but are time-consuming, labor-intensive, and poorly reproducible. Moreover, enzyme immunoassays only support a subset of target types. Here, we report on the use of real-time polymerase chain reaction (PCR) (M13qPCR) in developing methods for identification of cell- and tissue-type-specific binding peptides. With M13qPCR, we demonstrate a >/=5 log(10) dynamic linear range with high reproducibility and significantly lower coefficients of variation (10 to 20%) than conventional methodology. Using M13qPCR in phage-panning experiments on live leukemia and prostate cancer cells, cancer-binding phage were identified. Similar results were obtained with conventional methodology such as flow cytometry. These results were extended to specific application of M13qPCR in panning phage libraries on tissue sections of prostate and breast cancer. With the PCR-based method, direct quantification of phage bound to tissue sections correlated well with staining intensity and yielded phage that bound to neoplastic and nonneoplastic epithelium. Thus, real-time PCR-based methodology significantly improves a number of aspects of conventional phage-panning protocols. Furthermore, identification of phage that bind specifically to diseased or cancerous tissue sections will likely be facilitated by this PCR-based approach.

Mel-CAM (CD146) expression in parotid mucoepidermoid carcinoma

Mel-CAM (CD146) is a cell-cell adhesion protein found in normal and tumoral tissues. The aim of this study was to analyse Mel-CAM expression in mucoepidermoid carcinoma (MEC), and assess its importance in prognosis and its utility in differentiating high-grade MEC from squamous cell carcinoma (SCC). Immunohistochemical expression of Mel-CAM in 41 parotid MEC was correlated with clinical parameters. Ten cases of oral cavity SCC were included for comparison. Mel-CAM expression was found in 92.7% of the MEC but was not expressed by the SCC. Mel-CAM expression was greater in intermediate/high grade tumors, was weaker in patients that presented local recurrence, regional and distant metastasis, but no correlation between Mel-CAM and clinical stage and survival of the patients was found. Decreased Mel-CAM expression can impair cellular contact properties, facilitating growth, cell spreading and metastasis in MEC. Mel-CAM can also be useful in differentiating high grade MEC from SCC.