Xiang-Min Yang

A randomized controlled trial of Licartin for preventing hepatoma recurrence after liver transplantation.

Orthotopic liver transplantation (OLT) is the only curative therapy of HCC with underlying cirrhosis, but due to HCC metastasis and recurrence, its benefit is limited to a small population who meet the strict selection criteria. We previously reported that Licartin ([131I]mAb HAb18G/CD147) was safe and effective in treating HCC patients, and its antigen, HAb18G/CD147, was closely related to HCC invasion and metastasis. Here, we reported a randomized controlled trial to assess the post‐OLT antirecurrence efficacy of Licartin in advanced HCC patients. We randomized 60 post‐OLT patients with HCC, who were at tumor stage 3/4 and outside the Milan criteria before OLT, into 2 groups. Three weeks after OLT, the treatment group received 15.4 MBq/kg of Licartin, while the control group received placebo intravenously for 3 times with an interval of 28 days. At 1‐year follow‐up, the recurrence rate significantly decreased by 30.4% (P = 0.0174) and the survival rate increased by 20.6% (P = 0.0289) in the treatment group, compared with those in the control group. For the control group versus the treatment group, the hazard ratio for recurrence was 3.60 (95% confidence interval [CI], 1.50‐8.60) and that for death was 3.87 (95% CI, 1.23–12.21). Licartin treatment also resulted in an earlier decreased AFP level and a longer time of normal AFP level than placebo (P = 0.0016). No Licartin‐related toxic effects were observed. Conclusion: Licartin is a promising drug for preventing post‐OLT tumor recurrence in advanced HCC patients excluded by the currently strict criteria for OLT. HAb18G/CD147 can be a good drug target. (HEPATOLOGY 2007;45:269–276.)

HAb18G/CD147 Functions in Invasion and Metastasis of Hepatocellular Carcinoma

CD147 molecule is reported to be correlated with the malignancy of some cancers; however, it remains unclear whether it is involved in the progression of hepatocellular carcinoma (HCC). Here, we investigated the function of HAb18G/CD147, a member of CD147 family, and its antibodies, HAb18 and LICARTIN, in HCC invasion and metastasis. We observed that HAb18G/CD147 gene silence in HCC cells significantly decreased the secretion of matrix metalloproteinase (MMP) and the invasive potential of HCC cells (P < 0.001). MMP silence in HCC cells also significantly suppressed the invasion of the cells when cocultured with fibroblasts; however, its inhibitory effect was significantly weaker than that of both HAb18G/CD147 silence in HCC cells and that of MMP silence in fibroblasts (P < 0.001). Blocking theHAb18G/CD147 molecule on HCC cells with HAb18 monoclonal antibody resulted in a similar suppressive effect on MMP secretion and cell invasion, but with no significant effects on the cell growth. 131I-labeled HAb18 F(ab′)2 (LICARTIN), however, significantly inhibited the in vitro growth of HCC cells (P < 0.001). In an orthotopic model of HCC in nude mice, HAb18 and LICARTIN treatment effectively reduced the tumor growth and metastasis as well as the expression of three major factors in the HCC microenviroment (MMPs, vascular endothelial growth factor, and fibroblast surface protein) in the paracancer tissues. Overall, these results suggest that HAb18G/CD147 plays an important role in HCC invasion and metastasis mainly via modulating fibroblasts, as well as HCC cells themselves to disrupt the HCC microenviroment. LICARTIN can be used as a drug targeting to HAb18G/CD147 in antimetastasis and recurrence therapy of HCC. (Mol Cancer Res 2007;5(6):605–14)

Crystal structure of HAb18g/CD147 - Implications for immunoglobulin superfamily homophilic adhesion

CD147, a member of the immunoglobulin superfamily (IgSF), plays fundamental roles in intercellular interactions in numerous pathological and physiological processes. Importantly, our previous studies have demonstrated that HAb18G/CD147 is a novel hepatocellular carcinoma (HCC)-associated antigen, and HAb18G/CD147 stimulates adjacent fibroblasts and HCC cells to produce elevated levels of several matrix metalloproteinases, facilitating invasion and metastasis of HCC cells. In addition, HAb18G/CD147 has also been shown to be a novel universal cancer biomarker for diagnosis and prognostic assessment of a wide range of cancers. However, the structural basis underlying the multifunctional character of CD147 remains unresolved. We report here the crystal structure of the extracellular portion of HAb18G/CD147 at 2.8Å resolution. The structure comprises an N-terminal IgC2 domain and a C-terminal IgI domain, which are connected by a 5-residue flexible linker. This unique C2-I domain organization is distinct from those of other IgSF members. Four homophilic dimers exist in the crystal and adopt C2-C2 and C2-I dimerization rather than V-V dimerization commonly found in other IgSF members. This type of homophilic association thus presents a novel model for homophilic interaction between C2 domains of IgSF members. Moreover, the crystal structure of HAb18G/CD147 provides a good structural explanation for the established multifunction of CD147 mediated by homo/hetero-oligomerizations and should represent a general architecture of other CD147 family members.

Overexpression of HAb18G/CD147 promotes invasion and metastasis via α3β1 integrin mediated FAK-paxillin and FAK-PI3K-Ca2+ pathways

Abstract.Mechanism of HAb18G/CD147 underlying the metastasis process of human hepatoma cells has not been determined. In the present study, we found that integrin α3β1 colocalizes with HAb18G/CD147 in human 7721 hepatoma cells. The enhancing effect of HAb18G/CD147 on adhesion, invasion capacities and matrix metalloproteinases (MMPs) secretion was decreased by integrin α3β1 antibodies (p<0.01). The expressions of integrin downstream molecules including focal adhesion kinase (FAK), phospho-FAK (p-FAK), paxillin, and phospho-paxillin (p-paxillin) were increased in human hepatoma cells overexpressing HAb18G/CD147. Deletion of HAb18G/CD147 reduces the quantity of focal adhesions and rearranges cytoskeleton. Wortmannin and LY294002, specific phosphatidylinositol kinase (PI3K) inhibitors, reversed the effect of HAb18G/CD147 on the regulation of intracellular Ca2+ mobilization, significantly reducing cell adhesion, invasion and MMPs secretion potential (p<0.01). Together, these results suggest that HAb18G/CD147 enhances the invasion and metastatic potentials of human hepatoma cells via integrin α3β1-mediated FAK-paxillin and FAKPI3K-Ca2+ signal pathways.

Characterization of Basigin Isoforms and the Inhibitory Function of Basigin-3 in Human Hepatocellular Carcinoma Proliferation and Invasion

ABSTRACT Basigin, which has four isoforms, plays an important role in invasion of hepatocellular carcinoma (HCC). Detailed transcriptional regulation and functions of the basigin isoforms have not been reported except in the case of the predominant isoform basigin-2, which act as inducer of matrix metalloproteinases (MMPs). Here we determined that basigin-2, basigin-3, and basigin-4 were the most abundant transcript variants in human cell lines. GeneRacer PCR and luciferase reporter assays showed that basigin-3 and basigin-4 were initiated from an alternative promoter. Basigin-3 and basigin-4 were widely expressed in various normal human tissues at the mRNA level and were upregulated in HCC tissues compared to in normal tissues. Western blotting and confocal imaging showed that glycosylated basigin-3 and basigin-4 were expressed and localized to the plasma membrane. However, in cultured cell lines, only native basigin-3, and not basigin-4, was detected at protein level. Overexpression of basigin-3 inhibited HCC cell proliferation, MMP induction, and cell invasion in vitro and in vivo. Bimolecular fluorescence complementation assays and nuclear magnetic resonance (NMR) analysis indicated that basigin-3 interacted with basigin-2 to form hetero-oligomers. In conclusion, we systematically investigated the alternative splicing of basigin and found that basigin-3 could inhibit HCC proliferation and invasion, probably through interaction with basigin-2 as an endogenous inhibitor via hetero-oligomerization.

Epitope Mapping of Series of Monoclonal Antibodies Against the Hepatocellular Carcinoma-associated Antigen HAb18G/CD147

The hepatocellular carcinoma‐associated antigen HAb18G/CD147, a member of CD147 family, could promote tumour invasion and metastasis via inducing the secretion of matrix metalloproteinases (MMP). Anti‐CD147 monoclonal antibodies (MoAb) have exhibited obvious inhibitory effect on MMP induction. However, none of the epitopes of these MoAb has been reported. We previously prepared five MoAb against HAb18G/CD147, named HAb18, 3B3, 1B3, 5A5 and 4D2. To map the epitopes of these MoAb, a series of truncated fragments of extracellular region of HAb18G/CD147 was expressed in Escherichia coli and the MoAb‐binding affinity to these fragments was examined with an enzyme‐linked immunosorbent assay and Western blot. The residues 39LTCSLNDSATEV50, 36KILLTCS42 and 22AAGTVFTTVEDL33 were determined to be the epitopes of HAb18, 3B3 and 1B3, respectively, which were further proved by a dot‐blot analysis with synthesized peptides and bioinformatics epitope prediction. The binding regions of MoAb 5A5 and 4D2 were located at residues E120–R203. Then we constructed and expressed full‐length HAb18G/CD147 and truncated HAb18G/CD147 without residues A22–V50 in COS‐7 cells. Gelatin zymography and Boyden chamber assay showed that the COS‐7 cells expressing truncated HAb18G/CD147 failed to induce MMP production and enhance the cells’ invasive potential, compared with the cells expressing full‐length HAb18G/CD147. Taken together with the obviously inhibitory effects of HAb18 on the function of full‐length HAb18G/CD147, these findings suggest that residues 22AAGTVFTTVEDLGSKILLTCSLNDSATEV50 may play a critical role in the functions of HAb18G/CD147 on MMP secretion and tumour invasion. These key residues can be used as potential drug target in cancer therapy.

Involvement of HAb18G/CD147 in T cell activation and immunological synapse formation

HAb18G/CD147, a glycoprotein of the immunoglobulin super‐family (IgSF), is a T cell activation‐associated molecule. In this report, we demonstrated that HAb18G/CD147 expression on both activated CD4+ and CD8+ T cells was up‐regulated. In vitro cross‐linking of T cells with an anti‐HAb18G/CD147 monoclonal antibody (mAb) 5A12 inhibited T cells proliferation upon T cell receptor stimulation. Such co‐stimulation inhibited T cell proliferation by down‐regulating the expression of CD25 and interleukin‐2 (IL‐2), decreased production of IL‐4 but not interferon‐γ. Laser confocal imaging analysis indicated that HAb18G/CD147 was recruited to the immunological synapse (IS) during T cell activation; triggering HAb18G/CD147 on activated T cells by anti‐HAb18G/CD147 mAb 5A12 strongly dispersed the formation of the IS. Further functional studies showed that the ligation of HAb18G/CD147 with mAb 5A12 decreased the tyrosine phosphorylation and intracellular calcium mobilization levels of T cells. Through docking antibody–antigen interactions, we demonstrated that the function of mAb 5A12 is tightly dependent on its specificity of binding to N‐terminal domain I, which plays pivotal role in the oligomerization of HAb18G/CD147. Taken together, we provide evidence that HAb18G/CD147 could act as a co‐stimulatory receptor to negatively regulate T cell activation and is functionally linked to the formation of the IS.

A novel antibody fragment targeting HAb18G/CD147 with cytotoxicity and decreased immunogenicity

[131 I]Metuximab injection (Licartin) was an efficient therapeutic anti-hepatocellular carcinoma (HCC) radioimmunological agent generated by labeling 131 I with the murine monoclonal antibody fragment HAb18-F(ab’)2 but human anti-mouse antibody (HAMA) response in some patients after administration limited its clinical use. To reduce the immunogenicity of murine antibody, we attempted to humanize HAb18 by variable domain resurfacing based on the three-dimensional structure of Fv fragment. Considering the surface accessibility of non-human like framework residues and the potential to form a molecular hydrogen bond within the context of the homology modeled Fv of HAb18, three residues in a single chain fragment of antibody variable region of HAb18 (HAb18scFv) were replaced by their human counterparts. We fabricated a humanized version of HAb18scFv, HAb18-huscFv, to the human IgG1 Fc fragment to form (HAb18-huscFv)2-Fc. The reactivity of (HAb18-huscFv)2-Fc to the serum of patients with HAMA response was decreased while its specificity and similar binding activity (KD = 1.5 × 10-9 M) were retained compared with its parental antibody. In addition, this antibody is an efficient mediator of antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). These results suggest (HAb18-huscFv)2-Fc could be a more efficient antibody fragment with less immunogenicity and additional cytotoxicity function.

Full-length soluble CD147 promotes MMP-2 expression and is a potential serological marker in detection of hepatocellular carcinoma

BackgroundAs a surface glycoprotein, CD147 is capable of stimulating the production of matrix metalloproteinases (MMPs) from neighboring fibroblasts. The aim of the present study is to explore the role of soluble CD147 on MMPs secretion from hepatocellular carcinoma (HCC) cells, and to investigate the diagnostic value of serum soluble CD147 in the HCC detection.MethodsWe identified the form of soluble CD147 in cell culture supernate of HCC cells and serum of patients with HCC, and explored the role of soluble CD147 on MMPs secretion. Serum CD147 levels were detected by the enzyme-linked immunosorbent assay, and the value of soluble CD147 as a marker in HCC detection was analyzed.ResultsFull length soluble CD147 was presented in the culture medium of HCC cells and serum of patients with HCC. The extracellular domain of soluble CD147 promoted the expression of CD147 and MMP-2 from HCC cells. Knockdown of CD147 markedly diminished the up-regulation of CD147 and MMP-2 which induced by soluble CD147. Soluble CD147 activated ERK, FAK, and PI3K/Akt pathways, leading to the up-regulation of MMP-2. The level of soluble CD147 in serum of patients with HCC was significantly elevated compared with healthy individuals (P < 0.001). Soluble CD147 levels were found to be associated with HCC tumor size (P = 0.007) and Child-Pugh grade (P = 0.007). Moreover, soluble CD147 showed a better performance in distinguishing HCC compared with alpha-fetoprotein.ConclusionsThe extracellular domain of soluble CD147 enhances the secretion of MMP-2 from HCC cells, requiring the cooperation of membrane CD147 and activation of ERK, FAK, and PI3K/Akt signaling. The measurement of soluble CD147 may offer a useful approach in diagnosis of HCC.

Basigin-mediated redistribution of CD98 promotes cell spreading and tumorigenicity in hepatocellular carcinoma

BackgroundDysregulated endocytosis of membrane proteins contributes significantly to several hallmarks of cancer. Basigin can enhance cancer progression, but its precise mechanism remains unclear. CD98 promotes cell spreading and tumorigenicity by triggering integrin clustering and enhancing cell adhesion to the extracellular matrix. The endocytosis and recyle of basigin and CD98 might play critical roles in cancer.MethodsThe role of CD98 was confirmed in liver cancer cells by cell spreading in vitro and tumorigenicity by nude mice xenograft tumor assay in vivo; membrane expression of basigin and CD98 in SMMC-7721 was measured by FCAS; pull down and SPR analysis were uses to reveal the direct association between basigin and CD98; DsRed1 tagged CD98 was blocked in the cytoplasm in K7721 (whose basigin was knockn out) and had a well colocalization with ER and Rab5a positive recycling endosomes under co-focal; finally, by FRET imaging and FCAS we observed the internalization of basigin and CD98 was flotillin-1-regulated, and their recycle at early steps was Arf6-mediated.ResultsBasigin and CD98 were highly expressed and co-localized on the human hepatocellular carcinoma (HCC) cell membrane; basigin can directly bind to CD98, mediating CD98 redistribution on the HCC cell membrane and activating the downstream integrin signaling pathway. Internalization of basigin and CD98 was flotillin-1 regulated the and their recycling was mediated by Arf6. This recycling process for basigin and CD98 promotes cell spreading and tumor growth in liver cancer xenografts.ConclusionBasigin, as a redistribution chaperone of CD98, plays a critical role in promoting cell spreading and the progression of hepatocellular carcinoma.