Preparation Of Monoclonal Antibody To A Novel Hepatocellular Carcinoma Marker MXR7 And Clinical Application

Hepatocellular carcinoma (HCC) is one of the most severe sequelae of liver disorders. In spite of recent therapeutic advances, this malignancy continues to be a significant cause of cancer related morbidity and mortality in Asian and Western countries. Surgical resection remains the treatment of choice for these tumours. Advances in radiological imaging over the past two decades have focused attention on early detection of hepatic nodular lesions. The mainstay for the diagnosis for HCC includes serological tumor markers, such as alpha-fetoprotein, in addition to imaging modalities. First, it is necessary to identify the patients at high risk for developing HCC, such as those with chronic hepatitis or liver cirrhosis, and in the follow-up conduct regular check-ups for serological tumor markers. Those testing positive for any marker are at the highest risk for developing HCC, even when imaging fails to disclose any space-occupying lesions. Following high-risk patients for serological tumor markers, in concert with imaging, makes accurate evaluation of the efficacy of therapies for HCC possible. Since serological tumor markers can signal the development of HCC earlier than any other laboratory tests, they offer excellent means of identifying relapsing HCC. Equally important in the management of patients with HCC are biological indicators for malignancy, the selection of therapeutic interventions and the prediction of the outcome.MXR7 was cloned from the mitoxantrone-resistant human gastric carcinoma cell line with the differential display method. It is a full-length cDNA encoding a 580-amino acid polypeptide. MXR7 mRNA was expressed in high levels in the placenta, fetal liver, lung, and kidney, but it was undetectable in adult liver and was expressed in very low levels in adult lung and kidney. MXR7 belongs to the glypican family of GPI anchored heparan sulphate proteoglycans (HSPGs) which plays an important role in cellular growth, cell differentiation, and cell migration. The fact thatmembrane-bound HSPGs regulate the activity of heparin-binding growth factor has been known for many years, but only during the last decade has the existence of two major families of membrane-bound HSPGs been established[14-21]. One of these families, the glypicans, plays a critical role in developmental morphogenesis. The interest in the study of glypicans has increased in the last few years as a result of the discovery that MXR7 is mutated in an overgrowth and dysmorphic syndrome[22,23]. The finding that MXR7 regulates body size was particularly surprising and suggested that this glypican may interact with signaling pathways that have not been traditionally associated with membrane-bound HSPGs. Given the ability of glypicans to regulate the activity of growth and survival factors, recent reports associating changes in glypican expression with tumor progression were not surprising. One of the first studies that established a connection between glypicans and cancer showed that MXR7 expression is downregulated in a significant proportion of ovarian cancer cell lines. In all cases where MXR7 expression was lost, the promoter region of the MXR7 gene was hypermethylated, and no mutations were found in the coding region. MXR7 expression was restored by treatment with a demethylating agent[24]. Another recent study associating MXR7 with cancer built upon differential mRNA display data in which normal rat mesothelial cells were compared with mesothelioma cell lines. Murthy et al. found that MXR7 was consistently downregulated in the tumor cell lines. Moreover, a similar downregulation was found in primary rat mesotheliomas and in cell lines derived from human mesotheliomas. As with ovarian cancer, no mutations in the MXR7 coding sequence were found, but most of the cell lines displayed aberrant methylation in the MXR7 promoter region[25]. In addition, the study reported that, whereas MXR7 is not expressed in human normal adult liver, its expression is upregulated in most hepatocarcinomas[11-13]. Since it is highly expressed in emb...