Norishige Yamada

Expression profiles of MUC1, MUC2, and MUC4 mucins in human neoplasms and their relationship with biological behavior.

Mucins are high molecular weight glycoproteins that play important roles in carcinogenesis or tumor invasion. To clarify the relationship of the expression patterns of mucins in human neoplasms with their biological behavior, we examined the expression profiles of MUC1, MUC2, and MUC4 mucins in various human neoplasms using immunohistochemistry and in situ hybridization, and compared them with clinicopathologic factors including outcome of the patients. MUC1 or MUC4 expression is related with the aggressive behavior of human neoplasms and a poor outcome of the patients. In contrast, MUC2 expression tends to be related with the indolent behavior of human neoplasms and a favorable outcome of the patients, although indolent pancreatobiliary neoplasms sometimes show invasive growth with MUC1 expression in the invasive areas. The expression of MUC2 mucin in indolent pancreatobiliary neoplasms coincided with expression of MUC2 mRNA. Our recent studies to clarify the MUC2 gene regulation mechanism disclosed that DNA methylation and histone modification in the 5′ flanking region of the MUC2 promoter may play an important role. Further studies of the epigenetics also in MUC1 and MUC4 gene expression may be needed to understand the relationship between the expression of mucins in human neoplasms with their biological behavior.

Significance of mucin expression in pancreatobiliary neoplasms

Mucins are high molecular weight glycoproteins that play important roles in carcinogenesis and tumor invasion. We have described, for the first time, that pancreatic ductal adenocarcinomas (PDACs) with an aggressive behavior and a poor outcome expressed MUC1 (pan-epithelial membrane-associated mucin) but did not express MUC2 (intestinal-type secreted mucin), whereas intraductal papillary mucinous neoplasms (IPMNs) with indolent behavior and a favorable outcome did not express MUC1 but did express MUC2. These expression profiles of MUC1 and MUC2 related to the prognoses of the patients were also observed in biliary neoplasms such as intrahepatic cholangiocarcinoma (ICC)-mass-forming type (MF), mucin-producing bile duct tumor (MPBT), and extrahepatic bile duct carcinoma (EHBDC). We also found recently that high expression of MUC4 (tracheobronchial membrane-associated mucin) in PDACs, ICCs-MF, and EHBDCs was a new independent poor prognostic factor, although MUC4 was not expressed in normal pancreatobiliary tissue. High de novo expression of MUC5AC (gastric-type secreted mucin) was observed in many types of pancreatobiliary neoplasms, including all grades of pancreatic intraepithelial neoplasia (PanIN) and biliary intraepithelial neoplasia (BilIN), and all types of IPMNs and MPBTs, as well as PDACs and ICCs-MF, although MUC5AC was not expressed in normal pancreatobiliary tissue. The combined status of MUC1, MUC2, MUC4, and MUC5AC expression may be useful for the early detection of pancreatobiliary neoplasms and evaluation of their malignancy. In regard to the mechanism of mucin expression, we have recently reported that MUC1, MUC2, MUC4, and MUC5AC gene expression is regulated by epigenetics (DNA methylation and histone H3 lysine 9 modification) in cancer cell lines, including PDAC cells. Translational research of mucin gene expression mechanisms, including epigenetics, in pancreatobiliary neoplasms may give us new tools for the early and accurate detection of these neoplasms.

MUC2 expression is regulated by histone H3 modification and DNA methylation in pancreatic cancer

Mucins are highly glycosylated proteins that play important roles in carcinogenesis. In pancreatic neoplasia, MUC2 mucin has been demonstrated as a tumor suppressor and we have reported that MUC2 is a favorable prognostic factor. Regulation of MUC2 gene expression is known to be controlled by DNA methylation, but the role of histone modification for MUC2 gene expression has yet to be clarified. Herein, we provide the first report that the histone H3 modification of the MUC2 promoter region regulates MUC2 gene expression. To investigate the histone modification and DNA methylation of the promoter region of the MUC2 gene, we treated 2 human pancreatic cancer cell lines, PANC1 (MUC2‐negative) and BxPC3 (MUC2‐positive) with the DNA methyltransferase inhibitor 5‐azacytidine (5‐aza), the histone deacetylase inhibitor trichostatin A (TSA), and a combination of these agents. The DNA methylation level of PANC1 cells was decreased by all 3 treatments, whereas histone H3‐K4/K9 methylation and H3‐K9/K27 acetylation in PANC1 cells was changed to the level in BxPC3 cells by treatment with TSA alone and with the 5‐aza/TSA combination. The expression level of MUC2 mRNA in PANC1 cells exhibited a definite increase when treated with TSA and 5‐aza/TSA, whereas 5‐aza alone induced only a slight increase. Our results suggest that histone H3 modification in the 5′ flanking region play an important role in MUC2 gene expression, possibly affecting DNA methylation. An understanding of these intimately correlated epigenetic changes may be of importance for predicting the outcome of patients with pancreatic neoplasms.

Mucins in human neoplasms: clinical pathology, gene expression and diagnostic application.

Mucins are high molecular weight glycoproteins that play important roles in carcinogenesis and tumor invasion. Our immunohistochemical studies demonstrated that MUC1 or MUC4 expression is related to the aggressive behavior and poor outcome of human neoplasms. MUC2 is expressed in indolent pancreatobiliary neoplasms, but these tumors sometimes show invasive growth with MUC1 expression in invasive areas. MUC5AC shows de novo high expression in many types of precancerous lesions of pancreatobiliary cancers and is an effective marker for early detection of the neoplasms. The combination of MUC1, MUC2, MUC4 and MUC5AC expression may be useful for early detection and evaluation of the potential for malignancy of pancreatobiliary neoplasms. Regarding the mechanism of mucin expression, we have recently reported that expression of the mucin genes is regulated epigenetically in cancer cell lines, using quantitative MassARRAY analysis, methylation‐specific polymerase chain reaction analysis and chromatin immunoprecipitation analysis, with confirmation by the treatment with 5‐aza‐2′‐deoxycytidine and trichostatin A. We have also developed a monoclonal antibody against the MUC1 cytoplasmic tail domain, which has many biological roles. Based on all of the above findings, we suggest that translational research into mucin gene expression mechanisms, including epigenetics, may provide new tools for early and accurate detection of human neoplasms.

Precursor Lesions of Pancreatic Cancer

This review article describes morphological aspects, gene abnormalities, and mucin expression profiles in precursor lesions such as pancreatic intraepithelial neoplasia (PanIN), intraductal papillary mucinous neoplasm (IPMN), and mucinous cystic neoplasm (MCN) of the pancreas, as well as their relation to pancreatic ductal adenocarcinoma (PDAC). The gene abnormalities in precursors of PDAC are summarized as follows: (1) KRAS mutation and p16/CDKN2A inactivation are early events whose frequencies increase with the dysplasia grade in both PanIN and IPMN; (2) TP53 mutation and SMAD4/DPC4 inactivation are late events observed in PanIN3 or carcinomatous change of IPMN in both PanIN and IPMN, although the frequency of the TP53 mutation is lower in IPMN than in PDAC; and (3) also in MCN, KRAS mutation is an early event whose frequency increases with the dysplasia grade, whereas TP53 mutation and SMAD4/DPC4 inactivation are evident only in the carcinoma. The mucin expression profiles in precursors of PDAC are summarized as follows: (1) MUC1 expression increases with the PanIN grade, and is high in PDAC; (2) the expression pattern of MUC2 differs markedly between the major subtypes of IPMN with different malignancy potentials (i.e., IPMN-intestinal type with MUC2+ expression and IPMN-gastric type with MUC2- expression); (3) MUC2 is not expressed in any grade of PanINs, which is useful for differentiating PanIN from intestinal-type IPMN; (4) de novo expression of MUC4, which appears to increase with the dysplasia grade; and (5) high de novo expression of MUC5AC in all grades of PanINs, all types of IPMN, MCN, and PDAC.

Promoter CpG methylation in cancer cells contributes to the regulation of MUC4

Mucin 4 (MUC4) is a high molecular weight transmembrane mucin that is overexpressed in many carcinomas and is a risk factor associated with a poor prognosis. In this study, we show that the DNA methylation pattern is intimately correlated with MUC4 expression in breast, lung, pancreas and colon cancer cell lines. We mapped the DNA methylation status of 94 CpG sites from −3622 to +29 using MassARRAY analysis that utilises base-specific cleavage of nucleic acids. MUC4-negative cancer cell lines and those with low MUC4 expression (eg, A427) were highly methylated near the transcriptional start site, whereas MUC4-positive cell lines (eg, NCI-H292) had low methylation levels. Moreover, 5-aza-2′-deoxycytidine and trichostatin A treatment of MUC4-negative cells or those with low MUC4 expression caused elevation of MUC4 mRNA. Our results suggest that DNA methylation in the 5′ flanking region play an important role in MUC4 gene expression in carcinomas of various organs. An understanding of epigenetic changes in MUC4 may contribute to the diagnosis of carcinogenic risk and prediction of outcome in patients with cancer.

Pathobiological implications of MUC16/CA125 expression in intrahepatic cholangiocarcinoma-mass forming type.

Objectives: MUC16 carries the peptide epitope CA125, which is well known as a marker of ovarian cancer. High serum levels of MUC16 (CA125) have been reported not only in patients with ovarian cancer but also in patients with liver diseases. We evaluated the expression of MUC16 in intrahepatic cholangiocarcinoma-mass forming type (ICC-MF) tissues. Methods: We examined the expression of MUC16 by immunohistochemical analyses using the monoclonal antibody M11 in ICC-MF tissues from 63 patients. To compare the prevalence of each mucin expression by clinicopathological features, appropriate statistical analysis was performed. Results: MUC16 was detected in 48% of samples (30/63). After adjusting for the effects of other prognostic factors, multivariate survival analysis revealed that MUC16 expression is a significant independent factor of poor prognosis (p = 0.005). Conclusion: The current results indicate that MUC16 expression is a prognostic factor of poor survival in ICC-MF.

Aberrant DNA methylation of tumor-related genes in oral rinse: a noninvasive method for detection of oral squamous cell carcinoma.

The early detection of oral squamous cell carcinoma (OSCC) is important, and a screening test with high sensitivity and specificity is urgently needed. Therefore, in this study, the authors investigated the methylation status of tumor‐related genes with the objective of establishing a noninvasive method for the detection of OSCC.

MUC4: a novel prognostic factor of oral squamous cell carcinoma.

MUC4 mucin is now known to be expressed in various normal and cancer tissues. We have previously reported that MUC4 expression is a novel prognostic factor in several malignant tumors; however, it has not been investigated in oral squamous cell carcinoma (OSCC). The aim of our study is to evaluate the prognostic significance of MUC4 expression in OSCC. We examined the expression profile of MUC4 in OSCC tissues from 150 patients using immunohistochemistry. Its prognostic significance in OSCC was statistically analyzed. MUC4 was expressed in 61 of the 150 patients with OSCC. MUC4 expression was significantly correlated with higher T classification (p = 0.0004), positive nodal metastasis (p = 0.049), advanced tumor stage (p = 0.002), diffuse invasion of cancer cells (p = 0.004) and patients death (p = 0.004) in OSCC. Multivariate analysis showed that MUC4 expression (p = 0.011), tumor location (p = 0.032) and diffuse invasion (p = 0.009) were statistically significant risk factors. Backward stepwise multivariate analysis demonstrated MUC4 expression (p = 0.0015) and diffuse invasion (p = 0.018) to be statistically significant independent risk factors of poor survival in OSCC. The disease‐free and overall survival of patients with MUC4 expression was significantly worse than those without MUC4 expression (p < 0.0001 and p = 0.0001). In addition, the MUC4 expression was a significant risk factor for local recurrence and subsequent nodal metastasis in OSCC (p = 0.017 and p = 0.0001). We first report MUC4 overexpression is an independent factor for poor prognosis of patients with OSCC; therefore, patients with OSCC showing positive MUC4 expression should be followed up carefully.

Epigenetic regulation of mucin genes in human cancers.

Mucins are high molecular weight glycoproteins that play important roles in diagnostic and prognostic prediction and in carcinogenesis and tumor invasion. Regulation of expression of mucin genes has been studied extensively, and signaling pathways, transcriptional regulators, and epigenetic modification in promoter regions have been described. Detection of the epigenetic status of cancer-related mucin genes is important for early diagnosis of cancer and for monitoring of tumor behavior and response to targeted therapy. Effects of micro-RNAs on mucin gene expression have also started to emerge. In this review, we discuss the current views on epigenetic mechanisms of regulation of mucin genes (MUC1, MUC2, MUC3A, MUC4, MUC5AC, MUC5B, MUC6, MUC16, and MUC17) and the possible clinical applications of this epigenetic information.