Allelic loss in human intrahepatic cholangiocarcinoma: correlation between chromosome 8p22 and tumor progression

The significance of genetics for cholangiocarcinoma development

Cholangiocarcinoma (CCA) is a rare malignancy of the liver, arising from bile ducts. The incidence is increasing worldwide, but the prognosis has remained dismal and virtually unchanged in the past 30 years. Although several risk factors have been associated with the development of this cancer, none of them are normally identified in most patients. Diagnosis in advanced stages of the disease and limited therapeutic options contribute to poor survival rates. The recent analysis of genetic and epigenetic alterations occurring in CCA has shed new light in the understanding of the molecular mechanisms leading to the malignant transformation of biliary cells. Further studies in this direction may foster new diagnostic, prognostic and therapeutic approaches. This review provides a global overview of recent advances in CCA and describes the most important genetic mutations and epigenetic alterations so far reported in CCA.

Intraductal papillary neoplasms of the bile duct

Intraductal papillary neoplasm of the bile duct (IPNB) is a rare variant of bile duct tumors characterized by papillary growth within the bile duct lumen and is regarded as a biliary counterpart of intraductal papillary mucinous neoplasm of the pancreas. IPNBs display a spectrum of premalignant lesion towards invasive cholangiocarcinoma. The most common radiologic findings for IPNB are bile duct dilatation and intraductal masses. The major treatment of IPNB is surgical resection. Ultrasonography, computed tomography, magnetic resonance image, and cholangiography are usually performed to assess tumor location and extension. Cholangioscopy can confirm the histology and assess the extent of the tumor including superficial spreading along the biliary epithelium. However, pathologic diagnosis by preoperative biopsy cannot always reflect the maximum degree of atypia, because IPNBs are often composed of varying degrees of cytoarchitectural atypia. IPNBs are microscopically classified into four epithelial subtypes, such as pancreatobiliary, intestinal, gastric, and oncocytic types. Most cases of IPNB are IPN with high-grade intraepithelial neoplasia or with an associated invasive carcinoma. The histologic types of invasive lesions are either tubular adenocarcinoma or mucinous carcinoma. Although several authors have investigated molecular genetic changes during the development and progression of IPNB, these are still poorly characterized and controversial.

Aberrant DNA methylation profile in cholangiocarcinoma

Cholangiocarcinoma (CCA) is a notoriously lethal epithelial cancer originating from the biliary system. As radical resection offers a poor success rate and limited effective adjuvant modalities exist in its advanced stage, the disease leads to a fairly poor prognosis. As the incidence of CCA is increasing, although the mortality rate remains stable, and few other definite etiologies have yet to be established, renewing our knowledge of its fundamental carcinogenesis is advisable. The latest advances in molecular carcinogenesis have highlighted the roles of epigenetic perturbations and cancer-related inflammation in CCA. This review focuses on the reciprocal effects between aberrant DNA methylation and inflammatory microenvironment in CCA.

Molecular evidence for the neoplastic potential of hepatic Von-Meyenburg complexes

Von-Meyenburg complexes (VMCs) have been shown to progress to cholangiocarcinoma (CC) in some cases. Histologic examination in such cases reveals a gradual transition of VMCs to intermediate lesions and finally to CC. The goal of this study was to determine if this histologic progression was also accompanied by sequential genetic alterations. Two cases that showed many VMCs with a transition to cholangiocarcinoma through intermediate lesions were analyzed. Multiple VMCs (away from the tumor), intermediate lesions and areas of frank CC were microdissected under stereoscopic guidance and were analyzed for allelic imbalance [loss of heterozygosity (LOH)] using a panel of 20 polymorphic microsatellite markers by polymerase chain reaction/electrophoresis. The 2 cases of CCs revealed LOH at 5 and 7 different genomic loci specific for each patient, respectively. Coexisting VMCs also exhibited LOH ranging from 0 to 3 loci in each case. Intermediate lesions showed LOH at a single locus in case 1, whereas the assay could not be performed in case 2 due to inadequate DNA yield. In case 2, the earliest acquired mutations were present in the VMCs supporting a causal relationship for neoplastic progression. Discordant LOH mutations were also present in the VMCs and the adenomatous lesions providing support that LOH detected at these sites did not passively migrate or reflect contamination. The results of the present study show that the histologic progression observed through these stages is also accompanied by LOH at loci harboring key oncogenes. The findings also support that VMCs are preneoplastic lesions that could progress to CC with time.

Prognostic molecular markers in cholangiocarcinoma: a systematic review

The worldwide incidence of cholangiocarcinoma (CC) is steadily rising, with the incidence in United Kingdom (UK) now exceeding 1000 cases per year. It is an aggressive malignancy typified by unresponsiveness to the existing chemotherapy and radiotherapy regimes in the vast majority of cases. Surgery offers the only hope of a cure, though post-operative disease recurrence is common, with 5-year survival rates of less than 25% following resection. Developments in molecular techniques and improved understanding of the basis of carcinogenesis in CC has led to examination of the role of biomarkers in predicting poor outcome. This systematic review examines published evidence relating to the prognostic significance of these molecular markers in CC. Of the molecular markers which have been investigated to date, p53 mutation, cyclins, proliferation indices, mucins, CA19-9, CRP and aneuploidy appear to hold significant potential as predictors of outcome in CC. These and other biomarkers may themselves represent novel therapeutic targets for CC.

Biological characteristics of cancers in the gallbladder and biliary tract and targeted therapy

Adenocarcinomas of the gallbladder (GBC) and bile ducts (cholangiocarcinoma) (combined as biliary tract cancers, BTC) are uncommon tumors in the United States, but are endemic in parts of South America and Asia. BTC are aggressive tumors with poor survival. Published response rates to chemotherapy are less than 30% and no survival benefit has been demonstrated from palliative systemic therapy. Improved understanding of the biological characteristics and molecular carcinogenic mechanisms of these malignancies may lead to improved therapeutic regimens for patients.

Role of epigenetic alterations in cholangiocarcinoma

Intrahepatic cholangiocarcinomas are rare malignant epithelial liver tumors arising from intrahepatic bile ducts. The prognosis of affected patients is poor. Several risk factors, including hepatolithiasis, liver fluke infection, and anatomical abnormalities associated with inflammation of the biliary tract have been described. At present, little is known about the cellular and molecular mechanisms leading to the development of cholangiocarcinoma. In recent years, in addition to genetic alterations, epigenetic inactivation of (tumor suppressor) genes by promoter CpG island hypermethylation has been recognized as an important and alternative mechanism in tumorigenesis. This review discusses the epi-genetic inactivation of different tumor suppressor genes in cholangiocarcinoma.

Prognostic significance of microsatellite alterations at 1p36 in cholangiocarcinoma

AIM: To investigate loss of heterozygosity (LOH) and microsatellite instability (MSI) on the chromosomal region 1p36-pter in cholangiocarcinoma (CCA) patients and determine the association between microsatellite alterations and clinicopathological parameters.

METHODS: Ten polymorphic microsatellite markers were determined for LOH and MSI using GS-3000 gel scan fragment autoanalyzer.

RESULTS: Sixty-eight out of 90 cases (75.6%) showed LOH in one or more loci. LOH was found most frequently at D1S199 (40.0%), D1S507 (34.6%), D1S2845 (30.5%), and D1S2734 (30.1%). MSI was found in 34 of 90 cases (37.8%) at one or more loci. Fine mapping at 1p36 showed two distinctive regions of common loss, which were D1S2845 and the 25.5-cM region between D1S507 and D1S2734, indicating the existence of putative tumor suppressor genes that is likely to play important roles in the development of CCA. Patients with LOH at D1S234 showed less lymphatic invasion (P = 0.017), whereas patients with LOH at D1S2676 exhibited more lymphatic invasion than those without (P = 0.031). LOH at D1S2845 showed a significant correlation with nerve invasion (P = 0.029). Moreover, patients who demonstrated MSI at D1S228 showed a poor prognosis (P = 0.0026).

CONCLUSION: Allelic loss plays a major role in microsatellite alterations at chromosome 1p36, which may contribute to carcinogenesis and pathogenesis of liver fluke related CCA and these alterations can be used as molecular prognostic indicators for CCA patients.

Chromosomal imbalances in Korean intrahepatic cholangiocarcinoma by comparative genomic hybridization

Intrahepatic cholangiocarcinoma (ICC) arises from epithelial cells in the intrahepatic bile duct. Until now, only few reports have been available concerning the genetic changes during the progression of ICC. In this study, we analyzed chromosomal aberrations in 19 frozen ICC samples using comparative genomic hybridization. The common chromosomal gains were observed in 8q22 approximately qter (11 cases, 58%), 5p14 approximately pter (32%), 2q33 approximately qter (26%), 7p (26%), 17q21 approximately q22 (26%), 18q12 approximately q21 (26%), and 19q13.1 (26%). DNA amplification was identified in nine tumors (47%). Chromosomal loss was found in Y (60%), 1p34 approximately pter (37%), 4q(32%), 18q21 approximately qter (32%) 19p (32%), X (32%), 5q11 approximately q14 (26%), 8p(26%), 9p (26%), and 17p (26%). Chromosomal aberrations identified in this study provide candidate regions involved in the tumorigenesis and progression of ICC.

Microsatellite alterations in hepatocellular carcinoma and intrahepatic cholangiocarcinoma

A series of 20 hepatocellular carcinomas and 8 intrahepatic cholangiocarcinomas was screened from the Korean population for microsatellite alterations, including a loss of heterozygosity and replication errors using nine microsatellite markers containing several genes. The microsatellite results and our previous comparative genomic hybridization results of two tumors were compared at each locus, and the correlations between these and clinicopathologic variables were examined. The most characteristic findings were found at 13q. Replication errors were prevalent at D13S160 (13q21.2 approximately q31) and D13S292(13q12). The incidence of loss of heterozygosity, however, was higher at D13S153 (13q14.1 approximately q14.3) and D13S265(13q31 approximately q32). In contrast, there were higher deletion frequencies observed in hepatocellular carcinoma (HCC) and higher amplification frequencies observed in intrahepatic cholangiocarcinoma at 13q in our previous comparative genomic hybridization (CGH) study. Higher frequencies of replication errors were observed at D16S408 (13q12 approximately q21) and D16S504(13q23 approximately q24) in the HCC. This study found that significant differences in the patterns of genetic instability of microsatellites were dependent on the chromosomal loci. It is believed that certain genes at altered CGH regions, which are relevant to the development and/or progression of these cancers, are activated by different mutation mechanisms.

Alteration of the fragile histidine triad gene in intrahepatic cholangiocarcinoma

BACKGROUND AND AIMS

Intrahepatic cholangiocarcinoma is the second most common intrahepatic neoplasm, accounting for 10-30% of primary liver cancers. Since little is known about the development of this cancer, we searched for alterations to the fragile histidine triad (FHIT) gene, a putative tumour suppressor gene on chromosome 3p14.2. In addition, we investigated oncogenic mutations in beta-catenin, which lead to an activated Wnt signalling pathway and microsatellite instability as a consequence of mismatch repair deficiency.

METHODS AND RESULTS

Loss of heterozygosity at the FHIT/FRA3B locus was detected in two out of ten informative cases (20%) using the marker D3S1300 and in one out of seven informative cases (14%) by marker D3S1234. Furthermore, immunohistochemistry revealed loss of Fhit expression in most of the 19 intrahepatic cholangiocarcinomas analysed, although to varying degrees. Oncogenic mutations were excluded in exon 3 of the beta-catenin gene by restriction enzyme digest and DNA sequence analysis. Microsatellite instability could not be detected in the tumour specimens tested using a validated marker panel. In two out of nine informative cases (22%), loss of heterozygosity was displayed close to the adenomatous polyposis coli (APC) gene.

CONCLUSIONS

Alterations to FHIT/FRA3B were initially detected by allelic losses of genomic DNA in intervening sequences of this tumour suppressor gene. Immunohistochemistry extended this initial observation by demonstrating that seven of the 19 intrahepatic cholangiocarcinomas had entirely lost expression of FHIT. Loss of Fhit protein in only a subpopulation of tumour cells due to oligoclonality may explain the varying portions of negative staining observed in the other tumour samples. Microsatellite instability did not appear to contribute to the development of intrahepatic cholangiocarcinoma in the cohort of tumours we analysed. Furthermore, the Wnt pathway may be constitutively turned on by inactivation of the APC gene due to deletion of genomic DNA but not by oncogenic mutations within exon 3 of the beta-catenin gene.

Frequent loss of chromosome 3p and hypermethylation of RASSF1A in cholangiocarcinoma

BACKGROUND/AIMS

Cholangiocarcinoma comprises 5-20% of all primary malignant tumors of the liver. However, the lack of information about the genetic basis of cholangiocarcinoma has impeded characterization and understanding of its biological behavior.

METHODS

In this study, genome-wide aberrations in 13 cases of cholangiocarcinoma were examined by the molecular cytogenetic technique, comparative genomic hybridization.

RESULTS

Frequent gains of 1q, 3q, 8q, 15q and 17q, and common losses on 3p, 4q, 6q, 9p, 17p and 18q were found. The finding of common chromosome 3p loss (approximately 40%) with a minimal deleted region of 3p13-p21 has prompted our further investigation on the tumor suppressor gene RASSF1A, located at 3p21.3. Using bisulphite modification followed by methyl-specific PCR, a high incidence of methylated RASSF1A promoter region was detected in our current series (9/13 cases; 69%). Further expression analysis on the nine cases with promoter hypermethylation indicated much reduced RASSF1A expression compared to normal livers.

CONCLUSIONS

Our current molecular cytogenetic investigation on primary cholangiocarcinoma provided overall karyotypic information and represents the first report on the methylation status of RASSF1A in cholangiocarcinoma. The high incidence of 3p loss and RASSF1A promoter hypermethylation detected may have implications for this tumor suppressor gene in the malignant progression of cholangiocarcinoma.

Cellular and molecular biology of biliary tract cancers

Cancer of the biliary tract has been associated with point mutations of K-ras and beta-catenin proto-oncogenes; alterations of p53, p16, APC, and DPC4 tumor suppressor genes by a combination of chromosomal deletion, mutation, or methylation; and infrequently microsatellite instability. The frequencies of these alterations vary by location and race of the patient, tumor subsite, histology, and associated disease. Advances in the understanding of the genetics of this disease will help in diagnosing biliary tract cancer, screening at-risk patients, and developing therapies.

Cholangiocarcinoma: recent progress. Part 2: molecular pathology and treatment

Part 2 of this review discusses DNA damage in biliary epithelial cells in the development of cholangiocarcinoma, alterations in cell kinetics of biliary epithelial cells, biliary epithelial mitoinhibition, and apoptosis that includes the role of Bcl-2, transforming growth factor-beta, telomerase activities and deregulation of Ras and p53, cancer-associated antigens in cholangiocarcinoma, precancerous lesions, stroma formation and angiogenesis, cancer invasion, cell-cell and cell-matrix interactions, and the mechanism of evasion from immune surveillance. These discussions are followed briefly by treatments such as photodynamic therapy, and surgical approaches comparing resection and liver transplantation.

Microsatellite alterations in liver fluke related cholangiocarcinoma are associated with poor prognosis

We have characterized the role of genetic alterations in the development of liver fluke related cholangiocarcinoma. We analyzed the loss of heterozygosity (LOH) and microsatellite instability (MSI) of hMSH2, hMLH1, and p53 genes in 55 patients with intrahepatic cholangiocarcinoma by using polymerase chain reaction based microsatellite markers D2S119, D3S1611, and TP53, respectively and determined the association between microsatellite alterations and patient survival. A total of 27 (49.1%) out of 55 cases exhibited microsatellite alterations in one locus or more. Of 55 samples, 11 (20%) demonstrated MSI at D2S119 and four (7%) showed MSI at D3S1611. LOH was shown in seven out of 36 (19%) informative cases for D3S1611 and 16 out of 50 (32%) for TP53. Microsatellite alterations at loci studied were significantly associated with poor survival (P=0.0098). This study suggests that genetic alterations of DNA mismatch repair genes and tumor suppressor gene p53 may be involved in cholangiocarcinogenesis and these alterations may be of value as prognostic indicators for liver fluke related cholangiocarcinoma.

Physical and transcriptional map of the critical region for keratolytic winter erythema (KWE) on chromosome 8p22-p23 between D8S550 and D8S1759

Keratolytic winter erythema is an autosomal dominant skin disorder characterised by erythema, hyperkeratosis, and peeling of the skin of the palms and soles, especially during winter. The keratolytic winter erythema locus has been mapped to human chromosome 8p22-p23. This chromosomal region has also been associated with frequent loss of heterozygosity in different types of cancer. To identify positional candidate genes for keratolytic winter erythema, a BAC contig located between the markers at D8S550 and D8S1695 was constructed and sequenced. It could be extended to D8S1759 by a partially sequenced BAC clone identified by database searches. In the 634 404 bp contig 13 new polymorphic microsatellite loci and 46 single nucleotide and insertion/deletion polymorphisms were identified. Twelve transcripts were identified between D8S550 and D8S1759 by exon trapping, cDNA selection, and sequence analyses. They were localised on the genomic sequence, their exon/intron structure was determined, and their expression analysed by RT-PCR. Only one of the transcripts corresponds to a known gene, encoding B-lymphocyte specific tyrosine kinase, BLK. A putative novel myotubularin-related protein gene (MTMR8), a potential human homologue of the mouse acyl-malonyl condensing enzyme gene (Amac1), and two transcripts showing similarities to the mouse L-threonine 3-dehydrogenase gene and the human SEC oncogene, respectively, were identified. The remaining seven transcripts did not show similarities to known genes. There were no potentially pathogenic mutations identified in any of these transcripts in keratolytic winter erythema patients.

Allelic loss of chromosome 3p24 correlates with tumor progression rather than with retinoic acid receptor beta2 expression in breast carcinoma

A tumor suppressor gene. retinoic acid receptor (RAR) beta2, has been mapped to chromosome 3p24, a region where loss of heterozygosity (LOH) has been observed commonly in carcinomas of various tumor tissues. RAR beta2 expression is reduced or lost in many malignant tumors including breast cancer, however, whether LOH accounts for the loss of expression of RAR beta2 in breast cancer is unknown. We, therefore, assessed LOH on chromosome band 3p24 to correlate it with RAR beta2 expression and other established prognostic parameters in 52 breast carcinomas. Based on three microsatellites, D3S 1283, D3S 1293 and D3S 1286. all of the tumors were informative, of these, 12 (23%) exhibited LOH. RAR beta2 expression was lost in 42% (19/45) of these samples. We found that LOH on chromosome band 3p24 was not correlated with loss of RAR beta2, but correlated with higher histological grade, p53-positivity, and loss of estrogen and progesterone receptors. Our findings suggest that LOH of the RAR beta2 gene does not account for the frequent loss of RAR beta2 expression in breast cancer but the genomic structural alteration at or close to the RAR beta2 gene locus are likely to be associated with tumor progression and/or loss of hormonal dependency.

Identification and localization of a new human myotubularin-related protein gene, mtmr8, on 8p22-p23

Myotubularin and myotubularin-related proteins are dual-specificity phosphatases. Several myotubularin-related proteins have been identified in humans and mice. The members of the myotubularin protein family are highly conserved, from humans to yeast. Mutations in the human myotubularin gene (MTM1) lead to X-linked myotubular myopathy. Here we isolate and localize a novel putative myotubularin-related protein gene (MTMR8) on chromosome 8p22--p23,between the markers D8S550 and D8S265, by exon-trapping experiments and RT-PCR. Genomic sequencing revealed that the gene consists of 10 exons and spans approximately 43 kb. The corresponding cDNA is 7081 bp. The open reading frame predicts a protein of 549 amino acids and a calculated molecular mass of 63 kDa. Like myotubularin-related protein-5, MTMR8 has no dual-specificity phosphatase domain. It contains a double-helical motif similar to the SET interaction domain, which is thought to have a role in the control of cell proliferation.