Comparative genomic hybridization analysis of hepatoblastomas

Copy Number Alterations in Hepatoblastoma: Literature Review and a Brazilian Cohort Analysis Highlight New Biological Pathways

Hepatoblastoma (HB) is a rare embryonal tumor, although it is the most common pediatric liver cancer. The aim of this study was to provide an accurate cytogenomic profile of this type of cancer, for which information in cancer databases is lacking. We performed an extensive literature review of cytogenetic studies on HBs disclosing that the most frequent copy number alterations (CNAs) are gains of 1q, 2/2q, 8/8q, and 20; and losses at 1p and 4q. Furthermore, the CNA profile of a Brazilian cohort of 26 HBs was obtained by array-CGH; the most recurrent CNAs were the same as shown in the literature review. Importantly, HBs from female patients, high-risk stratification tumors, tumors who developed in older patients (> 3 years at diagnosis) or from patients with metastasis and/or deceased carried a higher diversity of chromosomal alterations, specifically chromosomal losses at 1p, 4, 11q and 18q. In addition, we distinguished three major CNA profiles: no detectable CNA, few CNAs and tumors with complex genomes. Tumors with simpler genomes exhibited a significant association with the epithelial fetal subtype of HBs; in contrast, the complex genome group included three cases with epithelial embryonal histology, as well as the only HB with HCC features. A significant association of complex HB genomes was observed with older patients who developed high-risk tumors, metastasis, and deceased. Moreover, two patients with HBs exhibiting complex genomes were born with congenital anomalies. Together, these findings suggest that a high load of CNAs, mainly chromosomal losses, particularly losses at 1p and 18, increases the tendency to HB aggressiveness. Additionally, we identified six hot-spot chromosome regions most frequently affected in the entire group: 1q31.3q42.3, 2q23.3q37.3, and 20p13p11.1 gains, besides a 5,3 Mb amplification at 2q24.2q24.3, and losses at 1p36.33p35.1, 4p14 and 4q21.22q25. An in-silico analysis using the genes mapped to these six regions revealed several enriched biological pathways such as ERK Signaling, MicroRNAs in Cancer, and the PI3K-Akt Signaling, in addition to the WNT Signaling pathway; further investigation is required to evaluate if disturbances of these pathways can contribute to HB tumorigenesis. The analyzed gene set was found to be associated with neoplasms, abnormalities of metabolism/homeostasis and liver morphology, as well as abnormal embryonic development and cytokine secretion. In conclusion, we have provided a comprehensive characterization of the spectrum of chromosomal alterations reported in HBs and identified specific genomic regions recurrently altered in a Brazilian HB group, pointing to new biological pathways, and relevant clinical associations.

Patient-derived mouse xenografts from pediatric liver cancer predict tumor recurrence and advise clinical management

Identification of new treatments for relapsing pediatric cancer is an unmet clinical need and a societal challenge. Liver cancer occurrence in infancy, 1.5 for million children per year, falls far below the threshold of interest for dedicated drug development programs, and this disease is so rare that it is very difficult to gather enough children into a phase II clinical trial. Here, we present the establishment of an unprecedented preclinical platform of 24 pediatric liver cancer patient-derived xenografts (PLC-PDXs) from 20 hepatoblastomas (HBs), 1 transitional liver cell tumor (TCLT), 1 hepatocellular carcinoma, and 2 malignant rhabdoid tumors. Cytogenetic array and mutational analysis of the parental tumors and the corresponding PLC-PDXs show high conservation of the molecular features of the parental tumors. The histology of PLC-PDXs is strikingly similar to that observed in primary tumors and recapitulates the heterogeneity of recurrent disease observed in the clinic. Tumor growth in the mouse is strongly associated with elevated circulating alpha-fetoprotein (AFP), low rate of necrosis/fibrosis after treatment, and gain of chromosome 20, all indicators of resistance to chemotherapy and poor outcome. Accordingly, the ability of a tumor to generate PLC-PDX is predictive of poor prognosis. Exposure of PLC-PDXs to standards of care or therapeutic options already in use for other pediatric malignancies revealed unique response profiles in these models. Among these, the irinotecan/temozolomide combination induced strong tumor regression in the TCLT and in a model derived from an AFP-negative relapsing HB.

CONCLUSION

These results provide evidence that PLC-PDX preclinical platform can strongly contribute to accelerate the identification and diversification of anticancer treatment for aggressive subtypes of pediatric liver cancer. (Hepatology 2016;64:1121-1135).

Upregulated genes at 2q24 gains as candidate oncogenes in hepatoblastomas

AIM

Cytogenetic data of hepatoblastomas, a rare embryonal tumor of the liver, mostly consist of descriptions of whole-chromosome aneuploidies and large chromosome alterations. High-resolution cytogenetics may provide clues to hepatoblastoma tumorigenesis and indicate markers with clinical significance.

PATIENTS & METHODS

We used array-CGH (180K) to screen for genomic imbalances in nine hepatoblastomas. Additionally, we investigated the expression pattern of selected genes exhibiting copy number changes.

RESULTS

Analysis showed mainly whole-chromosome or chromosome-arm aneuploidies, but some focal aberrations were also mapped. Expression analysis of 48 genes mapped at one 10 Mb amplification at 2q24 revealed upregulation of DAPL1, ERMN, GALNT5, SCN1A and SCN3A in the set of tumors compared with differentiated livers.

CONCLUSION

These genes appear as candidates for hepatoblastoma tumorigenesis.

Cytogenetic and array comparative genomic hybridization analysis of a series of hepatoblastomas

Hepatoblastoma is the most common primary hepatic tumor in children, and only a limited number of detailed karyotypic analyses have been reported to date. In the present study, cytogenetic abnormalities were identified in nine cases of hepatoblastoma from a single institution. Among characteristic chromosomal changes detected were simple numerical aberrations, structural alterations of chromosomes 1, 2, and 8, and the recurrent unbalanced rearrangements der(4)t(1;4)(q25.2;q35.1) and der(6)t(1;6)(q21;q26). Array comparative genomic hybridization was applied in four of the cases. The combined cytogenetic, molecular cytogenetic, and histopathologic analyses are presented here, together with clinical data. The results substantially confirm previous findings of aberrations involving chromosomal loci on 1q, 2 or 2q, 4q, 6q, 8 or 8q, and 20 as significant in the development and clinical course of this disease.

Whole-genome profiling of chromosomal aberrations in hepatoblastoma using high-density single-nucleotide polymorphism genotyping microarrays

To identify the genomic profile and elucidate the pathogenesis of hepatoblastoma (HBL), the most common pediatric hepatic tumor, we performed high-density genome-wide single-nucleotide polymorphism (SNP) microarray analyses of 17 HBL samples. The copy number analyzer for GeneChip(R) (CNAG) and allele-specific copy number analysis using anonymous references (AsCNAR) algorithms enabled simple but sensitive inference of allelic composition without using paired normal DNA. Chromosomal aberrations were observed in 15 cases (88%). Gains in chromosomes 1q, 2 (or 2q), 8, 17q, and 20 and losses in chromosomes 4q and 11q were frequently identified. High-grade amplifications were detected at 7q34, 14q11.2, and 11q22.2. Several types of deletions, except homozygous deletion, were identified. Most importantly, copy-neutral loss of heterozygosity (uniparental disomy [UPD]) at 11p15 was detected in four of the 17 HBL samples. Insulin-like growth factor II (IGF2) and H19 genes were located within this region. The methylated status of this region indicated the paternal origin of the UPD. The expression patterns of IGF2 and H19 were opposite between genes with and without the UPD. This difference in the expression patterns might influence the clinical features of HBL.

Comparative genomic hybridization detects an increased number of chromosomal alterations in large cell/anaplastic medulloblastomas

We correlate chromosomal changes in medulloblastomas with histologic subtype, reporting the analysis of 33 medulloblastoma specimens by comparative genomic hybridization, and a subset by fluorescence in situ hybridization. Of the 33 tumors, 5 were desmoplastic/nodular, 10 were histologically classic, and 18 were large cell/anaplastic. Chromosomal gains and losses were more common in anaplastic medulloblastomas than in non-anaplastic ones. We identified 4 medulloblastomas with c-myc amplification and 5 medulloblastomas with N-myc amplification; all 9 were of the large cell/anaplastic subtype. Additional regions with high level gains included 2q14-22, 3p23, 5p14-pter, 8q24, 9p22-23, 10p12-pter, 12q24, 12p11-12, 17p11-12, and Xp11. The majority of these high level gains occurred in anaplastic cases. We also found loss of chromosome 17p in 7 large cell/anaplastic cases but no nonanaplastic medulloblastomas. Finally, we detected a significantly increased overall number of chromosomal alterations in large cell/anaplastic medulloblastomas (6.8/case) compared to non-anaplastic ones (3.3/case). These findings support an association between myc oncogene amplification, 17p loss, and large cell/anaplastic histology.

Imbalances of chromosome arm 1p in pediatric and adult germ cell tumors are caused by true allelic loss: A combined comparative genomic hybridization and microsatellite analysis

Previous studies on childhood germ cell tumors (GCTs) report highly variable frequencies of losses at chromosome arm 1p. Since deletions at 1p portend a poor prognosis in other embryonal tumors, this study aims to clarify the question of the frequency of true allelic loss at 1p and whether it constitutes a prognostic parameter. We analyzed 13 GCTs from different gonadal and extragonadal sites of children (4 teratomas, 9 malignant GCTs) and 18 GCTs of adolescents and adults (3 teratomas; 15 malignant GCTs) using automated microsatellite analysis with 23 polymorphic markers and chromosomal "high resolution" comparative genomic hybridization (HR-CGH). With this combined approach, we detected loss of heterozygosity (LOH) at 1p in 8/9 childhood malignant GCTs with concordant data from HR-CGH and microsatellite analyses. In contrast, LOH at 1p was not detected in childhood teratomas (0/4) and constituted a rare event in GCTs of adolescence and adulthood (3/18). The commonly deleted region was located at distal 1p36-pter, with a proximal boundary between the markers D1S450 and D1S2870. These data unequivocally demonstrate that deletion at 1p is common in childhood GCTs and results in allelic loss. This observation argues for the presence of a classical tumor suppressor at distal 1p. Considering the high frequency of LOH at 1p and the overall favorable prognosis of childhood GCTs, a prognostic impact of LOH at 1p in childhood GCTs appears unlikely. However, since two postpubertal tumors with LOH at 1p progressed, a prognostic relevance in this age group seems possible, warranting a prospective evaluation.

Cytogenetic evaluation of a large series of hepatoblastomas: Numerical abnormalities with recurring aberrations involving 1q12-q21

Hepatoblastoma is a malignant embryonal liver tumor that occurs almost exclusively in infants and very young children. Previous cytogenetic studies of hepatoblastoma have investigated small series or individual cases. This report is on the cytogenetics of a large series of 111 hepatoblastoma specimens, with cytogenetic results consecutively karyotyped over a 12-year period. Abnormal karyotypes were observed in 55 cases (approximately 50% of the total). Numerical aberrations were observed in 41 cases (36% of the total), particularly trisomies of chromosomes 2, 8, and 20. Chromosome losses were less common than chromosome gains. Structural abnormalities were observed in 43 cases (39% of the total). Unbalanced translocations resulting in trisomy 1q and involving breakpoints at 1q12-21 were the most common structural abnormality, observed in 20 tumors (18% of total cases); the corresponding translocated chromosome was highly varied. The previously reported t(1;4) was observed in seven cases. Most tumors with translocations involving 1q12-21 also displayed numerical chromosome aberrations, the most common of which were chromosomal trisomies, whereas tumors with other structural rearrangements had fewer numerical abnormalities.

Interactions between Prostaglandin E2, Liver Receptor Homologue-1, and Aromatase in Breast Cancer

Local synthesis of estrogens within breast adipose tissue by cytochrome P450 aromatase contributes to the growth of postmenopausal breast cancers. One of the major stimulators of aromatase expression in breast is prostaglandin E2 (PGE2) derived from tumorous epithelium and/or infiltrating macrophages. Recently, the orphan nuclear receptor, liver receptor homologue-1 (LRH-1), has also been shown to regulate aromatase expression in breast adipose tissue. We therefore examined the expression of, and correlations between, aromatase and LRH-1 mRNA in a panel of breast carcinoma tissues and adjacent adipose tissue. LRH-1 mRNA expression was low in normal breast tissue but markedly elevated in both breast carcinoma tissue and adipose tissue surrounding the tumor invasion (thereby paralleling aromatase expression). Laser capture microdissection localized the site of LRH-1 expression to tumor epithelial cells but not to intratumoral stromal cells. A strong correlation between LRH-1 and aromatase mRNA levels was observed in tumor-containing adipose tissue but not in tumor tissue. Ectopic expression of LRH-1 in primary human adipose stromal cells strongly activated endogenous aromatase mRNA expression and enzyme activity. Finally, treatment of adipose stromal cells with PGE2 induced expression of both LRH-1 and aromatase. We suggest that PGE2 derived from breast tumor tissue may increase aromatase expression in the surrounding adipose stroma in part by inducing LRH-1 in these cells. The roles of LRH-1 in breast cancer proliferation merit further study.

Hepatoblastoma in a patient with a partial trisomy 9p syndrome: a case report

After an uneventful pregnancy, a boy was born by vacuum extraction at 40.6 weeks' gestation. Physical examination revealed several malformations due to a partial trisomy 9p [karyotype: 46,XY, dup(9)(p13p24)]. Three months after birth, the boy presented with a hepatoblastoma without distant metastases which was treated with chemotherapy combined with surgery. At the last follow-up, 15 years after the resection of the hepatoblastoma, he was still in complete remission. To our knowledge this is the first case report of a patient with a constitutional partial trisomy 9p associated with hepatoblastoma.

Amplification and overexpression of the IGF2 regulator PLAG1 in hepatoblastoma

There is evidence that 8q amplification is associated with poor prognosis in hepatoblastoma. A previous comparative genomic hybridization analysis identified a critical region in chromosomal bands 8q11.2-q13. Using restriction landmark genomic scanning in combination with a virtual genome scan, we showed that this region is delineated by sequences within contig NT_008183 of chromosomal subbands 8q11.22-q11.23. A real-time PCR-based genomic copy number assay of 20 hepatoblastomas revealed gain or amplification in this critical chromosomal region in eight tumors. The expression of four genes and expressed sequence tags (ESTs) within this newly defined region was assayed by real-time reverse transcriptase polymerase chain reaction (RT-PCR) in four tumors with and six tumors without gain or amplification. The PLAG1 oncogene was found to be highly expressed in all but one tumor compared to normal liver tissue. Furthermore, quantitative RT-PCR revealed that the expression level of the developmentally regulated transcription factor PLAG1 was 3-12 times greater in hepatoblastoma tumors and cell lines compared to age-matched normal liver and comparable to the expression in fetal liver tissue. PLAG1 has been shown be a transcriptional activator of IGF2 in other tumor types. Using luciferase reporter assays, we demonstrated that PLAG1 transactivates transcription from the embryonic IGF2 promoter P3, also in hepatoblastoma cell lines. Thus, our results provide evidence that PLAG1 overexpression may be responsible for the frequently observed up-regulation of IGF2 in hepatoblastoma and therefore may be implicated in the molecular pathogenesis of this childhood neoplasia.

Comparative genomic hybridization analysis of hepatoblastoma reveals high frequency of X-chromosome gains and similarities between epithelial and stromal components

Hepatoblastoma (HB) is the most common liver tumor in childhood and differs in its environmental risk factors and genetic background from hepatocellular carcinoma. HB is associated with inherited conditions such as familial adenomatous polyposis and Beckwith-Wiedemann syndrome, suggesting the importance of genetic abnormalities in the pathogenesis and progression of this disease. It has a very polymorphous morphology. A diverse range of cytogenetic alterations has been reported to date, the most frequent being trisomy 2 and trisomy 20. Thirty-five HB specimens from 31 patients (22 purely epithelial, 4 purely mesenchymal, 9 mixed) were examined by comparative genomic hybridization (CGH), a technique that enables us to screen the entire tumor genome for genetic losses and gains. Our aims were as follows: (1) to characterize chromosome abnormalities that appear in this tumor and (2) to identify possible differences between different histologic subtypes of HB. We found significant gains of genetic material, with very little difference in the number and type of alterations between the different histologic components of HB. The most frequent alterations were gains of Xp (15 cases, 43%) and Xq (21 cases, 60%). This finding was also confirmed by fluorescent in situ hybridization performed on nuclei extracted from 6 specimens. Other common alterations were 1p-, 2q+, 2q-, 4q-, and 4q+. We found no difference between different histologic subtypes, a finding that may be in agreement with the hypothesis of a common clonal origin for the different components. An hitherto-unreported high frequency of X chromosome gains may support the assumption that X-linked genes are involved in the development of this neoplasm.

Two novel in vitro human hepatoblastoma models, HepU1 and HepU2, are highly characteristic of fetal-embryonal differentiation in hepatoblastoma

Using comparative genomic hybridization (CGH), we present a genome-wide screening of a mixed mesenchymal-epithelial hepatoblastoma, its recurrence and 2 novel hepatoblastoma cell lines raised from the ascites, 18 (HepU1) and 23 (HepU2) months after diagnosis of a hepatoblastoma in a 35-month-old boy. Both cell lines were also characterized by GTG-banding, multicolor-fluorescence in situ hybridization (M-FISH) and multicolor banding (M-Band). On the basis of CGH, we compared the cytogenetics of histologically different tumor areas of the parental tumor and its recurrence with the hepatoblastoma cell lines. We found different CGH profiles in the parental tumor rev ish enh(1q31-q32,8p,12,17,20,X), dim(4q34-q35,18q23)[cp] and its recurrence rev ish enh(8q24,17,Xq26-q28), dim(7q11.2-q21,13q34)[cp]. Although both epithelial cell lines were obtained at different times and the clonal ancestor of HepU2 had been exposed to a higher cumulative dose of chemotherapy, HepU1 and HepU2 have an identical karyotype: 48-56,XY,+Y,dup(2)(q32-q34),t(3;4)(q21;q34),+8,+12,+13, +17,+t(18;19)(q21;q?),+20[cp] and identical CGH profiles: rev ish enh(2q24-q33,8,12,13q,17,20), dim(4q34-q35,18q22-q23). In common with previously described hepatoblastoma cell lines, HepU1 and HepU2 demonstrate a gain of chromosome 20. The in situ aberrations most closely resembling that of HepU1 and HepU2 were found in areas of fetal-embryonal differentiation of the primary tumor. Interestingly, both cell lines mimic this histology in their three-dimensional growth pattern in vitro. HepU1 and HepU2 are thus cytogenetically and phenotypically highly characteristic of fetal-embryonal hepatoblastoma.

hTERT gene amplification and increased mRNA expression in central nervous system embryonal tumors

High-level gains at 5p15, a chromosomal region including the human telomerase catalytic protein subunit (hTERT) gene, have been documented in several medulloblastomas. We therefore analyzed hTERT gene dosage in a group of medulloblastomas and other embryonal brain tumors using differential PCR. Amplification of the hTERT locus was detected in 15 of 36 (42%) tumors examined. To correlate gene amplification with message level, we used real-time quantitative PCR to measure hTERT mRNA in 50 embryonal brain tumors. hTERT mRNA was detected in all but one of these cases, and mRNA level correlated significantly with gene dosage (r = 0.82). Log-rank analysis of survival data revealed a trend toward poor clinical outcomes in patients with medulloblastomas containing high hTERT mRNA levels, but clinical follow-up was relatively short and the association was not statistically significant (P = 0.078). Comparative genomic hybridization was used to further analyze the tumor with the greatest hTERT gene dosage and mRNA level, a recurrent medulloepithelioma. hTERT was amplified in the recurrent tumor but not in the primary lesion, suggesting this locus can be involved in tumor progression. Our data indicate that hTERT gene amplification is relatively common in embryonal brain tumors, and that increased expression of hTERT mRNA may be associated with biologically aggressive tumor behavior.

Tetrasomy 15q25.3 --> qter resulting from an analphoid supernumerary marker chromosome in a patient with multiple anomalies and bilateral Wilms tumors

We describe a girl who had been followed since birth for apparent Shprintzen-Goldberg syndrome (SGS), with macrosomia, long fingers and toes, and craniosynostosis, and presented at 4 years of age with bilateral Wilms tumors (also called nephroblastoma). Cytogenetic analysis of her peripheral blood revealed a de novo supernumerary marker chromosome. This stable marker chromosome is present in 19 of 20 lymphocytes analyzed, as well as in all 40 tumor cells (20 from each tumor) studied. Classical and molecular cytogenetic studies indicate that the marker is derived from an inverted duplication of chromosome 15q25.3 --> qter and contains a neocentromere. The presence of this marker chromosome in our patient results in tetrasomy 15q25.3 --> qter. The relationship between her genotype and phenotype are discussed in light of genes, including IGF1R and FES, mapped to the aneusomic segment.

Genetic alterations in hepatoblastoma and hepatocellular carcinoma: common and distinctive aspects

Hepatoblastoma (HB) and hepatocellular carcinoma (HCC) are two different subtypes of primary tumors arising from liver parenchymal cells. These tumors differ by many histoclinical characteristics, and comparative analysis of genetic alterations in HB and HCC might provide some clues on the molecular oncogenic pathways leading to hepatocyte transformation. Recent outcomes have been provided by the assessment of global genetic changes in tumor cells, using conventional cytogenetic approaches, PCR-based microsatellite analysis and Comparative genomic Hybridization (CGH). Cytogenetic studies of HB, microsatellite analysis of HCC and recent CHG data have outlined common and distinctive characters between the two tumor types. HBs are characterized by a low number of chromosomal changes, consisting mainly of gains at chromosomes 1q, 2, 8q, 17q, and 20. By contrast, HCCs harbor multiple chromosomal abnormalities, predominantly losses, with increased chromosomal instability in tumors associated with hepatitis B virus infection. Common alterations in HB and HCC include gain of chromosomes 1q, 8q, and 17q, and loss of 4q. Another important common feature shared by the two tumor types is the frequent activation of Wnt/beta-catenin signaling by stabilizing mutations of beta-catenin. Immunohistochemical analysis of beta-catenin has demonstrated nuclear/cytoplasmic accumulation of the protein in most HBs and in more than one third of HCCs. Strikingly, beta-catenin mutations are associated with chromosomal stability in both tumor types. Together, these studies define different pathways in liver cell transformation, reflecting various developmental stages and multiple risk factors. A detailed understanding of the molecular hits underlying liver tumorigenesis, combined with clinicopathological parameters, will permit an accurate evaluation of major targets for prognostic and therapeutic intervention.

Hepatoblastoma: cytomorphologic characteristics in serious cavity fluids

BACKGROUND

Hepatoblastoma (HBL) represents the most common primary hepatic tumor in children. Although the cytologic features of this tumor have been amply elucidated on fine-needle aspiration, exfoliative cytomorphologic characteristics have not been reported. The authors reviewed the cytopathologic features of six serous cavity fluids (SCF) from four patients with histologically proven HBL.

METHODS

Five of the specimens evaluated were peritoneal fluids, and one specimen was pleural fluid from a patient with suspected pulmonary metastasis. Slides were prepared by cytocentrifugation and stained with Diff-Quik and Papanicolaou stains. The cytomorphologic features of each specimen were characterized, subclassified, and correlated histopathologically.

RESULTS

All specimens showed hypercellular smears in a relatively clean background. Mixed embryonal and fetal subtypes of HBL disclosed three-dimensional clusters of neoplastic cells that formed straight or branched cords and acinus-like structures. The cells were moderately pleomorphic and had high nuclear-to-cytoplasmic (N/C) ratios. Occasional cells had eccentrically placed nuclei and vacuolated cytoplasm. Numerous mitotic figures were present. Rare intranuclear inclusions were noted. The anaplastic (small cell) subtype of HBL showed tight clusters of small, round, primitive cells with hyperchromatic nuclei, high N/C ratios, and prominent nuclear molding. In addition, there were numerous single cells with naked nuclei, often in an Indian-file configuration. Bile pigment, osteoid, and other mesenchymal components were absent in all specimens.

CONCLUSIONS

The cytomorphologic features of HBL in SCF are quite characteristic. Although the differential diagnosis includes other childhood small, round, blue cell tumors and hepatocellular carcinoma, the above findings in the appropriate clinical-radiologic setting warrant a diagnosis of HBL.

Genetic abnormalities in a pre and post-chemotherapy hepatoblastoma

Comparative genomic hybridization (CGH) analysis was performed on both a pre- and post-chemotherapy hepatoblastoma from a 24-month-old female patient. The diagnostic sample obtained from a tru-cut biopsy was a mixed epithelial-mesenchymal tumor with both fetal and embryonal patterns present. In contrast, the post-chemotherapy tumor exhibited a prominent anaplastic large cell population focally reminiscent of pleomorphic hepatocellular carcinoma (HCC). CGH analysis indicated that there were similarities as well as differences in the gains and losses of genetic material in each tumor. The diagnostic sample had gains of chromosome 1q, 2, 2(q31q33), 7, 8q, 12(q15q22), 17q and 20 material, while the post-chemotherapy tumor had gains of 1q, 2, 7, 8q, 10, 17q and 20 material. In addition, the pre- and post-chemotherapy samples may have incurred loss of chromosome 17p material. The main differences between the two samples involved localized gain of 2(q31q33) and 12(q15q22) in the pre-chemotherapy sample, and gain of chromosome 10 material in the post-chemotherapy tumor. The patient subsequently developed metastatic nodules in her lungs, the histology of which was identical in pattern to the diagnostic pattern, and appeared to have localized gain of 2(q31q33) and 12(q15q22). These results are consistent with published results that gain of chromosome 8q and 20 are associated with an unfavorable prognosis.

Compilation of published comparative genomic hybridization studies

The power of comparative genomic hybridization (CGH) has been clearly proven since the first paper appeared in 1992 as a tool to characterize chromosomal imbalances in neoplasias. This review summarizes the chromosomal imbalances detected by CGH in solid tumors and in hemopathies. In May of 2001, we took a census of 430 articles providing information on 11,984 cases of human solid tumors or hematologic malignancies. Comparative generic hybridization has detected a number of recurrent regions of amplification or deletion that allows for identification of new chromosomal loci (oncogenes, tumor suppressor genes, or other genes) involved in the development, progression, and clonal evolution of tumors. When CGH data from different studies are combined, a pattern of nonrandom genetic aberrations appears. As expected, some of these gains and losses are common to different types of pathologies, while others are more tumor-specific.

Cytogenetic findings in two new cases of hepatoblastoma

We describe two cases of hepatoblastoma occurring in an 18-month-old boy and a 3-month-old girl. Cytogenetic analysis of the primary tumors revealed gain of 2q and 20 in both cases. In case 1, t(7;8;11) was seen as a secondary abnormality. Other chromosomal aberrations seen in case 2 were unbalanced t(1;1) and t(2;11), resulting in partial gains of 1q and 2q. These results support previous reports that gains of 2q and 20 and rearrangement of chromosome 1 are strongly associated with hepatoblastoma and may be essential for establishing this neoplasm. The 11q and 7q abnormalities may represent a pathway of genetic evolution associated with hepatoblastoma progression.

Prognostic impact of molecular genetic alterations in hepatoblastoma

BACKGROUND

During recent years, we identified characteristic genetic alterations in sporadic hepatoblastoma (HB). These include loss of heterozygosity (LOH) at the chromosomal region 11p15.5, LOH on chromosome arms 1p and 1q, activating mutations in exon 3 of the beta-catenin gene, as well as overexpression of the c-met oncogene, which encodes the hepatocyte growth factor receptor. We now wanted to evaluate the prognostic relevance of these abnormalities concerning the outcome in a large group of patients.

PROCEDURE

All but 7 of 56 patients with HB were treated either with primary resection for small tumors, or neo-adjuvant chemotherapy with ifosfamide, cisplatin and doxorubicin (IPA) before delayed surgery in case of extended disease and additional adjuvant IPA therapy in all cases. Seven tumors were primarily resected and adjuvantly treated with different cytotoxic drugs. LOH 11p15.5, LOH 1p, and LOH 1q were detected in tumor tissue in comparison to normal liver and/or peripheral blood leukocytes by PCR based microsatellite analysis. Beta-catenin mutations were analysed with SSCP, deletion screening and direct sequencing. RT-PCR was used for identification of c-met mRNA overexpression. The results were correlated with the tumors' stage, histological type and epithelial differentiation, as well as with the patients' outcome.

RESULTS

Overall disease-free survival after median follow-up of 5 years was 43/56 patients (77%). LOH 11p15.5 was found in 15/56, LOH1p in 11/53, LOH1q in 7/53 and beta-catenin mutations in 25/55 HB. 13/23 HB had a c-met overexpression. LOH 11p15.5 and LOH 1p were significantly more often found in embryonal HB, while there was no correlation of other genetic alterations with histological type or differentiation. Furthermore, statistical analysis revealed no correlation of any of these disorders with initial tumor stage, nor with the patients' outcome.

CONCLUSION

None of the investigated molecular genetic alterations are suited to serve as a prognostic indicator in HB. Further investigations, especially genetic screening of tumor tissue may reveal prognostic markers for this neoplasm.

Frequent increase of DNA copy number in the 2q24 chromosomal region and its association with a poor clinical outcome in hepatoblastoma: cytogenetic and comparative genomic hybridization analysis

In a cytogenetic and comparative genomic hybridization (CGH) study of 38 hepatoblastomas, we found gain of 1q in 17 tumors (44.7%), that of 2 / 2q in 14 (36.8%), that of 20 / 20q in 9 (23.7%) and that of 8 / 8q in 8 (21.0%), loss of 4q in 4 (10.5%) and no DNA copy changes with normal karyotype or no mitotic cells in 11 (28.9%). Eleven tumors with 2 / 2q gain detected by CGH had a total chromosome 2 gain, a partial 2q gain, or a total chromosome 2 gain with an augmented partial 2q region; the common region for DNA copy gain was 2q24. Two-color fluorescence in situ hybridization (FISH) analyses using probes covering the centromere of chromosome 2 or HOXD13 (2q31) confirmed the CGH findings, and showed that the common region for gain in 2q was centromeric to HOXD13. Event-free survival (EFS) +/- standard error (SE) at 5 years was lowest in patients with 2q gain [37 +/- 15%], highest in those with no DNA copy changes [82 +/- 12%], and intermediate in those with DNA copy changes other than 2q gain [74 +/- 13%] (P = 0.0549). Multivariate analysis showed that 2q gain was an independent factor predicting a poor outcome. These findings suggest the presence of a growth-promoting gene or an oncogene in the 2q24 chromosome band, and a tumor suppressor gene in terminal 4q, which have important roles in the development and progression of hepatoblastoma.

Comparative genomic hybridization in polycythemia vera and essential thrombocytosis patients

Polycythemia vera (PV) and essential thrombocytosis (ET) are clonal chronic myeloproliferative disorders originating from a multipotent stem cell. Bone marrow examinations reveal chromosomal abnormalities in 15-43% of PV patients and 5% of ET patients, but no specific recurring abnormality has been found to date. We aimed to find cytogenetic aberrations in PV and ET by comparative genomic hybridization (CGH), a relatively new molecular cytogenetic technique. In this study, CGH analysis was performed on peripheral blood leukocytes of 12 PV patients and 8 ET patients. One patient (8.3%) with PV had an abnormal karyotype with a deletion in 7q11.2 and one patient with ET (12.5%) had a gain in 18p. Peripheral blood analysis by CGH revealed a low frequency of cytogenetic abnormalities in PV and ET patients. However, using CGH we were able to detect two cytogenetic aberrations that were not reported previously in these disorders.

Comparative genomic hybridization reveals population-based genetic alterations in hepatoblastomas

Hepatoblastoma is a malignant paediatric liver tumour. In order to approach the genetic background of this malignancy we have screened a panel of eighteen cases from Europe and Japan for chromosomal imbalances using comparative genomic hybridization (CGH). The most frequent losses included chromosomal regions 13q21-q22 (28%) and 9p22-pter (22%), while the most frequent gains occurred on 2q23-q24 (33%), 20q (28%) and 1q24-q25 (28%). A significant difference in CGH alterations between the tumours from patients of Caucasian and Japanese was revealed where loss of 13q was found only in the Japanese samples. In conclusion, the findings indicate several candidate regions for suppressor genes and oncogenes potentially involved in the hepatoblastomas of different ethnic origin.

Characterization of genomic alterations in hepatoblastomas. A role for gains on chromosomes 8q and 20 as predictors of poor outcome

As data on the genomic alterations in hepatoblastoma (HB) are limited, 34 HB tumors and three HB cell lines were screened for DNA copy number changes by comparative genomic hybridization. The average number of chromosomal imbalances per tumor was 2.3 +/- 0.5 (mean +/- SEM) with gains sevenfold more frequent than losses. The most frequent gains of chromosomal material in HB tumors were on 2q (44%), 1q (41%), 2p (29%), 20 (24%), 22q (18%), 8q (15%), 8p and 12q (9% each), as well as 7q, 12p, and 17 (6% each) and the only recurrent loss was on 4q in 12% of cases. Highly amplified sequences were identified in four tumors and mapped to 2q24 in two cases, to 8q in two cases (once to 8q11.2-q13 and once to 8q11.2-q21.3) as well as to 10q24-q26 in one case. In one cell line, highly amplified DNA sequences were mapped to 7p and 8q. Comparison to previously published data on this series of HB revealed that the number of chromosomal imbalances was significantly higher in HB tumors with loss of heterozygosity on 11p (P = 0.03), whereas in five of 10 HB biopsies without chromosomal imbalances, beta-catenin gene mutations were found. HB patients were divided into a good (no evidence of disease) and a poor (died of disease) outcome group according to their clinical course after standard therapy. Two alterations were found to be significantly associated with poor outcome: gain on 8q (P = 0.007) and gain on 20 (P = 0.009). In summary, our analysis allowed the identification of gains on chromosomes 1q and 2 as hallmark DNA copy number changes in HB with 2q24 as a critical chromosomal band. Furthermore, this study provided evidence that gains on 8q and 20 play a role as markers of prognostic significance in HB.

Current awareness

In order to keep subscribers up-to-date with the latest developments in their field, this current awareness service is provided by John Wiley & Sons and contains newly-published material on comparative and functional genomics. Each bibliography is divided into 16 sections. 1 Reviews & symposia; 2 General; 3 Large-scale sequencing and mapping; 4 Genome evolution; 5 Comparative genomics; 6 Gene families and regulons; 7 Pharmacogenomics; 8 Large-scale mutagenesis programmes; 9 Functional complementation; 10 Transcriptomics; 11 Proteomics; 12 Protein structural genomics; 13 Metabolomics; 14 Genomic approaches to development; 15 Technological advances; 16 Bioinformatics. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted