Immunoreactivity of sinusoids in hepatoblastoma: an immunohistochemical study using lectin UEA-1 and antibodies against endothelium-associated antigens, including CD34

Co-Expression of CD34, CD90, OV-6 and Cell-Surface Vimentin Defines Cancer Stem Cells of Hepatoblastoma, Which Are Affected by Hsp90 Inhibitor 17-AAG

Cancer stem cells (CSCs) are nowadays one of the major focuses in tumor research since this subpopulation was revealed to be a great obstacle for successful treatment. The identification of CSCs in pediatric solid tumors harbors major challenges because of the immature character of these tumors. Here, we present CD34, CD90, OV-6 and cell-surface vimentin (csVimentin) as reliable markers to identify CSCs in hepatoblastoma cell lines. We were able to identify CSC characteristics for the subset of CD34⁺CD90⁺OV-6⁺csVimentin⁺-co-expressing cells, such as pluripotency, self-renewal, increased expression of EMT markers and migration. Treatment with Cisplatin as the standard chemotherapeutic drug in hepatoblastoma therapy further revealed the chemo-resistance of this subset, which is a main characteristic of CSCs. When we treated the cells with the Hsp90 inhibitor 17-AAG, we observed a significant reduction in the CSC subset. With our study, we identified CSCs of hepatoblastoma using CD34, CD90, OV-6 and csVimentin. This set of markers could be helpful to estimate the success of novel therapeutic approaches, as resistant CSCs are responsible for tumor relapses.

Intravital assessment of angioarchitecture in rat hepatocellular nodules using in vivo fluorescent microscopy

Background

To prospectively evaluate the stepwise changes that occur in intra-nodular microvessels and microcirculation during the carcinogenesis process of hepatocellular nodules by using in vivo fluorescent microscopy, and to compare these with pathological changes.

Methods

Forty-five 10-week-old male Wistar rats received drinking water containing N-nitrosomorpholine at 10 mg/100 mL for 18weeks to develop multiple hepatocellular carcinomas (HCC) and dysplastic nodules (DN) in the liver; meanwhile, the non-lesion liver tissues become fibrotic. The microvascular morphological change and hemodynamic change of two lesion areas (HCC or DN) and one non-lesion area in each rat were observed with in vivo fluorescent microscope. After in vivo microscopy, 90 nodules and 45 non-lesion liver tissues that were observed were removed for pathological study. The microvessel density (MVD), branch density (BD), and cell density (CD) of these lesions were compared with the Kruskal-Wallis test and Mann-Whitney test, with an overall statistical significance of 0.05.

Results

The intra-nodular microvessels appeared tortuous, with irregular branching and abrupt diameter changes to form irregular convoluted networks in the HCC. This was distinctly different from the appearance of DN and non-lesion liver parenchyma. The MVD and BD of HCC were less than that of the DN and non-lesion liver parenchyma (P<0.01), and the BD of DN was also less than that of the non-lesion liver parenchyma (P<0.05). However, the MVD of the DN was similar to that of the non-lesion liver parenchyma (P>0.05). The CD of HCC was more than that of the DN and non-lesion liver parenchyma (P<0.05), and the CD of DN was also more than that of the non-lesion liver parenchyma (P<0.05).

Conclusions

Concurrent with the carcinogenesis process of the hepatocellular nodule, both the intra-nodular microvascular morphology and hemodynamics were stepwise changed, and the number of the intravascular lumen of intranodular microvessels decreased due to the infiltration and compression of intra-nodular parenchymal cells.

Co-option of Liver Vessels and Not Sprouting Angiogenesis Drives Acquired Sorafenib Resistance in Hepatocellular Carcinoma

Background: The anti-angiogenic Sorafenib is the only approved systemic therapy for advanced hepatocellular carcinoma (HCC). However, acquired resistance limits its efficacy. An emerging theory to explain intrinsic resistance to other anti-angiogenic drugs is ‘vessel co-option,’ ie, the ability of tumors to hijack the existing vasculature in organs such as the lungs or liver, thus limiting the need for sprouting angiogenesis. Vessel co-option has not been evaluated as a potential mechanism for acquired resistance to anti-angiogenic agents.

Methods: To study sorafenib resistance mechanisms, we used an orthotopic human HCC model (n = 4-11 per group), where tumor cells are tagged with a secreted protein biomarker to monitor disease burden and response to therapy. Histopathology, vessel perfusion assessed by contrast-enhanced ultrasound, and miRNA sequencing and quantitative real-time polymerase chain reaction were used to monitor changes in tumor biology.

Results: While sorafenib initially inhibited angiogenesis and stabilized tumor growth, no angiogenic ‘rebound’ effect was observed during development of resistance unless therapy was stopped. Instead, resistant tumors became more locally infiltrative, which facilitated extensive incorporation of liver parenchyma and the co-option of liver-associated vessels. Up to 75% (±10.9%) of total vessels were provided by vessel co-option in resistant tumors relative to 23.3% (±10.3%) in untreated controls. miRNA sequencing implicated pro-invasive signaling and epithelial-to-mesenchymal-like transition during resistance development while functional imaging further supported a shift from angiogenesis to vessel co-option.

Conclusions: This is the first documentation of vessel co-option as a mechanism of acquired resistance to anti-angiogenic therapy and could have important implications including the potential therapeutic benefits of targeting vessel co-option in conjunction with vascular endothelial growth factor receptor signaling.

Evaluation of gene expression related to hepatic cell maturation and differentiation in a chemically induced mouse hepatoblastoma cell line

The MHB-2 cell line, established from a mouse hepatoblastoma (HB), was subjected to the reverse transcriptase-polymerase chain reaction (RT-PCR) for evaluation of gene expression related to cell differentiation. RNAs for c-kit, CD34, thy-1, albumin, cytokeratin (CK) 8, 18 and 19 could be detected, but expression of alpha-fetoprotein, glucose-6-phosphatase, tyrosine aminotransferase and CK7 was not observed. MHB-2 cells were positive for CK8/18 but negative for c-kit, CD34, thy-1 and albumin on protein level. Immunohistochemical staining of the HB in vivo revealed diffusely expressed c-kit. Thy-1-positive HB cells were sparsely observed, but the tumor was negative for CD34 and rarely positive for CK8/18. By in situ hybridization, the HB was positive for CK18 but negative for CK19. Slight expression of albumin, but the lack of immature hepatocytic marker suggested some heterogeneous hepatocyte or an undifferentiated cell from other origin. Furthermore, positive expression of CK19 as well as CK8 and CK18 in culture strongly suggested the differentiation into a biliary lineage or the bidirectional state. In conclusion, the present study indicated the mouse HB to have de-differentiated, bipotent, or biliary-like cell characteristics, and considering the histological difference between HB and biliary tumors, it suggests the mouse HB cells are closely like some sort of hepatic undifferentiated cells.

The microcirculation in acute murine cutaneous incisional wounds shows a spatial and temporal variation in the functionality of vessels

A mouse perfusion model using fluorescently labeled dextran has been developed to investigate the functionality of blood vessels during cutaneous wound healing. By immunostaining cryostat sections of perfused wounds with antibodies that identify vessels, we were able to assess their functionality. There was an increase in the proportion of CD31(+)-perfused vessels in all wound regions with time, although the vessels of the wound margins and superficial granulation tissue (GT) took the longest to become perfused. More than 50% of the latter vessels were not perfused at 10 days postwounding. This is consistent with the growth of functional vessels from the wound base proceeding to the more superficial GT. The CD34 marker was expressed by a subpopulation of CD31(+) vessels. However, in contrast to CD31(+) vessels, the functionality of CD34(+) vessels did not change significantly with time and 50-75% of CD34(+) vessels in the GT and wound margins were nonfunctional. This might be explained either by apoptosis of the CD34(+) vessels or the loss of the marker with time. This study has important implications for assays of wound-healing angiogenesis based on histology and immunohistochemical markers for vessels, because vessel functionality differs both spatially and temporally during wound healing.

Neoangiogenesis and sinusoidal capillarization in hepatocellular carcinoma: correlation between dynamic CT and density of tumor microvessels

PURPOSE

To retrospectively evaluate the correlation between the degree of contrast enhancement on dynamic computed tomographic (CT) scans and the degree of neoangiogenesis and sinusoidal capillarization in hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

The institutional review board did not require approval or informed patient's consent for the review of medical records or images. Dynamic CT scans of 97 nodular HCCs in 97 patients (79 men, 18 women; age range, 29-73 years; mean age, 54 years) were evaluated in terms of the attenuation change in the arterial, portal venous, and delayed phases, and the results were correlated with the number of unpaired arteries and the degree of sinusoidal capillarization at histopathologic examination. The mean attenuation value of the nodular HCCs on triple-phase helical CT scans was correlated with the number of unpaired arteries and the degree of sinusoidal capillarization. Statistical analysis was performed with the Spearman rank correlation test.

RESULTS

The number of unpaired arteries in the nodular HCCs was found to correlate with the degree of contrast enhancement in the arterial phase (r = 0.225, P = .027), but did not correlate with the degree of contrast enhancement in the portal and delayed phases. The degree of sinusoidal capillarization did not correlate linearly with the mean attenuation of the nodular HCCs in any phase of contrast enhancement.

CONCLUSION

The degree of contrast enhancement of the nodular HCCs in the arterial phase tended to correlate with the number of unpaired arteries, but no correlation was evident between the degree of contrast enhancement and sinusoidal capillarization in any phase of CT imaging.

Neoplasm of hepatic stellate cells (spongiotic pericytoma): a new tumor entity in human liver

The purpose of this investigation was to classify a previously unknown tumor entity in human liver observed in a 35-year-old woman. It was characterized by an unusual accumulation of fusiform CD34-positive cells and was initially misconceived as a tumor of the liver sinusoids. The tissue was examined by light and electron microscopy and by immunocytochemical techniques with a broad spectrum of antibodies. The polycyclic tumor contained multiple nodular cell aggregates. The tumor cells possessed extensive cytoplasmic processes, rough endoplasmic reticulum, a prominent Golgi complex, and, in isolated cases, fat droplets. They expressed vimentin, CD34, CD105, CD99, CD56, and sm-actin. The matrix surrounding these cells was reactive for collagen types I, III and V, and fibronectin. The unusual aspect of this tumor is that it contained collections of cells that appeared to be hepatic stellate cells (Ito cells). It also contained hepatic cells arranged in plates, lobules, and capillarized sinuses. These findings suggest that the tumorous proliferation of hepatic stellate cells is functionally linked to the hepatocytes. It is unclear whether there is a link between the tumor and the patient's use of oral contraceptives. Referring to animal studies, different hepatocarcinogens may cause neoplastic Ito cell proliferation. The patient has remained recurrence-free during the 12 months since operation.

Stem-like cells in human hepatoblastoma

Hepatoblastoma is a pediatric liver tumor with epithelial components resembling embryonal and fetal liver cells. The existence of teratoid hepatoblastoma suggests the presence of stem cells in hepatoblastoma. The aim of this study was to analyze the expression of stem cell markers in hepatoblastomas. We studied specimens from 10 hepatoblastomas. Five of the hepatoblastomas were of epithelial and five of mixed type. Immunohistochemistry (IHC) for the stem cell markers CD34, Thy1, c-kit, and the hepatic or biliary lineage markers CK-18, OCH, CK-7, and CD56 was performed. Double IHC for stem cell and lineage markers was used to identify putative liver stem cells. The different markers showed distinct distributions on the tumor cells. Cells in atypical ducts were found to express simultaneously stem cell markers and hepatocytic or biliary lineage markers. Other cells in connective tissue showed c-kit expression, but not hepatic or biliary marker expression. The data show the presence of different cell populations bearing stem cell markers in human hepatoblastoma. Ductal cells co-expressing stem cell markers and hepatic lineage markers phenotypically resemble hepatic stem-like cells. These findings support the thesis that stem cells play a role in the histogenesis of hepatoblastoma.

Possible stem cell origin of human cholangiocarcinoma

AIM: To investigate the expression of CD34 and c-kit (receptor of stem cell factor) in cholangiocarcinoma.

METHODS: Fifteen cases of intrahepatic cholangiocarcinoma and 17 cases of extrahepatic cholangiocarcinoma were studied in this experiment. Using Envision detection system, paraffin-embedded sections of the resected cholangiocarcinoma tissue were stained with antibodies against CD34 and c-kit, respectively. The sections were counterstained with hematoxylin, and the results were examined under light microscope. Normal tonsil and mammary tissues were used as positive controls for CD34 and c-kit, respectively.

RESULTS: CD34 was positive in all sections, but only in capillary endothelial cells of tumor tissue. No cholangiocarcinoma cells were positive for CD34. In one case of extrahepatic cholangiocarcinoma, a few tumor cells (about 5%) were immunoreactive with c-kit.

CONCLUSION: CD34 or c-kit positive cells in liver tissue may represent liver stem cells, as they can differentiate into mature biliary cells in vitro. The expression of c-kit by some cholangiocarcinoma cells suggests that cholangiocarcinoma might originate from liver stem cells. However, other mechanisms of hepatocarcinogenesis, such as de-differentiation of mature cholangiocytes, may also exist.

Small cells in hepatoblastoma lack "oval" cell phenotype

Hepatoblastoma, a childhood tumor of the liver, is composed of epithelial and mesenchymal elements in varying proportions and at various stages of differentiation. The epithelial element recapitulates the stages of hepatocyte development from the primitive blastema through embryonal hepatocytes to fetal hepatocytes. The blastemal or undifferentiated cells have been postulated to represent neoplastic hepatocyte progenitor cells. In this study, we examine the immunophenotype of the various epithelial cells of hepatoblastoma with special emphasis on the small undifferentiated cell component and compare it with that of adult hepatocytes and hepatic stem (oval) cells. Putative stem cells in the liver can express all of the following markers: alpha-feto protein, CK19 (OV-6), chromogranin A, Bcl-2, HepPar-1, and alpha1 microglobulin. The latter, like alpha-feto protein, is a plasma protein synthesized by hepatocytes. Both alpha1 microglobulin and HepPar-1 are expressed in fetal liver cells as early as 7 weeks of intrauterine life. They are also expressed in hepatocellular carcinoma and in hepatocytic cell lines derived from normal fetal or adult liver. Formalin-fixed, paraffin-embedded archival tissues from 10 predominantly epithelial hepatoblastomas were immunostained with antibodies directed against CD 34, alpha1 microglobulin, Bcl-2, HepPar 1, and CK19 using the avidin-biotin-peroxidase method. The undifferentiated small cell component did not express any of the markers studied, namely, Bcl-2, HepPar-1, alpha(1) microglobulin, CD34, or CK19. Hepatocyte-like cells were alpha1 microglobulin- and HepPar-1-positive, with the intensity of staining correlating with the degree of hepatocytic differentiation. Bcl-2 expression was restricted to areas of ductular differentiation. CK19 was detected in foci that showed duct formation. The small cells of hepatoblastoma did not express HepPar-1, Bcl-2, CK19, alpha1 microglobulin, or CD34, markers that characterize the immunophenotype of hepatic stem cells ("oval" cells). Thus, this observation raises the following questions: (1) is "hepatoblastoma" a misnomer? (2) is the expression of tumor antigens dysregulated in hepatoblastoma? (3) does the liver have two different types of progenitor cells, oval cells and blastemal cells, with differing immunophenotypes? and (4) do the blastemal cells, rather than oval cells, represent the more primitive progenitor cells of the liver?

Tumoral angiogenesis and tissue factor expression during hepatocellular carcinoma progression in a transgenic mouse model

BACKGROUND/AIMS

The hypervascularity described in hepatocellular carcinoma varies according to the progression and the differentiation of the tumor, suggesting an angiogenic switch during tumor development.

METHODS

We used a transgenic mouse model of hepatocellular carcinoma induced by the expression of SV40-T antigen, in which male mice developed hepatic tumors at various temporal and histological stages, whereas female mice remained tumor-free. We analyzed, by immunostaining and reverse transcription-polymerase chain reaction, factors involved in tumoral angiogenesis.

RESULTS

We demonstrated that tumoral angiogenesis occurred before the development of diffuse hepatocarcinoma. We showed that some SV40-T-positive cells with an endothelial phenotype are involved in angiogenic processes, suggesting a partial vasculogenic mimicry. This tumoral angiogenesis is associated with platelet activation due to tissue factor expression in endothelial cells and invading macrophages. Normal and transgenic livers exhibited different pattern of expression of hypoxia-inducible factor 1 alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) mRNA.

CONCLUSIONS

This model of hepatocellular carcinoma displays marked tumoral angiogenesis, with proliferation, remodeling and arterialization of hepatic sinusoids, probably associated with a partial vasculogenic mimicry. Abnormal angiogenesis observed in hepatocarcinoma was associated with platelet activation by tissue factor (TF) produced by endothelial cells and invading macrophages. In this transgenic model, HIF-1alpha, VEGF, and TF play a crucial role in tumoral angiogenesis.

Stem-like cells in hepatoblastoma

BACKGROUND

The principles of tumor biology suggest that hepatoblastoma is derived from a pluripotent stem cell. Our studies were undertaken to investigate this tumor for the presence of cells with morphologic and immunophenotypic features of the oval cells of rodents that are thought to be closely related to hepatic stem cells.

PROCEDURE

Hepatoblastomas of various subtypes were investigated by electron microscopy and immunoelectron microscopy with antibodies against cytokeratin 7, in the liver a marker of biliary differentiation, and albumin, a marker of hepatocytic differentiation. Immunohistochemical investigations were performed with the antibodies OV-1 and OV-6, which recognize antigens associated with oval cells.

RESULTS

OV-1 stained scattered cells in seven of 12 tumors investigated and OV-6 in nine. Small epithelial cells (SEC) with the ultrastructural features of the oval cells were found by electron microscopy. They were characterized by small size (7-18 microm), often an oval shape, tonofilament bundles, and tight junctions or desmosome-like junctions. SEC were found in small numbers in areas of fetal differentiation and in moderate numbers in areas of embryonal differentiation. In small cell hepatoblastoma, nearly all the tumor cells exhibited SEC-like features. Immunoelectron microscopy revealed coexpression of cytokeratin 7 and albumin by SEC.

CONCLUSIONS

SEC with ultrastructural and immunophenotypic features exhibited by oval cells, i.e., hepatic stem-like cells, are found in hepatoblastoma. Their numbers vary with the differing degrees of differentiation seen in the various subtypes. The findings further support the hypothesis that hepatoblastoma is derived from a pluripotent stem cell.

Expression of the endothelial markers PECAM-1, vWf, and CD34 in vivo and in vitro

EC culture models are essential to study pathological alterations of endothelial cells (ECs) in pulmonary vascular diseases under standardized conditions. Nevertheless, little is known about the spectrum of alterations of vessel-specific endothelial phenotypes in monolayer cultures. For the comparative study of endothelial markers in vivo and in vitro we investigated immunohistochemically the expression of PECAM-1, vWf, and CD34 by pulmonary ECs in vivo and in stimulated/unstimulated human umbilical vein endothelial cells (HU-VEC) and human pulmonary microvascular endothelial cells (HPMEC). In vivo, vessel type-specific expression patterns were found for vWf and CD34, while PECAM-1 was homogeneously and strongly expressed. While all HUVEC showed a marked vWf staining, about two-thirds of HPMEC exhibited a strong and the rest a moderate vWf staining. In both in vitro models all ECs were clearly PECAM-1-positive. However, only about 20% of the HUVEC and HPMEC were CD34-positive. Our results demonstrate the reduced expression of vessel type-specific endothelial phenotypes by endothelial monolayer cultures, stressing the need to improve culture conditions as well as develop cocultures and three-dimensional culture models. Moreover, the need for endothelial markers specific for single microvascular type ECs becomes obvious in order to establish cultures consisting of only one microvascular ECs subpopulation.

Neoangiogenesis and sinusoidal "capillarization" in dysplastic nodules of the liver

The blood supply of hepatocellular carcinoma (HCC) is primarily arterial. Recent studies reported differences of vascular, especially arterial, supply among low- and high-grade dysplastic nodules and HCC. We assessed arterialization using monoclonal antibody specific for smooth muscle actin as well as simultaneous changes in sinusoidal capillarization in cirrhotic nodules, dysplastic nodules, and HCC. We immunohistochemically stained 56 cirrhotic nodules, 20 low-grade dysplastic nodules, 27 high-grade dysplastic nodules, and 20 HCCs for alpha smooth muscle actin (to identify unpaired arteries (i.e., arteries not accompanied by bile ducts) and CD34 (indicating sinusoidal capillarization). Distribution and number of unpaired arteries and distribution of sinusoidal capillarization were graded semiquantitatively. Unpaired arteries were rare in cirrhotic nodules, significantly more common in dysplastic nodules of both types (p < 0.00001), and most common in HCC. Sinusoidal capillarization was least common in cirrhotic nodules, significantly more common in dysplastic nodules (p < 0.0035), and most common in HCC. No topographic relationship between unpaired arteries and sinusoidal capillarization was identified. These findings showed that (1) distributions of sinusoidal capillarization and unpaired arteries in dysplastic nodules are intermediate between those in cirrhotic nodules and HCC, supporting dysplastic nodules as premalignant lesions; (2) unpaired arteries are histologically useful for distinguishing dysplastic nodules from large cirrhotic nodules; and (3) areas of sinusoidal capillarization within dysplastic nodules are unrelated to location of arterialization.

Blood cyst of the pulmonary valve in an adult: report of a case and review of the literature

We report a case of a blood cyst originating from the pulmonary valve cusp of a 43-year-old Japanese woman with pulmonary stenosis. Cineangiography revealed a pedunculated tumor on the arterial surface of the pulmonary valve. It was successfully removed by a transpulmonary artery approach. The cyst contained old blood and calcified thrombi, and its wall consisted of collagenous fibrous tissue. Immunohistochemically, a monolayer of flat cells lining the cyst was confirmed as endothelium using antibodies to von Willebrand factor and CD34, as well as UEA-I lectin. To the best of our knowledge, blood cysts of the pulmonary valve are rare and only 10 such cases have been reported, including six pediatric cases. This case is the oldest and fifth adult patient with a blood cyst found on the pulmonary valve. A possible histogenesis is discussed.