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Comparison of Endothelial Cell Proliferation in Normal Liver and Adipose Tissue in B6C3F1 Mice, F344 Rats, and HumansDepartment of Pathology and Microbiology and the UNMC/Eppley Cancer Center, University of Nebraska Medical Center, 983135 Nebraska Medical Center, Omaha, NE 68198-3135 Correspondence: Address correspondence to: Samuel M Cohen, University of Nebraska, Medical Center, 983135 Nebraska Medical Center, Omaha, NE 68198-3135; e-mail:scohen{at}unmc.edu
Peroxisome proliferator-activated receptor gamma (PPAR ) and dual PPAR and agonists have been developed for use in the treatment of diabetes and hyperlipidemias. Vascular tumors were increased in mice treated with some PPAR agonists, but not in rats. Spontaneous hemangiosarcomas are common in several strains of mice, uncommon in rats, and rarely occur in humans. The objective of this study was to determine the endothelial cell proliferation rate in liver and adipose tissue of B6C3F1 mice, F344 rats, and humans to aid in investigations of the genesis and development of hemangiosarcoma formation, and to determine the relevance of the increased endothelial cell proliferation rate in drug-treated rodents in assessing the risk of these drugs in humans. We determined the endothelial cell labeling index (LI) in untreated mice, rats, and humans, in normal liver, brown fat (rats and mice only) and white fat by dual immunohistochemistry of CD31 and Ki-67. The LI, highest in mice and lowest in humans, was statistically significantly greater in the mouse compared to the human and rat. The increased rate of spontaneous or PPAR agonist-induced hemangiosarcoma formation in mice may be related to the higher background endothelial cell proliferation rate compared to rats and humans.
Key Words: Endothelial cell proliferation PPAR Abbreviations: PPAR
Hemangiosarcomas (angiosarcomas) are rare, highly malignant tumors with a generally poor prognosis in humans (Fletcher et al., 1991; Mark et al., 1996), accounting for less than 1% of all sarcomas (Enzinger and Weiss, 1995). They arise from the endothelial cells of small blood vessels and commonly occur in the skin, soft tissue and liver in humans (Maddox et al., 1981; Fineberg et al., 1994; Neshiwat et al., 1992; Smith et al., 1985). In contrast, hemangiosarcomas occur spontaneously at relatively high rates in many strains of mice, particularly in lifetime (2 year) studies. The incidence of spontaneous hemangiosarcomas in all organs of B6C3F1 mice is 5.3% in the male and 2.8% in the female (ranges of 0–14% and 0–16%, respectively) with a high incidence in all organs, but especially liver, spleen, and bone marrow (National Toxicology Program, 2000). In the liver of B6C3F1 mice, the mean incidence of spontaneous hemangiosarcomas is 2.48% in the male and 0.80% in the female, with ranges of 0–8% and 0–4%, respectively. In rats, vascular tumors, especially sarcomas, are much less common, but occur at rates considerably higher than in humans (Herman et al., 2002). The incidence of hemangiosarcomas in all organs of the F344 rat is 0.40% in the male and 0.28% in the female (ranges of 0–2% and 0–2%, respectively). In the liver of F344 rats, the incidence of spontaneous hemangiosarcomas is 0.07% in the male and 0.00% in the female (National Toxicology Program, 2000).
When troglitazone, a peroxisome proliferator-activated receptor gamma (PPAR Little is known about the mechanism of induction of hemangiosarcomas except when induced by genotoxic agents like vinyl chloride and thorotrast. Many of the hemangiosarcomas produced by various chemicals in mice occur at the sites with high spontaneous rates of endothelial cell proliferation, such as liver, spleen, and bone marrow. For PPAR agonists, a significant incidence frequently occurs in the subcutaneous adipose tissue. Since the mechanism of hemangiosarcoma induction in mice by nongenotoxic chemicals is not well understood, assessing the risk to humans is difficult. To begin, there is a paucity of comparative data between species. It is important for investigating the genesis and development of the hemangiosarcomas that comparative data regarding proliferation of endothelial cells in the different species be developed. The objective of this study was to determine the endothelial cell proliferation rate in normal liver and adipose tissue of untreated B6C3F1 mice, F344 rats, and humans to aid in the investigation of the genesis and development of hemangiosarcomas.
Human Samples Slides of routinely formalin-fixed, paraffin-embedded livers and white fat tissues from 10 female and 10 male humans (different patients for liver and fat), 20–50 years old, were obtained from the surgical pathology files of the Nebraska Medical Center. The protocol was approved by the University of Nebraska Medical Center Institutional Review Board. Liver tissue was obtained from biopsies of donor livers used to assess suitability for transplantation and were histopathologically unremarkable. Fat tissue was obtained from pannus specimens which were histologically normal. Normal pannus tissue was readily available with a proliferation rate similar to the liver, and the proliferation rate in pannus tissue would be expected to be similar to the proliferation rate at other subcutaneous sites.
Test Animals
Histological Examinations
Dual Immunostaining for Ki-67/CD31 on Human Tissues Dual immunostaining of liver and white fat tissues in 10% formalin-fixed specimens was performed for detection of Ki-67 (proliferation marker) and CD31 (endothelial cell marker). The dual immunostain was performed on the Ventana Benchmark instrument (Tucson, AZ). The tissues on slides underwent heat-induced epitope retrieval with CC1 solution (Ventana) for 30 minutes. The first antibody applied was for Ki-67 (Clone MIB-1, DAKO, Carpinteria, CA) diluted 1:40, for 30 minutes. The chromogenic stain was 3,3'-diaminobenzidine tetrahydrochloride (DAB) (Ventana). The second antibody applied was for CD31 (DAKO), diluted 1:100, for 32 minutes. The chromogenic stain was enhanced V red (Ventana).
Immunostaining for CD31 on 10% Formalin-Fixed Rat and Mouse Tissues
Dual Immunostaining for Ki-67/CD31 on Mouse Tissues
Dual Immunostaining for CD31/Ki-67 for Rat Tissues
Statistical Analysis
Labeling Index of Endothelial Cells in Humans, Rats, and Mice We determined the labeling index (LI) in mice, rats and humans of endothelial cells in normal liver, brown fat (rats and mice only) and white fat by dual immunohistochemical staining for Ki-67 and CD31 (Table 1, Figure 1). The LI in the male and female mouse liver was significantly higher (p < 0.01) compared to the LI in the male and female rat and human liver, and the LI in the male and female rat liver was significantly higher (p < 0.05) than the LI in the human liver. The LI in the male and female mouse brown fat was significantly higher (p < 0.01) than the LI in the male and female rat brown fat. The LI in the male mouse white fat was significantly higher (p < 0.01) compared to the LI in the male rat and human white fat. The LI in the female mouse white fat was significantly higher compared to the female rat (p < 0.05) and the female human (p < 0.01). Otherwise, the LI was similar in males and females although the LI in the male mouse tissues was consistently higher than in the female mouse tissues.
A new class of drugs called PPAR and dual PPAR and agonists has been developed for use in the treatment of diabetes and hyperlipidemias (Cantello et al., 1994; Lehman et al., 1995). PPAR is expressed in adipose tissue, endothelial cells, urothelium and intestine (Marx et al., 1999; Yki-Jarvinen., 2004). Vascular tumors were increased in mice treated with some of these drugs. In a 2-year bioassay, troglitazone, a PPAR agonist, caused an increased incidence of hemangiosarcomas of the liver in male and female mice but not in rats (Herman et al., 2002). Rodents treated with these drugs also had increased interscapular brown fat. It has also been reported that the bromodeoxyuridine (BrdU) labeling index of endothelial cells in the brown adipose tissue of PPAR agonist-treated B6C3F1 mice was increased (Breider et al., 1999). Ras mutation and p53 inactivation in B6C3F1 mice did not play a role in vascular tumorigenesis in a long-term study with troglitazone (Duddy et al., 1999a, 1999b). From the viewpoint of our data, the species-specific high incidences of hemangioma and hemangiosarcoma may be the result of increased endothelial cell proliferation on a background of an already high proliferation rate in B6C3F1 mice. The 8-week old rats and mice were in similar growth phases and the background cell proliferation rates in the liver and adipose tissue would be expected to be at adult rates by these ages. The high background proliferation rate of endothelial cells in mice might also be a significant basis for the high rate of spontaneous endothelial cell tumors in mice compared to other species, such as the rat and human. Increased numbers of cell divisions (DNA replications) have been theorized to provide the basis for an increased risk of carcinogenesis based on the spontaneous rates of mutation in somatic cells (Cohen et al., 1990, 1991; Cohen, 2005; Dominick et al., 2006). Platelet endothelial cell adhesion molecule-1 (PECAM-1, CD31) belongs to the immunoglobulin family of cell adhesion molecules (Newman et al., 1990). Anti-CD31 antibody primarily labels endothelial cells, and is useful for the identification of vascular lesions, including heangiosarcomas (Newman et al., 1990; Parums et al., 1990). In addition, anti-CD31 antibody is valuable for determining angiogenesis in several types of tumors (DeYoung et al., 1995; Engel et al., 1996). An anti-human CD31 antibody was used for labeling paraffin-embedded human tissue sections fixed in formalin with heat-induced epitope retrieval (Giatromanolaki et al., 1996). An anti-human CD31 antibody that was cross-reactive with mouse tissue was used in this study (Figure 1C–E), for the dual labeling procedure for paraffin-embedded mouse tissue sections fixed in formalin. Immunohistochemical studies using anti-rat and anti-mouse CD31 antibody are useful for tissues dehydrated with ethanol or in frozen sections (Carrithers et al., 2005; Zacchigna et al., 2005). Anti-rat CD31 antibody (clone number: TLD-3A12) and anti-mouse CD31 antibody (clone number: MEC13.3) may be used for labeling paraffin-embedded mouse tissue sections fixed in formalin with proteinase K for epitope retrieval (Figure 2). We chose Ki-67 as an indicator of cell proliferation so that the same marker could be used for human and rodent tissue. Obviously, BrdU labeling is not possible for examination of human tissues since BrdU cannot be routinely administered to humans. Using Ki-67 and CD31 permitted use of already available normal human tissues.
In conclusion, the increased rate of spontaneous hemangiosarcoma formation in mice may be related to the increased proliferation rate of endothelial cells normally present in this strain of mouse compared to rats and humans. Additional increases in endothelial cell proliferation might explain the sensitivity of mice to hemangiosarcomagenesis by various agents such as PPAR and dual PPAR / agonists.
We gratefully acknowledge the technical expertise of Dr. Dominick DiMaio with development of some of the methodology and the invaluable assistance of David Muirhead in the preparation of this manuscript.
Samuel M. Cohen is the Havlik-Wall Professor of Oncology.
Breider, MA, Gough, AW, Hasking, JR, Sobocinski, G, & de la Iglesia, FA. (1999). Troglitazone-induced heart and adipose tissue cell proliferation in mice. Toxicol Pathol, 27, 545-52 Cantello, BC, Cawthorne, MA, Cottam, GP, Duff, PT, Haigh, D, Hindley, RM, Lister, CA, Smith, SA, & Thurlby, PL. (1994). [[omega-(Heterocyclylamino) alkoxy] benzyl]-2,4-thiazolidinediones as potent antihyperglycemic agents. J Med Chem, 37, 3977-85[CrossRef][Web of Science][Medline] [Order article via Infotrieve] Carrithers, M, Tandon, S, Canosa, S, Michaud, M, Graesser, D, & Madri, J. (2005). Enhanced susceptibility to endotoxic shock and impared STAT3 signaling in CD31-deficient mice. Am J Pathol, 166, 185-96 Cohen, SM. (2005). Effects of PPAR Cohen, SM, & Ellwein, LB. (1990). Cell proliferation in carcinogenesis. Science, 31, 1007-11 Cohen, SM, & Ellwein, LB. (1991). Genetic errors, cell proliferation, and carcinogenesis. Cancer Res, 15, 6493-505 DeYoung, BR, Swanson, PE, Argenyi, ZB, Ritter, JH, Fitsgibbon, JF, Stahl, DJ, Hoover, W, & Wick, MR. (1995). CD31 immunoreactivity in mesenchymal neoplasms of the skin and subcutis: Report of 145 cases and review of putative immunohistologic markers of endothelial differentiation. J Cutan Pathol, 22, 215-22[CrossRef][Web of Science][Medline] [Order article via Infotrieve] Dominick, MA, White, MR, Sanderson, TP, van Vleet, T, Cohen, SM, Arnold, LL, Cano, M, Tannehill-Gregg, S, Moehlenkamp, JD, Waites, CR, & Schilling, BE. (2006). Urothelial carcinogenesis in the urinary bladder of male rats treated with muraglitazar, a PPAR alpha/gamma agonist: Evidence for urolithiasis as the inciting event in the mode of action. Toxicol Pathol, 34, 903-20 Duddy, SK, Gorospe, SM, Bleavins, MR, & de la Iglesia, FA. (1999b). Spontaneous and thiazolidinedione-induced B6C3F1 mouse hemangiosarcomas exhibit low ras oncogene mutation frequencies. Toxicol Appl Pharmacol, 160, 133-40[CrossRef][Web of Science][Medline] [Order article via Infotrieve] Duddy, SK, Parker, RF, Bleavins, MR, Gough, AW, Rowse, PE, Gorospe, S, Dethloff, LA, & de la Iglesia, FA. (1999a). p53 is not inactivated in B6C3F1 mouse vascular tumors arising spontaneously or associated with long-term administration of the thiazolidinedione troglitazone. Toxicol Appl Pharmacol, 156, 106-12[CrossRef][Web of Science][Medline] [Order article via Infotrieve] Giatromanolaki, A, Koukourakis, M, OByme, K, Fox, S, Whitehouse, R, Talbot, DC, Harris, AL, & Gatter, KC. (1996). Prognostic value of angiogenesis in operable non-small cell lung cancer. J Pathol, 179, 80-8[CrossRef][Web of Science][Medline] [Order article via Infotrieve] El Hage, J. (2005). Peroxisome proliferation-activated receptor agonist: carcinogenicity findings and regulatory recommendations. International Atherosclerosis Society Symposium on PPAR: Monte Carlo Engel, CJ, Bennett, ST, Chambers, AF, Doig, GS, Kerkvliet, N, & OMalley, FP. (1996). Tumor angiogenesis predicts recurrence in invasive colorectal cancer when controlled for Dukes staging. Am J Surg Pathol, 20, 1260-5[CrossRef][Web of Science][Medline] [Order article via Infotrieve] Enzinger, F, & Weiss, S. In Weiss, SH, & Goldblum, JR (Eds.). (1995). Soft Tissue Tumors (pp.579-677). St. Louis: Mosby Fineberg, S, & Rosen, PP. (1994). Cutaneous angiosarcoma and atypical vascular lesions of the skin and breast after radiation therapy for breast carcinoma. Am J Clin Pathol, 102, 757-63[Web of Science][Medline] [Order article via Infotrieve] Fletcher, CD, Beham, A, Bekir, S, Clarke, AM, & Marley, NJ. (1991). Epithelioid angiosarcoma of deep soft tissue: a distinctive tumor readily mistaken for an epithelial neoplasm. Am J Surg Pathol, 15, 915-24[Web of Science][Medline] [Order article via Infotrieve] Herman, JR, Dethloff, LA, McGuire, EJ, Parker, RF, Walsh, KM, Gough, AW, Masuda, H, & de la Iglesia, FA. (2002). Rodent carcinogenicity with the thiazolidinedione antidiabetic agent troglitazone. Toxicol Sci, 68, 226-36 Hong, HH, Devereux, TR, Melnick, RL, Moomaw, CR, Boorman, GA, & Sills, RC. (2000). Mutations of ras protooncogenes and p53 tumor suppressor gene in cardiac hemangiosarcomas from B6C3F1 mice exposed to 1,3-butadiene for 2 years. Toxicol Pathol, 28, 529-34 Lehman, JM, Moore, LB, Smith-Oliver, TA, Wilkison, WO, Willson, TM, & Kliewer, SA. (1995). An antidiabetic thiazolidinedione is a high affinity ligand for peroxisome proliferators-activated receptor gamma (PPAR Maddox, JC, & Evans, HL. (1981). Angiosarcoma of skin and soft tissues: a study of forty-four cases. Cancer, 8, 1907-21 Mark, RJ, Poen, JC, Tran, LM, Fu, YS, & Juillard, GF. (1996). Angiosarcoma. A report of 67 patients and review of the literature. Cancer, 77, 2400-6[CrossRef][Web of Science][Medline] [Order article via Infotrieve] Marx, N, Bourcier, T, Sukhova, GK, Libby, P, & Plutzky, J. (1999). PPAR Meis-Kindblom, JM, & Kindblom, LG. (1998). Angiosarcoma of soft tissue: a study of 80 cases. Am J Surg Pathol, 22, 683-97[CrossRef][Web of Science][Medline] [Order article via Infotrieve] National Toxicology Program. (2000). NIEHS Internet Website: http://ntp-server.niehs.nih.gov/. Neshiwat, LF, Friedland, ML, Schorr-Lesnick, B, Feldman, S, Glucksman, WJ, & Russo, RD., Jr. (1992). Hepatic angiosarcoma. Am J Med, 93, 219-22[CrossRef][Web of Science][Medline] [Order article via Infotrieve] Newman, P, Berndt, MC, Gorski, J, White, GC, Lyman, S, Paddock, C, & Muller, WA. (1990). PECAM-1 (CD31) cloning and relation to adhesion molecule of the immunoglobulin gene family. Science, 247, 1219-22 Parums, DV, Cordell, JL, Micklem, K, Heryet, AR, Gatter, KC, & Mason, DY. (1990). JC70: a new monoclonal antibody that detects vascular endothelium associated antigen on routinely processed tissue sections. J Clin Pathol, 43, 752-7 Smith, VC, Eisenberg, BL, & McDonald, EC. (1985). Primary splenic angiosarcoma: case report and literature review. Cancer, 55, 1625-7[CrossRef][Medline] [Order article via Infotrieve] Yki-Jarvinen, H. (2004). Drug therapy, thiazolidinediones. Review Article. New Engl J Med, 351, 1106-18 Zacchigna, S, Papa, G, Antonini, A, Novati, F, Moimas, S, Carrer, A, Arsic, N, Zentilin, L, Visintini, V, Pascone, M, & Giacca, M. (2005). Improved survival of ischemic cutaneous and musculocutaneous flaps after vascular endothelial growth factor gene transfer using adeno-associated virus vectors. Am J Pathol, 167, 981-91
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