**1. Introduction**

170 Hepatocellular Carcinoma – Basic Research

[18] Konduri SD, Srivenugopal KS, Yanamandra N*, et al*: Promoter methylation and silencing of

[20] Hube F, Reverdiau P, Iochmann S, Rollin J, Cherpi-Antar C and Gruel Y:

[21] Rollin J, Iochmann S, Blechet C*, et al*: Expression and methylation status of tissue factor pathway inhibitor-2 gene in non-small-cell lung cancer. Br J Cancer 92: 775-783, 2005. [22] Guo H, Lin Y, Zhang H*, et al*: Tissue factor pathway inhibitor-2 was repressed by CpG

[23] Nobeyama Y, Okochi-Takada E, Furuta J*, et al*: Silencing of tissue factor pathway inhibitor-2 gene in malignant melanomas. Int J Cancer 121: 301-307, 2007. [24] Wong CM, Ng YL, Lee JM*, et al*: Tissue factor pathway inhibitor-2 as a frequently silenced tumor suppressor gene in hepatocellular carcinoma. Hepatology 45: 1129-1138, 2007. [25] Kempaiah P, Chand HS and Kisiel W: Identification of a human TFPI-2 splice variant that is upregulated in human tumor tissues. Mol Cancer 6: 20, 2007. [26] Tasiou A, Konduri SD, Yanamandra N*, et al*: A novel role of tissue factor pathway

metalloproteinases in human glioma cells. Oncogene 22: 4509-4516, 2003. [19] Pulukuri SM, Gorantla B and Rao JS: Inhibition of histone deacetylase activity promotes

activator. J Biol Chem 282: 35594-35603, 2007.

cancer cells. BMC Mol Biol 8: 110, 2007.

Metastasis 18: 303-308, 2000.

vitro. Int J Oncol 18: 127-131, 2001.

and in vivo. Gynecol Oncol 83: 325-333, 2001.

meningioma cell line. Int J Oncol 29: 25-32, 2006.

kDa MSPI. Int J Cancer 76: 749-756, 1998.

Invest 107: 1117-1126, 2001.

choriocarcinoma cells. Biol Chem 384: 1029-1034, 2003.

the tissue factor pathway inhibitor-2 (TFPI-2), a gene encoding an inhibitor of matrix

invasion of human cancer cells through activation of urokinase plasminogen

Transcriptional silencing of the TFPI-2 gene by promoter hypermethylation in

hypermethylation through inhibition of KLF6 binding in highly invasive breast

inhibitor-2 in apoptosis of malignant human gliomas. Int J Oncol 19: 591-597, 2001. [27] Konduri SD, Tasiou A, Chandrasekar N, Nicolson GL and Rao JS: Role of tissue factor

pathway inhibitor-2 (TFPI-2) in amelanotic melanoma (C-32) invasion. Clin Exp

pathway inhibitor-2 (TFPI-2), decreases the invasiveness of prostate cancer cells in

2/MSPI decreases the invasive potential of human choriocarcinoma cells in vitro

(rAAV) expressing TFPI-2 inhibits invasion, angiogenesis and tumor growth in a

inhibits invasion and tumor growth in vitro and in vivo in a malignant

invasion are inhibited by the matrix-associated serine protease inhibitor TFPI-2/33

activation by tissue factor pathway inhibitor-2/matrix-associated serine protease

the production of active matrix metalloproteinase-2 and is down-regulated in cells

inhibitor of matrix metalloproteinases with implications for atherosclerosis. J Clin

[28] Konduri SD, Tasiou A, Chandrasekar N and Rao JS: Overexpression of tissue factor

[29] Jin M, Udagawa K, Miyagi E*, et al*: Expression of serine proteinase inhibitor PP5/TFPI-

[30] Yanamandra N, Kondraganti S, Gondi CS*, et al*: Recombinant adeno-associated virus

[31] Kondraganti S, Gondi CS, Gujrati M*, et al*: Restoration of tissue factor pathway inhibitor

[32] Rao CN, Cook B, Liu Y*, et al*: HT-1080 fibrosarcoma cell matrix degradation and

[33] Rao CN, Mohanam S, Puppala A and Rao JS: Regulation of ProMMP-1 and ProMMP-3

[34] Izumi H, Takahashi C, Oh J and Noda M: Tissue factor pathway inhibitor-2 suppresses

[35] Herman MP, Sukhova GK, Kisiel W*, et al*: Tissue factor pathway inhibitor-2 is a novel

human glioblastoma cell line. Int J Cancer 115: 998-1005, 2005.

inhibitor. Biochem Biophys Res Commun 255: 94-98, 1999.

harboring activated ras oncogenes. FEBS Lett 481: 31-36, 2000.

The last four decades witnessed a brilliant career of proteoglycans (PGs). Once regarded as mere space-fillers or passive structural components of matrices and charge-selective barriers, these fascinating molecules have been increasingly acknowledged as key players in cell-cell and cell-matrix communication, and have become recognized as modulators of most, if not all, aspects of cell behavior including survival, proliferation, and migration. Simultaneously, the range of disease processes with known involvement of PGs has steadily expanded, now covering areas as diverse as host-pathogen interactions, regulation of pathologic fibrogenesis, and tumor progression. Characteristic alterations of PGs in various human malignant tumors, including HCC, were first described more than 20 years ago (for an early review, see Tímár & Kovalszky, 1995).

PGs, glycanated proteins with extensive posttranslational modifications, consist of a protein core and one or more long, linear, sulfated polysaccharide chains, called glycosaminoglycans (GAGs). GAGs are ligated to the protein core at specific serine, threonine, or asparagine residues, although the exact signal sequences that designate the position of attachment are mostly unknown. The multifunctionality of PGs arises from their inherently complex structure: some functions are assigned to the core protein, while others are fulfilled by the GAG chains.

The synthesis of each GAG chain (recently reviewed by Ly et al., 2010) is introduced by the attachment of a short linkage region to Ser in the case of heparan sulfate (HS)/heparin and chondroitin sulfate/dermatan sulfate (CS/DS), and either Asn or Ser/Thr in the case of keratan sulfate (KS) type I and type II, respectively. During the elongation phase of GAG synthesis, acetylated hexosamine and hexuronic acid or galactose residues are added in an alternating fashion to the growing polysaccharide chain. GAGs are classified by their disaccharide composition: the dimeric building block is N-acetyl-glucosamine / glucoronic acid in HS and heparin; N-acetyl-galactosamine / glucoronic acid in CS and DS; and Nacetlyl-glucosamine / galactose in KS. Completed GAG chains then undergo various chemical modifications including *N*-deacetylation, *N*- and *O*-sulfation, and epimerization of the hexuronic acid. Heparin, for example, differs from HS in the extent of sulfation (heparin is sulfated uniformly and nearly exhaustively, whereas HS is sulfated only partially and in a

Proteoglycans in Chronic Liver Disease and Hepatocellular Carcinoma: An Update 173

patterned manner); and DS differs from CS in the degree of uronic acid epimerization (0% in CS vs. 1-100% in DS.) The extent and pattern of modifications not only vary between different GAGs and PGs, but also depend on the type and actual state of a cell, which contributes a great deal to the biological diversity of PGs. If this were still not enough of versatility, PGs may undergo further editing once they are in place: in the matrix or on the cell surface, they may be subject to the action of endoglycosidases that cleave the GAG chain, proteases that cut the protein core, and endosulfatases capable of removing sulfate groups from internal sugar residues.

Historically, PGs were sorted by the type of their GAG chain into one of the categories HSPG, CS/DSPG, or KSPG. Later, however, the discovery that several PGs carry more than one type of GAG (i.e., syndecans and betaglycan carry both HS and CS; aggrecan carries both CS and KS II) prompted a new classification based on structure and tissue localization. In this revised system, each PG belongs to one of three major families: 1) small leucine-rich proteoglycans or SLRPs; 2) modular PGs, further divided into a) hyalectans or hyaluronan-binding PGs and b) non-hyaluronan-binding PGs of the basement membrane; and 3) cell surface PGs. Nevertheless, both the old and new classifications fall short of being perfect; neither is free of overlaps, and neither can properly accommodate, for example, serglycin or endocan. In this review, we shall follow a sort of "hybrid" classification that fits best for our purposes.

A complete listing of all currently known PGs seems unnecessary here (for a comprehensive review, the Reader is referred to Esko et al., 2009); this paper is restricted in scope to PGs present in the healthy or diseased liver, and will concentrate on those involved in, or affected by, chronic liver disease and hepatocarcinogenesis. Also, with a focus on human disease, PGs reported to be present in the liver of experimental animals but not of humans will be omitted.
