Abstract.Little is known about the expression or role of ADAMTS-1, -4 and -5 and their endogenous inhibitor TIMP3 in the liver in physiological and pathological conditions. Their expression was, therefore, investigated in the hepatocellular carcinoma cell lines HepG2 and HuH-7 using qRT-PCR and western blotting, and their cellular localisation by immunocytochemistry. Cytokine treatments were used to assess mRNA and protein modulation. ADAMTS-1, -4, -5 and TIMP3 mRNA and protein were detected in both HepG2 and HuH-7 cells. IL-1β and IL-6 treatments significantly modulated ADAMTS-1 mRNA expression and IL-1β treatment ADAMTS-4 mRNA expression in HepG2 cells. Modulations of mRNA by ≥5-fold did not translate to increased protein expression. This study showed that ADAMTS-1, -4, -5 and TIMP3 were expressed at differential levels in hepatocellular carcinoma cell lines. The pro-inflammatory cytokines IL-1β, TNF-α or IL-6 induced changes in mRNA expression, although these did not translate to the protein level.
IntroductionHepatocellular carcinoma (HCC) is the most common primary malignant tumour occurring in the liver which accounts for 80-90% of all primary liver cancers (1). In many cases, the neoplastic transformation of hepatocytes results from accumulation of genetic changes during enhanced cell proliferation in the injured liver in response to paracrine growth factor and cytokine stimulation (2). HCCs have a considerable capacity for vascular invasion, with metastasis and recurrence being the major factors associated with the poor prognosis of HCC (3).Proteolytic modification of cell surface proteins and extracellular matrix (ECM) plays a pivotal role in cancer development and metastasis. Proteolytic enzymes are involved in several processes, at the cellular and organism level, which are dysregulated in cancer, e.g. cell adhesion and migration, cell invasion and angiogenesis. In particular, they mediate tumour invasion at several stages, e.g. detachment of cells from the primary tumour, crossing vessel walls and extravasation into target organs. This involves attachment of oncogenically transformed cells to the ECM followed by its degradation and movement of invading cells through the damaged ECM (4,5).Expression and activity of several classes of proteolytic enzymes have been shown to be modified in cancer, including recently discovered a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTSs). There are 19 ADAMTSs which can be involved in pathological processes such as ECM breakdown and angiogenesis (6). They consist of several domains: the prodomain, metalloproteinase domain, disintegrin-like domain, cysteine-rich domain, thrombospondin type-I repeats (TSRs) and a spacer domain. Several ADAMTSs also contain an additional unique domain(s). They are synthesised as zymogens and after proteolytic processing at the N-terminus to remove the signal sequence and prodomain, they are secreted from cells. For most ADAMTSs this is an important step in their activation. ADAMTSs may also undergo C-terminal proc...