Expression of a Secretory Protein C1qTNF6, a C1qTNF Family Member, in Hepatocellular Carcinoma

Abstract

Background: Recent studies have revealed that the adiponectin-associated protein belonging to the C1qTNF family mediates various biological processes. However, the pathobiological property of C1qTNF6 in carcinogenesis remains unclear. Here, we investigated the expression status of C1qTNF6 in human hepatocellular carcinomas and subsequently attempted to determine the role of C1qTNF6 in tumor neovascularization. Methods: Immunohistochemical staining was performed to evaluate the expression of C1qTNF6 in hepatocellular carcinoma tissue specimens. Various eukaryotic recombinant C1qTNF6 proteins were prepared to ask whether C1qTNF6 could activate Akt pathway in human liver sinusoidal microvascular endothelial cells. Xenograft assay was carried out to know the effect of C1qTNF6 on tumor neovascularization. Results: C1qTNF6 was not immunohistochemically detected in any non-cancerous liver tissues but was detected in 21 of 30 hepatocellular carcinoma tissue specimens. C1qTNF6 was not uniformly distributed but rather focally localized in hepatocellular carcinoma cells. Interestingly, it was also localized on the tumor endothelial cells, which were in close proximity of C1qTNF6-expressing hepatocellular carcinoma cells. Eukaryotic recombinant C1qTNF6 increased the level of active phosphorylated Akt molecules in cultured vascular endothelial cells via its C-terminal C1q domain. In the xenograft assay, enforced expression of C1qTNF6 markedly reduced the central hypovascular necrosis areas of the transplanted HepG2 hepatocellular carcinoma cells. Conclusion: These results indicate that C1qTNF6 is overexpressed and possibly contributes to tumor angiogenesis by activating the Akt pathway in many hepatocellular carcinomas.

Pathobiological properties of the ubiquitin ligase Nedd4L in melanoma

“…The detailed procedure of the xenograft assay is described previously (Takeuchi et al . ,b). The length and width of the tumours were measured using a caliper with a precision of 1.0 mm.…”

“…For stable expression of Nedd4L in A2058 cells, a previously described Nedd4L‐expression vector (Takeuchi et al . ,b) was modified to express the product of the neomycin‐resistant gene and transfected into cells using N ‐[1‐(2,3‐dioleoyloxy) propyl]‐ N , N , N ‐trimethylammonium methylsulphate (DOTAP) transfection reagents (Boehringer Mannheim, Indianapolis, IN, USA) according to the manufacturer's protocol. Briefly, A2058 cells were seeded at approximately 50% confluency in 10‐cm culture dishes.…”

C1QTNF6 is overexpressed in gastric carcinoma and contributes to the proliferation and migration of gastric carcinoma cells

“…An immunohistochemistry assay indicated that c1QTNF6 is mainly localized in hepatocellular carcinoma cells and endothelial cells in tumor tissues. High expression of c1QTNF6 was revealed to activate the Akt signaling pathway, increase tumor angiogenesis and reduce the necrosis of HepG2 cells (12). c1QTNF6-interference was revealed to inhibit the Erk1/2 signaling pathway in 3T3-L1 adipocytes (13).…”

Knockdown of CTRP6 inhibits adipogenesis via lipogenic marker genes and Erk1/2 signalling pathway

“…C1qTNF-related protein-6 (CTRP6) is also a C1qTNF family member that consists of a signal peptide, a short variable region, a collagen-like region, and a C-terminal globular domain, and is thought to play a role in fatty acid metabolism (Kishore et al, 2004), hepatocellular carcinoma (Takeuchi et al, 2011), and immune response . A recent study provides evidence that CTRP6 was found in serum and its expression in fat tissues was enhanced in obese, ob/ob and adiponectin null-mice.…”