Anti-fibrotic properties of an adiponectin paralog protein, C1q/TNF-related protein 6 (CTRP6), in diffuse gastric adenocarcinoma

CTRP6 alleviates endometrial fibrosis by regulating Smad3 pathway in intrauterine adhesion†

Intrauterine adhesion (IUA) is manifestations of endometrial fibrosis and excessive extracellular matrix deposition. C1q/tumor necrosis factor-related protein-6 (CTRP6) is a newly identified adiponectin paralog which has been reported to modulate the fibrosis process of several diseases; however, the endometrial fibrosis function of CTRP6 remains unknown. Our study aimed to assess the role of CTRP6 in endometrial fibrosis and further explore the underlying mechanism. Here, we found that the expression of CTRP6 was downregulated in the endometrial tissues of IUA. In vitro experiments demonstrated the reduced level of CTRP6 in facilitated transforming growth factor-β1 (TGF-β1)-induced human endometrial stromal cells (HESCs). In addition, CTRP6 inhibited the expression of α-smooth muscle actin (α-SMA) and collagen I in TGF-β1-treated HESCs. Mechanistically, CTRP6 activated the AMP-activated protein kinase (AMPK) and protein kinase B (AKT) pathway in HESCs, and AMPK inhibitor (AraA) or PI3K inhibitor (LY294002) pretreatment abolished the protective effect of CTRP6 on TGF-β1-induced fibrosis. CTRP6 markedly decreased TGF-β1-induced Smad3 phosphorylation and nuclear translocation, and AMPK or AKT inhibition reversed these effects. Notably, CTRP6-overexpressing treatment alleviated the fibrosis of endometrium in vivo. Therefore, CTRP6 ameliorates endometrial fibrosis, among which AMPK and AKT are essential for the anti-fibrotic effect of CTRP6 via the Smad3 pathway. Taken together, CTRP6 may be a potential therapeutic target for the treatment of intrauterine adhesion.

Tumor-related factor complement Clq/TNF-related protein 6 affects the development of digestive system tumors through the phosphatidylinositol 3-kinase pathway

In this editorial, we review the work of Razali et al published in World J Gastroenterology, with a particular focus on the effect of rs10889677 variation in the phosphatidylinositol 3-kinase (PI3K) pathway and buparlisib on colitis-associated cancer. The role of PI3K in promoting cancer progression has been widely recognized, as it is involved in regulating the survival, differentiation, and proliferation of cancer cells. The complement Clq/TNF-related protein 6 (CTRP6) is a newer tumor-associated factor. Recent studies have revealed the pro-tumor effect of CTRP6 in gastric cancer, hepatocellular carcinoma, colorectal cancer, and other gastrointestinal tumors through the PI3K pathway. This article attempts to reveal the mechanism through which the CTRP6 affects the development of digestive system tumors through the PI3K pathway by summarizing recent research.

Down regulation of C1q tumor necrosis factor-related protein 6 is associated with increased risk of breast cancer

C1q tumor necrosis factor-related protein 6 (CTRP6), a member of the C1q tumor necrosis factor-related protein (CTRP) family, is reported to be associated with the progression of different malignancies, however, its expression levels and role in breast cancer (BC) are yet unknown. In this study, we investigated the levels of circulating CTRP6 in BC patients and evaluated its role as a potential diagnostic biomarker in BC patients. Then we investigated the effect of recombinant CTRP6 on cellular viability in MCF-7 cells along with its effects on the expression of inflammatory cytokines, interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-α) in addition to the expression of vascular endothelial growth factor (VEGF) as a marker of angiogenesis. Our results showed decreased expression of circulating CTRP6 in BC patients with an inverse correlation between CTRP6 and IL-6, TNF-α and VEGF levels. Besides, Receiver operating characteristic (ROC) curve showed that the assessment of CTRP6 levels could be used to predict BC. Moreover, treatment of MCF-7 cells with recombinant CTRP6 protein reduced cellular viability and decreased IL-6, TNF-α and VEGF expression. In conclusion, these results provide new insights into the role of CTRP6 in BC pathogenesis and suggest its potential use as a novel diagnostic biomarker of BC.

Advances in the functions of CTRP6 in the development and progression of the malignancy

CTRP6, a member of the C1q/TNF-related protein (CTRP) family, has gained increasing scientific interest because of its regulatory role in tumor progression. Previous studies have shown that CTRP6 is closely involved in regulating various pathophysiological processes, including glucose and lipid metabolism, cell proliferation, apoptosis, and inflammation. To date, CTRP6 has been identified as related to eight different malignancies, including lung cancer, oral cancer, gastric cancer, colon cancer, liver cancer, bladder cancer, renal cancer, and ovarian cancer. CTRP6 is reported to be associated with tumor progression by activating a series of related signal networks. This review article mainly discusses the biochemistry and pleiotropic pathophysiological functions of CTRP6 as a new molecular mediator in carcinogenesis, hoping that the information summarized herein could make a modest contribution to the development of novel cancer treatments in the future.

Potential participation of CTRP6, a complement regulator, in the pathology of age related macular degeneration

PURPOSE

To investigate the localized expression of C1q/tumor necrosis factor related protein (CTRP) 6 in human age-related macular degeneration (AMD) retinal tissues.

EXPERIMENTAL STUDY DESIGN

4 AMD and 3 non-AMD whole eyes of Caucasian donors were used. Eyecups were excised at Eye Bank CorneaGen, Inc.

METHODS

To elucidate the effects of CTRP6, C3b was measured by an enzyme-linked immunosorbent-like assay. CFB versus CTRP6 competitive binding assay was applied to clarify the inhibition by CTRP6 of C3bBb complex formation. The cornea, iris, lens, and vitreous were removed and the eyes were cut into a posterior eye-cup including the retina, choroid, and sclera. Six-µm-thick serial sections of frozen samples underwent hematoxylin-eosin (HE) staining and indirect immunohistochemical staining using primary antibodies, anti-CTRP6, -CTRP5, -CTRP10, -Complement factor H (CFH) and -Clusterin (CLU). Results The two in vitro studies confirmed that CTRP6 has an inhibitory effect on alternative pathways of complement (APC) function and that the molecular target of CTRP6 is the inhibition of the formation of C3bBb. Localized expression for CTRP6 and CFH was found in the drusen of the AMD eyes, both associated with APC inhibition, CLU associated with membrane-attack complex (MAC) inhibition, and CTRP5 associated with retinal degeneration.

CONCLUSION

The localized expression of CTRP6 in the drusen of AMD eyes may open a new insight into the possible involvement of APC regulatory factors in the pathogenesis of AMD, together with the known CFH so far analyzed solely as an APC inhibitor.