Tensin4 (TNS4) is upregulated by Wnt signalling in adenomas in multiple intestinal neoplasia (Min) mice

Apc^Min/+ mice are regarded as a standard animal model of colorectal cancer (CRC). Tensin4 (TNS4 or Cten) is a putative oncogene conferring features of stemness and promoting motility. Our objective was to assess TNS4 expression in intestinal adenomas and determine whether TNS4 is upregulated by Wnt signalling. Apc^Min/+ mice (n = 11) were sacrificed at approximately 120 days old at the onset of anaemia signs. Small intestines were harvested, and Swiss roll preparations were tested for TNS4 expression by immunohistochemistry (IHC). Individual polyps were also separately collected (n = 14) and tested for TNS4 mRNA expression and Kras mutation. The relationship between Wnt signalling and TNS4 expression was tested by Western blotting in the human CRC cell line HCT116 after inhibition of β-catenin activity with MSAB or its increase by transfection with a Flag β-catenin expression vector. Overall, 135/148 (91.2%) of the total intestinal polyps were positive for TNS4 expression by IHC, whilst adjacent normal areas were negative. RT-qPCR analysis showed approximately 5-fold upregulation of TNS4 mRNA in the polyps compared to adjacent normal tissue and no Kras mutations were detected. In HCT116, β-catenin inhibition resulted in reduced TNS4 expression, and conversely, β-catenin overexpression resulted in increased TNS4 expression. In conclusion, this is the first report linking aberrant Wnt signalling to upregulation of TNS4 both during initiation of intestinal adenomas in mice and in in vitro models. The exact contribution of TNS4 to adenoma development remains to be investigated, but the Apc^Min/+ mouse represents a good model to study this.

The absence of LPA receptor 2 reduces the tumorigenesis by ApcMin mutation in the intestine

Lysophosphatidic acid (LPA) is a lipid mediator that mediates several effects that promote cancer progress. The LPA receptor type 2 (LPA(2)) expression is often elevated in several types of cancers, including colorectal cancer (CRC). In this study, we investigated the role of LPA(2) in the development of intestinal adenomas by comparing Apc(Min/+) mice with Apc(Min/+)/Lpar2(-/-) mice. There were 50% fewer intestinal adenomas in Apc(Min/+)/Lpar2(-/-) mice than Apc(Min/+) mice. Smaller-size adenomas (<1 mm) were found at higher frequencies in Apc(Min/+)/Lpar2(-/-) mice compared with Apc(Min/+) mice at the two age groups examined. The expression level of LPA(2) correlated with increased size of intestinal adenomas. Reduced tumor multiplicity and size in Apc(Min/+)/Lpar2(-/-) mice correlated with decreased proliferation of intestinal epithelial cells. Apc(Min/+)/Lpar2(-/-) mice showed an increased level of apoptosis, suggesting that LPA(2)-mediated signaling stimulates intestinal tumor development and progress by regulating both cell proliferation and survival. In addition, the expression levels of Krüpple-like factor 5 (KLF5), β-catenin, cyclin D1, c-Myc, and hypoxia-inducible factor-1α (HIF-1α) were significantly altered in Apc(Min/+)/Lpar2(-/-) mice compared with Apc(Min/+) mice. In vitro studies using HCT116 cells showed that LPA induced cyclin D1, c-Myc, and HIF-1α expression, which was attenuated by knockdown of LPA(2). In summary, intestinal tumor initiated by Apc mutations is altered by LPA(2)-mediated signaling, which regulates tumor growth and survival by altering multiple targets.

Cooperative effects of matrix metalloproteinase and cyclooxygenase-2 inhibition on intestinal adenoma reduction

Matrix metalloproteinases (MMPs) and cyclooxygenase-2 (COX-2) are expressed in both sporadic and familial adenomatous colonic polyps and tumours and have been independently shown to play causal roles in intestinal tumour formation in mouse models of colon cancer. The apparent roles of these enzymes in intestinal tumorigenesis led us to examine, in the Min mouse model of colon cancer, if selective COX-2 and MMP inhibitors provide additive or synergistic therapeutic benefits in intestinal tumour prevention. The broad-spectrum MMP inhibitor (A-177430; MMPI) and the selective COX-2 inhibitor (A-285969; COX-2I) both showed dose-dependent inhibition of the number of adenomas in Min mice. Using suboptimal doses, the MMPI reduced tumour multiplicity by 32%, the COX-2I by 48% and, both agents in combination resulted in a 67% decrease compared to control demonstrating a cooperative effect on intestinal tumorigenesis. Apoptosis, proliferation, and angiogenesis were assayed in tumors from each treatment group. These agents in combination allowed for a lowered dosage to be administered to achieve significant biological effects. Clinically, this could potentially reduce side effects associated with currently used MMP and COX-2 inhibitors. Together, these compounds could represent an easily tolerated chemopreventive approach.