Adhesion of Platelets to Colon Cancer Cells Is Necessary to Promote Tumor Development in Xenograft, Genetic and Inflammation Models

Platelets represent the linkage between tissue damage and inflammatory response with a putative role in tumorigenesis. Given the importance of the microenvironment in colon cancer development, we elucidated the eventual role of platelets-cancer cells crosstalk in in vivo colon cancer models. To evaluate the involvement of platelets in intestinal tumorigenesis, we first analyzed if the ablation of β-integrin P-selectin that drives platelets-cell adhesion, would contribute to platelets-colon cancer cell interaction and drive cancer progression. In a xenograft tumor model, we observed that when tumors are inoculated with platelets, the ablation of P-selectin significantly reduced tumor growth compared to control platelets. Furthermore, in genetic models, as well as in chronic colitis-associated colorectal carcinogenesis, P-selectin ablated mice displayed a significant reduction in tumor number and size compared to control mice. Taken together, our data highlights the importance of platelets in the tumor microenvironment for intestinal tumorigenesis. These results support the hypothesis that a strategy aimed to inhibit platelets adhesion to tumor cells are able to block tumor growth and could represent a novel therapeutic approach to colon cancer treatment.

The Influence of High-Fat Diet in Early Life on Intestinal Tumorigenesis in APC1638N Mice

Objectives Colorectal cancer (CRC) is one of the most prevalent cancer worldwide. Evidence from epidemiological studies shows that the incidence rate of CRC among elders with age ≥ 50 years is gradually decreased, whereas the rate continuously rise in adults with age < 50 years. Along with the rise of CRC in young adults, a significantly increasing trend in obesity is also observed in youth. The present study aims to investigate how the early-life nutrition influences the intestinal tumorigenesis later in mouse with an age equivalent to an age < 50 years in human. Methods APC1638N mice (4 weeks of age) were fed a low-fat diet (N = 22; LF: 10% kcal from fat) or a high-fat diet (N = 23; HF: 60% kcal from fat) for 8 weeks, which is equivalent to child/adolescent age in humans. After that, all animals were switched to standard chow diet (LabDiet #5P76) and fed for additional 12 weeks before sacrifice. Tumors were examined and the expression tumorigenic Wnt-signaling downstream genes (Cyclin D1, c-Myc and Axin 2) in the intestine were assessed. Results Our results showed that compared to LF group, the body weight of both male and female mice significantly increased after 8-week HF feeding (P < 0.05). After switching to the standard chow diet for further 12 weeks feeding, the increase of body weight in HF group remained, although the degree of magnitude reduced, and a statistical significance only shown in female mice (P < 0.05). There were a higher tumor incidence (P = 0.051) and tumor multiplicity (P < 0.05) in males than female. No interactions between gender and diet were observed. The HF group had a higher tumor incidence (P = 0.088) and tumor size (P < 0.05) when compared to the LF group. The expression of Wnt-signaling downstream gene, c-Myc, was significantly increased in the HF group at 24-week of age (P < 0.01). Conclusions A short term of high-fat diet in early life tends to promote intestinal tumorigenesis in adults as indicated by a mild increase in tumor incidence and a significant increase in tumor size. Funding Sources This project was supported by the US Department of Agriculture Hatch funding (#1013548).

RIPK3 Suppresses the Progression of Spontaneous Intestinal Tumorigenesis

Receptor-interacting protein 3 (RIPK3), a member of the family of serine/threonine protein kinases, emerged as a critical regulator of necroptosis. Downregulated expression of RIPK3 is correlated with poor prognosis in multiple tumor types. Here, we show that RIPK3 is involved in the progression of spontaneous intestinal tumorigenesis. As a clinical correlate, reduced expression of RIPK3 is positively associated with histological grade, lymphatic metastasis and poor prognosis in CRC patients. RIPK3-deficient (Ripk3-/-) mice exhibit increased tumor formation in Apcmin/+ spontaneous intestinal tumorigenesis. Apcmin/+Ripk3-/- tumors promote hyperactivation of IL-6/STAT3 signaling, which exacerbates proliferation and inhibits apoptosis. Blocking IL-6 signaling suppressed tumor formation and reduced STAT3 activation in Apcmin/+Ripk3-/- mice. Thus, our results reveal that RIPK3 is a tumor suppressor in spontaneous intestinal tumorigenesis, and implicate targeting the IL-6/STAT3 signaling axis as a potential therapeutic strategy for intestinal tumor patients with reduced RIPK3.