Antioxidants Promote Intestinal Tumor Progression in Mice.

Dietary antioxidants and supplements are widely used to protect against cancer, even though it is now clear that antioxidants can promote tumor progression by helping cancer cells to overcome barriers of oxidative stress. Although recent studies have, in great detail, explored the role of antioxidants in lung and skin tumors driven by RAS and RAF mutations, little is known about the impact of antioxidant supplementation on other cancers, including Wnt-driven tumors originating from the gut. Here, we show that supplementation with the antioxidants N-acetylcysteine (NAC) and vitamin E promotes intestinal tumor progression in the ApcMin mouse model for familial adenomatous polyposis, a hereditary form of colorectal cancer, driven by Wnt signaling. Both antioxidants increased tumor size in early neoplasias and tumor grades in more advanced lesions without any impact on tumor initiation. Importantly, NAC treatment accelerated tumor progression at plasma concentrations comparable to those obtained in human subjects after prescription doses of the drug. These results demonstrate that antioxidants play an important role in the progression of intestinal tumors, which may have implications for patients with or predisposed to colorectal cancer.

Genomic profiling of the transcription factor Zfp148 and its impact on the p53 pathway.

Recent data suggest that the transcription factor Zfp148 represses activation of the tumor suppressor p53 in mice and that therapeutic targeting of the human orthologue ZNF148 could activate the p53 pathway without causing detrimental side effects. We have previously shown that Zfp148 deficiency promotes p53-dependent proliferation arrest of mouse embryonic fibroblasts (MEFs), but the underlying mechanism is not clear. Here, we showed that Zfp148 deficiency downregulated cell cycle genes in MEFs in a p53-dependent manner. Proliferation arrest of Zfp148-deficient cells required increased expression of ARF, a potent activator of the p53 pathway. Chromatin immunoprecipitation showed that Zfp148 bound to the ARF promoter, suggesting that Zfp148 represses ARF transcription. However, Zfp148 preferentially bound to promoters of other transcription factors, indicating that deletion of Zfp148 may have pleiotropic effects that activate ARF and p53 indirectly. In line with this, we found no evidence of genetic interaction between TP53 and ZNF148 in CRISPR and siRNA screen data from hundreds of human cancer cell lines. We conclude that Zfp148 deficiency, by increasing ARF transcription, downregulates cell cycle genes and cell proliferation in a p53-dependent manner. However, the lack of genetic interaction between ZNF148 and TP53 in human cancer cells suggests that therapeutic targeting of ZNF148 may not increase p53 activity in humans.

Increased Intimal Hyperplasia After Vascular Injury in Male Androgen Receptor-Deficient Mice.

Intimal hyperplasia is a vascular pathological process involved in the pathogenesis of atherosclerosis. Data suggest that T, the most important sex steroid hormone in males, protects men from atherosclerotic cardiovascular disease. T mainly acts via the androgen receptor (AR), and in this study we evaluated formation of intimal hyperplasia in male AR knockout (ARKO) mice using a vascular injury model. Two weeks after ligation of the carotid artery, male ARKO mice showed increased intimal area and intimal thickness compared with controls. After endothelial denudation by an in vivo scraping injury, there was no difference in the reendothelialization in ARKO compared with control mice. Ex vivo, we observed increased outgrowth of vascular smooth muscle cells from ARKO compared with control aortic tissue explants; the number of outgrown cells was almost doubled in ARKO. In vitro, stimulation of human aortic vascular smooth muscle cells with a physiological T concentration inhibited both migration and proliferation of the cells. Analyzing the expression of central regulators of cell proliferation and migration, we found that mRNA and protein levels of p27 were lower in uninjured arteries from ARKO mice and that T replacement to castrated male mice increased p27 mRNA in an AR-dependent manner. In conclusion, AR deficiency in male mice increases intimal hyperplasia in response to vascular injury, potentially related to the effects of androgens/AR to inhibit proliferation and migration of smooth muscle cells.

Targeting Zfp148 activates p53 and reduces tumor initiation in the gut.

The transcription factor Zinc finger protein 148 (Zfp148, ZBP-89, BFCOL, BERF1, htß) interacts physically with the tumor suppressor p53, but the significance of this interaction is not known. We recently showed that knockout of Zfp148 in mice leads to ectopic activation of p53 in some tissues and cultured fibroblasts, suggesting that Zfp148 represses p53 activity. Here we hypothesize that targeting Zfp148 would unleash p53 activity and protect against cancer development, and test this idea in the APCMin/+ mouse model of intestinal adenomas. Loss of one copy of Zfp148 markedly reduced tumor numbers and tumor-associated intestinal bleedings, and improved survival. Furthermore, after activation of ß-catenin-the initiating event in colorectal cancer-Zfp148 deficiency activated p53 and induced apoptosis in intestinal explants of APCMin/+ mice. The anti-tumor effect of targeting Zfp148 depended on p53, as Zfp148 deficiency did not affect tumor numbers in APCMin/+ mice lacking one or both copies of Trp53. The results suggest that Zfp148 controls the fate of newly transformed intestinal tumor cells by repressing p53 and that targeting Zfp148 might be useful in the treatment of colorectal cancer.