Expression of the Wnt target gene phospholipase D1 (PLD1) is up-regulated in various carcinomas, including colorectal cancer (CRC). However, the mechanistic significance of its elevated expression in intestinal tumorigenesis remains unknown. In this study, we show that genetic and pharmacological targeting of PLD1 disrupts spontaneous and colitis-associated intestinal tumorigenesis in ApcMin/+ and azoxymethane/dextran sodium sulfate mice models. Intestinal epithelial cell-specific PLD1 overexpression in ApcMin/+ mice accelerated tumorigenesis with increased proliferation and nuclear β-catenin levels compared with ApcMin/+ mice. Moreover, PLD1 inactivation suppressed the self-renewal capacity of colon cancer-initiating cells (CC-ICs) by decreasing expression of β-catenin via E2F1-induced microRNA (miR)-4496 up-regulation. Ultimately, low expression of PLD1 coupled with a low level of CC-IC markers was predictive of a good prognosis in CRC patients, suggesting in vivo relevance. Collectively, our data reveal that PLD1 has a crucial role in intestinal tumorigenesis via its modulation of the E2F1-miR-4496-β-catenin signaling pathway. Modulation of PLD1 expression and activity represents a promising therapeutic strategy for the treatment of intestinal tumorigenesis.
Bibliographical noteFunding Information:
This study was supported by a National Research Foundation of Korea grant funded by the Korean government (MEST; 2012002009), a Translational Research Center for Protein Function Control grant (National Science Foundation 2009-0083522), and a National R&D Program for Cancer Control grant from the Ministry for Health, Welfare, and Family Affairs (Republic of Korea; 0920050). The authors declare no competing financial interests.
Human primary tumor samples and tissue microarray. 55 human colon tumors and adjacent normal tissues for q-RT-PCR analysis were obtained from Pusan National University Hospital, a member of the National Biobank of Korea, which is supported by the Ministry of Health and Welfare. All samples derived from the National Biobank of Korea were obtained with informed consent under institutional review board–approved protocols. For IHC analysis, tissue microarray slides were purchased from SuperBioChips and US-Biomax. Each array includes >174 cases of normal, reactive, premalignant, and malignant tissues of the colon (various grades and stages). Overall survival was calculated from the date of treatment start to the date of death or date of sacrifice. Survival curves were constructed using Kaplan-Meier methodology. Log-rank tests were used to assess differences in tumor characteristics.
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All Science Journal Classification (ASJC) codes
- Immunology and Allergy