Abstract
Metastasis of cancer cells is multi-step process and dissemination is an initial step. Here we report a tamoxifen-controllable Twist1a-ERT2 transgenic zebrafish line as a new animal model for metastasis research, and demonstrate that this model can serve as a novel platform for discovery of antimetastasis drugs targeting metastatic dissemination of cancer cells. By crossing Twist1a-ERT2 with xmrk (a homolog of hyperactive form of EGFR) transgenic zebrafish, which develops hepatocellular carcinoma, approximately 80% of the double transgenic zebrafish showed spontaneous cell dissemination of mCherry-labeled hepatocytes from the liver to the entire abdomen region and the tail region. The dissemination is accomplished in 5 days through induction of an epithelial-to-mesenchymal transition. Using this model, we conducted in vivo drug screening and identified three hit drugs. One of them, adrenosterone, an inhibitor for hydroxysteroid (11-beta) dehydrogenase 1 (HSD11β1), has a suppressor effect on cell dissemination in this model. Pharmacologic and genetic inhibition of HSD11β1 suppressed metastatic dissemination of highly metastatic human cell lines in a zebrafish xenotransplantation model. Through downregulation of Snail and Slug, adrenosterone-treated cells recovered expression of E-cadherin and other epithelial markers and lost partial expression of mesenchymal markers compared with vehicle-treated cells. Taken together, our model offers a useful platform for the discovery of antimetastasis drugs targeting metastatic dissemination of cancer cells. IMPLICATIONS: This study describes a transgenic zebrafish model for liver tumor metastasis and it has been successfully used for identification of some drugs to inhibit metastatic dissemination of human cancer cells.
Highlights
Overt metastases, the end result of malignant alteration of cancer cells, are responsible for approximately 90% of cancer-associated mortality
Twist1a was selected as the metastasis-inducible transgene in the zebrafish model based on the following two criteria: (i) loss of function of Twist1a interfered with metastatic potential of highly metastatic cancer cells in in vivo experiments using mouse metastasis models, and (ii) in clinical studies, elevated expression of Twist1a was observed in metastasized cancer cells in patients suffering from cancer [11, 12]
We examined whether Twist1a-ERT2 activation through tamoxifen (4-OHT) treatment could induce epithelialto-mesenchymal transition (EMT) in the liver of the fish through Western blot analysis
Summary
The end result of malignant alteration of cancer cells, are responsible for approximately 90% of cancer-associated mortality. Metastatic dissemination of cancer cells was traditionally viewed as a late stage event of cancer progression [3]. This paradigm has been challenged by recent studies, in which mammary epithelial cells disseminated systemically from early neoplastic lesions of Her and PyMT transgenic mice and from ductal carcinoma in situ in patients with breast cancer [4, 5]. Molecular mechanisms that promote dissemination involve the breakdown of local basement membrane, loss. Note: Supplementary data for this article are available at Molecular Cancer Research Online (http://mcr.aacrjournals.org/)
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