XB-ART-51977Cancer Sci June 1, 2016; 107 (6): 803-11.
Identification of anti-cancer chemical compounds using Xenopus embryos.
Cancer tissues have biological characteristics similar to those observed in embryos during development. Many types of cancer cells acquire pro-invasive ability through epithelial-mesenchymal transition (EMT). Similar processes (gastrulation and migration of cranial neural crest cells [CNCC]) are observed in the early stages of embryonic development in Xenopus during which cells that originate from epithelial sheets through EMT migrate to their final destinations. The present study examined Xenopus embryonic tissues to identify anti-cancer compounds that prevent cancer invasion. From the initial test of known anti-cancer drugs, AMD3100 (an inhibitor of CXCR4) and paclitaxel (a cytoskeletal drug targeting microtubules) effectively prevented migration during gastrulation or CNCC development. Blind-screening of 100 synthesized chemical compounds was performed, and nine candidates that inhibited migration of these embryonic tissues without embryonic lethality were selected. Of these, C-157 (an analog of podophyllotoxin) and D-572 (which is an indole alkaroid) prevented cancer cell invasion through disruption of interphase microtubules. In addition, these compounds affected progression of mitotic phase and induced apoptosis of SAS oral cancer cells. SAS tumors were reduced in size after intratumoral injection of C-157, and peritoneal dissemination of melanoma cells and intracranial invasion of glioma cells were inhibited by C-157 and D-572. When the other analogues of these chemicals were compared, those with subtle effect on embryos were not tumor suppressive. These results suggest that a novel chemical-screening approach based on Xenopus embryos is an effective method for isolating anti-cancer drugs and, in particular, targeting cancer cell invasion and proliferation.
PubMed ID: 27019404
PMC ID: PMC4968590
Article link: Cancer Sci
Genes referenced: abr tspan31 tspo
Disease Ontology terms: cancer
Article Images: [+] show captions
|Figure 1. Screening of chemicals that perturb gastrulation. (a) X‐Gal staining of a normal embryo after injection of nuclear‐localized β‐galactosidase mRNA into dorsal‐vegetal blastomeres at the eight‐cell stage. Cells stained blue are migrating mesodermal cells.44 (b) Vegetal or posterior‐dorsal views of stage 12–12 1/2 normal embryos (end of gastrulation). Arrows indicate blastopores. (d) Experimental sheme. (c, e, f) stage 12 1/2 embryos treated with 0.05% DMSO (control) or test chemicals (50 μM). (g) Stage 14 normal embryos (neurula stage). (h–k) Embryos at stage 14, treated with 0.05% DMSO (control) or test chemicals (50 μM). Bar = 2 mm.|
|Figure 2. Screening of chemicals that perturb migration of cranial neural crest cells (CNCC). (a) Experimental scheme. (b) Migratory CNCC streams at the tailbud craniofacial area (stage 30). The blue region indicates CNCC. Arrows indicate the direction of migration. abr, anterior branchial arch; hy, hyoid segment; m, mandibular segment; Op, optic vesicle; Ot, otic vesicle; pbr, posterior branchial arch. (c, d) Whole‐mount in situ hybridization: FoxD3 is a pre‐migratory NCC marker and Dlx2 is a migratory NCC marker. Mixture of these probes indicates whole NCC. DMSO (0.1%) did not affect migratory patterns, which comprised four streams of cranial NCC. (c) Five chemicals induced severe defects in CNCC migration. (d) Three chemicals had relatively mild effects.|
|Figure 5. Effects of C‐157 and D‐572 on apoptosis and viability of SAS cells. (a, b) Apoptosis and viability of SAS cells after treatment with chemicals. The results from triplicate samples are shown as the means ± SD. (b, right panels) SAS cells were labeled with Hoechst 33342, and treated with chemicals. Arrows indicate representative apoptotic cells containing condensed or fragmented nucleus. (c) Western blot analysis of SAS cell lysates with antibodies against phosphorylated and total Erk and Akt. The intensity of each band was measured by ImageJ software and the relative ratio of phosphorylated‐to‐total Erk or Akt was calculated.|