Progastrin overexpression imparts tumorigenic/metastatic potential to embryonic epithelial cells: phenotypic differences between transformed and non-transformed stem cells

摘要

We recently reported that overexpression of progastrin in embryonic epithelial cells (HEKmGAS-cells) increased proliferation of the cells, compared to that of control HEKC-cells. Here we report the novel finding that tumorigenic and metastatic potential of HEKmGAS cells is also increased significantly, compared to that of HEKC cells. Cell-surface associated annexinA2 (CS-ANXA2) binds progastrin and is over-expressed on cancer-cells, allowing us to successfully use fluorescently-labeled progastrin-peptide for enumerating metastatic lesions of transformed/cancer cells in vivo. Next, we examined the hypothesis that increased tumorigenic/metastatic potential of isogenic HEKmGAS vs HEKC cells maybe due to transformed-phenotype of stem-cells. FACSorting/FACScanning of cells demonstrated significant increases in percent DCLK1/Lgr5 positive stem-cells, co-expressing CD44/CS-ANXA2, in HEKmGAS vs HEKC-cells. Distinct differences were noted in morphology of HEKC vs HEKmGAS spheroidal growths on non-adherent cultures (selective for stem cells). HEKC-spheroids were rounded with distinct perimeters (basement membranes?), while HEKmGAS-spheroids were amorphous, with no perimeters. Relative levels of DCLK1/Lgr5/CD44 and AnnexinA2/β-catenin/pNFκBp65/metalloproteinases were significantly increased in HEKmGAS vs HEKC-cells, growing either as mono-layer cultures, 3D-spheroids (in vitro), or xenografts (in vivo). Interestingly, HEKC-cells enriched for CS-ANXA2, developed amorphous spheroids, while down-regulation of ANXA2 in HEKmGAS-clones, resulted in loss of matrixmetalloproteinases and re-formation of rounded spheroids, suggesting high levels of CS-ANXA2/matrixmetalloproteinases may impact spheroid morphology. Down-regulation of DCLK1 significantly attenuated activation of β-catenin, with loss of proliferation of HEKmGAS and HEKC-cells, suggesting DCLK1 is required for maintaining proliferation of cells.ConclusionsOur results suggest the novel possibility that transformed stem-cells, unlike non-transformed stem-cells, co-express stem-cell-markers DCLK1 and CD44 with CS-ANXA2.