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Figures
- Fig. 1.
MMH-D3 cells display a polarized phenotype and respond to the growth inhibitory function of TGF-β1. (A) Phase contrast and confocal immunofluorescence microscopy of parental MMH-D3 cells stained with the adherens junction markers E-cadherin and β-catenin and the tight junction marker ZO-1. (B) Proliferation kinetics of MMH-D3 cells (circles) versus MMH-D3 supplemented with 5 ng/ml TGF-β1 (squares). (C) Flow cytometry determining the cell cycle distribution of MMH-D3 cells versus MMH-D3 at day 5 of TGF-β1 (5 ng/ml) treatment.
- Fig. 3.
Cell cycle progression of MMH cell types and expression of marker proteins. (A) Proliferation kinetics of epithelial (MMH-D3, circles; MMH-R, squares) versus fibroblastoid MMH-RT cells (triangles). (B) Protein abundance of representative components participating in intercellular communication in epithelial and fibroblastoid cells. Besides the exogenous expression of Ha-Ras in epithelial MMH-R and fibroblastoid MMH-RT cells, the downregulation and loss of respective markers is indicated in fibroblastoid cells by immunoblotting.
- Fig. 2.
TGF-β1 triggers an epithelial to fibroblastoid conversion of MMH-R cells expressing constitutive active Ha-Ras. Left panel (—TGF-β1): MMH-R cells show a polarized epithelial phenotype as analyzed by phase contrast and confocal immunofluorescence microscopy. Right panel (+TGF-β1): Epithelial MMH-R cells treated with 5 ng/ml TGF-β1 undergo a conversion to a spindle-shaped fibroblastoid phenotype. The resulting depolarized MMH-RT cell type was processed for microscopical inspection. Exceptionally, cells were stained for Smad2 30 minutes after TGF-β1 induction. Insets in panels of undetectable E-cadherin and desmoplakin staining indicate the presence of GFP-positive cells.
- Table 1.
Tumorigenic features of epithelial and fibroblastoid cell types
MMH-D3 MMH-R MMH-RT Phenotype in culture Epithelial Epithelial Fibroblastoid Transepithelial resistance a +++ ++ - Efficiency of colony formation <1×10-3 0.2 0.22 Spreading of colonies b - - +++ Tumor induction in vivo c - 11-12 days 6-7 days Vascularization of tumors d - +/- +++ Phenotype ex-tumor - Fibroblastoid Fibroblastoid Invasive growth e - +/- +++ -
↵ a (+++) >200 Ω×cm2, (++) 150-200Ω× cm2, (-) < 20 Ω×cm2.
-
↵ b (-) no and (+++) vigorous spreading of colonies formed in soft agar ( Fig. 4A).
-
↵ c as monitored by initial tumor palpation after subcutaneous injection into SCID/BALB/c mice.
-
↵ d (+/-) a small and (+++) a high proportion of endothelial cells in the respective tumor tissue ( Fig. 4C).
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↵ e (+/-) a small and (+++) a high number of cells migrate through Matrigel invasion chambers ( Fig. 4E).
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- Fig. 4.
Malignant transformation of epithelial MMH-R and fibroblastoid MMH-RT cells analyzed in vitro and in vivo. (A) Phase contrast images depicting the typical colonies formed in vitro by anchorage-independent growth of MMH-R and MMH-RT cells in soft agar. (B) Kinetics of tumor formation in vivo after subcutaneous injection of MMH-R (circles) and MMH-RT cells (squares) into immunocompromized SCID/BALB/c recipient mice. (C) Visualization of endothelial cells in histological sections of tumors by immunological staining with anti-von Willebrand Factor. Insets represent lower magnifications (10×) of histological sections. (D) Dedifferentiation of epithelial MMH-R and fibroblastoid MMH-RT cells after tumor formation in vivo. Histological sections of tumors give rise to poorly differentiated cell carcinomas as shown by immunological staining with ZO-1. The cytoplasmic distribution of ZO-1 appears to be very weak in vascularized MMH-RT-derived tumors, and cell boundary staining is exclusively displayed by endothelial cells (white arrow). (E) Assessment of invasive properties in vitro. The ability of epithelial MMH-R and fibroblastoid MMH-RT cells to migrate through Matrigel matrices as reconstituted basement membranes is shown. Invaded cells on lower surfaces of membranes were visualized by immunofluorescence microscopy of GFP-positive MMH-R and MMH-RT cells.
- Fig. 5.
Typical hepatocellular-derived cell structures in collagen gels. (A) A phase contrast image of epithelial MMH-R cells generating lumen-forming structures. (B) Treatment of epithelial MMH-R cells with exogenous TGF-β1 (5 ng/ml) resulted in the formation of disordered branching cord-like structures.
- Fig. 6.
Molecular characteristics of epithelial MMH-R versus established fibroblastoid MMH-RT cells. (A) TGF-β1 production of epithelial and fibroblastoid cell types. The amount of latent TGF-β1 secretion into the medium was determined by ELISA. (B) Semi-quantitative RT-PCR determining the selective decrease (left panel) and increase (right panel) of mRNA abundance in epithelial versus fibroblastoid cells. All samples contained equal amounts of cDNA. As a control, rhoA mRNA expression remained unaffected (right panel). Lane 1, epithelial MMH-R cells; lane 2, fibroblastoid MMH-RT cells.
- Fig. 7.
Reversion of fibroblastoid MMH-RT cells to an epithelium-like phenotype. (A) Phase contrast microscopy of MMH-RT cells (control) grown on tissue culture plates and either treated with 30 μM UO126 or 5 μM LY294.002 for 24 hours. (B) Confocal immunofluorescence microscopy of MMH-RT cells treated with 5 μM LY294.002 for 24 hours. (C) Expression of E-cadherin and MMP-9 as determined by immunoblotting. Staining of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is shown as a loading control. Lane 1, fibroblastoid MMH-RT cells; lanes 2 and 3, MMH-RT cells treated with 5 μM LY294.002 for 24 and 72 hours, respectively; lane 4, epithelial MMH-R cells.
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