Article Figures & Data
Figures
- Figure 1.
In vitro correlations with gene expression signatures. M980513 and M000907 proliferative signature melanoma lines, as well as M991121 and M010308 invasive signature melanoma lines, were chosen for this study. A, a gene expression heat map, generated by clustering samples based on the normalized expression of 105 metastatic potential genes (Supplementary Fig. S1), highlights subtype-specific signatures. In vitro growth (B) and motility (C) experiments correlate appropriately with proliferative and invasive signature assignments. Bars, SD.
- Figure 2.
Immunohistochemical marker correlations with gene expression signatures. Immunohistochemical analysis of paraffin-embedded cell lines shows that proliferative and invasive signature lines have differential staining for Mitf (93% and 0%, respectively) and Ki67 antigen (94% and 45%, respectively). See Supplementary Fig. S2 for a higher-resolution image.
- Figure 3.
siRNA knockdown of Mitf protects against TGF-β–mediated growth inhibition. A, siRNA-mediated knockdown of Mitf in a proliferative signature melanoma cell line (M000921) was confirmed by Western blot analysis. B, the ratio of TGF-β–mediated inhibition of growth in cells treated with siRNA targeting Mitf over cells treated with a control siRNA is compared between proliferative (M000921) and invasive (M991121) signature melanoma cell lines. This shows that Mitf knockdown promotes resistance to TGF-β–mediated growth inhibition in a proliferative signature melanoma cell line, whereas identical treatment does not change susceptibility in an invasive signature line. TGF-β treatment of proliferative signature lines (M980513, M000907) results in reduction of Mitf mRNA (C).
- Figure 4.
Xenograft tumor growth. Human melanoma cell lines (M980513, M000907, M991121, M010308) were injected into both flanks of immunocompromised nude mice. Proliferation of melanoma cells led to tumor growth, which was monitored daily. Proliferative melanoma cells (M980513, M000907) rapidly formed tumors, whereas invasive melanoma cells (M991121, M010308) took weeks longer to initiate tumor growth.
- Figure 5.
Immunohistochemistry of melanoma xenograft tumors. Human melanoma cell lines (M980513, M000907, M991121, M010308) were injected into the flanks of immunocompromised nude mice and allowed to grow tumors for a maximum of 75 d. After a tumor had formed, it was removed and subjected to immunohistochemical analysis. A, a day 75 tumor resulting from an invasive signature melanoma (M010308); see Supplementary Fig. S3 for a higher-resolution image. B, Mitf and Ki67 stains of fields 1 and 2. C, a day 22 tumor resulting from a proliferative signature melanoma (M980513); see Supplementary Fig. S4 for a higher-resolution image. D, Mitf and Ki67 stains of fields 3 and 4. Black horizontal bars, 200 μm.
- Figure 6.
An integrated model for gene regulation of melanoma metastatic potential and progression. Early-phase melanoma cells expressing the proliferative signature gene set proliferate to form the primary lesion. Following this, an unknown signal switch, likely brought about by altered microenvironmental conditions (e.g., hypoxia or inflammation), gives rise to cells with a significantly different invasive signature gene set. Invasive signature cells escape and, upon reaching a suitable distal site, revert to the proliferative state and nucleate a new metastasis where the cycle is repeated. Each switch in phenotype (state change) is accompanied by an exchange in expressed gene sets from proliferative to invasive and vice versa.
Additional Files
Supplementary Data, Hoek, et al.
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Volume 68, Issue 3
