Figure 3

Long-term N-RAS^61K activation leads to melanocyte senescence followed by anoikis resistance and tumorigenicity in vivo. (a and b) Macroscopic appearance of subcutaneous tissue 10 weeks after injection of N-RAS^61K cells into nude mice. Where indicated, 2 mg/ml doxycycline (Dox) was added to the drinking water of the mice. (c) Macroscopic view of tumor development after subcutaneous injection of N-RAS^61K -AR cells into nude mice. (d–f) Hematoxylin/eosin stained tissue sections. In (d and e), N-RAS^61K -AR-derived tumors are displayed (d: scale bar, 50 μm; e: scale bar, 20 μm). The arrows in (e) indicate mitotic figures. (f) Lung metastasis in a N-RAS^61K-AR-injected nude mouse. The inlay shows a magnification of the metastasis. Scale bar, 500 μm. (g) Time-dependent development of subcutaneous tumors in N-RAS^61K-AR-injected nude mice. The different colors represent the single tumors from both flanks of each mice. (h) Hoechst and Ki67 staining and (i) Hoechst and P-H3 staining of a tumor section from N-RAS^61K-AR-injected mice visualizing strong mitotic activity throughout the tumor. Scale bars, 100 μm