Fig. 2.

Phd2 loss cooperates with BRaf^V600E to induce malignant melanoma in mice. a Treatment scheme. Mice carrying various conditional alleles of BRaf (BRaf^CA) and/or Phd2 (Phd2^lox/lox) were crossed to the Tyr::CreER mice with melanocyte-specific expression of a hormone-dependent form of Cre recombinase (CreERT2). 4-OHT-dependent activation of the CreER recombinase leads to a melanocyte-specific conversion of BRaf^CA→BRaf^V600E and the conversion of the Phd2^lox alleles to Phd2^−/− alleles. b–g Melanoma progression in mice. Tyr::CreER;BRaf^CA;Phd2^lox/lox mice were treated topically with 4-OHT on the ear (b–d) and flank (e–g). 4-OHT-treated mice were killed at 40, 80 and 120 days after the induction. The pigmented lesions at flank and ear was photographed at days 40 (b, e), 80 (c, f), and 120 (d, g) following the 4-OHT induction. h–m Histology of melanoma in mice. Mouse tissues were processed and histology was examined using hematoxylin and eosin stain. Increased pigmented cells in the dermis were present at day 40 (h) and pigmented cells formed small tumor nodules in the dermis at day 80 (i). At day 120, melanoma cells formed bigger tumor nodules (j, k). Cytologically, these tumor cells were focally pigmented and had enlarged nuclei, a morphology that is similar to human melanoma (l). Tumor cells were stained positive for the S100 antibody (m). Bars in b–g indicate 5 mm. Bars in h–j indicate 200 μm. Bar in k indicates 400 μm. Bars in l, m indicate 50 μm