Figure 3. BRaf^V600E cooperates with Pten loss in the induction of invasive and metastatic melanoma.

(a) Tyr::CreER; BRaf^CA/+; Pten^{lox4-5/lox4-5} mice were treated topically on the ear, flank and tail with 4-HT. 6 weeks later mice were euthanized and inspected for evidence of pigmented cells in the mammary gland lymph node. Tyr::CreER; BRaf^CA/+; Pten^lox5/lox5 mice were treated similarly to those described in (a), euthanized and then inspected by microscopy at low (b) and high (c) power for the presence of pigmented cells in the lymph nodes.

(d) A Tyr::CreER; BRaf^CA/+; Pten^lox5/lox5 mouse was treated topically with 5mM 4-HT in 100%(v/v) ethanol on the distal tail. The mouse had a visible tumor within 4 weeks but did not require euthanasia until 24 weeks later after 4-HT administration. The presence of pigmented cells in the Iliac, lumbar, inguinal, axillary and submandibular lymph nodes was assessed by stereomicroscopy. Tumor cells were restricted to the iliac nodes (pictured).

(e-f) Tyr::CreER; BRaf^CA/+; Pten^{lox4-5/lox4-5} mice were treated topically on the ear, flank and tail with 4-HT. Mice were euthanized 6-7 weeks after 4-HT treatment at which times the lungs were excised, cleared of blood and visually inspected for the presence of pigmented lesions (e) and (f). Lung sections were prepared, stained with hematoxylin and eosin and examined for the presence of pigmented cells in the lung parenchyma (g).