Histological and proteomic analysis of reversible H-RasV12G expression in transgenic mouse skin.

We have used a two-transgene tetracycline system to reversibly express oncogenic H-Ras(V12G) in mouse skin and primary keratinocytes culture using the bovine keratin 5 promoter. Induction of H-Ras(V12G) expression in skin at 30 days after birth causes epidermal basal cell hyperplasia, an eruption of keratinous cysts and loss of hair follicles by 3 weeks. Subsequent H-Ras(V12G) de-induction for 3 days results in massive apoptosis in the non-H-Ras(V12G)-expressing stroma as well as in the suprabasal cells of the epidermis. Several procaspases such as CASP3, 1alpha, 5 and 12 disappeared, whereas the pro-apoptotic proteins AIF, Bax and Fas ligand were induced in H-Ras(V12G) de-induction skin. This process is followed by a wave of cell division at 14 days as hair follicles regrew, returning to near normal histology and skin appearance by 30 days. Using Kinetworkstrade mark multi-immunoblotting screens, the phosphorylation status of 37 proteins and expression levels of 75 protein kinases in the skin were determined in three samples: (i) wild-type skin, (ii) hyperplastic H-Ras(V12G)-expressing skin and (iii) skin where H-Ras(V12G) expression was suppressed for 7 days. Following H-Ras(V12G) induction, 16 kinases were increased over 2-fold, and 2 kinases were reduced over 50%. This included increased phosphorylation of both known downstream H-Ras(V12G) targets and unknown H-Ras(V12G) targets. After H-Ras(V12G) suppression, many but not all protein changes were reversed. These results from skin and primary keratinocytes are organized to reflect the molecular events that cause the histological changes observed. These proteomic changes identify markers that may mediate the oncogenic addiction paradigm.