The importance of the Cdk4 protein in human cancer became evident

The importance of the Cdk4 protein in human cancer became evident following the identification of a germ line mutation in the locus that predisposes humans to melanoma. we report an increased incidence of spontaneous cutaneous melanoma in mice expressing the oncogene SRT3190 and genes are often observed in human familial melanoma.2 3 Approximately 20-40% of familial melanoma patients inherit mutations.4 The gene encodes two SRT3190 distinct tumor-suppressor proteins Ink4a and Arf (known as p14 in humans and p19 in mice). Homozygous deletion of this locus has been observed in cultured melanoma lines such as SK-MEL.5 knockout mice do not develop melanoma but do develop tumors such as fibrosarcoma and lymphoma.6 The importance of the pathway in melanoma was highlighted further with the identification of a germline mutation in familial melanoma patients.2 3 Two mutations SRT3190 have been observed in the 24th codon of and mice with Tyr-mice develop spontaneous cutaneous metastatic melanoma with a low incidence of metastatic optical melanoma.7 In 1999 Chin et al. crossed a doxycycline-inducible Tyr-mouse with an mouse to demonstrate that persistent expression of HRas is required for both initiation and maintenance of melanoma.8 In the case of mice removal of doxycycline from the feed causes repression resulting in regression of pre-existing melanomas.8 Interestingly activated has also been observed in proliferative defects in human skin. In the melanocytes of Spitz nevi for example the coding sequence contains point mutations and the entire locus is usually amplified.9 Activated has been reported in 33% of primary human melanomas and in 26% of metastatic melanomas.10 Recently two point mutations in the gene were observed in 66% of melanomas resulting in increase in Braf kinase activity.11 These observations suggest that members of the Ras pathway play an important role in melanoma development. Furthermore and mutant genes we mated Rabbit Polyclonal to C14orf49. Tyr-mice with mice to study their respective functions in the development of melanoma. Results The Cdk4-R24C mutation contributes to the development of melanoma in Tyr-HRas mice. To determine whether and alleles cooperate in the development of melanoma we crossed Tyr-HRas mice SRT3190 with Cdk4R24C/R24C and Cdk4+/+ mice to generate three different mouse strains: Tyr-HRas:Cdk4R24C/R24C Tyr-HRas:Cdk4+/R24C and Tyr-HRas:Cdk4+/+. Because the transgene is usually integrated around the Y chromosome only males carry the transgene. Therefore all the mice SRT3190 used in this study were males. We compared the development of melanomas in Tyr-HRas:Cdk4R24C/R24C Tyr-HRas:Cdk4+/R24C and Tyr-HRas/Cdk4+/+ over a period of eighteen months. Tyr-HRas:Cdk4R24C/R24C and Tyr-HRas:Cdk4+/R24C began to develop cutaneous melanomas between the ages of seven and fifteen months (Fig. 1) while Tyr-HRas:Cdk4+/+ mice did not develop any tumors. We observed a tumor incidence of 30% in Tyr-HRas:Cdk4R24C/R24C and Tyr-HRas:Cdk4+/R24C mice. Interestingly there was no significant difference in the tumor incidences in these two genotypes. Females (which do not carry activated transgene) were used SRT3190 as controls. As expected we did not observe any spontaneous melanomas in the females. Physique 1 Contribution of the Cdk4R24C mutation in the development of melanoma in Tyr-HRas mice. (A) Crosses performed to produce the required transgenic mice represented by dotted rectangles. Male mice are represented by squares and female mice are represented … Spontaneous cutaneous melanoma in Tyr-HRas:Cdk4. The cutaneous melanomas that developed in Tyr-HRas:Cdk4R24C/R24C and Tyr-HRas:Cdk4+/R24C mice lacked pigmentation and therefore were classified as amelanotic melanomas. These tumors were very similar to those observed in the original mouse model of Tyr-HRas mice.7 The most common anatomical site for cutaneous melanomas was the ear pinna (96%) followed by the tail (3%) (Fig. 2A). The tumors were locally invasive and there was no evidence of macro-metastasis upon autopsy of the tumor-bearing mice. Upon sectioning and staining with hematoxylin and eosin we observed hyper-proliferation of the dermis in all of the cutaneous melanomas (Fig. 2C) with epidermal hyperplasia observed in some tumors (data not shown). The tumors were composed predominantly of spindle shaped cells (Fig. 2E) with a few epithelioid cells that expanded the dermis to form a tumor nodule. The tumor cells in the dermis were present in a storiform (cart wheel) pattern and showed mitotic figures as evidenced by the appearance of condensed chromosomes (see insert in Fig. 2E). Physique 2 Tyr-HRas:Cdk4R24C mice develop spontaneous cutaneous.