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Myc lacks E2F1's ability to suppress skin carcinogenesis
R J Rounbehler1, R Schneider-Broussard, C J Conti
1University of Texas M.D. Anderson Cancer Center, Science Park Research Division, Park Road 1C, Smithville, Texas 78957, USA.
Abstract:
Myc and E2F1 can each stimulate proliferation, induce apoptosis, and contribute to oncogenic transformation. However, only E2F1 has been shown to have a tumor suppressive activity under some conditions. To examine the potential of Myc to suppress tumorigenesis under one of the conditions in which E2F1 functions to suppress tumorigenesis, transgenic mice expressing Myc under the control of a keratin 5 (K5) promoter were generated. Like K5 E2F1 transgenic mice, K5 Myc transgenic mice have hyperplastic and hyperproliferative epidermis and develop spontaneous tumors in the skin and oral epithelium. In addition, K5 Myc and K5 E2F1 transgenic mice both display aberrant, p53-dependent apoptosis in the epidermis. It has been demonstrated that deregulated expression of E2F1 in the epidermis of transgenic mice inhibits tumorigenesis in a two-stage skin carcinogenesis assay. In sharp contrast to those results, deregulated expression of Myc in the epidermis of transgenic mice resulted in an enhanced response to two-stage skin carcinogenesis. We conclude that while Myc and E2F1 have similar proliferative, apoptotic and oncogenic properties in mouse epidermis, Myc lacks E2F1's tumor suppressive property. This suggests that E2F1's unique ability to inhibit skin carcinogenesis is not simply a consequence of promoting p53-dependent apoptosis.
Insights
Myc and E2F1 promote cell growth and cancer. While E2F1 can suppress tumors, Myc does not, even with similar effects on cell division and death in mouse skin. This highlights E2F1's unique tumor-inhibiting role.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Myc and E2F1 are key regulators of cell proliferation, apoptosis, and oncogenesis.
- E2F1 exhibits tumor-suppressive activity under specific conditions, unlike Myc.
- Understanding differential roles in tumorigenesis is crucial for cancer research.
Purpose of the Study:
- To investigate Myc's tumor suppressive potential in conditions where E2F1 acts as a tumor suppressor.
- To compare the effects of deregulated Myc and E2F1 expression in mouse epidermis on tumorigenesis.
Main Methods:
- Generation of transgenic mice expressing Myc under a keratin 5 (K5) promoter.
- Analysis of epidermal hyperplasia, proliferation, and apoptosis in K5 Myc and K5 E2F1 mice.
- Evaluation of tumor development and response to a two-stage skin carcinogenesis assay.
Main Results:
- K5 Myc transgenic mice exhibited hyperplastic, hyperproliferative epidermis and developed spontaneous skin and oral tumors, similar to K5 E2F1 mice.
- Both K5 Myc and K5 E2F1 mice showed aberrant, p53-dependent apoptosis in the epidermis.
- While E2F1 inhibited tumorigenesis in a skin carcinogenesis assay, Myc enhanced the response.
Conclusions:
- Myc and E2F1 share proliferative, apoptotic, and oncogenic properties in mouse epidermis.
- Myc lacks the tumor-suppressive property observed for E2F1 in this context.
- E2F1's ability to inhibit skin carcinogenesis is not solely due to p53-dependent apoptosis.