gms | German Medical Science

Introduction: CK1δ phosphorylates key regulator proteins involved in cellular processes (e.g. proliferation, apoptosis) and modulates the activity of viral proteins, among them SV40 T-antigen. We generated a dominant negative mutant of CK1δ (mutCK1δ) with a highly reduced kinase activity, which strongly attenuated the transforming activity of T-Ag. To analyse factors involved in tumor development and –regression, we have further developed the SV40 T-Ag transgenic mouse model. We generated WAP-mutCK1δ/WAP-T transgenic mice. After the induction of the transgene/s the WAP-T transgenic and WAP-mutCK1d/WAP-T bitransgenic mice first develop DCIS and later an invasive carcinoma. To identify progression and/or regression factors tumors of transgenic and bitransgenic animals were analyzed on molecular level.

Materials and methods: A dominant negative mutant of CK1δ (mutCK1δ) was generated and characterized in vitro using SV40 transformed rat embryo fibroblast. WAP-mutCK1δ transgenic and WAP-mutCK1δ/WAP-T bitransgenic mice were generated, tumors and normal tissue of both groups were isolated. Staging, grading and expression of the transgenes were analysed. Kaplan-Meier survival curves were done. Differences in gene expression levels in mammary glands and tumor tissue were detected using real time PCR analysis.

Results: The dominant negative mutant of CK1δ (mutCK1δ) showed a highly reduced kinase activity and strongly attenuated the transforming activity of T-Ag in vitro.

Using a bi-transgenic mouse model, no significant differences in the staging and grading between WAP-T transgenic and WAP-mutCK1d/WAP-T bitransgenic mice could be verified. Transgene expression was detected in DCIS as well as in invasive carcinomas of different grades in both, WAP-mutCK1δ/WAP-T and WAP-T mice. However, Kaplan-Meier survival curves revealed a significant longer life-pan of WAP-mutCK1d/WAP-T bitransgenic mice compared to that of WAP-T transgenic mice. Differences in gene expression levels concerning the wnt-signalling pathway and DNA-repair pathways could be detected.

Conclusion: mutCK1d can influence the transformational competence of SV40 T-Ag in vitro and in vivo. Furthermore, our bitransgenic mouse model allows us to characterize factors which influence the tumor development of the ductal mammary carcinoma and to determine their prognostic relevance.