TY  - JOUR
A1  - Houben, Roland
A1  - Alimova, Pamela
A1  - Sarma, Bhavishya
A1  - Hesbacher, Sonja
A1  - Schulte, Carolin
A1  - Sarosi, Eva-Maria
A1  - Adam, Christian
A1  - Kervarrec, Thibault
A1  - Schrama, David
T1  - 4-[(5-methyl-1H-pyrazol-3-yl)amino]-2H-phenyl-1-phthalazinone inhibits MCPyV T antigen expression in Merkel cell carcinoma independent of Aurora kinase A
JF  - Cancers
N2  - Merkel cell carcinoma (MCC) is frequently caused by the Merkel cell polyomavirus (MCPyV), and MCPyV-positive tumor cells depend on expression of the virus-encoded T antigens (TA). Here, we identify 4-[(5-methyl-1H-pyrazol-3-yl)amino]-2H-phenyl-1-phthalazinone (PHT) — a reported inhibitor of Aurora kinase A — as a compound inhibiting growth of MCC cells by repressing noncoding control region (NCCR)-controlled TA transcription. Surprisingly, we find that TA repression is not caused by inhibition of Aurora kinase A. However, we demonstrate that β-catenin — a transcription factor repressed by active glycogen synthase kinase 3 (GSK3) — is activated by PHT, suggesting that PHT bears a hitherto unreported inhibitory activity against GSK3, a kinase known to function in promoting TA transcription. Indeed, applying an in vitro kinase assay, we demonstrate that PHT directly targets GSK3. Finally, we demonstrate that PHT exhibits in vivo antitumor activity in an MCC xenograft mouse model, suggesting a potential use in future therapeutic settings for MCC.
KW  - Merkel cell carcinoma
KW  - polyomavirus
KW  - large T antigen
KW  - phthalazinone pyrazole
KW  - glycogen synthase kinase 3
KW  - GSK3
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-313547
SN  - 2072-6694
VL  - 15
IS  - 9
ER  - 
TY  - JOUR
A1  - Houben, Roland
A1  - Ebert, Marlies
A1  - Hesbacher, Sonja
A1  - Kervarrec, Thibault
A1  - Schrama, David
T1  - Merkel Cell Polyomavirus Large T Antigen is Dispensable in G2 and M-Phase to Promote Proliferation of Merkel Cell Carcinoma Cells
JF  - Viruses
N2  - Merkel cell carcinoma (MCC) is an aggressive skin cancer frequently caused by the Merkel cell polyomavirus (MCPyV), and proliferation of MCPyV-positive MCC tumor cells depends on the expression of a virus-encoded truncated Large T antigen (LT) oncoprotein. Here, we asked in which phases of the cell cycle LT activity is required for MCC cell proliferation. Hence, we generated fusion-proteins of MCPyV-LT and parts of geminin (GMMN) or chromatin licensing and DNA replication factor1 (CDT1). This allowed us to ectopically express an LT, which is degraded either in the G1 or G2 phase of the cell cycle, respectively, in MCC cells with inducible T antigen knockdown. We demonstrate that LT expressed only in G1 is capable of rescuing LT knockdown-induced growth suppression while LT expressed in S and G2/M phases fails to support proliferation of MCC cells. These results suggest that the crucial function of LT, which has been demonstrated to be inactivation of the cellular Retinoblastoma protein 1 (RB1) is only required to initiate S phase entry.
KW  - Merkel cell polyomavirus
KW  - large T antigen
KW  - cell cycle
KW  - Merkel cell carcinoma
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-218171
SN  - 1999-4915
VL  - 12
IS  - 10
ER  -