Retrovirus type C in the mouse bladder carcinoma cell line MBT-2

Purpose: The presence of replicating type C retrovirus in MBT-2 mouse bladd er carcinoma cells is reported. This MBT-2 tumor cell line is nowadays glob ally distributed. The cells have been and are still used to study various a spects of bladder cancer. While studying the phagocytic capacity of MBT-2 c ells for BCG organisms by electron microscopic methods, the presence of thi s retrovirus was noticed. Materials and Methods: MBT-2 cells that were cultured in vitro as well as c ells from intravesically and intradermally grown MBT-2 tumors from syngenei c mice were investigated using transmission electron microscopy (TEM) and s canning electron microscopy (SEM) techniques. Results: All samples including the earliest generation MBT-2 cells that cou ld be traced from stocks of other research groups contained the C type retr ovirus, suggesting a contamination in all available generations of the MBT- 2 cell line. Conclusions: As this tumor cell line is widely used in immunologic studies of the response to bladder cancer, it is important to consider the possible presence of type C viruses and associated antigens, since they could contr ibute to or interfere with the responses being measured. Studies should be initiated to determine whether viral antigen expression is involved in the immune rejection of MBT-2 bladder cancer. As a consequence, clinical implem entation of immunological treatment strategies should not be based on resul ts obtained with the MBT-2 model alone, but preferably should be confirmed with other (bladder) carcinoma models.