The CT26 cell line is an undifferentiated mouse colon cancer cell line induced by N-nitroso-N-methylurethane (NNMU). A clone derived from this cell line was named CT26.WT. The CT26.WT cells were stably transformed using a retroviral vector, LXSN, to generate a lethal subclone called CT26.CL25. This viral vector carries the lacZ gene, which encodes both a tumor-associated antigen (TAA) and beta-galactosidase. CT26.WT and CT26.CL25 cells exhibit similar growth rates and lethality in mice. However, CT26.CL25 cells can express the tumor-associated antigen and beta-galactosidase, making these two cell lines suitable for combined use in studies on immunotherapy and host immune responses.