The development of
tumor therapies based on the activation of antitumor immunity requires
tumor models that are highly immunogenic. The immunologic response to
fluorescent proteins, green fluorescent
protein (GFP), or enhanced GFP (EGFP) was demonstrated in different
cancer models. However, for live animal imaging, red and far-red fluorescent
proteins are preferable, but their immunogenicity has not been studied. We assessed the immunogenicity of the
red fluorescent protein, KillerRed (KR), in CT26 murine colon
carcinoma. We showed a slower growth and a lower
tumor incidence of KR-expressing
tumors in comparison with nonexpressing ones. We found that KR-expressing lung
metastases and rechallenged
tumors were not formed in mice that had been surgically cured of KR-expressing primary
tumors. The effect of low-dose
cyclophosphamide (CY) treatment was also tested, as this is known to activate antitumor immune responses. The low-dose CY
therapy of CT26-KR
tumors resulted in inhibition of
tumor growth and improved mouse survival. In summary, we have established a highly immunogenic
tumor model that could be valuable for investigations of the mechanisms of antitumor immunity and the development of new therapeutic approaches.