CTLA4 and colon carcinoma: The systemic inhibition of Tregs using CHX and anti-CD25-antibodies in an in vivo tumor-bearing mouse model (lung and colon carcinoma) or via CTLA4 blockage in an in vivo tumor-bearing mouse model (colon carcinoma) after irradiation of the tumor resulted in reduced growth of distant non-irradiated tumor cells (63, 74).