CTLA4 and breast cancer: While it has been demonstrated that CTLA-4 expression can be an important mechanism of tumor immune evasion14,15, with high levels of CTLA-4 expression in tumor tissues being associated with poor overall survival16, a recent study on breast cancer patients found that elevated sCTLA-4 levels were associated with improved survival17 and several other studies have showed significant correlations between CTLA-4 and improved OS in other cancer types12.