CTLA4 and neoplasm: Among antagonistic aptamers, CTLA4apt–STAT3 siRNA, specific to CTLA4 and conjugated to STAT-3 siRNA, inhibits tumor proliferation and metastasis by down-regulation of STAT-3 gene expression in CD8+ and regulatory T cells infiltrated within tumors; its main strengths and limitations are presented in Table 4 [59,69].