CD8A and breast cancer: In a triple negative breast cancer-like transgenic MMTV-PyMT murine model of breast cancer, an increase of more than two-fold in the percentage of intra-tumoral CD4+ and CD8+ T-cells were found in the mammary fat-pad tumors and lung metastases of PI3K-γ knockout mice versus PI3K-γ competent mice (115), along with a 50% reduction in primary tumor growth volume at 5-weeks, reduced metastases formation, increased TNF-alpha secretion by CD4+ and CD8+ TILs, and increased TIL expression of the T-cell activation marker CD69+.