FAS and neoplasm: Of particular importance, TIL-Bs can exhibit direct cytotoxic activity, killing tumor cells via the Fas/FasL pathway (11): Activated B cells in tumor-draining lymph nodes (DLNs) have been shown to express the Fas ligand, to be upregulated upon engagement with cells of the 4T1 triple-negative breast cancer (TNBC) cell line, and, in turn, to exhibit cytotoxic activity (12).