The participation of the Fas-mediated cytotoxic pathway by natural killer cells is tumor-cell-dependent

Abstract

Cytotoxic T lymphocytes and natural killer (NK) cells kill target cells by two main mechanisms, namely, the perforin/granzymes and the Fas ligand (Fas-L) pathways. The preferential activation of either of these two mechanisms by target cells is not known. This study examined whether various NK stimuli regulate preferentially the perforin/granzyme or the Fas pathways during the NK-cell-mediated cytotoxic reaction (NK-CMC). Purified peripheral-blood-derived NK cells were stimulated with interleukin-2 (IL-2), IL-12, or interferon alpha (IFN alpha) and their response was analyzed by the reverse transcriptase/polymerase chain reaction (RT-PCR) for NK-associated gene expression and by the 51Cr-release assay for cytotoxic function. RT-PCR data revealed that the perforin, granzyme A and granzyme B mRNAs were constitutively expressed in unstimulated NK cells and the level of perforin mRNA was augmented following activation. IL-2 enhanced the level of Fas-L mRNA in NK cells; however, the Fas-L level was much lower than that obtained in activated T cells. NK-CMC against Fas-sensitive cells was examined in the presence of neutralizing anti-(Fas antigen receptor) (Fas-R) antibody (ZB-4) or EGTA/Mg2+, which inhibits the perforin/granzyme pathway but not the Fas Fas-L interaction. The human colon adenocarcinoma HT-29 cells were sensitized to anti-Fas-R antibody (CH-11) cytotoxicity following treatment with IFN gamma. NK-CMC against untreated HT-29 cells was completely inhibited by EGTA/Mg2+ and was unaffected by ZB-4, while both EGTA/Mg2+ and ZB-4 partially inhibited NK-CMC against IFN gamma-treated HT-29 cells. Similar findings to those obtained with untreated NK cells were observed with NK cells stimulated with IL-2, IL-2 plus IL-12 or IFN alpha. In contrast to IFN gamma-treated HT-29 cells, the neutralizing anti-Fas antibody ZB-4 did not inhibit NK-CMC against Fas-sensitive U937, CEM or Jurkat tumor cells. These findings demonstrate that the Fas pathway is involved in NK-CMC against certain target cells but not all. Further, the data demonstrate that activation of NK cells by IL-2, IL-2 plus IL-12 or IFN alpha does not preferentially modulate the Fas-L-mediated killing by NK cells.

The Molecular Interaction of Fas and FAP-1

“…In this study, we observed that treatment of DLD-1 cells with actinomycin D reduced the expression level of FAP-1 mRNA and enhanced Fas-induced apoptosis dramatically. These results are consistent with the recent report that actinomycin D-treatment of AIDS-associated Kaposi's sarcoma cells down-regulates FAP-1 mRNA and also sensitized these cells to Fasinduced apoptosis (44).…”

Protein-tyrosine Phosphatase PTPL1/FAP-1 Triggers Apoptosis in Human Breast Cancer Cells

“…Altogether our data on apoptosis in wildtype and PTPL1 antisense transfectants are therefore concordant with the concept that PTPL1 is a pro-apoptotic enzyme in estrogen receptor-positive breast cancer cells by early inhibition of the PI3-K/Akt pathway. (31)(32)(33), whereas other groups failed to find such a correlation (34 -36), which altogether seemed to highly depend on the cell line examined and therefore strongly suggested that it was a tissueor a cell-specific event. We have evaluated the ability of an anti-Fas antibody to induce apoptosis in three estrogen-sensitive breast cancer cell lines, which expressed varying levels of PTPL1/FAP-1, wild-type MCF7 cells (low expression), T47D cells (3.5-fold more expression than in MCF7 cells) (Fig.…”

“…Some studies have provided evidence for a high level of FAP-1 mRNA expression in Kaposi's sarcoma (31) and, in pancreatic adenocarcinomas (33), a higher expression in T helper cells type 1 (which are resistant to apoptosis) than in T helper cells type 2 (which are sensitive to Fas ligand) (32). Other groups failed to show any correlation between Fas resistance and FAP-1 expression in colon cancer (34), in subclones of S49.1 murine T lymphocytes (35), in adult T cell leukemia cell lines (36), and in testicular germ cells where exposure to mono-(2-ethylhexyl) phthalate induces massive cell death and increases FAP-1 expression (47).…”

Granulocytes mediates the Fas-L-associated apoptosis during lung metastasis of melanoma that determines the metastatic behaviour

“…Recent studies have also demonstrated that T cells specific for tumour antigens can become actively tolerated during progression of tumours (Mackensen et al, 1993;Adler et al, 1998). It is possible that altered T cells may produce a distinct profile of cytokine productions, which in turn stimulate tumour formation (Medvedev et al, 1997;Mori et al, 1997). …”