Tumor-Specific CTL Kill Murine Renal Cancer Cells Using Both Perforin and Fas Ligand-Mediated Lysis In Vitro, But Cause Tumor Regression In Vivo in the Absence of Perforin

Abstract

Kidney cancer is a devastating disease; however, biological therapies have achieved some limited success. The murine renal cancer Renca has been used as a model for developing new preclinical approaches to the treatment of renal cell carcinoma. Successful cytokine-based approaches require CD8+ T cells, but the exact mechanisms by which T cells mediate therapeutic benefit have not been completely identified. After successful biological therapy of Renca in BALB/c mice, we generated CTLs in vitro using mixed lymphocyte tumor cultures. These CTL mediated tumor-specific H-2Kd-restricted lysis and production of IFN-γ, TNF-α, and Fas ligand (FasL) in response to Renca. CTL used both granule- and FasL-mediated mechanisms to lyse Renca, although granule-mediated killing was the predominant lytic mechanism in vitro. The cytokines IFN-γ and TNF-α increased the sensitivity of Renca cells to CTL lysis by both granule- and FasL-mediated death pathways. Adoptive transfer of these anti-Renca CTL into tumor-bearing mice cured most mice of established experimental pulmonary metastases, and successfully treated mice were immune to tumor rechallenge. Interestingly, we were able to establish Renca-specific CTL from mice gene targeted for perforin (pfp−/−) mice. Although these pfp−/− CTL showed reduced cytotoxic activity against Renca, their IFN-γ production in the presence of Renca targets was equivalent to that of wild-type CTL, and adoptive transfer of pfp−/− CTL was as efficient as wild-type CTL in causing regression of established Renca pulmonary metastases. Therefore, although granule-mediated killing is of paramount importance for CTL-mediated lysis in vitro, some major in vivo effector mechanisms clearly are independent of perforin.

In vivo rejection of tumor cells dependent on CD8 cells that kill independently of perforin and FasL

“…Besides the two main killing pathways, it has been reported that other killing mechanisms, for example the proinflammatory cytokines gIFN and TNFa, have important roles in rejection of pulmonary metastasis of tumor cells. 38 In the study of Poehlein et al, 31 adoptive transfer of effector T cells, which are taken from perforin and gIFN double knockout mice (PKO/GKO), mediated complete tumor regression and cured wild-type animals with established pulmonary metastasis of melanoma cells by a TNF-a mediated killing mechanism. In addition, Smyth et al 39 have reported that, using the Renca carcinoma tumor model, TRAIL expression on NK and NKT cells has effective antimetastatic functions in vivo mediated by a gIFNdependent immune mechanism.…”

GPI-anchored TIMP-1 treatment renders renal cell carcinoma sensitive to FAS-meditated killing

“…The relative importance of granule exocytosis versus FAS/FASL-mediated lytic activities for tumour control in vivo is controversial. While many studies point to a dominance of the granule exocytosis mechanism, other studies using perforin-knockout mice (Seki et al, 2002) suggest that FAS-dependent apoptosis may constitute a more prominent pathway in vivo. Therefore, it is of concern that most tumour cells, including RCC, are intrinsically resistant to FASmediated killing (Frost et al, 2003).…”

NK Cells and Cancer

“…Subcutaneous injections of NK-stimulating doses of IL-2 or administration of preactivated NK cells (adoptive transfer of LAK cells) showed a 15-30% positive effect in patients with advanced renal cell carcinoma (RCC) or melanoma (MEL) (42). However, both MEL and RCC show a variable susceptibility to apoptosis induced by TNF ligand members (46 -48), and the clearance of murine renal cancer cells in vivo often does not even require the perforin-mediated pathway (49). Thus, antitumor response following IL-2 treatment also involves the NKR-independent pathways of NK (and T) cell cytotoxicity.…”