In Vitro Generation of Bacillus Calmette-Guérin-Activated Killer Cells

Abstract

Tumor regression induced in cancer patients by local instillation of bacillus Calmette-Guérin (BCG) into the bladder is considered to be mediated by cellular immune and inflammatory reactions. In an attempt to elucidate which of these effects are relevant to tumoricidal activity, an in vitro system was employed in which the immunostimulatory effects of BCG could be studied. This report describes the induction of BCG-activated killer (BAK) cells, which effectively lyse bladder tumor cells. Human peripheral blood mononuclear cells (PBMC) were stimulated with viable and sonicated BCG (v-BCG and s-BCG, respectively) to generate BAK cells. Cytotoxicity of BAK cells was comparable with the cytotoxicity exerted by lymphokine-activated killer (LAK) cells generated by interferon (IFN)-gamma but did not reach the level of interleukin-2 (IL-2)-generated LAK cells. Induction of BAK cells was possible only with v-BCG and not with s-BCG. By depletion and enrichment of defined cell populations, the cytotoxic potential of BAK cells could be attributed to a population of CD8(+) and CD56(+) double-positive lymphocytes. Macrophages and CD4(+) cells were required for the induction of killing activity but had no such activity by themselves. Furthermore, the presence of IFN-gamma and IL-2 in the supernatants harvested during the generation of BAK cells was demonstrated. Monoclonal antibodies neutralizing these cytokines abolished BCG-mediated cytotoxicity. From these results, it is concluded that the known beneficial effect of local instillation of BCG on maintenance of the relapse-free state in superficial bladder cancer may be due to local generation of BAK cells.

Construction of recombinant human IFNα-2b BCG and its antitumor effects on bladder cancer cells in vitro

“…Furthermore, the level of hIFN-g produced by rBCG-induced PBMCs was significantly higher than that in the other 2 groups. Previous studies have demonstrated that IFN-g, TNF-a, and IL-12 are antiproliferative to cancer cells, as well as induce apoptosis (Thanhäuser et al, 1995;Brandau et al, 2000a). In addition, Luo et al (2001) showed that the restructuring of hIFNa-2b-rBCG effectively induced generation of hIFN-g, hTNF-a, and hIL-12, which was clearly higher than that in wild-type BCG and wild-type BCG plus IFN.…”

Capsular Arabinomannans from Mycobacterium avium with Morphotype-specific Structural Differences but Identical Biological Activity

“…Both lipoglycans and AMs induced profound anti-tumor cytotoxicity in the range of 40 to 60% of that obtained by M. bovis BCG. BCG has been described as inducing strong natural killer cell-mediated tumor cell lysis in this system and serving as a positive control (44,45).…”

Th1 Cytokine-Secreting Recombinant Bacillus Calmette-Guérin: Prospective Use in Immunotherapy of Bladder Cancer

“…These effector cell types are crucial for BCG immunotherapy of bladder cancer, as depletion of these cell types failed to develop effective anti-bladder cancer responses in vivo and kill bladder cancer cells in vitro (Ratliff et al, 1993;Brandau et al, 2001). It has been shown that stimulation of human peripheral blood mononuclear cells (PBMC) by viable BCG in vitro leads to the generation of a specialized cell population called BCGactivated killer (BAK) cells (Böhle et al, 1993;a Brandau et al, 2000). BAK cells are a CD3 -CD8 + CD56 + cell population whose cytotoxicity is MHC non-restricted ( a,b Brandau et al, 2000).…”

“…It has been shown that stimulation of human peripheral blood mononuclear cells (PBMC) by viable BCG in vitro leads to the generation of a specialized cell population called BCGactivated killer (BAK) cells (Böhle et al, 1993;a Brandau et al, 2000). BAK cells are a CD3 -CD8 + CD56 + cell population whose cytotoxicity is MHC non-restricted ( a,b Brandau et al, 2000). BAK cells kill bladder cancer cells through the perforin-mediated lysis pathway and are effective on lysing NK cell-resistant bladder cancer cells (Böhle et al, 1993; Brandau et al, 2000).…”

“…BAK cells are a CD3 -CD8 + CD56 + cell population whose cytotoxicity is MHC non-restricted ( a,b Brandau et al, 2000). BAK cells kill bladder cancer cells through the perforin-mediated lysis pathway and are effective on lysing NK cell-resistant bladder cancer cells (Böhle et al, 1993; Brandau et al, 2000). Macrophages and CD4 + T cells have been found to be indispensable for the induction of BAK cell killing activity but have no such activity by themselves ( a Brandau et al, 2000).…”