Bystander signaling between glioma cells and fibroblasts targeted with counted particles

Abstract

Radiation-induced bystander effects may play an important role in cancer risks associated with environmental, occupational and medical exposures and they may also present a therapeutic opportunity to modulate the efficacy of radiotherapy. However, the mechanisms underpinning these responses between tumor and normal cells are poorly understood. Using a microbeam, we investigated interactions between T98G malignant glioma cells and AG01522 normal fibroblasts by targeting cells through their nuclei in one population, then detecting cellular responses in the other co-cultured non-irradiated population. It was found that when a fraction of cells was individually irradiated with exactly 1 or 5 helium particles ( 3 He 2þ ), the yield of micronuclei (MN) in the non-irradiated population was significantly increased. This increase was not related to the fraction of cells targeted or the number of particles delivered to those cells. Even when one cell was targeted with a single 3 He 2þ , the induction of MN in the bystander non-irradiated population could be increased by 79% for AG01522 and 28% for T98G. Furthermore, studies showed that nitric oxide (NO) and reactive oxygen species (ROS) were involved in these bystander responses. Following nuclear irradiation in only 1% of cells, the NO level in the T98G population was increased by 31% and the ROS level in the AG0 population was increased by 18%. Treatment of cultures with 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide (c-PTIO), an NO scavenger, abolished the bystander MN induction in nonirradiated AG01522 cells but only partially in non-irradiated T98G cells, and this could be eliminated by treatment with either DMSO or antioxidants. Our findings indicate that differential mechanisms involving NO and ROS signaling factors play a role in bystander responses generated from targeted T98G glioma and AG0 fibroblasts, respectively. These bystander interactions suggest that a mechanistic control of the bystander effect could be of benefit to radiotherapy. ' 2005 Wiley-Liss, Inc.

Low-Dose Hypersensitivity and Bystander Effect are Not Mutually Exclusive in A549 Lung Carcinoma Cells after Irradiation with Charged Particles

“…So far, irradiation with helium particles (Burdak-Rothkamm et al, 2006;Shao et al, 2005;Zhou et al, 2004), soft carbon X-rays , carbon and uranium particles (Fournier et al, 2007) have been used. Again the effect for a given endpoint is estimated from the proportion of irradiated cells and compared to the experimental measurements.…”

ATR-dependent radiation-induced γH2AX foci in bystander primary human astrocytes and glioma cells

“…Bystander effects induced by ionizing irradiation have been studied by various approaches including transfer of conditioned medium from irradiated cells (Lyng et al, 2002;Maguire et al, 2005), low particle fluence irradiation, where only a few percent of cells are irradiated (Azzam et al, 1998), and targeted irradiation of single cells and subcellular structures (Shao et al, 2004;Shao et al, 2003bShao et al, , 2005. They have been shown to occur in both tumour and normal cell types.…”

“…However, the mechanisms involved in bystander signalling have only partially been elucidated and are probably dependent on cell type and end points investigated. The involvement of soluble factors like reactive oxygen species (ROS) (Azzam et al, 2002;Shao et al, 2003aShao et al, , 2005, nitric oxide (NO) (Shao et al, 2003b(Shao et al, , 2005Sokolov et al, 2005) and cytokines released from irradiated cells as well as gap junction intercellular communication (Azzam et al, 2001;Shao et al, 2003a;Mitchell et al, 2004;Sokolov et al, 2005) have recently been reported. Most interestingly, several cytokines can be induced by ROS and NO/NOS (Ayache et al, 2002;Hsu and Wen, 2002;Kosmidou et al, 2002;Hwang et al, 2004;Ryan et al, 2004) providing a possible link between different factors potentially involved in bystander signalling.…”

Medium-mediated intercellular communication is involved in bystander responses of X-ray-irradiated normal human fibroblasts

“…Evidence is accumulating that multiple signal transduction pathways are involved in this process, including oxidative metabolism Shao et al, 2003), gap junction-mediated intercellular communication (GJIC) (Azzam et al, 2001;Ballarini et al, 2002;Wang et al, 2004) and soluble extracellular factors (Iyer and Lehnert, 2000;Little et al, 2002). Earlier studies showed that bystander effects could be induced by treatment of unirradiated cells with medium taken from cell cultures previously exposed to irradiation Seymour, 1997, 1998;Mothersill, 1999, 2000;Lyng et al, 2002).…”