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Modulation of the growth of pulmonary tumour colonies in mice after single or fractionated low-level irradiations with X-rays

Nowosielska E. M., Cheda A., Wrembel-Wargocka J., Janiak M. K.

Nukleonika

2008

Vol. 53, suppl. 1

9-15

A number of epidemiological and experimental data indicate that exposures to low doses of low-LET ionizing radiation may trigger the activity of natural anti-tumour immune mechanisms and inhibit tumour growth. Natural killer (NK) cells and activated macrophages play important roles in the anti-tumour defence of the host. In view of this, the aim of the present study was to correlate the tumour-inhibitory effect of low doses of X-rays with the activities of NK cells and macrophages. BALB/c mice were whole-body irradiated with single or fractionated doses of 0.1, 0.2, or 1.0 Gy X-rays and then intravenously injected with L1 sarcoma cells; 14 days later, tumour colonies on the lungs' surface were counted. Cytotoxic activities of NK cells and macrophages were estimated using the 51Cr-release and [3H]thymidineuptake assays, respectively. The anti-asialo GM1 antibody and carrageenan (CGN) were intraperitoneally injected to block the NK cell- and macrophage-mediated activities in vivo, respectively. Single and fractionated whole-body irradiation (WBI) of mice with 0.1 or 0.2 Gy X-rays led to reduction in the number of the pulmonary tumour colonies accompanied by the enhanced cytotoxic activities of both NK lymphocytes and macrophages. Treatment of mice with anti-asialo GM1 antibody or CGN abrogated the tumour-inhibitory effects of the low-level exposures to X-rays. The obtained data suggest that suppression of the development of pulmonary tumour colonies by single or fractionated irradiations of mice with the low doses of X-rays may result from stimulation of the natural anti-tumour defence reactions mediated by NK cells and/or cytotoxic macrophages.

Low-level exposures to ionising radiation modulate the anti-tumour activity of murine NK cells

Nowosielska E., Wrembel-Wargocka J., Cheda A., Lisiak E., Janiak M.

Nukleonika

2005

Vol. 50,suppl.2

21-24

Experimental evidence from the recent years indicates that low-level irradiations with X- or gamma rays may inhibit development of both primary and secondary tumours and stimulate the activity of natural anti-tumour immune mechanisms. Natural killer (NK) cells play an important role in anti-tumour defence of the host. In the present investigation cytotoxic activity, production of interferon-ă, and expression of the Fas ligand (FasL) were estimated in the NK splenocytes collected from BALB/c mice whose whole body was pre-exposed to irradiation with 0.1, 0.2, or 1.0 Gy X-rays. The results indicate that cytotoxic activity of the irradiated NK cells was significantly stimulated compared to that of the NK effectors obtained from the sham-exposed mice. This effect was totally abrogated by injection of the anti-asialo GM1 antibody. In addition, compared to the control mice, NK cells obtained from the irradiated animals exhibited reduced surface expression of FasL. Collectively, the obtained results suggest that the inhibitory effect of the low-level irradiations with X-rays on the development of pulmonary tumour nodules may be directly associated with stimulation by such exposures of anti-neoplastic functions mediated by NK cells.