Positive Health Online

Abstract

ISHIHARA and colleagues, Department of Hygiene and Public Health (I), School of Medicine, Tokyo Womens Medical University, Japan investigated the effect of the timing of stressor application upon transplanted tumour cells and its possible regulation by an immunomodulator .

Background

Methodology

Male C57 BL/6N mice were administered a rotational stressor for 7 days relative to tumour cell inoculation, i.e. stressor following inoculation of Lewis lung cancer cells, stressor during inoculation and stressor prior to inoculation.

Results

Stressor application and tumour cell inoculation caused transient decreases in body weight, particularly in mice stressed following inoculation. Compared to control mice, those mice exposed to the stressor during, or prior to inoculation showed significant increases in the number of metastatic foci. Early administration of an immunomodulator, PSK, significantly attenuated the increase in metastatic foci in stressed mice. Weights of thymus gland and spleen 14 days following inoculation were similar across the three stressor and control groups. Application of the stressor reduced NK cell activity of the normal mice, as well as tumour bearing mice. The lowest pre-inoculation NK cell activity was in mice stressed for 7 days starting on the day of inoculation. NK cell activity decreased in tumour bearing mice stressed at the time of tumour inoculation. Decreased NK cell activity was reversed at day 14 following tumour inoculation. Compared to mice exposed to the stressor prior to or during inoculation, mice exposed after inoculation showed the lowest level of NK cell activity. Treatment with PSK reduced these changes significantly.

Conclusion

The above results suggest that the rotational stress reduces splenic NK cell activity, which may influence the magnitude of tumour metastasis, depending upon time of tumour cell injection. Additionally, administration of an immunomodulator may counteract reduction of NK cell activity.

References

Ishihara Y et al. Time-dependent effects of stressor application on metastasis of tumor cells in the lung and its regulation by an immunomodulator in mice. Psychoneuroendocrinology 24(7): 713-26. Oct 1999.