The effect of OK-432 upon erythropoietic recovery in sub-lethally irradiated mice: a preliminary report.

OK-432, a multicytokine inducer and clinically used as an immunopotentiating anti-cancer agent, is known to induce IL-1 and TNF-alpha. The suppressive effect of IL-1 and TNF-alpha on erythropoiesis could limit the clinical use of OK-432 in cancer treatment, especially when combined with radiotherapy. In this study, the effect of OK-432 on normal and X-ray impaired erythropoiesis was examined. C57BL/6J mice were injected with a single dose of OK-432 (5.0 KE). Erythropoietic activity was measured by 59Fe incorporation into circulating erythrocytes and the heme iron fraction of erythropoietic tissue. When irradiated with 662 cGy of X-rays, OK-432 prolonged the survival of mice. No significant change in erythropoiesis was observed when normal mice were treated with OK-432. When treated with OK-432, the recovery of erythropoiesis after irradiation was promoted as judged by the uptake of 59Fe into erythrocytes. This promotion was observed when OK-432 was injected within 1 day before or within 3 hours after the irradiation with 284 cGy of X-rays. This promoting effect, however, appeared to be limited to the spleen. Whether the combination of OK-432 with radiotherapy has the potential to improve the treatment of malignant tumors is still a subject of controversy. The present results, nevertheless, suggest that when combined with radiotherapy, OK-432, at the very least, may have no adverse effects on erythropoiesis.