Modulation of tumor growth by allogeneic blood transfusion

The effect of a single blood transfusion on the formation and outgrowth of experimental lung metastases was assessed in two tumor models in rats. The transfusions were given either 1 week before (day -7) or 1 week after (day +7) tumor cell inoculation. The first approach was performed to investigate the effect of transfusions on the formation of lung colonies, the second approach to study the effect on the outgrowth of established metastases. The first tumor model used was a transplantable, nonimmunogenic sarcoma (LS175) in BN rats. Animals were injected i.v. with 10(5) tumor cells and the number of metastases developing in the lungs was counted after 18 days. Experimental animals received 1 ml of allogeneic WAG blood, controls were given 1 ml of syngeneic BN blood. A single allogeneic transfusion given on day -7 had no effect on the formation of LS175 lung colonies but, when given day +7, stimulated the outgrowth of established metastases. The second tumor model was a highly immunogenic transplantable basal cell carcinoma (BC1618) in inbred WAG rats. Rats were injected i.v. with 10(6) tumor cells and the numbers of lung colonies were counted after 21 days. Experimental animals were transfused with 1 ml of BN blood, controls received 1 ml of WAG blood. An allogeneic transfusion on day -7 led to a significant inhibition of lung metastases, whereas a transfusion on day +7 had no effect. The results clearly indicate that allogeneic blood transfusions can modulate tumor growth and metastasis. Although immunological factors seem to play a crucial role in this transfusion phenomenon, there was no clear-cut correlation between the observed effects (accelerated tumor growth vs inhibition of metastasis) and the type of immunomodulation evoked.