Leech salivary gland extract from Haementeria officinalis, a potent inhibitor of cyclophosphamide- and radiation-induced artificial metastasis enhancement.

Studies were designed to determine whether salivary gland extract (SGE) from the leech Haementeria officinalis could inhibit enhancement of lung tumor colonization induced by pretreatment of mice with cyclophosphamide (CY) or local thoracic irradiation (LTI). Tumor nodules in the lung were generated by i.v. injections of T241 sarcoma and FSA fibrosarcoma cells into syngeneic C57BL/6 and C3Hf/Kam mice, respectively. CY (200 mg/kg) was given i.p. 1 or 4 days prior to i.v. injection of tumor cells. In other mice, a single dose of 1000 rads of LTI was given 1 day before tumor cells. Three i.v. or i.p. injections of SGE at doses of 600 to 800 micrograms of protein per injection given at 2-hr intervals between 2 hr before and 4 hr after CY, LTI, or tumor cell injection strongly inhibited and, in some cases, abolished the artificial metastasis enhancing effect of CY and LTI. SGE was similarly effective in inhibiting the enhancement of lung colonization when given before or after cytotoxic agents. Using [125I]iododeoxyuridine-labeled tumor cells, it was observed that SGE did not affect the initial lodgement of tumor cells in the lung, but it greatly facilitated their subsequent release from the lung. In normal mice, the SGE was active when given on the day or 1 day before but not when given 4 days before tumor cells. The antimetastatic effect of SGE was ascribed to its anti-platelet-aggregating, anticoagulant, and antiproteolytic enzyme activities.