EFFECT OF THE THYMIC-FACTOR, THYMOSTIMULIN (TP-1), ON THE SURVIVAL RATE OF TUMOR-BEARING MICE

  • 1 January 1981
    • journal article
    • research article
    • Vol. 41  (8) , 3217-3221
Abstract
The effect of treatment with the thymic factor thymostimulin (TP-1) on the survival rate of tumor-bearing mice was studied, using C57BL/6 mice inoculated with 1 .times. 105 Lewis lung carcinoma (3LL) cells. TP-1 given from inoculation day (4 mg/kg, twice weekly) caused a delay in the appearance of primary tumor [14.4 .+-. 1.1 (SE) days in control; 18.5 .+-. 1.4 days in TP-1-treated animals; P < 0.05], without changing ultimate survival rate. When primary tumor was resected, the incidence of fatal lung metastasis increased as a function of tumor size on resection day. TP-1 given after resection (same dose schedule) significantly increased survival rate as compared to resection only, provided that resected tumor diameter was < 1.7 mm. The combination of TP-1 and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU; single i.p. injection, 50 mg/kg) was effective in either resected or nonresected primary tumor. Without resection, TP-1 with CCNU cured (> 6 mo. free of tumor; untreated animals died within 30-44 days) 55% of the animals, as compared to 23% cured by CCNU alone (P < 0.01). With resection animal cure rates were as follows: resection (resected tumor diameter, 0.7-1.7 mm) alone, 42% cured; resection with CCNU, 47% cured; resection with TP-1, 70% cured; resection with CCNU and TP-1, 100% cured (last 2 groups significantly different from resection only). TP-1 apparently has a profound effect in prolonging life and increasing cure rate of tumor-bearing mice. This effect was manifested when tumor load was small and was apparently more pronounced on metastatic than on primary tumor.

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