Retardation of Postsurgical Metastases With the Use of Extracted Tumor-Specific Transplantation Antigens and Cyclophosphamide<xref ref-type="fn" rid="FN1">2</xref><xref ref-type="fn" rid="FN3">3</xref>

Abstract

In a 3-methylcholanthrene [(MCA) CAS: 56-49-5]-induced tumor model of C3H/HeJ mice excision of a growing primary tumor decreased concomitant immunity and facilitated experimental lung metastases. Administration of tumor-specific transplantation antigens extracted from viable MCA-F cells with the use of single-phase (2.5%) 1-butanol [crude butanol extract (CBE)] augmented immunity after resection of the primary MCA-F tumor. Two weeks after footpad inoculation of 2 X 10(5) MCA-F cells, the tumor-bearing limbs were amputated and the mice were challenged subsequently with 5 X 10(4) cells of clone-9-4, a metastatic variant of MCA-F, via the tail vein. Whereas treatment with either 50 micrograms CBE sc or 20 mg cyclophosphamide (CY)/kg ip failed to retard lung colonization, combination therapy with the two agents reduced the incidence of lung colonies by 69.8% (26.5 vs. 8; P less than .001) compared with the incidence in the surgery-alone group and by 55.5% (18 vs. 8; P less than .001) compared with the incidence in the group treated with surgery and CY. Furthermore, the combined effects of CBE and CY were immunologically specific: The combined therapy with the non-cross-reactive MCA-D-CBE did not protect against iv challenge with clone-9-4. Treatment with antigenic extracts induced a 21.4% (4.2 vs. 3.3%) decrease in the ratio of Lyt 1+:Lyt 2+ cells in the spleens of tumor-resected mice, which suggested restoration to normal levels. Therefore, in the combined regimen, antigen may induce specific activation of helper lymphocytes, while CY inhibits activation of suppressor cells.