Evidence that the Elevated Levels of Proteinase Activity in the Plasma of Melanoma-Bearing Mice May Be of Host Origin

Abstract

C57B1/6 mice bearing the B16-F1 melanoma, an invasive variant (BL6) or a highly ‘metastatic’ variant (B16-F10) were found to develop elevated levels (200–300% of control) of neutral proteinase activity in their plasma during the progression of the disease. The magnitude of the level of proteinase activity detected was not dependent on tumor burden. Similar elevations in activity were detected with all 3 variants when they were transplanted either subcutaneously or intraperitoneally. However, transplantation of the B16-F10 line to the anterior chamber of the eye did not induce elevated plasma proteinase activity. Animals bearing intraocular tumors developed splenomegaly and lived the same length of time as animals bearing intraperitoneal or subcutaneous tumors. The development of increased levels of activity appeared to occur equally in male and female mice and was not dependent on the presence of a spleen, which undergoes enlargement during the disease process. These various lines of evidence support the hypothesis that the elevated level of plasma proteinase activity observed in melanoma-bearing mice is regulated by the host.

Differences between Beige and bg/+ Mice in the Disruption of Plasma Proteinase Regulation in the Tumor-Bearing State or following <i>Corynebacterium parvum</i> Treatment

“…Previous results obtained with both the BCLi leukemia [10] and the B16 melanoma [11][12][13] have led to the conclusion that host factors were central to the development of elevated levels of proteinase activity in tu mor-bearing animals. The strongest evidence was the finding that transplantation of the B16 melanoma to the anterior chamber of the eye failed to disrupt plasma proteinase regulation [12].…”

“…The B16-F10 cells were those used previously [11][12][13]. The cells were grown in vitro, washed three times with medium (RPMI-1640, Flow Laboratories), and then 10s cells were injected into a subcutaneous site on the flank.…”

“…The neutral proteinase activity in triplicate aliquots of plasma was determined as described previously [10][11][12][13][14][15] using l25I-casein. Brief ly, 25 pi of citrated plasma from each mouse was incubated with 75-100 pg l25I-casein (~ 150,000 cpm pg) for 3.5 h at 37 °C.…”

“…Transplantation of the B16 melanoma to a subcutaneous site on C57BL/6 mice leads to disruption of plasma proteinase homeo stasis by day 14, with maximal elevation occurring on approximately day 18 [11][12][13]. To determine whether the beige mutation in C57BL/6 mice could influence these changes, panels of beige mice and bg/+ het erozygote mice were transplanted with 105 B16-F10 cells.…”

“…Mice bearing transplantable tumors have recently been shown to develop elevated lev els of plasma proteinase activity [10][11][12], The onset of the disruption of homeostasis correlated with activation of the reticuloen dothelial system in these mice. In addition, the induction of elevation in plasma protein ase activity appeared to be regulated by host factors, since transplantation of tumors to an intraocular site did not result in disruption of homeostasis [12].…”