The composition of
gangliosides was studied in four
fibrosarcomas (FL, FLA, FLB, FLC) induced in the Lewis rat by
Ferridextran, and in two clones of a spontaneous Lewis rat mammary
sarcoma (C-1-SAM LEW and C-2-SAM LEW) and two supertransformed clones (S-174 and S-271) derived from these clones, using the B77 virus. The
malignancy of the Lewis
tumors was tested in terms of their ability to outgrow the RT-5 barrier in LEW.1x rats and expressed as the loss-rate of LEW.1x rats. As for the
Ferridextran-induced
tumors, the FL was the only one to have been rejected in nearly 100% of the LEW.1x recipients. Following presensitization with FL the other
tumors were also rejected, though not at a rate of 100%. The rat loss-rate was: FL--0%, FLC--23.5%, FLB--36.5%, and FLA--82.6%. As
malignancy increased, the composition of
gangliosides showed signs of progressive simplification indicating a step-by-step repression of
ganglioside biosynthesis involving first the disialoganglioside and subsequently also the monosialoganglioside pathways. Some less distinct decrease (but significant at the 5% level of probability) of
gangliosides of the disialoganglioside pathway and an increase of the simplest
ganglioside (GM3) were observed between the C-1 clone of SAM LEW and its S-174 supertransformant. However, the changes, especially in the C-2 clone and its supertransformant, were not such as would suggest a marked defect in the biosynthesis of
gangliosides.