Sf. Alino et al., ANTIMETASTATIC EFFECT OF IMMUNIZATION WITH LIPOSOME-ENCAPSULATED TUMOR CELL-MEMBRANE PROTEINS OBTAINED FROM EXPERIMENTAL-TUMORS, Immunopharmacology and immunotoxicology, 17(3), 1995, pp. 419-436
Immunization of C57BL/6 mice with tumor-derived membrane-proteins enca
psulated in sized liposomes (0.2 mu g/mouse) and composed by phosphati
dylcholine or sphingomyelin, significantly reduced the mean values of
spontaneous lung metastasis from both B16 (0.7 +/- 0.5 and 1.2 +/- 0.6
, respectively) and 3LL (4.8 +/- 2.5 and 7.2 +/- 4.1, respectively) tu
mors, with respect to control (HEPES) groups (4.8 +/- 1.1 and 19.0 +/-
4.4, respectively). However, no significant antimetastatic effect was
observed using free tumor-derived proteins (2 mu g/mouse) or liposome
vehicle alone. Specific humoral immune response after the vaccination
was studied by flow cytometry of tumor cells incubated with a pooled
sample from each group of immunized mice and FITC-conjugate antimouse
immunoglobulins. The results showed that the highest number of positiv
e tumor cells was identified using sera from immunized mice with sized
liposomes encapsulating tumor-derived proteins whereas the immunizati
on with the protein fraction in free form failed to induce this effect
. In addition, an increased cytotoxicity towards 3LL and B16 tumor cel
ls can also be observed when tumor cells were incubated with spleen ef
fector cells plus specific immunosera. In conclusion, our results show
that antitumor active vaccination, using sized liposomes as adjuvants
, induces an antitumor host response and a significant inhibition of t
umor progression.