J Surg Res 1996 Jul 15;64(1):42-48
Recent studies suggest that expression of B7-1 by tumor cells is effective
at inducing antitumor immune responses. Our purpose was to transfect three
human cancer cell lines (MEWO, WM35, and H125) with a B7-1 expression plasmid
and test the immunogenicity of these modified cancer cells using allogeneic
human peripheral blood lymphocytes (PBLs). PBLs were tested in vitro for
both proliferative and cytotoxic activity against parental and B7-transfected
tumor cells. [3H]thymidine lymphocyte proliferation assays showed that
PBLs incubated with B7-1+ WM35 [major histocompatibility complex (MHC)
class I+II+ melanoma] demonstrated a substantial increase in T cell proliferation
(P < 0.0005), but PBLs incubated with B7-1+ MEWO (MHC class I-II- melanoma)
and H125 (MHC class I+II- lung adenosquamous carcinoma) did not. T-cell-mediated
cytotoxicity was not increased against B7-1+ tumor cells: effector T lymphocytes
primed against B7-1+ tumor cells did not show any increase in cytolytic
activity against 51Cr-labeled B7-1+ or B7-1- target cells. NK cells did
not lyse MEWO cells, but they did kill H125 and WM35 targets. B7-1 expression
on MEWO and WM35 cells did not result in enhanced lysis by NK cells, but
NK cytotoxicity was enhanced by B7-1 expression on H125 cells (P < 0.01).
The observation that NK cytotoxicity is enhanced by B7-1+ H125 cells suggests
that B7-1/CD28 interactions may be important in NK cytotoxic activity.
We conclude that B7-1+ WM35 cells, which express both MHC molecules and
antigenic epitopes, elicit an improved alloantigen-induced T cell proliferative
response, presumably because they have the capacity to deliver an adequate
antigen-specific signal which can be costimulated by B7-1/CD28 interaction.
Ann Surg Oncol 1996 May;3(3):317-324
BACKGROUND: Transfection of the costimulatory molecule B7-1 into some murine tumors can increase antitumor immunity and eradicate tumor growth. The purpose of this work was to construct an adenovirus-B7 (Ad-B7) expression vector and study B7-1 gene transfer into human cancer cells. METHODS: The human B7-1 cDNA was ligated into an expression cassette containing the human cytomegalovirus immediate early gene promoter and then inserted into the E1 region of the Ad5 genome by homologous recombination. The resulting Ad-B7 vector was used to infect established cancer cell lines and freshly resected cancers. Resected tumors were disaggregated into single cell suspensions by mechanical mincing and enzymatic digestion. Surface expression of B7-1 after infection was verified by flow cytometry. RESULTS: Expression kinetics in three cell lines showed that infected cells began to express B7-1 within 24 h. The proportion of B7-1+ cells continued to increase during the next 48 h, after which expression remained relatively constant during the next 5 days (up to 98% B7-1+ cells). Fresh tumor cells from various cancers displayed similar kinetics, but with greater variability in the proportion of cells expressing B7-1 (13% to 95% B7-1+ cells). Cancers which were successfully infected included 3 colorectal adenocarcinomas, 2 leiomyosarcomas, 2 lung squamous cell carcinomas, and 1 renal cell carcinoma. CONCLUSIONS: The Ad-B7 vector is a rapid and efficient means of gene transfer which does not require host cell proliferation. The ultimate objective is to engineer autologous tumors to express B7-1 and vaccinate cancer patients in an adjuvant or palliative setting.
PMID: 8726189, UI: 96292653