Am. J. Respir. Cell Mol. Biol.,
Volume 20, Number 5, May, 1999 935-941
Adenovirus-Mediated Expression of Interleukin-12 Induces Natural
Killer Cell Activity and Complements Adenovirus-Directed gp75
Treatment of Melanoma Lung Metastases
Edward A.
Hirschowitz
and
Ronald G.
Crystal
Division of Pulmonary and Critical Care Medicine, New York Hospital-Cornell Medical Center,
New York, New York
Based on the knowledge that adenovirus (Ad)-mediated expression of the murine gp75 melanoma antigen
(Adgp75) will effectively immunize mice against H2-matched B16 melanoma cells, probably via cell-
mediated immune mechanisms, we hypothesized that Ad-mediated delivery of the murine interleukin-12
(IL-12) complementary DNA heterodimer would have independent therapeutic effects on tumor growth,
and that the combination of the two vectors would work synergistically to augment the antitumor response.
We evaluated the therapeutic effect of each vector alone and in combination for efficacy in C57BL/6 mice
with preestablished (2 d) B16 melanoma-derived pulmonary metastases, using the number of lung metastases as the efficacy parameter. Intraperitoneal administration of Adgp75 (108 PFU) reduced tumor burden to 45 ± 7% of controls (P < 0.01), and AdIL12 administration (108 PFU, intraperitoneally) reduced
the number of metastases to 43 ± 7% of controls (P < 0.01). The combination of Adgp75 (108 PFU, intraperitoneally) and AdIL12 (108 PFU, intraperitoneally) provided further protection (15 ± 3%; P < 0.01 as
compared with naive control; P < 0.01 compared with Adgp75 or AdIL12 alone). Mice receiving AdIL12
showed increased natural killer cell (NK cell) function in an in vitro cytotoxicity assay, with a dose-
dependent lysis of YAC-1 cells and, to a lesser extent, lysis of B16 cells. To assess the relative contribution of major histocompatibility complex I (MHC I) Dependent and Independent activity in combination
therapy with Adgp75 plus AdIL12, we performed adoptive transfer experiments, using splenocytes from
mice receiving Adgp75, AdIL12, or Adgp75 + AdIL12, from among which NK cells had been selectively
depleted in vitro prior to adoptive transfer. Each group showed significant decreases in tumor burden resembling those with primary treatment. Interestingly, NK-cell depletion from among cells derived from
the Adgp75- and AdIL12-treated mice significantly altered the therapeutic response (P < 0.01 compared with the Adgp75 + AdIL12 group), suggesting a significant role of NK-cell-mediated cytolysis in vivo,
although there was still a significantly reduced tumor burden (P < 0.01 compared with that of naive controls). Collectively, these data support the concept that the combination of AdIL12 and Adgp75 provides
additive effects against pulmonary metastases of B16 melanoma by MHC-independent (NK cell) means as
well as MHC-dependent cytotoxic lymphocyte means, suggesting that this therapy may be a useful adjuvant in the treatment of metastatic melanoma.
