Interleukin-12 Inhibits Angiogenesis Induced by Human Tumor Cell Lines In Vivo

Abstract

Tumor cell-induced angiogenesis, i.e., new blood vessel formation within tumor tissue, is an essential requirement for the growth of solid neoplasms. Interleukin-12 (IL-12) inhibits growth of a variety of experimental tumors in vivo. We tested whether antitumor activity of IL-12 is related to the inhibition of angiogenesis induced by tumor cell lines. Angiogenesis was induced in x-ray immunosuppressed Balb/c mice by intradermal injection of the following human tumor cells: T47D, originating from mammary carcinoma; A431, derived from vulval carcinoma; and Skv, established from bowenoid papulosis, Systemic treatment of the mice with murine IL-12 significantly decreased angiogenesis induced by human tumor cells in a time-and dose-dependent manner. Preincubation of human cells in vitro with IL-12 did not inhibit tumor cell-induced angiogenesis, suggesting that the antiangiogenic capacity of IL-12 is restricted to in vivo conditions. Treatment of the mice with rat antibody against murine interferon-gamma (IFN-gamma) resulted in counteracting the antiangiogenic effect of murine IL-12. Furthermore, human IFN-gamma inhibited the angiogenic activity of human tumor cell lines. This indicates that IFN-gamma is a mediator of the antiangiogenic effect of IL-12. The results show that the mechanism of antitumor action of IL-12 may depend not only on the immunostimulatory activity of this cytokine but also on its effect on tumor cell-induced angiogenesis. IL-12 should be considered as a potential candidate for the treatment of angiogenesis-dependent malignancies.

Endogenous IL-12 triggers an antiangiogenic program in melanoma cells

“…The mechanisms of IL-12-mediated antitumor activity depend not only on activation of innate and adaptive effector immune mechanisms, but also on inhibition of angiogenesis (16)(17)(18). The latter is mediated by induction of IFN-␥, which in turn leads to release of the antiangiogenic chemokines CXCL9, CXCL10, and CXCL11.…”

“…IL-12, which is produced predominantly by antigen-presenting cells, drives T helper (Th1) responses, enhances T and natural killer (NK) cell cytotoxicity, and induces IFN-␥ production by T and NK cells (4,[7][8][9]. In addition, we have shown that IL-12 contributes to the regulation of normal human B cell function through stimulation of IgM synthesis and IFN-␥ production (10).IL-12 exerts antitumor activity through IFN-␥-dependent and independent mechanisms (11-15), which include modulation of the immune system and antiangiogenesis (16)(17)(18). We have recently demonstrated that the IL12RB2 gene acts as a tumor suppressor in human chronic B cell malignancies (14) and, accordingly, that aging IL12rb2 knockout (KO) mice develop spontaneously B cell tumors.…”

“…IL-12 exerts antitumor activity through IFN-␥-dependent and independent mechanisms (11)(12)(13)(14)(15), which include modulation of the immune system and antiangiogenesis (16)(17)(18). We have recently demonstrated that the IL12RB2 gene acts as a tumor suppressor in human chronic B cell malignancies (14) and, accordingly, that aging IL12rb2 knockout (KO) mice develop spontaneously B cell tumors.…”

Molecular basis of angiogenesis and cancer

“…In vivo studies demonstrated that the antitumor effect of recombinant IFN-b may be mediated, at least in part, via angiogenesis inhibition rather than antiproliferative activity (Hong et al, 2000) and that IFNa and retinoic acid have remarkably synergistic antiangiogenic effects able to inhibit both the growth and the neovascularization of head and neck squamous cell carcinoma injected into the floor of the mouth of nude mice (Lingen et al, 1998). Other in vivo studies evidenced that mice treated with rat antibody raised against murine IFN-g results in neutralizing the antiangiogenic effect of murine interleukin-12 (IL-12) (Majewski et al, 1996). This phenomenon indicates that IFN-g is a mediator of the antiangiogenic effect of IL-12 and that the mechanism of antitumor action of IL-12 may depend not only on the immunostimulatory activity of this cytokine but also on its effect on tumor cell-induced angiogenesis.…”

Construction of a recombinant adeno-associated virus (rAAV) vector expressing murine interleukin-12 (IL-12)

“…The mechanism by which IL-12 exerts this antitumor effect is not known, but is likely to involve a combination of activities including the modulation of T cell populations, stimulation of IFN-␥ production, and inhibition of angiogenesis. [37][38][39][40][41] A phase I gene therapy clinical trial employing a bicistronic retroviral vector expressing both human IL-12 subunits has been initiated in patients with metastatic cancer. 42 Adeno-associated viruses (AAV) are single-stranded DNA parvoviruses that offer several advantages over other gene transfer vectors.…”