The Role of Interferon Regulatory Factor-1 and Interferon Regulatory Factor-2 in IFN-γ Growth Inhibition of Human Breast Carcinoma Cell Lines

Interferon (IFN) regulatory factor-1 (IRF-1) and IRF-2 play opposing roles in the regulation of many IFN-γ-inducible genes. To investigate the signal transduction pathway in response to IFN-γ in light of differences in growth effects, we selected four human breast carcinoma cell lines based on a spectrum of growth inhibition by IFN-γ. MDA468 growth was markedly inhibited by IFN-γ, and it showed substantial induction of IRF-1 mRNA but little IRF-2 induction. SKBR3 showed little growth inhibition and little induction of IRF-1 mRNA but significant induction of IRF-2 mRNA. HS578T and MDA436 growth inhibition and IRF-1/IRF-2 induction were intermediate. All four cell lines showed intact receptor at the cell surface and Stat1 translocation to the nucleus by immunostaining. By EMSA, there were marked differences in the induced ratio of IRF-1 and IRF-2 binding activity between the cell lines that correlated with growth inhibition. Finally, antisense oligonucleotides specific for IRF-1 attenuated IFN-γ growth inhibition in MDA436 and MDA468, confirming the direct role of IRF-1 in IFN-γ growth inhibition. Induction of IRF-1 causes growth inhibition in human breast cancer cell lines, and induction of IRF-2 can oppose this. The relative induction of IRF-1 to IRF-2 is a critical control point in IFN-γ response.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63111/1/10799900360708623.pd

Direct Intratumoral Injection of an Adenovirus Expressing Interleukin-12 Induces Regression and Long-Lasting Immunity That Is Associated with Highly Localized Expression of Interleukin-12

http://www.liebertonline.comReproduced by generous permission of the publisher.Mice bearing breast tumors were treated with a single dose of an adenovirus expressing interleukin-12 (AdmIL-12.1) injected intratumorally, which produced regressions in greater than 75% of the treated tumors; approximately one-third of the animals remained tumor free. Complete regression was associated with immunity to secondary challenge with fresh tumor cells. Analysis of local cytokine expression demonstrated maximum expression of IL-12 within the tumor between 24 and 72 hr post-injection, reaching 600-800 ng per tumor, with elevated local levels of IL-12 detectable for at least 9 days. This expression was highly localized as serum IL-12 peaked at 40-60 ng/ml at 24 hr and was less than 10 ng/ml from day 3 onward. Interferon-gamma (IFN-gamma) concentrations were markedly increased within the tumor following AdmIL-12.1 administration, demonstrating that IL-12 was acting locally. Tumor-draining lymph node cells spontaneously produced IFN-gamma following AdmIL-12.1 treatment, suggesting these cells were activated by IL-12. These data demonstrate that AdmIL-12.1 can be used to deliver very high levels of localized cytokine production. Moreover, we have confirmed that the IL-12 produced from our vector actually affects the local cytokine environment of the tumor and activates responder cells present within the tumor