Abstract 2838: Brief exposure to gefitinib/Iressa during premalignant risk window provides lifelong protection from mammary tumor development in MMTV-erbB-2 transgenic mice

Abstract Although chemopreventive agents targeting estrogen/estrogen receptor (ER) pathway have been effective for ER+ breast cancer, hormonal resistance associated with increased receptor tyrosine kinase activities, such as erbB-2 and/or EGFR, remains a significant issue in beast cancer prevention. Previous studies demonstrated that administration of gefitinib, an orally active EGFR tyrosine kinase inhibitor, to MMTV-erbB-2 transgenic mice inhibited mammary tumor development in these mice, suggesting that gefitinib is a promising agent for the prevention of ER-negative breast cancer. However, the prevention was achieved by high dose (100 mg/kg) and prolonged drug exposure (from 12 to 50 weeks). The tolerance to high dose/long-term of drug administration for the prevention regimens raised concerns in clinical application. In this study, we tested the efficacy of brief exposure to gefitinib during the high risk window in the prevention of mammary tumor development in the MMTV-erbB-2 transgenic mice and studied the underlying mechanisms. We found that brief exposure of gefitinib to these mice at a dosage of 100 mg/kg/day from 16 to 23 weeks (total 8 wks) resulted in significant chemopreventive effects. In contrast to no tumor-free animals in the control group by 52 weeks, mice in gefitinib treated group remained 65% tumor-free at the same age, which was comparable to the results from a previous report that mice with lifelong gefitinib were 75% tumor-free by 45 weeks. We further demonstrated that delayed tumor development in the treated mice was preceded with decreased mammary epithelial density. Molecular analysis indicated that gefitinib inhibited phosphorylation and expression of EGFR, erbB-3 and endogenous erbB-2 in premalignant mammary tissues. Phosphorylation of Akt1 and Erk1/2 was also significantly downregulated. Importantly, although tumors developed from this model were ER-, mammary tissues in the premalignant stage were ERα+; and gefitinib treatment drastically inhibited the phosphorylation and expression of ERα and the transcription of ER target genes, including EGF, EGFR, ESR1, Bcl-2, cyclin D1 and c-myc. Moreover, BrdU incorporation analysis demonstrates that cell proliferation in the mammary glands in gefitinib treated mice was significantly inhibited. Taken together, these data demonstrate that brief treatment with EGFR/erbB-2 targeting agents at the appropriate risk window may provide lifelong protection from mammary tumors, and inhibition of ER-erbB-2 crosstalk may play a critical role in this long lasting preventive process. Given the concerns associated with high dose/long-term gefitinib treatment, our findings are of great significance in directing clinical application of EGFR/erbB-2 targeting agents as chemopreventive agents. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2838. doi:10.1158/1538-7445.AM2011-2838</jats:p

Protection against Experimental Autoimmune Myocarditis Is Mediated by Interleukin-10-Producing T Cells that Are Controlled by Dendritic Cells

Experimental autoimmune myocarditis (EAM) can be induced in the Lewis rat by cardiac myosin or its cryptic S2-16 peptide epitope (amino acids1052 to 1076). To investigate cellular mechanisms and the role of antigen-presenting cells in regulation of myocarditis, we induced protection against EAM in Lewis rats by administration of S2-16 peptide in incomplete Freund’s adjuvant (IFA). Protection to EAM was associated with activation of S2-16-reactive splenocytes secreting high levels of interleukin (IL)-10 and reduced levels of interferon-γ and IL-2. Adoptive transfer of S2-16:IFA-induced splenocytes producing IL-10 suppressed myocarditis induction in syngeneic recipients, suggesting their regulatory cell nature. However, exposure of S2-16:IFA-induced cells to inflammatory cytokine IL-12 converted them to Th1 effectors that transferred EAM. Differentiated function of S2-16-reactive T cells in protected rats resulted from increased IL-10 production by dendritic cells (DCs). Purified DCs from S2-16:IFA-treated rats promoted S2-16-reactive CD4(+) T cells to produce increased IL-10 and reduced interferon-γ. In addition, adoptive transfer of IL-10-producing DCs from S2-16:IFA-treated rats also induced protection to EAM in recipient rats. These studies demonstrated DCs and key cytokines, such as IL-10 and IL-12, regulated the fate of T cells in myocarditis development in the Lewis rat