ABSTRACT
BACKGROUND: Although antiestrogens have been effective in preventing estrogen receptor (ER)-positive breast cancer, chemopreventive agents are still needed to prevent ER-negative breast cancer. Tyrosine kinase inhibitors are promising agents for the treatment and prevention of human cancers. ZD1839 (gefitinib or Iressa) is an orally active epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor that blocks signal transduction pathways in epithelial cells. We examined whether ZD1839 blocks signal transduction and prevents the development of ER-negative breast cancer. METHODS: The ability of ZD1839 to block signal transduction in normal, immortalized, and malignant breast cells was assessed by western blotting with specific antibodies to detect phosphorylation of cytoplasmic signaling molecules. The effect of ZD1839 on growth of these breast cells was assessed with anchorage-dependent and anchorage-independent growth assays. Its effect on ER-negative mammary tumorigenesis was assessed in MMTV-erbB2 transgenic mice. All statistical tests were two-sided. RESULTS: ZD1839 suppressed the phosphorylation of EGFR and mitogen-activated protein kinase in normal and malignant breast cells. ZD1839 treatment statistically significantly suppressed mammary tumorigenesis in MMTV-erbB2 transgenic mice; median time to tumor development was approximately 230 days in vehicle-treated mice and more than 310 days in mice treated with ZD1839 at 100 mg/kg (P<.001). ZD1839 reduced proliferation of normal breast cells by 20.3% (95% confidence interval [CI] = -13.7% to 44.2%) and of tumor cells by 42.0% (95% CI = 20.2% to 58.2%). ZD1839 also increased expression of the cell cycle regulator p27 in normal mammary tissue by 48.7% (95% CI = 27.0% to 74.2%) and in tumor tissue by 50.3% (95% CI = 35.8% to 66.7%). CONCLUSION: This study appears to provide the preclinical rationale for the development of these EGFR tyrosine kinase inhibitors for the prevention of human breast cancer.
Subject(s)
Anticarcinogenic Agents/pharmacology , Antineoplastic Agents/pharmacology , Breast Neoplasms/drug therapy , Breast Neoplasms/prevention & control , Enzyme Inhibitors/pharmacology , ErbB Receptors/antagonists & inhibitors , Mitogen-Activated Protein Kinases/antagonists & inhibitors , Muscle Proteins , Quinazolines/pharmacology , Receptors, Estrogen/metabolism , Animals , Blotting, Western , Breast Neoplasms/metabolism , Cell Line , Cell Line, Tumor , Epithelial Cells , ErbB Receptors/metabolism , Female , Gefitinib , Gene Expression Regulation, Neoplastic/drug effects , Genes, erbB-2/drug effects , Humans , Mice , Mice, Transgenic , Microfilament Proteins/analysis , Phosphorylation/drug effects , Precancerous Conditions/drug therapy , Precancerous Conditions/prevention & control , Signal Transduction/drug effectsABSTRACT
In these experiments, the effects of the drying history of hydrogels made from a novel polymer, oligo(poly(ethylene glycol) fumarate) (OPF) with two different poly(ethylene glycol) (PEG) molecular weights (approximately 920 (1K) and 9110 (10K) g/mol), were investigated. The hydrogels were either formed, dried and then swelled, representing what may occur in the case of a pre-formed membrane for guided tissue regeneration, or were formed and swelled immediately, as may occur with an injectable material for such applications. Subsequently, swelling properties, sol fraction and polymer network structure (as indicated by differential scanning calorimetry), as well as attachment of human dermal fibroblasts to these hydrogels at 4 and 24 h was examined. It was found that drying before swelling caused a significant reduction in final fold swelling of OPF hydrogels, regardless of OPF formulation or method of drying (air-dried or vacuum-dried) (e.g. PEG 10K swollen first: 13.94 +/- 0.35 vs. vacuum first: 6.53 +/- 0.12; PEG 1K swollen first: 8.99 +/- 0.47 vs. vacuum first: 2.26 +/- 0.08). This decreased swelling correlated to significantly higher cell attachment (% seeded) to these hydrogels at 24 h (PEG 10K vacuum first: 21.1 +/- 4.7% vs. swollen first: 7.1 +/- 5.5%; PEG 1K vacuum first: 58.2 +/- 2% vs. swollen first: 7.4 +/- 2.2%). LIVE/DEAD staining followed by microscopic analysis revealed attached cells were viable, yet rounded, and that, in the case of the PEG 1K dried-first samples, undulations in the surface visible in the hydrated state may have affected cell adhesion. Regardless of treatment, all hydrogels showed significantly less cell attachment than the tissue culture polystyrene control after 24 h (104.9 +/- 4.4%). These results suggest that, by altering the PEG molecular weight used in synthesis, OPF hydrogels may be tailored to produce desired swelling properties and reduce non-specific cell adhesion for either injectable or pre-formed applications, thus providing a potential alternative material for use in guided tissue regeneration procedures.
