Effect of antiestrogens on EGF-mediated movement of human breast cancer cells.

In a previous study we compared the influence of several growth factors on breast cancer cells in culture and observed that epidermal growth factor (EGF) enhanced the invasiveness of estrogen receptor-positive breast cancer cells. The objective of the present study was to determine the influence of three unique antiestrogens on EGF-mediated movement of human breast cancer cells. The rate of movement of MCF-7 breast cancer cells was measured using time-lapse videomicroscopy (TLVM). The MCF-7 cells were pretreated with antiestrogen (either tamoxifen, ICI-182-780 (ICI) or 1,1-dichloro-cis-2,3-diarylcyclopropane (AII)) at 10(-6) mol/l for 4 days, and then treated with EGF (10(-10) mol/l) immediately prior to TLVM. EGF enhanced the motility of the MCF-7 cells at 30-90 min post-administration. However, EGF-mediated motility of the MCF-7 cells was inhibited by antiestrogen pretreatment, with TAM and ICI producing complete inhibition of EGF-induced motility. In conclusion, this study demonstrates that EGF enhances the rate of movement of MCF-7 breast cancer cells and that antiestrogen pretreatment inhibits EGF-mediated motility.

rab7 activity affects epidermal growth factor:epidermal growth factor receptor degradation by regulating endocytic trafficking from the late endosome.

The epidermal growth factor receptor (EGFR) is a member of the receptor tyrosine kinase family. Ligand (epidermal growth factor or EGF) binding to the EGFR results in the coordinated activation and integration of biochemical signaling events to mediate cell growth, migration, and differentiation. One mechanism the cell utilizes to orchestrate these events is ligand-mediated endocytosis through the canonical clathrin-mediated endocytic pathway. Identification of proteins that regulate the intracellular movement of the EGF.EGFR complex is an important first step in dissecting how specificity of EGFR signaling is conferred. We examined the role of the small molecular weight guanine nucleotide-binding protein (G-protein) rab7 as a regulator of the distal stages of the endocytic pathway. Through the transient expression of activating and inactivating mutants of rab7 in HeLa cells, we have determined that rab7 activity directly correlates with the rate of radiolabeled EGF and EGFR degradation. Furthermore, when inhibitory mutants of rab7 are expressed, the internalized EGF.EGFR complex accumulates in high-density endosomes that are characteristic of the late endocytic pathway. Thus, we conclude that rab7 regulates the endocytic trafficking of the EGF.EGFR complex by regulating its lysosomal degradation.

A Comparison of KGF Receptor Expression in Various Types of Human Cancer.

BACKGROUND: Keratinocyte growth factor (KGF) has been observed to produce a rapid increase in the motility of breast cancer cells. KGF/KGFR (KGF receptor) signaling has also been demonstrated in the progression of many types of human cancer. The objective of the present study was to compare KGFR expression in various types of cancer. MATERIALS AND METHODS: A cancer profiling array containing cDNA from 154 tumor and paired normal samples representing 19 types of human cancer was employed. RESULTS: The results of the present study indicate that KGFR expression is enhanced in many types of human carcinomas at an early stage of cancer development, suggesting that KGFR overexpression may be an early signal in the progression of these cancers. However, the stage of cancer progression and relative level of expression varied considerably among the various types of cancer. CONCLUSION: These findings suggest that tumor KGFR levels may serve as a prognostic biomarker for cancer staging and/or treatment.