ABSTRACT
A second adenomatous polyposis coli (APC)-like gene, APC2/APCL, was recently described and localized to chromosome 19. We have fine mapped APC2 to a small region of chromosome 19p13.3 containing markers D19S883 and WI-19632, a region commonly lost in a variety of cancers, particularly ovarian cancer. Interphase fluorescence in situ hybridization analysis revealed an APC2 allelic imbalance in 19 of 20 ovarian cancers screened and indicates that APC2 could be a potential tumor suppressor gene in ovarian cancer. When overexpressed in SKOV3 ovarian cancer cells, which express low levels of APC2, exogenous APC2 localized to the Golgi apparatus, actin-containing structures, and occasionally to microtubules. Antibodies against the NH2 terminus of human APC2 show that endogenous APC2 is diffusely distributed in the cytoplasm and colocalizes with both the Golgi apparatus and actin filaments. APC2 remained associated with actin filaments after treatment with the actin-disrupting agent, cytochalasin D. These results suggest that APC2 is involved in actin-associated events and could influence cell motility or adhesion through interaction with actin filaments, as well as functioning independently or in cooperation with APC to down-regulate beta-catenin signaling.
Subject(s)
Allelic Imbalance , Cytoskeletal Proteins/genetics , Cytoskeletal Proteins/metabolism , Actin Cytoskeleton/metabolism , Animals , Breast Neoplasms/genetics , Breast Neoplasms/metabolism , Chromosomes, Human, Pair 19/genetics , Cytoskeletal Proteins/biosynthesis , Dogs , Female , Gene Expression , Genes, APC , Genes, Tumor Suppressor , Golgi Apparatus/metabolism , Humans , In Situ Hybridization, Fluorescence , Ovarian Neoplasms/genetics , Ovarian Neoplasms/metabolism , Radiation Hybrid Mapping , Transfection , Tumor Cells, CulturedABSTRACT
Ligands of the EGF/Heregulin family control the growth of epithelial cells by binding to receptors of the erbB family. By searching a large database of cDNA sequences at Human Genome Sciences Inc. we have identified a new encoded protein sequence containing all the conserved elements of the EGF/Heregulin family. The same sequence has recently been independently identified as NRG-3. The EGF-like domain of NRG-3 was generated as a recombinant protein in E. coli and used to test the specificity of receptor binding. In human breast cancer cells and in 32D cells transfected by erbB family members, NRG-3 activated multiple erbB family members. These include EGF receptor (erbB1) and erbB4 when expressed individually and erbB2 and erbB3 when expressed together. Recombinant NRG-3 altered the growth of human breast cancer cells growing in vitro. NRG-3 was expressed in cell lines derived from breast cancer. These results indicate that NRG-3 is a potential regulator of normal and malignant breast epithelial cells in vivo.
