title: Suppression of p53 function in normal human mammary epithelial cells increases sensitivity to extracellular matrix-induced apoptosis.
abstract: Little is known about the fate of normal human mammary epithelial cells (HMECs) that lose p53 function in the context of extracellular matrix (ECM)-derived growth and polarity signals. Retrovirally mediated expression of human papillomavirus type 16 (HPV-16) E6 and antisense oligodeoxynucleotides (ODNs) were used to suppress p53 function in HMECs as a model of early breast cancer. p53+ HMEC vector controls grew exponentially in reconstituted ECM (rECM) until day 6 and then underwent growth arrest on day 7. Ultrastructural examination of day 7 vector controls revealed acinus-like structures characteristic of normal mammary epithelium. In contrast, early passage p53- HMEC cells proliferated in rECM until day 6 but then underwent apoptosis on day 7. p53- HMEC-E6 passaged in non-rECM culture rapidly (8-10 passages), lost sensitivity to both rECM-induced growth arrest and polarity, and also developed resistance to rECM-induced apoptosis. Resistance was associated with altered expression of alpha3-integrin. Treatment of early passage p53- HMEC-E6 cells with either alpha3- or beta1-integrin function-blocking antibodies inhibited rECM-mediated growth arrest and induction of apoptosis. Our results indicate that suppression of p53 expression in HMECs by HPV-16 E6 and ODNs may sensitize cells to rECM-induced apoptosis and suggest a role for the alpha3/beta1-heterodimer in mediating apoptosis in HMECs grown in contact with rECM.
authors.affiliation: Division of Medical Oncology, Duke University, Durham, NC 27710, USA. seewa0001@mc.duke.edu
authors.forename: V L
authors.initials: VL
authors.lastname: Seewaldt
authors.forename: K
authors.initials: K
authors.lastname: Mrózek
authors.forename: R
authors.initials: R
authors.lastname: Sigle
authors.forename: E C
authors.initials: EC
authors.lastname: Dietze
authors.forename: K
authors.initials: K
authors.lastname: Heine
authors.forename: D M
authors.initials: DM
authors.lastname: Hockenbery
authors.forename: K B
authors.initials: KB
authors.lastname: Hobbs
authors.forename: L E
authors.initials: LE
authors.lastname: Caldwell
mesh_terms: D015703:Antigens, CD / Q000096:biosynthesis / Q000502:physiology; D017209:Apoptosis; D001940:Breast / Q000166:cytology; D015820:Cadherins / Q000096:biosynthesis; D002455:Cell Division; D002460:Cell Line; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D039422:Integrin alpha3; D019012:Integrin beta1 / Q000378:metabolism / Q000502:physiology; D016023:Integrins / Q000096:biosynthesis / Q000502:physiology; D007797:Laminin / Q000378:metabolism; D020319:Oligodeoxyribonucleotides, Antisense; D009856:Oncogene Proteins, Viral / Q000235:genetics / Q000378:metabolism; D027383:Papillomaviridae / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000502:physiology*
chemical_list: D015703:Antigens, CD; D015820:Cadherins; C068651:E6 protein, Human papillomavirus type 16; D039422:Integrin alpha3; D019012:Integrin beta1; D016023:Integrins; D007797:Laminin; D020319:Oligodeoxyribonucleotides, Antisense; D009856:Oncogene Proteins, Viral; D012097:Repressor Proteins; D016159:Tumor Suppressor Protein p53