Fig. 8. Expression of CBP in late passage HMEC-E6 cells promotes growth regulation and apoptosis in rECM culture. (A,B) Exogenous expression of CBP in apoptosis-resistant late passage HMEC-E6 cells results in decreased growth in rECM culture. (A) Ki-67 staining indices in late passage HMEC-E6 cells (passage 17) expressing exogenous CBP (CBP(+)) or transduced with the LXSN control vector (CBP(–)). (B) The number of nuclei per cell cluster formed by late passage HMEC-E6 cells (passage 17) expressing exogenous CBP (CBP(+)) or transduced with the LXSN control vector (CBP(–)). Two hundred cells were surveyed per time point and indices were calculated from an average of three independent experiments. Error bars show standard error. (C,D) Electron micrographs of late passage HMEC-E6 cells (passage 17) expressing exogenous CBP ((+)CBP) or transduced with the LXSN control vector ((–)CBP) grown in rECM for 7 days. Late passage HMEC-E6-CBP(–) control cells formed large, dense, irregularly shaped, multicellular colonies that have no central lumen (C). By contrast, late passage HMEC-E6-CBP⁺ cells underwent apoptosis when grown in rECM for 7 days (D) as shown by (1) nuclear condensation (n), (2) cell shrinkage and separation, and (3) margination of chromatin (mr). (E) Percentage of apoptotic cells in late passage HMEC-E6 cells (passage 16) expressing exogenous CBP (CBP(+)) or transduced with the LXSN control vector (CBP(–)). Apoptosis was measured by TUNEL-staining. Apoptotic index was measured by calculating the percentage of TUNEL-stained cells relative to the total number of cells surveyed. Data represents an average of three independent experiments. Error bars show standard error.