The inhibitor of the apoptosis protein (IAP) survivin is expressed in proliferating cells such as fetal tissues and cancers. We previously reported that survivin is expressed and growth factor regulated in normal adult CD34 ؉ cells. Herein, we examined survivin expression in CD34 ؉ cells before and after cell cycle entry and demonstrate a role for survivin in cell cycle regulation and proliferation. Analysis of known human IntroductionApoptosis and cell cycle regulation are tightly orchestrated processes involving multiple effector molecules. [1][2][3] Pathways that regulate cell cycle and cell survival overlap, but distinct mechanisms are involved. 4,5 The inhibitor of apoptosis protein (IAP) family proteins inhibit apoptosis by inactivating several caspases. There are 7 known IAP family proteins: NAIP, 6,7 XIAP, 7 c-IAP1, 7-9 c-IAP2, 7,8 survivin, 10,11 livin, 12 and murine Bruce 13 and its human homolog, Apollon. 14 Survivin and livin are frequently overexpressed in cancer cells and fetal tissues but are barely detectable in adult quiescent tissues. [10][11][12]15 While most IAPs block apoptosis, 3,8,12,16,17 their roles in cell cycle regulation are unclear.We recently reported that survivin is expressed and cytokine regulated in normal adult marrow CD34 ϩ cells, umbilical cord blood (UCB) CD34 ϩ cells, and adult peripheral blood T cells. 18 Survivin blocks caspase-3 activity and inhibits apoptosis in cancer cells, 11,15,16,[19][20][21] and an inverse correlation between survivin and active caspase-3 expression was observed in CD34 ϩ cells. 18 Survivin expression in cytokine-stimulated CD34 ϩ cells was associated with cell cycle progression, being highest in G 2 /M. However, in contrast to expression occurring only during G 2 /M in cancer cells, 15 survivin is expressed in all phases of the cell cycle in cytokine-stimulated CD34 ϩ cells. 18 These studies indicate that survivin is not a cancer-specific protein and suggest that survivin plays a role in the proliferation and survival of normal hematopoietic cells.Since most proliferating cells express survivin, including cancer cells, 10,11,15 normal T cells, 18 and normal CD34 ϩ cells, 18 it is unclear whether survivin is expressed simply because cells are dividing or whether survivin expression directly affects cell cycle progression and proliferation. Since survivin interacts with the cdk4/cyclin D complex and enhances Rb phosphorylation 4,22,23 and overexpression of survivin enhances cell cycle progression in hepatoma cells, survivin may be involved in cell cycle regulation, at least in cancer cells. 24 Our previous findings that survivin is found in G 0 CD34 ϩ cells after growth factor stimulation for 48 hours 18 raised the question of whether up-regulation of survivin by growth factors occurs in quiescent G 0 CD34 ϩ cells before they enter G 1 .In this study, we examined whether IAPs in general, and survivin in particular, are expressed and growth factor regulated in normal CD34 ϩ cells. Using real-time reverse transcriptionpolymerase chain reaction (RT-P...

CKβ-11 chemoattracts T cells, B cells, dendritic cells, macrophage progenitors, and NK cells and facilitates dendritic cell and T cell interactions in secondary lymphoid tissues. We hypothesized that expression of CKβ-11 in tumor cells may generate antitumor immunity through these interactions. After transduction with the retroviral vector L(CKβ11)SN, the murine breast cancer cell line C3L5 (C3L5-CKβ11) showed expression of retroviral mRNA by Northern analysis and production of functional CKβ-11 by chemotaxis of human NK cells to C3L5-CKβ11 supernatant. Only 10% of mice injected with C3L5-CKβ11 developed tumors, compared with 100% of mice injected with a transduced control C3L5 line (C3L5-G1N). Importantly, the in vitro growth characteristics of the CKβ-11-transduced cell line were unaffected, suggesting the difference in growth in vivo was a result of chemokine production. Vaccination with C3L5-CKβ11 partially protected animals from parental C3L5 challenge. Immunodepletion with anti-asialo-GM1 or anti-CD4 during C3L5-CKβ11 vaccination significantly reduced CKβ-11 antitumor activity compared with control and anti-CD8-treated groups. Splenocytes from NK-depleted animals transferred the acquired immunity generated with C3L5-CKβ11 vaccination, while splenocytes from the CD4-depleted animals did not. These results indicate, for the first time, that expression of CKβ-11 in a breast cancer cell line mediates rejection of the transduced tumor through a mechanism involving NK and CD4+ cells. Furthermore, CKβ-11-transduced tumor cells generate long-term antitumor immunity that requires CD4+ cells. These studies demonstrate the potential role of CKβ-11 as an adjuvant in stimulating antitumor responses.