Evaluation of a clinical-grade, cryopreserved, ex vivo-expanded stem cell product from cryopreserved primary umbilical cord blood demonstrates multilineage hematopoietic engraftment in mouse xenografts.

BACKGROUND AIMS: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potentially curative therapy for a wide range of malignant and genetic disorders of the hematopoietic and immune systems. Umbilical cord blood (UCB) is a readily available source of stem cells for allo-HSCT, but the small fixed number of hematopoietic stem and progenitor cells (HSPCs) found in a single unit limits its widespread use in adult recipients. The authors have previously reported that culturing UCB-CD34+ cells in serum-free media supplemented with a combination of cytokines and the histone deacetylase inhibitor valproic acid (VPA) led to expansion of the numbers of functional HSPCs. Such fresh expanded product has been advanced to the clinic and is currently evaluated in an ongoing clinical trial in patients with hematological malignancies undergoing allo-HSCT. Here the authors report on the cryopreservation of this cellular product under current Good Manufacturing Practice (cGMP). METHODS: cGMP VPA-mediated expansion was initiated with CD34+ cells isolated from cryopreserved primary UCB collections, and the functionality after a second cryopreservation step of the expanded product evaluted in vitro and in mouse xenografts. RESULTS: The authors found that the cryopreserved VPA-expanded grafts were characterized by a high degree of viability, retention of HSPC phenotypic subtypes and maintenance of long-term multilineage repopulation capacity in immunocompromised mice. All cellular and functional parameters tested were comparable between the fresh and cryopreserved VPA-expanded cellular products. CONCLUSIONS: The authors' results demonstrate and support the practicality of cryopreservation of VPA-expanded stem cell grafts derived from UCB-CD34+ cells for clinical utilization.

OX40 ligation enhances primary and memory cytotoxic T lymphocyte responses in an immunotherapy for hepatic colon metastases.

Previously, we showed that the eradication of murine hepatic metastatic colon carcinomas was achieved by using a combination therapy with adenovirus-mediated gene delivery of interleukin 12 (IL-12) and anti-4-1BB agonistic antibody. However, the therapeutic efficacy was compromised severely when mice with tumors larger than 8 x 8 mm(2) were treated. In this report, we studied the effect of OX40 costimulation through agonistic anti-OX40 in combination with the IL-12 + anti-4-1BB immunotherapy on primary and memory anti-tumor cytotoxic T lymphocyte responses in a large-tumor setting (8 x 8 to 12 x 12 mm(2)). Tumor-infiltrating leukocytes (TILs) isolated from mice treated with the combination therapy of IL-12, anti-4-1BB, and anti-OX40 showed a significantly higher ex vivo direct cytotoxic T lymphocyte (CTL) activity against parental tumors, as compared with those from mice treated with IL-12 and anti-4-1BB. In vivo depletion of CD4(+)T cells during combination therapy significantly decreased the number of tumor-infiltrating CD8(+)T cells and their cytotoxic activity in mice treated with IL-12 + anti-4-1BB + anti-OX40 combination therapy but not in the group treated with IL-12 + anti-4-1BB, which indicated that in vivo OX40 engagement on CD4(+) T cells led to the higher CTL responses observed in animals treated with IL-12 + anti-4-BB + anti-OX40 combination therapy. Furthermore, the combination therapy of IL-12, anti-4-1BB, and anti-OX40 resulted in a significantly higher survival rate in treated mice, as compared with treatment with IL-12 and anti-4-1BB. More importantly, long-term surviving mice from the combination therapy with IL-12, anti-4-1BB, and anti-OX40 exhibited higher memory CTL responses against parental tumor cells. The results demonstrated that OX40 ligation of CD4(+) T cells facilitated the development of primary and memory CTL responses against tumorcells and that coordinated immune activation by IL-12, anti-4-1BB, and anti-OX40 resulted in a significantly higher survival rate in mice with large tumor burdens. Thus, the combination therapy with the adenovirus encoding IL-12 (Adv.mIL-12) + anti-4-1BB + anti-OX40 antibodies may provide a better treatment modality for patients with advanced cancers, often associated with a state of immune suppression or tolerance.