Transient detection of beta-galactosidase activity in hematopoietic cells, following reinjection of retrovirally marked autologous blood progenitors in patients with breast or ovarian cancer receiving high-dose chemotherapy

Therapeutic utility of engineered myeloid cells in the tumor microenvironment

Despite promising results shown in hematologic tumors, immunotherapies for the treatment of solid tumors have mostly failed so far. The immunosuppressive tumor microenvironment and phenotype of tumor infiltrating macrophages are among the more prevalent reasons for this failure. Tumor associated macrophages (TAMs, M2-macrophages) are circulating myeloid cells recruited to the local tumor microenvironment, and together with regulatory T cells (T-regs), are reprogrammed to become immune suppressive. This results in the inactivation or hampered recruitment of cytotoxic CD8 + T and Natural Killer (NK) cells. Recently, attempts have been made to try to leverage specific myeloid functions and properties, including their ability to reach the TME and to mediate the phagocytosis of cancer cells. Additionally, myeloid cells have been used for drug delivery and reprogramming the tumor microenvironment in cancer patients. This approach, together with the advancements in genome editing, paved the way for the development of novel cell-mediated immunotherapies. This article focuses on the latest studies that detail the therapeutic properties of genetically engineered or pharmacologically modulated myeloid cells in cancer preclinical models, limitations, pitfalls, and evaluations of these approaches in patients with cancer.

Strategies to expand transduced hematopoietic stem cells in vivo

Data in mice suggest that in vivo selection strategies will expand the numbers of transduced hematopoietic stem cells (HSC) to levels sufficient for clinical therapies, and it is argued that comparable strategies will benefit larger animals and humans. To test this assumption, we performed virtual gene therapy in mouse and cat, species in which the in vivo kinetics of HSC are defined. In the simulated experiments, 10% of HSC and 50% of short-term repopulating cells were transduced with a gene allowing a conditional replication or apoptosis advantage. After transplantation, differentiation proceeded stochastically and contributions of transduced cells were tracked for 2 years. Fifty independent transplantations were simulated per species for each analysis. When transduced HSC had a 2-fold increased chance of replication (self-renewal) extending for 4, 10, or 20 weeks after transplantation, or a 5-fold replication advantage extending for 4 weeks, results in mice were far better than in cat, a larger animal, with slower baseline HSC cell cycle kinetics. Similarly, when transduced HSC had a 2-, 4-, or 10-fold decreased chance of apoptosis, extending for 20 or more weeks after transplantation, the murine studies were poor predictors of feline results. Simulation may allow one to optimize and/or understand the limitations of a gene therapy strategy.

Highly efficient lentiviral gene transfer in CD34+ and CD34+/38-/lin- cells from mobilized peripheral blood after cytokine prestimulation

Because mobilized peripheral blood (mPB) represents an attractive source of cells for gene therapy, we investigated lentiviral gene transfer in CD34(+) cells and the stem/progenitor-cell-enriched CD34(+)/38(-)/lin(-) cell subset isolated from mPB. In this study, we used an optimized third-generation self-inactivating lentiviral vector containing both the central polypurine tract and the woodchuck hepatitis posttranscriptional regulatory element sequences and encoding enhanced green fluorescent protein (EGFP) under the control of the elongation factor lalpha promoter. This lentivector was first used to compare multiplicity of infection (MOI)-dependent gene transfer efficiency in cord blood (CB) versus mPB CD34(+)-derived cells, colony-forming cells (CFCs), and long-term culture-initiating cells (LTC-ICs). Results showed a difference in the percentage of transduced cells particularly significant at low MOIs. A plateau was reached where 15% and 25% of CB and mPB cells, respectively, remained refractory to lentiviral trans-duction. Effects of a cytokine prestimulation period (18 hours) with interleukin-3, stem cell factor, Flt-3 ligand, and thrombopoietin were then analyzed in total cells, CFCs, and LTC-ICs derived from mPB CD34(+) cells. Transduction levels in those conditions demonstrated a two- and fourfold increase in CFCs and LTC-ICs, respectively, compared with unstimulated (<3 hours) control cells. Moreover, using the same transduction protocol, we were able to efficiently transduce CD34(+)/38(-)/lin(-) cells isolated from mPB, with up to >85% of colonies derived from LTC-ICs expressing EGFP and gene transfer levels remaining stable for 10 weeks in liquid culture. We therefore demonstrate a highly efficient gene transfer in this therapeutically relevant target cell population.

Endocrine aspects of cancer gene therapy

The field of cancer gene therapy is in continuous expansion, and technology is quickly moving ahead as far as gene targeting and regulation of gene expression are concerned. This review focuses on the endocrine aspects of gene therapy, including the possibility to exploit hormone and hormone receptor functions for regulating therapeutic gene expression, the use of endocrine-specific genes as new therapeutic tools, the effects of viral vector delivery and transgene expression on the endocrine system, and the endocrine response to viral vector delivery. Present ethical concerns of gene therapy and the risk of germ cell transduction are also discussed, along with potential lines of innovation to improve cell and gene targeting.