Adipose tissue-derived stromal cells primed in vitro with paclitaxel acquire anti-tumor activity.

Many strategies, including those based on genetically modified Mesenchymal Stromal Cells (MSCs), have been developed in recent years in order to obtain high concentrations of anticancer drugs effective on tumor mass. In previous studies, we showed that human and murine bone marrow-derived MSCs (BM-MSCs) and human skin-derived stromal fibroblasts (hSDFs) acquired strong anti-tumor capacity, both in vitro and in vivo, once primed with Paclitaxel (PTX). In this report we investigate whether adipose tissue-derived MSCs (AT-MSCs) behave similarly to BM-MSCs in their uptake and release of PTX in sufficient amounts to inhibit tumor proliferation in vitro. According to a standardized procedure, PTX primed AT-MSCs (AT-MSCsPTX) were washed and then subcultured to harvest their conditioned medium, which was then tested to evaluate its in vitro anti-tumor potential. We observed that AT-MSCsPTX were able to uptake PTX and release it in a time-dependent manner and that the released drug was active in vitro against proliferation of leukemia, anaplastic osteosarcoma, prostatic carcinoma and neuroblastoma cell lines. These data confirm that AT-MSCs, as well as BM-MSCs, can be loaded in vitro with anti-cancer drugs. While the harvesting of BM-MSCs requires invasive procedures, AT-MSCs can be prepared from fat samples taken with little patient discomfort. For this reason, this source of stromal cells represents an important alternative to BM-MSCs in developing new tools for carrying and delivering anti-cancer drugs into tumor microenvironments.

Assessment of human herpesvirus-6 infection in mesenchymal stromal cells ex vivo expanded for clinical use.

Infection or reactivation of human herpesvirus (HHV)-6 represents a potentially serious complication (often involving the central nervous system) in patients receiving either solid organ or hematopoietic stem cell transplantation. The objective of this study was to assess the risk of HHV-6 infection/reactivation in mesenchymal stromal cells (MSCs). MSCs are multipotent cells displaying immunomodulatory properties that have been already successfully used in the clinical setting to enhance hematopoietic stem cell engraftment and to treat steroid-refractory acute graft-versus-host disease. We analyzed 20 samples of ex vivo expanded MSCs, at different passages of culture, isolated both from bone marrow and from umbilical cord blood. Through Western blotting and immunocytochemistry techniques, we investigated the presence of the HHV-6 receptor (CD46) on cell surface, whereas the presence of HHV-6 DNA was evaluated by nested polymerase chain reaction assay. All of the MSC samples tested were positive for the virus receptor (CD46), suggesting their potential susceptibility to HHV-6. However, none of the MSC samples derived from cultures, performed in the perspective of clinical use, was found to harbor HHV-6. This preliminary observation on a consistent number of MSC samples, some of them tested at late in vitro passages, indicates a good safety profile of the product in terms of HHV-6 contamination. Nevertheless, it remains important to set up in vitro experimental models to study MSCs' susceptibility to HHV-6 (and HHV-7) infection, to verify their capacity to integrate the virus into cellular DNA, and to investigate which experimental conditions are able to induce virus reactivation.

In vitro toxicity of clozapine, olanzapine, and quetiapine on granulocyte-macrophage progenitors (GM-CFU).

INTRODUCTION: Atypical antipsychotics may lead to agranulocytosis because of the apoptosis caused by cells binding nitrenium molecules. Studies showing the direct myelotoxicity of clozapine were undertaken years ago using different assays, and thus it is difficult to compare them with those of clozapine's analogues that have been more recently reported as causing neutropenia, agranulocytosis, and thrombocytopenia. METHODS: We compared the direct toxicity of clozapine, olanzapine, quetiapine, and chlorpromazine using a previously standardized GM-CFU assay validated for predicting neutropenia. RESULTS: The results showed that all of the drugs were characterized by dose-dependent toxicity, which was greatest in the case of chlorpromazine (IC90 = 10.02 +/- 0.69 microg/mL), followed by olanzapine (IC90 = 13.43 +/- 1.23 microg/mL), clozapine (IC90 = 44.71 +/- 4.42 microg/mL), and quetiapine (IC90 = 137.24 +/- 15.36 microg/mL). DISCUSSION: These data agree with recent clinical reports concerning the direct or mediated toxic effects of olanzapine on progenitor and committed cells (GM-CFU) and suggest that the correlation between its plasma levels and clinical effects warrants further investigation. There are no published data concerning the bone marrow pharmacokinetics of atypical antipsychotics or their possible bioactivation by the bone marrow cell compartment, but our findings suggest that they may affect hematopoiesis in different ways, such as the direct action of them or their metabolites due to bioactivation by hematopoietic cells themselves.