Exogenous cell-permeable C6 ceramide sensitizes multiple cancer cell lines to Doxorubicin-induced apoptosis by promoting AMPK activation and mTORC1 inhibition.

New chemotherapy-enhancing strategies are needed for better cancer therapy. Previous studies suggest that exogenous cell-permeable C6 ceramide may be a useful adjunct to the anti-tumor effects of chemotherapeutic agents (such as Taxol) against multiple cancers. Here we demonstrate that exogenous cell-permeable C6 ceramide largely sensitizes multiple progressive cancer cell lines to Doxorubicin-induced cell death and apoptosis. We found for the first time that Doxorubicin induces AMP-activated protein kinase (AMPK) activation in a reactive oxygen species-dependent manner. Activation of AMPK contributes to Doxorubicin-induced cancer cell death and apoptosis. Inhibition of AMPK by small interfering RNA knockdown or a pharmacological inhibitor reduces Doxorubicin-induced cancer cell apoptosis, whereas AMPK activator AICAR enhances it. Importantly, we found that C6 ceramide largely enhances Doxorubicin-induced activation of AMPK, which leads to mTOR complex 1 inhibition and chemo-sensitization. Our data suggest that the combination of C6 ceramide with traditional chemotherapy drugs such as Doxorubicin may have the potential to be used as a new therapeutic intervention against multiple cancers.

Therapeutic potential of non-adherent BM-derived mesenchymal stem cells in tissue regeneration.

We demonstrated that non-adherent BM cells (NA-BMCs) can be expanded in suspension and give rise to multiple mesenchymal phenotypes including fibroblastic, osteoblastic, chondrocytic and adipocytic as well as glial cell lineages in vitro using the 'pour-off' BMC culture method. Mesenchymal stem cells (MSCs) derived from NA-BMCs (NA-MSCs) from wild-type mice were transplanted into VDR gene knockout (VDR(-/-)) mice that had received a lethal dose of radiation. Results revealed that NA-MSC can be used to rescue lethally irradiated mice and become incorporated into a diverse range of tissues. After lethal dose irradiation, all untransplanted mice died within 2 weeks, whereas those transplanted with NA-MSCs were viable for at least 3 months. Transplantation rescued these mice by reconstructing a hematopoietic system and repairing other damaged tissues. WBC, RBC and platelet counts recovered to normal after 1 month, and VDR gene expression was found in various tissues of viable VDR(-/-) recipients. Adult BM harbors pluripotent NA-MSCs, which can migrate in vivo into multiple body organs. In an appropriate microenvironment, they can adhere, proliferate and differentiate into specialized cells of target tissues and thus function in damaged tissue regeneration and repair.