Rat TNF-Related Apoptosis-Inducing Ligand (rTRAIL)-Expressing Rat-Adipose-Derived Stem Cells (rADSC) Moderately Limit Growth of Rat Mammary Cancer Cells-A Pilot Study.

BACKGROUND

Adipose-derived stem cells (ADSCs) are readily harvestable, tumour-homing cells that have been engineered as vehicles for antitumour agents. TNF-related apoptosis-inducing ligand (TRAIL) selectively triggers apoptosis in many cancer cells through death receptors DR4/DR5, while sparing most healthy cells. To date, only human TRAIL has been studied in such delivery systems; a fully homologous rat model (rat TRAIL delivered by rat ADSC) has not been tested, despite being essential for future syngeneic in vivo studies.

METHODS

In this pilot, exploratory study, we lentivirally transduced rat ADSC (rADSC) to express myc-tagged rat TRAIL, characterized the expression of TRAIL-pathway components in rADSC and three rat mammary carcinoma cell lines (RBA, HH-16.cl.4, SHZ-88) at the mRNA and protein levels, and assessed the antitumour effect of rTRAIL-rADSC using recombinant TRAIL dose-response, supernatant transfer, direct co-culture, and nine-day insert co-culture assays.

RESULTS

rADSCs were successfully transduced and produced cell-associated rat TRAIL (66.2 pg per 50,000 cells versus 4.4-5.7 pg in controls; p < 0.05); this ELISA measures total cell-associated (intracellular plus membrane-anchored) TRAIL rather than soluble TRAIL. rADSC expressed markedly higher levels of the decoy molecule osteoprotegerin and of DR4/DR5 than the cancer cells. Two of three cancer lines (RBA, HH-16.cl.4) were susceptible to rat TRAIL, and rTRAIL-rADSC reduced their growth and increased the proportion of dead cells, with morphological features compatible with both apoptosis and necrosis, most markedly in HH-16.cl.4; the effect was separable from the empty-vector control in HH-16.cl.4 but not in RBA.

CONCLUSIONS

In this pilot study, homologous rat TRAIL delivered by rADSC is feasible and increases cell death in TRAIL-susceptible rat mammary cancer cells, but the effect is moderate at most, contact-dependent, and in one of two susceptible lines not attributable to TRAIL itself. These findings define both the potential and the limitations of a fully translational rat model of TRAIL-based biologic brachytherapy and provide a foundation for future in vivo studies.