Fig. 3

In vivo suicide gene therapy using eGFP-fLuc-HSV-TK (+), ihSPIO-labeled mOct4⁻ BM-MAPCs in a mouse glioblastoma model. a Hypointense signal volume determination (three-dimensional T2* MRI) on 1 % labeled mOct4⁻ BM-MAPCs did not show statistically significant differences between stem cell injected animals (phosphate-buffered saline (PBS)/ganciclovir (GCV)) and sham-operated animals (SHAM) 1 day after surgery (day 16). At the end of treatment (day 30), there was, however, a significant difference between sham-operated animals and GCV-treated animals (**p < 0.01) due to the smaller tumor sizes in the GCV-treated group. In the sham-operated and PBS-treated group, tumor formation was present which is accompanied with necrosis and bleedings when tumors grow over time. In contrast, the hypointense signal in the GCV-treated group, which did not develop tumors, is mostly generated by remaining labeled mOct4⁻ BM-MAPCs. b Hypointense signal volume determination (three-dimensional T2* MRI) on 10 % labeled mOct4⁻ BM-MAPCs showed statistically significant differences between stem cell injected animals (PBS/GCV) and sham-operated animals 1 day after surgery (day 16). At the end of treatment (day 30), there was a statistically significant difference between sham-operated and PBS-treated animals and between the PBS-treated and GCV-treated groups. *p < 0.05, **p < 0.01, ***p < 0.001. c MR images of one representative animal stereotactically injected with 1 % or 10 % labeled mOct4⁻ BM-MAPCs showed that the hypointense contrast, delineated in red, generated by 10 % labeled mOct4⁻ BM-MAPCs was more pronounced compared to 1 % labeled cells. SC stem cell