Fig. 3

Intracranial injection of oHSV-1 in established GL261 tumor dramatically blocks tumor growth in vivo and rejects GL261 tumor challenge in the opposite brain hemisphere. C57BL/6 mice (n = 45) were initially injected with 3 × 10⁴ GL261 cells into the right striatum. After seven days of tumor implantation, one group of mice injected with GL261 cells was further treated with 10⁶ plaque-forming units (PFU) of oHSV-1 in the same brain hemisphere (n = 15). As a control, another group of mice received intracranial injections of PBS (vehicle) (n = 15) and the other animals were left untreated (n = 15). At 43 post-tumor implantation all surviving mice (n = 7) were challenged with parental 3 × 10⁴ GL261 tumor cells in the opposite brain hemisphere, and after additional 21 days mice were sacrificed, brains were removed, and serial sections of the brain were carried out to measure tumor size and for staining. (A) Average tumor size of GL261 tumor in oHSV-1 treated mice (oHSV-1) and in control group (vehicle). Data are represented as mean values, and error bars indicate the standard deviation (SD) within each group. p-Values were determined via unpaired t-test; ****P < 0.0001. (B) HE and IHC staining of serial brain sections. The panels were taken at 20x magnification. Arrowheads in HE, Nestin and MHC-II upper panels (oHSV-1) point to the sites of tumor cell injection shwing the absence of growing tumors. HE, hematoxylin and eosin; IHC, immunohistochemistry. Scale bar corresponds to 500 μM