P14.78 Comparison of progression-free survival after reirradiation of local and distant glioblastoma’s relapses

BACKGROUND

Despite using of modern comprehensive approaches to the treatment of patients with glioblastomas (GB) it invariably recur after a median interval of less than 7 months. Relapses are inevitable and is often the leading cause of death in patients. About 80–90% of recurrences are local, distant relapses are 5–20%. The optimal treatment strategy of recurrent GB have not yet been determined.

MATERIAL AND METHODS

The analysis included 130 patients with 160 lesions after primary combined treatment. Progression was assessed based on the RANO criteria. All patients have been re-irradiated in various regimens: 26 pts with median dose 60 Gy/30 fr, 20 pts with median dose 45 Gy/15 fr, 74 pts with dose 24-35Gy for 3–7 fr., 10 pts with median dose 22Gy/1fr. The scheme and regimen of fractionation were determined by tumor volume, localization and functional status of patient. Chemotherapy was changed to a regimen with Bevacizumab (BVZ) before the re-irradiation. According to the EORTC criteria lesions were divided as local (n=112) and distant (n=48) progression with median volume 23.6 cc and 14.7 cc respectively.

RESULTS

The median progression-free survival in the whole group was 8.2 months(95% CI 7–8.7). Progression-free survival at 6; 12 and 24 months was 65.8%; 21.9% and 4% respectively. Progression-free median survival after treatment of local and distant glioblastoma recurrences was different: 7.6 and 9.2 months, respectively (p = 0.048). In 17.4% radiation necrosis was detected according to MRI and 11C-methionine PET-CT data. Steroid and BVZ therapy were effective in these cases, no one of them was reoperated.

CONCLUSION

Re-irradiation for GB recurrences is effective and safe way for improvement of outcomes in patients with progression. In the group of patients with local relapses, local control is lower than in the group of distant ones. It may associated with the increasing of the radioresistance of tumor cells after the initial combined treatment. Further studies are needed to compare and assess the role of radiobiological and others factors in the development of local and distant recurrence.The research was supported financially by RFBR (Project No. 18-29-01061).

P11.48 Dose-dependent effects of radiation exposure on the cell culture of glioblastoma G01, obtained from the patient with a long-term survival

Background: The predictors of a favorable prognosis regarding radiation exposure in patients with glioblastoma have not been studied enough, therefore, the search for factors determining a tumor response to the combined chemoradiation treatment is an actual task at present. DNA repair protein RAD51 homolog 1 (RAD51) is a crucial protein for homologous recombination and its inhibition has been shown to sensitize glioma stem cells to irradiation. Materials and Methods: G01 primary glioblastoma cell culture was obtained from tumor tissues from patient with long term survival (42 month).An irradiation with the energy of 6 MeV was carried out in 1 fraction 20,40,60,80,100,125,150,200,250 Gy with Linac. mRNA expression of the RAD51 gene, XRCC6, XRCC5 genes, relative amount of RAD51 protein and Ku70, Ku80 proteins, proliferative activity of cell culture was evaluated by RT-PCR, Western blotting, MTT-test, respectively.Results: When G01 cells were irradiated with doses from 5 to 180 Gy there was a uniform linear decrease in the population of proliferating cells compared to the control, but at a dose of 200 Gy a rise to 24% was observed. The mRNA expression of the RAD51 gene increased 2 times after irradiation at a dose of 20 Gy compared with control and then increased, reaching a peak at the level of 100,250 Gy. Minimal expression was observed after irradiation at a dose of 20 and also decreased at 200 Gy. The mRNA expression of the XRCC5 gene increased 2-fold after irradiation at a dose of 20 Gy compared with control and then decreased, remaining at the same level. Minimal expression was observed after irradiation at a dose of 200Gy. The relative amount of Ku80 protein reached a peak at a dose of 100 Gy, followed by a decrease. Maximum expression level of mRNA of the XRCC6 gene was observed after irradiation at a dose of 250Gy. The relative amount of Ku70 protein also decreased at 200 Gy and reached a peak at a dose of 250 Gy. Conclusions: After irradiation transplantable G01 cell culture from patient with long term survival a linear decrease in proliferative activity depending on the dose was observed with an decrease in mRNA expression of Rad51 gene and the relative amount of RAD51,Ku70 in dose level of 200Gy that could potentially indicate sensitivity point to radiation exposure in these cell culture. Further studies using cell cultures from patients may help in understanding the mechanisms of radioresistance and radiosensitivity in glioblastoma.The research was supported financially by RFBR (Project No. 18-29-01061).

Effects of striatal transplantation of cells transfected with GDNF gene without pre- and pro-regions in mouse model of Parkinson's disease

Background

Previously, we have shown that transgenic cells bearing the GDNF gene with deleted pre- and pro-regions (mGDNF) can release transgenic GDNF. The medium conditioned by transgenic cells with mGDNF induced axonal growth in rat embryonic spinal ganglion in vitro. Here we demonstrate a neurotrophic effect of mGDNF on PC12 cells in vitro as well as its neuroprotective effect on dopaminergic neurons in the substantia nigra pars compacta in vivo as indicated by improved motor coordination and sleep-wakefulness cycle in the MPTP mouse model of Parkinson’s disease.

Results

HEK293 cells were transfected with a vector encoding an isoform of the human GDNF gene with deleted pre- and pro-regions (mGDNF). This factor in the medium conditioned by the transfected cells was shown to induce axonal growth in PC12 cells. The early Parkinson’s disease model was established by injection of the dopaminergic pro-neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) into C57Bl/6 mice. Transgenic HEK293/mGDNF/GFP cells were transplanted into the striatum (caudate-putamen) of experimental mice. The sleep-wakefulness cycle was studied by continuous EEG and motor activity monitoring 1 and 2 weeks after MPTP injection. After the experiment, the motor coordination of experimental animals was evaluated in the rotarod test, and dopaminergic neurons in the substantia nigra pars compacta were counted in cross-sections of the midbrain. MPTP administration lowered the number of tyrosine hydroxylase immunopositive cells in the substantia nigra pars compacta, decreased motor coordination, and increased the total wake time during the dark period. The transplantation of HEK293/mGDNF cells into the caudate-putamen 3 days prior to MPTP injection smoothed these effects, while the control transplantation of HEK293 cells showed no notable impact.

Conclusions

Transplantation of transgenic cells with the GDNF gene lacking the pre- and pro-sequences can protect dopaminergic neurons in the mouse midbrain from the subsequent administration of the pro-neurotoxin MPTP, which is confirmed by polysomnographic, behavioral and histochemical data. Hence it is released from transfected cells and preserves the differentiation activity and neuroprotective properties.