Study Of The Effect Of Radiosensitivity And Cell Cycle Distribution Of Bortezomib On Malignant Glioma

Bankground and ObjectiveGliomas are the most common malignant brain tumors. They account for more than35%-60%of all neoplasms of the central nervous system. Although in the past two decades, the understanding of glioma biology and genetics has been greatly improved, but still no effective way to cure gliomas; The current standard of care to treat patients with malignant glioma (World Health Organization Grade3and4) includes postoperative radiotherapy (RT) with concomitant and adjuvant temozolomide-based chemotherapy. However, the prognosis of patients with malignant glioma remains dismal, and median survival does not exceed52weeks. The latest research says that new combinations of RT with conventional chemotherapeutic agents and/or target-specific inhibitors needed to improve patient prognosis. This target requires a mechanism of radiosensitivity research and a rational choice of drugs.Ubiquitin-proteasome pathway (UPP) was found by the proteasome and ubiquitin composition In the1980s. UPP exist in eukaryotic cells within cytoplasm, nuclear, biological protein inside the body and it is an important way of selective degradation, can affect the gene expression regulation, the cell cycle, oxidative stress reaction and many kinds of cellular activities. Proteasome inhibitors specifically inhibit the activity of protease, prevent the growth of tumors, adhesion and angiogenesis. Proteasome inhibitors were also shown to sensitize tumor cells to DNA-damaging drugs, including effect of radiosensitivity in different tumor models, therefore becoming attractive for the treatment of human cancer.Bortezomib (BTZ, Brand name Velcade) is high selectivity and reversible proteasome inhibitor. At present BTZ indicated to treat patients with hematologic tumors, such as multiple myeloma, and recently for relapsed mantle-cell lymphoma. Several preclinical trials are ongoing for multiple solid tumors, including high-grade gliomas.Combining theory with clinical treatment of the status, we proceed to the experimental design. This study is divided into three parts, Part Ⅰ:the U87xenograft model was established. U87cells were breeded by using high sugar DMEN medium, trypsin digestion, after take off the wall percussion, extraction tumor cell suspension liquid vaccination in nude mice right fore axillary department skin,0.2ml/only; part Ⅱ:Nude mices were treated by Intraperitoneal injection of BTZ and8MeV-β electron beam radiation; Part Ⅲ:Observe the effect of BTZ intraperitoneal injection on the inhibition rate and cell cycle distribution of tumor in group A; Determination of tumor growth delay time (TGD), sensitizing enhancement ratio (SER), and draw Kaplan-Meier survival curves in group B.MethodsThe U87xenograft model was established. All64mices bearing6mm xenograft tumor were assigned randomly divided into experimental A and experimental B, each group only32, then randomly divided into4groups:control group (CTRL), Radiation group (RT), bortezomib group(BTZ) and joint group(RT+BTZ). Nude mices were treated by8MeV-(3electron beam radiation. The joint group were given BTZ0.9mg/kg at a weekly, treatments were delivered for2weeks.Observe the effect of BTZ intraperitoneal injection on the inhibition rate and cell cycle distribution of tumor, tumors were excised24h after the last radiotherapy administration. The experiment B for2weeks after treatment, mices receivede normal breeding until death, determination of tumor growth delay time (TGD), sensitizing enhancement ratio (SER), and draw Kaplan-Meier survival curves.Statistical methods:SPSS17.0statistical software is used to process data, using analysis of variance (One May ANOVA) statistical significance to test group; using analysis Kaplan-Meier draw survival curves.Results1.The xenograft models of68mices were established,only one mice died in accident.BTZ main adverse reactions were periphery mental illness, low blood pressure, low platelet (rates were37%,43%and12%). Nude mices in experimental group received the treatment (clinical recommended dosage), the mental state were well, normal activities, eating, quick reaction, skin colorl and stool had not seen the exception.2.The inhibition rate of RT+BTZ group was46.5%,and superior to RT group (31.5%, F=25.6, P=0.00<0.0). The TGD of joint group was59d vs38d (RT group), and the sensitizing enhancement ratio of BTZ was1.44. Showed that BTZ+RT make the sensitivity of radiotherapy alone1.44times improve. Combining BTZ with RT seemed to given that cells in G0/G1decreased (79.9%vs66.0%), P=0.005<0.01and cells in G2/M increased (3.2%vs16.4%), P=0.00<0.05, significant difference was found between groups. Survival time of nude mice was extended in BTZ+RT group.Conclusion1. BTZ has obvious radiosensitizing properties for U87xenograft model, the BTZ radiosensitizing effect seemed to be linked to its ability to interfere with cell cycle control after irradiation.2. Local radiotherapy combined with BTZ extend survival time of nude mice.3. BTZ of clinical recommended dose did not produce toxic reaction to death. Mices in injection groups showed good condition, and compared the blank group did not see obvious adverse reaction.