Citations

Abstract Glioblastoma (GBM) is the most common and aggressive primary brain tumor in adults with a median survival of 14 months despite multimodal treatment. Patients with GBM tumors exhibit a post-resection recurrence rate of almost 100%. The tumor recurrence and treatment resistance properties of GBM reside in a stem-like cell population called Brain Tumor Initiating Cells (BTIC). Among primary GBMs, periventricular tumors exhibit worse survival than tumors distal to the lateral ventricles (LV), the cause for this worse outcome is not known. A potential explanation is the proximity of these tumors to the cerebrospinal fluid (CSF) and the neurogenic niche in the sub-ventricular zone (SVZ). Chemotactic signals present in the cerebrospinal fluid (CSF) regulate neural progenitor cells migratory response and differentiation profile. Our preliminary data show that cancer-derived CSF induces an increase in the migration and proliferation of GBM cells when compared to non-cancer CSF. We evaluated the transcriptome of human GBM cells in response to cancer and non-cancer CSF and identified alpha-1-antichymotrypsin (SERPINA3) as one of the genes that show higher over expression upon cancer CSF-stimulation. SERPINA3 is a circulating anti-protease that is produced and released in different tissues such as liver, prostate, lungs, endometrium and brain that is over-expressed in multiple cancers. We hypothesize that the overexpression of SERPINA3 in response to CSF is a contributing factor to the increase malignancy of periventricular GBM tumors. We tested this hypothesis in silico, in vitro and in vivo. Using TCGA and Rembrandt databases we observed a higher expression of SERPINA3 in brain tumor tissue compared to controls with no differences among GBM subtypes. In GBM patients, expression of SERPINA3 negatively affects survival expectancy. In vitro, Using intraoperative samples, we confirmed that SERPINA3 is overexpressed in brain cancer tissue by western-blot and qRT-PCR. Interestingly, we observed a higher nuclear localization of SERPINA3 in cancer tissue and cells. To determine if SERPINA3 has an effect on the malignancy of GBM cells, we silenced its expression using shRNA. SERPINA3 silencing induced a decrease in cell proliferation (p<0.05), as well as migration (p<0.05), and invasion (p<0.05). Remarkably CD133 expression and stem cell markers were decreased when SERPINA3 is silenced. In contrast, the addition of recombinant SERPINA3 induced an increase in cell migration (p<0.05) of GBM cells. Moreover, cancer CSF is no longer able to induce an increase in GBM cell migration in SERPINA3-KD cells (p<0.05). In vivo, mice orthotopically-injected with SERPINA3-KD cells showed a prolonged overall survival (p<0.05). In summary, our results support the hypothesis that SERPINA3 plays a key role in GBM malignancy in response to CSF and its inhibition results in a better outcome using GBM preclinical models. Targeting the CSF-GBM interaction is a potential therapeutic approach that remains to be explored. Citation Format: Montserrat A. Lara Velazquez, Natanael Zarco, Anna Carrano, Jordan Phillips, Paula Schiapparelli, Emily S. Norton, Stephanie Jeanneret, Teresita Corona, Jose Segovia, Kaisorn Chaichana, Yan Asmann, Alfredo Quinones Hinojosa, Hugo Guerrero-Cazares. Cerebrospinal fluid-responsive factor SERPINA3 induces an increase in the malignancy of glioblastoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3780.

Abstract Glioblastoma (GBM) is the most aggressive of all the brain tumors with a median patient survival less than 15 months. Despite of surgical resection, radiotherapy, and chemotherapy, recurrence rate is almost 100%. A great percentage of GBM tumors (~60%) infiltrate and contact the ventricular-subventricular zone (V-SVZ). Interestingly, these tumors are the most aggressive, and invariably lead to higher distal recurrence rates, shorter time to tumor progression, and lower overall survival of the patient. The reason for this role of V-SVZ-proximity on the outcome of GBM patients is unknown. We suggest that a potential explanation is the interaction of GBM with the V-SVZ. This region is the largest neurogenic niche in the adult brain where neural stem cells (NSCs) give rise to newborn neuroblasts that migrate toward the olfactory bulb. In GBM there is a cell subpopulation called brain tumor stem cells (BTSCs) with NSCs-like characteristics, but with added potential for tumor initiation, recurrence and invasiveness. Tumor microenvironment plays an important role in migration and invasion process. In the present work, we used the total exosome isolation kit to purify Extracellular Vesicles (EVs) from human primary cultures of BTSCs. We determined that BTSCs-derived EVs contain specific information that is transfer to primary cultures of human Neural Progenitors Cells (NPCs) modulating their proliferation rate, cell viability, and migration. In addition, we identify that NPCs taken up BTSCs-derived EVs and significantly increase the expression levels of stemness-related genes such as Nestin, Nanog, and Sox2, suggesting that a phenotypic transdifferentiation is being carry out. These results support our hypothesis that GBM modulate the tumor microenvironment close to the V-SVZ by releasing EVs that target cellular components in this region and promote their phenotypic transformation, highlighting that NPCs biology changes in the context of tumor environment.