Widespread tumor cell invasion is a fundamental property of diffuse gliomas and is ultimately responsible for their poor prognosis. A greater understanding of basic mechanisms underlying glioma invasion is needed to provide insights into therapies that could potentially counteract them. While none of the currently available in vitro models can fully recapitulate the complex interactions of glioma cells within the brain tumor microenvironment, if chosen and developed appropriately, these models can provide controlled experimental settings to study molecular and cellular phenomena that are challenging or impossible to model in vivo. Therefore, selecting the most appropriate in vitro model, together with its inherent advantages and limitations, for specific hypotheses and experimental questions achieves primary significance. In this review, we describe and discuss commonly used methods for modeling and studying glioma invasion in vitro, including platforms, matrices, cell culture, and visualization techniques, so that choices for experimental approach are informed and optimal.

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Glioblastoma (GBM) is a highly malignant primary brain tumor and has a poor prognosis and is resistant to the most advanced therapies. The development of highly hypoxic centrally located necrotic regions is strongly associated with accelerated GBM progression, yet mechanistic explanations are not complete. Hypoxic regions within GBM are highly enriched for glioma stem cells (GSC), which are critical for tumor initiation, recurrence and therapeutic resistance due to their self-renewing capabilites. While most GBM cells migrate outward, away from hypoxia, GSCs accumulate there, forming a hypercellular border called pseudopalisades that promote their survival. Mechanisms that mediate GSC accumulation within pseudopalisades are unknown. We hypothesize that GSCs are enriched in the pseudopalisades due to the homing of a subpopulation towards the supportive hypoxic microenvironment. This in turn activates critical hypoxia-induced drivers to promote stemness, survival and migratory behavior encouraging the recruitment of more GSCs. Using two genetically distinct patient-derived GBM cell lines, we found that exposure to hypoxia in vitro led to enrichment of GSCs among a heterogeneous population of GSCs and non-GSCs. We found that hypoxia enhanced the expression of stem cell, pro-survival and pro-migratory factors in GSCs, such as the pro-migratory chemokine SDF-1α, and its cognate receptor CXCR4. Importantly, we found hypoxia also induced upregulation of OLIG2, one of four core transcription factors necessary and sufficient to induce stemness, in GSCs and non-GSCs exposed to hypoxia. We determined that OLIG2 was necessary for the expression of stem cell markers, and that its knockdown reduced cellular migration in hypoxia vs normoxia in GSCs. This suggests a critical role for OLIG2 in both hypoxia-induced stemness and homing behavior. We also generated a unique model of localized hypoxia in one brain hemisphere through vaso-cclusion and observed the homing of xenografted GBM cells towards hypoxia, regulated by OLIG2 in vivo. These data shed light on how hypoxic tumor microenvironments facilitate mechanisms vital to GBM progression and therapeutic resistance. Citation Format: Nitya V. Sharma, Monica Chau, Subhas Mukherjee, James Ross, Brandon Miller, Changming Zhang, Jun Kong, Carol Tucker-Burden, Emily Kaissi, John W. Reitnauer, Bilge Dundar, Cheryl L. Olson, Gregory Bix, Daniel J. Brat. Hypoxic microenvironments promote stemness and enhance the directed migration of glioma stem cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1153.

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BACKGROUND Breast Cancer is the most common cancer type in women, second among the all cancers, and inherited with autosomal dominant pattern. The clinical diagnosis of BC relies on the published diagnostic criteria, and two genes have been identified as the main causative for breast cancer which are BRCA1 and BRCA2. OBJECTIVE We aimed to compare the index cases with the diagnostic features to describe the genotype/demographic information association in breast cancer. METHODS We performed mutational analyses for the BRCA1 and BRCA2 genes on 2475 individuals from collobrative centers across Turkey, whom 1444 of them were ascertained index cases. RESULTS We identified mutations in 17% (421/2475) of all individuals while its almost the same 16.6% (239/1444) in 1444 index cases. Mutations in BRCA1/BRCA2 genes were detected in 17.8% (131/737) of familial cases and 12% (78/549) of sporadic breast cancer, with 4.9% of mutations in the BRCA1 and 12% in the BRCA2. CONCLUSIONS Genotype variation and demographic information patterns were analyzed of all observed breast cancer findings in probands. We showed that patients with BRCA2 mutations have significantly been identified more than BRCA1 mutations. We also observed that sporadic breast cancer cases without familial history have less mutation positivity in BRCA1/BRCA2 genes, and the results were consistent with other studies in the Mediterranean region. On performing meta-analyses of our data and the other limited studies of the Mediterranean region in the literature, we found significant correlations that individual studies did not have sufficient power to conclude. Correlating genotypes with demographic information should facilitate the disease management of BC both the familial and non-familial cases.

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