Patient-derived Glioblastoma Multiforme Cells Research Articles

Cilengitide response in ultra-low passage glioblastoma cell lines: relation to molecular markers

In glioblastoma multiforme (GBM), a tumor still characterized by dismal prognosis, recent research focuses on novel-targeted compounds, in addition to standard temozolomide (TMZ) chemotherapy. One of these emerging compounds is cilengitide (CGT), which by binding to integrins (i.e., αvβ3 and αvβ5) may inhibit angiogenesis and also is directly cytotoxic to tumor cells by interfering with intracellular signaling pathways. A total of ten patient-derived ultra-low passage GBM cell lines were treated with increasing doses of CGT, TMZ, and a combination of both substances. Inhibitory concentrations of 50% (IC₅₀) were determined for the single agents and as a combination. Cell lines were stratified according to MGMT promoter methylation. The expression of relevant integrins was assessed by flow cytometry. In monotherapy, all GBM cell lines showed higher sensitivity to CGT than to TMZ, as determined by IC₅₀ values in relation to clinically relevant patient plasma levels. MGMT promoter methylation correlated with a significantly higher TMZ response, but tended to be associated with a lower CGT response. Response to CGT was not correlated with cell surface integrin expression as measured by flow cytometry. Finally, addition of CGT to TMZ enhanced growth inhibition, but only in those cell lines with a methylated MGMT promoter. As suggested by this analysis, patients with MGMT promoter-methylated GBM may benefit from addition of CGT to the standard TMZ treatment, while patients with MGMT promoter-unmethylated GBM may better respond to CGT monotherapy.

Abstract 5194: Heterogenous expression of chemokine receptors in primary patient-derived GBM lines; association of CXCR3, CXCR4, and CXCR7 with a slow cycling sub-population

Abstract WHO class IV glioblastoma multiforme (GBM) is one of the most malignant and aggressive forms of primary brain tumors and despite multimodal treatments patients have modest survival rates. The poor prognosis and therapy resistance of glioblastoma are believed to be a consequence of a subpopulation of glioma stem-like cells. As such, targeting functions associated with this cell population is likely to yield new therapeutic strategies. Roles for CXCR3, CXCR4, and CXCR7 in glioblastoma are well documented although previously published studies involved primarily the characterization of glioma cell lines grown in the presence of serum. Our studies were undertaken to understand the roles of chemokine receptors CXCR4 and CXCR7, and their ligands CXCL11 and CXCL12, in modulating glioblastoma stem-like cell functions. Tumors xenografts developed from patient-derived primary GBM cells cultured as gliomaspheres in serum-free conditions expressed CXCR4, CXCR7, CXCL11, and CXCL12 in a manner similar to expression patterns of these genes in human GBM tissues. Flow cytometry analysis of CXCR4 and CXCR7 on various patient-derived primary GBM lines indicated marked heterogenous expression of these receptors. Variable percentages of CXCR4+, CXCR7+, and CXCR4+/CXCR7+ (double positive) populations were evident. In contrast, chemokine receptors CCR3 and CXCR3 were co-expressed on a small but similar percentage of cells in all cell lines. RT-PCR indicated that all lines expressed CXCL11 while none expressed CXCL12. A slow cycling sub-population of cells, which express stem-like cell markers and exhibit high tumorigenic frequencies, were enriched for CXCR3, CXCR4, and CXCR7. CXCR4+ and CXCR7+ subpopulations were capable of forming spheres in serum-free culture conditions and exhibited plasticity in regenerating the cellular heterogeneity of their parental phenotype. In addition, both CXCR4+ and CXCR7+ cells were able to initiate the formation of intracranial tumors. In vitro functional studies showed that while CXCL12, but not CXCL11, stimulated the migration of GBM cell lines, both of these ligands were able to promote short-term proliferation. Collectively, the results suggest that CXCR4 and CXCR7 may regulate the stem-like properties of GBM cells. The high degree of heterogeneity in CXCR4 and CXCR7 expression both within and between glioblastomas suggests that personalized treatment of glioblastoma patients using selective antagonists that target CXCR4 and CXCR7 may need to consider the complex expression patterns and specific functions of these receptors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5194. doi:1538-7445.AM2012-5194