Glioblastoma is the most frequent and aggressive brain tumor in adults. Based on genomic data glioblastomas can be classified into at least four subclasses: proneural, neural, classical and mesenchymal. However, recent publications have shown that individual glioblastoma can be heterogeneous and contain a mixture of these four subclasses. Moreover, it has been shown in other studies that intratumoral communication between genetically distinct cancer cell subclones in glioblastomas can affect the overall tumor growth via secreted proteins. In this project we aim to investigate the difference between protein secretomes from different tumor cell clones from within genetically heterogeneous glioblastomas.

For this we have used the U343 cell culture system, consisting of U343MG, U343MGa, U343MGa-31L and U343MGa-Cl2:6. These cultures were derived from a single glioblastoma, and can be divided into at least two categories based on their mutually exclusive expression patterns of FN1 and GFAP. Here we show that these different cultures display different characteristics with regard to matrigel invasion capacity, neurosphere formation capacity, and gene and protein expression. Combinatorial co-culture and conditioned media based experiments showed that the U343MG culture elicit anti-proliferative effects on U343MGa-31L via secreted factors. To identify proteins that are secreted by U343MG we have used Secretome Protein Enrichment with Click Sugars (SPECS) followed by mass spectrometry analysis. We detected 150 proteins by more than 2 peptides in U343MG conditioned media. Several of these proteins were growth factors and matrix proteins, including FN1. We are now performing a combined secretome and gene expression analysis of all U343 cultures to identify candidate secreted proteins that most likely are involved in the observed signaling effects between U343MG and U343MGa-31L. Finally, a functional genomic approach will be taken to experimentally pinpoint mediators of these inter-clonal effects.

This study shows that subclones from a heterogeneous glioblastoma can display different phenotypic characters and affect each other via secreted factors. Further knowledge about cell-to-cell communication through secreted proteins in glioblastoma may provide novel therapeutic targets.

Citation Format: Min Guo, Susanne Heller, Jessie Thorslund, Lukas Orre, Janne Lehtiö, Monica Nistér, Daniel Hägerstrand. Understanding the dynamic interplay between genetically different cancer cell clones in glioblastoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2385.