Identification of functionally distinct and interacting cancer cell subpopulations from glioblastoma with intratumoral genetic heterogeneity

Abstract

Background Glioblastomas display a high level of intratumoral heterogeneity with regard to both genetic and histological features. Within single tumors, subclones have been shown to communicate with each other to affect overall tumor growth. The aim of this study was to broaden the understanding of interclonal communication in glioblastoma. Methods We have used the U-343 model, consisting of U-343 MG, U-343 MGa, U-343 MGa 31L, and U-343 MGa Cl2:6, a set of distinct glioblastoma cell lines that have been derived from the same tumor. We characterized these with regard to temozolomide sensitivity, protein secretome, gene expression, DNA copy number, and cancer cell phenotypic traits. Furthermore, we performed coculture and conditioned media-based experiments to model cell-to-cell signaling in a setting of intratumoral heterogeneity. Results Temozolomide treatment of a coculture composed of all 4 U-343 cell lines presents a tumor relapse model where the least sensitive population, U-343 MGa 31L, outlives the others. Interestingly, the U-343 cell lines were shown to have distinct gene expression signatures and phenotypes although they were derived from a single tumor. The DNA copy number analysis revealed both common and unique alterations, indicating the evolutionary relationship between the cells. Moreover, these cells were found to communicate and affect each other’s proliferation, both via contact-dependent and -independent interactions, where NOTCH1, TGFBI, and ADAMTS1 signaling effects were involved, respectively. Conclusions These results provide insight into how complex the signaling events may prove to be in a setting of intratumoral heterogeneity in glioblastoma and provide a map for future studies.

A phase Ib/IIa trial of 9 repurposed drugs combined with temozolomide for the treatment of recurrent glioblastoma: CUSP9v3

“…In the common aggressive cancers, and especially in GBM, phenotypic spatial and temporal heterogeneity, in both stem and non-stem cell subsets, is a dynamic process responding to treatment interventions and driven further by hypoxia. 43–45 In addition, GBM may be considered a collection of mutually interacting, mutually supporting cellular subpopulations 46 demanding the use of a multi-drug combination to achieve prolonged treatment response.…”

SFRP2 induces a mesenchymal subtype transition by suppression of SOX2 in glioblastoma

“…This is considered to be a major hurdle for successful treatment of glioblastoma, where cells may display differential drug sensitivities, thereby posing an increased risk for developing treatment resistance and the pre-existence of resistant subpopulations, as exemplified in attempts of anti-EGFR treatment and in temozolomide resistance [ 9 – 11 ]. Intratumoral heterogeneity among the malignant cells may arise due to variation of lines and levels of differentiation, co-evolution of populations with different genetic or epigenetic characteristics, local microenvironmental cues or a combination of these that may evoke different phenotypes [ 12 – 14 ]. Frequently occurring genetic alterations in glioblastoma have been connected with different phenotypic states, and cells may also appear in intermediate hybrid states due to plasticity within single tumors [ 15 ].…”

Electrotherapies for Glioblastoma

“…Since the different subtypes respond differently to therapies and have differential survival times, the discovery of multiple subtypes existing within the same tumour complicates patient diagnosis and treatment (Figure 6). [175,176] Spatially distinct Figure 5. How can electrotherapy be improved in order to better treat GBM?…”

“…Since the different subtypes respond differently to therapies and have differential survival times, the discovery of multiple subtypes existing within the same tumour complicates patient diagnosis and treatment ( Figure 6 ). [ 175 , 176 ] Spatially distinct tumour fragments showed that heterogeneity increases with time resulting in different areas of the tumour being classified into different transcriptional subtypes. Further to this, multiple biopsies taken from the same tumour were analyzed for their transcription subtype.…”