Glioblastoma (GBM) is the most prevalent and malignant type of primary brain cancer with a median survival of only 15 months. Rapid tumour cell invasion within the brain is a significant challenge for physicians and their patients, reducing treatment efficacy and inevitably leading to tumour recurrence. Highly invasive tumour cells through the coordinated action of signalling proteins and proteases can lead to the degradation of the extracellular matrix (ECM). Although tissue remodelling and its interaction with invading and proliferating cells is well understood in other cancers including breast cancer, research is limited in GBM.
To develop an understanding of how invading and proliferating cells interact with the ECM we performed multiplex immunohistochemistry (mIHC) on primary and recurrent GBM tissue. This included pAKT (PI3K signalling), pERK1/2 (MAPK signalling), pCREB (transcriptional activation), MMP2 and MMP9 (ECM degradation) and PCNA (cell proliferation), which was integrated with Masson’s Trichrome staining to identify collagen-rich regions. To investigate this interaction in a 3D in vitro setting, brain tumour spheroids were embedded in a collagen Matrigel and visualised using live cell imaging, with mIHC performed on post-invading tumour spheroids.
Masson’s trichrome staining demonstrated extensive collagen deposition throughout primary and recurrent GBM tissue, with increased deposition of ECM in high-grade gliomas. Spatial analysis revealed heterogeneous PI3K and MAPK signaling, which correlated with distinct pathological hallmarks, including angiogenesis, tumour cell density, tumour cell invasion, and the ECM-stroma. In the 3D setting, we observed extensive tumour spheroid invasion and an upregulation of PI3K and MAPK signalling at the invasive front where cells interact with the collagen matrigel.
Future research aims to further investigate how specific components within the ECM influence tumour cell invasion and proliferation. Our results provide compelling evidence that the accumulation of ECM is an important element in GBM progression, and that targeting the ECM may be critical in reducing tumour cell proliferation and invasion, and thereby improving of small molecule signalling and invasion inhibitors.