Multicellular
tumor spheroids have emerged as well-structured,
three-dimensional culture models that resemble and mimic the complexity
of the dense and hypoxic cancer microenvironment. However, in brain
tumor studies, a variety of glioblastoma multiforme (GBM) cell lines
only self-assemble into loose cellular aggregates, lacking the properties
of actual glioma tumors in humans. In this study, we used type-I collagen
as an extracellular matrix component to promote the compaction of
GBM aggregates forming tight spheroids to understand how collagen
influences the properties of tumors, such as their growth, proliferation,
and invasion, and collagenase to promote collagen degradation. The
GBM cell lines U87MG, T98G, and A172, as well as the medulloblastoma
cell line UW473, were used as standard cell lines that do not spontaneously
self-assemble into spheroids, and GBM U251 was used as a self-assembling
cell line. According to the findings, all cell lines formed tight
spheroids at collagen concentrations higher than 15.0 μg mL–1. Collagen was distributed along the spheroid, similarly
to that observed in invasive GBM tumors, and decreased cell migration
with no effect on the cellular uptake of small active molecules, as
demonstrated by uptake studies using the photosensitizer verteporfin.
The enzymatic cleavage of collagen affected spheroid morphology and
increased cell migration while maintaining cell viability. Such behaviors
are relevant to the physiological models of GBM tumors and are useful
for better understanding cell migration and the in vivo infiltration
path, drug screening, and kinetics of progression of GBM tumors.