Evaluation of the theranostic potential of [64Cu]CuCl2 in glioblastoma spheroids.

Background: Glioblastoma is an extremely aggressive malignant tumor with a very poor prognosis. Due to the increased proliferation rate of glioblastoma, there is the development of hypoxic regions, characterized by an increased concentration of copper (Cu). Considering this, ⁶⁴Cu has attracted attention as a possible theranostic radionuclide for glioblastoma. In particular, [⁶⁴Cu]CuCl₂ accumulates in glioblastoma, being considered a suitable agent for positron emission tomography. Here, we explore further the theranostic potential of [⁶⁴Cu]CuCl₂, by studying its therapeutic effects in advanced three-dimensional glioblastoma cellular models. First, we established spheroids from three glioblastoma (T98G, U373, and U87) and a non-tumoral astrocytic cell line. Then, we evaluated the therapeutic responses of spheroids to [⁶⁴Cu]CuCl₂ exposure by analyzing spheroids' growth, viability, and cells' proliferative capacity. Afterward, we studied possible mechanisms responsible for the therapeutic outcomes, including the uptake of ⁶⁴Cu, the expression levels of a copper transporter (CTR1), the presence of a cancer stem cell population, and the production of reactive oxygen species (ROS).

Results: Results revealed that [⁶⁴Cu]CuCl₂ is able to significantly reduce spheroids' growth and viability, while also affecting cells' proliferation capacity. The uptake of ⁶⁴Cu, the presence of cancer stem-like cells and the production of ROS were in accordance with the therapeutic response. However, expression levels of CTR1 were not in agreement with uptake levels, revealing that other mechanisms could be involved in the uptake of ⁶⁴Cu.

Conclusions: Overall, our results further support [⁶⁴Cu]CuCl₂ potential as a theranostic agent for glioblastoma, unveiling potential mechanisms that could be involved in the therapeutic response.