gms | German Medical Science

Objective: Glioblastoma (GBM), the most frequent primary brain tumor, has an exceptionally poor prognosis. Recent reports have indicated that D,L-methadone alone or in combination with doxorubicin may be a promising approach for the adjuvant treatment of GBM. However, doxorubicin is not routinely used in the clinical management of GBM due to its poor penetration of the blood-brain barrier and high neurotoxic potential. The goal of our study was to validate the efficacy of D,L-methadone in a molecularly well characterized set of primary GBM cells cultured under stem cell promoting conditions in addition to established cell lines and investigate the potential synergism with temozolomide (TMZ) as a clinically relevant chemotherapy backbone.

Methods: We used two established GBM cell lines (U87, U251) and four brain tumor initiating cell lines (BTICs) derived from patient specimen. The BTICs were transcriptionally characterized: two cell lines were classified as mesenchymal and 2 as proneural subtype. Cells were treated for 6 days with D,L-methadone alone at concentrations from 0.3 – 45 µg/ml; to investigate a potential synergism with chemotherapy, cells were exposed to TMZ (100 µM) in combination with increasing concentrations of D,L-methadone. Effects on cell viability were measured by crystal violet assay, induction of apoptosis was assessed by annexin – V FACS analysis.

Results: High concentrations of D,L-methadone (15-45 µg/ml) significantly induced apoptosis combined with reduced cell viability in all cell lines and showed a significant synergism with TMZ. However, in realistic dosages reflecting the clinically reachable concentrations (0.3 – 1 µg/ml), D,L-methadone alone showed either no significant cell killing or induced even pro – proliferation in specific cell lines. In addition, at clinically realistic concentrations, we observed antagonistic effects to TMZ in several cell lines.

Conclusion: These results indicate that D,L-methadone at realistic concentrations may not provide significant efficacy in the treatment of GBM. In addition, depending on the biological context of the specific tumor cell, D,L-methadone may even induce higher proliferation rates and antagonistic effects to TMZ.