| Background: Chordoma, slow growing bone tumours originating from remnants of the
notochord, leave affected patients with a median survival of six years. The high recurrence
rate of chordoma, together with limited treatment options and bad overall prognosis, make the
development of new treatment options urgently necessary.
Purpose: In this study, the potential of two natural products, silibinin and β-β-
dimethylacrylshikonin (DMAS), was tested on clival (MUG-CC1 and UM-Chor1) as well as
sacral (MUG-Chor1 and U-CH2) chordoma cell lines. The treatment was administered both as
single- and combined therapy.
Methods: For investigation of cell viability, the Cell Titer 96 Aqueous Non-Radioactive Cell
Proliferation Assay Kit was used. Apoptosis induction was studied by flow cytometry,
(Annexin V/SYTOX Green, caspase-3) and RT-qPCR. Pathway analyses were performed by
western blot.
Results: Both drugs were found to reduce cell viability alone as well as in combination in a
dose dependent manner, with DMAS being more efficient than silibinin. The mode of cell
death was mainly apoptosis in DMAS treated samples, while the combination therapy led to
apoptosis as well as late-apoptosis/necrosis. Silibinin therapy alone, although reducing cell
viability, did not lead to significant apoptotic effects in the performed assays. Focussing on
the molecular mechanism of DMAS induced apoptosis, it was found that major genes of the
mitochondrial apoptosis pathway, like NOXA and PUMA were overexpressed. Additionally,
western blot experiments showed a decrease of ERK/pERK, STAT3/pSTAT3 (Tyr705) and
AKT/pAKT expression/activation levels under DMAS treatment.
Conclusion: DMAS is a promising new candidate for chordoma therapy, while silibinin or a
combination of both is less favourable. |