Kalata B1 Enhances Temozolomide Toxicity to Glioblastoma Cells

Area of Science:

• Oncology
• Pharmacology
• Biochemistry

Background:

• Glioblastoma (GBM) is an aggressive brain cancer with limited treatment options.
• Current combination therapies (surgery, radiation, chemotherapy) show suboptimal efficacy.
• Novel adjuvant therapies are crucial for improving GBM treatment outcomes.

Purpose of the Study:

• To investigate the potential of cyclotides as chemosensitizers for glioblastoma cells.
• To evaluate the efficacy of various natural and synthetic cyclotides in combination with temozolomide (TMZ).

Main Methods:

• Analysis of cyclotides (Cycloviolacin O3, O19, Kalata B1, Vitri E) using UPLC-PDA and HPLC-UV.
• Sequence verification of synthetic Kalata B1 via orbitrap LC-MS and structural confirmation by NMR.
• Assessment of cyclotide cytotoxicity and chemosensitization effects in human glioblastoma cell lines (U-87 MG, T 98) with TMZ.

Main Results:

• Cyclotides exhibited dose-dependent cytotoxicity (IC50 values 2.4–21.1 µM) as single agents.
• Co-exposure with cyclotides significantly reduced the required concentration of TMZ for glioblastoma cell death.
• Synthetic Kalata B1 demonstrated potent chemosensitization, enabling 16-fold and 15-fold reductions in TMZ dosage for U-87 MG and T 98 cells, respectively.
• Kalata B1 showed stability in human serum.

Conclusions:

• Cyclotides, particularly synthetic Kalata B1, can chemosensitize glioblastoma cells to temozolomide.
• These findings suggest cyclotides hold potential as an adjuvant therapy to enhance TMZ efficacy in GBM treatment.
• Further research into cyclotide-based therapies for glioblastoma is warranted.