Summary: Researchers report that kalata B1, a cyclic peptide originally found in violets, can dramatically increase the effectiveness of the chemotherapy drug temozolomide (TMZ) against glioblastoma cells in laboratory experiments. In cell studies, a synthetic form of kalata B1 lowered the amount of TMZ needed to kill tumor cells by more than tenfold, suggesting a potential route to stronger combination therapies for this aggressive brain cancer.
The team found that a lab-made version of kalata B1 reproduces the natural molecule’s structure and biological activity. While these findings are promising, the investigators emphasize that substantial work — including safety and efficacy testing in animals and eventual clinical trials — remains before this approach could reach patients.
Key Facts:
- Kalata B1, a cyclotide derived from certain violet species, strongly enhances temozolomide’s activity in glioblastoma cells.
- A synthetic version of kalata B1 matches the natural peptide in structure and function.
- Researchers plan next to test the synthetic peptide in mouse models before any human trials.
Source: Brain Chemistry Labs
Background: Glioblastoma is among the most aggressive and lethal brain tumors. Gliomas constitute over 45% of brain cancers, and standard treatment — surgery followed by radiation and chemotherapy — often fails to control the disease long term. Temozolomide (TMZ) is the only broadly approved chemotherapy for glioblastoma, but many patients do not respond, and resistant tumor cells frequently emerge. Median survival remains around a year to a year and a half, and few patients survive beyond five years.
A research group based in Jackson Hole, Wyoming, affiliated with the non-profit Brain Chemistry Labs, has been investigating small cyclic peptides produced by violets called cyclotides. These peptides are highly stable, circular molecules that can form disulfide bonds and adopt compact, knotted shapes. In nature, cyclotides help plants defend against herbivores, fungi, and viruses; in the laboratory some cyclotides have shown activity against cancer cells.
The specific cyclotide at the center of this study, kalata B1, was first noted in an African herb used historically to facilitate childbirth. Natural sources yield only trace amounts of the peptide, making extraction impractical for larger-scale research. To overcome this limitation, the team worked with a commercial synthesis lab to produce sufficient quantities of a synthetic kalata B1 for experimental use.
Analytical methods confirmed that the synthetic peptide folds and functions the same as the natural product. Nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry were used to verify the synthetic molecule’s three-dimensional structure and sequence. In human glioblastoma cell lines, several cyclotides including synthetic kalata B1 showed dose-dependent cytotoxicity and, notably, chemosensitizing activity when combined with TMZ.
In the reported experiments, co-exposure of glioblastoma cells to synthetic kalata B1 dramatically lowered the TMZ concentration required for significant cell death. For example, in U-87 MG cells, combining TMZ with 0.5 µM synthetic kalata B1 produced substantial cytotoxicity with only 100 µM TMZ — roughly a 16-fold reduction in TMZ concentration compared with TMZ alone. In T98 cells, 0.25 µM synthetic kalata B1 enabled a significant effect at 75 µM TMZ, approximately a 15-fold reduction. The synthetic peptide also showed stability in human serum assays, an encouraging feature for further development.
With these in vitro results, the researchers say the next step is testing the synthetic kalata B1 in mouse models of glioblastoma. Those animal studies are planned to take place in Vienna, Austria. If animal testing confirms improved efficacy and acceptable safety, the pathway would then include additional preclinical work and carefully designed clinical trials.
Investigators caution that promising cell-culture results do not guarantee success in animals or humans. While Brain Chemistry Labs’ director and the senior authors consider the ability to synthesize kalata B1 in useful quantities an important advance, they stress that clinical application will require much more evidence about safety, dosing, delivery, and long-term effects.
About this glioblastoma brain cancer research news
Author: Marilyn Asay
Source: Brain Chemistry Labs
Contact: Marilyn Asay – Brain Chemistry Labs
Image credit: Neuroscience News
Original Research: Open access. “Kalata B1 Enhances Temozolomide Toxicity to Glioblastoma Cells” by Samantha L. Gerlach et al., published in Biomedicines.
Abstract (summary)
Kalata B1 Enhances Temozolomide Toxicity to Glioblastoma Cells
Glioblastoma (GBM) is the most aggressive primary brain cancer, and outcomes following surgery, radiation, and chemotherapy remain poor. New adjuvant approaches that sensitize tumor cells to chemotherapy are urgently needed. Cyclotides are plant-derived cyclic peptides that have shown the ability to chemosensitize certain drug-resistant cancers. This study compared natural and synthetic cyclotides — including Cycloviolacin O3, Cycloviolacin O19, natural kalata B1, synthetic kalata B1, and Vitri E — alone and combined with temozolomide in human glioblastoma cell lines.
The peptides were identified and characterized using chromatographic and spectrometric methods, and the synthetic kalata B1 sequence and three-dimensional fold were confirmed by orbitrap LC-MS and NMR spectroscopy. The cyclotides produced dose-dependent cytotoxic effects (IC50 values ranging from 2.4 to 21.1 µM) and acted as chemosensitizers for U-87 MG and T98 glioblastoma cells exposed to temozolomide. Co-treatment with synthetic kalata B1 allowed substantial reductions in TMZ concentration needed to induce cell death. These data support further investigation of cyclotides as chemosensitizers for glioblastoma therapy.