Nikhil Prasad Fact checked by:Thailand Medical News Team Oct 07, 2026 57 minutes ago
A laboratory study has identified a synthetic peptide called RQ18 as a potentially promising anticancer candidate, after experiments showed that it selectively damaged several cancer cell lines and triggered programmed cell death in melanoma cells.
RQ18 showed selective anticancer activity and triggered multiple signs of apoptosis in laboratory melanoma cells.
The research focused on RQ18, an 18-amino-acid peptide previously investigated for antimicrobial activity. Researchers tested it against murine and human melanoma, cervical cancer, and breast cancer cells, alongside noncancerous cells.
Melanoma cells show strongest sensitivity
RQ18 reduced cancer-cell viability in a dose-dependent manner. The concentration required to inhibit viability by 50% (IC50) was just 4.4 µM/mL in B16F10-Nex2 murine melanoma cells and 11.58 µM/mL in human Sk-mel-28 melanoma cells. The corresponding values were 15.58 µM/mL for HeLa cervical cancer cells, 59.99 µM/mL for A375 melanoma cells, and 120.6 µM/mL for MCF-7 breast cancer cells.
Importantly, RQ18 showed preferential activity against several cancer cell lines compared with noncancerous RAW 264.7 cells. Its selectivity index reached approximately 15.7 for B16F10-Nex2 and 6 for Sk-mel-28 cells. However, selectivity was not universal: the index for MCF-7 cells was only 0.57.
Evidence points toward programmed cell death
As detailed in this
Thailand Medical News report, researchers found multiple signs suggesting that RQ18 activates apoptosis, the controlled process cells use to dismantle themselves.
Caspase-3/7 activity increased approximately 57% in B16F10-Nex2 cells and about 2.4-fold in Sk-mel-28 cells, although A375 cells showed a smaller increase of around 11%. RQ18 also rapidly increased intracellular oxidative activity across all three melanoma models.
Further experiments revealed cell rounding, loss of adhesion, chromatin condensation and reduced mitochondrial membrane potential. Flow cytometry provided particularly notable evidence: approximately 55% of treated B16F10-Nex2 cells were classified as being in late apoptosis.
Computer simulations additionally suggested that RQ18 can interact stably with cancer-like lipid membranes while maintaining its alpha-helical structure.
The researchers are from the Federal University of Mato Grosso do Sul, Dom Bosco Catholic University, and Catholic University of Brasília, Brazil.
Conclusions
The findings suggest RQ18 can selectively attack certain melanoma cells while activating oxidative, mitochondrial, and apoptotic processes. However, these are predominantly laboratory cell experiments, and animal studies are still needed to establish antitumor effectiveness, pharmacokinetics, biodistribution, and safety before any potential clinical application.
The study findings were publishe
d in the peer reviewed journal: Pharmaceuticals.
https://www.mdpi.com/1424-8247/19/10/1521
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https://www.thailandmedical.news/articles/peptides
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