Doxycycline Shows Preclinical Activity Against Prostate Cancer Bone Metastasis

A new preclinical study suggests that doxycycline, a widely used antibiotic, may help interfere with the process that allows prostate cancer cells to spread and grow in bone.

The researchers identified acetylated KLF5 (Ac-KLF5) as an important driver of bone metastasis. This altered form of KLF5 appears to make prostate cancer cells more invasive and also helps activate osteoclasts, the cells that break down bone and can create a more favourable environment for metastatic growth.
Doxycycline and the related antibiotic methacycline were found to bind this pathway and reduce several of these effects. In laboratory models, they decreased tumour-cell invasion, reduced osteoclast formation and slowed bone metastasis in mice.

The study also identified PGK1 as an important downstream part of the mechanism, suggesting that doxycycline may act through an Ac-KLF5–PGK1 pathway rather than through a general antibiotic effect.
The main attraction is drug repurposing: doxycycline is cheap, widely available and already has extensive safety data in humans. However, these results are still entirely preclinical. There is no evidence yet that doxycycline can prevent or treat prostate cancer bone metastases in patients, or that normal antibiotic doses would be enough to reproduce the effects seen in experimental models.
The next step would be to confirm realistic dosing and identify which tumours depend most strongly on this pathway before testing the idea clinically.

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