The post by dexy1234 and reply by PjOshea indicates the anti cancer properties of HDAC inhibitors. Valerian may have similar properties.

[Graham49]

Only in vitro for breast cancer but there's also a 2020 paper for liver cancer.

Published: 28 January 2021

Valerian and valeric acid inhibit growth of breast cancer cells possibly by mediating epigenetic modifications

Fen Gin Shi, Ya Li, Rui Han, Alan Fu, Ronghua Wang, Olivia Nusbaum, Qin Qin, Xinyi Chen, Li Hou & Yong Zhu

Scientific Reports volume 11, Article number: 2519 (2021)

Abstract

Valerian root (Valeriana officinalis) is a popular and widely available herbal supplement used to treat sleeping disorders and insomnia. The herb’s ability to ameliorate sleep dysfunction may signify an unexplored anti-tumorigenic effect due to the connection between circadian factors and tumorigenesis. Of particular interest are the structural similarities shared between valeric acid, valerian's active chemical ingredient, and certain histone deacteylase (HDAC) inhibitors, which imply that valerian may play a role in epigenetic gene regulation. In this study, we tested the hypothesis that the circadian-related herb valerian can inhibit breast cancer cell growth and explored epigenetic changes associated with valeric acid treatment. Our results showed that aqueous valerian extract reduced growth of breast cancer cells. In addition, treatment of valeric acid was associated with decreased breast cancer cell proliferation, migration, colony formation and 3D formation in vitro in a dose- and time-dependent manner, as well as reduced HDAC activity and a global DNA hypomethylation. Overall, these findings demonstrate that valeric acid can decrease the breast cancer cell proliferation possibly by mediating epigenetic modifications such as the inhibition of histone deacetylases and alterations of DNA methylation. This study highlights a potential utility of valeric acid as a novel HDAC inhibitor and a therapeutic agent in the treatment of breast cancer.

[LearnAll]

Valerian root acts by increasing GABA (Gamma Amino Butyric Acid) transmission in the Brain and this is how it reduces anxiety and promotes sleep. Medicines like Valium, Ativan, klonopin etc also act by the same mechanism.The positive effect on PCa might be related to Valerian's promoting good sleep. People with cancer need at least 7 hours of sleep at night.

[Graham49 in reply to LearnAll]

Valerian may well benefit cancer treatment by improving sleep, however the paper I posted was an invitro study of valerian on cancer cells.