Capivasertib combines with docetaxel to enhance anti-tumour activity through inhibition of AKT-mediated survival mechanisms in prostate cancer

Background/objective To explore the anti-tumour activity of combining AKT inhibition and docetaxel in PTEN protein null and WT prostate tumours. Methods Mechanisms associated with docetaxel capivasertib treatment activity in prostate cancer were examined using a panel of in vivo tumour models and cell lines. Results Combining docetaxel and capivasertib had increased activity in PTEN null and WT prostate tumour models in vivo. In vitro short-term docetaxel treatment caused cell cycle arrest in the majority of cells. However, a sub-population of docetaxel-persister cells did not undergo G2/M arrest but upregulated phosphorylation of PI3K/AKT pathway effectors GSK3β, p70S6K, 4E-BP1, but to a lesser extent AKT. In vivo acute docetaxel treatment induced p70S6K and 4E-BP1 phosphorylation. Treating PTEN null and WT docetaxel-persister cells with capivasertib reduced PI3K/AKT pathway activation and cell cycle progression. In vitro and in vivo it reduced proliferation and increased apoptosis or DNA damage though effects were more marked in PTEN null cells. Docetaxel-persister cells were partly reliant on GSK3β as a GSK3β inhibitor AZD2858 reversed capivasertib-induced apoptosis and DNA damage. Conclusion Capivasertib can enhance anti-tumour effects of docetaxel by targeting residual docetaxel-persister cells, independent of PTEN status, to induce apoptosis and DNA damage in part through GSK3β.