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Published on: September 19, 2018
CDK4/6 Alters TBK1 Phosphorylation to Inhibit the STING Signaling Pathway in Prostate Cancer
Wei Li1,2, Feng Guo3, Ruijiang Zeng1,2
1Department of Urology, The Second Xiangya Hospital, Central South University, Changsha, China.
Abstract:
The efficacy of immunotherapy in patients with prostate cancer is limited due to the "cold" tumor microenvironment and the paucity of neoantigens. The STING-TBK1-IRF3 signaling axis is involved in innate immunity and has been increasingly recognized as a candidate target for cancer immunotherapy. Here, we found that treatment with CDK4/6 inhibitors stimulates the STING pathway and enhances the antitumor effect of STING agonists in prostate cancer. Mechanistically, CDK4/6 phosphorylated TBK1 at S527 to inactivate the STING signaling pathway independent of RB1 in prostate cancer cells. CDK4/6-mediated phosphorylation of RB1 at S249/T252 also induced the interaction of RB1 with TBK1 to diminish the phosphorylation of TBK1 at S172, which suppressed STING pathway activation. Overall, this study showed that CDK4/6 suppresses the STING pathway through RB1-dependent and RB1-independent pathways, indicating that CDK4/6 inhibition could be a potential strategy to overcome immunosuppression in prostate cancer. Significance: Inhibiting CDK4/6 activates STING-TBK1-IRF3 signaling in prostate cancer by regulating TBK1 phosphorylation, suggesting that the combination of CDK4/6 inhibitors and STING agonists could be an effective approach to stimulate innate immunity.
Insights
Inhibiting CDK4/6 activators can stimulate the STING pathway in prostate cancer. This approach enhances immunotherapy by overcoming the cold tumor microenvironment, offering a new strategy for cancer treatment.
Area of Science:
- Oncology
- Immunology
- Molecular Biology
Background:
- Prostate cancer immunotherapy efficacy is limited by "cold" tumors and few neoantigens.
- The STING-TBK1-IRF3 signaling axis is crucial for innate immunity and a potential cancer immunotherapy target.
Purpose of the Study:
- To investigate the effect of CDK4/6 inhibitors on the STING pathway in prostate cancer.
- To elucidate the mechanisms by which CDK4/6 inhibition impacts STING signaling.
Main Methods:
- Treatment of prostate cancer cells with CDK4/6 inhibitors.
- Analysis of STING pathway activation and TBK1 phosphorylation.
- Investigation of RB1-dependent and independent pathways.
Main Results:
- CDK4/6 inhibitors stimulate the STING pathway in prostate cancer.
- CDK4/6 inactivates STING signaling via TBK1 phosphorylation (S527) independently of RB1.
- CDK4/6-mediated RB1 phosphorylation inhibits STING activation by reducing TBK1 phosphorylation (S172).
Conclusions:
- CDK4/6 inhibition represents a potential strategy to overcome prostate cancer immunosuppression.
- Combining CDK4/6 inhibitors with STING agonists may enhance innate immunity and antitumor effects.
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