Feng Guo

Despite the advancement in therapies, ovarian cancer treatment is challenging because of poor prognosis and high relapse associated with acquired resistance. Emerging targeted alpha particles, particularly actinium-225 ( ²²⁵ Ac), for treating refractory cancers have opened avenues for improved therapeutic options. Here, we describe a successful example of folate receptor 1 (FOLR1)–targeted ²²⁵ Ac alpha-particle therapy for treatment of ovarian cancer. Longitudinal positron emission tomography imaging demonstrated high tumor-specific uptake of αFOLR1 (anti-FOLR1 antibody) in SKOV3 xenografts. FOLR1-targeted ²²⁵ Ac demonstrated high therapeutic efficacy, achieving marked tumor regression, 80% survival, and 40% complete tumor elimination. The therapy resulted in tumor-specific double-stranded DNA damage, and no obvious toxicity was observed in normal tissues. Estimated human dosimetry showed high absorbed dose for tumor and minimal absorbed dose for healthy tissues, establishing its safety. In totality, FOLR1-targeted ²²⁵ Ac alpha-particle therapy is an efficacious and safe treatment with high feasibility for clinical translation to fight against ovarian cancer.

Pancreatic ductal adenocarcinoma (PDAC) remains one of the deadliest cancers with limited therapeutic options. Dysregulated transcriptional networks are key drivers of its aggressive biology. Here, by integrating clinical datasets with mechanistic studies, we performed a family wide systematic analysis of E2F transcription factors and identified E2F3 as a key oncogenic driver with prognostic significance comparable to E2F1. Functional studies showed that E2F3 accelerates PDAC proliferation and xenograft growth. Mechanistically, E2F3 transcriptionally activates the E3 ligase TRIM26, which binds TAB1, promotes K11-linked polyubiquitination, and facilitates TAB1-TAK1 complex formation to engage canonical NF-κB signaling. The SPRY and RING domains of TRIM26 mediate TAB1 interaction and ubiquitination, respectively. TRIM26 depletion attenuated E2F3 induced NF-κB activation and tumor growth, whereas its restoration rescued these effects. Clinically, E2F3, TRIM26, and phosphorylated p65 levels were positively correlated in PDAC tissues, and therapeutic delivery of siTRIM26 recapitulated NF-κB inhibition. These findings uncover an unrecognized E2F3-TRIM26-TAB1/TAK1-NF-κB signaling axis that links cell cycle regulation with inflammatory activation in PDAC and nominate TRIM26 as a druggable vulnerability to therapeutically decouple this oncogenic crosstalk.

Tyrosine kinase inhibitors (TKI) that can suppress the VEGF signaling pathway and angiogenesis have been developed to impede the progression of malignant tumors and have been approved as first-line targeted agents for clear cell renal cell carcinoma (ccRCC). Dysregulation of lipid metabolism is a major driver of TKI resistance in renal cancer. In this study, we showed that the palmitoyl acyltransferase ZDHHC2 is abnormally upregulated in tissues and cell lines resistant to TKIs, such as sunitinib. Upregulation of ZDHHC2 contributed to sunitinib resistance in cells and mice, and ZDHHC2 regulated angiogenesis and cell proliferation in ccRCC. Mechanistically, ZDHHC2 mediated AGK S-palmitoylation to promote translocation of AGK into the plasma membrane and activation of the PI3K–AKT–mTOR signaling pathway in ccRCC, which modulated sunitinib sensitivity. In conclusion, these results identify a ZDHHC2–AGK signaling axis and suggest that ZDHHC2 is a targetable candidate for improving the antitumor efficacy of sunitinib in ccRCC.Significance:ZDHHC2 confers sunitinib resistance to clear cell renal cell carcinoma by catalyzing AGK palmitoylation to activate the AKT–mTOR pathway.

Tyrosine kinase inhibitors (TKIs) that can suppress the VEGF signaling pathway and angiogenesis have been developed to impede the progression of malignant tumors and have been approved as first-line targeted agents for clear cell renal cell carcinoma (ccRCC). Dysregulation of lipid metabolism is a major driver of TKI resistance in renal cancer. In this study, we showed that the palmitoyl acyltransferase ZDHHC2 is abnormally upregulated in tissues and cell lines resistant to TKIs, such as sunitinib. Upregulation of ZDHHC2 contributed to sunitinib resistance in cells and mice, and ZDHHC2 regulated angiogenesis and cell proliferation in ccRCC. Mechanistically, ZDHHC2 mediated AGK S-palmitoylation to promote translocation of AGK into the plasma membrane and activation of the PI3K-AKT-mTOR signaling pathway in ccRCC, which modulated sunitinib sensitivity. In conclusion, these results identify a ZDHHC2-AGK signaling axis and suggest that ZDHHC2 is a targetable candidate for improving the anti-tumor efficacy of sunitinib in ccRCC.

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.

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.