The multi-subunit Nucleosome Remodeling and Deacetylase (NuRD) complex consists of seven subunits, each of which comprises two or three paralogs in vertebrates. These paralogs define mutually exclusive and functionally distinct complexes. In addition, several proteins in the complex are multimeric, which complicates structural studies. Attempts to purify sufficient amounts of endogenous complex or recombinantly reconstitute the complex for structural studies has proven quite challenging. Until now, only substructures of individual domains or proteins and low resolution densities of (partial) complexes have been reported. In this study, we comprehensively investigated the relative orientation of different subunits within the NuRD complex using multiple cross-link IP mass spectrometry (xIP-MS) experiments. Our results confirm that the core of the complex is formed by MTA, Accepted Article This article is protected by copyright. All rights reserved RBBP and HDAC proteins. Assembly of a copy of MBD and GATAD2 onto this core enables binding of the peripheral CHD and CDK2AP proteins. Furthermore, our experiments reveal that not only CDK2AP1, but also CDK2AP2 interacts with the NuRD complex. This interaction requires the C-terminus of CHD proteins. Our data provide a more detailed understanding of the topology of the peripheral NuRD subunits relative to the core complex.

The development of immunotherapy, in particular immune checkpoint inhibitors (ICI), has revolutionized cancer treatment in the past decades. However, its efficacy is still limited to subgroups of patients with cancer. Therefore, effective treatment combination strategies are needed. Here, radiotherapy is highly promising, as it can induce immunogenic cell death, triggering the release of pro-inflammatory cytokines, thereby creating an immunogenic phenotype and sensitizing tumors to ICI. Recently, targeted radionuclide therapy (TRT) has attained significant interest for cancer treatment. In this approach, a tumor-targeting radiopharmaceutical is used to specifically deliver a therapeutic radiation dose to all tumor cells, including distant metastatic lesions, while limiting radiation exposure to healthy tissue. However, fundamental differences between TRT and conventional radiotherapy make it impossible to directly extrapolate the biological effects from conventional radiotherapy to TRT. In this review, we present a comprehensive overview of studies investigating the immunomodulatory effects of TRT and the efficacy of combined TRT-ICI treatment. Preclinical studies have evaluated a variety of murine cancer models in which α- or β-emitting radionuclides were directed to a diverse set of targets. In addition, clinical trials are ongoing to assess safety and efficacy of combined TRT-ICI in patients with cancer. Taken together, research indicates that combining TRT and ICI might improve therapeutic response in patients with cancer. Future research has to disclose what the optimal conditions are in terms of dose and treatment schedule to maximize the efficacy of this combined approach.

Novel approaches to reduce tumor immunosuppression and improve responses to anti-cancer immunotherapies based on immune-checkpoint inhibitors are needed. Emerging evidence demonstrates that autophagy inhibition enhances anti-tumor immunity by tumor cell-intrinsic and extrinsic mechanisms. Recently, we reported that pharmacological inhibition of VPS34 (PIK3C3), a lipid kinase regulating autophagy initiation, decreases tumor growth and improve the efficacy of anti-PD-1/PD-L1 therapy in melanoma and colorectal cancer mouse models. This effect was dependent on increasing T and NK cell infiltration as well as the expression of CCL5 and CXCL10 chemokines in the tumor microenvironment. Here, we explored the signaling mechanisms underlying the chemokine release following treatment with VPS34 inhibitor SB02024. We found that both pharmacological and RNAi-mediated inhibition of VPS34 activated a cGAS-STING-dependent type I interferon response in renal cell carcinoma (RCC) and melanoma cell lines. Furthermore, combination treatment of VPS34 inhibitor SB02024 with STING agonist ADU-S100 or cGAMP increased the mRNA expression and release of proinflammatory cytokines in human and murine RCC and melanoma cancer cell lines. Oral administration of SB02024 in combination with intratumoral injections of ADU-S100 significantly decreased tumor growth and weight and improved mice survival of B16-F10 tumor-bearing mice. Taken together, our data demonstrates that targeting of VPS34 results in a cGAS/STING-mediated increase of pro-inflammatory cytokine secretion and synergizes with a STING agonist. We believe that systemic VPS34 inhibition using SB02024 would be of major interest in combination or as an alternative to STING agonists to improve anti-tumor immune responses. Citation Format: Yasmin Yu, Muhammad Z. Noman, Santiago Parpal, Simone C. Kleinendorst, Kristine B. Saether, Andrey Alexeyenko, Jenny Viklund, Martin Andersson, Jessica Martinsson, Katja P. Tamm, Angelo De Milito, Bassam Janji. VPS34 inhibitor SB02024 activates cGAS-STING signaling and sensitizes tumors to STING agonist [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2116.