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Supplementary Data from Vitamin E Enhances Cancer Immunotherapy by Reinvigorating Dendritic Cells via Targeting Checkpoint SHP1

Despite the popular use of dietary supplements during conventional cancer treatments, their impacts on the efficacies of prevalent immunotherapies, including immune-checkpoint therapy (ICT), are unknown. Surprisingly, our analyses of electronic health records revealed that ICT-treated patients with cancer who took vitamin E (VitE) had significantly improved survival. In mouse models, VitE increased ICT antitumor efficacy, which depended on dendritic cells (DC). VitE entered DCs via the SCARB1 receptor and restored tumor-associated DC functionality by directly binding to and inhibiting protein tyrosine phosphatase SHP1, a DC-intrinsic checkpoint. SHP1 inhibition, genetically or by VitE treatment, enhanced tumor antigen cross-presentation by DCs and DC-derived extracellular vesicles (DC-EV), triggering systemic antigen-specific T-cell antitumor immunity. Combining VitE with DC-recruiting cancer vaccines or immunogenic chemotherapies greatly boosted ICT efficacy in animals. Therefore, combining VitE supplement or SHP1-inhibited DCs/DC-EVs with DC-enrichment therapies could substantially augment T-cell antitumor immunity and enhance the efficacy of cancer immunotherapies.Significance:The impacts of nutritional supplements on responses to immunotherapies remain unexplored. Our study revealed that dietary vitamin E binds to and inhibits DC checkpoint SHP1 to increase antigen presentation, prime antitumor T-cell immunity, and enhance immunotherapy efficacy. VitE-treated or SHP1-silenced DCs/DC-EVs could be developed as potent immunotherapies.This article is highlighted in the In This Issue feature, p. 1599

Despite the popular use of dietary supplements during conventional cancer treatments, their impacts on the efficacies of prevalent immunotherapies, including immune-checkpoint therapy (ICT), are unknown. Surprisingly, our analyses of electronic health records revealed that ICT-treated patients with cancer who took vitamin E (VitE) had significantly improved survival. In mouse models, VitE increased ICT antitumor efficacy, which depended on dendritic cells (DC). VitE entered DCs via the SCARB1 receptor and restored tumor-associated DC functionality by directly binding to and inhibiting protein tyrosine phosphatase SHP1, a DC-intrinsic checkpoint. SHP1 inhibition, genetically or by VitE treatment, enhanced tumor antigen cross-presentation by DCs and DC-derived extracellular vesicles (DC-EV), triggering systemic antigen-specific T-cell antitumor immunity. Combining VitE with DC-recruiting cancer vaccines or immunogenic chemotherapies greatly boosted ICT efficacy in animals. Therefore, combining VitE supplement or SHP1-inhibited DCs/DC-EVs with DC-enrichment therapies could substantially augment T-cell antitumor immunity and enhance the efficacy of cancer immunotherapies. Significance: The impacts of nutritional supplements on responses to immunotherapies remain unexplored. Our study revealed that dietary vitamin E binds to and inhibits DC checkpoint SHP1 to increase antigen presentation, prime antitumor T-cell immunity, and enhance immunotherapy efficacy. VitE-treated or SHP1-silenced DCs/DC-EVs could be developed as potent immunotherapies. This article is highlighted in the In This Issue feature, p. 1599

Major neoplastic diseases have high incidences of brain metastasis (BrM) which is a clinically dreadful consequence of advanced cancers with an abysmal prognosis. Unfortunately, our understanding of the biology and molecular mechanisms underlying BrM remains rudimentary. Improving our understanding of the pathogenesis of BrM will facilitate the rational development and prioritization of new therapeutic strategies. Mitogen-activated protein kinases (MAPKs) are a group of serine/threonine protein kinases that are key players in various intracellular signaling pathways controlling many cellular processes, e.g., growth, differentiation, stress responses, and immune defense which have a key role in cancer progression. However, little is known regarding the role of MAPKs in the pathogenesis of BrM. Here, we report that p38γ mitogen-activated protein kinase (MAPK12) is overexpressed in multiple tumor types and associated with aggressive breast cancer progression and a poor outcome in BrM patients. Interestingly, we found that the lack of p38γ did not impact the proliferation of tumor cells ex vivo, but significantly reduced both the primary tumor growth and BrM in EO771 and other mammary tumor-bearing immunocompetent mouse models. Our preclinical data indicated that p38γ promoted tumor progression and BrM through remodeling tumor microenvironments in vivo. We have mapped the immune landscape of BrM lesions of EO771-bearing mice using high-dimensional single-cell profiling. Clearly, cytometry by time-of-flight (CyTOF) analysis of the BrM immune infiltrates revealed reprogramming of the immunosuppressive brain microenvironment toward a proinflammatory and antitumoral state with tumor-intrinsic p38γ depletion, as indicated by highly enriched dendritic cell (DC) and cytolytic T cell (CTL) populations in BrM. To explore the impact of p38γ depletion in breast cancer cells, we performed RNA sequencing on EO771 cells having p38γ knocked down versus the control cells. We found that p38γ knocked down led to the upregulation of pathways related to immune cell movement, thereby leading to an increased accumulation of antitumor immune cells in BrM. Together, our findings uncover an important role for tumor-intrinsic p38γ in shaping the brain immune microenvironment and underscore the potential of specific p38γ blockade in enhancing antitumor immunity for the treatment of breast cancer BrM. Citation Format: Xiangliang Yuan, Hao-Nien Chen, Akosua Badu-Nkansah, Yimin Duan, Dihua Yu. p38γ MAPK remodels tumor microenvironment facilitating breast cancer progression and brain metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 673.

The functions of immune cells in brain metastases are unclear because the brain has traditionally been considered “immune privileged.” However, we discovered that a subgroup of immunosuppressive neutrophils is recruited into the brain, enabling brain metastasis development. In brain metastatic cells, enhancer of zeste homologue 2 (EZH2) is highly expressed and phosphorylated at tyrosine-696 (pY696-EZH2) by nuclear-localized Src tyrosine kinase. Phosphorylation of EZH2 at Y696 changes its binding preference from histone H3 to RNA polymerase II, which consequently switches EZH2’s function from a methyltransferase to a transcription factor that increases c-JUN expression. c-Jun upregulates pro-tumorigenic inflammatory cytokines, including granulocyte-colony stimulating factor (G-CSF), which recruits Arg1-positive and PD-L1-positive immunosuppressive neutrophils into the brain to drive metastasis outgrowth. G-CSF-blocking antibodies or immune checkpoint blockade therapies combined with Src inhibitors impeded brain metastasis in multiple mouse models. These findings indicate that pY696-EZH2 can function as a methyltransferase-independent transcription factor to facilitate the brain infiltration of immunosuppressive neutrophils, which could be clinically targeted for brain metastasis treatment.

Both DNA and chromatin need to be duplicated during each cell division cycle. Replication happens in the context of defects in the DNA template and other forms of replication stress that present challenges to both genetic and epigenetic inheritance. The replication machinery is highly regulated by replication stress responses to accomplish this goal. To identify important replication and stress response proteins, we combined isolation of proteins on nascent DNA (iPOND) with quantitative mass spectrometry. We identified 290 proteins enriched on newly replicated DNA at active, stalled, and collapsed replication forks. Approximately 16% of these proteins are known replication or DNA damage response proteins. Genetic analysis indicates that several of the newly identified proteins are needed to facilitate DNA replication, especially under stressed conditions. Our data provide a useful resource for investigators studying DNA replication and the replication stress response and validate the use of iPOND combined with mass spectrometry as a discovery tool. Background: DNA replication and the replication stress response require the coordinated actions of many proteins. Results: iPOND coupled with mass spectrometry identified 290 proteins associated with active, stalled, or collapsed replication forks. Conclusion: iPOND-MS is a useful discovery tool. Significance: The data increase our understanding of the network of proteins involved in DNA replication and the replication stress response.

Elongation factor 4 is a widely distributed translational GTPase also known as LepA. Its physiological role is ambiguous, as only a few phenotypes resulting from lepA null mutations have been reported. Here, we report that a Streptomyces coelicolor lepA null mutant overproduces the calcium-dependent antibiotic (CDA). Our findings are the first that connect LepA (encoded by SCO2562) to antibiotic production. They lend additional evidence that perturbations in the quaternary structure and function of the ribosome can positively affect antibiotic production in Streptomyces bacteria.

Schimke Immunoosseous Dysplasia (SIOD) is a rare, autosomal recessive disorder of childhood with classical features of spondyloepiphyseal dysplasia, renal failure, and T cell immunodeficiency. SIOD has been associated with several malignancies, including non-Hodgkin lymphoma and osteosarcoma. About half of SIOD patients have biallelic mutations in SMARCAL1 (SWI/SNF-related matrix-associated actin-dependent regulator of chromatin, subfamily a-like 1). This gene encodes an annealing helicase and replication stress response protein that localizes to damage-stalled DNA replication forks. We report a child with SIOD and a novel S859P missense mutation in SMARCAL1 who developed undifferentiated carcinoma of the sinus.

Schimke Immunoosseous Dysplasia (SIOD) is a rare, autosomal recessive disorder of childhood with classical features of spondyloepiphyseal dysplasia, renal failure, and T cell immunodeficiency. SIOD has been associated with several malignancies, including non-Hodgkin lymphoma and osteosarcoma. About half of SIOD patients have biallelic mutations in SMARCAL1 (SWI/SNF-related matrix-associated actin-dependent regulator of chromatin, subfamily a-like 1). This gene encodes an annealing helicase and replication stress response protein that localizes to damage-stalled DNA replication forks. We report a child with SIOD and a novel S859P missense mutation in SMARCAL1 who developed undifferentiated carcinoma of the sinus.

SMARCAL1 (SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily A-like1) maintains genome integrity during DNA replication. Here we investigated its mechanism of action. We found that SMARCAL1 travels with elongating replication forks, and its absence leads to MUS81-dependent double-strand break formation. Binding to specific nucleic acid substrates activates SMARCAL1 activity in a reaction that requires its HARP2 (Hep-A-related protein 2) domain. Homology modeling indicates that the HARP domain is similar in structure to the DNA-binding domain of the PUR proteins. Limited proteolysis, small-angle X-ray scattering, and functional assays indicate that the core enzymatic unit consists of the HARP2 and ATPase domains that fold into a stable structure. Surprisingly, SMARCAL1 is capable of binding three-way and four-way Holliday junctions and model replication forks that lack a designed ssDNA region. Furthermore, SMARCAL1 remodels these DNA substrates by promoting branch migration and fork regression. SMARCAL1 mutations that cause Schimke immunoosseous dysplasia or that inactivate the HARP2 domain abrogate these activities. These results suggest that SMARCAL1 continuously surveys replication forks for damage. If damage is present, it remodels the fork to promote repair and restart. Failures in the process lead to activation of an alternative repair mechanism that depends on MUS81-catalyzed cleavage of the damaged fork.

Elongation factor 4 is a widely distributed translational GTPase also known as LepA. Its physiological role is ambiguous, as only a few phenotypes resulting from lepA null mutations have been reported. Here, we report that a Streptomyces coelicolor lepA null mutant overproduces the calcium-dependent antibiotic (CDA). Our findings are the first that connect LepA (encoded by SCO2562) to antibiotic production. They lend additional evidence that perturbations in the quaternary structure and function of the ribosome can positively affect antibiotic production in Streptomyces bacteria.