Kim, Sungjune

Abstract BACKGROUND: Tumor-specific T cells are often characterized by reduced TCR signaling due to central and peripheral tolerance pathways that limit their responsiveness. These signals are further weakened by insufficient co-stimulation and active co-inhibitory pathways, collectively establishing a high threshold for activation. The integration of antigen recognition with co-stimulatory and inhibitory cues ultimately determines whether a T cell becomes activated or remains tolerant. Early TCR signaling must therefore be precisely regulated to prevent autoreactivity while still supporting protective immunity. Although phosphorylation and ubiquitination are well-established regulators of proximal TCR signaling, additional post-translational mechanisms remain less defined. SIRT2, a cytosolic NAD+-dependent deacetylase with emerging roles in immune regulation, has not been examined in the context of TCR signaling. METHODS: We evaluated proximal TCR signaling events in wild-type and SIRT2-deficient T cells using flow cytometry, immunoblotting, calcium flux assays, and RNA-sequencing. SIRT2-associated pathways were defined by mapping its interactome and acetylated substrates through mass spectrometry and immunoprecipitation. We screened LCK post-translational modifications by mass spectrometry and assessed SIRT2 enzymatic activity using an HPLC-based deacetylase assay. Conformational effects of LCK modification were examined using fluorescence-polarization binding assays and AlphaFold structural modeling. SIRT2 was deleted in human tumor infiltrating lymphocytes (TILs) via CRISPR/Cas9, and the impact of SIRT2 targeting was tested in lung cancer patient-derived xenograft models reconstituted with autologous TILs. RESULTS: SIRT2 deficiency amplified proximal TCR signaling, leading to elevated phosphorylation of early signaling mediators and increased calcium flux in both naïve and anergic T cells. Loss of SIRT2 also altered thymic selection dynamics and expanded TCR repertoire diversity. Mechanistically, SIRT2 interacted with and deacetylated LCK, the initiating kinase of proximal TCR signaling. Mass spectrometry identified lysine K228 in the LCK linker region as a SIRT2-regulated deacetylation site that governs LCK conformation and kinase activity. Functionally, SIRT2 inhibition in exhausted mouse and human TILs restored TCR signaling capacity and improved anti-tumor responses. CONCLUSION: Here we identify SIRT2-regulated deacetylation of LCK as a previously unrecognized mechanism that sets the strength and threshold of proximal TCR signaling. Accordingly, SIRT2 targeting reverses the exhausted phenotype of tumor-reactive T cells. Citation Format: Imene Hamaidi, Pingyan Cheng, Soo Young Jun, Min-Hsuan Wang, Min Zhang, Odesha Taylor, Luis Lopez-bailon, Ismail Can, Bin Fang, Anders Berglund, Bradford Perez, Ben Creelan, Andriy Marusyk, Virginia Shapiro, Haitao Ji, Jose R. Conejo-Garcia, Sungjune Kim. Sirt2 dictates TCR activation thresholds through post-translational control of LCK conformational state [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 4250.

The immunosuppressive tumor microenvironment (TME) remains a major barrier to effective cancer immunotherapy. Among the central regulators of immune suppression, CD38, a multifunctional ectoenzyme and surface glycoprotein, has emerged as a pivotal orchestrator. CD38 is abundantly expressed on regulatory T cells (Tregs), regulatory B cells (Bregs), myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs), and tumor-associated neutrophils (TANs), where it enhances survival, metabolic fitness, and suppressive activity. Invariant natural killer T (iNKT) cells, which can either promote or suppress antitumor immunity, also express CD38 upon activation, suggesting a role for CD38 in directing their context-dependent fate within the TME. Mechanistically, CD38 regulates immune suppression through NAD + hydrolysis, calcium signaling, and promotion of fatty acid oxidation (FAO) while impairing effector T-cell glycolysis and mitochondrial fitness under chronic hypoxia—conditions that favor exhaustion rather than enhanced cytotoxicity. By depleting extracellular NAD + , CD38 diminishes glycolysis and mitochondrial oxidative phosphorylation in effector T cells, while sustaining regulatory cell persistence through FAO. Its enzymatic products, cyclic ADP-ribose (cADPR) and NAADP, further mobilize calcium fluxes that reinforce suppressive function. CD38 also integrates with hypoxia-driven pathways; in CD38 + Bregs, stabilization of HIF-1α and induction of FAO-related genes such as CPT1A and PPARα/γ promote angiogenesis, immune-evasion, and therapeutic resistance. Therapeutically, targeting CD38 with monoclonal-antibodies, small-molecule inhibitors, or combinations with checkpoint blockade and macrophage-reprogramming agents has shown promise. Such interventions reverse immune suppression, restore effector T cell activity, and enhance tumor responsiveness to immunotherapy. In summary, CD38 functions as both a metabolic regulator and an immunologic checkpoint, coordinating suppressive networks and shaping iNKT cell fate. These multifaceted roles position CD38 as a transformative target for next-generation immunotherapies.

Localized cutaneous squamous cell carcinoma (cSCC) has a favorable prognosis, unlike advanced disease, especially with clinical perineural invasion (PNI), which poses substantial management challenges due to aggressivity and higher recurrence, metastasis, and mortality risks. PNI, a high-risk staging feature, has worse outcomes, particularly when clinically evident rather than incidental. Clinical PNI (cPNI) is evident by clinical symptoms (such as pain, paresthesia, or motor deficits) or radiologic findings, whereas incidental PNI (iPNI) is identified only histologically without associated symptoms or radiologic evidence. PNI remains a novel area with varying practice patterns across institutions. Improving risk stratification and tailoring multidisciplinary approaches are critical for optimizing outcomes. Our review outlines clinical practice patterns at our institution, providing insights into managing cSCC with PNI, focusing on diagnosis, imaging, staging, and emerging immunotherapies. A structured search was conducted using the terms “perineural invasion,” “cutaneous squamous cell carcinoma,” and “immunotherapy.” cPNI has a poor prognosis and requires nuanced clinical decision-making. Surgery and radiation remain central to management. Adjuvant therapy offers substantial survival benefit in cSCC with PNI, with improved disease-free and overall survival compared with surgery alone, supporting its use in appropriately selected high-risk patients. Traditional systemic therapies, including cisplatin and cetuximab, remain foundational but have shown only moderate response rates and limited durability in advanced or neurotropic cSCC. In contrast, immunotherapy—now preferred for advanced or unresectable cases—has transformed management, with programmed cell death protein-1 (PD-1) inhibitors showing promising results (up to 69% response rate) and disease stabilization. Neoadjuvant immunotherapy may enable tumor downstaging, improve radiation planning, and reduce surgical morbidity. Imaging for squamous cell carcinoma (SCC) with PNI aids staging and surveillance, but symptoms remain key for detecting recurrence. Our multidisciplinary approach emphasizes personalized care. Larger trials are needed to define the optimal role and sequencing of immunotherapy in this high-risk patient population.

ABSTRACT Background As head and neck cancer survival rates improve, there is growing demand for quality survivorship care and tools to predict patient adherence; this study aims to evaluate an advanced practice provider ( APP )‐led survivorship clinic and assess these key metrics. Methods We performed a retrospective review of 213 head and neck cancer patients treated with curative radiation therapy between 2016 and 2023, to assess follow‐up adherence in an advanced practice provider–led survivorship clinic. Results With a median follow‐up of 2.4 years, follow‐up care metrics identified high completion percentages (> 90%) for lung cancer screening, smoking cessation, thyroid screening, dental evaluation, xerostomia, dysphagia, and dysgeusia. The HOUsing ‐based SocioEconomic Status ( HOUSES ) index at diagnosis showed a significant adherence difference (median percentile, 78% vs. 55%, adherent vs. nonadherent; p = 0.03). Conclusions High adherence rates with guideline‐defined care metrics are achievable in an advanced practice provider‐led head and neck cancer survivorship clinic. The HOUSES index may assist in predicting nonadherence; however, further studies are needed.

Abstract Background: While cancer immunotherapies have revolutionized treatment, their efficacy remains limited for most patients, highlighting tumors' capacity to evade immune detection. Epigenetic modifications, particularly DNA methylation, play a pivotal role in silencing immune-related pathways, thereby facilitating immune escape. By modulating gene expression, methylation disrupts immune activation, contributing to reduced tumor immunogenicity. This study examines the methylation landscape of co-stimulatory and immune checkpoint genes across various cancers to elucidate how these changes influence immune responses. Methods: Using The Cancer Genome Atlas (TCGA), we analyzed methylation and gene expression profiles across diverse cancer types. Data from 8,186 solid tumors and 745 adjacent normal tissues were processed via t-distributed stochastic neighbor embedding (t-SNE) with 247 probes targeting 20 immune-related genes. Principal component analysis (PCA) was applied to capture methylation variability across 8,931 tumor and normal samples. To explore the effects of methylation on immune gene expression, we analyzed data from 26 epithelial cancer cell lines treated with 5-azacitidine, a demethylating agent, using the GSE57342 dataset. Post-treatment changes in gene expression were assessed, and survival analyses from prior studies were used to explore clinical correlations. Results: We identified distinct methylation patterns in immune synapse genes, differentiating tumors from adjacent normal tissues. Co-stimulatory genes such as CD40 were hypermethylated in tumors, correlating with decreased expression, whereas immune checkpoint genes like PDL1 and HHLA2 were hypomethylated, correlating with increased expression. This inverse relationship between methylation and gene expression underscores the transcriptional regulatory role of DNA methylation. Treatment with 5-azacitidine reversed hypermethylation in co-stimulatory genes, including CD40, potentially enhancing immune recognition. Methylation levels of these genes were also associated with T cell infiltration into the tumor microenvironment and predicted better outcomes in melanoma patients, underscoring their clinical relevance. Conclusion: This study demonstrates that DNA methylation of immune synapse genes contributes to tumor immune evasion by modulating immune gene expression. Targeting these epigenetic alterations represents a promising strategy to restore tumor immunogenicity and improve immunotherapy outcomes, particularly when combined with immune checkpoint inhibitors. Reversing methylation-driven immune suppression could strengthen the immune response and enhance clinical outcomes for cancer patients. Citation Format: Imene Hamaidi, Anders Berglund, Matthew Mills, Ryan M. Putney, James J. Mulé, Sungjune Kim. DNA methylation of immune synapse genes drives tumor immune evasion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4831.