Biology subjects

Hedrick, C. C.

Publications and source records attributed to Hedrick, C. C..

10 recordsLinked to original sources

bioRxiv2026

GTP biosynthesis is a therapeutic vulnerability in Rac1-mutant melanoma

Metastatic melanoma remains highly lethal despite advances in immunotherapy and MAPK-targeted therapy. The Rac1P29S mutation, present in 4-9% of cutaneous melanomas, confers intrinsic resistance to BRAF and MEK inhibitors. Like other small GTPases, Rac1 lacks suitable pockets for small molecule inhibitor binding, motivating indirect approaches to suppressing its activity. We have previously shown that wild-type Rac1 is sensitive to inhibition of de novo GTP biosynthesis in cancer cells, particularly suppression of the rate-limiting inosine monophosphate dehydrogenase (IMPDH) enzymes. Therefore, we asked whether IMPDH inhibition could suppress Rac1P29S and its associated phenotypes in melanoma. We found that IMPDH inhibition reduced Rac1 activity, impaired Rac1-dependent phenotypes, and induced S-phase arrest in Rac1P29S-harboring cells. Moreover, IMPDH inhibition synergized with the BRAF inhibitor vemurafenib and the MEK inhibitor trametinib in Rac1P29S melanoma cells. Dual BRAF and IMPDH inhibition also resulted in enhanced suppression of MEK and ERK phosphorylation in vitro. In syngeneic mouse models, the FDA-approved IMPDH inhibitor mycophenolate mofetil sensitized Rac1P29S-expressing melanoma tumors to trametinib, including tumors made refractory by prior trametinib exposure. We further identified a feed-forward circuit in which Rac1 sustains IMPDH2 expression levels through JNK and c-Jun/AP1 signaling, potentially coupling the GTPase to its own nucleotide supply. These findings establish GTP biosynthesis as a targetable vulnerability in Rac1P29S melanoma and support IMPDH inhibition as a rational partner for MAPK-targeted therapy.

cancer biology↗

bioRxiv2026

S100A9-Dependent CXCR2hi Neutrophils Mediate Systemic Immune Suppression and Checkpoint Resistance in Metastatic TNBC

Most high-dimensional studies of tumor-immune interactions focus on metastatic models, limiting insight into how immune remodeling in primary tumors shapes metastatic competence. Here, integrating single-cell RNA sequencing, CyTOF, and functional studies across metastatic (4T1) and non-invasive (EMT6) triple-negative breast cancer (TNBC) murine models, we define tumor state-specific immune programs that distinguish metastatic competence. Tumors with metastatic capacity uniquely drive early bone marrow expansion of CXCR2 neutrophils, which infiltrate primary tumors acquiring a CXCL2-producing phenotype that promotes EMT-associated cancer stem cell (CSC) plasticity. This program depends on TGF-{beta}/CEBPD-mediated induction of S100A9. Elevated CXCL2, together with G-CSF, establishes a feed-forward circuit that drives systemic neutrophil mobilization and recruitment to distant organs, where neutrophil-derived S100A8/A9 (calprotectin) promotes MET-driven CSC outgrowth and metastatic colonization. Clinically, gene signatures associated with CXCR2 neutrophils predict poor survival in TNBC patients, whereas monocyte/macrophage (CX3CR1) and T cell activation signatures correlate with improved outcomes. S100A9 ablation disrupts this cascade and enhances immunotherapy responsiveness, defining a TGF-{beta}/S100A9/CXCR2 axis linking immune remodeling, CSC plasticity and metastasis. HighlightsO_LIMetastatic TNBC engages a TGF-{beta}/C/EBP{delta}/S100A9 axis that expands CXCR2 neutrophils C_LIO_LINon-invasive EMT6 tumors retain a CX3CR1 monocyte/macrophage and T-cell landscape C_LIO_LICXCR2+ neutrophils in pre-metastatic niches suppress T cell response while promoting tumor cell proliferation C_LIO_LIS100A9 loss redirects myelopoiesis and potentiates anti-PD-L1 in TNBC models C_LI In BriefAlkan et al. dissect how tumor state programs the myeloid compartment in TNBC. Metastatic 4T1 tumors uniquely engage a TGF-{beta}/C/EBP{delta}/S100A9 axis driving CXCR2 neutrophil expansion and CXCL2/G-CSF-dependent systemic mobilization, coupling immune remodeling to EMT/MET cancer-stem-cell plasticity, while S100A9 loss restores CX3CR1 myeloid identity and unlocks checkpoint-inhibitor responsiveness.

cancer biology↗

bioRxiv2026

Targeting phosphodiesterase 10A disrupts MAPK signaling pathways in the tumor microenvironment to unleash antitumor immunity

Phosphodiesterase 10A (PDE10A), a cyclic nucleotide-degrading enzyme, is overexpressed in various human cancers. While PDE10A inhibition using small-molecule inhibitors or gene silencing suppresses tumor growth in xenograft models, its precise mechanism of action and immunological impact remain unclear. Here, we report that ADT-030, a novel PDE10A inhibitor, exhibits potent cytotoxicity against a broad range of murine tumor cell lines. ADT-030 is orally bioavailable and effectively suppresses tumor growth across multiple syngeneic mouse models. Notably, its efficacy is diminished in immunodeficient mice or upon CD8+ T cell depletion, highlighting a critical dependence on host immunity. The immunostimulatory properties of ADT-030 are further supported by its ability to induce immunogenic tumor cell death and promote dendritic cell (DC) maturation, its reliance on Batf3-expressing DCs to elicit antitumor CD8+ T cell response, and its synergy with anti-PD-1 therapy. Comprehensive immune profiling in the 4T1 breast cancer model, both in orthotopic and metastatic settings, revealed that ADT-030 selectively reduces myeloid-derived suppressor cells (MDSCs) while normalizing the immune landscape within the tumor. Mechanistically, ADT-030 disrupts multiple components of the mitogen-activated protein kinase (MAPK) signaling network in both tumor cells and MDSCs, leading to induction of apoptosis in these populations. These findings highlight the multi-faceted impact of PDE10A inhibition as a therapeutic strategy that not only disrupts tumor-intrinsic oncogenic signaling to inhibit tumor progression but also reshapes the tumor immune microenvironment to unleash antitumor immunity.

immunology↗

bioRxiv2026

Indomethacin exerts both cyclooxygenase inhibition-dependent and independent mechanisms to enhance chemo-immunotherapy in mice

Nonsteroidal anti-inflammatory drugs (NSAIDs) primarily act by inhibiting cyclooxygenases (COX1 and COX2), thereby reducing production of the proinflammatory mediator prostaglandin E2 (PGE2). Because PGE2 is a critical driver of cancer progression and tumor immune evasion, this has motivated interest in combining NSAIDs with chemotherapy or immunotherapy for cancer treatment. However, since COX and PGE2 levels vary across tumor types, it remains unclear whether tumor PGE2 abundance solely dictates tumor response to NSAID-based therapies. Here, we investigated the therapeutic potential of indomethacin (Indo), a prototypical NSAID, in combination with cyclophosphamide (CTX), a widely used chemotherapeutic agent with immunostimulatory properties. Metronomic administration of Indo significantly enhanced the antitumor efficacy of CTX in multiple murine tumor models exhibiting variable COX2 and PGE2 levels, including CT26, MC38, 4T1 and A20. The antitumor effects of CTX+Indo required CD8 T cells and T-cell trafficking from tumor-draining lymph nodes and were further potentiated by anti-PD-1 blockade. Single-cell RNA sequencing (scRNA-seq) revealed that responsive CT26 tumors exhibited a reprogrammed tumor immune microenvironment (TIME), marked by increased effector CD8 T-cell infiltration, reduced immunosuppressive myeloid populations, and enhanced interferon signaling in tumor cells. Importantly, Indo retained therapeutic benefit following CTX even in tumors incapable of producing PGE2, demonstrating a critical contribution of COX-independent mechanisms, particularly inhibition of tumor-intrinsic oncogenic RAS signaling, to the enhanced efficacy of the CTX+Indo combination. Collectively, our results provide strong preclinical rationale for leveraging the COX/PGE2 and RAS dual inhibitory capacities of NSAIDs to enhance the efficacy of chemotherapy and immunotherapy.

immunology↗

bioRxiv2022

Modeling the evolutionary history of nonclassical monocytes in mammals

The immune system has experienced major changes in both its organization and function during the evolution of tetrapod animals. Still, the ancestry of specific cell types and the historical relationships between modern immune cells has received little attention. While all tetrapods possess mononuclear blood cells and monocytes, vasculature-patrolling nonclassical monocytes (CD16+CD14- in humans, Ly6C- in mice) have so far only been described in mammals. The question of whether nonclassical monocytes are specific to the mammalian lineage has not been answered. Cell types can be described as traits that persist via the inheritance of core regulatory complexes of transcription factors. We utilized transcriptional network analyses on a human monocyte single-cell RNA-sequencing dataset to highlight the core regulatory complex associated with nonclassical monocyte production (nCoRC). We then applied BLAST-based analyses to quantify the conservation of human nCoRC members amongst mammals and nonmammals. We determined that the average sequence similarity of nCoRC members is highest amongst mammals and that such conservation is not observed in non-mammalian tetrapods. We also discovered that this sequence similarity is specifically driven by boreoeutherian placental mammals. Finally, we found the receptor proteins upstream of nonclassical monocyte assembly are also more homologous in mammals than non-mammals. This work provides an evolutionary model in which the capacity for nonclassical monocyte production is unique to the mammalian lineage.

evolutionary biology↗

bioRxiv2022

Sex differences in coronary artery disease and diabetes revealed by scRNA-Seq and CITE-Seq of human CD4+ T cells

BackgroundDespite the decades-old knowledge that diabetes mellitus (DM) is a major risk factor for cardiovascular disease (CVD), the reasons for this association are only partially understood. Among the immune cells involved in CVD development, accumulating evidence supports the critical role of T cells as drivers and modifiers of this condition. CD4+ T cells are commonly found in atherosclerotic plaques. The activity and distribution of CD4+ T cell subsets differs between the sexes. MethodsPeripheral blood mononuclear cells (PBMCs) of 61 men and women who underwent cardiac catheterization were interrogated by single cell RNA sequencing (scRNA-Seq, [~]200,000 cells) combined with 49 protein markers (CITE-Seq). Coronary artery disease (CAD) was quantified using Gensini scores, with scores above 30 considered CAD+ and below 6 considered CAD-. Four pairs of groups were matched for clinical and demographic parameters. To test how DM changed cell proportions and gene expression, we compared matched groups of diabetic and non-diabetic subjects. We analyzed 41,782 single CD4+ T cell transcriptomes for sex differences in 61 mostly statin-treated coronary artery disease patients with and without DM. ResultsWe identified 16 clusters in CD4 T cells. The proportion of cells in CD4 cluster 8 (CD4T8, CCR2+ Em) was significantly decreased in CAD+, especially among DM+ participants. The proportions of cells in CD4T2, CD4T11, CD4T16 were increased and CD4T13 was decreased in CAD+ among DM+Statin+ participants. CD4T12 was increased in DM+ participants. In female participants, CD4T8, 12, and 13 were decreased compared to in male participants. In CD4 T cells, 31 genes showed significant and coordinated upregulation in both CAD and DM. The DM gene signature was partially additive to the CAD gene signature. ConclusionsWe conclude that CAD and DM are clearly reflected in PBMC transcriptomes and that significant differences exist between women and men and between subjects treated with statins or not.

immunology↗

bioRxiv2020

Combined protein and transcript single cell RNA sequencing reveals cardiovascular disease and HIV signatures

Cryopreserved peripheral blood mononuclear cells (PBMCs) are frequently collected and provide disease- and treatment-relevant data in clinical studies. Here, we developed combined protein (40 antibodies) and transcript single cell (sc)RNA sequencing in PBMCs. Among 31 participants in the WIHS Study, we sequenced 41,611 cells. Using Boolean gating followed by Seurat UMAPs and Louvain clustering, we identified 58 subsets among CD4 T, CD8 T, B, NK cells and monocytes. This resolution was superior to flow cytometry, mass cytometry or scRNA-sequencing without antibodies. Since the transcriptome was not needed for cell identification, combined protein and transcript scRNA-Seq allowed for the assessment of disease-related changes in transcriptomes and cell type proportion. As a proof-of-concept, we showed such differences between healthy and matched individuals living with HIV with and without cardiovascular disease. In conclusion, combined protein and transcript scRNA sequencing is a suitable and powerful method for clinical investigations using PBMCs.

immunology↗

bioRxiv2020

Interplay of Monocytes and T Lymphocytes in COVID-19 Severity

The COVID-19 pandemic represents an ongoing global crisis that has already impacted over 13 million people. The responses of specific immune cell populations to the disease remain poorly defined, which hinders improvements in treatment and care management. Here, we utilized mass cytometry (CyTOF) to thoroughly phenotype peripheral myeloid cells and T lymphocytes from 30 convalescent patients with mild, moderate, and severe cases of COVID-19. We identified 10 clusters of monocytes and dendritic cells and 17 clusters of T cells. Examination of these clusters revealed that both CD14+CD16+ intermediate and CD14dimCD16+ nonclassical monocytes, as well as CD4+ stem cell memory T (TSCM) cells, correlated with COVID-19 severity, coagulation factor levels, and/or inflammatory indicators. We also identified two nonclassical monocyte subsets distinguished by expression of the sugar residue 6-Sulfo LacNac (Slan). One of these subsets (Slanlo, nMo1) was depleted in moderately and severely ill patients, while the other (Slanhi, nMo2) increased with disease severity and was linked to CD4+ T effector memory (TEM) cell frequencies, coagulation factors, and inflammatory indicators. Intermediate monocytes tightly correlated with loss of naive T cells as well as an increased abundance of effector memory T cells expressing the exhaustion marker PD-1. Our data suggest that both intermediate and non-classical monocyte subsets shape the adaptive immune response to SARS-CoV-2. In summary, our study provides both broad and in-depth characterization of immune cell phenotypes in response to COVID-19 and suggests functional interactions between distinct cell types during the disease. One Sentence SummaryUse of mass cytometry on peripheral blood mononuclear cells from convalescent COVID-19 patients allows correlation of distinct monocyte and T lymphocyte subsets with clinical factors.

immunology↗

bioRxiv2019

Lack of apolipoprotein A1 impairs optimal regulatory T cell homeostasis at steady state due to impaired IL-2 signaling

Apolipoprotein A1 (ApoA1), the major constituent of the high-density lipoprotein (HDL) molecule, exhibits anti-inflammatory properties. Our laboratory has previously shown that ApoA1 protects against switching of regulatory T (Treg) cells to atherogenic T follicular helper cells in Western diet-fed mice. However, the role of ApoA1 in modulating Treg cell homeostasis in the absence of atherosclerosis remains uncharacterized. Here, we show that ApoA1 is required for normal Treg cell homeostasis and functioning at steady state. Specifically, lack of ApoA1 decreased the numbers of both natural and induced Treg cells and also lowered Treg cell-based homeostatic proliferation and suppressive functions. Importantly, these changes occurred without affecting other T cell populations. Finally, we determined that the observed phenotypes were caused by changes to cholesterol content and reduced interleukin-2 (IL-2) receptor signaling in ApoA1-deficient Treg cells. Overall, our results show that ApoA1-HDL is necessary for Treg cell homeostasis and functioning.

immunology↗

bioRxiv2019

Bone marrow transplantation rescues monocyte recruitment defect and improves cystic fibrosis in mice

One Sentence SummaryIn this study, we demonstrate that correcting the monocyte adhesion defect in CFTR{Delta}F508 mice (CF mice) by bone marrow transplantation significantly improved survival and reduced inflammation.\n\nAbstractCystic fibrosis (CF) is an inherited life-threatening disease accompanied by repeated lung infections and multi-organ inflammation that affects tens of thousands of people worldwide. The causative gene, cystic fibrosis transmembrane conductance regulator (CFTR), is mutated in CF patients. Monocytes from CF patients show a deficiency in integrin activation and adhesion. Since monocytes play critical roles in controlling infections, defective monocyte function may contribute to CF progression. In this study, we demonstrate that monocytes from CFTR{Delta}F508 mice (CF mice) show defective adhesion under flow. Transplanting CF mice with wild-type bone marrow after sublethal irradiation replaced most (60-80%) CF monocytes with wild-type monocytes, significantly improved survival, and reduced inflammation. Wild-type/CF mixed bone marrow chimeras directly demonstrated defective CF monocyte recruitment to the bronchoalveolar lavage and the intestinal lamina propria in vivo. Our findings show that providing wild-type monocytes by bone marrow transfer rescues gastrointestinal (GI) mortality in CF mice, suggesting that wild-type bone marrow stem cells might mitigate CF inflammation.

immunology↗