Biology subjects

Mulkey, J. S.

Publications and source records attributed to Mulkey, J. S..

3 recordsLinked to original sources

bioRxiv2026

Engineering antigen-driven co-stimulation and T helper cell activity into TCR-T cells with CD8-41BB fusion receptors enhances anti-tumor activity

1Adoptive cell therapy using tumor antigen-targeting T cell receptors (TCRs) offers a compelling approach to treat both hematological cancers and solid tumors due to broad antigen accessibility and the ability to target cancer-specific neoantigens. However, unlike clinically validated second generation CAR-T cells bearing built-in co-stimulatory signaling modules (i.e. 41BB or CD28), TCR-T cells receive little to no co-stimulation within most tumor microenvironments leading to attenuated cellular responses. Additionally, CD4+ TCR-T cells engineered to express HLA-Class I restricted TCRs possess minimal T-helper cell activity and thus do not effectively mobilize CD8+ TCR-T cells or host anti-tumor immune responses. To address these limitations, we used CRISPR-Cas9 to engineer TCR-T cells with targeted integration of chimeric CD8 constructs containing intracellular co-stimulatory domains. We found that expression of wild-type CD8{beta}, but not CD8, could promote CD4+ T cell activities in HLA-Class I restricted TCR-T cells. However, this was insufficient to drive durable anti-tumor responses in challenging tumor mouse models when using a high-affinity WT1-directed TCR. To address this, several CD8 co-stimulatory fusion constructs containing CD28 or 41BB intracellular domains were designed and screened, identifying two CD8-41BB based chimeras that substantially increased TCR-T cell activity relative to wild-type CD8{beta}. WT1-TCR-T cells co-expressing the CD8-41BB fusions demonstrated not only enhanced CD4+ activity including strong and polarized Th1-type cytokine secretion, but also enhanced the proliferation, cytokine release, and cytotoxicity of CD8+ CTLs. Remarkably, when combined with TGFBR2 gene disruption, WT1-TCR-T cells co-expressing CD8-41BB receptors were able to completely regress established cell line-derived ovarian tumors, showed robust in vivo expansion and persistence, and provided long-term protection from tumor rechallenge. Importantly, the specificity profile of the WT1-TCR including its HLA-A*02:01 restriction and WT1 peptide recognition motif was preserved upon expression of CD8-41BB. To simplify cell engineering processes for clinical applications, we configured a homology directed repair (HDR) cassette to allow for efficient CRISPR-Cas9-based insertion of both the TCR and CD8-41BB transgenes in the TRAC locus in a single step with >80% efficiency. Lastly, the enhanced activity conferred by CD8-41BB expression was validated with a second clinically relevant TCR targeting PRAME, suggesting this platform can be a universal approach for enhancing the therapeutic potential of TCR-based cell therapies.

synthetic biology↗

bioRxiv2026

Azacytidine restores T cell function in AML by modulating DNA methylation

AML is an aggressive blood cancer associated with poor clinical outcomes. Chemotherapy remains the standard of treatment, but unfortunately relapse is very common, highlighting the need for alternative therapies. T cell dysfunction and exhaustion are prominent in AML and may represent a barrier to effective immunotherapy yet remains poorly studied in AML. DNA methylation is a major driver of T cell exhaustion and inhibition of de novo methylation can block exhaustion and restore T cell function in chronic viral infections and other cancers but is understudied in AML. Here, we investigated the impact of azacytidine (Aza), an FDA-approved hypomethylating agent, on T cell exhaustion in AML. Using a spontaneous AML mouse model and samples from patients with AML, we found that Aza treatment modulates T cell function. In vivo Aza-treatment of AML-bearing mice decreased tumor burden and reshaped CD8+ T cell states, with increases in frequencies of memory subsets and decreases in regulatory T cells (Tregs). Functionally, Aza treatment overcame the impaired proliferation displayed by both CD4 and CD8+ T cells in our model. DNA methylation sequencing of T cells after Aza treatment revealed hypomethylation and increased expression of stem-like precursor gene TCF7 and E2F2, a regulator of cell cycle progression and proliferation. Similar changes in phenotypes were observed in cultures of AML patient samples treated with Aza. Collectively, we show that Aza remodels epigenetic and functional states in AML and has the potential to reverse T cell exhaustion, with enhanced memory and proliferation capacity. Our work generates a mechanistic framework that provides rationale of combining hypomethylating agents with T cell-based immunotherapies in this lethal disease. Data Sharing StatementRRBS data is available in GEO under the accession number GSE328721. For original data please contact Dr. Evan F. Lind. Key PointsAzacytidine mediated epigenetic modulation can alleviate T cell exhaustion in AML Translational RelevanceImmune therapy has shown limited efficacy in AML, despite increasing evidence of T cell dysfunction in this malignancy. Azacytidine (Aza) is an FDA approved drug for AML, but patients develop therapy resistance and relapse. Studies have mainly focused on Azas tumor intrinsic effects. In this study, we investigated the impact of Aza on immune function, especially T cell exhaustion in AML, since exhaustion is a major mechanism of disease resistance. We demonstrated that Aza can modulate T cell phenotype and restore T cell proliferation. Mechanistically, Aza induces epigenetic reprogramming in T cells and increases the expression of a stem-like precursor marker, TCF7. By shifting the focus on T cell biology, our study provides a rationale for combining Aza with other immunotherapies that can enhance durable immune responses in this malignancy.

immunology↗

bioRxiv2023

Leukemic mutation FLT3-ITD is retained in dendritic cells and disrupts their homeostasis leading to expanded Th17 frequency

Dendritic cells (DC) are mediators of adaptive immune responses to pathogens and tumors. DC development is determined by signaling through the receptor tyrosine kinase Fms-like tyrosine kinase 3 (FLT3) in bone marrow myeloid progenitors. Recently the naming conventions for DC phenotypes have been updated to distinguish between "Conventional" DCs (cDCs) and plasmacytoid DCs (pDCs). Activating mutations of FLT3, including Internal Tandem Duplication (FLT3-ITD), are associated with poor prognosis for leukemia patients. To date, there is little information on the effects of FLT3-ITD in DC biology. We examined the cDC phenotype and frequency in bone marrow aspirates from patients with acute myeloid leukemia (AML) to understand the changes to cDCs associated with FLT3-ITD. When compared to healthy donor (HD) we found that a subset of FLT3-ITD+ AML patient samples have overrepresented populations of cDCs and disrupted phenotypes. Using a mouse model of FLT3-ITD+ AML, we found that cDCs were increased in percentage and number compared to control wild-type (WT) mice. Single cell RNA-seq identified FLT3-ITD+ cDCs as skewed towards a cDC2 T-bet-phenotype, previously shown to promote Th17 T cells. We assessed the phenotypes of CD4+ T cells in the AML mice and found significant enrichment of both Treg and Th17 CD4+ T cells. Furthermore, co-culture of AML mouse- derived DCs and naive OT-II cells preferentially skewed T cells into a Th17 phenotype. Together, our data suggests that FLT3-ITD+ leukemia-associated cDCs polarize CD4+ T cells into Th17 subsets, a population that has been shown to be negatively associated with survival in solid tumor contexts. This illustrates the complex tumor microenvironment of AML and highlights the need for further investigation into the effects of FLT3-ITD mutations on DC phenotypes.

immunology↗