Biology subjects

Olejniczak, S. H.

Publications and source records attributed to Olejniczak, S. H..

3 recordsLinked to original sources

bioRxiv2026

Multidirectional Cellular Plasticity in Ewing Sarcoma Reveals a Tumor-CAF Continuum and Novel Immunotherapeutic Targets

Ewing sarcoma (EwS) is an aggressive pediatric malignancy with poor outcomes for patients with metastatic or relapsed disease. Effective immunotherapeutic approaches, including CAR T-cell therapy, are limited by intratumoral heterogeneity, an incompletely characterized tumor microenvironment (TME), and a lack of well-defined, tumor-restricted target antigens. To address these limitations, we performed an integrated analysis of EwS tumor samples using both single-nucleus and single-cell RNA sequencing datasets derived exclusively from patient samples, including matched primary tumors and orthotopic patient-derived xenograft (PDX) models. Our analyses reveal that primary EwS tumors are largely composed of highly heterogeneous malignant cell populations occupying multiple, multidirectional transcriptional states, including neuronal-like, proliferative, angiogenic, and fibroblast-like. We demonstrate that the EwS TME contains both classical cancer-associated fibroblasts (CAFs) and abundant EwS CAF-like tumor cells that transcriptionally resemble stromal cells while retaining tumor identity. Trajectory analyses define a progressive and coordinated tumor-CAF continuum, marked by gradual loss of neuronal programs and activation of mesenchymal and extracellular matrix remodeling programs, suggesting dynamic tumor cell reprogramming that may promote invasion, immune evasion, and therapeutic resistance. Notably, this structured transcriptional continuum was prominent in primary tumors but largely absent in matched PDX models, underscoring the importance of native tumor context for capturing clinically relevant tumor-TME interactions. We also developed a systematic surface-antigen discovery pipeline and identified ten novel putative tumor-associated surface target antigens (TAs), LRRC15, ATP2B3, CACNA1I, DCHS2, DSEL, LPAR4, PRRT4, TMEM229A, UNC5A, and UNC79, none of which have been previously described in EwS tumor biology. Characterization of these surface TAs revealed distinct expression patterns across EwS tumor cells, EwS CAF-like tumor cells, and classical CAFs. Moreover, some TAs expression differed between primary and metastatic tumors and between primary patient samples and matched PDX models, highlighting the critical importance of first validating therapeutic targets in primary tissues (PT). Together, these findings redefine the cellular architecture of EwS by revealing a dynamic tumor-CAF continuum that is uniquely preserved in primary tumors and establishes a framework for identifying clinically relevant tumor-associated surface TAs. These results provide a foundation for the rational development of next-generation immunotherapies and precision-targeted therapies for patients with EwS.

cancer biology↗

bioRxiv2024

Endogenous CD28 drives CAR T cell responses in multiple myeloma

Recent FDA approvals of chimeric antigen receptor (CAR) T cell therapy for multiple myeloma (MM) have reshaped the therapeutic landscape for this incurable cancer. In pivotal clinical trials B cell maturation antigen (BCMA) targeted, 4-1BB co-stimulated (BB{zeta}) CAR T cells dramatically outperformed standard-of-care chemotherapy, yet most patients experienced MM relapse within two years of therapy, underscoring the need to improve CAR T cell efficacy in MM. We set out to determine if inhibition of MM bone marrow microenvironment (BME) survival signaling could increase sensitivity to CAR T cells. In contrast to expectations, blocking the CD28 MM survival signal with abatacept (CTLA4-Ig) accelerated disease relapse following CAR T therapy in preclinical models, potentially due to blocking CD28 signaling in CAR T cells. Knockout studies confirmed that endogenous CD28 expressed on BB{zeta} CAR T cells drove in vivo anti-MM activity. Mechanistically, CD28 reprogrammed mitochondrial metabolism to maintain redox balance and CAR T cell proliferation in the MM BME. Transient CD28 inhibition with abatacept restrained rapid BB{zeta} CAR T cell expansion and limited inflammatory cytokines in the MM BME without significantly affecting long-term survival of treated mice. Overall, data directly demonstrate a need for CD28 signaling for sustained in vivo function of CAR T cells and indicate that transient CD28 blockade could reduce cytokine release and associated toxicities.

cancer biology↗

bioRxiv2021

ARS2-directed alternative splicing mediates CD28 driven T cell glycolysis and effector function

CD8 T cell activation prompts extensive transcriptome remodeling underlying effector differentiation and function. Regulation of transcriptome composition by the mitogen-inducible nuclear cap-binding complex (CBC) adaptor protein ARS2 has critical cell type-specific consequences, including thymic T cell survival. Here we show that ARS2 was upregulated by CD28 during activation of peripheral T cells, was essential for anti-tumor immunity, and facilitated T cell activation-induced alternative splicing. The novel splicing function of ARS2 was mediated at least in part by recruitment of splicing factors to nascent transcripts including the M2 isoform of pyruvate kinase (Pkm2), a key determinant of CD8 T cell effector properties. Notably, ARS2-directed Pkm2 splicing occurred days after stimulation of PI3K-indepdendent CD28 signaling and increased glycolysis beyond levels determined by PI3K signaling during T cell priming. Thus, ARS2-directed Pkm2 splicing represents a mechanism by which CD28 drives glycolytic metabolism, allowing for optimal effector cytokine production and T cell anti-tumor immunity.

immunology↗