Biology subjects

Slupsky, J. R.

Publications and source records attributed to Slupsky, J. R..

3 recordsLinked to original sources

bioRxiv2023

Soluble CTLA-4 raises the threshold for T-cell activation and modulates anti-tumour immunity

CTLA-4 is a crucial immune checkpoint receptor involved in the maintenance of immune homeostasis, tolerance, and tumour control. Antibodies targeting CTLA-4 have been promising treatment for numerous cancers, but the mechanistic basis of their anti-tumoral immune boosting effects are poorly understood. Although the ctla4 gene also encodes an alternatively-spliced soluble variant (sCTLA-4), preclinical/clinical evaluation of anti-CTLA-4-based immunotherapies have not considered the contribution of this isoform. Here, we explore the functional properties of sCTLA-4 and evaluate the efficacy of isoform-specific anti-sCTLA-4 antibody targeting in murine cancer model. We show that expression of sCTLA-4 in tumour cells suppresses CD8+ T-cells in vitro, and accelerates growth and experimental metastasis of murine tumours in vivo. These effects were accompanied by modification of the immune infiltrate, notably restraining CD8+ T-cells in a non-effector state. sCTLA-4 blockade with isoform-specific antibody reversed this restraint, enhancing intratumoural CD8+ T-cell activation and cytolytic potential, correlating with therapeutic efficacy and tumour control. This previously unappreciated role of sCTLA-4 suggests that better understanding of the biology and function of multi-gene products of immune checkpoint receptors needs to be fully elucidated for improved cancer immunotherapy.

cancer biology↗

bioRxiv2022

PKCβ facilitates leukemogenesis in chronic lymphocytic leukaemia by promoting constitutive BCR-mediated signaling

B cell antigen receptor (BCR) signaling competence is critical for pathogenesis of chronic lymphocytic leukemia (CLL). Defining key proteins that facilitate these networks aid in the identification of targets for therapeutic exploitation. We previously demonstrated that reduced PKC function in mouse hematopoietic stem/progenitor cells (HPSCs) resulted in PKC{beta}II upregulation and generation of a poor-prognostic CLL-like disease. Here, prkcb knockdown in HSPCs leads to reduced survival of PKC-KR-expressing CLL-like cells, concurrent with reduced expression of the leukemic markers CD5 and CD23. SP1 promotes elevated expression of prkcb in PKC-KR expressing cells enabling leukemogenesis. Global gene analysis revealed an upregulation of genes associated with B cell activation in PKC-KR expressing cells, coincident with upregulation of PKC{beta}II: supported by activation of key signaling hubs proximal to the BCR and elevated proliferation. Ibrutinib (BTK inhibitor) or enzastaurin (PKC{beta}II inhibitor) treatment of PKC-KR expressing cells and primary CLL cells showed similar patterns of Akt/mTOR pathway inhibition, supporting the role for PKC{beta}II in maintaining proliferative signals in our CLL mouse model. Ibrutinib or enzastaurin treatment also reduced PKC-KR-CLL cell migration towards CXCL12. Overall, we demonstrate that PKC{beta} expression facilitates leukemogenesis and identify that BCR-mediated signaling is a key driver of CLL development in the PKC-KR model. Statement of SignificancePKC{beta} facilitates leukemogenesis of CLL, driven through an SP1-regulated transcriptional program and promotes BCR signaling. Thus far, PKC{beta} is the only kinase within the BCR signaling pathway, a key pathway in driving CLL pathogenesis, implicated in the generation of neoplastic B lineage cells.

cancer biology↗

bioRxiv2022

Development of a bispecific Antibody Drug Conjugate targeting CD7 and CD33 to treat Acute Myeloid Leukaemia

Acute myeloid leukemia (AML) is a heterogeneous malignancy of the bone marrow associated with poor outcomes and limited treatment options available to patients. Recent developments have demonstrated that patient stratification based on disease classification (e.g. somatic mutations) allows for selective treatment regimens and greatly improved outcomes. AML patients can also be stratified based upon the heterogeneous immunophenotype of surface antigen expression on leukemic blasts and stem cells. Here we present data identifying a sub-population of AML patients showing expression of both CD33 and CD7 on their tumour cells, using mass cytometry. This combination of antigens is disease-specific, and is not expressed on healthy haematopoietic cells in patients. We developed a bispecific antibody-drug conjugate (ADC) targeting both CD7 and CD33 and demonstrate that these bispecific ADCs are cytotoxic to AML cells in vitro. Importantly, the anti-CD33/CD7 bispecific ADCs are more selective than single-antigen targeting ADCs and safely discriminate tumour from healthy cells (either myeloid or lymphoid). These anti-CD33/CD7 bispecific ADCs are well tolerated and selectively target AML cells in pre-clinical in vivo studies in mice. This study presents the first proof-of-principle for targeting specific and unique combinations of surface antigens on tumour cells with potential to overcome observed toxicities with current ADCs.

cancer biology↗