Biology subjects

Heltemes-Harris, L. M.

Publications and source records attributed to Heltemes-Harris, L. M..

4 recordsLinked to original sources

bioRxiv2025

PDL1 CHECKPOINT BLOCKADE SYNERGIZES WITH NILOTINIB BUT NOT DASATINIB TO PREVENT LEUKEMIA RELAPSE

Dasatinib and nilotinib are front line Tyrosine Kinase Inhibitors (TKIs) used to treat BCR-ABL+ B cell acute lymphoblastic leukemia (B-ALL) and BCR-ABL+ chronic myelogenous leukemia. We previously showed that combining nilotinib with anti-PD-L1 blockade significantly reduced leukemia relapse. The TKI dasatinib is more commonly used to treat to B-ALL. However, unlike nilotinib, dasatinib also inhibits SRC-family kinases, which may make it less efficacious in combination with anti-PDL1 blockade. Herein we assess the impact of nilotinib versus dasatinib on anti-leukemia immune responses. Dasatinib, but not nilotinib, inhibited T cell proliferation at high doses in-vitro, but neither TKI significantly impacted T cell function or expansion in response to immunization in-vivo with a model antigen (2W1S) plus polyIC-adjuvant. Dasatinib and nilotinib both reduced leukemic blasts equivalently after 5 days of treatment. In contrast, nilotinib and PD-L1 blockade, but not dasatinib plus anti-PDL1, prevented relapse several weeks later. Thus, dasatinib negatively impacts protective anti-leukemia T cell responses that prevent leukemia relapse.

immunology↗

bioRxiv2020

Identification of mutations that cooperate with defects in B cell transcription factors to initiate leukemia

The transcription factors EBF1 and PAX5 are frequently mutated in B cell acute lymphoblastic leukemia (B-ALL). We demonstrate that Pax5+/- x Ebf1+/- compound heterozygous mice develop highly penetrant leukemia. Similar results were seen in Pax5+/- x Ikzf1+/- and Ebf1+/- x Ikzf1+/- mice for B-ALL, or in Tcf7+/- x Ikzf1+/- mice for T cell leukemia. To identify genetic defects that cooperate with Pax5 and Ebf1 compound heterozygosity to initiate leukemia, we performed a Sleeping Beauty (SB) transposon screen that identified cooperating partners including gain-of-function mutations in Stat5 ([~]65%) and Jak1([~]68%), or loss-of-function mutations in Cblb (61%) and Myb (32%). These findings underscore the role of JAK/STAT5 signaling in B cell transformation and demonstrate unexpected roles for loss-of-function mutations in Cblb and Myb in leukemic transformation. RNA-Seq studies demonstrated upregulation of a PDK1>SGK3>MYC pathway; treatment of Pax5+/- x Ebf1+/- leukemia cells with PDK1 inhibitors blocked proliferation in vitro. Finally, we identified conserved transcriptional variation in a subset of genes between human leukemias and our mouse B-ALL models. Thus, compound haploinsufficiency for B cell transcription factors likely plays a critical role in transformation of human B cells and suggest that PDK1 inhibitors may be effective for treating patients with such defects.

cancer biology↗

bioRxiv2020

Single-cell analysis of developing B cells reveals dynamic gene expression networks that govern B cell development and transformation

SummaryIntegration of external signals and B-lymphoid transcription factor activities orchestrate B cell lineage commitment through alternating cycles of proliferation and differentiation, producing a diverse repertoire of mature B cells. We used single-cell transcriptomics and proteomics to characterize B cell development. Our analysis revealed unique transcriptional signatures that refine the pre-B cell expansion stages into novel pre-BCR-dependent and pre-BCR-independent proliferative phases. These changes correlate with unexpected dynamic and reciprocal changes in expression of the transcription factor EBF1 and the RNA binding protein YBX3, that are defining features of the pre-BCR-dependent stage. Using pseudotime analysis, we further characterize the expression kinetics of different biological modalities across B cell development, including transcription factors, cytokines, chemokines, and their associated receptors. Our findings reveal the underlying heterogeneity of developing B cells and point to key developmental nodes linked to B cell transformation.Competing Interest StatementThe authors have declared no competing interest.View Full Text

immunology↗

bioRxiv2017

B-1a cells acquire their unique characteristics by bypassing the pre-BCR selection stage

B-1a cells are long-lived, self-renewing innate like B cells that predominantly inhabit the peritoneal and pleural cavities. In contrast to conventional B-2 cells they have a receptor repertoire that is biased towards bacterial and self-antigens, promoting a rapid response to infection and clearing of apoptotic cells. Although B-1a cells are known to primarily originate from fetal tissues the mechanisms by which they arise has been a topic of debate for many years. Here we show that in the fetal liver (FL) versus bone marrow (BM) environment, reduced IL-7R/STAT5 levels promote immunoglobulin kappa (Igk) recombination at the early pro-B cell stage. As a result, B cells can directly generate a mature B cell receptor (BCR) and bypass the requirement for a pre-BCR and pairing with surrogate light chain (SLC). This alternate pathway of development enables the production of B cells with self reactive, skewed specificity receptors that are peculiar to the B-1a compartment. Together our findings connect seemingly opposing models of B-1a cell development and explain how these cells acquire their unique properties.

immunology↗