Biology subjects

Melenhorst, J. J.

Publications and source records attributed to Melenhorst, J. J..

3 recordsLinked to original sources

bioRxiv2025

MCL1 may not mediate chemoresistance

The anti-apoptotic BCL2 family member MCL1 is overexpressed in many cancers and has been linked to chemoresistance. Unlike other BCL2 family members, MCL1 displays both well-defined mitochondrial anti-apoptotic activities and also emerging nuclear functions. Prior reports suggest that MCL1 enters the nucleus during chemotherapy and promotes chemoresistance by influencing cell cycle progression and DNA repair. These nuclear roles of MCL1, however, remain poorly characterized. Using a newly validated monoclonal antibody across several cell lines and treatments, we find no evidence that MCL1 enhances chemoresistance or preferentially accumulates in the nucleus after drug exposure. Proximity biotinylation identified novel nuclear MCL1 interactors but did not recover previously reported DNA repair or cell cycle partners. Thus, while MCL1 does reach the nucleus and interact with nuclear proteins, our data do not support a role for MCL1 in chemoresistance. Further work is needed to clarify the functional significance of nuclear MCL1. SIGNFIGANCEPrevious studies have implicated MCL1 in promoting chemoresistance via interactions with DNA repair machinery in the nucleus. Using a validated, monoclonal anti-MCL1 antibody, we were unable to replicate these data. We report that MCL1 neither confers chemoresistance, translocates to the nucleus during chemotherapy treatment, nor interacts with DNA repair proteins in live cancer cells.

cell biology↗

bioRxiv2024

TET2 regulates early and late transitions in exhausted CD8+ T-cell differentiation and limits CAR T-cell function

CD8+ T-cell exhaustion hampers disease control in cancer and chronic infections and limits efficacy of T-cell-based therapies, such as CAR T-cells. Epigenetic reprogramming of CAR T-cells by targeting TET2, a methylcytosine dioxygenase that mediates active DNA demethylation, has shown therapeutic potential; however, the role of TET2 in exhausted T-cell (TEX) development is unclear. In CAR T-cell exhaustion models and chronic LCMV infection, TET2 drove the conversion from stem cell-like, self-renewing TEX progenitors towards terminally differentiated and effector (TEFF)-like TEX. In mouse T-cells, TET2-deficient terminally differentiated TEX retained aspects of TEX progenitor biology, alongside decreased expression of the transcription factor TOX, suggesting that TET2 potentiates terminal exhaustion. TET2 also enforced a TEFF-like terminally differentiated CD8+ T-cell state in the early bifurcation between TEFF and TEX, indicating a broad role for TET2 in mediating the acquisition of an effector biology program that could be exploited therapeutically. Finally, we developed a clinically actionable strategy for TET2- targeted CAR T-cells, using CRISPR/Cas9 editing and site-specific adeno-associated virus transduction to simultaneously knock-in a CAR at the TRAC locus and a functional safety switch within TET2. Disruption of TET2 with this safety switch in CAR T-cells restrained terminal TEX differentiation in vitro and enhanced anti-tumor responses in vivo. Thus, TET2 regulates pivotal fate transitions in TEX differentiation and can be targeted with a safety mechanism in CAR T-cells for improved tumor control and risk mitigation. One Sentence SummaryModulation of exhausted CD8+ T-cell differentiation by targeting TET2 improves therapeutic potential of CAR T-cells in cancer.

immunology↗

bioRxiv2021

Decade-long remissions of leukemia sustained by the persistence of activated CD4+ CAR T-cells

The adoptive transfer of T lymphocytes reprogrammed to target tumor cells has demonstrated significant potential in various malignancies. However, little is known about the long-term potential and the clonal stability of the infused cells. Here, we studied the longest persisting CD19-redirected chimeric antigen receptor (CAR) T cells to date in two chronic lymphocytic leukemia (CLL) patients who achieved a complete remission in 2010. CAR T-cells were still detectable up to 10+ years post-infusion, with sustained remission in both patients. Surprisingly, a prominent, highly activated CD4+ population developed in both patients during the years post-infusion, dominating the CAR T-cell population at the late time points. This transition was reflected in the stabilization of the clonal make-up of CAR T-cells with a repertoire dominated by few clones. Single cell multi-omics profiling via Cellular Indexing of Transcriptomes and Epitopes by Sequencing (CITE-Seq) with TCR sequencing of CAR T-cells obtained 9.3 years post-infusion demonstrated that these long-persisting CD4+ CAR T-cells exhibited cytotoxic characteristics along with strong evidence of ongoing functional activation and proliferation. Our data provide novel insight into the CAR T-cell characteristics associated with long-term remission in leukemia.

immunology↗