BackgroundThe emergence of immunotherapy has revolutionized the paradigm of cancer treatment with immune checkpoint blockades (ICB) in solid cancers, including colorectal cancer (CRC). However, only a small subset of CRC patients harboring deficient mismatch repair (dMMR) or microsatellite instability-high (MSI-H) benefits from ICB therapy. A very limited response to ICB therapy has been achieved in MMR-proficient CRC, representing a significant challenge limiting the clinical application of immunotherapy. MMR is the critical DNA repair pathway that maintains genomic integrity by correcting DNA mismatches, which is mediated by the MutSα or MutSβ complex consisting of MSH2 with MSH6 and MSH3, respectively. Given that MMR status directs effective immune response, we sought to determine whether targeting MMR capacity boosts ICB efficacy.MethodsAzoxymethane/dextran sodium sulfate (AOM/DSS)‐induced CRC and xenograft model were used to evaluate the function of PRMT6 and response to PRMT6 inhibitor EPZ020411 and combination therapy of PD1 and EPZ020411. Biochemical assays were performed to elucidate the underlying mechanism of PRMT6-mediated MSH2 methylation and immune evasion.ResultsWe have identified PRMT6 as a crucial regulator of MMR capacity via MSH2 dimethylation at R171 and R219. Such a modification abrogates its MMR capacity and prevents the recruitment of MSH3 and MSH6. PRMT6 loss or inhibition triggers cytosolic DNA accumulation and cGAS-STING signaling activation, leading to enhanced immune response in PRMT6-deficient colon tumors or xenografts. Pharmacological inhibition of PRMT6 using EPZ020411 promotes mutagenesis and destabilizes MutSα or MutSβ assembly, and prolonged EPZ020411 exposure maintains an MSI-like phenotype in microsatellite stability (MSS) cells. EPZ020411 treatment sensitizes ICB efficacy of MSS cells, but not MSI cells in vivo. Similar effects have been observed in MSS colon tumors induced by AOM/DSS.ConclusionsOur study provides a preclinical proof of concept to overcome resistance to immunotherapy by targeting PRMT6 in CRC with MSS.

2025-03-01·Virology

A high-throughput, microplate reader-based method to monitor in vitro HIV latency reversal in the absence of flow cytometry

Article

作者: Tietjen, Ian ; Liang, Kimberly ; Cassel, Joel ; Ntie-Kang, Fidele ; Montaner, Luis J ; Salvino, Joseph M ; Nkwelle, Chantal Emade ; Stephens, Unique ; Ndip, Roland N ; Esemu, Seraphine N

J-Lat cells are derivatives of the Jurkat CD4⁺ T cell line that contain a non-infectious, inducible HIV provirus with a GFP tag. While these cells have substantially advanced our understanding of HIV latency, their use by many laboratories in low and middle-income countries is restricted by limited access to flow cytometry. To overcome this barrier, we describe a modified J-Lat assay using a standard microplate reader that detects HIV-GFP expression following treatment with latency-reversing agents (LRAs). We show that HIV reactivation by control LRAs like prostratin and romidepsin is readily detected with dose dependence and with significant correlation and sensitivity to standard flow cytometry. For example, 10 μM prostratin induced a 20.1 ± 3.3-fold increase in GFP fluorescence in the microplate reader assay, which corresponded to 64.2 ± 5.0% GFP-positive cells detected by flow cytometery. Similarly, 0.3 μM prostratin induced a 1.7 ± 1.2-fold increase compared to 8.7 ± 5.7% GFP-positive cells detected. Using this method, we screen 79 epigenetic modifiers and identify CUDC-101, molibresib, and quisinostat as novel LRAs. This microplate reader-based method offers accessibility to researchers in resource-limited regions to work with J-Lat cells and more actively participate in global HIV cure research efforts.

2025-01-02·Molecular Cancer Research

B-type Plexins Regulate Mitosis via RanGTPase

Article

作者: Garg, Ritu ; Azad, Abul ; Williamson, Magali ; Mukhwana, Nicholus ; Mitchell, Alexandria R.

AbstractAberrant mitosis can result in aneuploidy and cancer. The small GTPase, Ras-related nuclear protein (Ran), is a key regulator of mitosis. B-type plexins regulate Ran activity by acting as RanGTPase-activating proteins and have been implicated in cancer progression. However, whether B-type plexins have a role in mitosis has not so far been investigated. We show here that Plexin B1 functions in the control of mitosis. Depletion of Plexin B1 affects mitotic spindle assembly, significantly delaying anaphase. This leads to mitotic catastrophe in some cells and prolonged application of the spindle assembly checkpoint. Plexin B1 depletion also promoted acentrosomal microtubule nucleation and defects in spindle pole refocusing and increased the number of cells with multipolar or aberrant mitotic spindles. An increase in lagging chromosomes or chromosomal bridges at anaphase was also found upon Plexin B1 depletion. Plexin B1 localizes to the mitotic spindle in dividing cells. The mitotic defects observed upon Plexin B1 depletion were rescued by an RCC1 inhibitor, indicating that Plexin B1 signals, via Ran, to affect mitosis. These errors in mitosis generated multinucleate cells and nuclei of altered morphology and abnormal karyotype. Furthermore, semaphorin 4D treatment increased the percentage of cells with micronuclei, precursors of chromothripsis.Implications: Defects in B-type plexins may contribute to the well-established role of plexins in cancer progression by inducing chromosomal instability.

100 项与 EPZ020411 相关的药物交易

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