Targeting PKMYT1 enhances antitumor immune responses in castration-resistant prostate cancer.
Ontology highlight
ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE317406 | GEO | 2026/02/11
REPOSITORIES: GEO
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Project description:Although immunotherapy has been successful in various tumors, its efficacy in castration resistant prostate cancer (CRPC) is minimal, due to reduced presence of intratumoral immune effector cells in CRPC. How CRPC cells escape immune surveillance is not fully defined. Here we demonstrate that PKMYT1 expression is elevated in CRPC cases, which related to low immune infiltration in these patients. Patients with high PKMYT1 expression exhibit low CD8+ T cells signature and resistance to ICB therapy. Targeting PKMYT1 can suppress CRPC progression, accompanied with increased intratumoral CD8+ T cells. Selective PKMYT1 inhibitor, RP-6306, augmented ICB in a manner dependent on CD8+ T cells. PKMYT1 inhibitors alone or in combination with PD-L1 blockade causes CD8+ T cell infiltration and remarkable tumor suppression, which suggests a promising immunotherapeutic approach in CRPC. Mechanically, targeting PKMYT1 activated the cGAS-STING pathway, which increases expression of type I and II interferon response genes and led to upregulation of key immune regulators. These findings highlight a key role of PKMYT1 in CRPC progression and rationalize PKMYT1 as a potential therapeutic target.
2026-02-11 | GSE283458 | GEO
Project description:Although immunotherapy has been successful in various tumors, its efficacy in castration resistant prostate cancer (CRPC) is minimal, due to reduced presence of intratumoral immune effector cells in CRPC. How CRPC cells escape immune surveillance is not fully defined. Here we demonstrate that PKMYT1 expression is elevated in CRPC cases, which related to low immune infiltration in these patients. Patients with high PKMYT1 expression exhibit low CD8+ T cells signature and resistance to ICB therapy. Targeting PKMYT1 can suppress CRPC progression, accompanied with increased intratumoral CD8+ T cells. Selective PKMYT1 inhibitor, RP-6306, augmented ICB in a manner dependent on CD8+ T cells. PKMYT1 inhibitors alone or in combination with PD-L1 blockade causes CD8+ T cell infiltration and remarkable tumor suppression, which suggests a promising immunotherapeutic approach in CRPC. Mechanically, targeting PKMYT1 activated the cGAS-STING pathway, which increases expression of type I and II interferon response genes and led to upregulation of key immune regulators. These findings highlight a key role of PKMYT1 in CRPC progression and rationalize PKMYT1 as a potential therapeutic target.
2026-02-11 | GSE284679 | GEO
Project description:Cyclin E is a regulatory subunit of CDK2 that mediates S phase entry and progression. Cleavage of full-length cyclin E (FL-cycE) to low molecular weight isoforms (LMW-E) dramatically alters the substrate specificity, promoting G1/S cell cycle transition and accelerating mitotic exit. Approximately 70% of triple-negative breast cancers (TNBC) express LMW-E, which correlates with poor prognosis. PKMYT1 also plays an important role in mitosis by inhibiting CDK1 to block premature mitotic entry, suggesting it could be a therapeutic target in TNBC expressing LMW-E. Here, analysis of TNBC patient tumor samples revealed that co-expression of LMW-E and PKMYT1-catalyzed CDK1 phosphorylation predicted poor response to neoadjuvant chemotherapy. Compared to FL-cycE, LMW-E specifically upregulated PKMYT1 expression and protein stability, elevating CDK1 phosphorylation. Inhibiting PKMYT1 with the selective inhibitor RP-6306 (lunresertib) elicited LMW-E dependent antitumor effects, accelerating premature mitotic entry, inhibiting replication fork restart, and enhancing DNA damage, chromosomal breaks, apoptosis, and replication stress. Importantly, TNBC cell line xenografts expressing LMW-E showed greater sensitivity to RP-6306 than tumors with empty vector or FL-cycE. Furthermore, RP-6306 exerted tumor suppressive effects in LMW-E transgenic murine mammary tumors and LMW-E-high TNBC patient-derived xenografts but not in the LMW-E null models examined in parallel. Lastly, transcriptomic and immune profiling demonstrated that RP-6306 treatment induced interferon responses and T-cell infiltration in the LMW-E-high tumor microenvironment, enhancing the antitumor immune response. These findings highlight the LMW-E/PKMYT1/CDK1 regulatory axis as a promising therapeutic target in TNBC, providing the rationale for further clinical development of PKMYT1 inhibitors in this aggressive breast cancer subtype.
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Project description:Targeting cell cycle checkpoints has emerged as a promising strategy in cancer therapy, yet single-agent inhibitors often fail due to compensatory mechanisms. Here, we demonstrate that co-inhibition of ATR (RP-3500) and PKMYT1 (RP-6306) induces synthetic lethality in Rb1-deficient breast cancers by disrupting both S/G2 and G2/M checkpoints, resulting in replication stress, premature mitotic entry, and DNA damage accumulation. In vitro, Rb1-deficient breast cancer cell lines exhibited marked apoptosis and loss of clonogenic potential, whereas Rb1-proficient models remained largely resistant to combination treatment. Genetic manipulation of Rb1 confirmed this dependency: Rb1 knockdown sensitized resistant models, and overexpression conferred protection. In vivo, patient-derived xenograft (PDX) models recapitulated these findings. Rb1-deficient tumors underwent complete regression, while Rb1-proficient tumors showed limited response with RP-3500/RP-6306 treatment. Combination therapy was well tolerated in vivo, without significant toxicity or weight loss. Biomarker analysis revealed increased γH2AX and reduced Ki67 staining exclusively in Rb1-deficient PDX models, underscoring the specificity of this response. Mechanistically, Rb1 loss impaired double-strand DNA repair by attenuating homologous recombination and non-homologous end joining, leading to replication fork collapse, chromosomal instability, and mitotic catastrophe. Proteogenomic analysis identified JNK/p38 stress response pathway activation as a key driver of apoptosis following ATR/PKMYT1 inhibition in Rb1-deficient cells. Clinically, analysis of stage IV breast cancer patient datasets revealed that Rb1-low tumors display reduced DNA repair pathway activity and are enriched in triple-negative and CDK4/6 inhibitor-resistant luminal breast cancers. These findings establish Rb1 loss as a functional biomarker for ATR/PKMYT1-targeted therapy, offering a precision treatment strategy for advanced breast cancers.
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Project description:Endocrine therapies (ET) combined with CDK4/6 inhibition (CDK4/6i) is standard treatment for estrogen receptor-α-positive (ER+) breast cancer, however lethal drug resistance is common. Proteogenomic analyses of 22 ER+ breast cancer patient-derived xenografts (PDXs) demonstrated that PKMYT1, a WEE1 homolog, is highly estradiol (E2) regulated in E2-dependent PDXs and constitutively expressed when growth is E2 independent. In clinical samples, high PKMYT1 mRNA is a resistance biomarker for both ET and CDK4/6 inhibition. The PKMYT1 inhibitor lunresertib(RP-6306) and gemcitabine selectively and synergistically reduced the viability of ET and palbociclib-resistant ER+ breast cancer cells without functional p53 in vitro; the combination increased DNA damage and apoptosis. In palbociclib-resistant, TP53 mutant PDX organoids and xenografts, RP-6306 with low-dose gemcitabine induced greater tumor volume reduction compared to treatment with either single agent. These results demonstrate the clinical potential of RP-6306 in combination with gemcitabine for ET and CDK4/6i resistant TP53 mutant ER+ breast cancer.
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Project description:Solid tumours are highly refractory to immune checkpoint blockade (ICB) therapies due to the functional impairment of effector T cells and their inefficient trafficking to tumours. T-cell activation is negatively regulated by C-terminal Src kinase (CSK); however, the exact mechanism remains unknown. Here we show that the conserved oncogenic tyrosine kinase Activated CDC42 kinase 1 (ACK1) is able to phosphorylate CSK at Tyrosine 18 (pY18), which enhances CSK function, constraining T-cell activation. Mice deficient in the Tnk2 gene encoding Ack1, are characterized by diminished CSK pY18 phosphorylation and spontaneous activation of CD8+ and CD4+ T cells, resulting in inhibited growth of transplanted ICB-resistant tumours. Furthermore, ICB treatment of castration-resistant prostate cancer (CRPC) patients results in re-activation of ACK1/pY18-CSK signalling, confirming the involvement of this pathway in ICB insensitivity. An ACK1 small-molecule inhibitor, (R)-9b, recapitulates inhibition of ICB-resistant tumours, which provides evidence for ACK1 enzymatic activity playing a pivotal role in generating ICB resistance. Overall, our study identifies an important mechanism of ICB resistance and holds potential for expanding the scope of ICB therapy to tumours that are currently unresponsive.
2023-03-11 | PXD037546 | Pride
Project description:PKMYT1 has recently emerged as a compelling therapeutic target for precision cancer therapy due to its synthetic lethality with oncogenic alterations such as CCNE1 amplification and mutations in FBXW7 and PPP2R1A. Current small molecule PKMYT1 inhibitors face limitations, such as insufficient molecular diversity and poor selectivity. We used our generative AI platform to develop a bifunctional PKMYT1 degrader by linking an entirely novel PKMYT1 inhibitor to an optimized cereblon (CRBN) binder. The lead PROTAC D16-M1P2 demonstrated dual mechanisms of PKMYT1 degradation and antagonism, with strong antiproliferative potency facilitated by high selectivity. It also exhibited favorable oral bioavailability, stronger pharmacodynamic effects relative to the PKMYT1 inhibitor alone, and robust antitumor response as a monotherapy in xenograft models. This first-in-class PROTAC serves as a precise chemical probe to explore PKMYT1 biology and a promising lead for further cancer therapy exploration.
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2024-10-06 | GSE253810 | GEO
Project description:How cancer cells escape immune surveillance and resist immunotherapies remain to be elucidated. By screening candidate genes frequently amplified in cancer, we identified expression of ubiquitin-activating enzyme (UBA1) as being the most negatively correlated with signatures related to effector CD8+T cells. High expression of UBA1was strongly predictive of resistance to immune checkpoint blockade (ICB) and poor survival in ICB cohorts. In immunocompetent syngeneic models, but not in immunodeficient models, we found that overexpression ofUba1in cancer cells promoted tumor growth and reduced functional, intratumoral CD8+T cells. Conversely, depletion ofUba1impaired tumor progression, accompanied with increase of functional, intratumoral CD8+T cells. CD8+T cell depletion rescued tumor growth impairment mediated byUba1depletion. Additionally, a selective, small molecule inhibitor of UBA1, TAK-243, delayed tumor growth and augmented ICB in various syngeneic models, in a manner dependent on CD8+T cells. Intratumoral administration of TAK-243 and tumor rechallenge experiments revealed that TAK-243 treatment exhibited a remarkable abscopal effect and provided prolonged protection against cancer, accompanied with elevation of memory CD8+ T cells. Mechanistically, depletion or inactivation of UBA1 stabilized the short-lived interferon (IFN) pathway component, JAK1, upregulated both type-I and -II IFN signaling pathways, and resulted in elevation of key immune modulators, including CXCL9, CXCL10, and MHC-I. Taken together, our data supports that UBA1 mediates cancer immune escape via suppressing interferon signaling and suggests that targeting UBA1 may activate systemic cancer immunity.
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