Biology subjects

Marshall, C. G.

Publications and source records attributed to Marshall, C. G..

3 recordsLinked to original sources

bioRxiv2025

PKMYT1 inhibition induces DNA damage and synergizes with immune checkpoint blockade in CCNE1-amplified gastroesophageal adenocarcinoma

PurposeCCNE1 amplification, found in approximately 10% of gastroesophageal adenocarcinoma (GEA), drives chromosomal instability and is associated with an immune-cold tumor microenvironment. Recent studies suggest that PKMYT1 inhibition is synthetic lethal in CCNE1-amplified cancers; however, its role in GEA is largely uncharacterized. We investigated the therapeutic activity of PKMYT1 inhibition in CCNE1-amplified GEA and its potential combination with immunotherapy. Experimental DesignWe evaluated lunresertib (RP-6306), a selective first-in-class PKMYT1 inhibitor, in CCNE1-amplified and wild-type GEA cell lines to define its effects on cell viability, DNA damage, and gene expression changes. To investigate the role of PKMYT1 blockade on immune microenvironment modulation, we used a syngeneic murine model of CCNE1;Trp53-/- GEA xenografts treated with lunresertib, anti-PD-1, or the combination. ResultsLunresertib was selectively cytotoxic in CCNE1-amplified GEA cell lines in cell viability and clonogenic assays. Mechanistically, treatment with lunresertib induced DNA damage, evidence by increased {gamma}H2AX expression and DNA micronuclei formation, and activated pro-inflammatory signaling pathways by gene set enrichment analysis. In a CCNE1-amplified GEA murine model, PKMYT1 inhibition promoted T cell infiltration, reduced myeloid cells, and synergized with anti-PD-1 therapy to induce tumor regression. ConclusionsOur results suggest that CCNE1 amplification is a potentially actionable target in GEA and support the development of combination therapeutic strategies utilizing PKMYT1 inhibition and PD-1 blockade. Translational RelevanceGastroesophageal adenocarcinoma (GEA) is an aggressive malignancy with poor prognosis and few actionable molecular alterations. CCNE1 amplification is present in approximately 10% of patients with GEA and represents a potential therapeutic vulnerability through synthetic lethality with PKMYT1 inhibition. We demonstrate that targeting CCNE1-amplified GEA through PKMYT1 inhibition with lunresertib is selectively cytotoxic, induces DNA damage, and activates inflammatory signaling pathways. In a syngeneic murine model of CCNE1-amplified gastric cancer, we further identified that PKMYT1 inhibition induced T cell infiltration and tumor microenvironment remodeling, and synergized with anti-PD-1 therapy to drive tumor regression. Together, these results support further development of PKMYT1 inhibition in combination with PD-1 blockade for CCNE1-amplified GEA.

cancer biology↗

bioRxiv2025

A dual mechanism of sensitivity to PLK4 inhibition by RP-1664 in neuroblastoma

A novel therapeutic strategy was recently proposed for high-risk neuroblastoma carrying copy number gain of the TRIM37 gene: centriole loss upon inhibition of polo-like kinase 4 (PLK4), while tolerated by normal cells, induces aberrant mitotic spindle formation and p53-dependent cell death in TRIM37-overexpressing cells. Interestingly, while full PLK4 inhibition causes centriole loss, partial inhibition is known to elevate centriole numbers. Here we show using a novel selective PLK4 inhibitor RP-1664 that both centriole loss and amplification contribute to hypersensitivity of neuroblastoma cells. Whereas inactivation of TRIM37 and TP53 rescues neuroblastoma cell death at higher concentrations of RP-1664, at lower doses cell death is TRIM37/TP53-independent. With CRISPR screens and live cell imaging we demonstrate that upon centriole amplification, neuroblastoma cells succumb to multipolar mitoses due to inability to cluster or inactivate supernumerary centrosomes. In vivo, RP-1664 shows robust efficacy in neuroblastoma xenografts at doses consistent with centriole amplification. STATEMENT OF SIGNIFICANCEHigh-risk neuroblastoma is associated with poor outcomes in pediatric patients and novel therapies need to be developed. We show that neuroblastoma cells are remarkably sensitive to PLK4 inhibitors due to a combination of two complementary mechanisms, supporting the evaluation of PLK4 inhibitors in clinical trials of high-risk neuroblastoma.

cancer biology↗

bioRxiv2021

CCNE1 amplification is synthetic-lethal with PKMYT1 kinase inhibition

Amplification of the gene encoding cyclin E (CCNE1) is an oncogenic driver in several malignancies and is associated with chemoresistance and poor prognosis. To uncover therapeutic targets for CCNE1-amplified tumors, we undertook genome-scale CRISPR/Cas9-based synthetic lethality screens in cellular models of CCNE1 amplification. Here, we report that increasing CCNE1 dosage engenders a vulnerability to the inhibition of the PKMYT1 kinase, a negative regulator of CDK1. To inhibit PKMYT1, we developed RP-6306, an orally bioavailable and selective inhibitor that shows single-agent activity and durable tumor regressions when combined with gemcitabine in models of CCNE1-amplification. RP-6306 treatment causes unscheduled activation of CDK1 selectively in CCNE1 overexpressing-cells, promoting early mitosis in cells undergoing DNA synthesis. CCNE1 overexpression disrupts CDK1 homeostasis at least in part through an early activation of the FOXM1/MYBL2/MuvB-dependent mitotic transcriptional program. We conclude that PKMYT1 inhibition is a promising therapeutic strategy for CCNE1-amplified cancers.

cancer biology↗