The ATM-E6AP-MASTL axis mediates DNA damage checkpoint recovery

First-in-class dual inhibitors of MASTL and Aurora A kinase: Discovery of selective cyclohexa[b]thiophenes with potent anticancer activity

The dysregulation of mitotic kinases, particularly Microtubule Associated Serine/Threonine Kinase Like (MASTL) and Aurora A kinase, play pivotal roles in tumor progression and resistance to therapy. Herein, we report cyclohexa[b]thiophenes as first-in-class dual inhibitors of MASTL and Aurora A kinase. The lead compound, MA4, demonstrated potent inhibition of both kinases with IC50 values of 0.16 ± 0.01 μM for Aurora A and 0.56 ± 0.16 μM for MASTL. Kinase selectivity profiling against a panel of 277 kinases revealed a high degree of specificity against both targets. In vitro antiproliferative screening using the NCI-60 human cancer cell line panel revealed broad-spectrum cytotoxicity, with MA4 exhibiting submicromolar GI50 values across multiple malignancies, outperforming previously reported cyclohexa[b]thiophenes in the multidose screening. Mechanistic studies, including microscale thermophoresis (MST) and NanoBRET target engagement assays, confirmed direct binding to both kinases. Computational studies, including molecular docking and molecular dynamics simulations, revealed key interactions stabilizing MA4 within the ATP-binding sites of both kinases. We demonstrated the potent anticancer activity of MA4 in 3D tumor spheroids, along with its favorable pharmacokinetic profile. Additionally, MA4 exhibited no inhibitory activity against hERG and demonstrated selectivity toward cancer cells over normal cell lines, further supporting its potential for in vivo applications. These findings establish cyclohexa[b]thiophenes as promising dual kinase inhibitors with high selectivity, offering a compelling strategy for targeting mitotic dysregulation in cancer therapy.

Expression of MASTL (Greatwall) associates with good prognosis and response to radiotherapy in pharyngeal squamous cell carcinoma

Head and neck squamous cell carcinomas (HNSCCs) are highly heterogeneous in both disease progression and treatment outcome, with hardly any molecular biomarker in clinical practice. Thus, the aim of this study was to investigate the potential prognostic and predictive value of MASTL/Greatwall, a mitotic kinase also involved in PI3K-mTOR signaling and the DNA damage response, in HNSCC. MASTL expression was evaluated by immunohistochemistry in a cohort of 346 surgically treated HPV-negative pharyngeal and laryngeal squamous cell carcinoma patients, as well as in pre-treatment biopsies from a separate cohort of 64 patients treated with induction chemotherapy (ICT). In addition, MASTL mRNA expression was analyzed in 135 patients from The Cancer Genome Atlas (TCGA) database. High MASTL expression was significantly associated with improved disease-specific survival (DSS) (P = 0.029), specifically in well-differentiated pharyngeal squamous cell carcinoma (PSCC) tumors (P = 0.002). Notably, this association was restricted to patients who received adjuvant radiotherapy (RT) (P = 0.009). Consistently, a similar correlation was found at the mRNA level in PSCC tumors from the TCGA dataset. Moreover, the combined expression of MASTL and p21 was significantly associated with better DSS, specifically among patients receiving RT (P = 0.014). Multivariate Cox regression analysis further confirmed that high MASTL expression was independently associated with favorable prognosis in patients who received post-operative RT (HR= 0.65; 95 % CI: 0.45-0.94; P = 0.021). Collectively, these findings unprecedentedly revealed the association between high MASTL expression and favorable outcome in advanced HPV-negative PSCC, in marked contrast to previous reports in other tumor types. Importantly, MASTL expression emerges as an independent predictor of good prognosis in RT-treated PSCC patients.

γ-tubulin mediates DNA double-strand break repair

Double-strand breaks (DSBs) in DNA pose a critical threat to genomic integrity, potentially leading to the onset and progression of various diseases, including cancer. Cellular responses to such lesions entail sophisticated repair mechanisms primarily mediated by non-homologous end joining (NHEJ) and homologous recombination (HR). Interestingly, the efficient recruitment of repair proteins and completion of DSB repair likely involve complex, inter-organelle communication and coordination of cellular components. In this study, we report a role of γ-tubulin in DSB repair. γ-tubulin is a major microtubule nucleation factor governing microtubule dynamics. We show that γ-tubulin is recruited to the site of DNA damage and is required for efficient DSB repair via both NHEJ and HR. Suppression of γ-tubulin impedes DNA repair and exacerbates DNA damage accumulation. Furthermore, γ-tubulin mediates the mobilization and formation of DNA damage foci, which serve as repair centers, thereby facilitating the recruitment of HR and NHEJ repair proteins on damaged chromatin. Finally, pharmacological inhibition of γ-tubulin enhances the cytotoxic effect of DNA-damaging agents, consistent with the DNA repair function of γ-tubulin, and underscoring the potential of its therapeutic intervention in cancer therapy.