Walid T. Khaled

The N7-methylguanosine (m ⁷ G) modification is one of the most prevalent tRNA modifications, mainly catalysed by the METTL1–WDR4 protein complex ^1–4 . The m ⁷ G methyltransferase METTL1 has been linked to oncogenic transformation and the maintenance of several aggressive malignancies; however, the clinical implications of therapeutically targeting a tRNA-modifying enzyme have not been established. Here we present the development and characterization of STM9005, a highly selective and potent first-in-class tRNA methyltransferase inhibitor of METTL1. Treatment of numerous cancer cell models (including leukaemia, melanoma, pancreatic carcinoma, oesophageal cancer and small cell lung carcinoma) with STM9005 blocks cell growth, causes differentiation changes and dysregulates cell cycle progression. These cellular effects were accompanied by a selective decrease in m ⁷ G on a subset of tRNAs and a reduction in their expression levels, which impacted the translation of oncogenic mRNAs. We show that pharmacological inhibition of METTL1 in vivo impairs tumour growth and significantly prolongs survival in multiple mouse cancer models of different tissue origin. Collectively, our results provide a strong proof of concept that targeting of tRNA methylation is a promising avenue of anti-cancer therapy and illustrate that catalytic inhibition of METTL1 represents a therapeutic strategy against a number of aggressive malignancies.

N-acetyltransferase 10 (NAT10) is a multifunctional enzyme that harbors RNA acetyltransferase and RNA helicase domains and has emerged as a therapeutic vulnerability in solid and hematological malignancies. By coupling Proteolysis Targeting Chimera-mediated degradation of NAT10 with a deep mutational scanning assay, followed by validations in biochemical assays, human cell lines, and female mouse xenografts, we find that the RNA helicase domain of NAT10 enhances cancer cell proliferation and tumor growth. This proliferative function of NAT10 is independent of RNA acetylation but requires its RNA-binding activity. The RNA helicase domain of NAT10 is required for 18S rRNA binding, promoting biogenesis of the 40S ribosomal subunit, while simultaneously interfering with the deposition of the conserved 18S rRNA modification m¹acp³Ψ. Loss of m¹acp³Ψ in 18S rRNA enhances cancer cell proliferation, revealing that NAT10 promotes the biogenesis of hypomodified ribosomes to facilitate tumor growth. These findings uncover a mechanism by which NAT10 promotes cancer cell proliferation and establish its RNA helicase domain as a potential therapeutic target.

Rank signaling regulates mammary gland development and epithelial differentiation. While Rank is expressed in both basal and luminal cells, its basal-specific role is unclear. Here, using inducible basal-specific Rank expression and lineage tracing, we show that Rank signaling regulates basal cell identity in postnatal mammary glands. Increased basal Rank activity disrupts basal and luminal identities, causing aberrant luminal-like differentiation, lactation defects, and premalignant lesions composed of hybrid basal-derived cells that progress to basal and luminal adenocarcinomas. Conversely, Rank loss reduces tumor formation and also impairs cell identity. Mechanistically, proteomic, transcriptomic, and chromatin analyses reveal that Rank activation drives epigenetic remodeling, leading to basal identity loss and tumor initiation. A basal Rank gene signature correlates with ductal carcinoma in situ recurrence, as well as poor outcomes in luminal breast cancers. Thus, basal Rank-driven lineage infidelity promotes pre-invasive lesions and transition to invasive breast cancer in females.

Antibody validation against NMR proteins

Sequence chromatograms assessing genomic cleavage using the first-generation Tp53 and Rb1 adenovirus.

Schematic of strategy to induce the EML4-ALK inversion

List of BaseScope probes used in study

Shows Co-localization of Eml4-Alk and Sftpc in NMR lung tumors.

Assessment of the effect of Eml4-Alk expression in NMR skin fibroblasts.

There is growing interest in understanding the mechanisms underlying differences in cancer incidence among species (comparative oncology). The naked mole rat (NMR) is often referenced as “cancer resistant” and prior studies focused on identifying mechanisms explaining this. However, efforts to assess this in vivo have been limited. In this study, we provide evidence that the NMR presents as a novel autochthonous model of lung tumor initiation, driven by an introduction of the oncogenic Eml4-Alk fusion gene using CRISPR-mediated genome editing. Although in mice, the inversion alone is sufficient to drive tumorigenesis, the inversion alone was insufficient to drive tumorigenesis in the NMR lung, and tumor development required additional losses of the tumor suppressors p53 and pRb. Our findings suggest that the proposed “resistance” of the NMR to the development of cancer may reflect that the genetic events leading to tumor initiation are likely to be comparable with those present in human cells.Significance:To identify evolutionary divergent mechanisms of cancer resistance, we assessed tumorigenesis in vivo using the NMR, a species considered to exhibit cancer resistance. Our findings suggest that the proposed “resistance” of NMRs to the development of cancer may reflect tumor initiation mechanisms comparable with the mechanisms present in humans.See related commentary by Boddy and Abegglen, p. 7