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SMYD5 regulates mRNA translation to promote gastric adenocarcinoma (GAC)

ABSTRACT: Dysregulated transcription due to disruption in histone lysine methylation dynamics is an established contributor to tumorigenesis. However, whether analogous pathologic epigenetic mechanisms act directly on the ribosome to advance oncogenesis is unclear. Here we find that trimethylation of the core ribosomal protein L40 at lysine 22 (rpL40K22me3) by the lysine methyltransferase (KMT) SMYD5 regulates mRNA translation output to promote gastric adenocarcinoma (GAC) malignant progression with lethal peritoneal ascites. A biochemical-proteomic strategy identifies the mono-ubiquitin fusion protein partner rpL40 as the principal physiologic substrate of SMYD5 across diverse samples. Inhibiting the SMYD5-rpL40K22me3 axis in GAC cell lines reprograms protein synthesis to attenuate oncogenic gene expression signatures. SMYD5 and rpL40K22me3 are upregulated in GAC patient samples and negatively correlate with clinical outcomes. SMYD5 ablation in vivo in familial and sporadic mouse models of malignant GAC blocks metastatic disease including peritoneal carcinomatosis (PC). Suppressing SMYD5 methylation of rpL40 inhibits human cancer cell and patient-derived GAC xenograft growth and renders them hypersensitive to PI3K/mTOR inhibitors. Finally, combining SMYD5 depletion with PI3K/mTOR inhibition and CAR-T administration cures an otherwise lethal in vivo mouse model of aggressive GAC-derived PC. Together, our work uncovers a ribosome-based epigenetic mechanism that facilitates evolution of malignant GAC and nominates SMYD5 targeting as part of a potential cornerstone combination therapy to treat a deadly cancer.

ORGANISM(S): Homo sapiens

PROVIDER: GSE238257 | GEO | 2024/03/01

REPOSITORIES: GEO

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Project description:Gastric adenocarcinoma (GAC) remains a significant cause of cancer-related deaths worldwide, with the majority of mortality resulting from metastatic spread. To elucidate the evolution of cancer cells and their interactions with the tumour microenvironment (TME), we conducted a comprehensive single-cell transcriptome and immune repertoire profiling of primary tumours (PRIs), matched liver metastases (LMs) or peritoneal carcinomatosis (PC), adjacent normal tissues, and blood samples from 20 treatment-naïve patients. We found that the TME within metastases varied substantially from PRIs and differed between LMs and PC samples. Indicative of immune evasion, we observed diminished T cell clonal expansion, a marked reduction in the fraction of tumour-reactive CD8 T cells, and an enrichment of naïve T cells, M2-like, and proliferative macrophages in PC samples compared to PRIs. LMs displayed significantly reduced B cells, with increased fractions of exhausted CD8 T cells and NK/NKT cells. Both LMs and PC showed nearly depleted plasma cells. Malignant cells largely exhibited diminished gastric lineage identity, predominantly adopting intestinal-like and mixed cell states, with the acquired expression of gastrointestinal stem-cell markers. LM cancer cells showed increased epithelial-to-mesenchymal signalling, while PC cancer cells had increased levels of aneuploidy. We observed differentially expressed cancer meta-programs and gene modules (GMs) between LMs and PC, with high GM2 expression in the PRI predicting an increased risk of distant metastases. Further analysis of GM signature genes revealed ferroptosis evasion through GPX4 upregulation during malignant progression. Functional validation via patient-derived xenografts and a novel autochthonous mouse model of GAC confirmed that genetic or pharmacological inhibition of ferroptosis resistance attenuates tumor growth and metastatic progression. Together, our mapping of malignant progression provides a rationale for targeting ferroptosis defense in combination with next-generation CAR T-cell immunotherapy as a potential avenue to overcome T cell dysfunction in advanced metastatic GAC therapy.

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SMYD5 regulates mRNA translation to promote gastric adenocarcinoma (GAC)

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