N6-methyladenosine (m6A) methylation is an abundant modification in eukaryotic mRNAs. Accumulating evidence suggests a role for RNA m6A methylation in various aspects of cancer biology. In this study, we aimed to explore the biological role of RNA m6A modification in tumor metastasis and to identify novel therapeutic strategies for esophageal squamous cell carcinoma (ESCC). Integration of genome-wide CRISPR/Cas9 functional screening with highly invasive and metastatic ESCC subline models led to the identification of METTL3, the catalytic subunit of the N6-adenosine-methyltransferase complex, as a promoter of cancer metastasis. METTL3 expression was upregulated in ESCC tumors and metastatic tissues. In vitro and in vivo experiments indicated that METTL3 increased m6A in EGR1 mRNA and enhanced its stability in a YTHDF3-dependent manner, activating EGR1/Snail signaling. Investigation into regulation of METTL3 expression found that KAT2A increased H3K27 acetylation levels in the METTL3 promoter region and activated transcription of METTL3 while SIRT2 exerted the opposite effects. Molecular docking and computational screening in a Food and Drug Administration (FDA)-approved compound library consisting of 1,443 small molecules identified compounds targeting METTL3 to suppress cancer metastasis. Elvitegravir, originally developed to treat human immunodeficiency virus (HIV) infection, suppressed metastasis by directly targeting METTL3 and enhancing its STUB1-mediated proteasomal degradation. Overall, RNA m6A modifications are important in cancer metastasis, and targeting METTL3 with elvitegravir has therapeutic potential for treating ESCC.

Dephosphorylation of transcription factor EB (TFEB) at Ser142 and Ser138 determines its nuclear localization and transcriptional activity. The link between TFEB-associated genes and colorectal cancer (CRC) progression and prognosis remains unclear. To systematically identify the targets of TFEB, we performed data-independent acquisition (DIA)-based quantitative proteomics to compare global protein changes in wild-type (WT) DLD1 cells and TFEBWT- or TFEBS142A/S138A (activated status)-expressing DLD1 cells. A total of 6048 proteins were identified and quantified in three independent experiments. The differentially expressed proteins in TFEBS142A/S138A versus TFEBWT and TFEBWT versus control groups were compared, and 60 proteins were identified as products of TFEB transcriptional regulation. These proteins were significantly associated with vesicular endocytic trafficking, the HIF-1 signaling pathway, and metabolic processes. Furthermore, we generated a TFEB-associated gene signature using a univariate and LASSO Cox regression model to screen robust prognostic markers. An eight-gene signature (PLSCR3, SERPINA1, ATP6V1C2, TIMP1, SORT1, MAP2, KDM4B, and DDAH2) was identified. According to the signature, patients were assigned to high-risk and low-risk groups. Higher risk scores meant worse overall survival and higher epithelial–mesenchymal transition (EMT) scores. Additionally, as per the clinicopathological parameters and gene signature, a nomogram was constructed that was utilized to enhance the quantification capacity in risk assessment for individual patients. This research shows that TFEB directly mediates network effects in CRC, and the identified TFEB gene signature-based model may provide important information for the clinical judgment of prognosis.

Dear Editor,Epidermal growth factor receptor (EGFR)-mediated mitogen-activated protein kinase/extracellular signalregulated kinase (MAPK/ERK) signalling is highly activated in colorectal cancer (CRC). 1,2 Small GTPase Ras-related protein Rab-5A (Rab5) is a critical player in transducing this oncogenic signal. 3,4 Rab5 activation has been known to be enhanced by relevant guanine exchange factors (GEFs) 5 ; however, the mechanism by which GEF activates Rab5 is poorly understood. The current work represents our effort in the comprehensive characterisation of a "dark" protein, C20orf24, which works as a Rab5 activator to promote colorectal tumorigenesis through EGFR/MEK/ERK signalling pathway.Human Proteome Organization launched a project named neXt-CP50, aiming to characterise those proteins with completely unknown functions, termed uncharacterised protein existence level 1 (uPE1) proteins. 6 These "dark" proteins are a rich resource for exploring novel tumour-associated proteins. Here, we screened for novel EGFR signalling regulators in CRC from 35 dedicated uPE1 proteins using the The Cancer Genome Atlas (TCGA) data set. C20orf24 was the top-ranked protein upregulated in CRC tissues among the 35 uPEs (Figure 1A). C20orf24 coexists in a fusion gene TGIF2-C20orf24, which constitutively occurs during read-through transcription between the TGIF2 and C20orf24 genes (Figure S1A). We found that the copy numbers of the three genes were markedly upregulated in CRC tissues (Figure S1B), while the expression of C20orf24 was higher than that of TGIF2 or TGIF2-C20orf24 in CRC tissues and cell lines (Figure S1C,D), as confirmed by quantitative real-time polymerase chain reaction (qRT-PCR) in 17 CRC tumours (Figure S1E).