Lysine butyrylation of HSP90 regulated by KAT8 and HDAC11 confers chemoresistance.

Posttranslational modification dramatically enhances protein complexity, but the function and precise mechanism of novel lysine acylation modifications remain unknown. Chemoresistance remains a daunting challenge to successful treatment. We found that lysine butyrylation (Kbu) is specifically upregulated in chemoresistant tumor cells and tissues. By integrating butyrylome profiling and gain/loss-of-function experiments, lysine 754 in HSP90 (HSP90 K754) was identified as a substrate for Kbu. Kbu modification leads to overexpression of HSP90 in esophageal squamous cell carcinoma (ESCC) and its further increase in relapse samples. Upregulation of HSP90 contributes to 5-FU resistance and can predict poor prognosis in cancer patients. Mechanistically, HSP90 K754 is regulated by the cooperation of KAT8 and HDAC11 as the writer and eraser, respectively; SDCBP increases the Kbu level and stability of HSP90 by binding competitively to HDAC11. Furthermore, SDCBP blockade with the lead compound V020-9974 can target HSP90 K754 to overcome 5-FU resistance, constituting a potential therapeutic strategy.

Lysine 2-hydroxyisobutyrylation of NAT10 promotes cancer metastasis in an ac4C-dependent manner.

Posttranslational modifications add tremendous complexity to proteomes; however, gaps remain in knowledge regarding the function and regulatory mechanism of newly discovered lysine acylation modifications. Here, we compared a panel of non-histone lysine acylation patterns in metastasis models and clinical samples, and focused on 2-hydroxyisobutyrylation (Khib) due to its significant upregulation in cancer metastases. By the integration of systemic Khib proteome profiling in 20 paired primary esophageal tumor and metastatic tumor tissues with CRISPR/Cas9 functional screening, we identified N-acetyltransferase 10 (NAT10) as a substrate for Khib modification. We further showed that Khib modification at lysine 823 in NAT10 functionally contribute to metastasis. Mechanistically, NAT10 Khib modification enhances its interaction with deubiquitinase USP39, resulting in increased NAT10 protein stability. NAT10 in turn promotes metastasis by increasing NOTCH3 mRNA stability in an N4-acetylcytidine-dependent manner. Furthermore, we discovered a lead compound #7586-3507 that inhibited NAT10 Khib modification and showed efficacy in tumor models in vivo at a low concentration. Together, our findings bridge newly identified lysine acylation modifications with RNA modifications, thus providing novel insights into epigenetic regulation in human cancer. We propose that pharmacological inhibition of NAT10 K823 Khib modification constitutes a potential anti-metastasis strategy.

ANO1 Reprograms Cholesterol Metabolism and the Tumor Microenvironment to Promote Cancer Metastasis.

SIGNIFICANCE: Metastatic cancer cells upregulate ANO1 to activate cell-intrinsic and -extrinsic mechanisms that alter cholesterol metabolism and stimulate fibroblasts, which can be targeted with ANO1 inhibitors to inhibit metastatic growth. See related commentary by Singh and Mehla, p. 1759.

Blockade of NMT1 enzymatic activity inhibits N-myristoylation of VILIP3 protein and suppresses liver cancer progression.

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors. Identification of the underlying mechanism of HCC progression and exploration of new therapeutic drugs are urgently needed. Here, a compound library consisting of 419 FDA-approved drugs was taken to screen potential anticancer drugs. A series of functional assays showed that desloratadine, an antiallergic drug, can repress proliferation in HCC cell lines, cell-derived xenograft (CDX), patient-derived organoid (PDO) and patient-derived xenograft (PDX) models. N-myristoyl transferase 1 (NMT1) was identified as a target protein of desloratadine by drug affinity responsive target stability (DARTS) and surface plasmon resonance (SPR) assays. Upregulation of NMT1 expression enhanced but NMT1 knockdown suppressed tumor growth in vitro and in vivo. Metabolic labeling and mass spectrometry analyses revealed that Visinin-like protein 3 (VILIP3) was a new substrate of NMT1 in protein N-myristoylation modification, and high NMT1 or VILIP3 expression was associated with advanced stages and poor survival in HCC. Mechanistically, desloratadine binds to Asn-246 in NMT1 and inhibits its enzymatic activity, disrupting the NMT1-mediated myristoylation of the VILIP3 protein and subsequent NFκB/Bcl-2 signaling. Conclusively, this study demonstrates that desloratadine may be a novel anticancer drug and that NMT1-mediated myristoylation contributes to HCC progression and is a potential biomarker and therapeutic target in HCC.

Blockade of Nuclear ß-Catenin Signaling via Direct Targeting of RanBP3 with NU2058 Induces Cell Senescence to Suppress Colorectal Tumorigenesis.

Colorectal cancer (CRC) is one of the most common malignant tumors in the world, with high prevalence and low 5-year survival. Most of the CRC patients show excessive activation of the Wnt/ß-catenin pathway which is a vital target for CRC treatment. Based on multiple CRC cell lines with different nuclear expression of ß-catenin, NU2058 is identified from a small molecule library consisting of 280 bioactive compounds and found to selectively inhibit the proliferation of CRC cells with nuclear ß-catenin activation in vitro and in vivo. The translational significance of NU2058 alone or in combination with chemotherapeutic drugs oxaliplatin and irinotecan (SN38) in CRC is demonstrated in orthotopic tumor model and patient-derived xenograft models. By integrating limited proteolysis-small molecule mapping (LiP-SMap) and mass spectrometry (MS), Ran-binding protein 3 (RanBP3) is identified as the direct target of NU2058. The results show that RanBP3 is a tumor suppressor in CRC and is associated with patient survival. Mechanistically, NU2058 increases the interaction of RanBP3 and ß-catenin to promote nuclear export of ß-catenin, which further inhibits transcription of c-Myc and cyclin D1 to induce cell senescence. Collectively, NU2058 may serve as a promising therapeutic agent for CRC patients with selective disruption of pathologic Wnt/ß-catenin signaling.

Anti-HIV Drug Elvitegravir Suppresses Cancer Metastasis via Increased Proteasomal Degradation of m6A Methyltransferase METTL3.

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 the regulation of METTL3 expression found that KAT2A increased H3K27 acetylation levels in the METTL3 promoter region and activated transcription of METTL3, whereas SIRT2 exerted the opposite effects. Molecular docking and computational screening in a Food and Drug Administration-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. SIGNIFICANCE: This study finds that METTL3 promotes cancer metastasis by activating EGR1/Snail signaling in an m6A-dependent manner, revealing vulnerability to METTL3 blockade in esophageal squamous cell carcinoma.

Targeting PI3K/Akt signal transduction for cancer therapy.

The phosphatidylinositol 3-kinase (PI3K)/Akt pathway plays a crucial role in various cellular processes and is aberrantly activated in cancers, contributing to the occurrence and progression of tumors. Examining the upstream and downstream nodes of this pathway could allow full elucidation of its function. Based on accumulating evidence, strategies targeting major components of the pathway might provide new insights for cancer drug discovery. Researchers have explored the use of some inhibitors targeting this pathway to block survival pathways. However, because oncogenic PI3K pathway activation occurs through various mechanisms, the clinical efficacies of these inhibitors are limited. Moreover, pathway activation is accompanied by the development of therapeutic resistance. Therefore, strategies involving pathway inhibitors and other cancer treatments in combination might solve the therapeutic dilemma. In this review, we discuss the roles of the PI3K/Akt pathway in various cancer phenotypes, review the current statuses of different PI3K/Akt inhibitors, and introduce combination therapies consisting of signaling inhibitors and conventional cancer therapies. The information presented herein suggests that cascading inhibitors of the PI3K/Akt signaling pathway, either alone or in combination with other therapies, are the most effective treatment strategy for cancer.