The recent discovery of mutations in metabolic enzymes has rekindled interest in harnessing the altered metabolism of cancer cells for cancer therapy. One potential drug target is isocitrate dehydrogenase 1 (IDH1), which is mutated in multiple human cancers. Here, we examine the role of mutant IDH1 in fully transformed cells with endogenous IDH1 mutations. A selective R132H-IDH1 inhibitor (AGI-5198) identified through a high-throughput screen blocked, in a dose-dependent manner, the ability of the mutant enzyme (mIDH1) to produce R-2-hydroxyglutarate (R-2HG). Under conditions of near-complete R-2HG inhibition, the mIDH1 inhibitor induced demethylation of histone H3K9me3 and expression of genes associated with gliogenic differentiation. Blockade of mIDH1 impaired the growth of IDH1-mutant—but not IDH1–wild-type—glioma cells without appreciable changes in genome-wide DNA methylation. These data suggest that mIDH1 may promote glioma growth through mechanisms beyond its well-characterized epigenetic effects.
Although previous studies indicate that loss of p53-mediated cell cycle arrest, apoptosis, and senescence, does not completely abrogate its tumor suppression function, it is unclear how the remaining activities of p53 are regulated. Here we identified an acetylation site at lysine K98 in mouse p53 (or K101 for human p53). While the loss of K98 acetylation (p53K98R) alone has very modest effects on p53-mediated transactivation, simultaneous mutations at all four acetylation sites (p534KR: K98R+3KR(K117R+K161R+K162R)) completely abolish its ability to regulate metabolic targets such as TIGAR and SLC7A11. Notably, in contrast to p533KR, p534KR is severely defective in suppressing tumor growth in mouse xenograft models. Moreover, p534KR is still capable of inducing the p53-Mdm2 feedback loop but p53-dependent ferroptotic responses are markedly abrogated. Together, these data indicate the critical role of p53 acetylation in ferroptotic responses and its remaining tumor suppression activity.
Small molecules that can selectively target cancer stem cells (CSCs) remain rare currently and exhibit no common structural features. Here we report a series of guaianolide sesquiterpene lactones (GSLs) and their derivatives that can selectively eradicate acute myelogenous leukemia (AML) stem or progenitor cells. Natural GSL compounds arglabin, an anticancer clinical drug, and micheliolide (MCL), are able to reduce the proportion of AML stem cells (CD34⁺CD38⁻) in primary AML cells. Targeting of AML stem cells is further confirmed by a sharp reduction of colony-forming units of primary AML cells upon MCL treatment. Moreover, DMAMCL, the dimethylamino Michael adduct of MCL, slowly releases MCL in plasma and in vivo and demonstrates remarkable therapeutic efficacy in the nonobese diabetic/severe combined immunodeficiency AML models. These findings indicate that GSL is an ample source for chemical agents against AML stem or progenitor cells and that GSL is potentially highly useful to explore anti-CSC approaches.
Ten types of post-translational modifications (PTMs) known to be critical to diverse cellular functions have been described in core histone proteins. However, it remains unclear whether additional PTMs exist in histones, and if so, what roles these undiscovered signals play in epigenetic phenomena. Here, we report a systematic analysis of yeast histone PTMs by mass spectrometry in combination with protein sequence alignment using PTMap, a computer program we recently developed. We have identified, for the first time, multiple sites of lysine propionylation and butyrylation in yeast histones H2B, H3, and H4. We confirmed these modifications by Western blotting using modification-specific antibodies, MS/MS of synthetic peptides, and coelution of synthetic and in vivo-derived peptides from an HPLC column. The presence of multiple modification sites in several yeast histones suggests that these two PTMs are histone marks that are evolutionarily conserved among eukaryotes. In addition, we identified 14 novel mass shifts that do not match any known PTM, suggesting the presence of previously undescribed histone modifications. The chemical natures of these modifications remain to be determined. Our studies therefore expand current knowledge of the “histone code”.
Purpose:To construct an immune-related gene prognostic index (IRGPI) for head and neck squamous cell carcinoma (HNSCC) and clarify the molecular and immune characteristics and the benefit of immune checkpoint inhibitor (ICI) therapy in IRGPI-defined subgroups of HNSCC.Experimental Design:On the basis of The Cancer Genome Atlas HNSCC immune dataset (n = 546), 22 immune-related hub genes were identified by weighted gene coexpression network analysis. Three genes were identified to construct an IRGPI by using the Cox regression method and validated with the Gene Expression Omnibus (GEO) dataset (n = 270). Afterward, the molecular and immune characteristics and the benefit of ICI therapy in IRGPI-defined subgroups were analyzed.Results:The IRGPI was constructed on the basis of SFRP4, CPXM1, and COL5A1 genes. IRGPI-high patients had a better overall survival than IRGPI-low patients, consistent with the results in the GEO cohort. The comprehensive results showed that a high IRGPI score was correlated with DNA repair–related pathways; low TP53 mutation rate; high infiltration of CD8 T cells, CD4 T cells, and M1 macrophages; active immunity and less aggressive phenotypes; and more benefit from ICI therapy. In contrast, a low IRGPI score was associated with cancer and metastasis-related pathways; high TP53 and PIK3CA mutation rate; high infiltration of B cells, M0 macrophages, and M2 macrophages; suppressive immunity and more aggressive phenotypes; and less benefit from ICI therapy.Conclusions:IRGPI is a promising biomarker to distinguish the prognosis, the molecular and immune characteristics, and the immune benefit from ICI therapy in HNSCC.
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