H3K9 Trimethylation Silences Fas Expression To Confer Colon Carcinoma Immune Escape and 5-Fluorouracil Chemoresistance

Abstract

The Fas-FasL effector mechanism plays a key role in cancer immune surveillance by host T cells, but metastatic human colon carcinoma often uses silencing Fas expression as a mechanism of immune evasion. The molecular mechanism under FAS transcriptional silencing in human colon carcinoma is unknown. We performed genome-wide ChIP-Sequencing analysis and identified that the FAS promoter is enriched with H3K9me3 in metastatic human colon carcinoma cells. H3K9me3 level in the FAS promoter region is significantly higher in metastatic than in primary cancer cells, and is inversely correlated with Fas expression level. We discovered that verticillin A is a selective inhibitor of histone methyltransferases SUV39H1, SUV39H2 and G9a/GLP that exhibit redundant functions in H3K9 trimethylation and FAS transcriptional silencing. Genome-wide gene expression analysis identified FAS as one of the verticillin A target genes. Verticillin A treatment decreased H3K9me3 level in the FAS promoter and restored Fas expression. Furthermore, verticillin A exhibited greater efficacy than Decitabine and Vorinostat in overcoming colon carcinoma resistance to FasL-induced apoptosis. Verticillin A also increased DR5 expression and overcame colon carcinoma resistance to DR5 agonist drozitumab-induced apoptosis. Interestingly, verticillin A overcame metastatic colon carcinoma resistance to 5-Fluouracil in vitro and in vivo. Using an orthotopic colon cancer mouse model, we demonstrated that tumor-infiltrating cytotoxic T lymphocytes are FasL+ and FasL-mediated cancer immune surveillance is essential for colon carcinoma growth control in vivo. Our findings determine that H3K9me3 of the FAS promoter is a dominant mechanism underlying FAS silencing and resultant colon carcinoma immune evasion and progression.

Discovery of Anticancer Agents of Diverse Natural Origin

“…In addition, screening has begun for compounds that regulate ferroptosis, an emerging form of regulated, non-apoptotic cell death (62). Several of the bioactive compounds obtained in our program project have been followed up recently in more specialized oncology-related in vitro and in vivo bioassays performed by colleagues at the OSU Comprehensive Cancer Center, Nationwide Children's Hospital, Columbus, (OH, USA), and Georgia Regents University (Augusta, GA, USA) (63–65). …”

Media studies to enhance the production of verticillins facilitated by in situ chemical analysis

“…Of these, verticillins are one of the most interesting for a variety of reasons [20, 48, 49, 58, 79]. This class of bioactive fungal secondary metabolites (as exemplified by compounds 1–7 ) is characterized by a dimeric structure [24] and is a key member of the epipolythiodioxopiperazine (ETP) alkaloids.…”

“…The HMT inhibitory activity resulted in the demethylation of H3K9me3 of the silenced FAS gene [58], thereby allowing its transcription, such that FAS was re- expressed, triggering apoptosis mediated cell death [45]. Moreover, verticillin A ( 1 ) induced apoptosis selectively against malignant tumor cells, while minimal effect was exhibited against healthy cells [79].…”

The Janus Face of Death Receptor Signaling during Tumor Immunoediting

“…The examples of reduced TRAIL receptor include loss of DR4 expression in lung squamous cell carcinoma (86) and reduced DR4 and DR5 expression in hepatocellular carcinoma (HCC), which correlated with shorter overall 5-year survival of patients (87). Reduced FAS, DR4, and DR5 expression is typically caused by gene and/or promoter CpG methylation or trimethylation of histone 3 on lysine 9 (H3K9me3), while gene deletion was rarely detected (83, 86, 88). Activating RAS mutations have also been associated with silencing of the FAS gene by driving methylation of the FAS promoter region (89).…”