G9a and EZH2 are two histone methyltransferases commonly upregulated in several cancer types, yet the precise roles that these enzymes play cooperatively in cancer is unclear. We demonstrate here that frequent concurrent upregulation of both G9a and EZH2 occurs in several human tumors. These methyltransferases cooperatively repressed molecular pathways responsible for tumor cell death. In genetically distinct tumor subtypes, concomitant inhibition of G9a and EZH2 potently induced tumor cell death, highlighting the existence of tumor cell survival dependency at the epigenetic level. G9a and EZH2 synergistically repressed expression of genes involved in the induction of endoplasmic reticulum (ER) stress and the production of reactive oxygen species. IL24 was essential for the induction of tumor cell death and was identified as a common target of G9a and EZH2. Loss of function of G9a and EZH2 activated the IL24-ER stress axis and increased apoptosis in cancer cells while not affecting normal cells. These results indicate that G9a and EZH2 promotes the evasion of ER stress–mediated apoptosis by repressing IL24 transcription, therefore suggesting that their inhibition may represent a potential therapeutic strategy for solid cancers. Significance: These findings demonstrate a novel role for G9a and EZH2 histone methyltransferases in suppressing apoptosis, which can be targeted with small molecule inhibitors as a potential approach to improve solid cancer treatment.

The tumor suppressor gene p53 plays a critical role in the cellular response to genetic damage caused by radiation. In addition, mutations in this gene are often encountered in cells in lung tumors resected from uranium miners whose exposure to radon daughters exceeded 450 working level months. However, most of these miners also smoked tobacco products. Thus whether this gene is of specific importance in lung cancer is unclear. In this study, aberrations in the p53 gene were investigated using an immunohistochemical assay on 38 lung tumors (26 squamous cell carcinomas, 9 adenocarcinomas and 3 adenosquamous carcinomas) from rats that had inhaled 239PuO2 aerosols. Only 2 tumors exhibited detectable levels of staining of p53 products; both were large, well-differentiated squamous cell carcinomas that had invaded the pleural cavity or mediastinum. Direct DNA sequence analysis was used to characterize the mutations in these two tumors, and both exhibited G-->A transition mutations. One tumor was mutated in the first position of codon 283, resulting in a lysine for glutamine substitution; the other tumor was mutated at the second position of codon 280, resulting in a histidine to arginine substitution. No alterations in exons 5-7 of the p53 gene were found in a representative sample of tumors that did not exhibit elevated levels of the protein by immunohistochemistry. Further, no detectable polymorphisms or deletions were observed within the rat p53 gene after Southern blot analysis of 18 randomly selected 239Pu-induced tumors. These results suggest that p53 mutations are relatively unimportant in the development of lung tumors induced in the rat by high-linear energy transfer radiation.

NK cell licensing is an educational process that enhances responsiveness to activating signals in maturing NK cells and is predominantly regulated by MHC class I–specific inhibitory signals. However, the role of non-MHC signaling in this process remains unclear. In this study, we investigated the role of FcRγ, an adaptor protein associated with activating receptors, in the regulation of NK cell responsiveness. We showed that although FcRγ does not affect NK cell development, maturation, or cytotoxic molecule expression, FcRγ-deficient (Fcer1g−/−) NK cells exhibit hyporesponsiveness to tumor cells and impaired tumor control in vivo. Transcriptional and proteomic analyses revealed significantly reduced expression of CD244 in Fcer1g−/− NK cells, which contributed to their functional maturation and licensing, suggesting an additional, nonredundant pathway of NK cell education. Pretreatment with common γ-chain cytokines (IL2 or IL15) rescued Fcer1g−/− NK cells from hyporesponsiveness and restored their antitumor activity. These findings demonstrate that FcRγ plays a crucial role in licensing NK cells for antitumor immune responses through CD244 signaling and that γ-chain cytokines can override the absence of this signaling.

Immunotherapy represents a groundbreaking approach for treating colorectal cancer (CRC), harnessing the body’s own immune system to target tumour cells more precisely than conventional chemotherapy. Immune checkpoint inhibitors, such as antibodies against PD-1, PD-L1, or CTLA-4, have shown remarkable efficacy in certain patients, leading to durable responses and improved survival. However, the majority of CRC cases have limited benefit from a single agent checkpoint blockade. There is a growing need to identify biomarkers that will improve the selection of patients who will best respond to therapy, as well as new targets to sensitise cancers to an immune checkpoint blockade. Unfortunately, the search for reliable biomarkers has been limited by our incomplete understanding of how immunotherapies modify the already complex immune response to cancer. Revolutionary techniques, such as genome-wide CRISPR/Cas9 screening combined with the appropriate validation systems such as in vivo mouse models and/or 3D organoid co-culture systems, are being used to address this knowledge gap. This review will focus on the use of immunotherapies in CRC, discuss why most CRC patients do not respond, and highlight in vitro, in vivo, and novel techniques for discovery of new targets for combination treatment.

Supplementary Data from Combined Inhibition of G9a and EZH2 Suppresses Tumor Growth via Synergistic Induction of IL24-Mediated Apoptosis

Supplementary Data from Combined Inhibition of G9a and EZH2 Suppresses Tumor Growth via Synergistic Induction of IL24-Mediated Apoptosis