Identification of DDX60 as a Regulator of MHC-I Class Molecules in Colorectal Cancer

Strategies to overcome low MHC-I expression in paediatric and adult tumours

Immunotherapy has made significant advancements in cancer treatments, improving patients' survival rates and quality of life. Several challenges still need to be addressed, which include the considerable fraction of incomplete curative responses in cancer patients, the development of therapy resistance by tumours, and the occurrence of adverse effects, such as inflammatory and autoimmune complications. Paediatric tumours usually exhibit lower responsiveness to immunotherapies compared to adult tumours. Although the underlying reasons are not yet fully understood, one known mechanism by which tumours avoid immune recognition is through reduced cell surface expression of major histocompatibility complex class I (MHC-I) complexes. Accordingly, the reduced presentation of neoantigens by MHC-I hinders the recognition and targeting of tumour cells by CD8+ T cells, impeding T-cell-mediated cytotoxic anti-tumour responses. MHC-I downregulation indeed often correlates with a poorer prognosis and diminished response to immunotherapy. Understanding the mechanisms underlying MHC-I downregulation in different types of paediatric and adult tumours is crucial for developing strategies to restore MHC-I expression and enhance anti-tumour immune responses. We here discuss progress in MHC-I-based immunotherapies against cancers.

Immunoprecipitation of RNA-DNA hybrid interacting proteins in Trypanosoma brucei reveals conserved and novel activities, including in the control of surface antigen expression needed for immune evasion by antigenic variation

RNA-DNA hybrids are epigenetic features of genomes that provide a diverse and growing range of activities. Understanding of these functions has been informed by characterising the proteins that interact with the hybrids, but all such analyses have so far focused on mammals, meaning it is unclear if a similar spectrum of RNA-DNA hybrid interactors is found in other eukaryotes. The African trypanosome is a single-cell eukaryotic parasite of the Discoba grouping and displays substantial divergence in several aspects of core biology from its mammalian host. Here, we show that DNA-RNA hybrid immunoprecipitation coupled with mass spectrometry recovers 602 putative interactors in T. brucei mammal- and insect-infective cells, some providing activities also found in mammals and some lineage-specific. We demonstrate that loss of three factors, two putative helicases and a RAD51 paralogue, alters T. brucei nuclear RNA-DNA hybrid and DNA damage levels. Moreover, loss of each factor affects the operation of the parasite immune survival mechanism of antigenic variation. Thus, our work reveals the broad range of activities contributed by RNA-DNA hybrids to T. brucei biology, including new functions in host immune evasion as well as activities likely fundamental to eukaryotic genome function.

Role and therapeutic potential of DEAD-box RNA helicase family in colorectal cancer

Colorectal cancer (CRC) is the third most commonly diagnosed and the second cancer-related death worldwide, leading to more than 0.9 million deaths every year. Unfortunately, this disease is changing rapidly to a younger age, and in a more advanced stage when diagnosed. The DEAD-box RNA helicase proteins are the largest family of RNA helicases so far. They regulate almost every aspect of RNA physiological processes, including RNA transcription, editing, splicing and transport. Aberrant expression and critical roles of the DEAD-box RNA helicase proteins have been found in CRC. In this review, we first summarize the protein structure, cellular distribution, and diverse biological functions of DEAD-box RNA helicases. Then, we discuss the distinct roles of DEAD-box RNA helicase family in CRC and describe the cellular mechanism of actions based on recent studies, with an aim to provide future strategies for the treatment of CRC.

The DEAD-box RNA helicase, DDX60, Suppresses immunotherapy and promotes malignant progression of pancreatic cancer

Excessive proliferation, invasion, metastasis, and immune resistance in pancreatic cancer (PC) makes it one of the most lethal malignant tumors. Recently, DDX60 was found to be involved in the development of various tumors and in immunotherapy. Therefore, we aimed to investigate whether DDX60 is a new factor involved in PC immunotherapy. The DDX60 mRNA was screened using transcriptome sequencing (RNA-seq). The Cox and survival analysis of DDX60 was performed using the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) databases. In addition, clinical and immune infiltration data in the databases were analyzed and plotted using the R language. Clinical samples and in vitro experiments were used to determine the molecular evolution of DDX60 during PC progression. We found that DDX60 was upregulated in PC tissues (P value = 0.0083) and was associated with poor prognosis and short survival time of patients with PC. Results of Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, and gene set variation analyses showed that viral defense, tumor, and immune-related pathways were significantly enriched in samples with high DDX60 expression. The Pearson correlation test demonstrated that DDX60 expression correlated strongly with immune checkpoint and immune system-related metagene clusters. Our results indicated that DDX60 promoted cell proliferation, migration, and invasion and was related to poor prognosis and immune resistance. Therefore, DDX60 may be a promising novel target for PC immunotherapy.