PWWP2B promotes DNA end resection and homologous recombination

PWWP2A/B: Prominent players in the proteomic landscape

The PWWP domain is a conserved motif unique to eukaryotes, playing a critical role in various cellular processes. Proteins containing the PWWP domain are typically found in chromatin, where they bind to DNA and histones in nucleosomes, facilitating chromatin-associated functions. Among these proteins, PWWP-domain containing proteins 2A and 2B (PWWP2A and PWWP2B), identified during the H2A interactome analysis, are DNA methyltransferase-related proteins, that are structurally disordered, except for their PWWP domain. While their precise functions remain to be fully elucidated, PWWP2A and PWWP2B have been implicated in essential processes such as embryonic development, mitotic regulation, adipose thermogenesis, transcriptional control, and DNA damage response. Their involvement in disease pathology is an emerging area of research, with PWWP2B downregulation linked to recurrent gastric cancer, promoting cell proliferation and migration. Literature reveals that the circular RNA, cPWWP2A sequesters miR-203, miR-223, and miR-27, to modulate TGF-β signalling by inhibiting key regulators like SMAD3 and SP3. Additionally, PWWP2A/B proteins may interact with P4HA3, a regulator of the TGF-β/SMAD signalling pathway that influences tumour invasiveness, though the precise nature of this interaction is not yet fully understood. The PWWP2-miRNA-TGF-β axis, particularly the PWWP2-P4HA3 association, provides valuable insights into therapeutic strategies, especially under adverse conditions where this pathway is differentially regulated. Overall, given their essential roles in fundamental cellular processes and their involvement in disease mechanisms, PWWP2A and PWWP2B proteins could be ideal targets for therapeutic intervention. Thus, these proteins occupy a prominent position in the human proteome and epigenetic landscape.

Advancements and Obstacles of PARP Inhibitors in Gastric Cancer

Gastric cancer (GC) is a common and aggressive cancer of the digestive system, exhibiting high aggressiveness and significant heterogeneity. Despite advancements in improving survival rates over the past few decades, GC continues to carry a worrisome prognosis and notable mortality. As a result, there is an urgent need for novel therapeutic approaches to address GC. Recent targeted sequencing studies have revealed frequent mutations in DNA damage repair (DDR) pathway genes in many GC patients. These mutations lead to an increased reliance on poly (adenosine diphosphate-ribose) polymerase (PARP) for DNA repair, making PARP inhibitors (PARPi) a promising treatment option for GC. This article presents a comprehensive overview of the rationale and development of PARPi, highlighting its progress and challenges in both preclinical and clinical research for treating GC.

SAMHD1 silencing cooperates with radiotherapy to enhance anti-tumor immunity through IFI16-STING pathway in lung adenocarcinoma

BACKGROUND

Sterile alpha motif domain and histidine-aspartate domain-containing protein 1 (SAMHD1) is a DNA end resection factor, which is involved in DNA damage repair and innate immunity. However, the role of SAMHD1 in anti-tumor immunity is still unknown. This study investigated the effects of SAMHD1 on stimulator of interferon genes (STING)-type I interferon (IFN) pathway and radiation-induced immune responses.

METHODS

The roles of SAMHD1 in the activation of cytosolic DNA sensing STING pathway in lung adenocarcinoma (LUAD) cells were investigated with flow cytometry, immunofluorescence, immunoblotting and qPCR. The combined effects of SAMHD1 silencing and radiation on tumor cell growth and STING pathway activation were also evaluated with colony formation and CCK8 assay. The Lewis lung cancer mouse model was used to evaluate the combined efficiency of SAMHD1 silencing and radiotherapy in vivo. Macrophage M1 polarization and cytotoxic T cell infiltration were evaluated with flow cytometry.

RESULTS

The single-stranded DNA (ssDNA) accumulated in the cytosol of SAMHD1-deficient lung adenocarcinoma (LUAD) cells, accompanied by upregulated DNA sensor IFN-γ-inducible protein 16 (IFI16) and activated STING pathway. The translocation of IFI16 from nucleus to cytosol was detected in SAMHD1-deficient cells. IFI16 and STING were acquired in the activation of STING-IFN-I pathway in SAMHD1-deficient cells. SAMHD1 silencing in LUAD cells promoted macrophage M1 polarization in vitro. SAMHD1 silencing synergized with radiation to activate ssDNA-STING-IFN-I pathway, inhibit proliferation, promote apoptosis and regulate cell cycle. SAMHD1 silencing cooperated with radiotherapy to inhibit tumor growth and increase CD86⁺MHC-II^high M1 proportion and CD8⁺ T cell infiltration in vivo.

CONCLUSIONS

SAMHD1 deficiency induced IFN-I production through cytosolic IFI16-STING pathway in LUAD cells. Moreover, SAMHD1 downregulation and radiation cooperated to inhibit tumor growth and enhance anti-tumor immune responses through macrophage M1 polarization and CD8⁺ T cell infiltration. Combination of SAMHD1 inhibition and radiotherapy may be a potentially therapeutic strategy for LUAD patients.