Nucleotide metabolism in cancer cells fuels a UDP-driven macrophage cross-talk, promoting immunosuppression and immunotherapy resistance.

Many individuals with cancer are resistant to immunotherapies. Here, we identify the gene encoding the pyrimidine salvage pathway enzyme cytidine deaminase (CDA) among the top upregulated metabolic genes in several immunotherapy-resistant tumors. We show that CDA in cancer cells contributes to the uridine diphosphate (UDP) pool. Extracellular UDP hijacks immunosuppressive tumor-associated macrophages (TAMs) through its receptor P2Y6. Pharmacologic or genetic inhibition of CDA in cancer cells (or P2Y6 in TAMs) disrupts TAM-mediated immunosuppression, promoting cytotoxic T cell entry and susceptibility to anti-programmed cell death protein 1 (anti-PD-1) treatment in resistant pancreatic ductal adenocarcinoma (PDAC) and melanoma models. Conversely, CDA overexpression in CDA-depleted PDACs or anti-PD-1-responsive colorectal tumors or systemic UDP administration (re)establishes resistance. In individuals with PDAC, high CDA levels in cancer cells correlate with increased TAMs, lower cytotoxic T cells and possibly anti-PD-1 resistance. In a pan-cancer single-cell atlas, CDAhigh cancer cells match with T cell cytotoxicity dysfunction and P2RY6high TAMs. Overall, we suggest CDA and P2Y6 as potential targets for cancer immunotherapy.

UBR7 E3 Ligase Suppresses Interferon-ß Mediated Immune Signaling by Targeting Sp110 in Hepatitis B Virus-Induced Hepatocellular Carcinoma.

A newly discovered E3 ubiquitin ligase, UBR7, plays a crucial role in histone H2BK120 monoubiquitination. Here, we report a novel function of UBR7 in promoting hepatitis B virus (HBV) pathogenesis, which further leads to HBV-induced hepatocellular carcinoma (HCC). Transcriptomics analysis from HCC patients revealed the deregulation of UBR7 in cancer. Remarkably, targeting UBR7, particularly its catalytic function, led to a significant decrease in viral copy numbers. We also identified the speckled family protein Sp110 as an important substrate of UBR7. Notably, Sp110 has been previously shown to be a resident of promyelocytic leukemia nuclear bodies (PML-NBs), where it remains SUMOylated, and during HBV infection, it undergoes deSUMOylation and exits the PML body. We observed that UBR7 ubiquitinates Sp110 at critical residues within its SAND domain. Sp110 ubiquitination downregulates genes in the type I interferon response pathway. Comparative analysis of RNA-Seq from the UBR7/Sp110 knockdown data set confirmed that the IFN-ß signaling pathway gets deregulated in HCC cells in the presence of HBV. Single-cell RNA-Seq analysis of patient samples further confirmed the inverse correlation between the expression of Sp110/UBR7 and the inflammation score. Notably, silencing of UBR7 induces IRF7 phosphorylation, thereby augmenting interferon (IFN)-ß and the downstream interferon-stimulated genes (ISGs). Further, wild-type but not the ubiquitination-defective mutant of Sp110 could be recruited to the type I interferon response pathway genes. Our study establishes a new function of UBR7 in non-histone protein ubiquitination, promoting viral persistence, and has important implications for the development of therapeutic strategies targeting HBV-induced HCC.

Targeting the bicarbonate transporter SLC4A4 overcomes immunosuppression and immunotherapy resistance in pancreatic cancer.

Solid tumors are generally characterized by an acidic tumor microenvironment (TME) that favors cancer progression, therapy resistance and immune evasion. By single-cell RNA-sequencing analysis in individuals with pancreatic ductal adenocarcinoma (PDAC), we reveal solute carrier family 4 member 4 (SLC4A4) as the most abundant bicarbonate transporter, predominantly expressed by epithelial ductal cells. Functionally, SLC4A4 inhibition in PDAC cancer cells mitigates the acidosis of the TME due to bicarbonate accumulation in the extracellular space and a decrease in lactate production by cancer cells as the result of reduced glycolysis. In PDAC-bearing mice, genetic or pharmacological SLC4A4 targeting improves T cell-mediated immune response and breaches macrophage-mediated immunosuppression, thus inhibiting tumor growth and metastases. In addition, Slc4a4 targeting in combination with immune checkpoint blockade is able to overcome immunotherapy resistance and prolong survival. Overall, our data propose SLC4A4 as a therapeutic target to unleash an antitumor immune response in PDAC.

Roles of Figla/figla in Juvenile Ovary Development and Follicle Formation During Zebrafish Gonadogenesis.

Sex determination and differentiation are complex processes. As a juvenile hermaphrodite or undifferentiated gonochorist, zebrafish undergo a special juvenile ovarian phase during sex differentiation, making it an excellent model for studying early oogenesis and folliculogenesis. We provide lines of evidence at morphological, molecular, and genetic levels for roles of factor in the germline α (Figla), an oocyte-specific transcription factor, in early zebrafish gonadogenesis. As in mammals, Figla/figla was also expressed in the gonads and its expression in the ovary was also restricted to early oocytes. Disruption of figla gene by CRISPR/Cas9 led to an all-male phenotype in the mutant. Detailed analysis of early gonadal development showed that the germ cells in the mutant were clustered in cysts and underwent meiosis, forming oocytes at prefollicular chromatin nucleolar (CN) stage (stage IA). However, the subsequent transition from cystic CN oocytes to individual follicular perinucleolar oocytes (stage IB) was blocked, resulting in an all-male phenotype in the mutant. The phenotype of figla mutant could not be rescued by estrogen treatment, in contrast to cyp19a1a mutant, and introduction of tp53 mutation also had no effect, unlike in fancd1 and fancl mutants. Transcriptome analysis revealed that many biological processes and pathways related to germ cell development, especially oogenesis, were upregulated in the presence of Figla and that the regulation of figla expression may involve heat shock proteins. Our results strongly suggest important roles for Figla in juvenile ovary development, especially the formation of individual follicles from cystic oocytes.