Activation of polyamine catabolism promotes glutamine metabolism and creates a targetable vulnerability in lung cancer.

Polyamines are a class of small polycationic alkylamines that play essential roles in both normal and cancer cell growth. Polyamine metabolism is frequently dysregulated and considered a therapeutic target in cancer. However, targeting polyamine metabolism as monotherapy often exhibits limited efficacy, and the underlying mechanisms are incompletely understood. Here we report that activation of polyamine catabolism promotes glutamine metabolism, leading to a targetable vulnerability in lung cancer. Genetic and pharmacological activation of spermidine/spermine N1-acetyltransferase 1 (SAT1), the rate-limiting enzyme of polyamine catabolism, enhances the conversion of glutamine to glutamate and subsequent glutathione (GSH) synthesis. This metabolic rewiring ameliorates oxidative stress to support lung cancer cell proliferation and survival. Simultaneous glutamine limitation and SAT1 activation result in ROS accumulation, growth inhibition, and cell death. Importantly, pharmacological inhibition of either one of glutamine transport, glutaminase, or GSH biosynthesis in combination with activation of polyamine catabolism synergistically suppresses lung cancer cell growth and xenograft tumor formation. Together, this study unveils a previously unappreciated functional interconnection between polyamine catabolism and glutamine metabolism and establishes cotargeting strategies as potential therapeutics in lung cancer.

Mammary epithelial cell-derived exosomal miR-155-inhibitor played a key role in the treatment of mastitis via down-regulation of TLRs/NF-κB signaling pathway to inhibit inflammatory response.

Mastitis is a common disorder in women capable of altering the normal physiological function of the mammary gland. It has been reported that mammary epithelial cells (MECs) could be involved in treating mastitis by regulating the inflammatory response and miR-155 might participate in this process. However, the effects of MECs-derived exosomal miR-155-inhibitor in treating mastitis and the regarding mechanism are still unknown. In our study, mouse mammary epithelial cells (HC11) were applied to study the role of MECs-derived exosomal miR-155-inhibitor in the treatment of mastitis and explore the mechanism. Results in our study showed that specific markers including CD63 and Apo-A1 were expressed in blank exosomes and exosomes containing miR-155-inhibitor isolated from transfected HC11 cells. Results of immunofluorescence showed that the blank exosomes and exosomes (containing miR-155-inhibitor) labeled with PKH26 were absorbed in HC11 cells. The level of miR-155 was decreased obviously in Engineered exosomes with miR-155-inhibitor and HC11 cells Transfected with exosome containing miR-155-inhibitor. The level of miR-155 was increased and cell apoptosis was promoted obviously in HC11 cells induced by LPS, however, they were decreased obviously after transfecting with an exosome containing miR-155-inhibitor. The level of TLR2, TLR4, TLR6, NF-κB, TNF-α, and IL-1ß was increased obviously in LPS-induced HC11 cells, however, they were decreased obviously after transfecting with an exosome containing miR-155-inhibitor. The change in IL-10 level is opposite to the above genes. Taken together, exosomal miR-155-inhibitor could decrease the apoptosis of MECs and inhibit the inflammatory response to treat mastitis by down-regulation in the TLRs/NF-κB signaling pathway, which might be a new therapeutic target for mastitis.

PUF60 promotes cell cycle and lung cancer progression by regulating alternative splicing of CDC25C.

Alternative splicing (AS) has been implicated in cell cycle regulation and cancer, but the underlying mechanisms are poorly understood. The poly(U)-binding splicing factor 60 (PUF60) is essential for embryonic development and is overexpressed in multiple types of cancer. Here, we report that PUF60 promotes mitotic cell cycle and lung cancer progression by controlling AS of the cell division cycle 25C (CDC25C). Systematic analysis of splicing factors deregulated in lung adenocarcinoma (LUAD) identifies that elevated copy number and expression of PUF60 correlate with poor prognosis. PUF60 depletion inhibits LUAD cell-cycle G2/M transition, cell proliferation, and tumor development. Mechanistically, PUF60 knockdown leads to exon skipping enriched in mitotic cell cycle genes, including CDC25C. Exon 3 skipping in the full-length CDC25C results in nonsense-mediated mRNA decay and a decrease of CDC25C protein, thereby inhibiting cell proliferation. This study establishes PUF60 as a cell cycle regulator and an oncogenic splicing factor in lung cancer.

The Ribosome Biogenesis Factor Ltv1 Is Essential for Digestive Organ Development and Definitive Hematopoiesis in Zebrafish.

Ribosome biogenesis is a fundamental activity in cells. Ribosomal dysfunction underlies a category of diseases called ribosomopathies in humans. The symptomatic characteristics of ribosomopathies often include abnormalities in craniofacial skeletons, digestive organs, and hematopoiesis. Consistently, disruptions of ribosome biogenesis in animals are deleterious to embryonic development with hypoplasia of digestive organs and/or impaired hematopoiesis. In this study, ltv1, a gene involved in the small ribosomal subunit assembly, was knocked out in zebrafish by clustered regularly interspaced short palindromic repeats (CRISPRs)/CRISPR associated protein 9 (Cas9) technology. The recessive lethal mutation resulted in disrupted ribosome biogenesis, and ltv1 Δ14/Δ14 embryos displayed hypoplastic craniofacial cartilage, digestive organs, and hematopoiesis. In addition, we showed that the impaired cell proliferation, instead of apoptosis, led to the defects in exocrine pancreas and hematopoietic stem and progenitor cells (HSPCs) in ltv1 Δ14/Δ14 embryos. It was reported that loss of function of genes associated with ribosome biogenesis often caused phenotypes in a P53-dependent manner. In ltv1 Δ14/Δ14 embryos, both P53 protein level and the expression of p53 target genes, Δ113p53 and p21, were upregulated. However, knockdown of p53 failed to rescue the phenotypes in ltv1 Δ14/Δ14 larvae. Taken together, our data demonstrate that LTV1 ribosome biogenesis factor (Ltv1) plays an essential role in digestive organs and hematopoiesis development in zebrafish in a P53-independent manner.