Lung cancer is the leading cause of cancer-related death worldwide. Aberrant splicing has been implicated in lung tumorigenesis. However, the functional links between splicing regulation and lung cancer are not well understood. Here we identify the RNA-binding protein QKI as a key regulator of alternative splicing in lung cancer. We show that QKI is frequently down-regulated in lung cancer, and its down-regulation is significantly associated with a poorer prognosis. QKI-5 inhibits the proliferation and transformation of lung cancer cells both in vitro and in vivo. Our results demonstrate that QKI-5 regulates the alternative splicing of NUMB via binding to two RNA elements in its pre-mRNA, which in turn suppresses cell proliferation and prevents the activation of the Notch signaling pathway. We further show that QKI-5 inhibits splicing by selectively competing with a core splicing factor SF1 for binding to the branchpoint sequence. Taken together, our data reveal QKI as a critical regulator of splicing in lung cancer and suggest a novel tumor suppression mechanism involving QKI-mediated regulation of the Notch signaling pathway.

TP53-induced glycolysis and apoptosis regulator (TIGAR) inhibits glycolysis and increases the flow of pentose phosphate pathway (PPP), which generates NADPH and pentose. We hypothesized that TIGAR plays a neuroprotective role in brain ischemia as neurons do not rely on glycolysis but are vulnerable to oxidative stress. We found that TIGAR was highly expressed in brain neurons and was rapidly upregulated in response to ischemia/reperfusion insult in a TP53-independent manner. Overexpression of TIGAR in normal mice with lentivirus reduced ischemic neuronal injury, whereas lentivirus-mediated TIGAR knockdown aggravated it. In cultured primary neurons, increasing TIGAR expression reduced oxygen and glucose deprivation (OGD)/reoxygenation-induced injury, whereas decreasing its expression worsened the injury. The glucose 6-phosphate dehydrogenase was upregulated in mouse and cellular models of stroke, and its upregulation was further enhanced by overexpression of TIGAR. Supplementation of NADPH also reduced ischemia/reperfusion brain injury and alleviated TIGAR knockdown-induced aggravation of ischemic injury. In animal and cellular stroke models, ischemia/ reperfusion increased mitochondrial localization of TIGAR. OGD/reoxygenation-induced elevation of ROS, reduction of GSH, dysfunction of mitochondria, and activation of caspase-3 were rescued by overexpression of TIGAR or supplementation of NADPH, while knockdown of TIGAR aggravated these changes. Together, our results show that TIGAR protects ischemic brain injury via enhancing PPP flux and preserving mitochondria function, and thus may be a valuable therapeutic target for ischemic brain injury.

Despite the widespread use of the blockade of immune checkpoints, for a significant number of cancer patients, these therapies have proven ineffective, presumably due to the immunosuppressive nature of the tumor microenvironment (TME). Critical drivers of immune escape in the TME include tumor-associated macrophages (TAMs) and myeloid-derived suppressor cells (MDSCs), which not only mediate immune suppression, but also facilitate metastatic dissemination and impart resistance to immunotherapies. Thus, strategies that convert them into tumor fighters may offer great therapeutic potential. In this study, we evaluated whether pharmacologic modulation of macrophage phenotype by HDAC inhibitors (HDACi) could produce an anti-tumor effect. We demonstrated that low-dose HDACi trichostatin-A (TSA) markedly reshaped the tumor immune microenvironment by modulating the suppressive activity of infiltrating macrophages and inhibiting the recruitment of MDSCs in various tumors. These actions, in turn, augmented anti-tumor immune responses and further enhanced anti-tumor effects of immunotherapies. HDAC inhibition, however, also upregulated PD-L1, thereby limiting the beneficial therapeutic effects. Indeed, combining low-dose TSA with anti-PD-L1 in this model significantly enhanced the durability of tumor reduction and prolonged survival of tumor-bearing mice, compared with the effect of either treatment alone. These data introduce HDAC inhibition as a potential means to harness the anti-tumor potential of macrophages in cancer therapy.

Summary• Villin is one of the major actin filament bundling proteins in plants. The function of Arabidopsis VILLINs (AtVLNs) is still poorly understood in living cells. In this report, the biochemical activity and cellular function of AtVLN4 were examined.• The biochemical property of AtVLN4 was characterized by co-sedimentation assays, fluorescence microscopy and spectroscopy of pyrene fluorescence. The in vivo function of AtVLN4 was analysed by ectopically expressing it in tobacco pollen and examining the phenotypes of its T-DNA insertional plants.• Recombinant AtVLN4 protein exhibited multiple activities on actin, including actin filament bundling, calcium (Ca 2+ )-dependent filament severing and barbed end capping. Expression of AtVLN4 in tobacco pollen induced the formation of supernumerary actin cables and reduced pollen tube growth. Loss of function of AtVLN4 resulted in slowing of root hair growth, alteration in cytoplasmic streaming routes and rate, and reduction of both axial and apical actin bundles.• Our results demonstrated that AtVLN4 is involved in root hair growth through regulating actin organization in a Ca 2+ -dependent manner.