Oxidative stress-triggered Wnt signaling perturbation characterizes the tipping point of lung adeno-to-squamous transdifferentiation.

Lkb1 deficiency confers the Kras-mutant lung cancer with strong plasticity and the potential for adeno-to-squamous transdifferentiation (AST). However, it remains largely unknown how Lkb1 deficiency dynamically regulates AST. Using the classical AST mouse model (Kras LSL-G12D/+;Lkb1flox/flox, KL), we here comprehensively analyze the temporal transcriptomic dynamics of lung tumors at different stages by dynamic network biomarker (DNB) and identify the tipping point at which the Wnt signaling is abruptly suppressed by the excessive accumulation of reactive oxygen species (ROS) through its downstream effector FOXO3A. Bidirectional genetic perturbation of the Wnt pathway using two different Ctnnb1 conditional knockout mouse strains confirms its essential role in the negative regulation of AST. Importantly, pharmacological activation of the Wnt pathway before but not after the tipping point inhibits squamous transdifferentiation, highlighting the irreversibility of AST after crossing the tipping point. Through comparative transcriptomic analyses of mouse and human tumors, we find that the lineage-specific transcription factors (TFs) of adenocarcinoma and squamous cell carcinoma form a "Yin-Yang" counteracting network. Interestingly, inactivation of the Wnt pathway preferentially suppresses the adenomatous lineage TF network and thus disrupts the "Yin-Yang" homeostasis to lean towards the squamous lineage, whereas ectopic expression of NKX2-1, an adenomatous lineage TF, significantly dampens such phenotypic transition accelerated by the Wnt pathway inactivation. The negative correlation between the Wnt pathway and AST is further observed in a large cohort of human lung adenosquamous carcinoma. Collectively, our study identifies the tipping point of AST and highlights an essential role of the ROS-Wnt axis in dynamically orchestrating the homeostasis between adeno- and squamous-specific TF networks at the AST tipping point.

Metal transporter Slc39a10 regulates susceptibility to inflammatory stimuli by controlling macrophage survival.

Zn plays a key role in controlling macrophage function during an inflammatory event. Cellular Zn homeostasis is regulated by two families of metal transporters, the SLC39A family of importers and the SLC30A family of exporters; however, the precise role of these transporters in maintaining macrophage function is poorly understood. Using macrophage-specific Slc39a10-knockout (Slc39a10fl/fl;LysM-Cre+ ) mice, we found that Slc39a10 plays an essential role in macrophage survival by mediating Zn homeostasis in response to LPS stimulation. Compared with Slc39a10fl/fl mice, Slc39a10fl/fl;LysM-Cre+ mice had significantly lower mortality following LPS stimulation as well as reduced liver damage and lower levels of circulating inflammatory cytokines. Moreover, reduced intracellular Zn concentration in Slc39a10fl/fl;LysM-Cre+ macrophages led to the stabilization of p53, which increased apoptosis upon LPS stimulation. Concomitant knockout of p53 largely rescued the phenotype of Slc39a10fl/fl;LysM-Cre+ mice. Finally, the phenotype in Slc39a10fl/fl;LysM-Cre+ mice was mimicked in wild-type mice using the Zn chelator TPEN and was reversed with Zn supplementation. Taken together, these results suggest that Slc39a10 plays a role in promoting the survival of macrophages through a Zn/p53-dependent axis in response to inflammatory stimuli.

Shen-Fu injection reduces impaired myocardial ß-adrenergic receptor signaling after cardiopulmonary resuscitation.

BACKGROUND: Post-resuscitation myocardial dysfunction has been implicated as a major cause of fatal outcome in patients who survive initially successful cardiopulmonary resuscitation (CPR). In our previous study, we found that impaired myocardial ß-adrenergic receptor (AR) signaling is a key mechanism in post-resuscitation myocardial dysfunction and Shen-Fu injection (SFI) can attenuate post-resuscitation myocardial dysfunction. However, whether SFI can prevent impaired post-resuscitation myocardial ß-AR signaling is not yet known. In this study, we investigated the effect of SFI on impaired myocardial ß-AR signaling occurring post-resuscitation in a porcine model of cardiac arrest. METHODS: Ventricular fibrillation was induced electrically in anesthetized male landrace domestic pigs. After 4 minutes of untreated ventricular fibrillation, cardiopulmonary resuscitation was initiated. Sixteen successfully resuscitated pigs were randomized to receive a continuous infusion of either SFI (0.5 ml/min; n = 8) or saline (placebo; n = 8) for 6 hours, beginning 15 minutes after the return of spontaneous circulation (ROSC). Hemodynamic and echocardiographic data were recorded. ß-AR signaling was assessed at 6 hours after the intervention by measuring myocardial adenylate cyclase activity, ß-AR density and ß-AR kinase expression. RESULTS: Treatment with SFI produced better maximum rate of left ventricular pressure increase (dp/dt(max)) and maximum rate of left ventricular pressure decline (-dp/dt(max)), cardiac output, and ejection fraction after ROSC. SFI treatment was also associated with lower myocardial ß-adrenergic receptor kinase expression, whereas basal and isoproterenol-stimulated adenylate cyclase activity and the total ß-AR density were significantly increased in the SFI group when compared with the placebo group. CONCLUSION: SFI attenuated post-resuscitation myocardial dysfunction by preventing impaired myocardial ß-AR signaling after CPR.

HER2YVMA drives rapid development of adenosquamous lung tumors in mice that are sensitive to BIBW2992 and rapamycin combination therapy.

Mutations in the HER2 kinase domain have been identified in human clinical lung cancer specimens. Here we demonstrate that inducible expression of the most common HER2 mutant (HER2(YVMA)) in mouse lung epithelium causes invasive adenosquamous carcinomas restricted to proximal and distal bronchioles. Continuous expression of HER2(YVMA) is essential for tumor maintenance, suggesting a key role for HER2 in lung adenosquamous tumorigenesis. Preclinical studies assessing the in vivo effect of erlotinib, trastuzumab, BIBW2992, and/or rapamycin on HER2(YVMA) transgenic mice or H1781 xenografts with documented tumor burden revealed that the combination of BIBW2992 and rapamycin is the most effective treatment paradigm causing significant tumor shrinkage. Immunohistochemical analysis of lung tumors treated with BIBW2992 and rapamycin combination revealed decreased phosphorylation levels for proteins in both upstream and downstream arms of MAPK and Akt/mTOR signaling axes, indicating inhibition of these pathways. Based on these findings, clinical testing of the BIBW2992/rapamycin combination in non-small cell lung cancer patients with tumors expressing HER2 mutations is warranted.