Entry into mitosis depends on the activity of cyclin-dependent kinases (CDKs). Conversely, exit from mitosis occurs when mitotic cyclins are degraded, thereby extinguishing CDK activity. Exit from mitosis must also require mitotic phosphoproteins to revert to their interphase hypophosphorylated forms, but there is a controversy about which phosphatase(s) is/are responsible for dephosphorylating the CDK substrates. We find that PP2A associated with a B55d subunit is relatively specific for a model mitotic CDK substrate in Xenopus egg extracts. The phosphatase activity measured by this substrate is regulated during the cell cycle-high in interphase and suppressed during mitosis. Depletion of PP2A-B55d (in interphase) from 'cycling' frog egg extracts accelerated their entry into mitosis and kept them indefinitely in mitosis. When PP2A-B55d was depleted from mitotic extracts, however, exit from mitosis was hardly delayed, showing that other phosphatase(s) are also required for mitotic exit. Increasing the concentration of PP2A-B55d in extracts by adding recombinant enzyme inhibited the entry into mitosis. This form of PP2A seems to be a key regulator of entry into and exit from mitosis.

The stable expansion of tissue-specific stem cells in vitro has contributed to research on several organs. Alveolar epithelial type II (AT2) cells function as tissue stem cells in the lung, but robust models for studying human AT2 cells are lacking. Here we report a method for the efficient generation and long-term expansion of alveolar organoids (AOs) harboring SFTPC alveolar stem cells derived from human induced pluripotent stem cells (hiPSCs). hiPSC-derived SFTPC cells self-renewed, with transcriptomes and morphology consistent with those of AT2 cells, and were able to differentiate into alveolar epithelial type I (AT1)-like cells. Single-cell RNA-seq of SFTPC cells and their progenitors demonstrated that their differentiation process and cellular heterogeneity resembled those of developing AT2 cells in vivo. AOs were applicable to drug toxicology studies recapitulating AT2-cell-specific phenotypes. Our methods can help scientists overcome the limitations of current approaches to the modeling of human alveoli and should be useful for disease modeling and regenerative medicine.

Alveologenesis is a developmental step involving the expansion of the lung surface area which is essential for gas exchange. The gas exchange process is mediated by alveolar type I (AT1) cells, which are known to be differentiated from alveolar type II (AT2) or bipotent cells. Due to the difficulty of isolating and culturing primary AT1 cells, the mechanism underlying their differentiation is not completely understood. We performed single-cell RNA sequencing (scRNA-seq) of fibroblast-dependent alveolar organoids (FD-AOs), including human induced pluripotent stem cell (hiPSC)-derived epithelial cells and fetal lung fibroblasts, and identified hiPSC-derived AT1 (iAT1) cells. A comparison of the FD-AOs and fibroblast-free alveolar organoids showed that iAT1 cells were mainly present in the FD-AOs. Importantly, the transcriptomes of iAT1 cells were remarkably similar to those of primary AT1 cells. Additionally, XAV-939, a tankyrase inhibitor, increased iAT1 cells in passaged FD-AOs, suggesting that these cells were differentiated from hiPSC-derived AT2 (iAT2) cells through the inhibition of canonical Wnt signaling. Consequently, our scRNAseq data allowed us to define iAT1 cells and identify FD-AOs as a useful model for investigating the mechanism underlying human AT1 cell differentiation from AT2 cells in vitro.

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BackgroundThere have been few data on the chemotherapy in elderly advanced non-small cell lung cancer (NSCLC) patients with poor performance status (PS), and usefulness of chemotherapy for such patients remains unclear. The objective of this study was to identify factors that predicted the survival benefit of chemotherapy.MethodsAll consecutive elderly patients (≥75 years) with advanced NSCLC, Eastern Cooperative Oncology Group PS ≥2, EGFR mutation wild type/unknown, and newly diagnosed from January 2009 to December 2012 at a tertiary hospital were retrospectively reviewed.ResultsWe enrolled 59 patients, and 31 patients received at least one chemotherapy regimen (chemotherapy group). However, 28 patients received best supportive care (BSC) alone (BSC group). The proportion of PS 2 and serum albumin levels was significantly higher in the chemotherapy group than in the BSC group. In the chemotherapy group, log-rank testing did not show statistically significant differences in overall survival (OS) between the single-agent therapy group and carboplatin-based doublet therapy group; however, the OS of patients receiving chemotherapy for only 1 cycle (early termination) was significantly shorter than patients receiving chemotherapy for ≥2 cycles. Hypoalbuminemia was not only a risk factor for the early termination of chemotherapy but also an independent prognostic factor in the chemotherapy group. A receiver operating characteristic curve analysis showed that the best cut-off value was 3.40 g/dL. In patients with serum albumin levels ≥3.40 g/dL, OS was significantly better in the chemotherapy group than in the BSC group (p = 0.0156), however, patients with serum albumin levels <3.40 g/dL exhibited poor prognosis regardless of the presence or absence of chemotherapy.ConclusionIn the elderly NSCLC patients with poor PS, serum albumin levels may help identify certain patient populations more likely to receive a survival benefit of systemic chemotherapy.Electronic supplementary materialThe online version of this article (10.1186/s12885-017-3814-3) contains supplementary material, which is available to authorized users.