Koichi Ayukawa

The cytoskeletal and/or nuclear matrix molecules responsible for morphological changes associated with apoptosis were identified using monoclonal antibodies (mAbs). We developed mAbs against Triton X-100-insoluble components of HL-60 cells pretreated with all-trans retinoic acid. In particular, one mAb recognized a 22-kDa protein that exhibited intriguing behavior by forming an aggregate and appearing as a speck during apoptosis induced by retinoic acid and other anti-tumor drugs. Cloning and sequencing of its cDNA revealed that this protein comprises 195 amino acids and that its C-terminal half has a caspase recruitment domain (CARD) motif, characteristic of numerous proteins involved in apoptotic signaling. We referred to this protein as ASC (apoptosis-associated speck-like protein containing a CARD). The ASC gene was mapped on chromosome 16p11.2-12. The antisense oligonucleotides of ASC were found to reduce the expression of ASC, and consequently, etoposide-mediated apoptosis of HL-60 cells was suppressed. Our results indicate that ASC is a novel member of the CARD-containing adaptor protein family.

La autoantigen is a 47-kDa nuclear protein that binds to nascent polymerase III transcripts and a number of viral RNAs. We show that La protein was cleaved to generate a 43-kDa fragment during apoptosis of human leukemic HL-60 cells treated with camptothecin or etoposide. Immunofluorescence microscopy showed that the La protein level was increased in the cytoplasm during apoptosis of HL-60 cells. In addition, UV irradiation of HeLa cells led to the cleavage and redistribution of La protein upon apoptosis. Several lines of evidence show that La protein is cleaved by caspase-3 or closely related proteases at Asp-374 in the COOH terminus. When the full-length (La) and COOH-terminally truncated (La delta C374) forms of La protein were expressed as fusion proteins with green fluorescence protein (GFP), GFP-La delta C374 was predominantly cytoplasmic, whereas GFP-La was localized in the nucleus. These results suggest that La protein loses the nuclear localization signal residing in the COOH terminus upon cleavage and is thus redistributed to the cytoplasm during apoptosis.

Ubiquitin C-terminal hydrolase L1 (UCH-L1) is a component of the ubiquitin system, which has a fundamental role in regulating various biological activities. However, the functional role of the ubiquitin system in neurogenesis is not known. Here we show that UCH-L1 regulates the morphology of neural progenitor cells (NPCs) and mediates neurogenesis. UCH-L1 was expressed in cultured NPCs as well as in embryonic brain. Its expression pattern in the ventricular zone (VZ) changed between embryonic day (E) 14 and E16, which corresponds to the transition from neurogenesis to gliogenesis. At E14, UCH-L1 was highly expressed in the ventricular zone, where neurogenesis actively occurs; whereas its expression was prominent in the cortical plate at E16. UCH-L1 was very weakly detected in the VZ at E16, which corresponds to the start of gliogenesis. In cultured proliferating NPCs, UCH-L1 was co-expressed with nestin, a marker of undifferentiated cells. In differentiating cells, UCH-L1 was highly co-expressed with the early neuronal marker TuJ1. Furthermore, when UCH-L1 was induced in nestin-positive progenitor cells, the number and length of cellular processes of the progenitors decreased, suggesting that the progenitor cells were differentiating. In addition, NPCs derived from gad (UCH-L1-deficient) mice had longer processes compared with controls. The ability of UCH-L1 to regulate the morphology of nestin-positive progenitors was dependent on its binding affinity for ubiquitin but not on hydrolase activity; this result was also confirmed using gad-mouse-derived NPCs. These results suggest that UCH-L1 spatially mediates and enhances neurogenesis in the embryonic brain by regulating progenitor cell morphology.

Clinical experience of ceritinib in patients who progressed on alectinib is limited. In this prospective phase II study, we evaluated the activity of ceritinib in alectinib-pretreated patients with anaplastic lymphoma kinase (ALK)-rearranged metastatic (stage IIIB/IV) non-small-cell lung cancer (NSCLC) in Japan. All patients were required to have ≥1 measurable lesion per RECIST, 1.1, and a World Health Organization Performance Status (WHO PS) of 0-1. Prior crizotinib and/or up to 1 chemotherapy regimen was allowed. Primary endpoint was investigator-assessed overall response rate (ORR) per RECIST 1.1. Ceritinib was given at a dose of 750 mg/day fasted. A total of 20 patients were enrolled from August 2015 to March 2017. All patients received prior alectinib (100%), 13 (65.0%) patients received prior platinum-based chemotherapy, and 4 (20%) patients received prior crizotinib. Median duration of exposure and the follow-up time with ceritinib were 3.7 months (range: 0.4-15.1) and 11.6 months (range: 4.8-23.0), respectively. Investigator-assessed ORR was 25% (95% CI: 8.7-49.1). Key secondary endpoints, all investigator assessed, included disease control rate (70.0%; 95% CI: 45.7-88.1), time to response (median, 1.8 months; range: 1.8-2.0), and duration of response (median, 6.3 months; 95% CI: 3.5-9.2). Median progression-free survival was 3.7 months (95% CI: 1.9-5.3). The most common adverse events reported were diarrhea (85.0%), nausea (80.0%), and vomiting (65.0%). Based on our findings, ceritinib could be considered as one of the treatment options for patients with ALK-positive NSCLC who progressed on alectinib. (Trial registration no. NCT02450903).