Biomedical subjects

Takashi Sasayama

Publications and source records attributed to Takashi Sasayama.

4 recordsLinked to original sources

PubMed2026

A multicenter randomized phase II/III trial of salvage treatment for refractory primary central nervous system lymphoma using tirabrutinib: JCOG2314 (ReSTART).

Primary central nervous system lymphoma (PCNSL) is an aggressive malignancy. Patients refractory to high-dose methotrexate-based induction therapy have an extremely poor prognosis. Although whole-brain radiotherapy (WBRT) is the standard salvage treatment and provides potent tumor control, early functional deterioration and late neurocognitive toxicity remain major concerns. A phase I/II trial on relapsed or refractory PCNSL demonstrated favorable efficacy and tolerability of tirabrutinib, a second-generation selective Bruton's tyrosine kinase inhibitor. Tirabrutinib's oral administration has enabled outpatient management. However, its clinical value for induction-refractory PCNSL remains uncertain. We designed a multicenter, randomized phase II/III trial (JCOG2314) to assess the non-inferiority of tirabrutinib to WBRT in overall survival and its potential to reduce functional deterioration and cognitive impairment. A total of 94 patients from 49 institutions will be enrolled over 4 years. The trial has been registered in the Japan Registry of Clinical Trials (study number: jRCT1031250645).

Humans↗

PubMed2026

Leptomeningeal Dissemination in TERT Promoter-mutant Anaplastic Pleomorphic Xanthoastrocytoma Responding to BRAF-MEK Inhibition: A Case Report.

Pleomorphic xanthoastrocytoma is a rare brain tumor that frequently harbors the oncogenic BRAF V600E mutation. Approximately 28.6%-47% of high-grade pleomorphic xanthoastrocytomas are associated with TERT promoter mutation and leptomeningeal dissemination, for which no established treatment exists and the prognosis remains poor. Combination therapy with BRAF and MEK inhibitors has demonstrated efficacy in BRAF V600E-mutant brain tumors. We report a case of a 22-year-old man with a right temporal lobe tumor initially diagnosed as World Health Organization grade 2 pleomorphic xanthoastrocytoma after gross total resection. Two years later, the tumor recurred and underwent malignant transformation to World Health Organization grade 3 pleomorphic xanthoastrocytoma. At the third resection, pathological and genomic analyses confirmed BRAF V600E mutation together with TERT promoter mutation. Following chemoradiotherapy, spinal leptomeningeal dissemination developed. After spinal irradiation, dabrafenib plus trametinib was initiated, resulting in partial radiological response and symptomatic improvement. Although regrowth occurred 10 months after initiation of targeted therapy, the patient remains alive at the time of writing. Here, we report a case of recurrent anaplastic BRAF V600E-mutant pleomorphic xanthoastrocytoma with leptomeningeal dissemination that showed a transient but clinically meaningful response to combined BRAF-MEK inhibition and spinal radiation therapy. In addition, this case raises the possibility of an association between TERT promoter mutation and leptomeningeal dissemination, although further studies are required to clarify this relationship.

BRAF V600E↗

PubMed2003

Aurora-A and an interacting activator, the LIM protein Ajuba, are required for mitotic commitment in human cells.

Aurora family kinases contribute to regulation of mitosis. Using RNA interference in synchronized HeLa cells, we now show that Aurora-A is required for mitotic entry. We found that initial activation of Aurora-A in late G2 phase of the cell cycle is essential for recruitment of the cyclin B1-Cdk1 complex to centrosomes, where it becomes activated and commits cells to mitosis. A two-hybrid screen identified the LIM protein Ajuba as an Aurora-A binding protein. Ajuba and Aurora-A interact in mitotic cells and become phosphorylated as they do so. In vitro analyses revealed that Ajuba induces the autophosphorylation and consequent activation of Aurora-A. Depletion of Ajuba prevented activation of Aurora-A at centrosomes in late G2 phase and inhibited mitotic entry. Overall, our data suggest that Ajuba is an essential activator of Aurora-A in mitotic commitment.

Animals↗

PubMed2002

Roles of aurora-A kinase in mitotic entry and G2 checkpoint in mammalian cells.

BACKGROUND: Various mitotic events are controlled by Cdc2-cyclin B and other mitotic kinases. Aurora/Ipl1-related mitotic kinases were proved to play key roles in mitotic progression in diverse lower organisms. Aurora-A is a mammalian counterpart of aurora/Ipl1-related kinases and is thought to be a potential oncogene. However, the regulation of aurora-A activation and the commitment of aurora-A in the progression of G2-M phase are largely unknown in mammalian cells. RESULTS: We demonstrated that aurora-A is activated depending on the activation of Cdc2-cyclin B in mammalian cells. Since Cdc2-cyclin B does not directly phosphorylate aurora-A, indirect pathways such as the inhibition of PP1 by Cdc2-cyclin B may act for the activation of aurora-A kinase. Microinjection of anti-aurora-A antibodies into HeLa cells at late G2 phase caused a significant delay in mitotic entry. Furthermore, aurora-A activation at G2-M transition was inhibited by DNA damage, and the over-expression of aurora-A induced the abrogation of the DNA damage-induced G2 checkpoint. CONCLUSIONS: Aurora-A is activated downstream of Cdc2-cyclin B and plays crucial roles in proper mitotic entry and G2 checkpoint control. Dysregulation of aurora-A induces abnormal G2-M transition in mammalian cells and may lead to chromosome instability, which results in the development and progression of malignant tumours.

Animals↗