Asymmetric cell division (ACD) is a fundamental mechanism that balances self-renewal and differentiation in stem cells and is closely linked to tissue homeostasis and tumor development. The centrosome, a key organelle for microtubule organization and cell division, consists of a mother and a daughter centriole that differ in structure and maturation state. Increasing evidence suggests that this intrinsic asymmetry of centrosomes plays an important role in ACD. In human neuroblastoma cells, asymmetric cell division is accompanied by biased inheritance of centrosomes and recycling endosomes. Our recent studies show that the centrosomal protein, Odf2 (cenexin), regulates the asymmetric distribution of CD133-positive recycling endosomes during cytokinesis. Loss of Odf2 disrupts this asymmetry and converts ACD into symmetric cell division (SCD), generating two equivalent daughter cells. These findings indicate that centrosome maturity, mediated by Odf2, functions as a switch that determines cell fate during division. This review summarizes current knowledge on the relationship between centrosomes and ACD, with a focus on human neuroblastoma cells. We propose that the centrosome is not merely a structural component of the mitotic machinery but also a regulatory hub that controls stemness, differentiation, and cell fate decisions.

Programmed death-1 (PD-1) is a negative regulator of immune responses. In PD-1-deficient mice, autoimmune symptoms develop only as they age. In cancer immunotherapy models, PD-1 has been shown to prevent cytotoxic T lymphocytes from attacking cancer cells that express mutation-derived neoantigens. To understand the common molecular mechanisms underlying these findings, we hypothesize that PD-1 suppresses excessive immune responses against neoantigens in normal somatic cells of aged individuals. To test this, we introduced random mutations into the genome of wild-type (WT) and PD-1 knockout (KO) mice. We employed a genetic approach of random mutagenesis by deleting the Msh2 gene, which is essential for the mismatch-repair activity in the nucleus and, therefore, for the suppression of accumulation of random mutations in the genome. Granulomatous inflammatory responses were elicited in Msh2/PD-1 double KO mice but not in Msh2 single KO mice. In parabiosis experiments, surgical connection of an Msh2 KO mouse with a PD-1 KO mouse resulted in the development of inflammatory lesions in the Msh2 KO mouse but not in the Msh2 KO mouse surgically connected with a WT mouse. These results strongly support our hypothesis about the physiological function(s) of PD-1.

Objectives: Circulating tumor cells (CTCs) are implicated in cancer progression and metastasis and are regarded as indicators of therapeutic efficacy and prognosis. In this study, we identified previously unreported rosette-like cell aggregates, designated complementary CTCs (C-CTCs), and evaluated their morphology and diagnostic performance. Methods: Forty-six patients with advanced solid cancer and 60 healthy volunteers were examined. CTCs and C-CTCs were detected using flow cytometry (FCM) and fluorescence microscopy (Imaging) with epithelial markers (EpCAM and cytokeratin, CK). Diagnostic accuracy was assessed by receiver operating characteristic (ROC) analysis. In six patients, CTC and C-CTC counts were compared before and after radiofrequency hyperthermia. Results: Imaging detected EpCAM-positive C-CTCs in 54.3% of patients and 1.7% of controls (p < 0.001). CK-positive C-CTCs were observed in 45.6% of patients and none of the controls (p < 0.001). ROC analysis showed that EpCAMpositive C-CTCs had the highest diagnostic accuracy (AUC = 0.748), exceeding EpCAM-positive CTCs (FCM, AUC = 0.533) and CK-positive CTCs (FCM, AUC = 0.579). Among six patients undergoing hyperthermia, C-CTCs increased in several cases. Conclusions: EpCAM-positive C-CTCs were specifically detected in patients with advanced cancer and demonstrated greater diagnostic utility than conventional CTCs. The observed increase in C-CTCs after hyperthermia suggests a potential role as indicators of treatment response and immune activation. These fi ndings indicate that C-CTCs may represent exploratory biomarker candidates warranting further investigation.

Cytometry technicians have the mission of obtaining reliable results, which requires extensive knowledge and outstanding skills. Specifically, this includes accurate sample preparation, suppression of nonspecific signals using antibodies and appropriate controls, understanding the fundamental principles of equipment such as laser, scatter light (FSC, SSC), and fl uorescence, setting up fl uorescence compensation, gate setting and doublet removal in analysis, as well as knowledge and skills in meticulous equipment maintenance and performance evaluation. The examination for Certifi ed Cytometrists (CC) aims to verify the level of profi ciency in these areas. What stands out in the current state of the certifi cation examination is the increase in examinees among clinical laboratory technicians, which can be attributed to the growing importance of cytometry technology in healthcare. Consequently, there is signifi cant expectation for the value of CC as a means of enhancing expertise and advancing careers in the workplace. In clinical testing, knowledge of immunophenotypes related to hematologic tumors and their clinical characteristics is essential for advancing analysis. Furthermore, selecting optimal markers and panels considering disease inference and sample volume, as well as choosing appropriate gating strategies during analysis, are capabilities that should naturally be acquired by a CC. In the designated training sessions that are prerequisites for the certifi cation examination, lectures covering these topics are conducted, but they can hardly be considered complete. This is because the evolution of cytometry, which has greatly contributed to the advancement of immunobiology and tumor immunology, has become increasingly complex, necessitating a proper understanding of equipment that incorporates new technologies. Furthermore, it is not an exaggeration to say that a diverse range of knowledge and skills is required for detailed analysis of immune cells in cancer immunotherapy, setting detector sensitivity, and understanding multicolor analysis. For these various reasons, it is believed that a revision of the curriculum regarding the knowledge level goals (standards) expected of CC is necessary.

This lecture, “Fundamentals and Applications of cytometric analysis of DNA,” provides an overview of cytometric DNA analysis, including cell cycle and DNA ploidy, along with data interpretation. While DNA ploidy analysis has declined since its peak in the 1990s, cell cycle analysis remains widely used in research. Accurate interpretation requires integrated knowledge of biological phenomena such as genome doubling and tumor evolution. Recent advances have expanded cytometry applications, including extracellular vesicle analysis and novel detection technologies. Despite increasing specialization, broader knowledge beyond one’s routine practice is essential for problem solving. This lecture aims to provide foundational insights and promote interdisciplinary understanding within the cytometry community.

2024年7月6－7日，第34回日本サイトメトリー学会はオンライン方式で開催された。テーマは－Uniqueness－としたが，これは当学会が構成員の属性や研究テーマが多彩であるというユニークな特徴を持つことをふまえたものである。配信基地は前回と同じ未来のまち創造館 （金沢市） とし，当日は実行委員や学会役員，プロの司会者，金沢市にある学会サポート担当企業社員も集合し，配信に協力していただいた。当初の目標であった参加費のみで学会を開催することはできなかったが，素晴らしい講演が多数配信され，参加者は約300名と成功したように思える。私は本大会に会長として参加しており，事前の準備，プログラムの作成，大会当日の進行，反省について記したいと思う。