The importance of circulating tumor cells (CTC) is well recognized. However, the biological characteristics of CTC in the bloodstream have not yet been examined in detail, due to the limited number of CTC cell lines currently available. Thirty-nine CTC cell lines were reported by 2021. For successful cell culturing, these CTC cell lines were reviewed. Previous studies on short-term cultures of CTC also analyzed approaches for establishing the long-term culture of CTC. Negative selection, hypoxic conditions, three-dimensional conditions, and careful management are preferable for the long-term culture of CTC. However, the establishment of CTC cell lines is dependent on the specific characteristics of each cell type. Therefore, a method to establish CTC cell lines has not yet been developed. Further efforts are needed to resolve this issue.

Oesophageal squamous cell carcinoma (ESCC) is an aggressive cancer that resulted in ~400,000 mortalities worldwide in 2012. It was reported previously that fibroblast growth factor receptor-like 1 (FGFRL1) is highly expressed in ESCC patients with lymph node metastasis and poor prognosis accordingly. FGFRL1 is an FGFR that lacks tyrosine kinase activity, whereas the activity is critical for other FGFRs to activate intracellular signalling. The mechanism by which FGFRL1 promotes the aggressiveness of ESCCs is unknown. In the present study, two independent FGFRL1-deficient cell lines were generated from human ESCC KYSE520 cells, in order to investigate the relationship of FGFRL1 with the aggressiveness of ESCCs. FGFRL1-deficiency did not affect proliferation of KYSE520 cells in vitro. However, a xenograft mouse model demonstrated that FGFRL1-deficiency decelerated tumour growth in vivo. The haematoxylin-eosin staining identified that FGFRL1-deficient cells formed well-differentiated squamous cell carcinomas, whereas wild-type cells formed moderately differentiated squamous cell carcinomas. Microarray analysis of mRNA expression revealed that FGFRL1-depletion resulted in decreased expression of proteins associated with motility and invasion of tumour cells, matrix metalloproteinase-1 and fibroblast growth factor binding protein 1. The wound-healing assay indicated that depleting FGFRL1 reduced cell motility. Furthermore, the invasiveness of FGFRL1-deficient cells was lesser than that of wild-type KYSE520 cells. In the FGFRL1-deficient KYSE520 cells, actin filaments around the nucleus were observed sparsely, whereas the filaments along the plasma membranes were observed as frequently as those in the parent KYSE520 cells. These results demonstrate that FGFRL1 may be involved in regulation of protein expression, actin filament assembly and tumorigenic potential of ESCC cells.

Fibroblast growth factor receptor-like 1 (FGFRL1) belongs to the FGFR protein family. We previously reported that FGFRL1 is highly expressed in esophageal squamous cell carcinoma (ESCC) patients with lymph node metastasis and with the depth of ESCCs. Furthermore, transient inhibition of FGFRL1 expression induces cell cycle arrest and apoptosis of ESCC cells. However, the intracellular domain of FGFRL1 lacks the tyrosine kinase domain. Thus the mechanisms of which FGFRL1 contributes to the development of ESCC are unclear. Two cell lines (Clone 15 and 21) deficient for FGFRL1 expression were established from an ESCC cell line (KYSE520) using the CRISPR-Cas9 method. We evaluated the characteristics of these two cell lines in vitro and in vivo. In these FGFRL1-deficient KYSE520 cells, actin filaments around the nucleus were observed sparsely, whereas the filaments along the plasma membranes were observed as strong as those in the parent KYSE520 cells. Depleting FGFRL1 reduced cell motility in vitro and, decelerated tumor growth in a mouse xenograft model. Microarray analysis of mRNA expression revealed that FGFRL1-depletion resulted in reduced expression of MMP-1 and FGFBP1. In conclusions, FGFRL1-deficiency reduced both cell motility and tumor growth of KYSE520 cells. This is consistent with that high expression of FGFRL1 coincident with lymph node metastasis and poor prognosis. These results demonstrate that FGFRL1 expressed in ESCC cells has a role in aggressiveness of ESCCs. Citation Format: Yoshinori Takei, Takafumi Matsumura, Kazuaki Watanabe, Hirokazu Nakamine, Tetsuo Sudo, Kazuharu Shimizu, Yutaka Shimada. FGFRL1 deficiency reduces motility and tumor growth of cells derived from esophageal squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2513.

Abstract Background: The findings of a recent analysis on microRNAs (miRNAs) suggest that circulating miRNAs have potential as biomarkers of esophageal squamous cell carcinoma (ESCC). In order to identify specific miRNAs of ESCC, we analyzed the circulating miRNAs of patients who underwent endoscopic mucosal resection (EMR) and esophagectomy. Method: After obtaining written informed consent, we collected paired (pre and post treatment) blood samples from 60 superficial ESCC patients and 42 pretreatment advanced ESCC patients between 2011 and 2015. Samples were divided into training (40 superficial ESCC and 22 advanced ESCC) and test (15 superficial ESCC and 20 advanced ESCC) cohorts according to the period at which they were obtained (between 2011 and 2013 and between 2014 and 2015). Fifty-five patients underwent EMR and were confirmed as stage 0 or Stage 1a. Microarray analyses of blood samples were performed using the 3D-Gene miRNA microarray platform (Toray). Normalization was achieved using the Quantile method, and poor quality samples were excluded from the analysis. Any two clinical groups were compared using a two-sided Student’s t-test. miRNAs exhibiting significant differences were subsequently evaluated using a logistic regression analysis (LRA). Multivariate LRA, Akaike’s Information Criterion (AIC), and Receiver Operating Characteristic (ROC) analyses were performed in order to evaluate the diagnostic power of miRNA combinations. In all series, we used post-EMR patients as control cases. Results: Twelve miRNAs (miR-6722-5p, 489, 4525, 409-3p, 6088, 3678-5p, 197-5p, 4281, 5090, 3173-3p, 762, and 1470) were selected as discriminant markers (S-combination: AUC 1.00) of superficial ESCC, while 4 miRNAs (miR-4723-3p, 4646-3p, 2392, and 1236-3p) were selected as discriminant markers (A-combination: AUC 1.00) of advanced ESCC in the training cohort. There were no overlap miRNAs between the two combinations. In the test cohort, the S-combination discriminated superficial ESCC (AUC 1.00), while the A-combination discriminated advanced ESCC (AUC 1.00) from post-EMR patients. Furthermore, the S-combination discriminated advanced ESCC in the test cohort (AUC 1.00). However, the A-combination did not clearly discriminate superficial ESCC (AUC 0.833). Conclusion: Our results suggest that selected miRNAs are useful biomarkers for the discrimination of ESCC. However, biomarkers of superficial ESCC and advanced ESCC may differ. Citation Format: Yutaka Shimada, Yoshinori Takei, Tomoyuki Okumura, Takuya Nagata, Haruka Fujinami, Miwako Arima, Tetsuya Abe, Yasumasa Niwa, Masahiro Tajika, Tetsuo Sudo, Kazuharu Shimizu. Circulating microRNA expression profiles as a novel diagnostic biomarker for esophageal squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4430. doi:10.1158/1538-7445.AM2017-4430

The Psmb11-encoded β5t subunit of the thymoproteasome, which is specifically expressed in cortical thymic epithelial cells (cTECs), is essential for the optimal positive selection of functionally competent CD8+ T cells in mice. Here, we report that a human genomic PSMB11 variation, which is detectable at an appreciable allele frequency in human populations, alters the β5t amino acid sequence that affects the processing of catalytically active β5t proteins. The introduction of this variation in the mouse genome revealed that the heterozygotes showed reduced β5t expression in cTECs and the homozygotes further exhibited reduction in the cellularity of CD8+ T cells. No severe health problems were noticed in many heterozygous and 5 homozygous human individuals. Long-term analysis of health status, particularly in the homozygotes, is expected to improve our understanding of the role of the thymoproteasome-dependent positive selection of CD8+ T cells in humans.

Just as normal stem cells require niche cells for survival, leukemia-initiating cells (LICs) may also require niche cells for their maintenance. Chronic myeloid leukemia (CML) is caused by the activity of BCR-ABL, a constitutively active tyrosine kinase. CML therapy with tyrosine kinase inhibitors is highly effective; however, due to the persistence of residual LICs, it is not curative. Several factors are known to support CML LICs, but purification of LICs and a thorough understanding of their niche signals have not yet been achieved. Using a CML-like mouse model of myeloproliferative disease, we demonstrate that CML LICs can be divided into CD25(+)FcεRIα(-) Lineage marker (Lin)(-) Sca-1(+)c-Kit(+) (F(-)LSK) cells and CD25(-)F(-)LSK cells. The CD25(+)F(-)LSK cells had multilineage differentiation capacity, with a preference toward cytokine-producing mast cell commitment. Although cells interconverted between CD25(-)F(-)LSK and CD25(+)F(-)LSK status, the CD25(+)F(-)LSK cells exhibited higher LIC capacity. Our findings suggest that interleukin-2 derived from the microenvironment and CD25 expressed on CML LICs constitute a novel signaling axis. The high levels of CD25 expression in the CD34(+)CD38(-) fraction of human CML cells indicate that CD25(+) LICs constitute an "LIC-derived niche" that could be preferentially targeted in therapy for CML.

Germ cells are similar to pluripotent stem cells in terms of gene expression patterns and the capacity to convert to pluripotent stem cells in culture. The factors involved in germ cell development are also able to reprogram somatic cells. This suggests that germ cells are useful tools for investigating the mechanisms responsible for somatic cell reprograming. In this study, the expression of reprograming factors in primordial germ cells (PGCs) was analyzed. PGCs expressed Oct3/4, Sox2, and c-Myc but not Klf4. However, Klf2, Klf5, Essrb, or Essrg, which were expressed in PGCs, could compensate for Klf4 during somatic cell reprograming. Furthermore, PGCs could be converted to a pluripotent state by infection with any of the known reprogramming factors (Oct3/4, Sox2, Klf4, and c-Myc). These cells were designated as multipotent PGCs (mPGCs). Contrary to differences in the origins of somatic cells in somatic cell reprogramming, we hypothesized that the gene expression levels of the reprogramming factors would vary in mPGCs. Candidate genes involved in the regulation of tumorigenicity and/or reprogramming efficiency were identified by comparing the gene expression profiles of mPGCs generated by the exogenous expression of c-Myc or L-Myc.

To understand mechanisms underlying acquisition of pluripotency, it is critical to identify cells that can be converted to pluripotent stem cells. For this purpose, we focused on unipotent primordial germ cells (PGCs), which can be reprogrammed into pluripotent embryonic germ (EG) cells under defined conditions. Treatment of PGCs with combinations of signaling inhibitors, including inhibitors of MAP2K (MEK), GSK3B (GSK-3beta), and TGFB (TGFbeta) type 1 receptors, induced cells to enter a pluripotent state at a high frequency (12.1%) by Day 10 of culture. When we employed fluorescence-activated cell sorting to monitor conversion of candidate cells to a pluripotent state, we observed a cell cycle shift to S phase, indicating enrichment of pluripotent cells, during the early phase of EG formation. Transcriptome analysis revealed that PGCs retained expression of some pluripotent stem cell-associated genes, such as Pou5f1 and Sox2, during EG cell formation. On the other hand, PGCs lost their germ lineage characteristics and acquired expression of pluripotent stem cell markers, such as Klf4 and Eras. The overall gene expression profiles revealed by this system provide novel insight into how pluripotency is acquired in germ-committed cells.

Germ cells possess the unique ability to acquire totipotency during development in vivo as well as give rise to pluripotent stem cells under the appropriate conditions in vitro. Recent studies in which somatic cells were experimentally converted into pluripotent stem cells revealed that genes expressed in primordial germ cells (PGCs), such as Oct3/4, Sox2, and Lin28, are involved in this reprogramming. These findings suggest that PGCs may be useful for identifying factors that successfully and efficiently reprogram somatic cells into toti- and/or pluripotent stem cells. Here, we show that Blimp-1, Prdm14, and Prmt5, each of which is crucial for PGC development, have the potential to reprogram somatic cells into pluripotent stem cells. Among them, Prmt5 exhibited remarkable reprogramming of mouse embryonic fibroblasts into which Prmt5, Klf4, and Oct3/4 were introduced. The resulting cells exhibited pluripotent gene expression, teratoma formation, and germline transmission in chimeric mice, all of which were indistinguishable from those induced with embryonic stem cells. These data indicate that some of the factors that play essential roles in germ cell development are also active in somatic cell reprogramming.

While murine B- and T-lymphopoiesis require overlapping molecules, they occur in separate organs: the bone marrow (BM) and the thymus, respectively. The BM microenvironment is incapable of supporting T-lymphopoiesis because of insufficient interactions of Notch1 with delta-like ligand (Dll). Notch1/Dll interactions also play a role in the suppression of B-lymphopoiesis in the thymus. However, it is still unclear whether the Notch1/Dll interaction alone explains why the thymus does not support B-lymphopoiesis. In this study, we compared the precursor population colonizing the thymus with that in the BM by culturing them on stromal cells expressing abundant Dll1. We demonstrated that Flt3+ Il7r+ B220+ Cd19+ BM cells gave rise to B cells under this condition. We defined them as resistant to Dll1. In the thymus, Dll1-resistant cells were undetectable. This suggested that the absence of Dll1-resistant cells might explain the absence of B-lymphopoiesis in the thymus.

Genetic analyses of human mucoepidermoid carcinoma (MEC) revealed that the t(11; 19) (q21; p13) is responsible for its tumorigenesis during which the gene resulting from the fusion between Mammalian Mastermind like 2 and Mucoepidermoid carcinoma translocated 1 activates Hairy/Enhancer of split homologue 1 (HES1), a downstream of the Notch signal. However, in the previous studies, limited clinical cases (15 in total) were investigated for the translocation and HES1 expression. We examined the relevance of aberrant expression of HES1 in 40 cases of MEC and found that 30% of the cases showed the positive signal. No direct relationship of HES1 to the tumor malignancy grade measured by the AFIP score or to the cell proliferation rate was observed although HES1 positive cells were mostly squamous cells. We investigated 12 pleomorphic adenomas and 3 adenoid cystic carcinomas, but they were negative for HES1immunoreactivity with only one exceptional case in pleomorphic adenoma. On the contrary, 5 out of 6 cases of Warthin's tumor showed positive immunoreactivity in the epithelial component. Thus, HES1 expression may regulate specific differentiation of the salivary gland tumor cells, but not tumorigenesis.

Human T-cell lymphotropic virus type I (HTLV-I) is associated with various clinical disorders including adult T cell leukemia, myelopathy, arthropathy. Hypercalcemia resulting from osteoclast activation and a variety of hematopoietic abnormalities have been also observed in HTLV-I infected patients, however, precise mechanism about initial trigger(s) prior to presenting symptoms is still unknown. In this study, to assess effects of HTLV-I on hematopoiesis, we analysed characteristics of early hematopoietic precursors in HTLV-I env-pX transgenic rats. Progenitor cells for osteoclasts were significantly increased even in the marrow of asymptomatic env-pX rats. Progenitors for B cells were also highly enriched, while colony forming cells (CFC) elicited by GM-CSF(CFU-GM) and M-CSF(CFU-M) were comparable to normal littermates. Following arthritis in env-pX transgenic rats, osteoclastogenesis was further augmented and the CFCs were increased. Bone marrow cells carrying adjuvant-induced arthritis retained a constant number of progenitors for osteoclast and B lymphocytes, whereas the number of CFU-GM and CFU-M increased. These results indicate that the env-pX transgene affect early stages of osteoclast and B-cell lineages prior to developing diseases, in contrast, an increase of the CFCs was caused indirectly by arthritis. This study provides a novel standpoint for the mechanisms of pathogenesis by HTLV-I.