Masako Kurashige

Tuberous sclerosis complex is a genetic disorder characterized by facial angiofibromas, intellectual disability, epilepsy, and tumor formation in multiple organs, including the kidney. Renal cell carcinoma occurs in 2%–4% of patients with tuberous sclerosis complex, often developing multiply and bilaterally. Renal cell carcinoma associated with this genetic disorder may include complex tumor heterogeneity caused by the spatially different mutational landscape. Herein, we report the case of a female patient with tuberous sclerosis complex who developed multiple renal tumors. A 44-year-old female patient with tuberous sclerosis complex developed three different histological types of tumor—angiomyolipoma, clear cell renal cell carcinoma, and papillary renal cell carcinoma—in the left kidney at first renal cell carcinoma recurrence. The papillary renal cell carcinoma was morphologically atypical, indicating that its occurrence was associated with the genetic disorder. Furthermore, whole-exome sequencing revealed distinct patterns of somatic mutation in the three tumor types, and the atypical papillary renal cell carcinoma possessed a different mutational landscape than that of typical papillary renal cell carcinomas. Our findings indicate that tumors associated with tuberous sclerosis complex may be diagnosed with careful pathological examination. Furthermore, somatic mutation profiles of these tumors revealed their unique features, providing important information for further understanding the mechanism of multiple tumor development in patients with tuberous sclerosis complex.

Summary: A population of mesenchymal stem cells, termed CXC chemokine ligand (CXCL)12‐abundant reticular (CAR) cells or leptin receptor‐expressing cells, are the major cellular component of niches for haematopoietic stem cells (HSCs) in murine bone marrow. CAR cells are characterized by several salient features, including much higher expression of CXCL12, stem cell factor (SCF), forkhead box C1 (FOXC1) and early B‐cell factor 3 (EBF3), which are essential for HSC maintenance, than other cells. However, the human counterpart of CAR cells has not been fully described. Here, we show the presence of cells expressing much higher CXCL12 than other cells in human adult bone marrow using a flow cytometry‐based in situ technique that enables high‐throughput detection of mRNA at single‐cell resolution. Most CXCL12^hi cells expressed high levels of SCF, FOXC1 and EBF3 and had the potential to differentiate into adipocytes and osteoblasts. Histologically, the nuclei of CXCL12^hi cells were identified and quantified by EBF3 expression in fixed marrow sections. CXCL12^hi cells sorted from residual bone marrow aspirates of chronic myeloid leukaemia patients expressed reduced levels of CXCL12, SCF, FOXC1 and EBF3 in correlation with increased leukaemic burden. Together, we identified the human counterpart of CAR cells, enabling the evaluation of their alterations in various haematological disorders by flow cytometric and histological analyses.

Aims: Follicular lymphoma (FL), comprising a minor subset of primary thyroid lymphomas, is divided into two groups based on Bcl‐2 expression and IGH‐BCL2 translocation. The clinicopathological features exhibited by Bcl‐2‐negative IGH‐BCL2 translocation‐negative FL of the thyroid (Bcl‐2^–/IGH‐BCL2^– tFL) are different from those of conventional FL; however, its lymphomagenesis remains unclear. Here, we collected samples from seven patients with Bcl‐2^–/IGH‐BCL2^– tFL to investigate their epigenetic and genetic aberrations.Methods and results: The immunohistochemical profiles of epigenetic modifiers and the methylation status of histones were examined, including EZH2, MLL2/KMT2D, CBP/CREBBP, EP300, H3K27me3 and H3K4me3, in Bcl‐2^–/IGH‐BCL2^– tFL and Bcl‐2‐positive IGH‐BCL2 translocation‐positive FL of the thyroid (Bcl‐2⁺/IGH‐BCL2⁺ tFL). Most Bcl‐2^–/IGH‐BCL2^– tFLs retained the positivity of epigenetic modifiers and lower expression of H3K27me3, although Bcl‐2⁺/IGH‐BCL2⁺ tFLs exhibited aberrant immunohistochemical patterns of EZH2 and CBP/CREBBP and overexpression of H3K27me3. Samples from seven cases were further analysed using targeted sequencing, focusing on the exons of 409 key tumour suppressor genes and oncogenes. Bcl‐2^–/IGH‐BCL2^– tFLs do not have pathogenic mutations of epigenetic modifiers, such as EZH2, MLL2/KMT2D, MLL3/KMT2C, EP300 and ARID1A, which have been reported in FLs in the literature, whereas Bcl‐2⁺/IGH‐BCL2⁺ tFLs are probably pathogenic/pathogenic missense mutations or frameshift mutations of these genes. Additionally, novel mutations in TET2 and EP400 were detected in Bcl‐2^–/IGH‐BCL2^– tFLs.Conclusions: Different genetic and epigenetic abnormalities might be involved in the oncogenesis of Bcl‐2^–/IGH‐BCL2^– tFLs from Bcl‐2⁺/IGH‐BCL2⁺ tFLs and other FLs.

Cancer-associated fibroblasts (CAFs) and tumor-associated macrophages (TAMs) in tumor stroma play a key role in disease progression. Recent studies using mice models suggest that CAFs are partly derived from bone marrow and TAMs primarily originate from bone marrow-derived inflammatory monocytes. However, the origin of these cells in humans remains unclear. Hence, we investigated their human origin, using specimens from human secondary tumors that developed after sex-mismatched bone marrow transplantation, by modified immunofluorescent in situ hybridization analysis and triple immunostaining. We observed that most of the α-smooth muscle actin (αSMA)-positive CAFs in the mammary gland, liver, and oral mucosa specimens obtained 3–19 years after bone marrow transplantation are recipient-derived cells. In contrast, the majority of the peritumoral αSMA-negative fibroblast-like cells are actually bone marrow-derived HLA-DR-positive myeloid cells, such as macrophages and dendritic cells. Furthermore, almost all CD163-positive TAMs and macrophages present in the non-tumor areas are derived from bone marrow.