Requirement for ssbp2 in hematopoietic stem cell maintenance and stress response

A minority of Th1 and Tfh effector cells express survival genes shared by memory cell progeny that require IL-7 or TCR signaling to persist

It is not clear how CD4+ memory T cells are formed from a much larger pool of earlier effector cells. We found that transient systemic bacterial infection rapidly generates several antigen-specific T helper (Th)1 and T follicular helper (Tfh) cell populations with different tissue residence behaviors. Although most cells of all varieties had transcriptomes indicative of cell stress and death at the peak of the response, some had already acquired a memory cell signature characterized by expression of genes involved in cell survival. Each Th1 and Tfh cell type was maintained long term by interleukin (IL)-7, except germinal center Tfh cells, which depended on a T cell antigen receptor (TCR) signal. The results indicate that acute infection induces rapid differentiation of Th1 and Tfh cells, a minority of which quickly adopt the gene expression profile of memory cells and survive by signals from the IL-7 receptor or TCR.

A time- and single-cell-resolved model of murine bone marrow hematopoiesis

The paradigmatic hematopoietic tree model is increasingly recognized to be limited, as it is based on heterogeneous populations largely defined by non-homeostatic assays testing cell fate potentials. Here, we combine persistent labeling with time-series single-cell RNA sequencing to build a real-time, quantitative model of in vivo tissue dynamics for murine bone marrow hematopoiesis. We couple cascading single-cell expression patterns with dynamic changes in differentiation and growth speeds. The resulting explicit linkage between molecular states and cellular behavior reveals widely varying self-renewal and differentiation properties across distinct lineages. Transplanted stem cells show strong acceleration of differentiation at specific stages of erythroid and neutrophil production, illustrating how the model can quantify the impact of perturbations. Our reconstruction of dynamic behavior from snapshot measurements is akin to how a kinetoscope allows sequential images to merge into a movie. We posit that this approach is generally applicable to understanding tissue-scale dynamics at high resolution.

Immunohistochemical Analysis of Single-Stranded DNA Binding Protein 2 in Non-Melanoma Skin Cancers

Single-stranded DNA binding protein 2 (SSBP2) is a tumor suppressor candidate. In this study, the expression level and clinicopathological significance of SSBP2 in squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) were evaluated. We also identified biological pathways associated with a set of genes potentially related to SSBP2. Immunohistochemistry (IHC) was performed on 70 SCC and 146 BCC cases to assess SSBP2 expression semi-quantitatively. In addition, the associations between SSBP2 expression and clinicopathological characteristics were analyzed. Gene ontology (GO) enrichment analysis was performed using publicly available data and web-based bioinformatics tools. Compared with BCC, SCC had a significantly low SSBP2 expression (p < 0.001). In total, 12 (17.1%) of the 70 SCC cases and 30 (20.5%) of the 146 BCC cases showed low SSBP2 expression. Among SCC cases, ulceration (p = 0.005) and a deep level of invasion (p = 0.012) showed an association with low SSBP2 expression. Local recurrence was slightly more common in the SCC subgroup with low SSBP2 expression, although the difference was not significant (p = 0.058). Using GO enrichment analysis, we identified several biological functions performed by a set of 36 genes in SCC. SSBP2 evaluation using IHC can be helpful in the differential diagnosis of SCC and BCC. SSBP2 expression was associated with tumor invasiveness in SCC.

Functions and regulatory mechanisms of resting hematopoietic stem cells: a promising targeted therapeutic strategy

Hematopoietic stem cells (HSCs) are the common and essential precursors of all blood cells, including immune cells, and they are responsible for the lifelong maintenance and damage repair of blood tissue homeostasis. The vast majority (> 95%) of HSCs are in a resting state under physiological conditions and are only activated to play a functional role under stress conditions. This resting state affects their long-term survival and is also closely related to the lifelong maintenance of hematopoietic function; however, abnormal changes may also be an important factor leading to the decline of immune function in the body and the occurrence of diseases in various systems. While the importance of resting HSCs has attracted increasing research attention, our current understanding of this topic remains insufficient, and the direction of clinical targeted treatments is unclear. Here, we describe the functions of HSCs, analyze the regulatory mechanisms that affect their resting state, and discuss the relationship between resting HSCs and different diseases, with a view to providing guidance for the future clinical implementation of related targeted treatments.

Improved memory CD8 T cell response to delayed vaccine boost is associated with a distinct molecular signature

Effective secondary response to antigen is a hallmark of immunological memory. However, the extent of memory CD8 T cell response to secondary boost varies at different times after a primary response. Considering the central role of memory CD8 T cells in long-lived protection against viral infections and tumors, a better understanding of the molecular mechanisms underlying the changing responsiveness of these cells to antigenic challenge would be beneficial. We examined here primed CD8 T cell response to boost in a BALB/c mouse model of intramuscular vaccination by priming with HIV-1 gag-encoding Chimpanzee adenovector, and boosting with HIV-1 gag-encoding Modified Vaccinia virus Ankara. We found that boost was more effective at day(d)100 than at d30 post-prime, as evaluated at d45 post-boost by multi-lymphoid organ assessment of gag-specific CD8 T cell frequency, CD62L-expression (as a guide to memory status) and in vivo killing. RNA-sequencing of splenic gag-primed CD8 T cells at d100 revealed a quiescent, but highly responsive signature, that trended toward a central memory (CD62L⁺) phenotype. Interestingly, gag-specific CD8 T cell frequency selectively diminished in the blood at d100, relative to the spleen, lymph nodes and bone marrow. These results open the possibility to modify prime/boost intervals to achieve an improved memory CD8 T cell secondary response.

Loss of Single-Stranded DNA Binding Protein 2 Expression Is Associated with Aggressiveness and Poor Overall Survival in Patients with Invasive Breast Carcinoma

Background: Single-stranded DNA binding protein 2 (SSBP2) is involved in the DNA damage response and the maintenance of genome stability. Previous studies have suggested that SSBP2 has a tumor suppressor function or oncogenic function. Loss of SSBP2 expression has been reported in various tumors. However, the role of SSBP2 expression in invasive breast carcinoma has not been reported. Methods: Immunohistochemical staining for SSBP2 was performed on tissue microarrays consisting of 491 invasive breast carcinoma cases. The result of nuclear SSBP2 staining was stratified as either negative or positive. Then, we investigated the correlations between SSBP2 expression and various clinicopathological parameters and patient outcomes. Results: Loss of nuclear SSBP2 expression was observed in 61 cases (12.4%) of 491 invasive breast carcinomas. Loss of nuclear SSBP2 expression was significantly correlated with larger tumor size (p < 0.001, chi-squared test), higher histological grade (p = 0.016, Cochran–Armitage trend test), higher pathological T stage (p < 0.001, Cochran–Armitage trend test), estrogen receptor status (p < 0.001, chi-squared test), and molecular subtype (p < 0.001, chi-squared test). Kaplan–Meier survival analysis revealed that patients with loss of nuclear SSBP2 expression had worse overall survival (p = 0.013, log-rank test). However, loss of nuclear SSBP2 expression was not correlated with recurrence-free survival (p = 0.175, log-rank test). Conclusions: Loss of nuclear SSBP2 expression was associated with adverse clinicopathological characteristics and poor patient outcomes. SSBP2 acts as a tumor suppressor in invasive breast carcinoma and may be used as a prognostic biomarker.

Structure and function of Pygo in organ development dependent and independent Wnt signalling

Pygo is a nuclear protein containing two conserved domains, NHD and PHD, which play important roles in embryonic development and carcinogenesis. Pygo was first identified as a core component of the Wnt/β-catenin signalling pathway. However, it has also been reported that the function of Pygo is not always Wnt/β-catenin signalling dependent. In this review, we summarise the functions of both domains of Pygo and show that their functions are synergetic. The PHD domain mainly combines with transcription co-factors, including histone 3 and Bcl9/9l. The NHD domain mainly recruits histone methyltransferase/acetyltransferase (HMT/HAT) to modify lysine 4 of the histone 3 tail (H3K4) and interacts with Chip/LIM-domain DNA-binding proteins (ChiLS) to form enhanceosomes to regulate transcriptional activity. Furthermore, we summarised chromatin modification differences of Pygo in Drosophila (dPygo) and vertebrates, and found that Pygo displayes a chromatin silencing function in Drosophila, while in vertebates, Pygo has a chromatin-activating function due to the two substitution of two amino acid residues. Next, we confirmed the relationship between Pygo and Bcl9/9l and found that Pygo-Bcl/9l are specifically partnered both in the nucleus and in the cytoplasm. Finally, we discuss whether transcriptional activity of Pygo is Wnt/β-catenin dependent during embryonic development. Available information indications that the transcriptional activity of Pygo in embryonic development is either Wnt/β-catenin dependent or independent in both tissue-specific and cell-specific-modes.

The loss of nuclear expression of single-stranded DNA binding protein 2 of gastric adenocarcinoma and its prognostic role: Analysis of molecular subtype

Single-stranded DNA binding protein 2 (SSBP2) is ubiquitously expressed, with several studies reporting it to be a tumor suppressor. We investigated SSBP2 expression and its clinicopathological significance in gastric cancer. SSBP2 expression was examined by immunohistochemistry in 539 gastric cancer sections. The cases were divided into three subtypes, namely, Epstein–Barr virus-associated (EBV), microsatellite unstable, and others (microsatellite stable and EBV negative), based on the molecular classification of The Cancer Genome Atlas (TCGA). Cases were also divided into two subgroups according to the amplification status of human epidermal growth factor receptor 2 (HER2). Most cases showed SSBP2 positivity, and only 24 (4.5%) cases displayed negative nuclear expression. Loss of nuclear expression correlated significantly with high pT category (P = 0.001), nodal metastasis (P = 0.002), and stage of progression (P = 0.005), with no correlation between molecular characteristics and SSBP2 expression. All HER2 amplification cases displayed positive SSBP2 expression. Negative SSBP2 cases showed significantly shorter recurrence-free survival (RFS) compared to positive SSBP2 cases (P = 0.008). Loss of nuclear expression of SSBP2 was significantly associated with shorter RFS in the microsatellite stable and EBV negative groups (P = 0.002), as well as the HER2 negative group (P = 0.007). However, there were no statistically significant differences in multivariate analyses. Loss of nuclear expression of SSBP2 was a poor prognostic factor, associated with stage of progression and recurrence, and showed no significant difference in molecular characteristics, including TCGA subtype and HER2 status.

Low Expression of Single-stranded DNA Binding Protein 2 (SSBP2) Predicts Unfavourable Postoperative Outcomes in Patients With Clear Cell Renal Cell Carcinoma

BACKGROUND

Single-stranded DNA binding protein 2 (SSBP2) is a subunit of a single-stranded DNA binding complex, which is involved in the maintenance of hematopoietic stem cells and stress responses. Numerous studies have suggested that SSBP2 functions as a tumor suppressor and is silenced through a pathway mediated by promoter hypermethylation. However, the role of SSBP2 in human renal cell carcinoma has not been reported, to date. Herein, we investigated the clinicopathological significance of SSBP2 expression in clear cell renal cell carcinoma (ccRCC).

MATERIALS AND METHODS

We constructed tissue micro arrays consisting of 173 ccRCC tissues, and SSBP2 expression was evaluated semi-quantitatively based on the staining intensity and the proportion of stained cells. Regarding statistical analysis, the tissues were divided into two groups according to SSBP2 expression, and correlation of SSBP2 expression with various clinicopathological characteristics and patient outcomes was evaluated.

RESULTS

Low SSBP2 expression was observed in 114 of 175 (65.9%) of ccRCC cases, and low SSBP2 expression was significantly correlated with larger tumor size (p=0.005, Chi-square test), higher WHO/ISUP histological grade (p<0.001, Chi-square test), tumor necrosis (p=0.008, Chi-square test), sarcomatoid change (p=0.021, Chi-square test), and higher pT AJCC stage (p=0.002, Chi-square test). Kaplan-Meier survival curves revealed that patients with low SSBP2 expression had worse recurrence-free survival (p=0.041, log-rank test).

CONCLUSION

ccRCC with low SSBP2 expression was associated with adverse clinicopathological characteristics and poor patient outcomes.

Rotational symmetry of the structured Chip/LDB-SSDP core module of the Wnt enhanceosome

The Chip/LIM-domain binding protein (LDB)-single-stranded DNA-binding protein (SSDP) (ChiLS) complex controls numerous cell-fate decisions in animal cells, by mediating transcription of developmental control genes via remote enhancers. ChiLS is recruited to these enhancers by lineage-specific LIM-domain proteins that bind to its Chip/LDB subunit. ChiLS recently emerged as the core module of the Wnt enhanceosome, a multiprotein complex that primes developmental control genes for timely Wnt responses. ChiLS binds to NPFxD motifs within Pygopus (Pygo) and the Osa/ARID1A subunit of the BAF chromatin remodeling complex, which could synergize with LIM proteins in tethering ChiLS to enhancers. Chip/LDB and SSDP both contain N-terminal dimerization domains that constitute the bulk of their structured cores. Here, we report the crystal structures of these dimerization domains, in part aided by DARPin chaperones. We conducted systematic surface scanning by structure-designed mutations, followed by in vitro and in vivo binding assays, to determine conserved surface residues required for binding between Chip/LDB, SSDP, and Pygo-NPFxD. Based on this, and on the 4:2 (SSDP-Chip/LDB) stoichiometry of ChiLS, we derive a highly constrained structural model for this complex, which adopts a rotationally symmetrical SSDP2-LDB2-SSDP2 architecture. Integrity of ChiLS is essential for Pygo binding, and our mutational analysis places the NPFxD pockets on either side of the Chip/LDB dimer, each flanked by an SSDP dimer. The symmetry and multivalency of ChiLS underpin its function as an enhancer module integrating Wnt signals with lineage-specific factors to operate context-dependent transcriptional switches that are pivotal for normal development and cancer.

Single-stranded DNA binding protein 2 expression is associated with patient survival in hepatocellular carcinoma

Background

SSBP2, single-stranded DNA binding protein 2, is a subunit of the ssDNA-binding complex that is involved in the maintenance of genome stability. The majority of previous studies have suggested a tumor-suppressive role of SSBP2, which is silenced by promoter hypermethylation in several human malignancies, such as hematologic malignancies, prostate cancer, esophageal squamous cell carcinoma, ovarian cancer, and gallbladder cancer. However, an oncogenic role of SSBP2 has been suggested in glioblastoma patients. We investigated the clinicopathologic significance of SSBP2 expression in hepatocellular carcinoma.

Methods

We constructed tissue microarrays consisting of 21 normal liver parenchyma and 213 hepatocellular carcinoma tissues with corresponding adjacent non-neoplastic tissues. SSBP2 expression was investigated by immunohistochemistry, and positive expression was defined as more than 10% of the tumor cells to show nuclear staining. We then analyzed the correlations between SSBP2 expression and various clinicopathologic characteristics, and further studied the role of SSBP2 in cell growth and migration.

Results

Hepatocytes were negative for SSBP2 immunohistochemistry in all normal liver samples, whereas the nuclei of normal bile duct epithelium and sinusoidal endothelium were immunoreactive. Positive immunoreactivity was found in one (0.6%) out of 180 non-neoplastic liver tissue samples adjacent to the tumor and in 16 (8.5%) out of 189 hepatocellular carcinomas. Positive SSBP2 expression was significantly correlated with tumor multifocality (P = 0.027, chi-square test), high histologic grade (P = 0.003, chi-square test), and frequent vascular invasion (P = 0.001, chi-square test). Kaplan-Meier survival curves revealed that patients with SSBP2 expression had poor prognosis in both disease-free and overall survival (P = 0.004 and P = 0.026, respectively, log-rank test). SSBP2-positive tumors also had a higher Ki-67 proliferation index (P <  0.001, t-test). Furthermore, downregulation of SSBP2 in the Huh7 cell line inhibited cell migration (P = 0.022, t-test) with altered expression of epithelial-mesenchymal transition markers.

Conclusions

The minority of hepatocellular carcinomas expressed SSBP2 by immunohistochemistry, whereas normal hepatocytes were negative. SSBP2-positive hepatocellular carcinomas were significantly associated with aggressive phenotypes and poor clinical outcome.

LIM-Only Protein 4 (LMO4) and LIM Domain Binding Protein 1 (LDB1) Promote Growth and Metastasis of Human Head and Neck Cancer (LMO4 and LDB1 in Head and Neck Cancer)

Squamous cell carcinoma of the head and neck (HNSCC) accounts for more than 300,000 deaths worldwide per year as a consequence of tumor cell invasion of adjacent structures or metastasis. LIM-only protein 4 (LMO4) and LIM-domain binding protein 1 (LDB1), two directly interacting transcriptional adaptors that have important roles in normal epithelial cell differentiation, have been associated with increased metastasis, decreased differentiation, and shortened survival in carcinoma of the breast. Here, we implicate two LDB1-binding proteins, single-stranded binding protein 2 (SSBP2) and 3 (SSBP3), in controlling LMO4 and LDB1 protein abundance in HNSCC and in regulating specific tumor cell functions in this disease. First, we found that the relative abundance of LMO4, LDB1, and the two SSBPs correlated very significantly in a panel of human HNSCC cell lines. Second, expression of these proteins in tumor primaries and lymph nodes involved by metastasis were concordant in 3 of 3 sets of tissue. Third, using a Matrigel invasion and organotypic reconstruct assay, CRISPR/Cas9-mediated deletion of LDB1 in the VU-SCC-1729 cell line, which is highly invasive of basement membrane and cellular monolayers, reduced tumor cell invasiveness and migration, as well as proliferation on tissue culture plastic. Finally, inactivation of the LDB1 gene in these cells decreased growth and vascularization of xenografted human tumor cells in vivo. These data show that LMO4, LDB1, and SSBP2 and/or SSBP3 regulate metastasis, proliferation, and angiogenesis in HNSCC and provide the first evidence that SSBPs control LMO4 and LDB1 protein abundance in a cancer context.

The Hematopoietic Stem and Progenitor Cell Cistrome: GATA Factor-Dependent cis-Regulatory Mechanisms

Transcriptional regulators mediate the genesis and function of the hematopoietic system by binding complex ensembles of cis-regulatory elements to establish genetic networks. While thousands to millions of any given cis-element resides in a genome, how transcriptional regulators select these sites and how site attributes dictate functional output is not well understood. An instructive system to address this problem involves the GATA family of transcription factors that control vital developmental and physiological processes and are linked to multiple human pathologies. Although GATA factors bind DNA motifs harboring the sequence GATA, only a very small subset of these abundant motifs are occupied in genomes. Mechanistic studies revealed a unique configuration of a GATA factor-regulated cis-element consisting of an E-box and a downstream GATA motif separated by a short DNA spacer. GATA-1- or GATA-2-containing multiprotein complexes at these composite elements control transcription of genes critical for hematopoietic stem cell emergence in the mammalian embryo, hematopoietic progenitor cell regulation, and erythroid cell maturation. Other constituents of the complex include the basic helix-loop-loop transcription factor Scl/TAL1, its heterodimeric partner E2A, and the Lim domain proteins LMO2 and LDB1. This chapter reviews the structure/function of E-box-GATA composite cis-elements, which collectively constitute an important sector of the hematopoietic stem and progenitor cell cistrome.

Clinical and biological significance of de novo CD5+ diffuse large B-cell lymphoma in Western countries

CD5 is a pan-T-cell surface marker and is rarely expressed in diffuse large B-cell lymphoma (DLBCL). Large-scale studies of de novo CD5+ DLBCL are lacking in Western countries. In this study by the DLBCL Rituximab-CHOP Consortium, CD5 was expressed in 5.5% of 879 DLBCL patients from Western countries. CD5+ DLBCL was associated with higher frequencies of >1 ECOG performance status, bone marrow involvement, central nervous system relapse, activated B-cell-like subtype, Bcl-2 overexpression, and STAT3 and NF-κB activation, whereas rarely expressed single-stranded DNA-binding protein 2 (SSBP2), CD30 or had MYC mutations. With standard R-CHOP chemotherapy, CD5+ DLBCL patients had significantly worse overall survival (median, 25.3 months vs. not reached, P< .0001) and progression-free survival (median, 21.3 vs. 85.8 months, P< .0001) than CD5- DLBCL patients, which was independent of Bcl-2, STAT3, NF-κB and the International Prognostic Index. Interestingly, SSBP2 expression abolished the prognostic significance of CD5 expression, suggesting a tumor-suppressor role of SSBP2 for CD5 signaling. Gene-expression profiling demonstrated that B-cell receptor signaling dysfunction and microenvironment alterations are the important mechanisms underlying the clinical impact of CD5 expression. This study shows the distinctive clinical and biological features of CD5+ DLBCL patients in Western countries and underscores important pathways with therapeutic implications.