Melanoma Cells Use Thy-1 (CD90) on Endothelial Cells for Metastasis Formation

Lung-specific metastasis: the coevolution of tumor cells and lung microenvironment

The vast majority of cancer-related deaths are attributed to metastasis. The lung, being a common site for cancer metastasis, is highly prone to being a target for multiple cancer types and causes a heavy disease burden. Accumulating evidence has demonstrated that tumor metastasis necessitates continuous interactions between tumor cells and distant metastatic niches. Nevertheless, a comprehensive elucidation of the underlying mechanisms governing lung-specific metastasis still poses a formidable challenge. In this review, we depict the lung susceptibility and the molecular profiles of tumors with the potential for lung metastasis. Under the conceptual framework of "Reciprocal Tumor-Lung Metastatic Symbiosis" (RTLMS), we mechanistically delineate the bidirectional regulatory dynamics and coevolutionary adaptation between tumor cells and distal pulmonary niches during lung-specific metastasis, including the induction of pre-metastatic-niches, positive responses of the lung, tumor colonization, dormancy, and reawakening. An enhanced understanding of the latest mechanisms is essential for developing targeted strategies to counteract lung-specific metastasis.

An acidic microenvironment promotes lymphatic metastasis of melanoma by Thy-1 in endothelial cells and integrin αvβ3 in tumor cells

Melanoma tissues exhibit an acidic microenvironment compared with that of surrounding normal tissues. However, the effects of acidic conditions on the lymphatic metastasis, a crucial prognostic factor for patients with melanoma, are unclear. In the present study, we aimed to investigate the role of the acidic microenvironment in the function of lymphatic endothelial cells. We first conducted gene expression profiling using human dermal lymphatic endothelial cells (HDLECs) treated with low pH media. Based on these results, we focused on Thy-1/CD90, whose expression increased in a time-dependent manner in HDLECs under acidic conditions. Immunohistochemical analysis of primary tumor tissues in a mouse melanoma model revealed an increased expression of Thy-1 in lymphatic endothelial cells. The expression of integrin αvβ3, a receptor for Thy-1, was also up-regulated in melanoma cells under acidic conditions. The adhesion of HDLECs to melanoma cells was accelerated under acidic conditions, which was reduced by Thy-1 knockdown in HDLECs. Furthermore, lymphatic metastasis was significantly attenuated in a mouse melanoma metastasis model when inoculated with integrin αv-silenced melanoma cells. These results suggest that acid-induced Thy-1 in lymphatic endothelial cells, as well as integrin αvβ3 in melanoma cells, may promote their mutual cellular adhesion, contributing to lymphatic metastasis.

B-1 derived anti-Thy-1 B cells in old aged mice develop lymphoma/leukemia with high expression of CD11b and Hamp2 that different from TCL1 transgenic mice

Human old aged unmutated chronic lymphocytic leukemia U-CLL are the TCL1+ZAP70+CD5+ B cells. Since CD5 makes the BCR signaling tolerance, ZAP70 increased in U-CLL not only TCL1+ alone. In mice, TCL1 (TCL1A) is the negative from neonate to old aged, as TC-. VH8-12/Vk21-5 is the anti-thymocyte/Thy-1 autoreactive ATA B cell. When ATA μκTg generation in mice, ATA B cells are the neonate generated CD5+ B cells in B-1, and in the middle age, CD5+ can be down or continuously CD5+, then, old aged CLL/lymphoma generation with increased CD11b in TC-ZAP70-CD5- or TC-ZAP70+CD5+. In this old aged TC-ATA B microarray analysis showed most similar to human CLL and U-CLL, and TC-ZAP70+CD5+ showed certain higher present as U-CLL. Original neonate ATA B cells showed with several genes down or further increase in old aged tumor, and old aged T-bet+CD11c+, CTNNB1hi, HMGBhi, CXCR4hi, DPP4hi and decreased miR181b. These old aged increased genes and down miR181b are similar to human CLL. Also, in old age ATA B cell tumor, high CD38++CD44++, increased Ki67+ AID+, and decreased CD180- miR15Olow are similar to U-CLL. In this old aged ATA B, increased TLR7,9 and Wnt10b. TC+Tg generated with ATAμκTg mice occurred middle age tumor as TC+ZAP70-CD5+ or TC+ZAP70+CD5+, with high NF-kB1, TLR4,6 and Wnt5b,6 without increased CD11b. Since neonatal state to age with TC+Tg continuously, middle age CLL/lymphoma generation is not similar to old aged generated, however, some increased in TC+ZAP70+ are similar to the old age TC- ATA B tumor. Then, TC- ATA B old age tumor showed some difference to human CLL. ATA B cells showed CD11b+CD22++, CD24 down, and hepcidin Hamp2++ with iron down. This mouse V8-12 similar to human V2-5, and V2-5 showed several cancers with macrophages/neutrophils generated hepcidin+ ironlow or some showed hepcidin- iron+ with tumor, and mouse V8-12 with different Vk19-17 generate MZ B cells strongly increased macrophage++ in old aged and generated intestine/colon tumor. Conclusion, neonate generated TC-ATA B1 cells in old aged tumor generation are CD11b+ in the leukemia CLL together with lymphoma cancer with hepcidin-related Hamp2++ in B-1 cell generation to control iron.

Thy-1 (CD90)-regulated cell adhesion and migration of mesenchymal cells: insights into adhesomes, mechanical forces, and signaling pathways

Cell adhesion and migration depend on the assembly and disassembly of adhesive structures known as focal adhesions. Cells adhere to the extracellular matrix (ECM) and form these structures via receptors, such as integrins and syndecans, which initiate signal transduction pathways that bridge the ECM to the cytoskeleton, thus governing adhesion and migration processes. Integrins bind to the ECM and soluble or cell surface ligands to form integrin adhesion complexes (IAC), whose composition depends on the cellular context and cell type. Proteomic analyses of these IACs led to the curation of the term adhesome, which is a complex molecular network containing hundreds of proteins involved in signaling, adhesion, and cell movement. One of the hallmarks of these IACs is to sense mechanical cues that arise due to ECM rigidity, as well as the tension exerted by cell-cell interactions, and transduce this force by modifying the actin cytoskeleton to regulate cell migration. Among the integrin/syndecan cell surface ligands, we have described Thy-1 (CD90), a GPI-anchored protein that possesses binding domains for each of these receptors and, upon engaging them, stimulates cell adhesion and migration. In this review, we examine what is currently known about adhesomes, revise how mechanical forces have changed our view on the regulation of cell migration, and, in this context, discuss how we have contributed to the understanding of signaling mechanisms that control cell adhesion and migration.

Pirin is a prognostic marker of human melanoma that dampens the proliferation of malignant cells by downregulating JARID1B/KDM5B expression

Originally considered to act as a transcriptional co-factor, Pirin has recently been reported to play a role in tumorigenesis and the malignant progression of many tumors. Here, we have analyzed the diagnostic and prognostic value of Pirin expression in the early stages of melanoma, and its role in the biology of melanocytic cells. Pirin expression was analyzed in a total of 314 melanoma biopsies, correlating this feature with the patient's clinical course. Moreover, PIR downregulated primary melanocytes were analyzed by RNA sequencing, and the data obtained were validated in human melanoma cell lines overexpressing PIR by functional assays. The immunohistochemistry multivariate analysis revealed that early melanomas with stronger Pirin expression were more than twice as likely to develop metastases during the follow-up. Transcriptome analysis of PIR downregulated melanocytes showed a dampening of genes involved in the G1/S transition, cell proliferation, and cell migration. In addition, an in silico approach predicted that JARID1B as a potential transcriptional regulator that lies between PIR and its downstream modulated genes, which was corroborated by co-transfection experiments and functional analysis. Together, the data obtained indicated that Pirin could be a useful marker for the metastatic progression of melanoma and that it participates in the proliferation of melanoma cells by regulating the slow-cycling JARID1B gene.

The GPI-Anchored Protein Thy-1/CD90 Promotes Wound Healing upon Injury to the Skin by Enhancing Skin Perfusion

Wound healing is a highly regulated multi-step process that involves a plethora of signals. Blood perfusion is crucial in wound healing and abnormalities in the formation of new blood vessels define the outcome of the wound healing process. Thy-1 has been implicated in angiogenesis and silencing of the Thy-1 gene retards the wound healing process. However, the role of Thy-1 in blood perfusion during wound closure remains unclear. We proposed that Thy-1 regulates vascular perfusion, affecting the healing rate in mouse skin. We analyzed the time of recovery, blood perfusion using Laser Speckle Contrast Imaging, and tissue morphology from images acquired with a Nanozoomer tissue scanner. The latter was assessed in a tissue sample taken with a biopsy punch on several days during the wound healing process. Results obtained with the Thy-1 knockout (Thy-1^−/−) mice were compared with control mice. Thy-1^−/− mice showed at day seven, a delayed re-epithelialization, increased micro- to macro-circulation ratio, and lower blood perfusion in the wound area. In addition, skin morphology displayed a flatter epidermis, fewer ridges, and almost no stratum granulosum or corneum, while the dermis was thicker, showing more fibroblasts and fewer lymphocytes. Our results suggest a critical role for Thy-1 in wound healing, particularly in vascular dynamics.

Evaluation of Soluble CD90: Potential for Diagnostic Significance in Endometriosis Patients

Background

Endometriosis is a chronic and debilitating gynecologic disorder, driven by endocrine and immune dysfunctions, which lead to poor endometrial differentiation and attenuated fertility. Escape from immune surveillance and involvement of inflammatory mechanisms appear to be factors in disease progression. Current diagnostic guidelines for endometriosis still lack an efficient biomarker. Here, we report a study on two previously unexplored factors as potential biomarkers for endometriosis.

Methods

A case-control study was performed to evaluate the diagnostic potential of serum CD90 and CD83 levels in endometriosis patients (cases validated by surgical and histological examination) compared to healthy controls. Serum was collected from age-matched females and analyzed by ELISA.

Results

Comparison of endometriosis patients to the control group showed significantly elevated levels of serum CD90 (1160 ± 856 pg/mL vs. 334 ± 228 pg/mL; ^∗∗∗∗p < 0.0001). A threshold value of 479.4 pg/mL was defined based on the control results, and the diagnostic efficiency of the test was estimated. The obtained sensitivity (70.4%), specificity (92.9%), positive predictive value (90.5%), and negative predictive value (76.5%) rated the test as one with promising diagnostic potential. In contrast, the analysis of serum CD83 levels showed comparable values in both groups, suggesting no association with patient status.

Conclusion

Elevated soluble CD90 in human serum is associated with endometriosis, which suggests its putative clinical significance as a biomarker in screening and/or diagnosis of the disease.

Thy-1-Integrin Interactions in cis and Trans Mediate Distinctive Signaling

Thy-1 is a cell surface glycosylphosphatidylinositol (GPI)-anchored glycoprotein that bears a broad mosaic of biological roles across various cell types. Thy-1 displays strong physiological and pathological implications in development, cancer, immunity, and tissue fibrosis. Quite uniquely, Thy-1 is capable of mediating integrin-related signaling through direct trans- and cis-interaction with integrins. Both interaction types have shown distinctive roles, even when interacting with the same type of integrin, where binding in trans or in cis often yields divergent signaling events. In this review, we will revisit recent progress and discoveries of Thy-1–integrin interactions in trans and in cis, highlight their pathophysiological consequences and explore other potential binding partners of Thy-1 within the integrin regulation/signaling paradigm.

CD34+THY1+ synovial fibroblast subset in arthritic joints has high osteoblastic and chondrogenic potentials in vitro

Objective

Synovial fibroblasts (SFs) in rheumatoid arthritis (RA) and osteoarthritis (OA) play biphasic roles in joint destruction and regeneration of bone/cartilage as mesenchymal stem cells (MSCs). Although MSCs contribute to joint homeostasis, such function is impaired in arthritic joints. We have identified functionally distinct three SF subsets characterized by the expression of CD34 and THY1 as follows: CD34⁺THY1⁺, CD34⁻THY1⁻, and CD34⁻THY1⁺. The objective of this study was to clarify the differentiation potentials as MSCs in each SF subset since both molecules would be associated with the MSC function.

Methods

SF subsets were isolated from synovial tissues of 70 patients (RA: 18, OA: 52). Expressions of surface markers associated with MSCs (THY1, CD34, CD73, CD271, CD54, CD44, and CD29) were evaluated in fleshly isolated SF subsets by flow cytometry. The differentiation potentials of osteogenesis, chondrogenesis, and adipogenesis were evaluated with histological staining and a quantitative polymerase chain reaction of differentiation marker genes. Small interfering RNA was examined to deplete THY1 in SFs.

Results

The expression levels of THY1⁺, CD73⁺, and CD271⁺ were highest and those of CD54⁺ and CD29⁺ were lowest in CD34⁺THY1⁺ among three subsets. Comparing three subsets, the calcified area, alkaline phosphatase (ALP)-stained area, and cartilage matrix subset were the largest in the CD34⁺THY1⁺ subset. Consistently, the expressions of differentiation markers of the osteoblasts (RUNX2, ALPL, and OCN) or chondrocytes (ACAN) were the highest in the CD34⁺THY1⁺ subset, indicating that the CD34⁺THY1⁺ subset possessed the highest osteogenic and chondrogenic potential among three subsets, while the differentiation potentials to adipocytes were comparable among the subsets regarding lipid droplet formations and the expression of LPL and PPARγ. The knockdown of THY1 in bulk SFs resulted in impaired osteoblast differentiation indicating some functional aspects in this stem-cell marker.

Conclusion

The CD34⁺THY1⁺ SF subset has high osteogenic and chondrogenic potentials. The preferential enhancement of MSC functions in the CD34⁺THY1⁺ subset may provide a new treatment strategy for regenerating damaged bone/cartilage in arthritic joints.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02736-7.

Phenotypic plasticity of melanocytes derived from human adult skin

We previously described a novel in vitro culture technique for dedifferentiated human adult skin melanocytes. Melanocytes cultured in a defined, cholera toxin and PMA free medium became bipolar, unpigmented, and highly proliferative. Furthermore, TRP-1 and c-Kit expression disappeared and EGFR receptor and nestin expression were induced in the cells. Here, we further characterized the phenotype of these dedifferentiated cells and by comparing them to mature pigmented melanocytes we detected crucial steps in their phenotype change. Our data suggest that normal adult melanocytes easily dedifferentiate into pluripotent stem cells given the right environment. This dedifferentiation process described here for normal melanocyte is very similar to what has been described for melanoma cells, indicating that phenotype switching driven by environmental factors is a general characteristic of melanocytes that can occur independent of malignant transformation.

MicroRNA-1301-3p promotes the progression of non-small cell lung cancer by targeting Thy-1 and predicts poor prognosis of patients

The role of microRNA (miR)-1301-3p has been investigated in breast cancer and colorectal cancer. Dysregulation of miR-1301-3p expression in non-small cell lung cancer (NSCLC) is speculated to be associated with tumor progression, which was systemically investigated in the present study. Reverse transcription-quantitative PCR analysis was performed to detect miR-1301-3p expression in 124 paired tissue samples and cultured cell lines. The results demonstrated that miR-1301-3p expression was regulated by transfection with miR-1301-3p mimic or inhibitor, and the proliferation, migration and invasion of the transfected cells were assessed via the Cell Counting Kit-8 and Transwell assays. In addition, miR-1301-3p expression was significantly upregulated in NSCLC tissues and cells compared with normal tissues and normal cells, respectively. Notably, upregulated miR-1301-3p expression in NSCLC tissues was significantly associated with the TNM stage, lymph node metastasis and poor prognosis of patients with NSCLC. Furthermore, upregulated miR-1301-3p expression in NSCLC cells promoted cell proliferation, migration and invasion, the effects of which were reversed following miR-1301-3p knockdown. Thy-1 was identified as a direct target of miR-1301-3p, which serves as a tumor promoter in the progression of NSCLC. Taken together, the results of the present study suggest that upregulated miR-1301-3p expression in NSCLC acts as an independent prognostic factor and a tumor promoter by targeting thy-1, thus provides a potential therapeutic target for NSCLC.

Thy-1 (CD90)-Induced Metastatic Cancer Cell Migration and Invasion Are β3 Integrin-Dependent and Involve a Ca2+/P2X7 Receptor Signaling Axis

Cancer cell adhesion to the vascular endothelium is an important step in tumor metastasis. Thy-1 (CD90), a cell adhesion molecule expressed in activated endothelial cells, has been implicated in melanoma metastasis by binding to integrins present in cancer cells. However, the signaling pathway(s) triggered by this Thy-1-Integrin interaction in cancer cells remains to be defined. Our previously reported data indicate that Ca²⁺-dependent hemichannel opening, as well as the P2X7 receptor, are key players in Thy-1-α_Vβ₃ Integrin-induced migration of reactive astrocytes. Thus, we investigated whether this signaling pathway is activated in MDA-MB-231 breast cancer cells and in B16F10 melanoma cells when stimulated with Thy-1. In both cancer cell types, Thy-1 induced a rapid increase in intracellular Ca²⁺, ATP release, as well as cell migration and invasion. Connexin and Pannexin inhibitors decreased cell migration, implicating a requirement for hemichannel opening in Thy-1-induced cell migration. In addition, cell migration and invasion were precluded when the P2X7 receptor was pharmacologically blocked. Moreover, the ability of breast cancer and melanoma cells to transmigrate through an activated endothelial monolayer was significantly decreased when the β₃ Integrin was silenced in these cancer cells. Importantly, melanoma cells with silenced β₃ Integrin were unable to metastasize to the lung in a preclinical mouse model. Thus, our results suggest that the Ca²⁺/hemichannel/ATP/P2X7 receptor-signaling axis triggered by the Thy-1-α_Vβ₃ Integrin interaction is important for cancer cell migration, invasion and transvasation. These findings open up the possibility of therapeutically targeting the Thy-1-Integrin signaling pathway to prevent metastasis.

Single-cell analysis reveals transcriptomic remodellings in distinct cell types that contribute to human prostate cancer progression

Prostate cancer shows remarkable clinical heterogeneity, which manifests in spatial and clonal genomic diversity. By contrast, the transcriptomic heterogeneity of prostate tumours is poorly understood. Here we have profiled the transcriptomes of 36,424 single cells from 13 prostate tumours and identified the epithelial cells underlying disease aggressiveness. The tumour microenvironment (TME) showed activation of multiple progression-associated transcriptomic programs. Notably, we observed promiscuous KLK3 expression and validated the ability of cancer cells in altering T-cell transcriptomes. Profiling of a primary tumour and two matched lymph nodes provided evidence that KLK3 ectopic expression is associated with micrometastases. Close cell-cell communication exists among cells. We identified an endothelial subset harbouring active communication (activated endothelial cells, aECs) with tumour cells. Together with sequencing of an additional 11 samples, we showed that aECs are enriched in castration-resistant prostate cancer and promote cancer cell invasion. Finally, we created a user-friendly web interface for users to explore the sequenced data.

Application of Force to a Syndecan-4 Containing Complex With Thy-1-αVβ3 Integrin Accelerates Neurite Retraction

Inflammation contributes to the genesis and progression of chronic diseases, such as cancer and neurodegeneration. Upregulation of integrins in astrocytes during inflammation induces neurite retraction by binding to the neuronal protein Thy-1, also known as CD90. Additionally, Thy-1 alters astrocyte contractility and movement by binding to the mechano-sensors α_Vβ₃ integrin and Syndecan-4. However, the contribution of Syndecan-4 to neurite shortening following Thy-1-α_Vβ₃ integrin interaction remains unknown. To further characterize the contribution of Syndecan-4 in Thy-1-dependent neurite outgrowth inhibition and neurite retraction, cell-based assays under pro-inflammatory conditions were performed. In addition, using Optical Tweezers, we studied single-molecule binding properties between these proteins, and their mechanical responses. Syndecan-4 increased the lifetime of Thy-1-α_Vβ₃ integrin binding by interacting directly with Thy-1 and forming a ternary complex (Thy-1-α_Vβ₃ integrin + Syndecan-4). Under in vitro-generated pro-inflammatory conditions, Syndecan-4 accelerated the effect of integrin-engaged Thy-1 by forming this ternary complex, leading to faster neurite retraction and the inhibition of neurite outgrowth. Thus, Syndecan-4 controls neurite cytoskeleton contractility by modulating α_Vβ₃ integrin mechano-receptor function. These results suggest that mechano-transduction, cell-matrix and cell-cell interactions are likely critical events in inflammation-related disease development.

Toward the Clinical Development and Validation of a Thy1-Targeted Ultrasound Contrast Agent for the Early Detection of Pancreatic Ductal Adenocarcinoma

Early detection of pancreatic ductal adenocarcinoma (PDAC) represents the most significant step toward the treatment of this aggressive lethal disease. Previously, we engineered a preclinical Thy1-targeted microbubble (MBThy1) contrast agent that specifically recognizes Thy1 antigen overexpressed in the vasculature of murine PDAC tissues by ultrasound (US) imaging. In this study, we adopted a single-chain variable fragment (scFv) site-specific bioconjugation approach to construct clinically translatable MBThy1-scFv and test for its efficacy in vivo in murine PDAC imaging, and functionally evaluated the binding specificity of scFv ligand to human Thy1 in patient PDAC tissues ex vivo.

MATERIALS AND METHODS

We recombinantly expressed the Thy1-scFv with a carboxy-terminus cysteine residue to facilitate its thioether conjugation to the PEGylated MBs presenting with maleimide functional groups. After the scFv-MB conjugations, we tested binding activity of the MBThy1-scFv to MS1 cells overexpressing human Thy1 (MS1Thy1) under liquid shear stress conditions in vitro using a flow chamber setup at 0.6 mL/min flow rate, corresponding to a wall shear stress rate of 100 seconds, similar to that in tumor capillaries. For in vivo Thy1 US molecular imaging, MBThy1-scFv was tested in the transgenic mouse model (C57BL/6J - Pdx1-Cre; KRas; Ink4a/Arf) of PDAC and in control mice (C57BL/6J) with L-arginine-induced pancreatitis or normal pancreas. To facilitate its clinical feasibility, we further produced Thy1-scFv without the bacterial fusion tags and confirmed its recognition of human Thy1 in cell lines by flow cytometry and in patient PDAC frozen tissue sections of different clinical grades by immunofluorescence staining.

RESULTS

Under shear stress flow conditions in vitro, MBThy1-scFv bound to MS1Thy1 cells at significantly higher numbers (3.0 ± 0.8 MB/cell; P < 0.01) compared with MBNontargeted (0.5 ± 0.5 MB/cell). In vivo, MBThy1-scFv (5.3 ± 1.9 arbitrary units [a.u.]) but not the MBNontargeted (1.2 ± 1.0 a.u.) produced high US molecular imaging signal (4.4-fold vs MBNontargeted; n = 8; P < 0.01) in the transgenic mice with spontaneous PDAC tumors (2-6 mm). Imaging signal from mice with L-arginine-induced pancreatitis (n = 8) or normal pancreas (n = 3) were not significantly different between the two MB constructs and were significantly lower than PDAC Thy1 molecular signal. Clinical-grade scFv conjugated to Alexa Fluor 647 dye recognized MS1Thy1 cells but not the parental wild-type cells as evaluated by flow cytometry. More importantly, scFv showed highly specific binding to VEGFR2-positive vasculature and fibroblast-like stromal components surrounding the ducts of human PDAC tissues as evaluated by confocal microscopy.

CONCLUSIONS

Our findings summarize the development and validation of a clinically relevant Thy1-targeted US contrast agent for the early detection of human PDAC by US molecular imaging.

RKIP Regulates Differentiation-Related Features in Melanocytic Cells

Raf Kinase Inhibitor Protein (RKIP) has been extensively reported as an inhibitor of key signaling pathways involved in the aggressive tumor phenotype and shows decreased expression in several types of cancers. However, little is known about RKIP in melanoma or regarding its function in normal cells. We examined the role of RKIP in both primary melanocytes and malignant melanoma cells and evaluated its diagnostic and prognostic value. IHC analysis revealed a significantly higher expression of RKIP in nevi compared with early-stage (stage I–II, AJCC 8th) melanoma biopsies. Proliferation, wound healing, and collagen-coated transwell assays uncovered the implication of RKIP on the motility but not on the proliferative capacity of melanoma cells as RKIP protein levels were inversely correlated with the migration capacity of both primary and metastatic melanoma cells but did not alter other parameters. As shown by RNA sequencing, endogenous RKIP knockdown in primary melanocytes triggered the deregulation of cellular differentiation-related processes, including genes (i.e., ZEB1, THY-1) closely related to the EMT. Interestingly, NANOG was identified as a putative transcriptional regulator of many of the deregulated genes, and RKIP was able to decrease the activation of the NANOG promoter. As a whole, our data support the utility of RKIP as a diagnostic marker for early-stage melanomas. In addition, these findings indicate its participation in the maintenance of a differentiated state of melanocytic cells by modulating genes intimately linked to the cellular motility and explain the progressive decrease of RKIP often described in tumors.

The multiple roles of Thy-1 in cell differentiation and regeneration

Thy-1 is a 25-37 kDa glycophosphatidylinositol (GPI)-anchored cell surface protein that was discovered more than 50 years ago. Recent findings have suggested that Thy-1 is expressed on thymocytes, mesenchymal stem cells (MSCs), cancer stem cells, hematopoietic stem cells, fibroblasts, myofibroblasts, endothelial cells, neuronal smooth muscle cells, and pan T cells. Thy-1 plays vital roles in cell migration, adhesion, differentiation, transdifferentiation, apoptosis, mechanotransduction, and cell division, which in turn are involved in tumor development, pulmonary fibrosis, neurite outgrowth, and T cell activation. Studies have increasingly indicated a significant role of Thy-1 in cell differentiation and regeneration. However, despite recent research, many questions remain regarding the roles of Thy-1 in cell differentiation and regeneration. This review aimed to summarize the roles of Thy-1 in cell differentiation and regeneration. Furthermore, since Thy-1 is an outer leaflet membrane protein anchored by GPI, we attempted to address how Thy-1 regulates intracellular pathways through cis and trans signals. Due to the complexity and mystery surrounding the issue, we also summarized the Thy-1-related pathways in different biological processes, and this might provide novel insights in the field of cell differentiation and regeneration.

Tumor infiltrating lymphocytes in malignant melanoma - allies or foes?

This is an overview of current problematics regarding the role of tumor infiltrating lymphocytes (TILs) in malignant melanomas. Various and often conflicting data have been published, correlating tumor type, stage, prognosis, as well as sex and age of patients. This is partly due to heterogeneity in scaling systems and unstandardized TILs grading but also due to changes of tumor-host interactions. Melanomas are an immunologically heterogeneous group with variability of TILs, where distinct gene expression patterns were found in tumors with absent, and/or non- brisk TIL grade versus brisk TIL grade. However, the presence of TILs alone appears to be inadequate for implicating them as immunologically functional. Further characterisation of TIL phenotype and function is warranted. This especially concerns, evaluation of TILs of the suppressor phenotype but rather than as a prognostic factor, more for prediction of targeted immunotherapy.

Melanoma-Derived Exosomes Induce PD-1 Overexpression and Tumor Progression via Mesenchymal Stem Cell Oncogenic Reprogramming

Recently, it has been described that programmed cell death protein 1 (PD-1) overexpressing melanoma cells are highly aggressive. However, until now it has not been defined which factors lead to the generation of PD-1 overexpressing subpopulations. Here, we present that melanoma-derived exosomes, conveying oncogenic molecular reprogramming, induce the formation of a melanoma-like, PD-1 overexpressing cell population (mMSCPD-1+) from naïve mesenchymal stem cells (MSCs). Exosomes and mMSCPD-1+ cells induce tumor progression and expression of oncogenic factors in vivo. Finally, we revealed a characteristic, tumorigenic signaling network combining the upregulated molecules (e.g., PD-1, MET, RAF1, BCL2, MTOR) and their upstream exosomal regulating proteins and miRNAs. Our study highlights the complexity of exosomal communication during tumor progression and contributes to the detailed understanding of metastatic processes.

Thy-1 in Integrin Mediated Mechanotransduction

The glycosylphosphatidylinositol (GPI) anchored glycoprotein Thy-1 has been prevalently expressed on the surface of various cell types. The biological function of Thy-1 ranges from T cell activation, cell adhesion, neurite growth, differentiation, metastasis and fibrogenesis and has been extensively reviewed elsewhere. However, current discoveries implicate Thy-1 also functions as a key mechanotransduction mediator. In this review, we will be focusing on the role of Thy-1 in translating extracellular mechanic cues into intracellular biological cascades. The mechanotransduction capability of Thy-1 relies on trans and cis interaction between Thy-1 and RGD-binding integrins; and will be discussed in depth in the review.

The expressions of HMGA2 and Thy1 in extrahepatic cholangiocarcinoma and their clinicopathological significances

AIMS

Extrahepatic cholangiocarcinoma is a malignant tumor and poor prognosis with intrinsic resistance to cytotoxic agents. The molecular mechanism associated with high malignancy and resistance to chemotherapy and radiotherapy has not been fully elucidated. This study aims to investigate the clinicopathological significances of HMGA2 and Thy1 expression in extrahepatic cholangiocarcinoma.

METHODS

The expressions of HMGA2 and Thy1 in 100 extrahepatic cholangiocarcinoma, 30 peritumoral tissues, 10 adenoma and 15 normal biliary tract tissues were assayed using EnVision immunohistochemistry.

RESULTS

The HMGA2 and Thy1 proteins were overexpression in extrahepatic cholangiocarcinoma compared to peritumoral tissues, adenoma, and normal biliary tract tissues (P < 0.05 or P < 0.01). Adenoma and pericancerous tissues with positive HMGA2 or/and Thy1 protein expression exhibited atypical hyperplasia. The positive correlation was found between the expression of HMGA2 and Thy1 in extrahepatic cholangiocarcinoma (P < 0.01). The positive rates of HMGA2 and Thy1 expression were significantly higher in cases with poor differentiation, lymph node metastasis, invasion, and TNM stage III or IV and no resection (biopsy only) (P < 0.05 or P < 0.01). Kaplan-Meier survival analysis showed that the survival of extrahepatic cholangiocarcinoma patients with positive HMGA2 and/or Thy1 expression is significantly shorter than patients with negative HMGA2 and/or Thy1 expression (P = 0.000). Cox multivariate analysis revealed that positive HMGA2 and/or Thy1 expressions were independently poor prognosis factors in extrahepatic cholangiocarcinoma patients. We calculated the AUC for HMGA2 (AUC = 0.610, 95%CI: 0.519-0.702), or Thy1 (AUC = 0.675, 95%CI: 0.588-0.762), respectively.

CONCLUSIONS

The present study indicated that positive HMGA2 and Thy1 expression are closely associated with the pathogenesis, clinical, pathological and biological behaviors, and poor prognosis in patients with extrahepatic cholangiocarcinoma.

Stromal CD38 regulates outgrowth of primary melanoma and generation of spontaneous metastasis

The outgrowth of primary melanoma, the deadliest skin cancer, and generation of metastasis is supported by the tumor microenvironment (TME) which includes non-cancerous cells. Since the TME plays an important role in melanoma pathogenesis, its targeting is a promising therapeutic approach. Thus, it is important to identify proteins in the melanoma TME that may serve as therapeutic targets. Here we show that the nicotinamide adenine dinucleotide glycohydrolase CD38 is a suitable target for this purpose. Loss of CD38 in the TME as well as inhibition of its enzymatic activity restrained outgrowth of primary melanoma generated by two transplantable models of melanoma, B16F10 and Ret-mCherry-sorted (RMS) melanoma cells. Pathological analysis indicated that loss of CD38 increased cell death and reduced the amount of cancer-associated fibroblasts (CAFs) and blood vessels. Importantly, in addition to inhibiting outgrowth of primary melanoma tumors, loss of CD38 also inhibited spontaneous occurrence of RMS pulmonary and brain metastasis. The underlying mechanism may involve, at least in the brain, inhibition of metastasis expansion, since loss of CD38 inhibited the outgrowth of B16F10 and RMS brain tumors that were generated by direct intracranial implantation. Collectively, our results suggest that targeting CD38 in the melanoma TME provides a new therapeutic approach for melanoma treatment.

Targeting αvβ3 and αvβ5 integrins inhibits pulmonary metastasis in an intratibial xenograft osteosarcoma mouse model

Osteosarcoma is an aggressive bone cancer that has a high propensity for metastasis to the lungs. Patients with metastatic disease face a very poor prognosis. Therefore, novel therapeutics, efficiently suppressing the metastatic process, are urgently needed. Integrins play a pivotal role in tumor cell adhesion, motility and metastasis. Here, we evaluated αvβ3 and αvβ5 integrin inhibition with cilengitide as a novel metastasis-suppressive therapeutic approach in osteosarcoma. Immunohistochemical analysis of αvβ3 and αvβ5 integrins expression in a tissue microarray of tumor specimens collected from osteosarcoma patients revealed that αvβ5 integrin is mainly found on tumor cells, whereas αvβ3 is predominantly expressed by stromal cells. In vitro functional assays demonstrated that cilengitide dose-dependently inhibited de novo adhesion, provoked detachment and inhibited migration of osteosarcoma cell lines. Cilengitide induced a decline in cell viability, blocked the cell cycle in the G1 phase and caused anoikis by activation of the Hippo pathway. In a xenograft orthotopic mouse model cilengitide minimally affected intratibial primary tumor growth but, importantly, suppressed pulmonary metastasis. The data demonstrate that targeting αvβ3 and αvβ5 integrins in osteosarcoma should be considered as a novel therapeutic option for patients with metastatic disease.

Cancer stem cell marker CD90 inhibits ovarian cancer formation via β3 integrin

Cancer stem cell (CSC) markers have been identified for CSC isolation and proposed as therapeutic targets in various types of cancers. CD90, one of the characterized markers in liver and gastric cancer, is shown to promote cancer formation. However, the underexpression level of CD90 in ovarian cancer cells and the evidence supporting the cellular mechanism have not been investigated. In the present study, we found that the DNA copy number of CD90 is correlated with mRNA expression in ovarian cancer tissue and the ovarian cancer patients with higher CD90 have good prognosis compared to the patients with lower CD90. Although the expression of CD90 in human ovarian cancer SKOV3 cells enhances the cell proliferation by MTT and anchorage-dependent growth assay, CD90 inhibits the anchorage-independent growth ability in vitro and tumor formation in vivo. CD90 overexpression suppresses the sphere-forming ability and ALDH activity and enhances the cell apoptosis, indicating that CD90 may reduce the cell growth by the properties of CSC and anoikis. Furthermore, CD90 reduces the expression of other CSC markers, including CD133 and CD24. The inhibition of CD133 is attenuated by the mutant CD90, which is replaced with RLE domain into RLD domain. Importantly, the CD90-regulated inhibition of CD133 expression, anchorage-independent growth and signal transduction of mTOR and AMPK are restored by the β3 integrin shRNA. Our results provide evidence that CD90 mediates the antitumor formation by interacting with β3 integrin, which provides new insight that can potentially be applied in the development of therapeutic strategies in ovarian cancer.

Extracellular S100A4 affects endothelial cell integrity and stimulates transmigration of A375 melanoma cells

High extracellular S100A4 level proves a specific characteristic of some cancer cases, including malignant melanoma. Concerning the latter, extracellular S100A4 in an autocrine manner was shown to promote prometastatic activation of A375 cells by interaction with the receptor for advanced glycation endproducts (RAGE). We hypothesized that interaction of extracellular S100A4 with RAGE in a paracrine manner will affect endothelial cell (EC) integrity thus further promoting melanoma metastasis. We investigated the influence of recombinant and cell (A375)-derived S100A4 on junction protein expression and EC (hCMEC/D3) integrity by measuring transendothelial electrical resistance (TEER). Decrease of TEER and diminished expression of both occludin and VE-cadherin revealed the loss of EC integrity. Transmigration of transgenic A375 cells (A375-hS100A4/A375-hRAGE) through the EC monolayer was significantly higher compared to wild-type A375 cells, and was substantially decreased by sRAGE. A pilot study in mice, intracardially injected with A375-hS100A4 or A375-hRAGE cells, showed lower survival rates and a higher incidence of metastases compared to wild-type A375 cells. Tumor development was mostly located in the brain, bones, and ovaries. These findings provide further evidence on extracellular S100A4 as paracrine mediator of prometastatic endothelial dysfunction involving its interaction with RAGE.

The clinical pathological significance of Thy1 and CD49f expression in chondrosarcomas

OBJECTIVE

This study investigated the protein expression and clinicopathological significance of Thy1 and CD49f in chondrosarcomas.

METHODS

Thy1 and CD49f protein expression in 59 chondrosarcomas and 33 osteochondromas were measured by immunohistochemical staining.

RESULTS

The percentage of positive Thy1 and CD49f expression was significantly higher in patients with chondrosarcoma than in patients with osteochondroma (P<0.01). The percentage of positive Thy1 and CD49f expression was significantly lower in patients with histological grade I, Enneking stage I, AJCC stage I/II stage, non-metastatic and non-invasive chondrosarcoma than in patients with histological grade III, Enneking stage II+III, AJCC stage III/IV, metastatic and invasive chondrosarcoma (P<0.05 or P<0.01). Thy1 expression was positively correlated with CD49f expression in chondrosarcoma. Kaplan-Meier survival analysis showed that histological grade, AJCC stage, Enneking stage, metastasis, invasion, and Thy1 and CD49f expression significantly correlated with shorter mean survival time in chondrosarcoma patients (P<0.05 or P<0.01). Cox multivariate analysis showed that positive Thy1 and CD49f expression was an independent prognostic factor that negatively correlated with overall postoperative survival.

CONCLUSION

Positive Thy1 and CD49f expression is significantly associated with the progression and poor prognosis of chondrosarcoma.

Gene expression analyses of primary melanomas reveal CTHRC1 as an important player in melanoma progression

Melanoma is notorious for its high tendency to metastasize and its refractoriness to conventional treatments after metastasis, and the responses to most targeted therapies are short-lived. A better understanding of the molecular mechanisms behind melanoma development and progression is needed to develop more effective therapies and to identify new markers to predict disease behavior. Here, we compared the gene expression profiles of benign nevi, and non-metastatic and metastatic primary melanomas to identify any common changes in disease progression. We identified several genes associated with inflammation, angiogenesis, and extracellular matrix modification to be upregulated in metastatic melanomas. We selected one of these genes, collagen triple helix repeat containing 1 (CTHRC1), for detailed analysis, and found that CTHRC1 was expressed in both melanoma cells and the associated fibroblasts, as well as in the endothelium of tumor blood vessels. Knockdown of CTHRC1 expression by shRNAs in melanoma cells inhibited their migration in Transwell assays and their invasion in three-dimensional collagen and Matrigel matrices. We also elucidated the possible down-stream effectors of CTHRC1 by gene expression profiling of the CTHRC1-knockdown cells. Our analyses showed that CTHRC1 is regulated coordinately with fibronectin and integrin β3 by the pro-invasive and -angiogenic transcription factor NFATC2. We also found CTHRC1 to be a target of TFGβ and BRAF. These data highlight the importance of tumor stroma in melanoma progression. Furthermore, CTHRC1 was recognized as an important mediator of melanoma cell migration and invasion, providing together with its regulators-NFATC2, TGFβ, and BRAF-attractive therapeutic targets against metastatic melanomas.

Heparan Sulfate Proteoglycans May Promote or Inhibit Cancer Progression by Interacting with Integrins and Affecting Cell Migration

The metastatic disease is one of the main consequences of tumor progression, being responsible for most cancer-related deaths worldwide. This review intends to present and discuss data on the relationship between integrins and heparan sulfate proteoglycans in health and cancer progression. Integrins are a family of cell surface transmembrane receptors, responsible for cell-matrix and cell-cell adhesion. Integrins' main functions include cell adhesion, migration, and survival. Heparan sulfate proteoglycans (HSPGs) are cell surface molecules that play important roles as cell receptors, cofactors, and overall direct or indirect contributors to cell organization. Both molecules can act in conjunction to modulate cell behavior and affect malignancy. In this review, we will discuss the different contexts in which various integrins, such as α5, αV, β1, and β3, interact with HSPGs species, such as syndecans and perlecans, affecting tissue homeostasis.

CD90 is upregulated in gastric cancer tissues and inhibits gastric cancer cell apoptosis by modulating the expression level of SPARC protein

Cluster of differentiation 90 (CD90) (Thy-1) plays important roles in the oncogenesis in various types of malignancies. In the present study, we investigated the expression of CD90 in gastric cancer (GC) tissues by q-PCR, immunohistochemistry (IHC), and western blot technologies. The results showed that CD90 was overexpressed in gastric cancer tissues compared with the level in the adjacent non‑cancerous tissues. To explore the possible mechanism of CD90 in GC, we elucidated the effect of CD90 on the apoptosis of AGS gastric cancer cells, and found that a considerable decrease in apoptotic cells was observed for AGS cells with CD90 overexpression. Meanwhile, the rate of apoptotic cells was increased in the AGS cells with CD90 interference (siCD90) compared with that in the AGS cells. Cell apoptosis is closely related to a reduction in mitochondrial membrane potential (ΔΨm) and an increase in intracellular reactive oxygen species (ROS) and calcium ion (Ca2+) concentrations. Our results showed that overexpression of CD90 in the AGS gastric cancer cells led to an increase in ΔΨm and a decrease in intracellular ROS and Ca2+ concentrations. At the same time, siCD90 reduced ΔΨm and the increase in intracellular ROS and Ca2+ concentrations. Furthermore, we identified and confirmed that CD90 functions by modulating the expression level of secreted protein, acidic, cysteine‑rich (osteonectin) (SPARC) in vitro through LC‑MS/MS analyses and western blot technology. In summary, our results suggest that CD90 is upregulated in gastric cancer and inhibits gastric cancer cell apoptosis by modulating the expression level of SPARC protein.

The changes of angiogenesis and immune cell infiltration in the intra- and peri-tumoral melanoma microenvironment

Malignant melanoma (MM) urgently needs identification of new markers with better predictive value than currently-used clinical and histological parameters. Cancer cells stimulate the formation of a specialized tumor microenvironment, which reciprocally affects uncontrolled proliferation and migration. However, this microenvironment is heterogeneous with different sub-compartments defined by their access to oxygen and nutrients. This study evaluated microvascular density (MVD), CD3+ lymphocytes (TILs) and FOXP3+ T-regulatory lymphocytes (Tregs) on formalin-fixed paraffin-embedded tissue sections using light microscopy. We analyzed 82 malignant melanomas, divided according to the AJCC TNM classification into four groups--pT1 (35), pT2 (17), pT3 (18) and pT4 (12)--and 25 benign pigmented nevi. All parameters were measured in both the central areas of tumors (C) and at their periphery (P). A marked increase in all parameters was found in melanomas compared to nevi (p = 0.0001). There was a positive correlation between MVD, TILs, FOXP3+ Tregs and the vertical growth phase. The results show that MVD, TILs and FOXP3+ Tregs substantially influence cutaneous melanoma microenvironment. We found significant topographic differences of the parameters between central areas of tumors and their boundaries.

Overexpression of CD90 (Thy-1) in pancreatic adenocarcinoma present in the tumor microenvironment

CD90 (Thy-1) plays important roles in oncogenesis and shows potential as a candidate marker for cancer stem cells (CSCs) in various malignancies. Herein, we investigated the expression of CD90 in pancreatic adenocarcinoma (PDAC), with a comparison to normal pancreas and non-malignant pancreatic disease, by immunohistochemical (IHC) analysis of tissue microarrays containing 183 clinical tissue specimens. Statistical analysis was performed to evaluate the correlation between CD90 expression and the major clinicopathological factors after adjustment of age and gender. The IHC data showed that CD90 was significantly overexpressed in PDAC and its metastatic cancers as compared to chronic pancreatitis and benign islet tumors, while it was negative in normal pancreas and 82.7% of adjacent normal pancreas tissues. The abundant CD90 expression was predominantly present in PDAC stroma, such as fibroblasts and vascular endothelial cells, which could serve as a promising marker to distinguish pancreatic adenocarcinoma from normal pancreas and non-malignant pancreatic diseases. Double immunostaining of CD90 with CD24, a CSC marker for PDAC, showed that there was little overlap between these two markers. However, CD90+ fibroblast cells were clustered around CD24+ malignant ducts, suggesting that CD90 may be involved in the tumor-stroma interactions and promote pancreatic cancer development. Furthermore, CD90 mostly overlapped with α-smooth muscle actin (αSMA, a marker of activated pancreatic stellate cells (PSCs)) in PDAC stroma, which demonstrated that CD90+ stromal cells consist largely of activated PSCs. Double immunostaining of CD90 and a vascular endothelial cell marker CD31 demonstrated that CD90 expression on vascular endothelial cells was significantly increased in PDACs as compared to normal pancreas and non-malignant pancreatic diseases. Our findings suggest that CD90 could serve as a promising marker for pancreatic adenocarcinoma where desmoplastic stroma plays an important role in tumor growth and angiogenesis.

Besides neuro-imaging, the Thy1-YFP mouse could serve for visualizing experimental tumours, inflammation and wound-healing

The B6.Cg-Tg(Thy1-YFP)16Jrs/J transgenic mouse strain, widely used to study neuronal development and regeneration, expresses the yellow fluorescent protein (YFP) in the peripheral nerves and the central nervous system under the control of regulatory sequences of the Thy1 gene. The Thy1 (CD90) cell surface glycoprotein is present on many cell types besides neurons, and is known to be involved in cell adhesion, migration and signal transduction. We hypothesized that Thy1-activating conditions could probably activate the truncated Thy1 regulatory sequences used in the Thy1-YFP construct, resulting in YFP transgene expression outside the nervous system. We demonstrated that the stroma of subcutaneous tumours induced by the injection of 4T1 or MC26 carcinoma cells into BALB/c(Thy1-YFP) mice, carrying the same construct, indeed expressed the YFP transgene. In the tumour mass, the yellow-green fluorescent stromal cells were clearly distinguishable from 4T1 carcinoma cells stably transfected with red fluorescent protein. Local inflammation induced by subcutaneous injection of complete Freund's adjuvant, as well as the experimental wound-healing milieu, also triggered YFP fluorescence in both the BALB/c(Thy1-YFP) and B6.Cg-Tg(Thy1-YFP)16Jrs/J mice, pointing to eventual overlapping pathways of wound-healing, inflammation and tumour growth.

Neuronal NAMPT is released after cerebral ischemia and protects against white matter injury

Nicotinamide phosphoribosyltransferase (NAMPT) has been implicated in neuroprotection against ischemic brain injury, but the mechanism underlying its protective effect remains largely unknown. To further examine the protective effect of NAMPT against ischemic stroke and its potential mechanism of action, we generated a novel neuron-specific NAMPT transgenic mouse line. Transgenic mice and wild-type littermates were subjected to transient occlusion of the middle cerebral artery (MCAO) for 60 minutes. Neuron-specific NAMPT overexpression significantly reduced infarct volume by 65% (P=0.018) and improved long-term neurologic outcomes (P≤0.05) compared with littermates. Interestingly, neuronal overexpression of NAMPT increased the area of myelinated fibers in the striatum and corpus callosum, indicating that NAMPT protects against white matter injury. The mechanism of protection appeared to be through extracellular release of NAMPT. First, NAMPT was secreted into the extracellular medium by primary cortical neurons exposed to ischemia-like oxygen-glucose deprivation (OGD) in vitro. Second, conditioned medium from NAMPT-overexpressing neurons exposed to OGD protected cultured oligodendrocytes from OGD. Third, the protective effects of conditioned medium were abolished by antibody-mediated NAMPT depletion, strongly suggesting that the protective effect is mediated by the extracellular NAMPT released into in the medium. These data suggest a novel neuroprotective role for secreted NAMPT in the protection of white matter after ischemic injury.

Genomewide RNAi screen identifies protein kinase Cb and new members of mitogen-activated protein kinase pathway as regulators of melanoma cell growth and metastasis

A large-scale RNAi screen was performed for eight different melanoma cell lines using a pooled whole-genome lentiviral shRNA library. shRNAs affecting proliferation of transduced melanoma cells were negatively selected during 10 days of culture. Overall, 617 shRNAs were identified by microarray hybridization. Pathway analyses identified mitogen-activated protein kinase (MAPK) pathway members such as ERK1/2, JNK1/2 and MAP3K7 and protein kinase C β (PKCβ) as candidate genes. Knockdown of PKCβ most consistently reduced cellular proliferation, colony formation and migratory capacity of melanoma cells and was selected for further validation. PKCβ showed enhanced expression in human primary melanomas and distant metastases as compared with benign melanocytic nevi. Moreover, treatment of melanoma cells with PKCβ-specific inhibitor enzastaurin reduced melanoma cell growth but had only small effects on benign fibroblasts. Finally, PKCβ-shRNA significantly reduced lung colonization capacity of stably transduced melanoma cells in mice. Taken together, this study identified new candidate genes for melanoma cell growth and proliferation. PKCβ seems to play an important role in these processes and might serve as a new target for the treatment of metastatic melanoma.

Heterogeneity of The CD90+ Population in Different Stages of Hepatocarcinogenesis

We have characterized herein the heterogeneity of the CD90⁺ population at each stage of hepatocarcinogenesis using a computer-assisted immunohistochemical staining evaluation method for quantitative analysis on tissue microarrays. We found that CD90 in Hepatocellular carcinoma (HCC) tissues, which has been shown to be a marker for cancer stem cells, is expressed on tumor cells, in the stroma or on endothelial cells. Sub-classification of the CD90⁺ population was based on morphology and co-expression with known markers including CD45 and CD31. Multiple linear regression suggested that the percentage of CD90⁺ cancer cells/hepatocyte (p<0.0001), level of overall CD90 expression (p<0.0014), and level of CD90 expression in tumor islands (p<0.0001) increased significantly in each stage of liver disease progression, while the level of stromal CD90 expression (p=0.1129) did not change significantly. Additionally, only the CD90⁺ cancer cells were positive for other cancer stem cell (CSC) markers including CD24, CD44 and CD133 whereas the other CD90⁺ cells were negative for these markers. CD90 expression in cirrhosis was observed in hepatocytes, the portal tract area and fibrous septa while CD90 expression in normal liver was limited only to the portal tract area. This study demonstrates the heterogeneity of the CD90⁺ population in HCC where a small population of the CD90+ cells that expressed other CSC markers are CSCs and are associated with advanced stages of hepatocarcinogenesis. This heterogeneity should be emphasized in further studies where other methods may not be able to discriminate these distinct types of CD90⁺ cells.

On the notion of doll's eyes

CD90 is a membrane GPI-anchored protein with one Ig V-type superfamily domain that was initially described in mouse T cells. Besides the specific expression pattern and functions of CD90 that were described in normal tissues, i.e., neurons, fibroblasts and T cells, increasing evidences are currently highlighting the possible involvement of CD90 in cancer. This review first provides a brief overview on CD90 gene, mRNA and protein features and then describes the established links between CD90 and cancer. Finally, we report newly uncovered functional connections between CD90 and endoplasmic reticulum (ER) stress signaling and discuss their potential impact on cancer development.