Liang Liu

Abstract While lymphocytopenia is a common characteristic of patients infected by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the mechanisms responsible for this depletion are unclear. Through careful inspection of the spleens and lymph nodes (LNs) from six cases with postmortem examinations, we observed that SARS-CoV-2 could directly infect secondary lymphoid organs to induce cell death. Immunohistochemistry demonstrated ACE2 (angiotensin-converting enzyme 2), the potential receptor of SARS-CoV-2, expresses on tissue-resident CD169 + macrophages in spleens and LNs. Immunofluorescent staining confirmed that viral nucleocaspid protein (NP) can be found in ACE2 + cells, CD169 + macrophages, but not in CD3 + T cells or B220 + B cells in spleens and LNs. SARS-CoV-2 infection induces severe tissue damage including lymph follicle depletion, splenic nodule atrophy, histiocyte hyperplasia and lymphocyte reductions. Moreover, in situ TUNEL staining illustrated that viral infection leads to severe lymphocyte apoptosis, which might be mediated by viral antigens inducing Fas upregulation. Furthermore, SARS-CoV-2 also triggers macrophages to produce IL-6, a proinflammatory cytokine that directly promotes lymphocyte necrosis. Collectively, these results demonstrate that SARS-CoV-2 directly neutralizes human spleens and LNs through infecting tissue-resident CD169 + macrophages.

Mesenchymal stem cells (MSCs) have been reported to localize in colorectal carcinomas, and participate in the formation of the tumor microenvironment. They have recently been isolated from colorectal cancer tissues, and are implicated in the growth, invasion, and metastasis of cancer cells. However, the roles and detailed mechanisms associated with human colorectal cancer-derived MSCs (CC-MSCs) have not been fully addressed. In this study, we found that CC-MSCs increased the migration and invasion of colorectal cancer cells and promoted the tumorigenesis of colorectal cancer through epithelial-to-mesenchymal transition (EMT) in vitro. We also found that CC-MSCs enhanced the growth and metastasis of colorectal cancer in vivo. Mechanistically, we determined that interleukin-6 (IL-6) was the most highly expressed cytokine in the CC-MSC conditioned medium, and promoted the progression of colorectal cancer cells through IL-6/JAK2/STAT3 signaling, which activated PI3K/AKT signaling. We used anti-IL-6 antibody to target IL-6. Collectively, these results reveal that the IL-6 secreted by CC-MSCs enhances the progression of colorectal cancer cells through IL-6/JAK2/STAT3 signaling, and could provide a novel therapeutic or preventive target.

Abstract Background Focal adhesion plays an essential role in tumour invasiveness and metastasis. Hippo component YAP has been widely reported to be involved in many aspects of tumour biology. However, its role in focal adhesion regulation in breast cancer remains unexplored. Methods Tissue microarray was used to evaluate YAP expression in clinical breast cancer specimens by immunohistochemical staining. Cell migration and invasion abilities were measured by Transwell assay. A cell adhesion assay was used to measure the ability of cell adhesion to gelatin. The focal adhesion was visualized through immunofluorescence. Phosphorylated FAK and other proteins were detected by Western blot analysis. Gene expression profiling was used to screen differently expressed genes, and gene ontology enrichment was performed using DAVID software. The gene mRNA levels were measured by quantitative real-time PCR. The activity of the THBS1-promoter was evaluated by dual luciferase assay. Chromatin immunoprecipitation (ChIP) was used to verify whether YAP could bind to the THBS1-promoter region. The prediction of potential protein-interaction was performed with the String program. The ChIP sequence data of TEAD was obtained from the ENCODE database and analysed via the ChIP-seek tool. The gene expression dataset (GSE30480) of purified tumour cells from primary breast tumour tissues and metastatic lymph nodes was used in the gene set enrichment analysis. Prognostic analysis of the TCGA dataset was performed by the SurvExpress program. Gene expression correlation of the TCGA dataset was analysed via R2: Genomics Analysis and Visualization Platform. Results Our study provides evidence that YAP acts as a promoter of focal adhesion and tumour invasiveness via regulating FAK phosphorylation in breast cancer. Further experiments reveal that YAP could induce FAK phosphorylation through a TEAD-dependent manner. Using gene expression profiling and bioinformatics analysis, we identify the FAK upstream gene, thrombospondin 1, as a direct transcriptional target of YAP-TEAD. Silencing THBS1 could reverse the YAP-induced FAK activation and focal adhesion. Conclusion Our results unveil a new signal axis, YAP/THBS1/FAK, in the modulation of cell adhesion and invasiveness, and provides new insights into the crosstalk between Hippo signalling and focal adhesion.

Dear Editor,To date, the number of confirmed coronavirus disease 2019 (COVID-19) cases has surpassed 100 million, with deaths exceeding 2 million, yet the mechanism by which severe acute respiratory syndrome coronavirus (SARS-CoV)-2 attacks the body remains unclear.Although SARS-CoV-2 is known to primarily target the lung, it is also believed to cause multi-organ dysfunction and comprehensive studies on SARS-CoV-2 cell tropism in humans are lacking.SARS-CoV-2 exploits the host angiotensin-converting enzyme 2 (ACE2) as its receptor for cell entry 1 , but the correlation between SARS-CoV-2 organ/cell tropism and ACE2 distribution is unclear.Here, we studied these issues via a systemic analysis of postmortem specimens from a 66-year-old female COVID-19 patient who had rapidly developed multiorgan failure.The patient died in the hospital on Day 13 of admission (Day 16 of illness) and her autopsy was performed at 8 h after death.To elucidate SARS-CoV-2 tissue tropism, we used immunohistochemical and immunofluorescence staining.Results showed that viral antigens (spike proteins) were highly expressed in pneumocytes and hyperplastic cells around the bronchioles (Supplementary Fig. S1a-c); mucosal epithelia, submucosal glands, and gland ducts of the trachea (Supplementary Fig. S1d-f); mucosal epithelia and glands of the small intestine (Supplementary Fig. S1g,i); distal tubules and collecting ducts of the kidneys (Supplementary Fig. S1j-l); islets of Langerhans, glands, and intraislet ducts of the pancreas (Supplementary Fig. S1m,n); and

PURPOSE: Aberrant activation of beta-catenin contributes to the malignant phenotype in hepatocellular carcinoma (HCC). Hypoxia is also known to promote HCC invasion and metastasis. However, the association between beta-catenin and the proinvasive role of hypoxia remains unclear. We investigated the role of beta-catenin in the proinvasive consequences of hypoxia in HCC. EXPERIMENTAL DESIGN: We established in vitro and in vivo hypoxic models to investigate the expression of beta-catenin in hypoxic HCC cells and its role in hypoxia-induced aggressiveness. The clinical significance of beta-catenin and/or hypoxia-induced factor-1alpha (HIF-1alpha) was evaluated using HCC tissue microarrays. RESULTS: Hypoxia induced beta-catenin overexpression and/or intracellular accumulation in four HCC cell lines through downregulating the endogenous degradation machinery, and promoted in vitro invasion and in vivo metastasis of MHCC97 and Hep3B cells. Besides morphologic changes, hypoxic MHCC97 and Hep3B cells exhibited molecular alterations consistent with epithelial-mesenchymal transition, characterized by the loss of epithelial cell markers (E-cadherin and plakoglobin) and upregulation of mesenchymal markers (vimentin and N-cadherin), as well as the increase of matrix metalloproteinase 2. However, silencing beta-catenin in these hypoxic cells reversed epithelial-mesenchymal transition and repressed metastatic potential. Positive expression of beta-catenin in HCC tissue microarray was associated with the expression of HIF-1alpha (P=0.034), and coexpression of beta-catenin and HIF-1alpha in HCC was correlated with shorter overall survival and time to recurrence. CONCLUSION: beta-Catenin in HCC is activated by hypoxia and contributes to hypoxia-induced metastatic potential.