Biology subjects

Bekkhus, T.

Publications and source records attributed to Bekkhus, T..

3 recordsLinked to original sources

bioRxiv2025

Podoplanin-Linked Mesenchymal Shift Synergizes with CCR7 driving Lymphatic Metastasis and Tumor Progression in Breast Cancer

Epithelial-to-mesenchymal-transition (EMT) and upregulation of chemokine receptors are linked to lymphatic metastasis in various types of cancer including breast cancer. However, the underlying molecular mechanisms are not fully understood. Using a triple-negative mammary carcinoma model, conditioned for lymphatic metastasis through expression of the C-C chemokine receptor 7 (CCR7), we identified intrinsic tumor plasticity associated with EMT as a critical determinant for effective metastasis. Specifically, tumor cells upregulate Podoplanin (PDPN) as part of a spontaneous mesenchymal shift that promotes lymphatic dissemination and tumor growth. Intriguingly, the expression of CCR7, or PDPN alone, was not sufficient for these effects. CCR7- and PDPN-positive tumors displayed an immune-cold tumor profile, compared to control, characterized by reduced tumor-infiltrating T-cells. Consistent with this, we found that spontaneous upregulation of PDPN was linked to hypoxia and was associated with the downregulation of homeostatic interferon signaling, and increased expression of collagens. Analysis of single-cell data sets showed that PDPN expression was heterogeneous and correlated significantly with EMT markers, collagen expression, and hypoxia hallmark in human breast cancer cell lines and primary human triple negative (TN) breast cancer, mirroring findings in the mouse model. Further analysis of the human breast cancer METABRIC-microarray datasets supported an association between a high CCR7/PDPN mRNA expression score and aggressive breast cancer subtypes with an independent prognostic value in lymph node-positive tumors. Together, these findings highlight a critical role of tumor microenvironment-driven tumor plasticity and molecular synergy between CCR7 and PDPN-coupled EMT shift in promoting chemokine receptor-mediated tumor dissemination and progression. SummaryCCR7-driven lymphatic metastasis requires a mesenchymal shift with PDPN upregulation. This tumor plasticity, linked to hypoxia and immune evasion, suggests CCR7-PDPN synergy in aggressive breast cancer progression and poor prognosis.

cancer biology↗

bioRxiv2022

Stromal transdifferentiation drives lymph node lipomatosis and induces extensive vascular remodeling

Lymph node (LN) lipomatosis is a common, but rarely discussed phenomenon, associated with aging, involving a gradual exchange of the LN parenchyma into adipose tissue. The mechanisms behind these changes and the effects on the LN have been unknown. We show that LN lipomatosis starts in the medullary regions of the human LN and link the initiation of lipomatosis to transdifferentiation of LN medullary fibroblasts into adipocytes. The latter is associated with a downregulation of lymphotoxin beta expression. We also show that, medullary fibroblasts, in contrast to the reticular cells in the T-cell zone, display an inherent higher sensitivity for adipogenesis. Progression of lipomatosis leads to a gradual loss of the medullary lymphatic network, but at later stages, collecting-like lymphatic vessels, are found inside the adipose tissue. The stromal dysregulation includes a dramatic remodeling and dilation of the high endothelial venules associated with reduced density of naive T-cells. Abnormal clustering of plasma cells is also observed. Thus, LN lipomatosis causes widespread stromal dysfunction with consequences for the immune contexture of the human LN. Our data warrant an increased awareness of LN lipomatosis as a factor contributing to decreased immune functions in the elderly and in disease. Graphical abstractIn lymph nodes (LNs) of young patients there is a normal lymph flow, normal and functioning high endothelial venules (HEVs) with a high density of surrounding naive T-cells. With aging lymphotoxin beta (LTB) is downregulated in the medulla of the LN and the fibroblasts of the medulla, namely the medullary reticular cells (MedRCs), transdifferentiate into adipocytes inducing LN lipomatosis. LN lipomatosis leads to loss of lymphoid tissue, medullary sinuses and can be predicted to result in a shortcut of the lymph flow based on the presence of collecting-like vessels in the adipose tissue in late stage lipomatosis. Lipomatosis also induce extensive vascular remodeling with loss of medullary lymphatic vessels and dysfunctional, highly dilated HEVs with lower density of naive T-cells and trapped plasma cells. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=148 SRC="FIGDIR/small/498248v1_ufig1.gif" ALT="Figure 1"> View larger version (60K): org.highwire.dtl.DTLVardef@1634935org.highwire.dtl.DTLVardef@15b77e9org.highwire.dtl.DTLVardef@1d8ab2org.highwire.dtl.DTLVardef@17ceccd_HPS_FORMAT_FIGEXP M_FIG C_FIG

pathology↗

bioRxiv2020

A single-cell transcriptional roadmap of the mouse and human lymph node lymphatic vasculature

Single-cell transcriptomics promises to revolutionize our understanding of the vasculature. Emerging computational methods applied to high dimensional single cell data allow integration of results between samples and species, and illuminate the diversity and underlying developmental and architectural organization of cell populations. Here, we illustrate these methods in analysis of mouse lymph node (LN) lymphatic endothelial cells (LEC) at single cell resolution. Clustering identifies five well-delineated subsets, including two medullary sinus subsets not recognized previously as distinct. Nearest neighbor alignments in trajectory space position the major subsets in a sequence that recapitulates known and suggests novel features of LN lymphatic organization, providing a transcriptional map of the lymphatic endothelial niches and of the transitions between them. Differences in gene expression reveal specialized programs for (1) subcapsular ceiling endothelial interactions with the capsule connective tissue and cells, (2) subcapsular floor regulation of lymph borne cell entry into the LN parenchyma and antigen presentation, and (3) medullary subset specialization for pathogen interactions and LN remodeling. LEC of the subcapsular sinus floor and medulla, which represent major sites of cell entry and exit from the LN parenchyma respectively, respond robustly to oxazolone inflammation challenge with enriched signaling pathways that converge on both innate and adaptive immune responses. Integration of mouse and human single-cell profiles reveals a conserved cross-species pattern of lymphatic vascular niches and gene expression, as well as specialized human subsets and genes unique to each species. The examples provided demonstrate the power of single-cell analysis in elucidating endothelial cell heterogeneity, vascular organization and endothelial cell responses. We discuss the findings from the perspective of LEC functions in relation to niche formations in the unique stromal and highly immunological environment of the LN. Highlights Computational alignments ("trajectories") predict LN LEC organization in situ, revealing a continuum of phenotypes punctuated by specialized clusters Multiple intermediate phenotypes suggest LEC malleability Gene profiles define niche-specific functional specialization Medullary sinus LECs are comprised of Ptx3-LECs and Marco-LECs O_LIDistinct mechanisms for pathogen interactions and matrix modeling C_LIO_LIPtx3-LECs: paracortical and central medullary sinuses near hilus; enriched for genes driving lymphangiogenic responses and lymphocyte egress C_LIO_LIMarco-LECs: peri-follicular medullary sinuses; macrophage-associated genes, complement and coagulation cascade C_LI Niche-specific responses to inflammation O_LIIFN gene responses in SCS floor and medullary sinus LECs C_LIO_LISuppression of LEC identity genes in responding subsets C_LI Conserved and unique LEC subsets and gene programs across species O_LICore subsets common to mouse and human C_LIO_LIGreater diversity of subsets and intermediates in human LN LECs C_LI

systems biology↗