LYVE-1+ macrophages form a collaborative CCR5-dependent perivascular niche that influences chemotherapy responses in murine breast cancer

Tumor-associated macrophages (TAMs) are a heterogeneous population of cells that facilitate cancer progression. However, our knowledge of the niches of individual TAM subsets and their development and function remain incomplete. Here, we describe a population of lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1)-expressing TAMs, which form coordinated multi-cellular “nest” structures that are heterogeneously distributed proximal to vasculature in tumors of a spontaneous murine model of breast cancer. We demonstrate that LYVE-1+ TAMs develop in response to IL-6, which induces their expression of the immune-suppressive enzyme heme oxygenase-1 and promotes a CCR5-dependent signaling axis, which guides their nest formation. Blocking the development of LYVE-1+ TAMs or their nest structures, using gene-targeted mice, results in an increase in CD8+ T cell recruitment to the tumor and enhanced response to chemotherapy. This study highlights an unappreciated collaboration of a TAM subset to form a coordinated niche linked to immune exclusion and resistance to anti-cancer therapy

Cassava genome from a wild ancestor to cultivated varieties

Cassava is a major tropical food crop in the Euphorbiaceae family that has high carbohydrate production potential and adaptability to diverse environments. Here we present the draft genome sequences of a wild ancestor and a domesticated variety of cassava and comparative analyses with a partial inbred line. We identify 1,584 and 1,678 gene models specific to the wild and domesticated varieties, respectively, and discover high heterozygosity and millions of single-nucleotide variations. Our analyses reveal that genes involved in photosynthesis, starch accumulation and abiotic stresses have been positively selected, whereas those involved in cell wall biosynthesis and secondary metabolism, including cyanogenic glucoside formation, have been negatively selected in the cultivated varieties, reflecting the result of natural selection and domestication. Differences in microRNA genes and retrotransposon regulation could partly explain an increased carbon flux towards starch accumulation and reduced cyanogenic glucoside accumulation in domesticated cassava. These results may contribute to genetic improvement of cassava through better understanding of its biology

LYVE-1+ macrophages form a collaborative CCR5-dependent perivascular niche that influences chemotherapy responses in murine breast cancer.

Tumor-associated macrophages (TAMs) are a heterogeneous population of cells that facilitate cancer progression. However, our knowledge of the niches of individual TAM subsets and their development and function remain incomplete. Here, we describe a population of lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1)-expressing TAMs, which form coordinated multi-cellular "nest" structures that are heterogeneously distributed proximal to vasculature in tumors of a spontaneous murine model of breast cancer. We demonstrate that LYVE-1 + TAMs develop in response to IL-6, which induces their expression of the immune-suppressive enzyme heme oxygenase-1 and promotes a CCR5-dependent signaling axis, which guides their nest formation. Blocking the development of LYVE-1 + TAMs or their nest structures, using gene-targeted mice, results in an increase in CD8 + T cell recruitment to the tumor and enhanced response to chemotherapy. This study highlights an unappreciated collaboration of a TAM subset to form a coordinated niche linked to immune exclusion and resistance to anti-cancer therapy

Integrin-interacting proteins in human cancer progression

Integrins are the major transmembrane receptors for the extracellular matrix (ECM) which regulate a diverse array of cellular functions crucial to tumor cell migration, invasion, proliferation and survival. Integrins contact the ECM via their N-terminal extracellular domains and connect to the intracellular environment via the C-terminal cytoplasmic domains. Therefore, studies on the integrins cytoplasmic domain binding proteins will help to better understand the mechanisms of tumor progression and make them appealing targets for cancer therapy. Kindlin and PAK (p21-activated kinase) family proteins have been identified as integrin-interacting proteins. The following studies in this thesis aimed to investigate the role of Kindlin-2 and PAK5 in human cancer progression. In paper I, we investigated the expression of Kindlin-2 in a series of malignant mesothelioma (MM) and found it to be highly expressed and correlated to tumor cell proliferation. To evaluate the biological relevance of Kindlin-2 in MM, we also evaluated ILK (integrin-linked kinase) and Kindlin-1 expression levels. Notably, in vitro depletion of Kindlin-2 impaired tumor cell adhesion and migration. Our findings provide new evidence that Kindlin-2 contributes to MM progression and may therefore be a potential target for anti-cancer therapy in MM. In paper II, we demonstrated a novel role of Kindlin-2 as a signaling molecule that controls a Wnt-paralleling signaling pathway. We showed that Kindlin-2 specifically activates small GTPase Cdc42, but not Rac1 and RhoA, and regulates beta-catenin activation via a Cdc42 -PAR 6 -PKCzeta -GSK-3beta cascade. Overexpression of Kindlin-2 in zebrafish embryo xenograft promotes tumor growth, invasion and dissemination. Importantly, overexpression of Kindlin-2 correlates to a poor prognosis in malignant mesothelioma patients, suggesting an important role of Kindlin-2 in cancer progression. Our data indicates that Kindlin-2 controls a signaling pathway that regulates tumor cell invasive growth. In paper III, we used the human prostate cancer cell line PC-3 as a working model and to analyze the role of Kindlin-2 in cell cycle regulation by a loss-of-function approach. We found that depletion of Kindlin-2 causes mitotic arrest during metaphase, with cyclin B1 accumulation, mitotic spindle disruption, γ tubulin mislocation and abnormal chromosome formation. In addition, we demonstrated that Kindlin-2 is involved in Cdc42 mediated functions at metaphase. Our results identify a novel role of Kindlin-2 in the regulation of cell cycle progression in mitosis. In paper IV, we showed that PAK5 was overexpressed in colorectal carcinoma (CRC) and associated with CRCs progression from adenoma to carcinoma. Overexpression of PAK5 also correlated to CRC development from lower Duke s grades to higher grades and correlated to CRC cell differentiation. Depletion of PAK5 reduced CRC cell adhesion but promoted their migration. Our study demonstrated that PAK5 expression correlates to CRC progression and that PAK5 promotes CRC metastasis by regulating CRC cell adhesion and migration. Taken together, our studies highlight the importance of Kindlin-2 and PAK5 association with human cancer. This work also strengthens the link between Kindlin-2 and PAK5 expression and tumor malignancy in general, and therefore, promotes Kindlin-2 and PAK5 as novel putative targets for anti-cancer therapies

Regulation of mesenchymal stem to transit amplifying cell transition in the continuously growing mouse incisor

Summary In adult tissues and organs with high turnover rates, the generation of transit-amplifying cell (TAC) populations from self-renewing stem cells drives cell replacement. The role of stem cells is to provide a renewable source of cells that give rise to TACs to provide the cell numbers that are necessary for cell differentiation. Regulation of the formation of TACs is thus fundamental to controlling cell replacement. Here, we analyze the properties of a population of mesenchymal TACs in the continuously growing mouse incisor to identify key components of the molecular regulation that drives proliferation. We show that the polycomb repressive complex 1 acts as a global regulator of the TAC phenotype by its direct action on the expression of key cell-cycle regulatory genes and by regulating Wnt/β-catenin-signaling activity. We also identify an essential requirement for TACs in maintaining mesenchymal stem cells, which is indicative of a positive feedback mechanism

A quiescent cell population replenishes mesenchymal stem cells to drive accelerated growth in mouse incisors.

Mouse incisors constantly renew from a slow cycling population of mesenchymal stem cells. Here, the authors show that upon cutting of adult incisors, a sub-population of dental mesenchymal stem cells reactivates, allowing an increased growth rate and rapid regeneration

Ring1a/b polycomb proteins regulate the mesenchymal stem cell niche in continuously growing incisors

AbstractRodent incisors are capable of growing continuously and the renewal of dental epithelium giving rise to enamel-forming ameloblasts and dental mesenchyme giving rise to dentin-forming odontoblasts and pulp cells is achieved by stem cells residing at their proximal ends. Although the dental epithelial stem cell niche (cervical loop) is well characterized, little is known about the dental mesenchymal stem cell niche. Ring1a/b are the core Polycomb repressive complex1 (PRC1) components that have recently also been found in a protein complex with BcoR (Bcl-6 interacting corepressor) and Fbxl10. During mouse incisor development, we found that genes encoding members of the PRC1 complex are strongly expressed in the incisor apical mesenchyme in an area that contains the cells with the highest proliferation rate in the tooth pulp, consistent with a location for transit amplifying cells. Analysis of Ring1a−/−;Ring1bcko/cko mice showed that loss of Ring1a/b postnatally results in defective cervical loops and disturbances of enamel and dentin formation in continuously growing incisors. To further characterize the defect found in Ring1a−/−;Ring1bcko/cko mice, we demonstrated that cell proliferation is dramatically reduced in the apical mesenchyme and cervical loop epithelium of Ring1a−/−;Ring1bcko/cko incisors in comparison to Ring1a−/−;Ring1bfl/fl cre- incisors. Fgf signaling and downstream targets that have been previously shown to be important in the maintenance of the dental epithelial stem cell compartment in the cervical loop are downregulated in Ring1a−/−;Ring1bcko/cko incisors. In addition, expression of other genes of the PRC1 complex is also altered. We also identified an essential postnatal requirement for Ring1 proteins in molar root formation. These results show that the PRC1 complex regulates the transit amplifying cell compartment of the dental mesenchymal stem cell niche and cell differentiation in developing mouse incisors and is required for molar root formation