Analysis of the human lumican gene promoter

Lumican inhibits immune escape and carcinogenic pathways in colorectal adenocarcinoma

Lumican (LUM), a small leucine-rich proteoglycan, is a component of the extracellular matrix. Abnormal LUM expression is potentially associated with cancer progression. In the present study, we confirmed high LUM mRNA expression in colorectal adenocarcinoma (COAD) through the UALCAN database. The Kaplan-Meier method, univariate, and multivariate COX analysis showed that high LUM expression is an independent determinant of poor prognosis in COAD. A COX regression model was constructed based on clinical information and LUM expression. The receiver operating characteristic (ROC) curve indicated that this model was highly accurate in monitoring COAD prognosis. The co-expression network of LUM was determined by LinkedOmics, which showed that LUM expression was closely related to immune escape and the miR200 family. Furthermore, we studied the co-expression network of LUM and found that LUM could promote tumor metastasis and invasion. The Tumor Immune Estimation Resource website showed that LUM was closely related to immune infiltration and correlated with regulatory T cells, tumour-associated macrophages, and dendritic cells. We found that LUM cultivated cancer progression by targeting the miR200 family to promote epithelial-to-mesenchymal transition. These findings suggest that LUM is a potential target for inhibiting immune escape and carcinogenic pathways.

Irx3 and Bmp2 regulate mouse mesenchymal cell chondrogenic differentiation in both a Sox9-dependent and -independent manner

Sox9, a master regulator of cartilage development, controls the cell fate decision to differentiate from mesenchymal to chondrogenic cells. In addition, Sox9 regulates the proliferation and differentiation of chondrocytes, as well as the production of cartilage-specific proteoglycans. The existence of Sox9-independent mechanisms in cartilage development remains to be determined. Here, we attempted to identify genes involved in such putative mechanisms via microarray analysis using a mouse chondrogenic cell line, N1511. We first focused on transcription factors that exhibited upregulated expression following Bmp2 treatment, which was not altered by subsequent treatment with Sox9 siRNA. Among these, we selected positive regulators for chondrogenesis and identified Iroquois-related homeobox 3 (Irx3) as one of the candidate genes. Irx3 expression gradually increased with chondrocyte terminal differentiation in a reciprocal manner to Sox9 expression, and promoted the chondrogenic differentiation of mesenchymal cells upon Bmp2 treatment. Furthermore, Irx3 partially rescued impaired chondrogenesis by upregulating the expression of epiphycan and lumican under reduced Sox9 expression. Finally, Irx3 was shown to act in concert with Bmp2 signaling to activate the p38 MAPK pathway, which in turn stimulated Sox9 expression, as well as the expression of epiphycan and lumican in a Sox9-independent manner. These results indicate that Irx3 represents a novel chondrogenic factor of mesenchymal cells, acts synergistically with Bmp2-mediated signaling, and regulates chondrogenesis independent of the transcriptional machinery associated with Sox9-mediated regulation.

Identification of transcripts modulated by ETV6 expression

Deletions at chromosome 12p12-13 are observed in 26-47% of childhood pre-B acute lymphoblastic leukaemia (ALL) cases, suggesting the presence of a tumour suppressor gene (TSG). Accumulating genetic and functional evidence points to ETV6 as being the most probable TSG targeted by the deletions. ETV6 is a ubiquitously expressed transcription factor of the ETS family with very few known targets. To understand its function and to elucidate the impact of its absence in leukaemia, we conducted a study to identify targeted genes. Following the induction of ETV6 expression, global expression was evaluated at different time points. We identified 87 modulated genes, of which 10 (AKR1C1, AKR1C3, IL18, LUM, PHLDA1, PTGER4, PTGS2, SPHK1, TP53 and VEGF) were validated by real-time quantitative reverse transcription-polymerase chain reaction. To assess the significance of the validated candidate genes in leukaemia, their expression patterns were determined, as well as that of ETV6, in pre-B ALL patients. The expression of IL18, LUM, PTGER4, SPHK1 and TP53 was significantly correlated with that of ETV6, further suggesting that ETV6 could regulate the expression of these genes in leukaemia. This work constitutes another step towards the understanding of the functions of ETV6 and the impact of its inactivation in childhood leukaemia.

Transcriptional regulation of the human HFE gene indicates high liver expression and erythropoiesis coregulation

The human HFE gene is clearly involved in hereditary hemochromatosis, a common autosomal recessive genetic disorder of iron homeostasis. However, the precise role of the HFE protein is still undefined. Here, to obtain new insight, we analyzed the transcriptional regulation of HFE gene and defined the functional organization of the HFE promoter. Both in vitro transcription and reporter gene assay in transient transfection evidenced a high liver expression of the HFE mRNA. The 5' end analysis of mRNA showed two major initiation sites localized at -265 and -195 directed by TATA-like sequences and a window of initiation within the -120 to -10 GC-rich region upstream of the first coding nucleotide. Positive cis-regulating elements were characterized within the -1057/-8 region, and a negative one extending upstream (-1485/-1057) was identified. DNase I footprinting analysis and gel shift assay revealed several protein binding sites, and subsequent functional analysis evidenced transactivation of HFE by liver-enriched C/EBPalpha, erythropoietic-specific GATA-1, and ubiquitous Sp1 transcription factors. These data bring some evidence of a role of HFE in the liver and a coregulation with erythropoiesis as other genes involved in iron homeostasis.

Lumican is down-regulated in cells expressing endoglin. Evidence for an inverse correlationship between Endoglin and Lumican expression

Endoglin (CD105) is a homodimeric membrane glycoprotein, which acts as a TGF-beta coreceptor in the vasculature and plays an important role in cardiovascular development and vascular remodelling. To isolate putative genes regulated by endoglin expression, a PCR-based RNA fingerprinting technique was carried out. Myoblasts stably transfected with endoglin showed a decrease in the expression of lumican both at the RNA and protein levels. Lumican is a proteoglycan of the extracellular matrix, belonging to the SLRP (Small Leucine-Rich Repeat Proteoglycans) family. Lumican down-regulation by endoglin appeared to be controlled, at least in part, at the transcriptional level, as indicated by RT-PCR, and transient transfection experiments using a lumican promoter reporter based vector. This inverse correlation between endoglin and lumican expression was substantiated by immunohistochemical staining of vessels from human tissues. Thus, cells belonging to the high endothelia, such as tonsil, express a large amount of endoglin, and the lumican content of their matrix is considerably reduced. Conversely, in resting endothelia, such as that of large vessels, the expression of endoglin is reduced whereas the amount of lumican is greatly increased. The inverse regulation in the expression of endoglin and lumican was also evident after TGF-beta treatments since endoglin was up-regulated, whereas lumican was down-regulated by this cytokine. This report describes for the first time a relationship between endoglin and lumican expression.

Lumican is a major proteoglycan component of the bone matrix

MC3T3-E1 mouse calvaria cells are a clonal population of committed osteoprogenitors that in the presence of appropriate supplements form a mineralized bone matrix. The development of the MC3T3-E1 cells can be divided into three major stages, namely, proliferation, differentiation, and mineralization. Recently, using the cDNA microarray technology we found lumican to be abundantly expressed during the mineralization and differentiation stages of the MC3T3-E1 development and not during the proliferation stage. Lumican has been shown to play essential roles in regulating collagen fibril formation in different extracellular matrices but its expression in the developing bone matrix remains elusive. By examining the expression profile of this gene during the different stages of MC3T3-E1 development, utilizing the 'real-time' PCR technology, we observed that the expression of lumican increases as the osteoblast culture differentiates and matures, suggesting that lumican may be involved in regulating collagen fibrillogenesis in bone matrices. Using immunostaining, we observed that during the early embryonic development of mouse (E11 to E13), lumican is mainly expressed in the cartilaginous matrices. However, in the older embryos (E14 to E16), the expression of lumican is more prominent in the developing bone matrices. Our data suggest that lumican is a significant proteoglycan component of bone matrix, which is secreted by differentiating and mature osteoblasts only and therefore it can be used as a marker to distinguish proliferating pre-osteoblasts from the differentiating osteoblasts.

Roles of lumican and keratocan on corneal transparency

Lumican and keratocan are members of the small leucine-rich proteoglycan (SLRP) family, and are the major keratan sulfate (KS) proteoglycans in corneal stroma. Both lumican and keratocan are essential for normal cornea morphogenesis during embryonic development and maintenance of corneal topography in adults. This is attributed to their bi-functional characteristic (protein moiety binding collagen fibrils to regulate collagen fibril diameters, and highly charged glycosaminoglycan (GAG) chains extending out to regulate interfibrillar spacings) that contributes to their regulatory role in extracellular matrix assembly. The absence of lumican leads to formation of cloudy corneas in homozygous knockout mice due to altered collagenous matrix characterized by larger fibril diameters and disorganized fibril spacing. In contrast, keratocan knockout mice exhibit thin but clear cornea with insignificant alteration of stromal collaegenous matrix. Mutations of keratocan cause cornea plana in human, which is often associated with glaucoma. These observations suggest that lumican and keratocan have different roles in regulating formation of stromal extracellular matrix. Experimental evidence indicates that lumican may have additional biological functions, such as modulation of cell migration and epithelium-mesenchyme transition in wound healing and tumorgenesis, besides regulating collagen fibrillogenesis.