In Vivo Expression of the Novel CXC Chemokine BRAK in Normal and Cancerous Human Tissue

Abstract

Using differential display, we cloned a gene with reduced expression in short-term explants of head and neck squamous cell carcinoma (HNSCC) tumors compared to cultured normal oral epithelial cells. The differentially expressed gene was identical to the recently cloned CXC chemokine BRAK, which is ubiquitously expressed in normal tissue extracts but is absent from many tumor cell lines in vitro. To define the cell populations expressing BRAK in vivo, in situ mRNA hybridization was performed on normal and cancerous tissues from six different histological sites. The predominant normal cell type constitutively expressing BRAK in vivo was squamous epithelium. Expression in tumors was heterogeneous, with the majority of HNSCCs and some cervical squamous cell carcinomas (SCCs) showing loss of BRAK mRNA. Although absent in unstimulated peripheral blood mononuclear cells, high levels of BRAK were consistently found in infiltrating inflammatory cells (with lymphocyte morphology) in nearly all cancers examined. Furthermore, BRAK expression was demonstrated in B cells and monocytes, after stimulation of peripheral blood mononuclear cells with lipopolysaccharide. This study demonstrates for the first time up-regulation of BRAK mRNA by inflammatory cells in the tumor microenvironment and lost expression from certain cancers in vivo. The data suggest that BRAK may have a role in host-tumor interactions.

The atypical Rho GTPase RhoBTB2 is required for expression of the chemokine CXCL14 in normal and cancerous epithelial cells

“…Although CXCL14 was not reported as a target of RhoBTB2 in HeLa cells previously (Siripurapu et al, 2005), we saw the same robust loss of CXCL14 expression in HeLa cells treated with RhoBTB2 siRNAs (Figure 2b). (Hromas et al, 1999;Frederick et al, 2000). The level of CXCL14 in medium conditioned by NHBE cells was too low to detect in this assay (o100 pg/ml; data not shown).…”

“…CXCL14 is expressed by epithelial cells (Hromas et al, 1999;Frederick et al, 2000) and is a chemokine for monocytes (Kurth et al, 2001), natural killer cells (Starnes et al, 2006) and immature dendritic cells (Shellenberger et al, 2004;Schaerli et al, 2005). CXCL14 expression is lost at high frequency in wide range of epithelial tumors (Hromas et al, 1999;Frederick et al, 2000;Schwarze et al, 2002;Shellenberger et al, 2004;Shurin et al, 2005), although the mechanism for this loss is unknown. Loss of CXCL14 expression is associated with reduced leukocyte infiltration in tumors, leading to the proposal that loss of CXCL14 allows tumors to evade immune surveillance (Shurin et al, 2005).…”

“…The level of CXCL14 in medium conditioned by NHBE cells was too low to detect in this assay (o100 pg/ml; data not shown). We therefore examined keratinocytes, which express high levels of CXCL14 (Frederick et al, 2000;Shurin et al, 2005). As with NHBE cells, normal primary human keratinocytes showed dramatic downregulation of CXCL14 mRNA Humans have two related RhoBTB genes; RhoBTB1 and RhoBTB2, and the two proteins show a high degree of similarity in sequence (73% identity).…”

Murine CXCL14 Is Dispensable for Dendritic Cell Function and Localization within Peripheral Tissues

“…CXCL14 is a chemokine with unknown function and receptor selectivity (4,9,15). Human CXCL14, alternatively called BRAK and MIP-2␥, is constitutively produced in healthy epithelial tissues such as skin and gut.…”

“…Human CXCL14, alternatively called BRAK and MIP-2␥, is constitutively produced in healthy epithelial tissues such as skin and gut. CXCL14 is also present in various tumors of epithelial origin, but the level of expression is heterogeneous, with the majority showing a downregulation with respect to healthy tissue (4,9,15,19,43,44,46). Recently, we have shown that human CXCL14 is selective for blood monocytes and CD14 ϩ DC precursors, either derived from CD34 ϩ hematopoietic progenitor cells or isolated from blood (19,42).…”