Functional characterization of THY1 as a tumor suppressor gene with antiinvasive activity in nasopharyngeal carcinoma

Abstract

THY1 was previously identified as a candidate tumor suppressor gene (TSG) associated with lymph node metastases in nasopharyngeal carcinoma (NPC) through functional studies. It was identified by oligonucleotide microarray analysis as an interesting differentially expressed gene. However, direct functional evidence is still lacking for THY1 being a TSG in NPC, as in vivo tumorigenicity assays have not been previously reported in our last study of THY1. In this study, a tetracycline-inducible expression vector, pETE-Bsd, was used to obtain stable transfectants of THY1. The stringent in vivo tumorigenicity assay results show that the activation of THY1 suppresses tumor formation of HONE1 cells in nude mice, and the tumor formation ability was restored in the presence of doxycycline (a tetracycline analog), when the gene is shut off. Functional inactivation of this gene is observed in all the tumors derived from the tumorigenic transfectant. The tumor suppressive effect could be repressed by knockdown of THY1 expression in nontumorigenic microcell hybrids. Further studies indicate that expression of THY1 inhibits HONE1 cell growth in vitro by arresting cells in G 0 /G 1 phase. It greatly reduces the ability for anchorage-independent growth. The invasiveness of HONE1 cells was also inhibited by the expression of THY1. These findings suggest that THY1 is a TSG in NPC, which is involved in invasion and shows an association with tumor metastasis. Taken together, THY1 clearly plays an important functional role in tumor suppression in NPC.THY1 (CD90) is a cell surface glycoprotein of 25-37 kDa localized on the outer leaflet of cell membranes, enriched in lipid raft microdomains. Human THY1 maps to chromosome 11q22.3. It is expressed on various cell types, including human fibroblasts, neurons, blood stem cells and endothelial cells as well as murine T cells.1 THY1 is involved in T cell activation and the other nonimmunologic functions including inhibition of neurite outgrowth, apoptotic signaling, leukocyte and melanoma cell adhesion and migration and fibroblast proliferation and migration. 2,3 Taken together, these functions suggest that THY1 is an important mediator of cell-cell and cell-matrix interactions. In T cells, it is reported to function in cell adhesion with the bone marrow stroma.1 Surface expression of THY1 promotes focal adhesion in fibroblasts. 2In cancers, THY1 was initially found to be differentially expressed in tumorigenic and nontumorigenic hybrid clones derived from the transfer of chromosome 11 into the human ovarian cancer cell line SKOV-3. 4 The later functional studies also suggest that THY1 is associated with tumor suppression in human ovarian cancer.5 A recent study shows that loss of THY1 expression is correlated with poor survival rate in neuroblastoma patients.6 THY1 is also involved in the adhesion of melanoma cells to the human dermal microvascular endothelial cells.7 THY1 is a cell surface marker, which has been used to identify local and circulating liver cancer stem cells. 8,9 Nasopharyn...

Multiple roles of CD90 in cancer

“…This loss of tumorigenicity during overexpression of CD90 was attributed to G0/G1 cell cycle arrest in HONE1 cells. When CD90 expression was inhibited by shRNA in HONE1 cells that were made non-tumorigenic, tumorigenicity was restored [60] clearly linking CD90 to a tumor-suppressive role also in nasopharyngeal carcinoma (Fig. 1a).…”

“…When an intact copy of chromosome 11 which carries CD90 gene was introduced into highly tumorigenic HONE1 cells through microcell mediated chromosome method, tumor-forming ability in the mouse was suppressed (14 out of 30 mice) or delayed (16 out of 30 mice) [17]. Similarly, Lung et al in their two separate studies observed that when CD90 expression was re-introduced into HONE1 cells through a tetracycline-inducible system, there was a significant reduction in the colony forming ability of the cells in vitro [59] and suppression of tumor formation in nude mice in vivo (8 out of 18 sites injected did not form tumors) [60]. The number of colonies as well as the colony size was reduced during CD90 expression, and invasion through matrigel was inhibited.…”

“…On the contrary, the prognostic value of CD90 is not similar in all cancer types as CD90 downregulation was associated with poor prognosis, survival, or disease progression in ovarian adenocarcinoma [16,18,50,51,53], nasopharyngeal carcinoma [59,60], and neuroblastoma [61,62]. In these cancers, CD90 was found to have a tumor suppressor effect and reconstitution of CD90 in non-expressing cancer cells limited their proliferation and tumor-forming ability.…”

Catalytic activity of matrix metalloproteinase‐19 is essential for tumor suppressor and anti‐angiogenic activities in nasopharyngeal carcinoma

“…35 This has been reported in previous studies in which repression of gene expression by dox is not absolute and leakage of transgene expression, especially in vivo, can occur. 31,36,37 Despite reduction of MMP19 in MMP19 C7 and C14 (þdox) in vivo, the levels of MMP19 expressed were still sufficient to suppress tumor formation in nude mice.…”

A CD90+ Tumor-Initiating Cell Population with an Aggressive Signature and Metastatic Capacity in Esophageal Cancer

“…Stable clones were selected using neomycin (11). For CD90 knockdown, 3 pairs of CD90 short hairpin RNA (shRNA) oligonucleotides were designed by BLOCK-iT RNAi designer program, as previously described (12). These oligonucleotides target positions 78-99, 298-117, and 301-321 of the human CD90 cDNA (NM_006288).…”