Autotaxin (ATX), a potent tumor motogen, augments invasive and metastatic potential of ras-transformed cells

Abstract

Autotaxin (ATX), an exo-nucleotide pyrophosphatase and phosphodiesterase, was originally isolated as a potent stimulator of tumor cell motility. In order to study whether ATX expression a ects motility-dependent processes such as invasion and metastasis, we stably transfected full-length ATX cDNA into two nonexpressing cell lines, parental and ras-transformed NIH3T3 (clone7) cells. The e ect of ATX secretion on in vitro cell motility was variable. The ras-transformed, ATX-secreting subclones had enhanced motility to ATX as chemoattractant, but there was little di erence in the motility responses of NIH3T3 cells transfected with atx, an inactive mutant gene, or empty vector. In Matrigel TM invasion assays, all subclones, which secreted enzymatically active ATX, demonstrated greater spontaneous and ATX-stimulated invasion than appropriate controls. This di erence in invasiveness was not caused by di erences in gelatinase production, which was constant within each group of transfectants. In vivo studies with athymic nude mice demonstrated that injection of atx-transfected NIH3T3 cells resulted in a weak tumorigenic capacity with few experimental metastases. Combination of ATX expression with ras transformation produced cells with greatly ampli®ed tumorigenesis and metastatic potential compared to ras-transformed controls. Thus, ATX appears to augment cellular characteristics necessary for tumor aggressiveness.

Identification of molecular subtypes of glioblastoma by gene expression profiling

“…Hierarchical clustering of these tumors based on these 157 genes continued to support the presence of three primary GBM subtypes ( Figure 5). In addition to the previously mentioned genes, the EGFR+ tumors had increased expression of extracellular matrix proteins including tenascin C and fibronectin, which play a role in GBM cell invasion (Ohnishi et al, 1998;Herold-Mende et al, 2002), while the 12q13-15+ group had very high transcript levels of autotaxin, a secreted motility factor that promotes tumor cell invasion and metastasis (Stracke et al, 1992;Nam et al, 2000). These results suggest that these GBM subtypes may differ in their invasion patterns, and suggest additional potential biological, and perhaps clinical differences.…”

Microarray analysis identifies Autotaxin, a tumour cell motility and angiogenic factor with lysophospholipase D activity, as a specific target of cell transformation by v-Jun

“…We believe that the ATX secreted by v-Jun-transformed CEF is also biologically active, since medium conditioned by the transformed cells contains chemotactic activity which, like ATX, is sensitive to pertussis toxin (Stracke et al, 1992;Lee et al, 2002). On the basis of these results, and the known capacity of ATX to enhance tumor progression (Nam et al, 2000), we believe that it is highly likely that ATX contributes to oncogenesis by v-Jun.…”

“…The lysophospholipase D activity of ATX can generate lysophosphatidic acid and sphingosine-1-phosphate from appropriate precursors, and it now seems likely that it is through generation of such signalling lipids that ATX exerts many of its biological effects (Moolenaar, 2002;Umezu-Goto et al, 2002). Since the increase in ATX expression was so striking, and because ectopic expression of ATX markedly enhances the tumorigenicity of Ras-transformed rodent fibroblasts in vivo (Nam et al, 2000), we investigated the relationship between v-Jun and ATX in more detail.…”

“…ATX has been shown to enhance the tumorigenicity of cells which are already transformed by an activated Ras oncogene (Nam et al, 2000) and to stimulate the growth of human cancer cell lines when added to growth medium in soluble form (UmezuGoto et al, 2002). Ectopic expression of ATX alone, however, is not sufficient induce cell transformation or alterations in growth control in normal rodent fibroblasts (Nam et al, 2001), or as we have shown here in primary CEF (Figure 7, and data not shown).…”

“…For example, ATX (107-fold) is a secreted factor that has been shown to stimulate cell motility, invasion, and angiogenesis (Nam et al, 2000(Nam et al, , 2001. The relationship between ATX expression and cell transformation by v-Jun and other oncogenes is investigated in more detail below.…”