Modulation of invasive potential in different clonal subpopulations of a rat rhabdomyosarcoma cell line (BA-HAN-1) by differentiation induction

In vitro invasiveness of human epithelioid-sarcoma cell lines: association with cell motility and inverse correlation with the expression of tissue inhibitor of metalloproteinases

Epithelioid sarcoma (ES) is a very aggressive soft-tissue tumor in vivo, but no experimental data on its invasive and metastatic behavior have been reported. In the present study, 3 different clonal sub-populations (GRU-1A, GRU-1B and GRU-1C), derived from the same human ES cell line, GRU-1, were investigated for in vitro invasiveness in relation to migration, adhesion and the expression of different invasion- and metastasis-related genes. Tumor spheroids of GRU-1A were markedly more invasive in the chick-heart invasion assay (CHIA) than spheroids of GRU-1B and GRU-1C. These results were paralleled by a significantly higher cell motility of GRU-1A than GRU-1B and GRU-1C (p < 0.05) on distinct substrates, suggesting that the observed differences in invasion result at least in part from differences in motility. When invasion was assayed with suspended tumor cells in the Matrigel assay, differences between the 3 cell lines were much more pronounced than in the CHIA, where cell-cell contacts are established. These results indicate that interclonal differences in ES invasion result mainly from differences in motility, but also partly depend on differences in cell-cell adhesion. On the molecular level, low invasive potential was associated with over-expression of distinct tissue inhibitor of metalloproteinases (TIMPs) relative to matrix metalloproteinase-2 and -9. However, no association was found between invasion and the expression of CD44 splicing variants or nm23 isoforms. Our results suggest that differences in invasion between GRU-1A, GRU-1B and GRU-1C are caused mainly by interclonal differences in migration, and might result from differences in the expression of distinct TIMPs.

Differentiation markers and invasiveness: discordant regulation in normal trophoblast and choriocarcinoma cells

In tumor cells, malignant (invasive) behavior and differentiation tend to be correlated inversely, although it is not clear to what extent this can be generalized and whether it may also apply to normal invasive cell types. We have modulated differentiation of normal trophoblast cells from first trimester or term placenta as well as choriocarcinoma cells (BeWo, Jeg-3, and JAr) with retinoic acid (RA), methotrexate (MTX), dibutyryl-cAMP (dbcAMP), or phorbol-[12-myristoyl-13-acetyl]-diester (PMA). The secretion of the differentiation marker chorionic gonadotrophin was stimulated by nearly all substances in all cell types. The activity of cellular sterylsulfatase showed a tendency to be increased (decreased by RA and dbcAMP in normal trophoblast; not detected in JAr). Invasiveness was decreased by all effectors in normal trophoblast (both types) and in BeWo. In Jeg-3 and JAr, however, PMA treatment (in JAr also RA treatment) increased invasion rates. These results suggest that only in normal trophoblast and in BeWo (but not in other choriocarcinoma cells, i.e., Jeg-3 and JAr) invasiveness and differentiation tend to be correlated inversely. When extrapolating to the various subpopulations of cells within a tumor, induction of differentiation-as intended in certain strategies for tumor therapy ("differentiation therapy")-may have the unwanted effect of stimulating invasiveness in certain subpopulations of tumor cells.

Growth inhibition in clonal subpopulations of a human epithelioid sarcoma cell line by retinoic acid and tumour necrosis factor alpha

Epithelioid sarcoma is a highly malignant soft tissue tumour that is refractory to conventional chemotherapy and irradiation. Since permanent cell lines of this tumour are extremely rare, in vitro data on compounds with significant antiproliferative effects are still lacking. Therefore, we investigated the effects of retinoic acid (RA) and tumour necrosis factor alpha (TNF-alpha) on tumour cell proliferation of three different clonal subpopulations (GRU-1A, GRU-1B, GRU-1C) derived from the same human epithelioid sarcoma cell line, GRU-1. In GRU-1A both RA (P=0.01) and TNF-alpha (P=0.002) exhibited highly significant and dose-dependent growth inhibitory effects, which could further be increased by a combined application of both compounds (P<0.006). GRU-1B proved to be sensitive to RA (P=0.006), whereas no response to TNF-alpha was observed. GRU-1C was resistant to both RA and TNF-alpha. The antiproliferative effect of TNF-alpha was mediated by TNF receptor 1(TNF-R1) and correlated positively with both the number of TNF-R1 per cell and receptor affinity. No correlation was detected between RA-induced growth inhibition and the expression pattern of the RA receptors (RARs) RAR-alpha, RAR-beta, and RAR-gamma. Plating efficiency, however, could exclusively be reduced by RA in GRU-1B, the only cell line expressing RAR-alpha. Taken together, these data are the first showing significant antiproliferative effects in human epithelioid sarcoma by RA and TNF-alpha. Whereas the TNF-alpha response seems to depend on the expression of TNF-R1, no simple correlation could be found between RA sensitivity and the expression pattern of RARs.

Activation of the E-cadherin/catenin complex in human MCF-7 breast cancer cells by all-trans-retinoic acid

All-trans-retinoic acid (RA), like insulin-like growth factor I (IGF-I) and tamoxifen, inhibit invasion of human MCF-7/6 mammary cancer cells in vitro. For tamoxifen and for IGF-I, activation of the invasion-suppressor function of the E-cadherin/catenin complex was shown to be the most probable mechanism of the anti-invasive action. We did a series of experiments to determine whether the anti-invasive effect of RA also implicated the invasion-suppressor E-cadherin/catenin complex. Human MCF-7/6 mammary and HCT-8/R1 colon cancer cells, both with a dysfunctional E-cadherin/catenin complex, were treated with RA and the function of the complex was evaluated through Ca(2+)-dependent fast aggregation. Fast aggregation of both MCF-7/6 and HCT-8/R1 cells was induced by 1 microM RA. This effect was abolished by antibodies against E-cadherin. RA-induced fast aggregation was not sensitive to cycloheximide, tyrosine kinase inhibitors or antibodies against IGF-I or against the IGF-I receptor. RA did not stimulate IGF-I receptor phosphorylation or alter the E-cadherin/catenin complex, as evidenced by immunoprecipitation. RA up-regulates the function of the invasion-suppressor complex E-cadherin/catenin. Its action mechanism is different from that of IGF-I. RA may act as an anti-invasive agent with unique mechanisms of action.

Are fibroblast growth factors regulators of myogenesis in vivo?

Recent advances in understanding of skeletal muscle differentiation implicate fibroblast growth factors (FGFs) as regulators of myogenesis; however, the identity and actions of factors that repress myogenesis in vivo remain to be established. This review will focus on the fibroblast growth factor family and the evidence for its role in regulating myogenesis in culture and in vivo.