metallothionein and Carcinoma--Embryonal

Data concerning the involvement of elevated metallothionein (MT) expression in drug resistance are obviously scattered and contrasting. The presence of the MT gene product protein was screened in 51 untreated human germ cell testicular tumours, furthermore a relationship between MT expression and clinical resistance was investigated. Using monoclonal antibody and immunoenzyme staining elevated MT level could be demonstrated in nuclei and cytoplasm of both seminomas and non seminomatous germ cell testis tumours. Thirty-one tumours (61%) showed extensive, 15 (29%) focal positive staining. In contrast teratomas expressed this antigen negatively or scarcely. The highest level of MT was stated in early stages (I, IIA) compared with progressed stages (IIB, III) (p = 0.0004). Between the high level of MT and clinical resistance a converse correlation could be shown because the resistant tumours expressed no or low, while the sensitive tumours significantly high level of MT protein which can be used as an useful marker to identify patient subgroups sensitive to anticancer therapy, at least in testis tumours.

Topics: Antineoplastic Combined Chemotherapy Protocols; Carcinoma, Embryonal; Gene Expression; Germinoma; Humans; Immunohistochemistry; Male; Metallothionein; Neoplasm Staging; Seminoma; Testicular Neoplasms

Testicular cancer is highly curable with cisplatin-based therapy, and testicular cancer-derived human embryonal carcinoma (EC) cells undergo a p53-dominant transcriptional response to cisplatin. In this study, we have discovered that a poorly characterized member of the death-associated protein family of serine/threonine kinases, STK17A (also called DRAK1), is a novel p53 target gene. Cisplatin-mediated induction of STK17A in the EC cell line NT2/D1 was prevented with p53 siRNA. Furthermore, STK17A was induced with cisplatin in HCT116 and MCF10A cells but to a much lesser extent in isogenic p53-suppressed cells. A functional p53 response element that binds endogenous p53 in a cisplatin-dependent manner was identified 5 kb upstream of the first coding exon of STK17A. STK17A is not present in the mouse genome, but the closely related gene STK17B is induced with cisplatin in mouse NIH3T3 cells, although this induction is p53-independent. Interestingly, in human cells containing both STK17A and STK17B, only STK17A is induced with cisplatin. Knockdown of STK17A conferred resistance to cisplatin-induced growth suppression and apoptotic cell death in EC cells. This was associated with the up-regulation of detoxifying and antioxidant genes, including metallothioneins MT1H, MT1M, and MT1X that have previously been implicated in cisplatin resistance. In addition, knockdown of STK17A resulted in decreased cellular reactive oxygen species, whereas STK17A overexpression increased reactive oxygen species. In summary, we have identified STK17A as a novel direct target of p53 and a modulator of cisplatin toxicity and reactive oxygen species in testicular cancer cells.

Topics: Animals; Antineoplastic Agents; Apoptosis Regulatory Proteins; Carcinoma, Embryonal; Cell Line, Tumor; Cisplatin; Drug Resistance, Neoplasm; Gene Knockdown Techniques; Humans; Male; Metallothionein; Mice; NIH 3T3 Cells; Protein Serine-Threonine Kinases; Reactive Oxygen Species; Response Elements; Species Specificity; Testicular Neoplasms; Tumor Suppressor Protein p53

Murine embryonal carcinoma cells have been used in in vitro models to study the effects of cadmium chloride on proliferation and differentiation of early embryonic cells. This approach allows the various cell types within the early embryo as well as several developmental mechanisms to be dissected and studied in isolation using larger numbers of cells than would be readily available from the embryo itself. The present study shows that both embryonal carcinoma cell proliferation and differentiation into parietal endoderm are inhibited by cadmium chloride. The effects are counteracted by the additional presence of zinc chloride. The uptake of cadmium into the cells is inhibited in the presence of zinc chloride, suggesting that competition between these metals for passage into the cells contributes to the mechanism underlying the protective effect of zinc. In addition, metallothionein gene expression is enhanced more rapidly after simultaneous incubation with zinc chloride, indicating that the attenuating effect of zinc on cadmium toxicity is also partly attributable to detoxification by metallothioneins.

Topics: Animals; Cadmium; Carcinoma, Embryonal; Cell Differentiation; Cell Division; Depression, Chemical; Endoderm; Gene Expression Regulation, Neoplastic; Laminin; Metallothionein; Mice; Neoplasm Proteins; Tumor Cells, Cultured; Zinc