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.     

Temporary remission of an alveolar rhabdomyosarcoma diagnosed and treated as acute leukemia

A 29-year-old man with alveolar rhabdomyosarcoma was considered to be suffering from acute leukemia. A bone marrow aspirate had revealed extensive infiltration by atypical blast-like cells which were interpreted as acute lymphoblastic leukemia. Although there was no confirmation of this diagnosis by immunophenotyping chemotherapy with a protocol suited for the treatment of acute lymphoblastic leukemia was started prior to histological analysis and resulted in a complete temporary remission after the first cycle. Histological analysis of a bone marrow biopsy revealed an alveolar rhabdomyosarcoma, as further confirmed by molecular genetic analysis. Two months after the end of chemotherapy, there was an extensive recurrence and the patient died one year after initial diagnosis with chemotherapy refractory disease. In conclusion, rhabdomyosarcoma should always be included in the differential diagnosis of systemic diseases with extensive bone marrow infiltration by tumor cells which could otherwise be misinterpreted as a haematological malignancy.     

Penile metastasis secondary to follicular thyroid carcinoma

Penile metastases are rare and are considered to reflect end-stage malignant disease. The first case of a follicular thyroid carcinoma metastasizing to the penis is described. Local tumor control and probably enhanced survival was achieved by extended surgery of a previous pelvic recurrence and the penile metastasis and this procedure may be justified in selected cases.     

Decrease of DNA methyltransferase 1 expression relative to cell proliferation in transitional cell carcinoma

In many common cancers such as transitional cell carcinoma (TCC), specific genes are hypermethylated, whereas overall DNA methylation is diminished. Genome-wide DNA hypomethylation mostly affects repetitive sequences such as LINE-1 retrotransposons. Methylation of these sequences depends on adequate expression of DNA methyltransferase I (DNMT1) during DNA replication. Therefore, DNMT1 expression relative to proliferation was investigated in TCC cell lines and tissue as well as in renal carcinoma (RCC) cell lines, which also display hypomethylation, as indicated by decreased LINE-1 methylation. Cultured normal uroepithelial cells or normal bladder tissue served as controls. In all tumor cell lines, DNMT1 mRNA as well as protein was decreased relative to the DNA replication factor PCNA, and DNA hypomethylation was present. However, the extents of hypomethylation and DNMT1 downregulation did not correlate. Reporter gene assays showed that the differences in DNMT1 expression between normal and tumor cells were not established at the level of DNMT1 promoter regulation. Diminished DNMT1:PCNA mRNA ratios were also found in 28/45 TCC tissues but did not correlate with the extent of DNA hypomethylation. In addition, expression of the presumed de novo methyltransferases DNMT3A and DNMT3B mRNAs was investigated. DNMT3B overexpression was observed in about half of all high-stage TCC (DNMT3B vs. tumor stage, chi(2): p = 0.03), whereas overexpression of DNMT3A was rarer and less pronounced. Expression of DNMT3A and DNMT3B in most RCC lines was higher than in TCC lines. Our data indicate that DNMT1 expression does not increase adequately with cell proliferation in bladder cancer. This relative downregulation probably contributes to hypomethylation of repetitive DNA but does not determine its extent alone.