Promoter CpG hypermethylation and downregulation of DICE1 expression in prostate cancer.

A critical region of loss of heterozygosity on human chromosome 13q14 harbors the tumor suppressor gene DICE1 (DDX26). To elucidate the reduced DICE1 expression in tumor cells, the putative promoter sequence upstream of the DICE1 gene was analysed. This sequence shows a high GC content and is rich in CpG sites and binding sites of transcriptional factors. Promoter activity was identified within three overlapping fragments of the 800 bp sequence upstream of the DICE1 gene. A 13 bp deletion polymorphism detected in the DICE1 promoter region showed a decreased activity compared with the undeleted variant. However, this 13 bp deletion was seen in male control samples and patients with prostate cancer or benign prostatic hyperplasia at similar rates. A reduced DICE1 expression was observed in prostate cancer cell lines DU145 and LNCaP. This downregulation is associated with hypermethylation of the DICE1 promoter. Treatment of both prostate cancer cell lines with 5-azacytidine leads to upregulation of DICE1 expression. Hypermethylation of CpG sites of the DICE1 promoter was observed in four of eight analysed prostate cancers. This study suggests that transcriptional repression of DICE1 is caused by hypermethylation of the DICE1 promoter region in prostate cancer cells.

Re-analysis of the cell line NALM-1 karyotype by GTG-banding, spectral karyotyping, and whole chromosome painting.

Chronic myelogenous leukemia (CML) is a clonal bone marrow disease with progression from a chronic phase to an aggressive blast crisis. The cell line NALM-1 was originally established by Minowada and coworkers from the peripheral blood of a patient in CML blastic crisis. A karyotype analysis of the NALM-1 cell line was performed in the 1970s. To the best of our knowledge, this karyotype was not re-analyzed by molecular cytogenetic techniques, although this cell line is the source of many molecular investigations including expression studies. To establish this cell line as a CML control in our own laboratory, NALM-1 was analyzed by GTG banding, fluorescence in situ hybridization, and spectral karyotyping. Our results differ from the original publication of Sonta and coworkers. We describe for the first time the karyotype of the NALM-1 cell line: 44,X,-X,der(7)t(7;9;15)(q10;?;q15),der(9)t(9;9)(p24;q33 approximately q34)t(9;22)(q34;q11),der(15)t(7;9;15) (?;?;q15),der(22)t(9;22)(q34;q11).

Sex chromosomal mosaicism in the gonads of patients with gonadal dysgenesis, but normal female or male karyotypes in lymphocytes.

OBJECTIVES: In most cases, XX or XY gonadal dysgenesis remains genetically unexplained. In this pilot study we searched for sex-chromosomal mosaicism in gonads of patients with XX or XY gonadal dysgenesis of undetermined origin. STUDY DESIGN: Gonadal tissues were analyzed by cytogenetic and interphase fluorescence in-situ hybridization (FISH) analyses in four patients with gonadal dysgenesis and normal female (46,XX) or male (46,XY) karyotypes in lymphocytes. RESULTS: Cytogenetic and FISH analyses of the gonads demonstrated in three patients a sex-chromosomal mosaicism. Cytogenetic analysis of gonadal tissue of the fourth patient confirmed the result of the lymphocytes with 46,XX, but FISH analysis revealed in 17% of nuclei only one X-chromosome. CONCLUSION: Our data indicate that sex-chromosomal mosaicism in gonads may be a frequent cause of gonadal dysgenesis despite of normal karyotypes in lymphocytes. Therefore, cytogenetic and FISH analyses of gonadal tissue can provide important information in unexplained cases of gonadal dysgenesis.