Telomere dynamics and genome stability in the human pancreatic tumor cell line MIAPaCa-2.

Telomeres are specialized structures found at the ends of eukaryotic chromosomes serving as guardians of genome stability. In normal cells telomeres shorten with each cell division, but immortal cells undergoing multiple divisions constantly have to maintain telomere lengths above a critical level. This is accomplished either through expression of telomerase or the alternative recombination pathway (ALT). In the present study, we analyzed telomere dynamics of the telomerase positive human pancreatic tumor cell line MIAPaCa-2. The cells demonstrated genomic instability with a high frequency of chromosomal aberrations resulting in differences between individual karyotypes within the same cell population. The telomeres were short when compared with normal human fibroblasts, and about 39% of the chromosome ends did not have detectable telomere repeats as demonstrated by PNA-FISH. In many cases telomere signals were missing even when sister chromatids were strongly labeled. In addition, we used an internal PNA probe specific for the X chromosome, present in a single copy in these cells, in order to follow telomere dynamics on individual chromatids. High heterogeneity in telomere signals among individual X chromosomes as well as between their sister chromatids suggested sudden and stochastic loss or gain of telomere repeats. Such constant genomic instability often results in apoptosis and death of a fraction of cells present in the culture at all times. We discuss possible molecular mechanisms that may explain this observed telomere heterogeneity and possible adaptive repair mechanisms by which these cells maintain their chromosomes in order to survive such extreme and permanent genomic instability.

Conservative surgical treatment of low-grade urothelial carcinoma in the renal allograft recipient: a case report.

Development of urothelial carcinoma in a renal allograft is rare. We report the case of 52-year-old male patient who developed chronic renal failure secondary to Balkan endemic nephropathy and underwent renal allotransplantation. The patient who developed low-grade pTa urothelial carcinoma in the left contracted kidney at 3 years after transplantation and underwent nephroureterectomy. Three years later, the same neoplastic process was observed in the renal allograft. Preoperative estimation for allograft tumor recurrence and progression included percutaneous tumor biopsy followed by cytopathological, histological, and cytogenetic analysis. Cytopathology revealed well-differentiated urothelial tumor cells. Histopathologic analysis showed low-grade urothelial carcinoma. Cytogenetic examination demonstrated that the tumor originated from the recipient suggesting a low malignant potential of carcinoma. Based on these findings, we decided to perform a right-side nephroureterectomy and graft-sparing procedure, which resulted in preservation of allograft function. In this report we discussed the prognostic factors, which are the basis for rational therapeutic approaches in these patients.

IgH and TCRgamma gene rearrangements, cyclin A1 and HOXA9 gene expression in biphenotypic acute leukemias.

In this study we investigated IgH and TCRgamma gene rearrangements, cyclin A1 and HOXA9 gene expression as well as the in vitro growth of biphenotypic acute leukemia (BAL) blasts in relation to acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). The aim of the study was to correlate BAL morphology and its biological parameters in order to get information that might be used for additional stratification of BAL. This rare form of AL was identified in a total of 10 patients, comprising 4.3% of adult and 3.0% of pediatric patients with de novo AL referred to our institution during the 1999-2003 period. Our results indicate that IgH and TCRgamma gene rearrangements correlated well with lymphoid BAL morphology, whereas the expression of cyclin A1 correlated with myeloid and undifferentiated BAL morphology. Surprisingly, HOXA9 expression, a marker associated with myeloid cell lineage, showed no strong correlation with BAL morphology. Finally, in vitro growth of blasts during a 7-day culture showed autonomous cell growth in 3/10 AML and 3/8 myeloid BAL samples tested, but not in any of the AL with lymphoid features. Further studies are needed to confirm these findings and to extend research to a broader spectrum of cell markers.