Diagnostic markers demonstrating successful culture of human meningioma cells.

The light microscopic and ultrastructural features of cultured meningioma cells were compared with those of surgically resected specimens. Meningioma cells normally show variable degrees of epithelial or mesenchymal differentiation. In cultured cells, well formed psammoma bodies and whorls were seen by light microscopy and specialised intercellular junctions were observed by electron microscopy. Cytogenetic analysis was also shown to be a useful diagnostic marker to differentiate cultured meningioma from contaminant proliferating fibroblastic and endothelial cells. These methods have demonstrated that the cells cultured from operative samples were predominantly meningioma cells. The ability to reproducibly cultivate populations of meningioma cells should facilitate in vitro assessment of potential adjunctive treatment modalities.

Mosaicism with a normal cell line and an autosomal structural rearrangement.

Over three decades, 12 cases of mosaicism for an autosomal rearrangement were recognised in the major cytogenetics laboratories in New Zealand, eight of which were studied between 1990 and 1992. One case inferentially involved the gonad, eight the soma, and three both gonad and soma. This mosaicism could have arisen as a postzygotic event either in a conceptus that was initially normal, with the generation of an abnormal cell line, or in a conceptus having a supernumerary chromosome which was lost at a subsequent mitosis, thereby restoring a normal cell line. Three of the 12 cases involved a presumed direct duplication, an otherwise very uncommon rearrangement. This may indicate a propensity for direct duplications to arise at mitosis rather than at meiosis; unequal sister chromatid exchange is a plausible mechanism. Mosaicism has clinical relevance for genetic counselling, as an intragonadal cell line carrying a rearrangement could generate multiple unbalanced gametes. Mosaicism for an autosomal rearrangement my be very much more common that is, or ever could be, recognised.

Radiosensitivity of new and established human melanoma cell lines: comparison of [3H]thymidine incorporation and soft agar clonogenic assays.

Seven new low-passage melanoma lines were developed in this laboratory from clinical melanoma specimens and characterised for chromosome complement, DNA ploidy and S-phase content. The radiosensitivity of these lines was compared with that of eight established melanoma cell lines, FME, MM-96, SK-MEL-5, SK-MEL-28, SK-MEL-2, MALME-3M, M19-MEL and LOX-IMVI, using a 96-well microculture assay technique. Dose-response curves were determined using a 5-day incubation period and 6-h terminal [3H]thymidine-labelling period. Radiation (60Co source) was carried out under a lead wedge to provide a radiation dose range of 0-10 Gy, or by irradiating part of the plate (radiation dose 0 or 2 Gy). Data for a range of cell densities in a single 96-well plate were combined into a single regression equation incorporating linear quadratic terms for radiation dose and cell density. SF2 values were defined as the amount of thymidine incorporated following a radiation dose of 2 Gy, expressed as a fraction of that of unirradiated cells, and varied from 0.36 to 0.93. The reproducibility in repeat assays, as defined by the standard error of determinations at different passage numbers, was +/- 0.04. The newly developed lines exhibited a similar range of radiosensitivity to that of the established lines, and melanin content did not correlate with resistance. For nine of the lines, radiation parameters were also determined using a modified Courtenay clonogenic soft agar assay technique, and the results compared with the thymidine incorporation results, and a significant linear correlation was found between SF2 and SF2' (r = 0.89). The linear (alpha) and quadratic (beta) terms of the best-fit linear quadratic dose-response curves, were significantly correlated between the two assays. It is concluded for this series of human melanoma lines that proliferation assays in 96-well plates provide radiosensitivity parameters comparable to those using clonogenic assays.

Deletion of the long arm of chromosome 20 in a patient with small cell lymphocytic lymphoma.

Cytogenetic analysis of bone marrow from an 80-year-old woman with small cell lymphocytic lymphoma revealed a del(20)(q11.2) as the sole cytogenetic abnormality. Del(20q) is found almost exclusively in myeloid disorders and this case represents a rare occurrence in a non-myeloid disorder.

Myelodysplastic syndrome and trisomy 14q.

Trisomy 14 as a sole karyotypic abnormality in neoplasia is extremely rare. In hematologic disorders, 18 cases have been reported so far, 17 of which involved disorders of the myeloid lineage. Five were cases of myelodysplastic syndrome (MDS), and a further four involved Philadelphia-negative atypical chronic myeloid leukemia. The case presented here is the second case of trisomy 14q in MDS involving the chronic myelomonocytic leukemia subtype. There were certain features in common with some of the previously reported cases. We raise the possibility that this represents a specific entity.