Molecular characterization of permanent cell lines from primary, metastatic and recurrent malignant peripheral nerve sheath tumors (MPNST) with underlying neurofibromatosis-1.

Malignant peripheral nerve sheath tumors (MPNSTs) develop in patients with underlying NF1, and usually arise as a result of malignant transformation of a pre-existing plexiform neurofibroma. The clonal cytogenetic abnormalities reported in primary MPNST include complex karyotypes with chromosome numbers in the triploid or tetraploid range with recurrent abnormalities of several chromosomes including losses or imbalances. As a prelude to cell biological, pharmacological, and functional studies to investigate pathways and gene(s) associated with multistep tumorigenesis, which includes progression, metastasis and resistance to therapy in MPNST, detailed molecular cytogenetic and genetic analyses of cell lines from primary, metastatic and recurrent MPNST with underlying NF1 disorder have been performed. The clonal cytogenetic abnormalities detected in the primary tumor cell line were similar to those observed in primary cultures of this tumor. Due to the complexity of the rearrangements seen by G-banded karyotype analysis, further characterization of the clonal abnormalities in these three cell lines was performed by molecular cytogenetic techniques, including CGH and SKY. CGH analysis detected recurrent deletions of 9p, 12q21-q32, complete losses of the X-chromosome, and gains of the chromosomal segment 17q25 in all three cell lines. SKY analysis detected extensive clonal abnormalities in these cell lines. The nature and the alterations of the cell cycle regulators, particularly those associated with G1-S checkpoints and known to be deregulated in MPNST, were studied. These cell cycle regulators included those associated with Rb1-cyclin D1 and the p53 pathways. The findings are consistent with the argument that an imbalance between the cyclin activators of CDKs and inhibitory proteins such as p16 result in uncontrollable proliferation in the cell lines, associated with progression of the disease. LOH and expression of the p53 gene in metastatic and recurrent cell lines was observed, as reported by others. The role of biallelic inactivation of p53 gene in MPNST with underlying NF1 mutations, however, needs further study. Overexpression of Rb1-protein observed in metastatic and recurrent cell lines is indicative of its role in the progression of the disease. One of the most important observations of this study is that Nm23-H1 expression is closely associated with advanced or metastatic disease. In summary, MPNST cell lines derived from a patient with metastatic and recurrent disease with NF1 disorder were characterized and a gene associated with metastatic potential which is amenable to therapeutic and chemo-preventative approaches was identified. These cell lines with extensive characterization of genetic abnormalities are likely to provide important reagents for biochemical, molecular and pharmacological studies related to MPNST.

Genetic abnormalities in non-Hodgkin's lymphoma as revealed by conventional and molecular cytogenetics methods of analyses.

Malignant non-Hodgkin's lymphoma (NHL) is a heterogeneous group of tumors, the histological classification of which based on morphologic evaluation alone is not always possible. Various technological advances in cytogenetics combined with molecular approaches have greatly enhanced our ability to identify genetic abnormalities in any given tumor type. The genetic abnormalities identified with the combination of these methods of analysis have resulted in various histological subtypes of NHL being linked with specific genetic abnormalities. Such a classification based on specific abnormalities has lead to the realization that the same abnormalities associated with initiation, transformation, and progression of the disease have also served as markers of diagnosis, prognosis, and predisposition to a given tumor type, and some abnormalities also served as markers for therapeutic targets. Results of such studies in NHL have not only identified the subsets of various histological types based on specific abnormalities, but, as is evident from recent literature, also set the stage for further evaluation using high-resolution array comparative genomic hybridization (CGH) and expression profiling.

ALK-positive diffuse large B-cell lymphoma with the t(2;17)(p23;q23).

Diffuse large B-cell lymphoma (DLBCL) with plasmablastic features associated with t(2;17)(p23;q23) and characteristic granular cytoplasmic anaplastic lymphoma kinase-1 (ALK1) protein expression is a rare lymphoma subtype. Nodal and extranodal involvement has been reported. Our case is a 32-year-old man with right cervical adenopathy. Lymph node biopsy showed large atypical cells with prominent plasmablastic differentiation, abundant amphophilic cytoplasm, and prominent central nucleoli. Paraffin immunohistochemistry showed finely granular cytoplasmic ALK1 expression, positive CD138, IgA, p63 (VS38), focal positive epithelial membrane antigen and CD4, and lambda light chain restriction whereas negative CD20 and CD30 staining. While reports show detection of the unique CLTC-ALK fusion by either reverse transcription-polymerase chain reaction or fluorescence in situ hybridization, our case represents the second case in the literature to detect the t(2;17)(p23;q23) translocation by multiplex karyotyping (multiplex fluorescence in situ hybridization) and the usefulness of this technique to detect hidden translocations not seen by G-banding. An add(2)(p23) was also seen not previously reported. Differential diagnoses of neoplasms with plasmablastic differentiation and a comprehensive molecular/cytogenetic literature review of ALK+DLBCL is discussed.