Single cell PCR for the analysis of Hodgkin's disease: four years later

Molecular morphology of Hodgkin lymphoma

No other disease entity has provided greater impetus for the development of the concept of "molecular morphology" than Hodgkin lymphoma. Efforts to understand the etiology of this enigmatic disease have stimulated the application and refinement of almost every mode of biomedical scientific exploration. Notwithstanding the vast amount of data generated, much is still unknown about this remarkable disease, serving as an ongoing inducement to the development and application of new technologies for the analysis of cells and molecules in a morphologic environment.

Blastic variant of mantle cell lymphoma following interfollicular Hodgkin's lymphoma

Infrequently, patients are diagnosed with Hodgkin's lymphoma and a morphologically distinct lymphoma. While specific subtypes of lymphomas (including Hodgkin's lymphoma) may present diagnostic difficulties, fine needle aspiration biopsy (FNAB) is sometimes useful in the evaluation and classification of these lymphoproliferative processes. We report a case of the blastic variant of mantle cell lymphoma following Hodgkin's lymphoma, interfollicular variant. A 66-year-old woman with a history of Hodgkin's lymphoma presented with increasing contralateral cervical adenopathy three years after receiving chemotherapy. FNAB with ancillary immunophenotypic characterization identified mantle cell lymphoma, blastic variant. Subsequent excisional biopsy confirmed this diagnosis and also aided in the exclusion of recurrent Hodgkin's lymphoma. In addition to identifying the previously unreported combination of blastic variant of mantle cell lymphoma and Hodgkin's lymphoma, this case emphasizes the utility of FNAB in evaluation of new masses in patient's with a previous diagnosis of Hodgkin's lymphoma.

MDM2 gene amplification and lack of p53 point mutations in Hodgkin and Reed-Sternberg cells: results from single-cell polymerase chain reaction and molecular cytogenetic studies

Hodgkin's disease (HD) is the most common haematological malignancy after chronic lymphocytic leukaemia, but very little is known about its pathogenesis or the genetic events that contribute to the malignant phenotype of the tumour cells. p53 is assumed to play an important role in the pathogenesis of HD, based on the observation that p53 protein is frequently accumulated in Hodgkin and Reed-Sternberg (H & RS) cells. We investigated single H & RS cells from five different HD patients for point mutations at the genomic level using multiplex polymerase chain reaction amplification and subsequent sequencing. No point mutations were detected in 50 single H & RS cells analysed. Hence, accumulation of p53 protein cannot be explained by mutations within the gene. A genome-wide screening for genomic imbalances using comparative genomic hybridization revealed gain on chromosome 12q14, i.e. the mapping position of the MDM2 gene in several HD cases. Therefore, we assessed the copy number of the MDM2 gene using fluorescence in situ hybridization. In four out of six HD cases analysed, the copy number of the MDM2 gene was found to be increased. As gene amplification is frequently associated with protein overexpression, the observed accumulation of p53 in the nuclei of H & RS cells could be as a result of elevated MDM2 protein levels resulting in stabilization of p53 protein.

Subtractive hybridization--genetic takeaways and the search for meaning

Gene expression profiling relies on mRNA extraction from defined cell systems, which in the case of pathological processes necessarily results in the use of small quantities of tissues, sometimes as little as a few cells. This obviates the use of many systems of gene expression profiling and is best carried out using cDNA amplified by poly(A) reverse transcription polymerase chain reaction, which is capable of generating material representative of all the expressed genes in samples as small as one cell. Analysis of this material using subtractive hybridization compares the genes expressed at different stages of a biological/pathological process allowing identification of the all the genes upregulated during the process. The identification of the genes present is not dependent on their prior description or on the choice of genes used in a screen and as such the method is ideal for identifying novel genes or unsuspected genes. We have used the method to identify genes involved in normal osteoblastic differentiation and in Paget's disease of bone and it has been widely used to study normal differentiation and pathological processes in a number of systems. The method, its applications and its relationship with the other methods of gene expression profiling are reviewed.

Hodgkin's disease: a disorder of dysregulated cellular cross-talk

Hodgkin's disease (HD) is a peculiar type of human malignant lymphoma characterized by a very low frequency of tumor cells, the so called Hodgkin and Reed-Sternberg (H-RS) cells, embedded in a hyperplastic background of non-neoplastic (reactive) cells recruited and activated by H-RS cells-derived cytokines. H-RS cells can be functionally regarded as antigen-presenting cells (APC) able to elicit an intense, but anergic and ineffective, T-cell mediated immune response along with a hyperplastic inflammatory reaction which involves several cell types including T- and B-cells, neutrophils, eosinophils, plasma cells, fibroblasts and stromal cells. In tissues involved by HD, malignant H-RS cells and their reactive neighboring cells are able to cross-talk via a complex network of cytokine- and cell contact-dependent interactions. As a result of such interactions, mediated by specific surface receptors and adhesion molecules on both tumor and non-neoplastic cells, H-RS cells may receive several proliferative and anti-apoptotic signals favoring the cellular expansion and tumor cell survival in HD. The ineffective T-cell immune response elicited by the abnormal APC function of H-RS cells may further contribute to the biologic and clinical progression of HD. Innovative therapeutic strategies aimed at blocking the pathways of dysregulated cellular cross-talk among H-RS cells and bystander reactive cell populations might be beneficial in the treatment of HD patients.