[Southern blot hybridization analysis for lymphoid neoplasms]

The recent remarkable progress of molecular biology gave us new tools for examination of the etiology and pathology of many diseases. Hence, the introduction of such techniques in our clinical laboratory area is becoming more important and indispensable year by year. In addition to morphological and phenotypical analysis, we are now establishing a molecular diagnosis system to support the clinical diagnosis of hematological malignancies. In the present study, we show our ongoing results focusing on adult T-cell leukemia(ATL). Southern blot analysis for detection of the monoclonal integration of HTLV-I proviral genome, a causative agent of ATL, was performed using digoxigenin-labeled probe. The sensitivity was equivalent to RI-labeled probe and was enough for clinical use. We are also doing Southern blot analysis for immunoglobulin heavy chain gene and T-cell receptor beta chain gene as custom service for the diagnosis of B-lymphoproliferative disorders and non-ATL T-lymphoproliferative disorders. We are reporting such results to the clinical site with our interpretation. Since the band size of the HTLV-I provirus obtained by Southern blot differed in each case and was sometimes smaller than the size of the complete virus, we further analyzed the structure of HTLV-I using long and accurate PCR(LA-PCR) and sequence-target-site PCR(STS-PCR). We found that the integrated HTLV-I provirus is divided into two subtypes, complete virus and defective virus. The incidence of defective virus was high in acute-type ATL compared with that in chronic- or lymphoma-type ATL. Although there are several difficulties in introducing such molecular analyses into the clinical laboratory area, we think that the need is increasing together with the progression of gene therapy and evidence-based medicine.