title: An approach to the sensitivity of temperature-gradient gel electrophoresis in the detection of clonally expanded T-cells in cutaneous T-cell lymphoma.
abstract: Detection of T-cell clonality by polymerase chain reaction (PCR) and high-resolution electrophoresis facilitates differentiation of early stages of cutaneous T-cell lymphoma (CTCL) from benign T-cell-rich dermatoses. However, data regarding the sensitivity of the various electrophoresis techniques differ remarkably. In the present study, the capacity of heteroduplex (HD)-loaded temperature-gradient gel electrophoresis (TGGE) to detect clonally expanded T-cells was assessed systematically and modifications to the procedure were defined. Using our standard protocol, HD-TGGE detected clonal T-cell receptor (TCR)-gamma PCR products, generated from the Jurkat cell line, down to a total of 2 ng/microL (14 ng) DNA. However, slowly migrating single strands of the clonal PCR product reduced the amount of the clonality indicating homoduplices. To overcome this single-strand formation, thus decreasing the detection limit, the urea concentration in the gel and the temperature ramp for the HD-formation were altered, as well as the temperature gradient in the gel. Application of the modified protocol resulted in a tenfold lower detection limit of 0.15 ng/microL (1.05 ng) DNA in the clonal band. The sensitivity of the adapted HD-TGGE was investigated by dilution experiments using the well established T-cell lines Jurkat, Molt-4, MyLa and SeAx. By these approaches clonal PCR products diluted in nonclonal PCR products were detectable down to concentrations of 5-10%. Comparably, in the case of mixtures of clonal in nonclonal DNA the detection limit reached 5-10% clonal DNA. However, by dilution of clonal cells in nonclonal peripheral blood mononuclear cells, which corresponds to in vivo conditions, a lower detection limit of approximately 1-5% was observed.
authors.affiliation: Department of Dermatology and Allergy, Charité, Humboldt-University of Berlin, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Ahnhudt
authors.forename: J M
authors.initials: JM
authors.lastname: Muche
authors.forename: K
authors.initials: K
authors.lastname: Dijkstal
authors.forename: W
authors.initials: W
authors.lastname: Sterry
authors.forename: A
authors.initials: A
authors.lastname: Lukowsky
mesh_terms: D004273:DNA, Neoplasm / Q000032:analysis*; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods*; D006801:Humans; D019169:Jurkat Cells; D016410:Lymphoma, T-Cell, Cutaneous / Q000235:genetics*; D012680:Sensitivity and Specificity; D013601:T-Lymphocytes; D013696:Temperature
chemical_list: D004273:DNA, Neoplasm