Detection of clonal T cells in cutaneous T cell lymphoma by polymerase chain reaction: Comparison of mutation detection enhancement‐polyacrylamide gel electrophoresis, temperature gradient gel electrophoresis and fragment analysis of sequencing gels

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Abstract
Cutaneous T cell lymphomas (CTCL) can be differentiated from benign inflammatory dermatoses by the demonstration of clonal T cells in skin biopsy. As a marker of the T cell clonality, the rearrangement of the T cell receptor (TCR) genes is amplified by polymerase chain reaction (PCR) and subsequently analyzed by several electrophoresis techniques. Since the validity of this approach depends substantially on the separating capacity of the applied electrophoresis technique, we investigated in the present study the lower detection limit and the sensitivity of heteroduplex‐loaded polyacrylamide gel electrophoresis on MDE® (mutation detection enhancement) gels (HD‐MDE PAGE), of heteroduplex‐loaded temperature gradient gel electrophoresis (HD‐TGGE) and fragment analysis (FA) on sequencing gels. Genomic DNA from formalin‐fixed, paraffin‐embedded skin biopsies of 53 CTCL specimens and 27 samples of benign dermatoses was analyzed by TCRy PCR followed by electrophoretic separation. Clonality was detected by HD‐MDE PAGE in 22, by HD‐TGGE in 34, and by FA in 33 of the 53 CTCL cases. Additionally, FA revealed an oligoclonal fragment profile in seven CTCL specimens. In the 27 samples from benign dermatoses, HD‐MDE PAGE and HD‐TGGE showed the expected polyclonal pattern in 26, and FA in 25 specimens. HD‐TGGE and FA detected a clonal pattern down to a dilution of 103 monoclonal cells in 106 peripheral blood mononuclear cells (PBMC), while HD‐MDE PAGE revealed a detection limit of 104 monoclonal cells in 106 PBMC. In conclusion, HD‐TGGE and FA possess a higher sensitivity and lower detection limit than HD‐MDE PAGE. Therefore, both former techniques are useful tools for the routine diagnostic procedure. With regard to time and cost, we recommend HD‐TGGE.

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