Clonal Disease in Early Cutaneous T-Cell Lymphoma

Molecular Analysis of T-Cell Receptor β Genes in Cutaneous T-Cell Lymphoma Reveals Jβ1 Bias

Molecular characterization of T-cell receptor junctional region sequences in cutaneous T-cell lymphoma had not been previously reported. We have examined in detail the features of the T-cell receptor beta (TCRB) gene rearrangements in 20 individuals with well-defined stages of cutaneous T-cell lymphoma (CTCL) comprising 10 cases with early-stage mycosis fungoides (MF) and 10 cases with late-stage MF or Sezary syndrome. Using BIOMED-2 PCR primers, we detected a high frequency of clonally rearranged TCR gamma and TCRB genes (17/20 and 15/20 cases, respectively). We carried out sequencing analysis of each complete clonal variable (V)beta-diversity (D)beta-joining(J)beta fingerprint generated by PCR amplification, and determined the primary structure of the Vbeta-Dbeta-Jbeta junctional regions. We observed considerable diversity in the T-cell receptor Vbeta gene usage and complementarity-determining region 3 loops. Although we found that TCRB gene usage in CTCL and normal individuals share common features, our analysis also revealed preferential usage of Jbeta1 genes in all cases with advanced stages of disease.

T-cell receptor γ gene rearrangement by multiplex polymerase chain reaction/heteroduplex analysis in patients with cutaneous T-cell lymphoma (mycosis fungoides/Sézary syndrome) and benign inflammatory disease: correlation with clinical, histological and i

BACKGROUND

A dominant T-cell clone can be detected by polymerase chain reaction (PCR) in 40-90% of cutaneous samples from patients with cutaneous T-cell lymphoma (CTCL).

MATERIALS AND METHODS

From 1996 to 2003 we analysed 547 cutaneous biopsies performed to exclude CTCL (mycosis fungoides, MF/Sézary syndrome, SS). The final diagnosis was benign inflammatory disease (BID) in 353 samples (64.5%) and CTCL in 194 (35.5%). T-cell receptor (TCR)-gamma gene rearrangement was studied by using a multiplex PCR/heteroduplex (HD) analysis. The PCR results were correlated with the clinical picture, the histological pattern and the presence of T-cell lineage antigen loss, using univariate and multivariate logistic regression analyses.

OBJECTIVE

To determine the sensitivity and specificity of the multiplex PCR/HD analysis and to identify which are the clinical, histopathological or immunophenotypical features significantly associated with a positive T-cell clonality.

RESULTS

A clonality was demonstrated in 83.5% of CTCL and in 2.3% of BID (P < 0.001). A significantly higher percentage of clonal cases was associated with the cutaneous T-score (71.4% in T1, 76.1% in T2 and 100% in nodular and erythrodermic MF samples) and with the presence of a T-cell lineage antigen loss (93.9% vs. 77.4%). Moreover, clonality was closely related to an increase in the histopathological score (51.3% in the samples with a score < 5, compared with 92% in the lesions with > or = 5). No significant difference in the percentage of clonal cases was found between T1/T2 and T3/T4 lesions with a histopathological score > or = 5. The multivariate logistic regression showed that the density and extent of the cell infiltrate, the degree of epidermotropism and the presence of cytological atypia share an independent predictive value for clonality in T1/T2 samples, even if the highest odds ratios (3.6) were associated with the density of the cell infiltrate. The disease course of T1/T2 patients was analysed according to the PCR findings. All the PCR-negative patients showed a long-standing stable disease course; on the other hand, a disease progression occurred in 12/87 (13.8%) positive patients.

CONCLUSIONS

The multiplex PCR/HD analysis is associated with a high diagnostic accuracy (92.7%) in CTCL patients. The finding of a clonal T-cell rearrangement is more closely associated with the histological pattern (in particular with the density and extent of the cell infiltrate) rather than with the MF cutaneous T-score or immunophenotype.

Minimal residual disease in mycosis fungoides follow-up can be assessed by polymerase chain reaction

BACKGROUND

T-cell receptor (TCR) gene rearrangement analysis, i.e. T-cell clonality, using polymerase chain reaction (PCR) is a routine method used to assess the presence of a cutaneous dominant T-cell clone in mycosis fungoides (MF).

OBJECTIVES

To compare the outcome of cutaneous lesions of MF after treatment with the fate of the cutaneous T-cell clonality, and to determine whether minimal residual disease can be detected in patients in clinical complete remission.

METHODS

Fifty-one patients histologically diagnosed as having MF (17 stage IA, 21 stage IB and 13 stage III) were included in this retrospective study. T-cell clonality was analysed by GC-clamp multiplex PCRgamma-denaturing gradient gel electrophoresis. Every patient had two cutaneous biopsies at least 3 months apart. The second biopsy was performed at the site of a treated lesion.

RESULTS

The presence or absence of a dominant T-cell clone in the skin remained identical in 26 of the 31 (84%) patients with persistent disease. Thirteen patients with a detectable dominant T-cell clone at diagnosis went into complete clinical remission. In nine of these 13 (69%) patients, the T-cell clone was no longer detectable after treatment. The remaining four (31%) patients had an unchanged T-cell clonality.

CONCLUSIONS

The TCR gene rearrangement imprint is a stable and reliable tumour marker of MF disease. One-third of patients in complete clinical remission had a cutaneous molecular residual disease, the prognostic value of which will be analysed in an ongoing prospective study.

PCR-heteroduplex analysis of T-cell receptor gamma gene rearrangement in paraffin-embedded skin biopsies

We developed a rapid, simple, and sensitive method for the detection of T-cell receptor-gamma (TCRgamma) gene rearrangements in paraffin-embedded skin biopsies. Available techniques often require either fresh tissue, several primer pairs, nested amplifications, or specialized electrophoresis steps such as denaturing gradient gel electrophoresis. Our method is based on heteroduplex analysis of polymerase chain reaction (PCR) products of the TCRgamma in a nondenaturing modified polyacrylamide gel using a single pair of primers and is adapted for paraffin-embedded tissue. When tested against Southern blot analysis, the PCR results correlated in 8 of 9 cases. Six mature cutaneous B-cell lymphomas and 29 inflammatory skin disorders all resulted in a polyclonal amplification pattern. When analyzing 3-mm or 4-mm punch biopsies of 51 cases of cutaneous T-cell lymphoma, 37 (72.5%) showed a clonal rearrangement with this technique. For 7 cases of patch stage mycosis fungoides, frozen tissue and formalin-fixed and paraffin-embedded tissue was available, and in 5 of 7 cases (71%), the results in frozen and paraffin-embedded tissue were concordant. One case showed a clonal pattern in frozen tissue but not in paraffin-embedded tissue, and one case was polyclonal in frozen tissue but monoclonal in paraffin-embedded tissue. Using serial dilutions of DNA from a T-cell ALL in a polyclonal background (tonsil), we established a sensitivity of 0.5%. Heteroduplex PCR of the TCRgamma is a rapid, sensitive, and inexpensive screening procedure as well as a useful adjunct to histologic analysis and immunophenotyping of cutaneous T-cell proliferations.

Detection of expanded T cell clones in skin biopsy samples of patients with lichen sclerosus et atrophicus by T cell receptor-gamma polymerase chain reaction assays

Lichen sclerosus et atrophicus is a chronic dermatosis of unknown etiology and pathogenesis. Lichen sclerosus et atrophicus associated skin lesions show T cell enriched infiltrates, sometimes resembling the histologic picture of early mycosis fungoides. It is supposed that the infiltrating T cells participate in the pathogenesis of atrophy and sclerosis. We investigated skin biopsies from 39 lichen sclerosus et atrophicus patients by histology, immunohistochemistry and, in order to establish the status of T cell clonality, by polymerase chain reaction amplifying the T cell receptor-gamma rearrangements. A stage-dependent shift of the CD3-positive T cells was observed from a predominantly CD4-positive to a predominantly CD8-positive phenotype. The increase of CD8-positive cells was associated with more pronounced epidermotropism and basal degeneration. Nearly all CD8-positive cells expressed cytotoxic granules (TIA1), possibly causing the basal destruction. In the late fibrotic stage of the disease, only a weak or no infiltrate was found. Regarding the T cell receptor-gamma polymerase chain reaction, the presence of clonally expanded T cells was demonstrated in 19 of 39 patients (49%) by at least one of two different high resolution electrophoresis techniques applied to separate the amplification products. Thus, for the first time clonally expanded infiltrating T cells were detected in lichen sclerosus et atrophicus. Furthermore, this is one of the first reports on the detection of clonally expanded infiltrating T cells in an inflammatory skin disease. The clonal T cells could not be assigned to the CD4 or CD8 subtype. Most likely, their presence is not the result of a malignant transformation but a response to an as yet unknown lichen sclerosus et atrophicus associated antigen.

Monoclonality of intraepidermal T lymphocytes in early mycosis fungoides detected by molecular analysis after laser-beam-based microdissection

The identification of neoplastic lymphocytes in early lesions of mycosis fungoides is difficult because of the scarcity of the infiltrate and the presence of reactive T lymphocytes admixed with neoplastic cells. Molecular analysis of the T cell receptor gene rearrangement using the polymerase chain reaction technique demonstrates monoclonality only in a proportion of these cases. The exact location of the malignant clone is unknown, and at present it is not clear whether neoplastic cells in early lesions reside within the epidermis, the superficial dermis, or both. We analyzed skin lesions from five patients with early mycosis fungoides using the polymerase chain reaction technique after microdissection of the specimens. In each case the epidermis was separated from the dermis using a laser-beam microdissection technique. Three samples were prepared from each lesion: one containing only the epidermis, one only the superficial dermis, and one the entire specimen. A distinct band could be observed in the epidermal sample in four cases, indicating the presence of an intraepidermal monoclonal population of T lymphocytes. The dermal sample revealed a monoclonal pattern in two cases (both of them showing clonality also within the epidermis). Analysis of the entire specimen revealed a monoclonal pattern only in two cases. Our results demonstrate that intraepidermal lymphocytes in early mycosis fungoides often show a monoclonal pattern of T cell receptor gene rearrangement. Microdissection of biopsy specimens may enhance the sensitivity of the polymerase chain reaction technique.

Efficacy of Histologic Criteria for Diagnosing Early Mycosis Fungoides

The correct classification of lymphoproliferative disorders provides valuable information regarding subsequent clinical evolution of the disease. The ability of pathologists to distinguish such lesions is generally low, especially when dealing with minimal lymphoid infiltrates. To improve the efficacy of histopathology in the diagnosis of early lesions of mycosis fungoides (MF), we reviewed 24 skin biopsies from 18 patients with patch stage lesions of MF early in the course of their disease and 13 slides of lichenoid, spongiotic, or psoriasiform simulators of MF as a control series. A series of cytoarchitectural features was assessed, and differences in the distribution of histopathologic parameters between the two groups (early MF lesions and MF simulators) were evaluated by the chi-square test and Fisher's exact test. For these parameters, sensitivity and specificity also were calculated. A multivariate log-linear analysis was performed to estimate which of the morphologic parameters yielded independent diagnostic information. We found that the most important feature for the diagnosis of lymphoma was the presence of lymphocytes with extremely convoluted, medium-large (7-9 microm in diameter) nuclei (medium-large cerebriform cells), singly or clustered in the epidermis and in small sheets in the dermis. Additional significant histologic features were epidermotropism as single cells lined up along the basal keratinocytes of the dermal-epidermal junction, absence of significant papillary dermis fibrosis, and absence of significant numbers of dermal blastlike cells. We conclude that the efficacy of single histopathologic features in the diagnosis of early MF is generally poor. Only the presence of medium-large cerebriform cells in the epidermis or in clusters in the dermis proved to be a highly reliable feature. However, the histopathologic diagnosis of early MF lesions and their discrimination from inflammatory simulators can be achieved using the constellation of cytoarchitectural parameters proposed.

Polymerase chain reaction/denaturing gradient gel electrophoresis (PCR/DGGE): sensitivity, band pattern analysis, and methodologic optimization

Polymerase chain reaction/denaturing gradient gel electrophoresis (PCR/DGGE) has been gaining popularity as a preferred method to determine the clonality of T-cell populations in small or sparsely infiltrated specimens such as skin biopsies. T-cell receptor (TCR)-gamma gene rearrangements are amplified using nested consensus primers in two rounds of PCR and then are separated by DGGE. Sensitivity is better than with conventional Southern blot analysis but not fully defined. In addition to a discrete primary band resulting from a monoclonal TCR-gamma gene rearrangement, there are often weaker secondary bands of unknown origin. Our goals were to define the PCR/DGGE clonal detection threshold, determine the genesis of the multiband pattern, and optimize methods to minimize extraneous bands. Titration studies showed that the sensitivity of PCR/DGGE for detecting clonal T-cell DNA is affected by the polyclonal T-cell content of the background DNA. The detection threshold is 0.001% using keratinocyte DNA as diluent but only 1% with tonsil DNA. Analysis of monoclonal T-cell lines showed that multiple bands can be produced by a single TCR-gamma gene rearrangement. Mixing of inner and outer primer pair PCR products showed that this is an artifact resulting from different sized PCR products produced during the two rounds of nested PCR required for optimal specificity. Repeat DGGE of isolated bands ruled out variable mobility of partially melted PCR products. Reduction of first round PCR product used as second round target from 10 microl to 1 microl, or a decrease of first round primers from 40 pmole to 5 pmole, resulted in diminished secondary bands without compromising primary band intensity. These results show that: 1) PCR/DGGE has a realistic clonal detection threshold of 0.1% to 1%, 2) multiple bands are consistent with a monoclonal T-cell population, and 3) conditions can be optimized to minimize artifactual secondary bands.

Sézary T-cell activating factor is a Chlamydia pneumoniae-associated protein

We previously identified a protein that was stimulatory for malignant Sézary T cells, termed Sézary T-cell activating factor (SAF). However, the identity of this protein has not been fully elucidated, nor has it's role been determined in the pathogenesis of cutaneous T-cell lymphoma (CTCL). The basis for epidermotropism and proliferation of malignant cells in the skin of patients with CTCL is unknown. Using a monoclonal antibody inhibitory for SAF activity, we demonstrated that SAF is present in the skin of 16 of 27 samples from patients with mycosis fungoides, the predominant form of CTCL. In this report, the SAF determinant is demonstrated to be associated with Chlamydia pneumoniae bacteria by immunohistochemistry, immunoelectron microscopy, and culture analysis. Reactivity of antibodies against an outer membrane protein of C. pneumoniae or against the lipopolysaccharide of Chlamydiae spp. demonstrated that these determinants are coexpressed in 90% of the SAF-positive samples. We confirmed the presence of C. pneumoniae DNA and RNA in the skin by PCR and reverse transcription-PCR and by sequence analysis of the PCR products. The expression of the C. pneumoniae antigens and SAF appears to be associated with active disease in that C. pneumoniae antigens were absent or greatly diminished in the skin of three patients examined after Psoralen and long-wave UVA radiation treatment. Our results suggest that SAF is a Chlamydia-associated protein and that further investigation is warranted to determine whether SAF and C. pneumoniae play a role in the pathogenesis of CTCL.

Clonal T-cell receptor gamma-chain gene rearrangement by PCR-based GeneScan analysis in advanced cutaneous T-cell lymphoma: a critical evaluation

Detection of clonal T-cell receptor gamma (TCRgamma)-chain gene rearrangement is a promising approach to distinguish between cutaneous T-cell lymphomas (CTCLs) and reactive T-cell infiltrates. Despite the improved sensitivity by using the polymerase chain reaction (PCR) rather than Southern blot analysis, monoclonality could be demonstrated in only 53-90 per cent of CTCL biopsies in recent studies. In the present study, formalin-fixed, paraffin-embedded specimens of 21 selected patients with clear-cut advanced-stage CTCL were analysed using a semi-nested TCRgamma PCR with newly developed consensus primer pairs. Detection of PCR products was done by GeneScan analysis (GSA); this technique is advantageous due to its sensitivity and accuracy in the detection and size determination of PCR products and it is easier to interpret than direct read-outs from TGGE or DGGE gels. In serial dilution experiments, TCRgamma-PCR-GSA allowed the detection of clonal, rearranged T-cells with a high in vitro sensitivity against a polyclonal background (1-6 per cent). Despite the selection of clear-cut, advanced-stage CTCL cases, however, dominant clonal TCRgamma-chain gene rearrangement was found in only 16 of the 21 patients analysed, indicating an overall clinical sensitivity of 76 per cent. Specificity was evaluated using biopsy specimens from 21 control patients suffering from long-standing psoriasis (n=13) and eczema (n=8). Surprisingly, GeneScan profiles showing apparently single dominant peaks were detected in 14 per cent of these skin lesions, but these profiles turned out to be pseudo-monoclonal by repeated determinations. In conclusion, TCRgamma-PCR-GSA does not suffice reliably to exclude malignancy, due to its limited clinical sensitivity, but with precautions taken to detect pseudo-monoclonality and to secure specificity, TCRgamma-PCR-GSA is a valuable instrument in the diagnosis of CTCL.

Prognostic Significance of a Polymerase Chain Reaction–Detectable Dominant T-Lymphocyte Clone in Cutaneous Lesions of Patients With Mycosis Fungoides

Although mycosis fungoides (MF) is considered to be an indolent lymphoma, survival is highly influenced by TNM stage. At diagnosis, most MF patients present with early stage disease and a high probability of long-term survival. Treatment is generally directed towards skin lesions, and achievement and duration of complete responses are variable. A dominant T-cell clone is detectable in the cutaneous lesions of 60% of patients. The aim of this study was to determine whether the presence of a T-cell clonal population influences the clinical course of the disease after topical therapy. Cutaneous biopsies from 68 patients were histologically diagnosed as MF and T-cell clonality was analyzed by in vitro amplification of TCR-γ chain gene rearrangements (polymerase chain reaction γ [PCRγ]). After a median follow-up of 48 months, response to treatment was clinically assessed. Age, sex, duration of symptoms before diagnosis, type of cutaneous lesions (T stage), TNM stage, and PCRγ were evaluated as predictive factors of response to treatment in univariate and multivariate analyses. Univariate analysis demonstrated that T1 cutaneous lesions (P = .05) and PCRγ negativity (P = .007) were associated with a higher complete remission rate. Using multivariate analysis, T stage (relative risk, 3.13; P = .06) and PCRγ (relative risk, 4.4; P = .01) remained independent significant predictive parameters of response. In conclusion, T stage and cutaneous PCRγ at diagnosis are the two predictive parameters of treatment response for MF. Therefore, the cutaneous PCRγ findings should be considered in the analysis of future therapeutic trials.

© 1998 by The American Society of Hematology.

Prognostic Significance of a Polymerase Chain Reaction–Detectable Dominant T-Lymphocyte Clone in Cutaneous Lesions of Patients With Mycosis Fungoides

Although mycosis fungoides (MF) is considered to be an indolent lymphoma, survival is highly influenced by TNM stage. At diagnosis, most MF patients present with early stage disease and a high probability of long-term survival. Treatment is generally directed towards skin lesions, and achievement and duration of complete responses are variable. A dominant T-cell clone is detectable in the cutaneous lesions of 60% of patients. The aim of this study was to determine whether the presence of a T-cell clonal population influences the clinical course of the disease after topical therapy. Cutaneous biopsies from 68 patients were histologically diagnosed as MF and T-cell clonality was analyzed by in vitro amplification of TCR-γ chain gene rearrangements (polymerase chain reaction γ [PCRγ]). After a median follow-up of 48 months, response to treatment was clinically assessed. Age, sex, duration of symptoms before diagnosis, type of cutaneous lesions (T stage), TNM stage, and PCRγ were evaluated as predictive factors of response to treatment in univariate and multivariate analyses. Univariate analysis demonstrated that T1 cutaneous lesions (P = .05) and PCRγ negativity (P = .007) were associated with a higher complete remission rate. Using multivariate analysis, T stage (relative risk, 3.13; P = .06) and PCRγ (relative risk, 4.4; P = .01) remained independent significant predictive parameters of response. In conclusion, T stage and cutaneous PCRγ at diagnosis are the two predictive parameters of treatment response for MF. Therefore, the cutaneous PCRγ findings should be considered in the analysis of future therapeutic trials.

© 1998 by The American Society of Hematology.

Detection of clonal T-cell receptor gamma chain gene rearrangements by polymerase chain reaction and denaturing gradient gel electrophoresis (PCR/DGGE) in archival specimens from patients with early cutaneous T-cell lymphoma: correlation of histologic findings with PCR/DGGE

BACKGROUND

Early stages of cutaneous T-cell lymphoma (CTCL) may be difficult to distinguish from benign inflammatory dermatoses by routine histologic examination.

OBJECTIVE

Our purpose was to determine whether clonal rearrangements of the T-cell receptor (TCR) gamma gene by polymerase chain reaction and denaturing gradient gel electrophoresis (PCR/DGGE) could be detected in the early stages of CTCL and to correlate these findings with conventional histopathology.

METHODS

A total of 39 specimens from 12 patients with CTCL were obtained. The slides were evaluated independently by three dermatopathologists, and categorized into three groups: nondiagnostic, suggestive of CTCL, and diagnostic of CTCL. Of the 39 specimens, 33 were tested by PCR/DGGE by means of GC-clamped primers for clonal rearrangement of the TCR gamma gene.

RESULTS

The histologic evaluation of the 12 cases showed a significant variation among the three dermatopathologists. The correlation of PCR/DGGE with routine histology was as follows: Clonal TCR gamma gene rearrangements were demonstrated in 73% of the specimens nondiagnostic for CTCL, 71% of those suggestive of CTCL, and 74% of those diagnostic of CTCL.

CONCLUSION

Clonal TCR gamma gene rearrangements may be detected in patients with early CTCL, even when the histologic findings are not unequivocally diagnostic. In patients with multiple biopsy specimens, identical clones were demonstrated in all rearranged samples, indicating the same neoplastic clone was present in the earliest stages of disease.

Demonstration of Frequent Occurrence of Clonal T Cells in the Peripheral Blood of Patients With Primary Cutaneous T-Cell Lymphoma

Clonal T cells have been demonstrated in skin lesions of all stages of cutaneous T-cell lymphomas (CTCLs). However, there are conflicting data regarding the CTCL stage at which dissemination of clonal cells into peripheral blood occurs. Although the multifocal occurrence of cutaneous CTCL lesions and T-cell recirculation suggest an early appearance of neoplastic cells in the blood, circulating clonal T cells have only been detected in advanced stages. We investigated their occurrence by a highly sensitive polymerase chain reaction (PCR) assay amplifying T-cell receptor γ rearrangements and subsequent heteroduplex temperature gradient gel electrophoresis (HD-TGGE) of the amplification products. Circulating clonal T cells were found in 26 of 45 patients with mycosis fungoides (MF ), six of seven with Sezary's syndrome (SS), 10 of 13 pleomorphic CTCLs, and three of four unclassified CTCLs. Corresponding skin specimens carried clonal T cells in 29 of 40 MF, three of four SS, 12 of 12 pleomorphic, and two of two unclassified CTCL patients. Except for the blood specimen of a psoriatic patient, all samples of 60 controls (psoriasis vulgaris, atopic dermatitis, and healthy volunteers) revealed polyclonal amplification products. In 30 of 32 CTCL patients carrying a clonal rearrangement in blood and skin, identity of both clones was indicated by HD-TGGE and confirmed by sequencing six of these cases. We found an unexpected high frequency of identical clonal T cells in peripheral blood and skin of CTCL patients, including early stages of MF. This supports the concept of an early systemic disease in CTCL and raises new questions concerning the pathogenesis.

Demonstration of Frequent Occurrence of Clonal T Cells in the Peripheral Blood of Patients With Primary Cutaneous T-Cell Lymphoma

Clonal T cells have been demonstrated in skin lesions of all stages of cutaneous T-cell lymphomas (CTCLs). However, there are conflicting data regarding the CTCL stage at which dissemination of clonal cells into peripheral blood occurs. Although the multifocal occurrence of cutaneous CTCL lesions and T-cell recirculation suggest an early appearance of neoplastic cells in the blood, circulating clonal T cells have only been detected in advanced stages. We investigated their occurrence by a highly sensitive polymerase chain reaction (PCR) assay amplifying T-cell receptor γ rearrangements and subsequent heteroduplex temperature gradient gel electrophoresis (HD-TGGE) of the amplification products. Circulating clonal T cells were found in 26 of 45 patients with mycosis fungoides (MF ), six of seven with Sezary's syndrome (SS), 10 of 13 pleomorphic CTCLs, and three of four unclassified CTCLs. Corresponding skin specimens carried clonal T cells in 29 of 40 MF, three of four SS, 12 of 12 pleomorphic, and two of two unclassified CTCL patients. Except for the blood specimen of a psoriatic patient, all samples of 60 controls (psoriasis vulgaris, atopic dermatitis, and healthy volunteers) revealed polyclonal amplification products. In 30 of 32 CTCL patients carrying a clonal rearrangement in blood and skin, identity of both clones was indicated by HD-TGGE and confirmed by sequencing six of these cases. We found an unexpected high frequency of identical clonal T cells in peripheral blood and skin of CTCL patients, including early stages of MF. This supports the concept of an early systemic disease in CTCL and raises new questions concerning the pathogenesis.

A realistic approach to the sensitivity of PCR-DGGE and its application as a sensitive tool for the detection of clonality in cutaneous T-cell proliferations

The practical value of the detection of clonality within the T-cell receptor gamma locus by polymerase chain reaction for the diagnosis of cutaneous T-cell lymphomas is well known. However, studies dealing with this subject so far, with special emphasis on the sensitivity of the technique in comparison to, for example, Southern blotting have used mixtures of DNA in various concentrations instead of using mixtures of the cells involved, which would reflect the in vivo situation in a more realistic scope. The purpose of this study was therefore to determine the sensitivity and the limitations of the PCR assay by dilution experiments, using mixtures of cells. Furthermore we studied its applicability to cutaneous T-cell proliferative disorders. Two clonal T-cell lines (MyLa and Jurkat) served as positive control. Dilutions of MyLa cells, cultured normal human keratinocytes and peripheral blood mononuclear cells from lymphoma negative volunteers were used to assess the sensitivity of the PCR-DGGE assay. Skin samples from 4 patients with cutaneous T-cell lymphoma, 1 lesional lymph node, 2 blood samples from a patient with Sézary syndrome and 4 lymphoma-negative tissue samples were analysed. Two samples were uncertain for diagnosis of lymphoma. The PCR-DGGE assay consisted of a 2-round nested PCR with consensus primers within the TCR-gamma locus followed by electrophoretic separation of the product along a denaturing urea/formamide gradient gel. PCR-DGGE sensitivity was, to our knowledge, for the first time investigated for mixtures of lymphocytes (clonal and polyclonal) and keratinocytes. Clonal T-cells were detected in a concentration between 1-0.1% in keratinocytes, whereas the sensitivity was generally lower upon dilution in peripheral blood mononuclear cells or in a mixture of keratinocytes and peripheral blood mononuclear cells. Nevertheless, T-cell clonality was detected in 2 blood samples of a patient with Sézary syndrome, which were negative by Southern blot analysis. The crucial point of this work was the new approach to establish the sensitivity of the PCR-DGGE, in a way which more closely mimics the condition of clinical specimens. Instead of mixing and amplifying DNA extracted from clonal T-cell lines and polyclonal bone marrow cells, we amplified DNA from clonal and polyclonal cells which had been mixed in various ratios before DNA extraction. Polymerase chain reaction in conjunction with denaturing gradient gel electrophoresis is a sensitive and versatile molecular tool for the assessment of clonality of suspect cutaneous lesions. The determination of sensitivity using DNA extracted from premixed cells more closely corresponds to the actual test situation when testing skin samples.

Detection of low-level tumor cells in allergic contact dermatitis induced by mechlorethamine in patients with mycosis fungoides

Two patients with histologically proven mycosis fungoides, a malignancy of phenotypically mature T cells, received a topical challenge with mechlorethamine to areas of clinically uninvolved skin to exclude possible hypersensitivity reactions to this chemotherapeutic agent. In both patients, allergic contact dermatitis (ACD) developed at the sites of the application and resolved completely after withdrawal of mechlorethamine. The lesions were biopsied and analyzed for the presence of clonal T-cell receptor (TCR)-gamma gene rearrangements using two polymerase chain reaction (PCR)-based assays involving denaturing gradient gel electrophoresis (PCR/DGGE) and ribonuclease protection analysis (PCR/RPA). The former method has a clonal detection threshold of 10(-3)-10(-2), while the latter has a sensitivity of 10(-5). In both cases, the ACD lesions were polyclonal by PCR/DGGE. In contrast, PCR/RPA detected tumor-specific TCR-gamma gene rearrangements in these same lesions. This indicates that the ACD lesions contained tumor cells at a density within the 10(-5)-10(-2) range. Analysis of peripheral blood mononuclear cells from both patients failed to detect the malignant clone and showed the same result as blood from four normal individuals. The normal skin from one skin patient also lacked detectable TCR-gamma gene rearrangements. These results indicate that mycosis fungoides tumor are present within ACD lesions induced in mycosis fungoides patients and that this phenomenon does not appear to be due to the ubiquitous presence of detectable levels of these tumor cells in the blood or skin. These findings might be explained by nonspecific recruitment of malignant T cells to sites of local inflammation mediated by non-neoplastic antigen-specific T cells. Alternatively, they might be due to the local proliferation of very rare tumor cells in apparently normal skin in response to cytokines generated during the ACD reaction. In either case, the present study offers evidence that the malignant cells in myosis fungoides retain at least some capability of responding in vivo to physiologic stimuli.

Lymphomatoid papulosis and associated cutaneous lymphoproliferative disorders exhibit a common clonal origin

Determination of the clonal relationship among multiple lymphoproliferative disorders occurring in individual patients has been hampered by dependence on molecular biologic techniques that require analysis of advanced lesions containing high tumor clone densities to isolate dominant, clonal antigen-receptor gene rearrangements. Polymerase chain reaction/denaturing gradient gel electrophoresis (PCR/DGGE) involves the amplification of T-cell receptor (TCR)-gamma gene rearrangements followed by their electrophoresis in denaturing gradient gels. This method detects dominant TCR-gamma gene rearrangements at tumor clone densities as low as 0.1%, making this assay suitable for analysis of early as well as late lesions. Using this approach, we analyzed skin lesions of lymphomatoid papulosis and either CD30+ large-cell lymphoma or early patch/plaque mycosis fungoides that developed in three patients. In each case, the dual specimens exhibited an identical band pattern by PCR/DGGE analysis, suggesting a common clonal origin. To confirm this clonal relationship, the dominant TCR-gamma gene rearrangements were eluted, amplified, cloned, and sequenced. In each case, they showed identical junctional sequences. These findings are significant for several reasons: 1) they demonstrate the common clonal origin of lymphomatoid papulosis and CD30+ large-cell lymphoma or mycosis fungoides occurring in individual patients; 2) they confirm that co-migrating PCR/DGGE bands exhibit identical nucleotide sequences; and 3) they provide a method for determining the sequence of a tumor-derived TCR-gamma gene rearrangement in early lesions containing a low tumor clone density. This latter feature should allow the prospective molecular staging of early cutaneous lymphoproliferative disorders.