bcl-1, bcl-2, p53, c-myc, and lyt-10 analysis in cutaneous lymphomas

Doxycycline is an NF-κB inhibitor that induces apoptotic cell death in malignant T-cells

Cutaneous T-cell Lymphoma (CTCL) is a rare non-Hodgkin's lymphoma that can affect the skin, blood, and lymph nodes, and can metastasize at late stages. Novel therapies that target all affected disease compartments and provide longer lasting responses while being safe are needed. One potential therapeutic target is NF-κB, a regulator of immune responses and an important participant in carcinogenesis and cancer progression. As a transcription factor, NF-κB targets genes that promote cell proliferation and survival. Constitutive or aberrant activation of NF-κB is encountered in many types of cancer, including CTCL.Recently, while analyzing gene-expression profiles of a variety of small molecule compounds that target NF-κB, we discovered the tetracycline family of antibiotics, including doxycycline, to be potent inhibitors of the NF-κB pathway. Doxycycline is well-tolerated, safe, and inexpensive; and is commonly used as an antibiotic and anti-inflammatory for the treatment a multitude of medical conditions.In our current study, we show that doxycycline induces apoptosis in a dose dependent manner in multiple different cell lines from patients with the two most common subtypes of CTCL, Mycosis Fungoides (MF) and Sézary Syndrome (SS). Similar results were found using primary CD4+ T cells from a patient with SS. Doxycycline inhibits TNF induced NF-κB activation and reduces expression of NF-κB dependent anti-apoptotic proteins, such as BCL2α. Furthermore, we have identified that doxycycline induces apoptosis through reactive oxygen species.

Altered expression of Bcl-2, c-Myc, H-Ras, K-Ras, and N-Ras does not influence the course of mycosis fungoides

INTRODUCTION

Data about genetic alterations in mycosis fungoides (MF) are limited and their significance not fully elucidated. The aim of the study was to explore the expression of various oncogenes in MF and to assess their influence on the disease course.

MATERIAL AND METHODS

Skin biopsies from 27 MF patients (14 with early MF and 13 with advanced disease) and 8 healthy volunteers were analyzed by real-time polymerase chain reaction (PCR) to detect Bcl-2, c-Myc, H-Ras, K-Ras and N-Ras expression. All PCR reactions were performed using an Applied Biosystems 7900HT Fast Real-Time PCR System and interpreted using Sequence Detection Systems software which utilizes the comparative delta Ct method. The level of mRNA was normalized to GAPDH expression. All data were analyzed statistically.

RESULTS

All evaluated oncogenes were found to be expressed in the skin from healthy controls and MF patients. Bcl-2 (-4.2 ±2.2 vs. -2.2 ±1.1; p = 0.01), H-Ras (-3.0 ±3.3 vs. 0.6 ±2.6; p = 0.01) and N-Ras (-3.6 ±2.0 vs. -1.1 ±2.4; p = 0.03) were expressed at significantly lower levels in MF. No relationships between oncogene expression and disease stage, presence of distant metastases and survival were observed (p > 0.05 for all comparisons).

CONCLUSIONS

The pathogenic role and prognostic significance of analyzed oncogenes in MF seem to be limited and further studies are needed to establish better prognostic factors for patients suffering from MF.

Abnormal AP-1 protein expression in primary cutaneous B-cell lymphomas

BACKGROUND

Primary cutaneous B-cell lymphoma (PCBCL) consists mainly of primary cutaneous marginal zone B-cell lymphoma (PCMZL), primary cutaneous follicle centre lymphoma (PCFCL) and primary cutaneous large B-cell lymphoma, leg type (PCLBCL-LT). The activator protein 1 (AP-1) transcription factor includes JUN, FOS and other family members.

OBJECTIVES

To assess the expression pattern of AP-1 transcription factors in PCBCL.

METHODS

We analysed paraffin tissue sections from nine cases of PCMZL, seven PCFCL, six PCLBCL-LT and two unspecified PCBCL cases by using immunohistochemistry with antibodies against c-JUN, JUNB, JUND, c-FOS, RAF1, alphaPAK, CD30 and CCND1.

RESULTS

A positive staining for JUND (++) was observed in six cases of PCFCL (86%), five PCLBCL-LT (83%) and five PCMZL (56%). Positive CCND1 protein expression was present in four cases of PCLBCL-LT (67%), four PCFCL (57%) and four PCMZL (44%), and the two unspecified PCBCL cases. Expression of alphaPAK protein was seen in three cases of PCLBCL-LT (50%), two PCMZL (22%) and one PCFCL. However, c-JUN, c-FOS and RAF1 protein were rarely expressed in the PCBCL cases analysed; JUNB and CD30 protein expression was absent in these cases.

CONCLUSIONS

These findings suggest that the presence of abnormal AP-1 protein expression is associated with upregulation of JUND, CCND1 and alphaPAK and downregulation of JUNB in PCBCL.

Mycosis fungoides--analysis of the duration of disease stages in patients who progress and the time point of high-grade transformation

BACKGROUND

Mycosis fungoides (MF) is a low-grade malignant primary cutaneous T-cell lymphoma which, in its evolution, passes through five distinct stages (patch, plaque, and tumor stages, lymph node infiltration, and, finally, multiple organ infiltration). Furthermore, a blast transformation into a high-grade malignant lymphoma can occur. In order to better understand the dynamics of the disease and the prognostic implications in patients who progress, we studied the duration of each stage and the time at which blast transformation occurred.

METHODS

We reviewed the records of 48 MF patients who had been followed in the lymphoma clinic of the Department of Dermatology, University Hospital Zurich, Zurich, Switzerland for a median of 10 years. Forty-two cases were eligible for evaluation.

RESULTS

Our study showed that MF in patients who progress is a disease which, after an initial patch stage with an average duration of 7.2 years, a plaque stage lasting for an average of 2.3 years, and a tumor stage with an average duration of 1.8 years, leads to a stage of lymph node infiltration with an average duration of 0.6 years, internal organ infiltration lasting for an average of 0.5 years and, finally, a fatal outcome. Consequently, the overall average disease duration in progressing patients is 12.4 years. Blast transformation occurs in 85% of all cases in the tumor stage.

CONCLUSIONS

The course of progressing MF is chronic and advancing. The progression is initially slow and later accelerates. Important prognostic factors are the stage of disease and the presence of blast transformation. The prognosis is better in the early stage and when blast transformation is absent.

Increased expression of CTLA-4 in malignant T-cells from patients with mycosis fungoides -- cutaneous T cell lymphoma

Mycosis fungoides (MF) is a low-grade lymphoma of cluster of differentiation (CD)4+, CD45RO+, cutaneous leukocyte antigen (CLA)+ T cells that homes to the skin. To understand the functional abnormalities in this disease, we study the regulation of cytotoxic T-lymphocyte antigen (CTLA)-4 in peripheral blood mononuclear cells (PBMCs) from patients with MF. CTLA-4 is a costimulatory molecule for T cells that functions in immunoregulation. Unlike the expression of CD28, which is expressed constitutively on T cells, CTLA-4 expression is highly regulated. In the analysis of PBMCs in MF, we found that CTLA-4 is stimulated by phorbol myristate acetate/A23187 to a greater level when compared to normals. This defect was seen in the dominant clones of T cells. The increased CTLA-4 expression was significant between normal and MF, with a correlation between higher expression of CTLA-4 and a higher grade of MF. In a patient whose disease progressed, the CTLA-4 level increased. The abnormal level of CTLA-4 was confirmed at both the transcription and translation levels. Although MF is associated with a Th2 bias, Th1 cytokines IL-2 and IFN-gamma enhanced CTLA-4 expression, while IL-4 did not. These findings reveal an abnormal regulation of CTLA-4 expression in MF and show that PBMCs from patients with MF have properties that are divergent from those of normal T cells.

Primary Cutaneous T-Cell Lymphomas Show a Deletion or Translocation AffectingNAV3, the HumanUNC-53Homologue

Multicolor fluorescent in situ hybridization (FISH) was used to identify acquired chromosomal aberrations in 12 patients with mycosis fungoides or Sézary syndrome, the most common forms of primary cutaneous T-cell lymphoma (CTCL). The most frequently affected chromosome was 12, which showed clonal deletions or translocations with a break point in 12q21 or 12q22 in five of seven consecutive Sézary syndrome patients and a clonal monosomy in the sixth patient. The break point of a balanced translocation t(12;18)(q21;q21.2), mapped in the minimal common region of two deletions, fine mapped to 12q2. By locus-specific FISH, the translocation disrupted one gene, NAV3 (POMFIL1), a human homologue of unc-53 in Caenorhabditis elegans. A missense mutation in the remaining NAV3 allele was found in one of six cases with a deletion or translocation. With locus-specific FISH, NAV3 deletions were found in the skin lesions of four of eight (50%) patients with early mycosis fungoides (stages IA-IIA) and in the skin or lymph node of 11 of 13 (85%) patients with advanced mycosis fungoides or Sézary syndrome. Preliminary functional studies with lentiviral small interfering RNA-based NAV3 silencing in Jurkat cells and in primary lymphocytes showed enhanced interleukin 2 expression (but not CD25 expression). Thus, NAV3 may contribute to the growth, differentiation, and apoptosis of CTCL cells as well as to the skewing from Th1-type to Th2-type phenotype during disease progression. NAV3, a novel putative haploinsufficient tumor suppressor gene, is disrupted in most cases of the commonest types of CTCL and may thus provide a new diagnostic tool.

Cutaneous T-cell lymphomas: a review with emphasis on new treatment approaches

Primary cutaneous T-cell lymphomas represent a wide variety of non-Hodgkin lymphomas that are characterized by a distinct clinical presentation. Advanced molecular and biological techniques have enhanced the recognition of cutaneous T-cell lymphomas. The most common subtypes of cutaneous T-cell lymphomas are the epidermotropic variants mycosis fungoides and Sézary syndrome. At present, a stage-adjusted therapy is the best concept available, since early aggressive treatment options did not improve the prognosis of patients with cutaneous T-cell lymphomas. Accurate diagnostic and clinical assessment as well as identification of prognostic factors provides a helpful basis for treatment strategies. Current medical literature on diagnosis, prognosis, and treatment is reviewed with emphasis on new biologic response-modifying treatment options.

Expression of apoptosis regulators in cutaneous T-cell lymphoma (CTCL) cells

This study examined cutaneous T-cell lymphoma (CTCL) cell lines and cutaneous lesions for the presence of Bcl-2 gene family members and found that the two apoptosis-inhibiting members Bcl-xL and Mcl-1 and the two apoptosis-supporting members Bad and Bax were expressed. However, Bad was at least partially inactivated by phosphorylation. In skin lesions, the translocation of Bad from the nucleus to the cytoplasm may reflect the Bad inactivation by phosphorylation identified in vivo. Bax is also ineffective, as the non-steroidal anti-inflammatory drug sulindac, whose cytotoxic effect is mediated by Bax, could not induce apoptosis in CTCL cell lines. The expression of Bcl-2, Bcl-xL, and Mcl-1 may therefore be sufficient to guarantee the survival of malignant CTCL cells. The Bcl-x, Mcl-1, Bad, and Bax proteins were also expressed in all CTCL skin lesions tested. In two patients from whom two biopsies from two different time points of the disease were available, a significant increase in Mcl-1 expression was found in the later-stage skin lesion. Overexpression of Mcl-1 and synthesis of non-functional Bax may be responsible for the resistance of CTCL cells to the anti-cancer drugs chlorambucil and sulindac.

Chromosomal abnormalities in relation to clinical disease in patients with cutaneous T-cell lymphoma: a 5-year follow-up study

BACKGROUND

Patients with cutaneous T-cell lymphoma (CTCL) show chromosomal aberrations in skin and blood lymphocytes.

OBJECTIVES

To evaluate the significance of peripheral blood clonal or non-clonal chromosomal abnormalities in comparison with the clinical course of cutaneous T-cell lymphoma patients.

PATIENTS/METHODS

Five patients with large-plaque parapsoriasis (LPP) or with follicular mucinosis, eight with mycosis fungoides and two with Sézary syndrome were followed for an average of 54 months. G-banding and enzyme-detected in situ hybridization (EDISH) were used to identify aberrations in chromosomes 1, 6, 8, 9, 11, 13/21, 15 or 17, that had previously showed frequent aberrations.

RESULTS

The aberration rates of all chromosomes studied differed between patients with active disease and healthy or photochemotherapy-treated controls by EDISH or G-banding (P < 0.01 to P < 0.05). Patients in complete remission differed from healthy controls for aberrations of chromosomes 1, 6 and 11, and from patients with active, progressing disease for chromosomes 1, 6, 8, 11 and 17 (P < 0.01 to P < 0.05, EDISH or G-banding). All 11 samples representing active, progressing disease showed elevated levels of chromosome 8 aberrations in EDISH. The change in chromosomal aberration rate and clinical condition between two consecutive samples agreed for chromosomes 1, 8, 9 and 15 (G-banding) and for chromosome 17 (G-banding and EDISH; kappa > 0.5-0.6). Six of seven patients (five CTCL, one LPP patient) with clonal chromosomal aberrations by G-banding showed continuously active disease and four of them, but none of the other patients, died within 30 months of the detection of the clone.

CONCLUSIONS

The rate of chromosomal aberrations associates with the activity of CTCL, and has prognostic significance. Aberrations of chromosomes 1, 6 and 11, although increasing with activity of the disease, seem to be a hallmark of existing disease, detectable even in remission. Aberrations of chromosomes 8 and 17 especially associate with active or progressive disease.

From inflammation to neoplasia: new concepts in the pathogenesis of cutaneous lymphomas

Mycosis fungoides is a clinicopathologic term which describes a neoplasm of cerebriform T lymphocytes that form plaques and tumors. We further suggest that mycosis fungoides arises in a background of chronic inflammation or as a response to chronic antigenic stimulation. Subsequently, a series of mutations results in the stepwise progression from eczematous patches, to plaques, tumors and eventual hematogenous dissemination. The pathogenetic process is driven by various, probably individually different, exogenous factors, e.g. environmental foreign antigens, bacterial superantigen, and/or endogenous factors, e.g. autocrine cytokine loops, CD40/CD40L and B7/CD28 interaction.

Infrequent Fas mutations but no Bax or p53 mutations in early mycosis fungoides: a possible mechanism for the accumulation of malignant T lymphocytes in the skin

Mycosis fungoides (MF) is the most frequent manifestation of cutaneous T cell lymphoma but its cause and pathophysiology remain unclear. Because progression of lesions is characteristically slow, we hypothesized that mycosis fungoides originates from an accumulation of lymphocytes due to defective apoptosis of skin homing T lymphocytes. In this study, we investigate possible alterations of three molecules regulating apoptosis, i.e., Fas antigen, Bax, and p53, at the genomic level in skin lesions from 44 patients with MF, as Fas mediates one of two major pathways for apoptosis of activated T cells. Fas mutations were found in six patients using a polymerase chain reaction and single-strand conformational polymorphism method followed by cloning and sequencing of abnormal polymerase chain reaction products. The mutations predict for defective transmission of the death signal in three cases. Immunohistochemistry demonstrated the lack of Fas protein expression on dermal lymphocytes in one case with Fas gene mutation predicting for a truncated death domain, whereas Fas protein was expressed by dermal lymphocytes in the other investigated cases. By contrast, no mutations of Bax or p53 were found, whereas immunohistochemistry demonstrated increased p53 expression in the nucleus of basal keratinocytes above the neoplastic infiltrate in some MF cases. These results support the hypothesis that Fas defects may play a role in the pathogenesis of MF.

CD4+CD7- leukemic T cells from patients with Sézary syndrome are protected from galectin-1-triggered T cell death

In early stages of cutaneous T cell lymphoma (Sézary syndrome) both CD4+CD7- and CD4+CD7+ T cells clonally expand whereas in late stages of the disease CD7- cells are predominant in number, giving rise to the question whether CD7- T cells have a survival advantage in the skin. Galectin-1, a cell-bound lectin, was recently reported to trigger apoptosis in activated CD7+ T cells. Here, we demonstrate that in contrast to activated CD7(+) T cells, quiescent and activated CD69+ CD7- T cells from healthy donors and from Sézary patients are resistant to galectin-1-mediated cell death. CD7- T cells are apoptosis-resistant even during coculture with IFN-gamma-stimulated endothelial cells that constitutively express galectin-1 in high amounts. These data imply that resistance of CD7- T cells to galectin-1-induced apoptosis may contribute to the accumulation of CD7- Sézary T cells during progression of the disease.

p16(INK4a) is selectively silenced in the tumoral progression of mycosis fungoides

Knowledge about the molecular mechanisms involved in the pathogenesis of tumoral progression in mycosis fungoides (MF) is still scarce. Because the 9p21 locus seems to be a good target for a detailed study in MF, this prompted us to compare the mechanisms of inactivation of the p16(INK4a), p15(INK4b), and p14(ARF) genes in aggressive and stable forms of MF, performing microsatellite analysis, methylation-specific polymerase chain reaction, direct sequencing, and p16(INK4a) protein expression by immunohistochemistry. Additionally, the p53 gene was also sequenced in tumoral lesions. Thirty-nine patients with stable MF were studied. Alterations in p16(INK4a) and p15(INK4b) genes were detected in 18% and 5% of the cases, respectively. None of the cases analyzed showed alterations of the p14(ARF) gene. In contrast with these findings, in the 11 patients with aggressive MF, alterations of the p16(INK4a), p15(INK4b), or p14(ARF) genes were found in 8 (73%), 3 (27%), and 2 (18%) cases, respectively. A significant proportion (4/11) of these alterations were already present in the p16(INK4a) gene in the initial plaque lesions in these aggressive forms of MF. Alterations in the p16(INK4a) gene, either methylation or loss of heterozygosity, were clearly more frequent than those in the p15(INK4b) and p14(ARF) genes. These p16(INK4A) alterations were confirmed using immunohistochemistry. None of the nine tumoral lesions analyzed showed mutations in exons 1-2 of the p16(INK4a) gene or in exons 5-8 of the p53 gene. These results seem to suggest that 9p21 alterations, and selectively p16(INK4a) silencing, could be a characteristic phenomenon in MF progression.

Interleukin-7 and interleukin-15 regulate the expression of the bcl-2 and c-myb genes in cutaneous T-cell lymphoma cells

Interleukin-7 (IL-7) and IL-15 have been recently identified as growth factors for cutaneous T-cell lymphoma (CTCL) cells, and they protect these cells from cell death. Using the CTCL cell line SeAx as a test system now shows that IL-7 and IL-15 are indeed necessary to maintain high levels of bcl-2. The up-regulation of bcl-2 was paralleled by increased DNA-binding activities of the transcription factors STAT2, STAT5, STAT6, and c-Myb to bcl-2 gene promoter-enhancer elements. Because STAT5 and c-Myb positively regulate bcl-2, IL-7 and IL-15 may mediate some of their effects on cell death survival gene expression through these 2 factors. Constitutive activities of the 3 STAT factors and c-Myb were found in the IL-7- and IL-15-independent CTCL cell lines HUT78 and MyLa 2059. The c-Myb protein was also present in CTCL cells of the skin lesions of all investigated patients. These results indicate that IL-7 and IL-15 may increase bcl-2 expression in CTCL cells by the activation of c-myb and STAT factors.

Early mycosis fungoides: molecular analysis for its diagnosis and the absence of p53 gene mutations in cases with progression

The histological diagnosis of initial mycosis fungoides (MF) and the molecular mechanisms that are responsible for its progression and transformation to the more highly malignant variants of MF remain largely unknown. Because of the rare occurrence of these tumours, the need for snap frozen skin biopsy specimens and the difficulty to obtain suitable material for karyotypic and genotypic analysis, specific cytogenetic and molecular lesions have not yet been identified. In particular the role of known oncogenes and tumour suppressor genes, including the p53 gene, in the pathogenesis and clinical progression of MF has not been extensively investigated. The present study was carried out using the polymerase chain reaction (PCR) technique combined with temperature gradient gel electrophoresis (TGGE) to detect mutations of the p53 gene in 58 patients with MF. TGGE analysis was also used in combination with clonality analysis by means of T-cell receptor gamma (TCRG) gene rearrangement studies to distinguish parapsoriasis en plaque and initial MF from patch/plaque stage MF. More than 83% of the diagnoses of initial MF could be confirmed using PCR-TGGE analysis. However, although the sensitive TGGE analysis was used for all exons, p53 gene polymorphisms were found in 4 and p53 gene mutation in only 1 of 58 biopsy specimens. It appears unlikely that p53 gene mutations play a role in either the pathogenesis of parapsoriasis and initial MF or their progression to advanced stages of MF. However, TCRG gene rearrangement studies by means of TCR-TGGE analysis may be useful for distinguishing histologically discordant cases of initial MF.

Decreased expression of Fas (APO-1/CD95) on peripheral blood CD4+ T lymphocytes in cutaneous T-cell lymphomas

BACKGROUND

The usually protracted and indolent course of cutaneous T-cell lymphoma (CTCL) is consistent with an accumulation of lymphocytes rather than being a true proliferative disorder, perhaps as the result of defective lymphocyte apoptosis. Fas (CD95) is the main signalling membrane molecule involved in postactivation T-lymphocyte apoptosis.

OBJECTIVES

To evaluate expression of Fas on circulating CD4+ lymphocytes in patients with CTCL.

METHODS

Fas expression on peripheral blood CD4+ T cells in 16 patients with mycosis fungoides (patch and infiltrated plaque stages) and in four patients with Sézary syndrome was compared with that in 25 matched patients with lymphocyte-mediated cutaneous benign inflammatory disorders and in 15 subjects without inflammatory cutaneous diseases.

RESULTS

Fas expression on peripheral CD4+ lymphocytes was significantly lower in patients with CTCL compared with subjects with benign inflammatory cutaneous disorders and with healthy donors.

CONCLUSIONS

This pattern supports the hypothesis that a defect in T-cell apoptosis may play a part in the pathophysiology of CTCL, perhaps through abnormalities of the Fas/Fas ligand system. Alternatively, this decrease could be the result of the presence of the soluble Fas ligand molecule in the sera of patients with CTCL.

p16(INK4a) gene alterations are frequent in lesions of mycosis fungoides

Mycosis fungoides is usually an indolent disease that, after a variable period of time in a stable phase, evolves into a tumoral form with aggressive behavior. The molecular events that mark this progression remain essentially unknown to date, and this prompted us to investigate the hypothetical role of p16(INK4a) silencing in mycosis fungoides progression. We analyzed the three most frequent mechanisms of inactivation of the p16(INK4a) gene (deletion, promoter hypermethylation, and mutation) in nine cases with patch/plaque and tumoral lesions of mycosis fungoides. The existence of alterations was investigated by microsatellite analysis, methylation-specific polymerase chain reaction, and direct sequencing. Alterations of the p16(INK4a) gene were found in four of nine of the plaque lesions (hypermethylation in three samples and allelic loss in one sample) and seven of nine in the tumor lesions (hypermethylation in five samples and allelic loss in three samples). No case presented point mutations. Although a higher incidence of p16(INK4a) hypermethylation was observed in the cases that failed to achieve a complete remission, the limited size of our series prompted us to evaluate this finding cautiously. The results of this study therefore showed a common genetic alteration that is found more frequently in tumoral lesions than it is in plaque lesions of mycosis fungoides. It also offers data that could suggest a relationship between p16(INK4a) hypermethylation and unfavorable clinical outcome. Broader studies are needed to confirm both relationships.

Inducible loss of NF-κB activity is associated with apoptosis and Bcl-2 down-regulation in Epstein-Barr virus-transformed B lymphocytes

The Epstein–Barr virus (EBV)-encoded latent membrane protein-1 induces NF-κB activity by targeting IκBα. To understand the role of NF-κB activation in EBV-related oncogenesis, we have subcloned mutated IκBα32/36A cDNA into a pHEBo vector containing doxycycline regulatory sequences and stably transfected this construct into a lymphoblastoid cell line. Two tightly regulated clones were obtained in which IκBα32/36A was inducible in a doxycycline dose-dependent manner. Levels of inducible IκBα32/36A peaked at day 2. Inhibition of NF-κB activity was closely correlated with levels of inducible IκBα32/36A. Levels of 3 well-known NF-κB-dependent genes, CD54, p105, and endogenous IκBα, were decreased when IκBα32/36A was induced, and the growth of IκBα32/36A-induced EBV-infected cells was slightly reduced. Loss of NF-κB activity was associated with decreased Bcl-2 protein levels. Finally, the induction of apoptosis was strongly increased in IκBα32/36A-overexpressing cells. Together these results show that it is possible to control IκBα32/36A levels, ie, NF-κB activity, in EBV-infected B-lymphocytes using a doxycycline-inducible vector. Moreover, our results indicate that NF-κB can protect EBV-infected cells from apoptosis by Bcl-2. Finally, our results suggest that a cellular model with doxycycline-inducible IκBα32/36A may be useful in the identification of genuine NF-κB target genes in EBV-infected B cells.

Overexpression of p53 protein in cutaneous T cell lymphoma: relationship to large cell transformation and disease progression

The molecular mechanisms by which advanced cases of cutaneous T cell lymphoma (CTCL) (mycosis fungoides/Sezary syndrome) undergo large cell transformation (LCT) and develop the morphologic appearance of a large cell lymphoma, are undefined. We used immunohistochemical analysis and polymerase chain reaction/single strand conformational polymorphism to examine whether p53 mutations are associated with disease progression and LCT in CTCL. p53 protein immunohistochemistry was performed on 37 paraffin embedded biopsies from 27 patients with CTCL; LCT was present in 15 biopsies. Overexpression of p53 protein was found in 11 of 37 CTCL biopsies including 10 of 15 biopsies (67%) with LCT in which p53 staining was predominantly seen in large transformed cells. In contrast, p53 immunostaining was found in only one of 22 CTCL biopsies without LCT (p < 0.0004). Serial biopsies revealed acquisition of p53 expression following LCT in two patients in whom initial diagnostic biopsies without LCT were p53 negative by immunostaining. All p53 protein positive biopsies were from advanced lesions (cutaneous tumors or extracutaneous sites); none of 12 patch/plaque stage CTCL biopsies demonstrated p53 staining. Polymerase chain reaction/single strand conformational polymorphism and sequencing analysis of p53 exons 4-8 was performed in 11 cases where frozen tissue was available. No mutations were detected in six cases positive for p53 protein expression. These results suggest overexpression of p53 protein in LCT and disease progression of CTCL by a mechanism other than p53 gene mutation, in most cases.