Advances in the understanding and treatment of Cutaneous T-cell Lymphoma.

Cutaneous T-cell lymphomas (CTCL) are a heterogeneous group of non-Hodgkin's lymphomas (NHL) characterised by the clonal proliferation of malignant, skin homing T-cells. Recent advances have been made in understanding the molecular pathogenesis of CTCL. Multiple deep sequencing studies have revealed a complex genomic landscape with large numbers of novel single nucleotide variants (SNVs) and copy number variations (CNVs). Commonly perturbed genes include those involved in T-cell receptor signalling, T-cell proliferation, differentiation and survival, epigenetic regulators as well as genes involved in genome maintenance and DNA repair. In addition, studies in CTCL have identified a dominant UV mutational signature in contrast to systemic T-cell lymphomas and this likely contributes to the high tumour mutational burden. As current treatment options for advanced stages of CTCL are associated with short-lived responses, targeting these deregulated pathways could provide novel therapeutic approaches for patients. In this review article we summarise the key pathways disrupted in CTCL and discuss the potential therapeutic implications of these findings.

Spectrum of mutational signatures in T-cell lymphoma reveals a key role for UV radiation in cutaneous T-cell lymphoma.

T-cell non-Hodgkin's lymphomas develop following transformation of tissue resident T-cells. We performed a meta-analysis of whole exome sequencing data from 403 patients with eight subtypes of T-cell non-Hodgkin's lymphoma to identify mutational signatures and associated recurrent gene mutations. Signature 1, indicative of age-related deamination, was prevalent across all T-cell lymphomas, reflecting the derivation of these malignancies from memory T-cells. Adult T-cell leukemia-lymphoma was specifically associated with signature 17, which was found to correlate with the IRF4 K59R mutation that is exclusive to Adult T-cell leukemia-lymphoma. Signature 7, implicating UV exposure was uniquely identified in cutaneous T-cell lymphoma (CTCL), contributing 52% of the mutational burden in mycosis fungoides and 23% in Sezary syndrome. Importantly this UV signature was observed in CD4 + T-cells isolated from the blood of Sezary syndrome patients suggesting extensive re-circulation of these T-cells through skin and blood. Analysis of non-Hodgkin's T-cell lymphoma cases submitted to the national 100,000 WGS project confirmed that signature 7 was only identified in CTCL strongly implicating UV radiation in the pathogenesis of cutaneous T-cell lymphoma.

Frequent and Persistent PLCG1 Mutations in Sézary Cells Directly Enhance PLCγ1 Activity and Stimulate NFκB, AP-1, and NFAT Signaling.

Phospholipase C Gamma 1 (PLCG1) is frequently mutated in primary cutaneous T-cell lymphoma (CTCL). This study functionally interrogated nine PLCG1 mutations (p.R48W, p.S312L, p.D342N, p.S345F, p.S520F, p.R1158H, p.E1163K, p.D1165H, and the in-frame indel p.VYEEDM1161V) identified in Sézary Syndrome, the leukemic variant of CTCL. The mutations were demonstrated in diagnostic samples and persisted in multiple tumor compartments over time, except in patients who achieved a complete clinical remission. In basal conditions, the majority of the mutations confer PLCγ1 gain-of-function activity through increased inositol phosphate production and the downstream activation of NFκB, AP-1, and NFAT transcriptional activity. Phosphorylation of the p.Y783 residue is essential for the proximal activity of wild-type PLCγ1, but we provide evidence that activating mutations do not require p.Y783 phosphorylation to stimulate downstream NFκB, NFAT, and AP-1 transcriptional activity. Finally, the gain-of-function effects associated with the p.VYEEDM1161V indel suggest that the C2 domain may have a role in regulating PLCγ1 activity. These data provide compelling evidence to support the development of therapeutic strategies targeting mutant PLCγ1.

Contribution of STAT3 and RAD23B in Primary Sézary Cells to Histone Deacetylase Inhibitor FK228 Resistance.

FK228 (romidepsin) and suberoylanilide hydroxamic acid (vorinostat) are histone deacetylase inhibitors (HDACi) approved by the US Food and Drug Administration for cutaneous T-cell lymphoma (CTCL), including the leukemic subtype Sézary syndrome. This study investigates RAD23B and STAT3 gene perturbations in a large cohort of primary Sézary cells and the effect of FK228 treatment on tyrosine phosphorylation of STAT3 (pYSTAT3) and RAD23B expression. We report RAD23B copy number variation in 10% (12/119, P ≤ 0.01) of SS patients, associated with reduced mRNA expression (P = 0.04). RAD23B knockdown in a CTCL cell line led to a reduction in FK228-induced apoptosis. Histone deacetylase inhibitor treatment significantly reduced pYSTAT3 in primary Sézary cells and was partially mediated by RAD23B. A distinct pattern of RAD23B-pYSTAT3 co-expression in primary Sézary cells was detected. Critically, Sézary cells harboring the common STAT3 Y640F variant were less sensitive to FK228-induced apoptosis and exogenous expression of STAT3 Y640F, and D661Y conferred partial resistance to STAT3 transcriptional inhibition by FK228 (P ≤ 0.0024). These findings suggest that RAD23B and STAT3 gene perturbations could reduce sensitivity to histone deacetylase inhibitors in SS patients.

Candidate driver genes involved in genome maintenance and DNA repair in Sézary syndrome.

Sézary syndrome (SS) is a leukemic variant of cutaneous T-cell lymphoma (CTCL) and represents an ideal model for study of T-cell transformation. We describe whole-exome and single-nucleotide polymorphism array-based copy number analyses of CD4(+) tumor cells from untreated patients at diagnosis and targeted resequencing of 101 SS cases. A total of 824 somatic nonsynonymous gene variants were identified including indels, stop-gain/loss, splice variants, and recurrent gene variants indicative of considerable molecular heterogeneity. Driver genes identified using MutSigCV include POT1, which has not been previously reported in CTCL; and TP53 and DNMT3A, which were also identified consistent with previous reports. Mutations in PLCG1 were detected in 11% of tumors including novel variants not previously described in SS. This study is also the first to show BRCA2 defects in a significant proportion (14%) of SS tumors. Aberrations in PRKCQ were found to occur in 20% of tumors highlighting selection for activation of T-cell receptor/NF-κB signaling. A complex but consistent pattern of copy number variants (CNVs) was detected and many CNVs involved genes identified as putative drivers. Frequent defects involving the POT1 and ATM genes responsible for telomere maintenance were detected and may contribute to genomic instability in SS. Genomic aberrations identified were enriched for genes implicated in cell survival and fate, specifically PDGFR, ERK, JAK STAT, MAPK, and TCR/NF-κB signaling; epigenetic regulation (DNMT3A, ASLX3, TET1-3); and homologous recombination (RAD51C, BRCA2, POLD1). This study now provides the basis for a detailed functional analysis of malignant transformation of mature T cells and improved patient stratification and treatment.

Independent Loss of Methylthioadenosine Phosphorylase (MTAP) in Primary Cutaneous T-Cell Lymphoma.

Methylthioadenosine phosphorylase (MTAP) and the tumor suppressor genes CDKN2A-CDKN2B are frequently deleted in malignancies. The specific role of MTAP in cutaneous T-cell lymphoma subgroups, mycosis fungoides (MF) and Sézary syndrome (SS), is unknown. In 213 skin samples from patients with MF/SS, MTAP copy number loss (34%) was more frequent than CDKN2A (12%) in all cutaneous T-cell lymphoma stages using quantitative reverse transcription PCR. Importantly, in early stage MF, MTAP loss occurred independently of CDKN2A loss in 37% of samples. In peripheral blood mononuclear cells from patients with SS, codeletion with CDKN2A occurred in 18% of samples but loss of MTAP alone was uncommon. In CD4(+) cells from SS, reduced MTAP mRNA expression correlated with MTAP copy number loss (P < 0.01) but reduced MTAP expression was also detected in the absence of copy number loss. Deep sequencing of MTAP/CDKN2A-CDKN2B loci in 77 peripheral blood mononuclear cell DNA samples from patients with SS did not show any nonsynonymous mutations, but read-depth analysis suggested focal deletions consistent with MTAP and CDKN2A copy number loss detected with quantitative reverse transcription PCR. In a cutaneous T-cell lymphoma cell line, promoter hypermethylation was shown to downregulate MTAP expression and may represent a mechanism of MTAP inactivation. In conclusion, our findings suggest that there may be selection in early stages of MF for MTAP deletion within the cutaneous tumor microenvironment.

Regulation of T-plastin expression by promoter hypomethylation in primary cutaneous T-cell lymphoma.

T-plastin (PLS3) is an actin-bundling protein normally expressed in epithelial cells but absent in cells of hematopoietic origin. Aberrant PLS3 expression has been demonstrated in lymphocytes from Sézary syndrome (SS) patients and has been proposed as a biomarker for SS; however, the mechanism underlying dysregulation of PLS3 has not been determined. In this study, PLS3 mRNA expression was demonstrated in 21/35 (60%) SS patients and in 3/8 (38%) mycosis fungoides patients, all of whom had clonal blood involvement. No evidence for PLS3 mutations within coding or promoter regions was found, but significant hypomethylation of CpG dinucleotides 95-99 within the PLS3 CpG island was observed and this was restricted to the PLS3+ population. A polyclonal antibody specific to PLS3 was raised to examine coexpression of PLS3 with a panel of T-cell differentiation markers. All PLS3+ cells were CD3+CD4+ and CD26-, suggesting that loss of CD26 is consistently associated with gain of PLS3, whereas all other markers were distributed heterogeneously. However, a patient-specific TCR copy number assay also demonstrated heterogeneity in PLS3 expression in tumor cell populations. Importantly, our findings demonstrate PLS3 expression in the majority of SS patients and provide insight into the molecular regulation of PLS3 expression in CTCL.

Vorinostat combined with bexarotene for treatment of cutaneous T-cell lymphoma: in vitro and phase I clinical evidence supporting augmentation of retinoic acid receptor/retinoid X receptor activation by histone deacetylase inhibition.

The retinoid X receptor (RXR)-agonist bexarotene and the histone deacetylase inhibitor (HDACI) vorinostat are each established monotherapies for cutaneous T-cell lymphomas (CTCLs). We investigated the combination of HDACI and retinoic acid receptor (RAR)/RXR agonists in vitro and in a phase I, multicenter, open-label, two-part dose-escalation study. The combination of bexarotene with a HDACI in vitro leads to cooperative activation of gene transcription and reduction of cell viability in human tumor cell lines. The primary clinical objective was to determine the maximum tolerated dose (MTD) of bexarotene plus vorinostat in 23 patients with CTCLs. The MTD for part I was established at vorinostat 200 mg/day plus bexarotene 300 mg/m(2)/day. The MTD for part II was not reached. Four patients had an objective response and seven patients experienced pruritus relief. We conclude that concomitant administration of vorinostat and bexarotene is feasible only if lower doses of each drug are administered relative to the product label monotherapy doses.

Survival outcomes and prognostic factors in mycosis fungoides/Sézary syndrome: validation of the revised International Society for Cutaneous Lymphomas/European Organisation for Research and Treatment of Cancer staging proposal.

PURPOSE: We have analyzed the outcome of mycosis fungoides (MF) and Sézary syndrome (SS) patients using the recent International Society for Cutaneous Lymphomas (ISCL)/European Organisation for Research and Treatment of Cancer (EORTC) revised staging proposal. PATIENTS AND METHODS: Overall survival (OS), disease-specific survival (DSS), and risk of disease progression (RDP) were calculated for a cohort of 1,502 patients using univariate and multivariate models. RESULTS: The mean age at diagnosis was 54 years, and 71% of patients presented with early-stage disease. Disease progression occurred in 34%, and 26% of patients died due to MF/SS. A significant difference in survival and progression was noted for patients with early-stage disease having patches alone (T1a/T2a) compared with those having patches and plaques (T1b/T2b). Univariate analysis established that (1) advanced skin and overall clinical stage, increased age, male sex, increased lactate dehydrogenase (LDH), and large-cell transformation were associated with reduced survival and increased RDP; (2) hypopigmented MF, MF with lymphomatoid papulosis, and poikilodermatous MF were associated with improved survival and reduced RDP; and (3) folliculotropic MF was associated with an increased RDP. Multivariate analysis established that (1) advanced skin (T) stage, the presence in peripheral blood of the tumor clone without Sézary cells (B0b), increased LDH, and folliculotropic MF were independent predictors of poor survival and increased RDP; (2) large-cell transformation and tumor distribution were independent predictors of increased RDP only; and (3) N, M, and B stages; age; male sex; and poikilodermatous MF were only significant for survival. CONCLUSION: This study has validated the recently proposed ISCL/EORTC staging system and identified new prognostic factors.

Final results from a multicenter, international, pivotal study of romidepsin in refractory cutaneous T-cell lymphoma.

PURPOSE: The primary objective of this study was to confirm the efficacy of romidepsin in patients with treatment refractory cutaneous T-cell lymphoma (CTCL). PATIENTS AND METHODS: This international, pivotal, single-arm, open-label, phase II study was conducted in patients with stage IB to IVA CTCL who had received one or more prior systemic therapies. Patients received romidepsin as an intravenous infusion at a dose of 14 mg/m(2) on days 1, 8, and 15 every 28 days. Response was determined by a composite assessment of total tumor burden including cutaneous disease, lymph node involvement, and blood (Sézary cells). RESULTS: Ninety-six patients were enrolled and received one or more doses of romidepsin. Most patients (71%) had advanced stage disease (≥ IIB). The response rate was 34% (primary end point), including six patients with complete response (CR). Twenty-six of 68 patients (38%) with advanced disease achieved a response, including five CRs. The median time to response was 2 months, and the median duration of response was 15 months. A clinically meaningful improvement in pruritus was observed in 28 (43%) of 65 patients, including patients who did not achieve an objective response. Median duration of reduction in pruritus was 6 months. Drug-related adverse events were generally mild and consisted mainly of GI disturbances and asthenic conditions. Nonspecific, reversible ECG changes were noted in some patients. CONCLUSION: Romidepsin has significant and sustainable single-agent activity (including improvement in pruritus) and an acceptable safety profile, making it an important therapeutic option for treatment refractory CTCL.

MicroRNA expression in Sezary syndrome: identification, function, and diagnostic potential.

MicroRNAs are commonly aberrantly expressed in many cancers. Very little is known of their role in T-cell lymphoma, however. We therefore elucidated the complete miRNome of purified T cells from 21 patients diagnosed with Sézary Syndrome (SzS), a rare aggressive primary cutaneous T-cell (CD4(+)) lymphoma. Unsupervised cluster analysis of microarray data revealed that the microRNA expression profile was distinct from CD4(+) T-cell controls and B-cell lymphomas. The majority (104 of 114) of SzS-associated microRNAs (P < .05) were down-regulated and their expression pattern was largely consistent with previously reported genomic copy number abnormalities and were found to be highly enriched (P < .001) for aberrantly expressed target genes. Levels of miR-223 distinguished SzS samples (n = 32) from healthy controls (n = 19) and patients with mycosis fungoides (n = 11) in more than 90% of samples. Furthermore, we demonstrate that the down-regulation of intronically encoded miR-342 plays a role in the pathogenesis of SzS by inhibiting apoptosis, and describe a novel mechanism of regulation for this microRNA via binding of miR-199a* to its host gene. We also provide the first in vivo evidence for down-regulation of the miR-17-92 cluster in malignancy and demonstrate that ectopic miR-17-5p expression increases apoptosis and decreases cell proliferation in SzS cells.

Downregulation of Fas gene expression in Sézary syndrome is associated with promoter hypermethylation.

Sézary Syndrome (SS) is an aggressive leukemic variant of primary cutaneous T-cell lymphoma characterized by the presence of tumor or Sézary cells that generally display a mature memory T-cell immunophenotype. Sézary cells proliferate poorly and therefore their accumulation may be due to defective T-cell homeostasis involving resistance to apoptosis. In this study, we analyzed Fas expression in CD4+ lymphocytes at the mRNA and protein levels in a large cohort of SS patients as compared with healthy controls. Fas mRNA expression was dysregulated in 34/47 patients, with significant under- and overexpression of Fas mRNA detected in 21 and 13 patients respectively (P<0.01). Examination of cell-surface Fas expression showed correlation with the observed downregulation of mRNA in CD4+ T cells. Mutational analysis demonstrated that functional FAS gene mutations are rare. Moreover, 16 SS patients who showed significant under-expression of Fas mRNA also showed significant positional hypermethylation within the FAS CpG island, which was not present in healthy controls or SS patients determined to have normal or overexpression of Fas mRNA. These data demonstrate that dysregulation of Fas expression is a common feature of SS, and provide a rationale for targeted therapies to restore the extrinsic Fas-dependent apoptotic pathway in this malignancy.

Fine-mapping chromosomal loss at 9p21: correlation with prognosis in primary cutaneous diffuse large B-cell lymphoma, leg type.

Primary cutaneous diffuse large B-cell lymphoma, leg type (PCLBCL, LT) is the most aggressive type of primary cutaneous B-cell lymphoma. In a recent study on 12 patients it was found that inactivation of CDKN2A by either deletion of 9p21.3 or promoter hypermethylation is correlated with a worse prognosis. In the present EORTC multicenter study, skin biopsies of 64 PCLBCL, LT patients were analyzed by multiplex ligation-dependent probe amplification to validate these previous results and to fine-map the losses in this region. Although no minimal common region of loss could be identified, most homozygous loss was observed in the CDKN2A gene (43 of 64; 67%) encoding p16 and p14ARF. Promoter hypermethylation of p16 and p14ARF was found in six and zero cases, respectively. Survival was markedly different between patients with versus without aberrations in the CDKN2A gene (5-year disease-specific survival 43 versus 70%; P=0.06). In conclusion, our results confirm that deletion of chromosome 9p21.3 is found in a considerable proportion of PCLBCL, LT patients and that inactivation of the CDKN2A gene is associated with an unfavorable prognosis. In most patients the deletion involves a large area of at least several kilobase pairs instead of a small minimal common region.

An unusual case of granulomatous slack skin disease with necrobiosis.

Granulomatous slack skin disease (GSS) is a very rare form of T-cell lymphoma, with only 52 cases reported in the literature. In the recent World Health Organization-European Organization for Research and Treatment of Cancer consensus classification GSS is considered to be a variant of mycosis fungoides. We describe a patient with GSS and histologic evidence of necrobiosis, which has not been previously reported.

A genomic and expression study of AP-1 in primary cutaneous T-cell lymphoma: evidence for dysregulated expression of JUNB and JUND in MF and SS.

Activator protein 1 (AP-1) consists of a group of transcription factors including the JUN and FOS family proteins with diverse biological functions. This study assessed the genomic and expression status of the AP-1 transcription factors in primary cutaneous T-cell lymphoma (CTCL) by using immunohistochemistry (IHC), Affymetrix expression microarray, real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and fluorescent in situ hybridization (FISH). IHC showed JUNB protein expression in tumor cells from 17 of 33 cases of Sezary syndrome (SS) and JUND protein expression in 16 of 23 mycosis fungoides cases. There was no correlation between JUNB and CD30 expression. However, 7 of 12 JUNB-positive SS cases expressed both phosphorylated and total extracellular signal-regulated kinase (ERK) 1/2 mitogen-activated protein kinase (MAPK) proteins. Expression microarray showed over threefold increased expression of JUNB in three of six SS patients and similar findings were also noted after re-analysis of previously published data. Real-time RT-PCR confirmed the overexpression of JUNB in four SS cases and of JUND in three of four cases. FISH showed increased JUNB copy number in four of seven SS cases. These findings suggest that deregulation of AP-1 expression in CTCL is the result of aberrant expression of JUNB and possible JUND resulting from genomic amplification and constitutive activation of ERK1/2 MAPK in this type of lymphoma.

Genital herpes masquerading as a cutaneous T-cell lymphoma: a report of two cases.

Genital herpes simplex virus (HSV) infection is usually a straightforward clinical diagnosis, rarely requiring histological confirmation. We report two cases of immunosuppressed patients in which the clinical and pathological features were initially suspicious for cutaneous lymphoma with a T-cell clone detected in one case. A diagnosis of HSV infection was eventually made on the basis of histological features and confirmed with immunohistochemistry.

Efficacy and tolerability of currently available therapies for the mycosis fungoides and Sezary syndrome variants of cutaneous T-cell lymphoma.

Primary cutaneous T-cell lymphomas are a heterogenous group of non-Hodgkin lymphomas. The characteristic clinicopathologic and immunophenotypic features and prognoses of the various cutaneous lymphomas have been recently described by the World Health Organization and European Organization for Research and Treatment of Cancer. Cutaneous T-cell lymphoma variants include mycosis fungoides and Sezary syndrome, which are generally associated, respectively, with indolent and aggressive clinical courses and are the subject of this review. Currently utilized treatments for cutaneous T-cell lymphoma include skin-directed therapies (topical agents such as corticosteroids, mechlorethamine, carmustine, and retinoids, phototherapy, superficial radiotherapy, and total skin electron beam therapy), systemic therapies (photophoresis, retinoids, denileukin diftitox, interferons, and chemotherapy), and stem cell transplantation (autologous and allogeneic). This review will describe recent advances in our understanding of the biology (immunologic, cytogenetic, and genetic) of cutaneous T-cell lymphomas and discuss the efficacy and tolerability of the current therapeutic options for cutaneous T-cell lymphomas. Disease progression in over 20% of patients with early stages of disease and the current lack of a definitive treatment which produces durable responses in advanced stages of disease indicates a critical unmet need in CTCL. New insights into the molecular and immunologic changes associated with cutaneous T-cell lymphomas should ultimately lead to the identification of novel therapeutic targets and the development of improved therapeutic options for patients with these malignancies.

Lack of suppressive CD4+CD25+FOXP3+ T cells in advanced stages of primary cutaneous T-cell lymphoma.

Mycosis fungoides and its leukemic variant, Sezary syndrome, are the most common primary cutaneous T-cell lymphomas (CTCLs). In an ex vivo study, we investigated the percentage, phenotype, and suppressive function of CD4+CD25+ regulatory T cells (Tregs) from peripheral blood of CTCL patients. The percentage of Tregs did not differ significantly between patients and controls. Functional assays demonstrated a dichotomy in Treg function: in four out of 10 patients CD4+CD25+ T cells were incapable of suppressing autologous CD4+CD25- T-cell proliferation, whereas suppressive function was intact in the other six patients. Suppressive activity of Tregs inversely correlated with the peripheral blood tumor burden. T-plastin gene expression, used as a Sezary cell marker, confirmed that Sezary cells were heterogeneous for CD25 expression. Mixed lymphocyte reactions demonstrated that CD4+CD25- T cells from patients who lacked functional Tregs were susceptible to suppression by Tregs from healthy controls, and had not become suppressive themselves. Furthermore, we found reduced expression of Foxp3 in the CD4+CD25+ Tregs of these patients relative to the other six CTCL patients and controls. Our findings thus indicate a dysfunction of peripheral Tregs in certain CTCL patients, which correlates with tumor burden.

Molecular analysis of T-cell receptor beta genes in cutaneous T-cell lymphoma reveals Jbeta1 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.