CD4⁺CD25⁺FOXP3⁺ malignant T cells in Sézary syndrome are not necessarily functional regulatory T cells

Evaluation of Low-Dose, Low-Frequency Oral Psoralen-UV-A Treatment With or Without Maintenance on Early-Stage Mycosis Fungoides: A Randomized Clinical Trial

Importance

Psoralen-UV-A (PUVA) photochemotherapy is standard first-line treatment for skin-limited, early-stage mycosis fungoides capable of producing high initial complete response (CR) rates. However, much remains unknown about PUVA's therapeutic mechanisms, optimal duration and frequency of treatment, dose escalation, or use as maintenance therapy.

Objectives

To evaluate low-dose, low-frequency PUVA, and whether maintenance treatment extends disease-free remission in patients with mycosis fungoides.

Design, Setting, and Participants

This prospective randomized clinical trial with defined PUVA dosing regimen was carried out in 5 centers (Graz, Vienna, Hietzing, Innsbruck, and Salzburg) across Austria. Patients with stage IA to IIA mycosis fungoides (n = 27) were enrolled in the study beginning March 13, 2013, with the last patient enrolled March 21, 2016. These patients were treated with oral 8-methoxypsoralen followed by UV-A exposure 2 times per week for 12 to 24 weeks until CR. Patients with CR were randomized to PUVA maintenance for 9 months (14 total exposures) or no maintenance. The study was conducted from April 27, 2012, to July 27, 2018. Data analysis of the primary end point was of the intention-to-treat population, and the secondary end point analysis was of the evaluable population.

Main Outcomes and Measures

Efficacy of the PUVA regimen was determined by the rate of CR as defined by a modified severity-weighted assessment tool (mSWAT) score reduction to 0. Levels of proinflammatory molecules in serum and histologic features and percentage of clonal T cells in skin were assessed to search for biomarkers of clinical response.

Results

In 27 patients with mycosis fungoides, 19 (70%) were male with mean (range) age 61 (30-80) years. At baseline, patients with CR had a mean (range) mSWAT score of 18.6 (1-66) compared with 16.8 (3-46) in patients with partial response. The 12- to 24-week PUVA induction regimen reduced the mSWAT score in all patients and led to CR in 19 (70%) of 27 patients and a low mean cumulative UV-A dose of 78.5 J/cm2. The subsequent standardized 9-month PUVA maintenance phase prolonged median (range) disease-free remission from 4 (1-20) months to 15 (1-54) months (P = .02). High density of histologic infiltrate and high percentage of clonal TCR sequences in skin biopsy specimens at baseline were inversely associated with therapeutic response. No severe adverse effects were seen during the PUVA induction or maintenance phase.

Conclusions and Relevance

This proof-of-concept study identifies potential biomarkers for therapeutic response to PUVA in mycosis fungoides; it also demonstrates that low-dose, low-frequency PUVA appears to be highly effective, and maintenance treatment may extend disease-free remission.

Trial Registration

ClinicalTrials.gov identifier: NCT01686594.

Therapeutic reduction of cell-mediated immunosuppression in mycosis fungoides and Sézary syndrome

Tumor progression is associated with progressive immunosuppression mediated in part by T regulatory cell(s) (Treg) and/or myeloid-derived suppressor cell(s) (MDSC). Development of strategies to reduce populations of immune cells with suppressive function in cancer patients may enable the induction or recovery of immunity against tumor cells, which may limit or reverse disease progression. With a goal of developing Treg and MDSC neutralizing strategies to treat mycosis fungoides (MF) and Sézary syndrome (SzS), we determined the association between disease stage and suppressor cell populations in patients with MF/SzS, including those responding to therapy. We found elevations in Treg populations, across Treg subtypes, in patients with SzS, and these Treg markedly suppressed proliferation of autologous CD4+CD25- responder T cells. Interestingly, while MDSC numbers were not increased in MF/SzS patients, MDSC from patients with stage IB and above produced significantly more reactive oxygen species than those from stage IA MF patients and control cohorts. Therapy with the CD25-targeting agent denileukin diftitox or IFN-α2b was associated with a reduction in Treg numbers or MDSC function, respectively. These studies identify potential mechanisms of action for these therapies and support the development of coordinated strategies targeting both Treg and MDSC activities in patients with MF/SzS.

FoxP3-Positive T-Regulatory Cells in Lymph Nodes with Mycosis Fungoides and Sézary Syndrome

Mycosis fungoides and Sézary syndrome are indolent cutaneous T-cell lymphomas, with skin-associated peripheral lymph nodes being the most frequent extracutaneous site of involvement. Acquisition of functional properties of regulatory T-cells by malignant T-cells in advanced disease may contribute to immunosuppression. Whereas previous studies examining FoxP3 protein expression in mycosis fungoides and Sézary syndrome have focused on skin specimens, little data are available on lymph nodes from patients with these conditions. In this study we examined FoxP3+ regulatory T-cells in lymph nodes from 26 patients with mycosis fungoides and Sézary syndrome and correlated the findings with clinical data, molecular assays for T-cell clonality, and flow cytometry. Except for one case of Sézary syndrome in which malignant T-cells expressed FoxP3 protein, a significantly lower number of FoxP3-expressing cells occurred in lymph nodes that were clearly involved with lymphoma as compared to uninvolved nodes. Cox proportional hazards model showed that lymph node rating and histological evidence of transformation, but not number of FoxP3+ cells, were factors significantly associated with adverse prognosis. We speculate that modulation of FoxP3+ cells in lymph nodes involved with lymphoma might play a role in disease progression. Attainment of a regulatory T-cell phenotype by a subset of lymphoma cells might signal a poor prognosis.

Sézary Syndrome

Sézary syndrome (SS), a type of cutaneous T-cell lymphoma with a poor prognosis, is characterized by erythroderma and leukemic involvement. Because of the rarity of SS and difficulty in diagnosis, data on this aggressive malignancy are scarce. In this review, the diagnosis and pathology of SS are summarized and an update is provided, highlighting microscopic features and novel molecular findings. The diagnostic challenge of SS is described, with an emphasis on the differential diagnosis of erythroderma and key points in distinguishing SS from other cutaneous T-cell malignancies. Finally, the prognosis is discussed, focusing on large, recent studies of SS patients.