Genome-wide transcriptome analysis of the STAT6-regulated genes in advanced-stage cutaneous T-cell lymphoma.

The signal transducer and activator of transcription 6 (STAT6) is a critical up-stream mediator of interleukin-13 (IL-13) and IL-4 signaling and is constitutively activated in malignant lymphocytes from Sezary syndrome (SS) and mycosis fungoides (MF), the most common subtypes of cutaneous T-cell lymphomas. By combining genome-wide expression profiling with pharmacological STAT6 inhibition, we have identified the genes regulated by STAT6 in MF/SS tumors. We found that STAT6 regulates several common pathways in MF/SS malignant lymphocytes that are associated with control of cell-cycle progression and genomic stability as well as production of Th2 cytokines. Using ex vivo skin explants from cutaneous MF tumors as well as Sezary cells derived from the blood of SS patients, we demonstrated that inhibition of STAT6 activation downregulates cytokine production and induces cell-cycle arrest in MF/SS malignant lymphocytes, inhibiting their proliferation but not their survival. Furthermore, we show that STAT6 promotes the protumoral M2-like phenotype of tumor-associated macrophages in the tumor microenvironment of advanced stage MF by upregulating the expression of genes associated with immunosuppression, chemotaxis, and tumor matrix remodeling. Thus, we show STAT6 to be a major factor in the pathogenesis and progression of MF/SS, promoting proliferation and invasion of the malignant lymphocytes while inducing a progressive depression of the antitumor immune response. Together, our results provide new insights into disease pathogenesis and offer new prospective targets for therapeutic intervention.

Dual-Positive CD4/CD8 Primary Cutaneous Peripheral T-Cell Lymphoma Previously Classified as Mycosis Fungoides a Tumor D'Emblée.

Cutaneous peripheral T-cell lymphoma, not otherwise specified represents a "waste basket" of all cases that cannot be put into another of the categories of mature cutaneous T-cell lymphoma. Previously, the sudden multifocal development of cutaneous CD4 tumors without preceding a patch or plaque stage was classified as d'emblée form of mycosis fungoides (MF). Currently, the term "MF" reserved only for the classic Alibert-Bazin type characterized by the evolution of patches, plaques, and tumors or for variants showing a similar clinical course. The authors describe a 75-year-old white woman who presented with a solitary skin tumor in the right supraclavicular region, with no lymph node or systemic involvement. Local external beam radiation treatment resulted in a complete response. The patient relapsed after 5 months with new tumors in the left neck and left upper chest. Biopsy of the lesions showed a dermal infiltrate of atypical small- to medium-sized T-lymphocytes, and immunohistochemical staining showed coexpression of CD4/CD8 in a subset of these cells, which was confirmed with flow cytometry of the tumor. Although the patient had no preceding patch or plaque stage, the authors herein report this extremely rare case of CD4/CD8 dual-positive peripheral T-cell lymphoma, not otherwise specified presented as MF d'emblée and discuss the seldom similar cases published previously.

Cutaneous Small/Medium CD4+ Pleomorphic T-Cell Lymphoma-Like Nodule in a Patient With Erythema Chronicum Migrans.

CD4+ small/medium pleomorphic T-cell lymphoma is a relatively rare subtype of cutaneous lymphoproliferative disorder with an indolent clinical behavior. The place of this condition among lymphomas is debatable. The authors describe a rare case of the direct association of CD4 small/medium pleomorphic T-cell lymphoma-like solitary nodule with Borrelia burgdorferi infection in a 5-year-old boy, discuss the reactive nature of this condition, and emphasize the importance of clinicopathological correlation.