Analysis of STAT4 expression in cutaneous T-cell lymphoma (CTCL) patients and patient-derived cell lines

Abstract

Deregulation of STAT signaling has been implicated in the pathogenesis for a variety of cancers, including CTCL. Recent reports indicate that loss of STAT4 expression is an important prognostic marker for CTCL progression and is associated with the acquisition of T helper 2 cell phenotype by malignant cells. However, little is known about the molecular mechanism behind the downregulation of STAT4 in this cancer. In the current work we test the expression of STAT4 and STAT6 via RT-PCR and/or Western Blot in CTCL lesional skin samples and in immortalized patient-derived cell lines. In these malignant cell lines we correlate the expression of STAT4 and STAT6 with the T helper (Th) phenotype markers and test the effect of Histone Deacetylase (HDAC) inhibitors and siRNA-mediated knock down of miR-155 on STAT4 expression. Our findings demonstrate that STAT4 expression correlates with Th1 phenotype, while STAT6 is associated with the Th2 phenotype. Our results further document that STAT4 and STAT6 genes are inversely regulated in CTCL. Treatment with HDAC inhibitors upregulates STAT4 expression, while at the same time decreases STAT6 expression in MyLa cells. Also, siRNA-mediated knock down of miR-155 leads to upregulation in STAT4 expression in MyLa cells. In summary, our results suggest that loss of STAT4 expression and associated switch to Th2 phenotype during Mycosis Fungoides progression may be driven via aberrant histone acetylation and/or upregulation of oncogenic miR-155 microRNA.

Histone Deacetylase Inhibitors for Cutaneous T-Cell Lymphoma

“…HDAC inhibitors may restore this balance because treatment with HDAC inhibitors have been shown to upregulate STAT-4 and decrease STAT-6 in vitro. 16 …”

“…15 The STAT family of transcription factors (STAT-3, -4, -5, and -6) are thought to have a key role in driving T-cell proliferation in CTCL. 16 STAT-4, associated with a T helper cell (Th) 1 phenotype, is downregulated in CTCL cell lines, whereas STAT-6, which is associated with Th2 phenotype, is upregulated. Change in STAT expression could contribute to the TH1 to TH2 phenotype switch seen in disease progression.…”

“…Evidence suggests that with STAT5 upregulation early in CTCL, the resulting miR-155 increase promotes proliferation of malignant T-cells and may be responsible for STAT-4 decline and conversion to TH2 phenotype. 16,17 The imbalance between STAT-4 and STAT-6 is thought to be owing to aberrant histone acetylation. MyLa cells treated with romidepsin or vorinostat, show downregulation of STAT-6 and upregulation of STAT-4, which is beneficial for CTCL.…”

MicroRNA-mediated Gene Expression in Sezary Syndrome: An Overview

“…miR-155 has been dubbed as the "bridge between inflammation and cancer" because a transient increase in this miRNA leads to activation of several types of immune cells, while constitutive up-regulation of this gene results in the development of malignancies as a result of increased genomic instability [48] [49]. In a recent study, Litvinov et al demonstrated that STAT4 is one of the targets of miR-155 [46]. In summary, STAT signaling appears to play a central role in the pathogenesis of this cancer where early in the disease STAT5 up-regulation drives the expression of miR-155 oncogene, [4].…”

“…In particular, Nebozhyn M. et al demonstrated that STAT4 protein levels in purified CD4 + cells from patients with SS were reduced or absent [45]. STAT4 activity, which is required for T helper (Th) 1 differentiation, is induced by IL-12 cytokine, which is profoundly deficient in CTCL patients [46]. STAT4 expression is subsequently lost at later clinical stages, when the disease predominantly acquires the Th2 phenotype [47].…”