Metastatic melanoma represents a complex and heterogeneous disease for which there are no therapies to improve patient survival. Recent expression profiling of melanoma cell lines identified two transcription signatures, respectively, corresponding with proliferative and invasive cellular phenotypes. A model derived from these findings predicts that in vivo melanoma cells may switch between these states. Here, DNA microarray-characterized cell lines were subjected to in vitro characterization before s.c. injection into immunocompromised mice. Tumor growth rates were measured and postexcision samples were assessed by immunohistochemistry to identify invasive and proliferative signature cells. In vitro tests showed that proliferative signature melanoma cells are faster growing but less motile than invasive signature cells. In vivo proliferative signature cells initiated tumor growth in 14 F 3 days postinjection. By comparison, invasive signature cells required a significantly longer (P < 0.001) period of 59 F 11 days. Immunohistochemistry showed that regardless of the seed cell signature, tumors showed evidence for both proliferative and invasive cell types. Furthermore, proliferative signature cell types were detected most frequently in the peripheral margin of growing tumors. These data indicate that melanoma cells undergo transcriptional signature switching in vivo likely regulated by local microenvironmental conditions. Our findings challenge previous models of melanoma progression that evoke one-way changes in gene expression. We present a new model for melanoma progression that accounts for transcription signature plasticity and provides a more rational context for explaining observed melanoma biology. [Cancer Res 2008;68(3):650-6]

In this study we investigated the role of interleukin-15 (IL-15) in the immunobiology of cutaneous T-cell lymphoma (CTCL) cells. Using cell culture techniques, reverse transcriptase-polymerase chain reaction (RT-PCR), and immunhistochemistry we found that IL-15, like IL-7, is a growth factor for the Sézary cell line SeAx and that both cytokines prolonged the survival of malignant T cells directly isolated from Sézary syndrome (SS) patients. Both IL-15 and IL-7 were more potent than IL-2. IL-4 and IL-9, whose receptors share the same gamma chain with the receptors of IL-2, IL-7, and IL-15, did not sustain the growth of CTCL cells, indicating that signaling through the common gamma chain (γc) is not sufficient for continuous growth. IL-13 and tumor necrosis factor-α (TNF-α) had no effect. IL-7 and IL-15 also supported the growth of SeAx cells in the presence of the apoptosis inducing agents dexamethasone and retinoic acid. The analysis of patient Sézary cells and three CTCL cell lines by RT-PCR showed that all these cells expressed IL-15 mRNA, but only a few (25%) produced IL-7 mRNA. Immunohistological analyses of skin biopsy samples of SS and Mycosis fungoides patients showed immunoreactivity for IL-15 in basal cell layer keratinocytes and in the infiltrating lymphocytes. We conclude that IL-15 is a growth or viability factor for CTCL-derived cell lines or shortly cultivated Sézary cells. The findings that IL-15 mRNA can be detected in Sézary syndrome peripheral blood mononuclear cells and that the IL-15 protein is detected in skin sections from CTCL patients suggest that IL-15 plays an important role in the biology of CTCL.

Interleukin-7 (IL-7) and IL-15 have been recently identified as growth factors for cuta-neous 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 paral-leled 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. (Blood. 2001;98:2778-2783)

On testing cutaneous T cell lymphoma cell lines and skin lesions, we found that the transcription factors STAT2, STAT3, STAT5, and STAT6 (STAT, signal transducer and activator of transcription) were present in the nuclei of these cells and that the binding to their specific DNA binding sites was stimulated by interleukin-7 and interleukin-15. DNA binding studies also revealed the presence of three additional DNA factors in cutaneous T cell lymphoma cells that bound to the same sequences and could also be stimulated by interleukin-7 and interleukin-15. One of these novel factors was also present in the adult T cell leukemia cell line Jurkat and malignant T cells from the blood of Sézary syndrome patients, but not in normal peripheral blood lymphocytes. It may therefore be a marker of T cell leukemia. It seems to interfere with the binding of STAT1 to the sis inducible element, suggesting that the DNA binding activity of STAT1 in cutaneous T cell lymphoma cells is disturbed.

We have analysed the interplay of glucocorticoid receptor (GR) and the lymphocyte‐specific factor Oct‐2A with transient co‐transfection assays. Our data confirm our previously described observation that GR and the apparently unrelated factors belonging to the Octamer family can synergize when permitted to bind in cis. However, when GR binding sites are not present in the reporter genes, we observe that the action of the cloned factor Oct‐2A expressed in HeLa cells is strongly inhibited in the presence of active GR molecules. We can demonstrate that this GR‐mediated inhibition of Oct‐2A action is neither due to competitive binding to DNA target sites nor to a reduction of DNA binding competent Oct‐2A in the transfected cells. We observe that the phenomenon is not reciprocal, since co‐expression of Oct‐2A does not inhibit GR‐dependent transcription activation. Furthermore, we provide evidence that the observed GR‐Oct‐2A interference may be dependent on the type of cell line hosting the co‐transfected molecules. We consider it likely that the GR‐mediated inhibition is due to the exhaustion of some rate‐limiting co‐activators.