Type I IFN innate immune response to adenovirus-mediated IFN-gamma gene transfer contributes to the regression of cutaneous lymphomas.

The fact that adenoviral vectors activate innate immunity and induce type I IFNs has not been fully appreciated in the context of cancer gene therapy. Type I IFNs influence different aspects of human immune response and are believed to be crucial for efficient tumor rejection. We performed transcriptional profiling to characterize the response of cutaneous lymphomas to intralesional adenovirus-mediated IFN-gamma (Ad-IFN-gamma) gene transfer. Gene expression profiles of skin lesions obtained from 19 cutaneous lymphoma patients before and after treatment with Ad-IFN-gamma revealed a distinct gene signature consisting of IFN-gamma- and numerous IFN-alpha-inducible genes (type II- and type I-inducible genes, respectively). The type I IFN response appears to have been induced by the vector itself, and its complexity, in terms of immune activation, was potentiated by the IFN-gamma gene insert. Intralesional IFN-gamma expression together with the induction of a combined type I/II IFN response to Ad-IFN-gamma gene transfer seem to underlie the objective (measurable) clinical response of the treated lesions. Biological effects of type I IFNs seem to enhance those set in motion by the transgene, in our case IFN-gamma. This combination may prove to be of therapeutic importance in cytokine gene transfer using Ads.

Human CD271-positive melanoma stem cells associated with metastasis establish tumor heterogeneity and long-term growth.

Human melanoma is composed of distinct cell types reminiscent of neural crest derivatives and contains multipotent cells that express the neural crest stem cell markers CD271(p75(NTR)) and Sox10. When isolated from solid tumors by using a method that leaves intact cell surface epitopes, CD271-positive, but not CD271-negative, cells formed tumors on transplantation into nude or nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. These tumors fully mirrored the heterogeneity of the parental melanoma and could be passaged more than 5 times. In contrast, in more immunocompromised NOD/SCID/IL2rγ(null) mice, or in natural killer cell-depleted nude or NOD/SCID mice, both CD271-positive and CD271-negative tumor cell fractions established tumors. However, tumors resulting from either fraction did not phenocopy the parental tumors, and tumors derived from the CD271-negative cell fraction could not be passaged multiple times. Together, our findings identify CD271-positive cells as melanoma stem cells. Our observation that a relatively high frequency of CD271/Sox10-positive cells correlates with higher metastatic potential and worse prognosis further supports that CD271-positive cells within human melanoma represent genuine cancer stem cells.

In vivo switching of human melanoma cells between proliferative and invasive states.

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 +/- 3 days postinjection. By comparison, invasive signature cells required a significantly longer (P < 0.001) period of 59 +/- 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.