The X-linked inhibitor of apoptosis protein (XIAP) is involved in melanoma invasion by regulating cell migration and survival.

BACKGROUND: The X-linked inhibitor of apoptosis (XIAP) is a potent cellular inhibitor of apoptosis, based on its unique capability to bind and to inhibit caspases. However, XIAP is also involved in a number of additional cellular activities independent of its caspase inhibitory function. The aim of this study was to investigate whether modulation of XIAP expression affects apoptosis-independent functions of XIAP in melanoma cells, restores their sensitivity to apoptosis and/or affects their invasive and metastatic capacities. METHODS: XIAP protein levels were analyzed by immunohistochemical staining of human tissues and by Western blotting of melanoma cell lysates. The effects of pharmacological inhibition or of XIAP down-regulation were investigated using ex-vivo and transwell invasion assays. The biological effects of XIAP down-regulation on melanoma cells were analyzed in vitro using BrdU/PI, nucleosome quantification, adhesion and migration assays. In addition, new XIAP binding partners were identified by co-immunoprecipitation followed by mass spectrometry. RESULTS: Here we found that the expression of XIAP is increased in metastatic melanomas and in invasive melanoma-derived cell lines. We also found that the bivalent IAP antagonist birinapant significantly reduced the invasive capability of melanoma cells. This reduction could be reproduced by downregulating XIAP in melanoma cells. Furthermore, we found that the migration of melanoma cells and the formation of focal adhesions at cellular borders on fibronectin-coated surfaces were significantly reduced upon XIAP knockdown. This reduction may depend on an altered vimentin-XIAP association, since we identified vimentin as a new binding partner of XIAP. As a corollary of these molecular alterations, we found that XIAP down-regulation in melanoma cells led to a significant decrease in invasion of dermal skin equivalents. CONCLUSION: From our data we conclude that XIAP acts as a multifunctional pro-metastatic protein in skin melanomas and, as a consequence, that XIAP may serve as a therapeutic target for these melanomas.

Loss of epidermal MMP-14 expression interferes with angiogenesis but not with re-epithelialization.

Synthesis and activation of matrix metalloproteinases during wound healing are important for remodeling the extracellular matrix and modulating various cellular functions. The membrane-type 1 matrix metalloproteinase (MMP-14) has been shown to play a key role during these processes. To analyze the function of epidermal-derived MMP-14 during skin repair we generated mice lacking MMP-14 expression in the epidermis (MMP-14(ep-/-)). These mice displayed overall normal skin morphology and epidermal differentiation patterns. Wound repair in MMP-14(ep-/-) followed the same kinetics as in wild type mice (MMP-14(ep+/+)), and infiltration of neutrophils, leukocytes, and macrophages into the wound site was comparable. Microscopic analysis showed no altered re-epithelialization in the absence of epidermal MMP-14. Furthermore, epidermal differentiation at the end of the repair process and scar formation was normal. However, at day 14 post wounding, sustained angiogenesis was observed in MMP-14(ep-/-) mice in contrast to control mice. Interestingly, decreased levels of endostatin were detected in wound lysates of MMP-14(ep-/-) mice as well as in cultured keratinocytes. Taken together, these data indicate that MMP-14 expression in keratinocytes is dispensable for skin homeostasis and repair, but plays a crucial role in the epidermal-dermal crosstalk leading to modulation of vessel density.

Human leukocyte antigen class I, MHC class I chain-related molecule A, and CD8+/regulatory T-cell ratio: which variable determines survival of cervical cancer patients?

PURPOSE: To investigate the effect of intraepithelial tumor-infiltrating lymphocytes (ieTIL) and their ligands expressed by cervical tumor cells on the outcome of cervical cancer patients. EXPERIMENTAL DESIGN: The prognostic value of ieTILs was investigated in 115 cases of cervical cancer. T-cell subsets, CD57(+) cells, and regulatory T cells (Treg) were enumerated. The associations of these different ieTIL subtypes with human leukocyte antigen (HLA) class I and MHC class I chain-related molecule A (MICA) expression were determined in relation to clinical variables and patient survival. RESULTS: Survival analysis showed that a high number of intraepithelial Treg (FoxP3(+)), a low CD8(+)/regulatory T-cell ratio, and a weak HLA-A expression were all associated with worse survival (P=0.034, 0.025, and 0.033, respectively, log-rank test). Further stratification of patient groups based on HLA-A-MICA expression and HLA-A-MICA-CD8(+)/Treg ratio revealed an even poorer survival (P=0.005). In a multivariate Cox analysis, low CD8(+)/Treg ratio (P=0.047), weak HLA-A-MICA expression (P=0.003), and weak HLA-A-MICA expression combined with low CD8(+)/Treg ratio (P=0.002) were all found to be independent unfavorable prognostic predictors in cervical carcinoma (hazard ratios, 2.7, 4.0, and 4.9, respectively). CONCLUSION: Weak HLA-A-MICA expression combined with low CD8(+)/Treg ratio reveals a patient group with the poorest survival in cervical cancer. As a single variable, low CD8(+)/Treg ratio was a significant independent unfavorable prognostic factor.