The bidirectional crosstalk between metastatic uveal melanoma cells and hepatic stellate cells engenders an inflammatory microenvironment.

Uveal melanoma is the most common primary ocular neoplasm in adults. It is peculiar for its hematogenous dissemination and its high propensity to spread to the liver. Current treatments rarely prolong patient survival. We hypothesized that metastatic uveal melanoma cells modulate the function of surrounding hepatic stellate cells to facilitate their own growth and survival. This study was conducted to investigate the role of the hepatic microenvironment on uveal melanoma aggressiveness. We demonstrated that the paracrine signaling of surrounding hepatic stellate cells have more transcriptional impact on metastatic uveal melanoma cells. Upregulated transcripts were linked to inflammation and included several interleukins. The uveal melanoma-stellate cell crosstalk induced as well the expression of transmembrane integrins. In addition, the interleukin-6 receptor inhibitor Tocilizumab did not reduce the growth of uveal melanoma cells. Our results provide evidence that inflammatory mediators are key players in the homing of uveal melanoma cells to the liver. The bidirectional crosstalk between uveal melanoma cells and hepatic stellate cells involved pro-fibrogenic interleukins. The inflammatory characteristics of the metastatic microenvironment might offer relevant therapeutic opportunities in uveal melanoma.

Dramatic efficacy improvement of a DC-based vaccine against AML by CD25 T cell depletion allowing the induction of a long-lasting T cell response.

Dendritic cell (DC)-based vaccination is a promising approach to enhance anti-tumor immunity that could be considered for acute myeloid leukemia (AML) patients with high-risk of relapse. Our purpose was to study the efficiency and to optimize the immunogenicity of a DC-based vaccine in a preclinical AML murine model. In this report, C57BL6 mice were vaccinated with DC pulsed with peptides eluted (EP) from the syngeneic C1498 myelomonocytic leukemic cell line in a prophylactic setting. In this model, a natural antileukemic immunity mediated by NK cells was observed in the control unloaded DC-vaccinated group. On the other hand, we showed that the cytotoxic antileukemic immune response induced by vaccination with eluted peptides pulsed-DC (DC/EP), in vitro and in vivo, was mainly mediated by CD4(+) T cells. Treatment with anti-CD25 antibody to deplete CD4(+) CD25(+) regulatory T cells before DC-vaccination dramatically improved the antileukemic immune response induced by immunization, and allowed the development of long-lasting immune responses that were tumor protective after a re-challenge with leukemic cells. Our results suggest that this approach could be successful against weakly immunogenic tumors such as AML, and could be translated in human.

17-AAG and 17-DMAG-induced inhibition of cell proliferation through B-Raf downregulation in WT B-Raf-expressing uveal melanoma cell lines.

PURPOSE: The HSP90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG) has been shown to have promising results in antitumor activity through the degradation of the activated V600E mutant of B-Raf (V600E B-Raf) in cutaneous melanoma cell lines. It has different effects, however, on the wild-type form of B-Raf (WT B-Raf), according to the WT B-Raf activation levels in the tumor cells. Uveal melanoma cells express WT B-Raf and only rarely express V600E B-Raf. This study was conducted to investigate the effects of HSP90 inhibition on uveal melanoma cell lines. METHODS: Human uveal melanoma cell lines were treated with the HSP90 inhibitors 17-AAG and 17-dimethylaminoethylamino-17-demethoxy-geldanamycin (17-DMAG). Cell proliferation was assessed by MTT staining, and apoptosis was quantified by flow cytometry. Analysis of the expression of HSP90 and activation of the MEK/ERK downstream signaling of B-Raf was performed by Western blot. Effects of the downregulation of the HSP90 cochaperone, cdc37, on cell proliferation and activation of MEK/ERK was investigated by siRNA strategy. RESULTS: The inhibition of HSP90 downregulated B-Raf, decreased cell proliferation, and reduced activation of MEK/ERK in uveal melanoma cell lines expressing WT B-Raf. HSP90 inhibition also reduced the expression of Akt, but the inhibition of Akt had no effect on cell proliferation, ruling out a role of Akt in the 17-AAG-induced inhibition of cell proliferation. The downregulation of cdc37 did not affect MEK/ERK signaling and cell proliferation, demonstrating that the cochaperone was not required for HSP90-controlled stability of B-Raf. c-Kit was also downregulated after HSP90 inhibition. The combination of 17-DMAG with imatinib mesylate, the inhibitor of c-kit, had synergistic inhibitory effects on cell proliferation in WT B-Raf uveal melanoma cell lines. CONCLUSIONS: These results suggest that targeting HSP90 in tandem with c-Kit inhibition may be a promising therapeutic approach to uveal melanoma.

The PI3K/Akt and mTOR/P70S6K signaling pathways in human uveal melanoma cells: interaction with B-Raf/ERK.

PURPOSE: Activated B-Raf alone cannot induce melanoma but must cooperate with other signaling pathways. The phosphatidylinositol 3-kinase (PI3K)/Akt and mammalian target of rapamycin (mTOR)/p70S6K pathways are critical for tumorigenesis. The authors investigated the role of these pathways in uveal melanoma cells. METHODS: The effects of PI3K and mTOR activation and inhibition on the proliferation of human uveal melanoma cell lines expressing either activated (WT)B-Raf or (V600E)B-Raf were investigated. Interactions among PI3K, mTOR, and B-Raf/ERK were studied. RESULTS: Inhibition of PI3K deactivated P70S6 kinase, reduced cell proliferation by 71% to 84%, and increased apoptosis by a factor of 5.0 to 8.4 without reducing ERK1/2 activation, indicating that ERK plays no role in mediating PI3K in these processes. In contrast, rapamycin-induced inhibition of mTOR did not significantly affect cell proliferation because it simultaneously stimulated PI3K/Akt activation and cyclin D1 expression. Regardless of B-Raf mutation status, cotreatment with the PI3K inhibitor effectively sensitized all melanoma cell lines to the B-Raf or ERK1/2 inhibition-induced reduction of cell proliferation. B-Raf/ERK and PI3K signaling, but not mTOR signaling, converged to control cyclin D1 expression. Moreover, p70S6K required the activation of ERK1/2. These data demonstrate that PI3K/Akt and mTOR/P70S6K interact with B-Raf/ERK. CONCLUSIONS: Activated PI3K/Akt attenuates the inhibitory effects of rapamycin on cell proliferation and thus serves as a negative feedback mechanism. This finding suggests that rapamycin is unlikely to inhibit uveal melanoma growth. In contrast, targeting PI3K while inhibiting B-Raf/ERK may be a promising approach to reduce the proliferation of uveal melanoma cells.

Activation of the FGF2/FGFR1 autocrine loop for cell proliferation and survival in uveal melanoma cells.

PURPOSE: Constitutive activation of ERK1/2 controls proliferation of uveal melanoma cells. Because an autocrine fibroblast growth factor (FGF) activation loop controls ERK1/2 activation in many cancers, this study was conducted to examine the role of the FGF/FGF receptor autocrine loop in the ERK1/2-dependent proliferation and survival of uveal melanoma cells. METHODS: Primary tumors and cell lines (OCM-1, MKT-BR, SP6.5, Mel270 and 92.1) were used to define the role of the FGF/FGFR system in human uveal melanoma. Cell proliferation was assessed by MTT-staining, and apoptosis was quantified by flow cytometry. Specific pharmacologic inhibitors of ERK1/2 and FGFR1, an anti-FGF2 neutralizing antibody and an antisense oligonucleotide directed against FGF2 were used to analyze signaling in the FGF/FGFR autocrine loop. RESULTS: FGF1, FGF2, and their FGFR1 receptor were strongly expressed in the primary uveal melanomas. All five uveal melanoma cell lines expressed and secreted FGF2. They also expressed FGFR1. Cell proliferation was strongly reduced by the antisense oligonucleotide-mediated depletion of endogenous FGF2, immunoneutralization of secreted FGF2, and pharmacologic inhibition of FGFR1. The FGF2/FGFR1-mediated signaling pathway was identified by showing that inhibition of either FGF2 or FGFR1 reduced ERK1/2 activation, cell proliferation, and survival. CONCLUSIONS: The FGF/FGFR/ERK signaling pathway may be a target for therapeutic strategies against uveal melanoma.