Melanoma Inhibitor Of Apoptosis Protein Research Articles

The Inhibitor of Apoptosis Protein Livin Confers Resistance to Fas-Mediated Immune Cytotoxicity in Refractory Lymphoma.

Death receptor Fas-mediated apoptosis not only eliminates nonspecific and autoreactive B cells but also plays a major role in antitumor immunity. However, the possible mechanisms underlying impairment of Fas-mediated induction of apoptosis during lymphomagenesis remain unknown. In this study, we employed our developed syngeneic lymphoma model to demonstrate that downregulation of Fas is required for both lymphoma development and lymphoma cell survival to evade immune cytotoxicity. CD40 signal activation significantly restored Fas expression and thereby induced apoptosis after Fas ligand treatment in both mouse and human lymphoma cells. Nevertheless, certain human lymphoma cell lines were found to be resistant to Fas-mediated apoptosis, with Livin (melanoma inhibitor of apoptosis protein; ML-IAP) identified as a driver of such resistance. High expression of Livin and low expression of Fas were associated with poor prognosis in patients with aggressive non-Hodgkin's lymphoma. Livin expression was tightly driven by bromodomain and extraterminal (BET) proteins BRD4 and BRD2, suggesting that Livin expression is epigenetically regulated in refractory lymphoma cells to protect them from Fas-mediated apoptosis. Accordingly, the combination of CD40-mediated Fas restoration with targeting of the BET proteins-Livin axis may serve as a promising immunotherapeutic strategy for refractory B-cell lymphoma. SIGNIFICANCE: These findings yield insights into identifying risk factors in refractory lymphoma and provide a promising therapy for tumors resistant to Fas-mediated antitumor immunity. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/20/4439/F1.large.jpg.

Abstract 3570: Differential expression of the melanoma inhibitor of apoptosis protein (ML-IAP)/Livin in patients with ulcerated and non-ulcerated melanomas

Abstract Background: Cutaneous malignant melanoma is one of the most aggressive forms of skin cancer with an extremely poor prognosis for the patients diagnosed with metastatic disease. Ulceration has been correlated with an increased risk of death within a given thickness range, however, the biologic basis for the development of ulceration is poorly understood. Livin, an inhibitor of apoptosis protein (IAP), is overexpressed in various cancers and possesses both the ability to protect from cell death and to promote it once it is cleaved. It is unknown whether there is a differential cellular expression of livin in ulcerated versus non-ulcerated melanomas. Methods: To explore the role of livin in relation to ulceration, other clinicopathological factors and survival of melanoma patients, we have performed semiquantitative immunohistochemical analysis of livin expression as measured by percentage and intensity (levels) of cells immunoreactive for livin in tumor specimens having both ulcerated and non-ulcerated areas from 50 melanoma lesions. Results: Superficial as well as deep melanoma cells located in non-ulcerated areas of tumor had higher percentage of cytoplasmic immunopositivity for livin when compared with melanocytes in the ulcerated areas of the melanoma (p<0.0001). We also observed nuclear expression of livin protein in this subset of melanoma patients. Compared to the ulcerated areas, the superficially located melanoma cells from the non-ulcerated areas showed significantly higher intensity of livin immunoreactivity in their nuclei (p = 0.048) but not those from the deep non-ulcerated areas (p = 0.32). Ulcerated melanomas with low tumor stage (I/II) had higher percentage of tumor cells with nuclear livin expression than those from higher tumor stage (III/IV) (p = 0.002). Interestingly, we observed that patients with higher intensity of cytosolic expression of livin protein in the ulcerated area of tumor were more likely to have a brisk tumor-infiltrating lymphocytes (TILs) response (p = 0.001). Patients with higher intensity of cytoplasmic livin protein of tumor cells in ulcerated areas had higher risk of death compared to those with lower levels (p = 0.005). On the other hand, patients with higher intensity of cytoplasmic expression of livin in melanoma cells located superficially in the non-ulcerated areas of tumor had better prognosis (p = 0.045). Conclusion: Our data indicate that there is a decrease of nuclear as well as cytoplasmic expression of livin protein in melanoma cells from ulcerated when compared to non-ulcerated areas. Also, cytoplasmic livin expression is an indicator of poor prognosis, but apparently only in patients with ulcerated lesions. Although IAPs regulate caspases, they also regulate signaling pathways that activate NF-κB modulating immunity. The prominent TILs response in livin-positive tumors suggests a possible involvement in tumor immunity in melanoma. Citation Format: Nitin Chakravarti, Dawen Sui, Denái R. Milton, Wen-Jen Hwu, Elizabeth A. Grimm, Victor G. Prieto. Differential expression of the melanoma inhibitor of apoptosis protein (ML-IAP)/Livin in patients with ulcerated and non-ulcerated melanomas. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3570.

Immunity to the melanoma inhibitor of apoptosis protein (ML-IAP; livin) in patients with malignant melanoma

Therapeutic targeting of melanoma antigens frequently focuses on the melanocyte differentiation or cancer-testis families. Antigen-loss variants can often result, as these antigens are not critical for tumor cell survival. Exploration of functionally relevant targets has been limited. The melanoma inhibitor of apoptosis protein (ML-IAP; livin) is overexpressed in melanoma, contributing to disease progression and treatment resistance. Improved understanding of the significance of ML-IAP immune responses in patients has possible therapeutic applications. We found ML-IAP frequently expressed in melanoma metastases by immunohistochemistry. To assess spontaneous immunity to ML-IAP, an overlapping peptide library representing full-length protein was utilized to screen cellular responses in stage I–IV patients and healthy controls by ELISPOT. A broad array of CD4+ and CD8+ cellular responses against ML-IAP was observed with novel class I and class II epitopes identified. Specific HLA-A*0201 epitopes were analyzed further for frequency of reactivity. The generation of specific CD4+ and cytotoxic T cells revealed potent functional capability including cytokine responsiveness to melanoma cell lines and tumor cell killing. In addition, recombinant ML-IAP protein used in an ELISA demonstrated high titer antibody responses in a subset of patients. Several melanoma patients who received CTLA-4 blockade with ipilimumab developed augmented humoral immune responses to ML-IAP as a function of treatment which was associated with beneficial clinical outcomes. High frequency immune responses in melanoma patients, associations with favorable treatment outcomes, and its essential role in melanoma pathogenesis support the development of ML-IAP as a disease marker and therapeutic target.Electronic supplementary materialThe online version of this article (doi:10.1007/s00262-011-1124-1) contains supplementary material, which is available to authorized users.

Melanoma Inhibitor of Apoptosis Protein (ML-IAP) Specific Cytotoxic T Lymphocytes Cross-React with an Epitope from the Auto-Antigen SS56

A large proportion of melanoma patients host a spontaneous T-cell response specifically against ML-IAP-derived peptides. In this study, we describe that some ML-IAP-specific cytotoxic T cells isolated from melanoma patients cross react with an epitope from the auto-antigen SS56. SS56 is a recently described target of autoantibody responses in Sjögren's syndrome (SS) as well as systemic lupus erythematosus (SLE). Here, we describe that SS56 is also an auto-antigen for T cells in SS and SLE. Hence, SS56-specific T cells could readily be detected in circulation and among the infiltrating cells of SLE skin lesions. SS56-specific T cells were able to lyse target cells presenting the peptide epitope on the surface. Notably, SS56-specific CD8 T cells isolated from an SS patient cross reacted with the ML-IAP epitope. This early evidence of a target for auto-reactive CTL in SS and SLE patients; it is to our knowledge previously unreported and underscores the important role of CD8 T cells in autoimmune disorders. Furthermore, the cross-reactivity against the auto-antigen SS56 and the tumor-antigen ML-IAP confirms the link between autoimmunity and anti-cancer cellular immune responses.

Evaluation of Assay Technologies for the Identification of Protein–Peptide Interaction Antagonists

An increasing number of assay detection technologies are routinely used in small molecule drug discovery and lead optimization. These assays range from solid-phase heterogeneous assays such as enzyme-linked immunosorbent assay and dissociation-enhanced lanthanide fluorescent immunoassay (DELFIA, PerkinElmer Life and Analytical Sciences, Boston, MA) to solution phase, bead-based assays such as electrochemiluminescence assay (BioVeris [Gaithersburg, MD] technology) and amplified luminescent proximity homogeneous assay (AlphaScreen, PerkinElmer Life and Analytical Sciences) to completely solution-based homogeneous assays such as time-resolved fluorescence resonance energy transfer and fluorescence polarization. The aim of this study is to compare these assay technologies and assess the advantages and disadvantages of each in the context of our efforts to develop small molecule antagonists to the melanoma inhibitor of apoptosis protein. In this study, seven peptides have been evaluated for their potencies in each assay format. Our results indicate that these assay technologies produce similar relative potencies; however, some methods may be more susceptible to interference than others. Consequently, the choice of the method used frequently depends on a number of factors in addition to assay reproducibility and performance, such as throughput of the assay, cost, compound interference, and ease of use.

Livin/melanoma inhibitor of apoptosis protein as a potential therapeutic target for the treatment of malignancy

Livin, also called melanoma inhibitor of apoptosis protein (IAP) or kidney IAP, is a member of the IAP family of caspase inhibitors that selectively binds the endogenous IAP antagonist SMAC and caspase-3, caspase-7, and caspase-9. As such, Livin inhibits apoptosis, and its overexpression renders malignant cells resistant to chemotherapy. Therefore, inhibitors of Livin could be useful adjuncts to chemotherapy in the treatment of malignancies. This review will discuss Livin as a potential therapeutic target and strategies for its inhibition, including antisense oligonucleotides, small-molecule inhibitors, and immune-mediated approaches.

Antisense-mediated melanoma inhibitor of apoptosis protein downregulation sensitizes G361 melanoma cells to cisplatin

Malignant melanoma is an aggressive form of skin cancer that is highly resistant to conventional therapies. The melanoma inhibitor of apoptosis protein is a potent inhibitor of apoptosis and is overexpressed in melanoma cells, but undetectable in most normal tissues including melanocytes. We designed 20-mer phosphorothioate antisense oligonucleotides complementary to five putatively single-stranded sites on the melanoma inhibitor of apoptosis protein mRNA and investigated their ability to sensitize G361 melanoma cells to cisplatin. Inhibition of melanoma inhibitor of apoptosis protein mRNA and protein expression were measured by real-time polymerase chain reaction and immunoblotting. Cell viability and apoptosis were quantitated by colorimetric viability assays and by annexin V staining, respectively. Oligonucleotide M706 was identified as the most efficient antisense sequence which downregulated melanoma inhibitor of apoptosis protein mRNA and protein levels in G361 cells by 68 and 78%, respectively. The specificity of target downregulation was confirmed using scrambled sequence control oligonucleotides that only marginally decreased melanoma inhibitor of apoptosis protein expression. Whereas downregulation of melanoma inhibitor of apoptosis protein moderately inhibited cell growth by 26%, in combination with cisplatin, this resulted in a supra-additive effect with almost 57% reduction in G361 cell viability compared with cisplatin alone (17%) (P<0.05). Cell death was mainly due to apoptosis as demonstrated by a 3- to 4-fold increase in annexin V-positive cells and typical morphological changes compared with controls. In summary, we describe a new antisense oligonucleotide that efficiently downregulates melanoma inhibitor of apoptosis protein expression and sensitizes melanoma cells to cisplatin.

Melanoma inhibitor of apoptosis protein is expressed differentially in melanoma and melanocytic naevus, but similarly in primary and metastatic melanomas

Background: Malignant melanoma is highly resistant to current treatments. The inhibitor of apoptosis protein (IAP) family member, melanoma IAP (ML-IAP), is overexpressed in some melanoma cell lines, rendering them resistant...

Targeting melanoma inhibitor of apoptosis protein with cancer immunotherapy.

Aberrantly expressed or mutated proteins in cancer cells evoke immune recognition, but host reactions are usually insufficient to prevent disease progression. Vaccination with irradiated tumor cells engineered to secrete granulocyte-macrophage colony stimulating factor (GM-CSF) augments host immunity through improved tumor antigen presentation by recruited dendritic cells and macrophages. By analyzing the immune response of a metastatic melanoma patient who achieved a long-term response to vaccination, we identified melanoma inhibitor of apoptosis protein (ML-IAP) as a target for immune-mediated tumor destruction. Vaccination stimulated a coordinated cellular and humoral reaction to ML-IAP that was associated with extensive tumor necrosis, whereas lethal disease progression was linked with the loss of ML-IAP expression and the absence of intra-tumoral lymphocyte infiltrates. These findings demonstrate that ML-IAP can serve as a tumor rejection antigen, although additional vaccine targets will be required to circumvent immune escape and tumor heterogeneity.

The melanoma inhibitor of apoptosis protein: a target for spontaneous cytotoxic T cell responses.

The identification of tumor antigens which expression is essential for the survival of tumor cells is a new avenue to prevent antigen loss variants emerging due to immunoselection, particularly during immune therapy. The melanoma inhibitor of apoptosis protein, ML-IAP (also named livin) counteracts apoptosis induced by death receptors, hypooxgenic conditions, or chemotherapeutic agents. Thus, elevated expression of ML-IAP renders melanoma cells resistant to apoptotic stimuli and thereby potentially contributes to the oncogenic phenotype. Here, we demonstrate that T cells in a large proportion of melanoma patients infiltrating the tumor or circulating in the peripheral blood specifically recognize ML-IAP-derived peptides. Interestingly, the responses against the peptide epitope ML-IAP280-289 were not restricted to melanoma patients but present among peripheral blood T cells in a few healthy controls. In situ peptide/HLA-A2 multimer staining, however, confirmed the infiltration of ML-IAP-reactive cells into the tumor microenvironment. Moreover, ML-IAP-reactive T cells isolated by magnetic beads coated with peptide/HLA-A2 complexes were cytotoxic against HLA-matched melanoma cells. In conclusion, out data strongly indicate ML-IAP as a suitable target for immunologic intervention.