The majority of current anticancer therapies induce tumor cell death through the induction of apoptosis. Alterations in the apoptotic pathways may determine tumor resistance to these therapies. ...Activation of the proteolytic cascade involving caspase family members is a critical component of the execution of cell death in apoptotic cells. However, recent studies suggest that cell death can proceed in the absence of caspases. In this review we describe the role of caspase-dependent and -independent pathways as targets for anticancer treatment. A better understanding of diverse modes of tumor cell death will help to avoid ineffective treatment and provide a molecular basis for the new strategies targeting caspase-independent death pathways in apoptosis-resistant forms of cancer.
Tumors represent an altered self cell type that can be recognized by both the host humoral (B cells, antibodies) and cellular (T cells) adaptive immune systems. Because most known tumor-associated ...antigens (TAA) recognized by T cells represent overexpressed or aberrantly expressed proteins, which are not mutated and to which tolerance has been developed, the anti-TAA T-cell repertoire available to the cancer patient is of moderate-to-low avidity. Specific vaccinations typically amplify the absolute number of such T cells, but may have little consequence on improving their functional avidity, which may fall below a critical threshold required for effective recognition of tumor cells in situ. This review will discuss methods to improve low-avidity T-cell recognition of cancer cells by manipulating the tumor cells themselves to conditionally express higher levels of TAA-derived peptide epitopes presented in major histocompatibility (MHC) complexes. This may facilitate the design and performance of novel combinational therapies for the effective treatment of a broad range of cancer types.
IL-17 is a pro-inflammatory cytokine implicated in the pathogenesis of autoimmune diseases including psoriasis. ACT1 is an essential adaptor molecule in the IL-17 signaling pathway. A missense single ...nucleotide polymorphism (
rs33980500
; SNP-
D10N
) that resulted in the substitution of an asparagine for an aspartic acid at position 10 of ACT1 (ACT1-D10N) is associated with psoriasis susceptibility. Due to alternative splicing in humans, SNP-
D10N
encodes two mutated ACT1 proteins, ACT1-D10N and ACT1-D19N. Though both ACT1 isoforms are Hsp90 ‘client’ proteins, the nine additional amino acids in ACT1-D19N provide an additional Hsp90 binding site that is absent in ACT1-D10N. Therefore, while ACT1-D10N is a dead protein that is unable to transduce IL-17 signals for gene expression, ACT1-D19N is fully responsive to IL-17. Intriguingly, the two ACT1 isoforms are differentially expressed in ACT1
D10N/D10N
fibroblasts and T cells. Fibroblasts express both isoforms equally, enabling ACT1-D19N to compensate for the loss of ACT1-D10N function. ACT1
D10N/D10N
T cells, however, express predominantly ACT1-D10N. Lacking this compensatory mechanism, ACT1
D10N/D10N
T cells behave like ACT1-deficient T cells, exhibiting a dysregulated and hyperactive Th17 phenotype with overproduction of IL-22 and IL-17. The hyperactive Th17 response combined with fully responsive fibroblasts likely synergized to contribute to psoriasis susceptibility in SNP-
D10N
patients.
Renal cell carcinoma (RCC) is known to be a model of an immune-influenced malignancy. The immunobiology of RCC has three main immune cell types known to contribute to immunosuppression: T regulatory ...(Treg) cells, Type 2 T helper (Th2) cells, and myeloid derived suppressor cells. Sunitinib has rapidly revolutionized RCC treatment and is now a first-line standard of care for advanced RCC. Preliminary evidence reviewed here reveals that, in addition to antiangiogenic effects, sunitinib may have a direct or secondary effect on reversing the immunosuppressive environment by decreasing Treg cells and reversing the Th2 bias. Hypotheses for these observed effects and others are postulated based upon the mechanism of action. Current research is underway to further delineate the effect sunitinib has on the immune system and its mechanisms. Future therapeutics in RCC may include combination therapies that function collaboratively with sunitinib to harness an antitumor immune effect.PUBLICATION ABSTRACT
The antitumor effect of T cells is executed either through CD95 or Perforin (PFN)/Granzyme B (GrB) pathways. Induction of apoptosis by either mode requires activation of caspase family members. ...However, recent studies have suggested that cell death can proceed in the absence of caspase induction and apoptotic events. We investigated the contribution of CD95 and PFN/GrB-mediated cytotoxicity to apoptotic and necrotic mechanisms of cell death in human renal cell carcinoma. Although freshly isolated and cultured tumors expressed CD95 on their surface, they were resistant to CD95-mediated apoptosis. CD95 resistance coincided with decreased levels of FADD protein and diminished caspase-3-like activity. In contrast, we demonstrated that tumor cell death mediated by PFN/GrB can be achieved in the absence of functional caspase activity and is accompanied by a dramatic accumulation of nonapoptotic necrotic cells.
Previously we showed that IL2 expanded tumor-infiltrating lymphocytes (TILs) from renal cell carcinoma mediated non-major histocompatibility complex-restricted cytotoxicity. Phenotypic analysis ...showed that cultured TILs were composed mostly of T-lymphocytes with varying numbers of CD4+, CD8+, and CD56+ (Leu19+) populations. Here we compared the cytolytic activity of the two predominant TIL subsets, CD3+CD4+ and CD3+CD8+, to that of the CD56+ populations. Using magnetic beads coated with antibodies to either CD4 or CD8, CD3+CD4+, and CD3+CD8+ TILs were isolated in a highly enriched form (greater than 92%) and could be expanded for over 40 days in vitro with 1000 units/ml IL2. In a 4-h 51Cr release assay the CD4+ and CD8+ TILs showed minimal lytic activity, whereas unseparated cells exhibited significant levels of non-major histocompatibility complex-restricted cytotoxicity. The lytic activity seen in the 4-h assay with unseparated TILs appeared to be related to the presence of CD56+ populations. With one exception none of the purified CD4+ or CD8+ TILs expressed any significant levels of CD56, while the unseparated TILs contained varying numbers of CD3+CD56+ and CD3-CD56+ populations. Cell-sorting experiments verified that the CD56+ populations were responsible for most of the lytic activity in 4 h even though CD3+CD56- cells represented the predominant cell type. Although CD3+CD56- TILs were minimally lytic in 4 h, we show here that both CD3+CD4+ and CD3+CD8+ subsets displayed substantial cytotoxicity in long-term assays. In the 18-h 51Cr release assay 5 of 6 CD4+ and 2 of 3 CD8+ TILs were lytic for the autologous tumor. In two cases, restimulation with the autologous tumor induced augmented cytolytic activity of TIL subsets and in one case induced lytic activity in 4 h. The cytotoxic activity of TIL subsets was further examined using a 72-h assay in which TILs were cocultured with a confluent layer of tumor cells. The degree of cytotoxicity was quantitated by measuring the amount of crystal violet dye that was incorporated by tumor cells which remained after the incubation period. CD4+ and CD8+ TILs typically caused greater than a 50% reduction of tumor cells in 3 days and the level of reduction was increased when IL2 was added to the cultures. All the CD4+ and CD8+ subset preparations were cytotoxic in the 3-day assay even though some were not lytic for certain targets in the 18-h 51Cr release assay.
Myeloid derived suppressor cells (MDSC) are detected at elevated levels in the peripheral blood mononuclear cells (PBMC) of human renal cell carcinoma (RCC) patients and have been shown to mediate ...tumor growth by promoting angiogenesis and immune suppression (Zea et al., 2005, Ko et al., 2009). Granulocytic-MDSCs (G-MDSCs), the dominant population in RCC patients, have been shown to suppress T-cell function in RCC patients (Rodriguez et al., 2009; Schmeilau and Finn, 2001; Zea et al., 2005). However, less is known regarding the role of neutrophils in promoting tumor growth in RCC patients and their relationship to G-MDSC. In this study we compared the suppressive and angiogenic profile of neutrophils from RCC patients to those of normal donors and the impact that RCC conditioned media has in altering neutrophils normal function. We showed that IFNγ production of T-cells stimulated with anti-CD3/antiCD28 antibodies (n=4) was suppressed by neutrophils pretreated with SK-RC-26b tumor supernatant (TCM) when compared to neutrophils not exposed to TCM. Further experiments showed that neutrophils from RCC patients had increased expression compared to normal healthy donor neutrophils of genes Vegfa (15.28 fold increase), Vegfb (10.84 fold increase), Tgfb1 (3.31 fold increase), IL10 (23.45 fold increase), IDO1 (4.60 fold increase), Nox1 (9.33 fold increase), and Prokr2 (4.14 fold increase) utilizing custom pro-angiogenic and immunosuppressive RT-PCR arrays (n=4). Furthermore, human angiogenesis Proteome Profile Arrays (n=2) were performed comparing RCC patient and normal healthy donor neutrophils and exhibited an increased level of Activin A (94.5% increase), Angiogenin (70% increase), Angiostatin/ plasminogen (56% increase), IGFBP-1 (188% increase), IGFBP-2 (263% increase),TGF-B1 (157.5% increase), Pentraxin 3 (140% increase), PD-ECGF (184.5% increase), Serpin E1 (196% increase), and Serpin F1 (114.5% increase) in RCC patient neutrophils. Normal neutrophils cultured with ACHN tumor supernatant for 18 hours (n=2) had up-regulation of proteins CXCL16 (111% increase), FDF-7 (82% increase), Serpin E1 (470.5% increase), and uPA (198.5% increase) when compared to normal healthy donor’s neutrophils cultured 18 hours in media. In summary, we observed up-regulation of several pro-angiogenic/ immunosuppressive genes in RCC patient neutrophils, suggesting RCC patient neutrophils may promote tumor escape. In addition, the normal healthy donor neutrophils cultured with ACHN tumor supernatant produces several angiogenic proteins suggesting the tumor microenvironment could be providing factors to mediate these angiogenic functions in RCC patient’s neutrophils.
Activation of the transcription factor nuclear factor-κB (NFκB) is impaired in T cells from patients with renal cell carcinomas (RCCs). In circulating T cells from a subset of patients with RCCs, the ...suppression of NFκB binding activity is downstream from the stimulus-induced degradation of the cytoplasmic factor IκBα. Tumor-derived soluble products from cultured RCC explants inhibit NFκB activity in T cells from healthy volunteers, despite a normal level of stimulus-induced IκBα degradation in these cells. The inhibitory agent has several features characteristic of a ganglioside, including sensitivity to neuraminidase but not protease treatment; hydrophobicity; and molecular weight less than 3 kDa. Indeed, we detected gangliosides in supernatants from RCC explants and not from adjacent normal kidney tissue. Gangliosides prepared from RCC supernatants, as well as the purified bovine gangliosides G
m1
and G
d1a
, suppressed NFκB binding activity in T cells and reduced expression of the cytokines IL-2 and IFN-γ. Taken together, our findings suggest that tumor-derived gangliosides may blunt antitumor immune responses in patients with RCCs.
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