In human tumors of distinct origin including renal cell carcinoma (RCC), the non-classical human leukocyte antigen G (HLA-G) is frequently expressed, thereby inhibiting the cytotoxic activity of T and natural killer (NK) cells. Recent studies demonstrated a strong post-transcriptional gene regulation of the HLA-G by miR-152, -148A, -148B and -133A. Standard methods were applied to characterize the expression and function of HLA-G, HLA-G-regulatory microRNAs (miRs) and the immune cell infiltration in 453 RCC lesions using a tissue microarray and five RCC cell lines linking these results to clinical parameters. Direct interactions with HLA-G regulatory miRs and the HLA-G 3' untranslated region (UTR) were detected and the affinities of these different miRs to the HLA-G 3'-UTR compared. qPCR analyses and immunohistochemical staining revealed an inverse expression of miR-148A and -133A with the HLA-G protein and. Stable miR overexpression caused a downregulation of HLA-G protein enhancing the NK and LAK cell-mediated cytotoxicity in CD107a activation assays revealing a HLA-G-dependent cytotoxic activity of immune effector cells. A significant higher frequency of CD3/CD8 T cell lymphocytes, but no differences in the activation markers CD69, CD25 or in the presence of CD56, FoxP3 and CD4 immune cells were detected in HLA-G compared to HLA-G RCC lesions. This could be associated with higher WHO grade, but not with a disease-specific survival. These data suggest a miR-mediated control of HLA-G expression in RCC, which is associated with a distinct pattern of immune cell infiltration.

Hormone receptor (HR)+ breast cancer (BC) causes most BC-related deaths, calling for improved therapeutic approaches. Despite expectations, immune checkpoint blockers (ICBs) are poorly active in patients with HR+ BC, in part reflecting the lack of preclinical models that recapitulate disease progression in immunocompetent hosts. We demonstrate that mammary tumors driven by medroxyprogesterone acetate (M) and 7,12-dimethylbenz[a]anthracene (D) recapitulate several key features of human luminal B HR+HER2− BC, including limited immune infiltration and poor sensitivity to ICBs. M/D-driven oncogenesis is accelerated by immune defects, demonstrating that M/D-driven tumors are under immunosurveillance. Safe nutritional measures including nicotinamide (NAM) supplementation efficiently delay M/D-driven oncogenesis by reactivating immunosurveillance. NAM also mediates immunotherapeutic effects against established M/D-driven and transplantable BC, largely reflecting increased type I interferon secretion by malignant cells and direct stimulation of immune effector cells. Our findings identify NAM as a potential strategy for the prevention and treatment of HR+ BC.

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The cyclic (c)AMP responsive element binding protein (CREB) plays a key role in many cellular processes, including differentiation, proliferation, and signal transduction. Furthermore, CREB overexpression was found in tumors of distinct origin and evidence suggests an association with tumorigenicity. To establish a mechanistic link between HER-2/neu-mediated transformation and CREB protein expression and function, in vitro models of HER-2/neu-overexpressing and HER-2/neu-negative/silenced counterparts as well as human mammary carcinoma lesions with defined HER-2/neu status were used. HER-2/neu overexpression resulted in the induction and activation of CREB protein in vitro and in vivo, whereas short hairpin RNA (shRNA)-mediated inhibition of HER-2/neu correlated with downregulated CREB activity. CREB activation in HER-2/neu-transformed cells enhanced distinct signal transduction pathways, whereas their inhibition negatively interfered with CREB expression and/or activation. CREB downregulation in HER-2/neu-transformed cells by shRNA and by the inhibitors KG-501 and lapatinib caused morphologic changes, reduced cell proliferation with G 0 -G 1 cell-cycle arrest, which was rescued by CREB expression. This was accompanied by reduced cell migration, wound healing, an increased fibronectin adherence, invasion, and matrix metalloproteinase expression. In vivo shCREB-HER-2/neu þ cells, but not control cells, exerted a significantly decreased tumorgenicity that was associated with decreased proliferative capacity, enhanced apoptosis, and increased frequency of T lymphocytes in peripheral blood mononuclear cells. Thus, CREB plays an important role in the HER-2/neu-mediated transformation by altering in vitro and in vivo growth characteristics.

The clinical usage of dendritic cells (DC) for tumor immunotherapy still requires improvements. In this study, three alternative maturation mixtures were compared with the cytokine-based gold standard, and the overall interaction of the resulting DC with effector cells from the innate as well as the adaptive immunity was evaluated in healthy donors. Stimulation with the TLR-4 ligand monophosphoryl lipid A together with IFN-γ (alt-2 DC) resulted in DC with the highest levels of costimulatory molecule expression and IL-12p70/IL-10 ratio. Whereas all alternative DC were able to induce NK and γδ T cells to acquire cytotoxic properties and secrete type 1 and proinflammatory cytokines, after both short (20-h)- and long (5–8 d)-time coculture, secretion of IFN-γ by the innate populations was induced in response to alt-2 and alt-1 DC (TNF-α, IFN-α, IFN-γ, IL-1β, poly IC), but not to alt-3 DC (TNF-α, IFN-γ, IL-1β, CL097). Regarding CD8+ T cell–mediated Ag-specific immune responses, a heterogeneous pattern of responses was obtained among the healthy donors, suggesting rather a competition than a synergy among the different effector cells. Our data promote further evaluation of alt-2 fast DC for translatability into clinical immunotherapy trials, while also fostering the need to identify biomarkers for immune cell responsiveness and tumor susceptibility to be able to select for each patient the best possible DC-based therapy.

Tumor immunotherapy has exploited the ability of heat shock proteins to chaperone precursors of antigenic peptides to antigen-presenting cells and to activate efficiently an immune response against tumor-associated antigens. The most common strategy is based on the purification of heat shock protein-peptide complexes from tumor cell lines or from tumor surgical samples for in vivo administration. In this article, we have modified the murine-inducible hsp70 into a secreted protein and engineered tumor cells to secrete constitutively their antigenic repertoire associated with the hsp70 protein. In vitro studies showed that the relocalization of hsp70 from the cytoplasm to the secretory pathway did not modify the ability of hsp70 to interact with peptides derived either from natural tumor-associated antigens or model antigens, and that antigen-presenting cells specifically took up the secreted hsp70 and presented the chaperoned epitopes to T cells. In vivo studies showed that tumors secreting hsp70 displayed increased immunogenicity, with induction of a strong and specific CTL response. Mice injected with hsp70-secreting tumors showed increased survival and impaired tumor take compared with mice bearing parental tumors. More than 70% of mice rejected tumor cells secreting hsp70 through mechanisms that involve T lymphocytes and natural killer cells, with the induction of a memory response in the case of T lymphocytes. Moreover, hsp70 secretion increased the immunogenic potential of tumor cell vaccines.

The non-classical human leukocyte antigen G (HLA-G) is expressed at a high frequency in renal cell carcinoma (RCC) and is associated with a higher tumor grade and a poor clinical outcome. This might be caused by the HLA-G-mediated inhibition of the cytotoxicity of T and NK cells. Therefore a selective targeting of HLA-G might represent a powerful strategy to enhance the immunogenicity of RCC lesions. Recent studies identified a number of HLA-G-regulating microRNAs (miRs) and demonstrated an inverse expression of some of these miRs with HLA-G in RCC in vitro and in vivo. However, it was postulated that further miRs might exist contributing to the tightly controlled selective HLA-G expression.By application of a miR enrichment assay (miTRAP) in combination with in silico profiling two novel HLA-G-regulatory miRs, miR-548q and miR-628-5p, were identified. Direct interactions of both miRs with the 3′ untranslated region of HLA-G were confirmed with luciferase reporter gene assays. In addition, qPCR analyses and immunohistochemical staining revealed an inverse, expression of miR-628-5p, but not of miR-548q to the HLA-G protein in primary RCC lesions and cell lines. Stable overexpression of miR-548q and miR-628-5p caused a downregulation of HLA-G mRNA and protein. This leads in case of miR-548q to an enhanced NK cell-mediated HLA-G-dependent cytotoxicity, which could be reverted by ILT2 blockade suggesting a control of the immune effector cell activity at least by this miR. The identification of two novel HLA-G-regulatory miRs extends the number of HLA-G-relevant miRs tuning the HLA-G expression and might serve as future therapeutic targets.

BackgroundIn patients with microsatellite stable (MSS) metastatic colorectal cancer (mCRC), immune checkpoint blockade is ineffective, and combinatorial approaches enhancing immunogenicity need exploration.MethodsWe treated 43 patients with predominantly microsatellite stable RAS/BRAF wild-type mCRC on a phase II trial combining chemotherapy with the epidermal growth factor receptor antibody cetuximab and the programmed cell death ligand 1 (PD-L1) antibody avelumab. We performed next-generation gene panel sequencing for mutational typing of tumors and liquid biopsy monitoring as well as digital droplet PCR to confirm individual mutations. Translational analyses included tissue immunohistochemistry, multispectral imaging and repertoire sequencing of tumor-infiltrating T cells. Detected PD-L1 mutations were mechanistically validated in CRISPR/Cas9-generated cell models using qRT-PCR, immunoblotting, flow cytometry, complement-dependent cytotoxicity assay, antibody-dependent cytotoxicity by natural killer cell degranulation assay and LDH release assay as well as live cell imaging of T cell mediated tumor cell killing.ResultsCirculating tumor DNA showed rapid clearance in the majority of patients mirroring a high rate of early tumor shrinkage. In 3 of 13 patients expressing the high-affinity Fcγ receptor 3a (FcγR3a), tumor subclones with PD-L1 mutations were selected that led to loss of tumor PD-L1 by nonsense-mediated RNA decay in PD-L1 K162fs and protein degradation in PD-L1 L88S. As a consequence, avelumab binding and antibody-dependent cytotoxicity were impaired, while T cell killing of these variant clones was increased. Interestingly, PD-L1 mutant subclones showed slow selection dynamics reversing on avelumab withdrawal and patients with such subclones had above-average treatment benefit. This suggested that the PD-L1 mutations mediated resistance to direct antitumor effects of avelumab, while at the same time loss of PD-L1 reduced biological fitness by enhanced T cell killing limiting subclonal expansion.ConclusionThe addition of avelumab to standard treatment appeared feasible and safe. PD-L1 mutations mediate subclonal immune escape to avelumab in some patients with mCRC expressing high-affinity FcγR3a, which may be a subset experiencing most selective pressure. Future trials evaluating the addition of avelumab to standard treatment in MSS mCRC are warranted especially in this patient subpopulation.Trial registration numberNCT03174405.