Transcription factor Sp1 is upregulated by PKCι to drive the expression of YAP1 during pancreatic carcinogenesis.

Recently, we identified that the atypical protein kinase C isoform ι (PKCι) enhances the expression of Yes-associated protein 1 (YAP1) to promote the tumorigenesis of pancreatic adenocarcinoma harboring mutant KRAS (mu-KRAS). To advance our understanding about underlying mechanisms, we analyze the transcription of YAP1 in pancreatic cancer cells and reveal that transcription factor specificity protein 1 (Sp1) is upregulated by PKCι and subsequently binds to multiple sites in YAP1 promoter to drive the transactivation of YAP1 in pancreatic cancer cells carrying mu-KRAS. The bioinformatics analysis further substantiates that the expression of PKCι, Sp1 and YAP1 is correlated and associated with the stages and prognosis of pancreatic tumors. Moreover, our apoptotic detection data demonstrate that combination of PKCι and Sp1 inhibitors at subtoxic doses displays synergistic effects on inducing apoptosis and reversing the immunosuppression of pancreatic cancer cells, establishing the combination of PKCι and Sp1 inhibitors as a promising novel therapeutic approach, or an adjuvant strategy to potentiate the antitumor effects of other immunotherapeutic agents in pancreatic cancer treatment.

High RIG-I expression in ovarian cancer associates with an immune-escape signature and poor clinical outcome.

Ovarian cancer (OC) is the most lethal gynecological malignancy, with platinum-based chemotherapy remaining the mainstay for adjuvant treatment after surgery. The lack of indication for immunotherapy may at least in part result from the lack of suitable biomarkers allowing stratification of potentially responding patients. In this monocentric study of 141 cases with OC, we used real-time quantitative PCR to assess the expression of retinoic acid-inducible gene-I (RIG-I) in primary tumor and healthy ovarian control tissues. RIG-I expression was correlated to various clinicopathological characteristics as well as to a set of molecular and immunological markers. The prognostic significance of RIG-I expression was queried in univariate and multivariate analyses and validated in an independent cohort. RIG-I was overexpressed in the cancerous ovary and correlated with a higher tumor grade. The more aggressive Type-II cancers and cancers with inactivating p53 mutations exhibited higher RIG-I expression. RIG-I levels were also elevated in cancers that recurred after remission or were platinum-refractory. Survival analyses disclosed RIG-I as an independent marker of poor outcome in OC. Continuative analyses revealed the molecular and immunological correlates of RIG-I expression in the tumor microenvironment, including interferon production and a distinct immune-regulatory signature involving checkpoint molecules (PD-L1/PD-1), the RNA-editing enzyme ADAR1 and the regulatory T cell-specific transcription factor FoxP3. We conclude that high RIG-I expression associates with poor outcome in OC, which is explainable by local immunosuppression in the tumor bed. RIG-I expression may inform checkpoint blockade and/or RIG-I agonistic targeting in a subset of high-risk OC patients.

Low concentrations of the soy phytoestrogen genistein induce proteinase inhibitor 9 and block killing of breast cancer cells by immune cells.

The risks and benefits of diets and supplements containing the estrogenic soy isoflavone genistein are not well established. We report that 10 nm genistein potently induces the granzyme B inhibitor, proteinase inhibitor 9 (PI-9) in MCF-7 human breast cancer cells. By inducing PI-9, genistein inhibits the ability of human natural killer (NK) cells to lyse the target breast cancer cells. In ERalphaHA cells, stably transfected MCF-7 cells, which contain elevated levels of estrogen receptor-alpha (ERalpha), 100 pm genistein or 17beta-estradiol potently induce PI-9 and prevent NK cells from killing the target breast cancer cells. The concentrations of genistein that fully induce PI-9 in MCF-7 cells, and in ERalphaHA cells, are far lower than those previously reported to elicit estrogenic responses through ERalpha. Because 4-hydroxytamoxifen, raloxifene, and ICI 182,780/Faslodex all block genistein induction of PI-9 and elevated levels of ERalpha enhance induction of PI-9, genistein acts via ERalpha to induce PI-9. Increasing levels of ERalpha in breast cancer cells results in a progressive increase in induction of PI-9 by genistein and in the cell's ability to evade killing by NK cells. Moderate levels of dietary genistein and soy flour effectively induce PI-9 in human breast cancers grown in ovariectomized athymic mice. A significant population consumes levels of genistein in soy products that may be high enough to induce PI-9, perhaps potentiating the survival of some preexisting breast cancers by enabling them to evade immunosurveillance.

OX40 agonist therapy enhances CD8 infiltration and decreases immune suppression in the tumor.

Acquisition of full T-cell effector function and memory differentiation requires appropriate costimulatory signals, including ligation of the costimulatory molecule OX40 (TNFRSF4, CD134). Tumors often grow despite the presence of tumor-specific T cells and establish an environment with weak costimulation and immune suppression. Administration of OX40 agonists has been shown to significantly increase the survival of tumor-bearing mice and was dependent on the presence of both CD4 and CD8 T cells during tumor-specific priming. To understand how OX40 agonists work in mice with established tumors, we developed a model to study changes in immune cell populations within the tumor environment. We show here that systemic administration of OX40 agonist antibodies increased the proportion of CD8 T cells at the tumor site in three different tumor models. The function of the CD8 T cells at the tumor site was also increased by administration of OX40 agonist antibody, and we observed an increase in the proportion of antigen-specific CD8 T cells within the tumor. Despite decreases in the proportion of T regulatory cells at the tumor site, T regulatory cell function in the spleen was unaffected by OX40 agonist antibody therapy. Interestingly, administration of OX40 agonist antibody caused significant changes in the tumor stroma, including decreased macrophages, myeloid-derived suppressor cells, and decreased expression of transforming growth factor-beta. Thus, therapies targeting OX40 dramatically changed the tumor environment by enhancing the infiltration and function of CD8 T cells combined with diminished suppressive influences within the tumor.

[Tumor escape mechanism involving Fas and Fas-L molecules in human colorectal tumors].

OBJECTIVES: The interaction between Fas and its ligand (Fas-L) leads to Fas-positive cell apoptosis. Our objective was to study a new mechanism of tumor escape involving these molecules, the so-called "counterattack". METHODS: We used flow cytometry to analyze Fas expression and apoptosis sensitivity in different human colorectal tumor cell lines. The presence of Fas-L mRNA was analyzed by RT-PCR. We studied apoptosis rate in peripheral blood lymphocytes and lymph node lymphocytes from patients with colorectal cancer by flow cytometric cell cycle analysis after in vitro culture with or without tumor cells. RESULTS: We found differences in Fas expression and sensitivity to Fas-induced apoptosis between different colorectal tumor cell lines. Interferon-gamma was also found to affect Fas expression and apoptosis sensitivity induced by an anti-Fas antibody. Actinomycin-D decreased Fas expression and apoptosis sensitivity in certain cell lines. Our data confirmed the tumor cell "counterattack" hypothesis by showing their capacity to induce apoptosis in lymphocytes from patients with colorectal cancer. CONCLUSION: Fas expression and apoptosis sensitivity in colorectal tumor cell lines can be modulated by actinomycin-D or interferon-gamma. These data may suggest new therapeutic options based on increased Fas expression in tumor cells induced by interferon-gamma, or on apoptosis induction in tumor cells with a local intratumoral treatment with actinomycin-D.