Immunoregulatory protein B7-H3 regulates cancer stem cell enrichment and drug resistance through MVP-mediated MEK activation.

B7-H3 is a tumor-promoting glycoprotein that is expressed at low levels in most normal tissues, but is overexpressed in various human cancers which is associated with disease progression and poor patient outcome. Although numerous publications have reported the correlation between B7-H3 and cancer progression in many types of cancers, mechanistic studies on how B7-H3 regulates cancer malignancy are rare, and the mechanisms underlying the role of B7-H3 in drug resistance are almost unknown. Here we report a novel finding that upregulation of B7-H3 increases the breast cancer stem cell population and promotes cancer development. Depletion of B7-H3 in breast cancer significantly inhibits the cancer stem cells. By immunoprecipitation and mass spectrometry, we found that B7-H3 is associated with the major vault protein (MVP) and activates MEK through MVP-enhancing B-RAF and MEK interaction. B7-H3 expression increases stem cell population by binding to MVP which regulates the activation of the MAPK kinase pathway. Depletion of MVP blocks the activation of MEK induced by B7-H3 and dramatically inhibits B7-H3 induced stem cells. This study reports novel functions of B7-H3 in regulating breast cancer stem cell enrichment. The novel mechanism for B7-H3-induced stem cell propagation by regulating MVP/MEK signaling axis independent of the classic Ras pathway may have important implications in the development of strategies for overcoming cancer cell resistance to chemotherapy.

Diverse Roles of Mitochondria in Immune Responses: Novel Insights Into Immuno-Metabolism.

Lack of immune system cells or impairment in differentiation of immune cells is the basis for many chronic diseases. Metabolic changes could be the root cause for this immune cell impairment. These changes could be a result of altered transcription, cytokine production from surrounding cells, and changes in metabolic pathways. Immunity and mitochondria are interlinked with each other. An important feature of mitochondria is it can regulate activation, differentiation, and survival of immune cells. In addition, it can also release signals such as mitochondrial DNA (mtDNA) and mitochondrial ROS (mtROS) to regulate transcription of immune cells. From current literature, we found that mitochondria can regulate immunity in different ways. First, alterations in metabolic pathways (TCA cycle, oxidative phosphorylation, and FAO) and mitochondria induced transcriptional changes can lead to entirely different outcomes in immune cells. For example, M1 macrophages exhibit a broken TCA cycle and have a pro-inflammatory role. By contrast, M2 macrophages undergo ß-oxidation to produce anti-inflammatory responses. In addition, amino acid metabolism, especially arginine, glutamine, serine, glycine, and tryptophan, is critical for T cell differentiation and macrophage polarization. Second, mitochondria can activate the inflammatory response. For instance, mitochondrial antiviral signaling and NLRP3 can be activated by mitochondria. Third, mitochondrial mass and mobility can be influenced by fission and fusion. Fission and fusion can influence immune functions. Finally, mitochondria are placed near the endoplasmic reticulum (ER) in immune cells. Therefore, mitochondria and ER junction signaling can also influence immune cell metabolism. Mitochondrial machinery such as metabolic pathways, amino acid metabolism, antioxidant systems, mitochondrial dynamics, mtDNA, mitophagy, and mtROS are crucial for immune functions. Here, we have demonstrated how mitochondria coordinate to alter immune responses and how changes in mitochondrial machinery contribute to alterations in immune responses. A better understanding of the molecular components of mitochondria is necessary. This can help in the development of safe and effective immune therapy or prevention of chronic diseases. In this review, we have presented an updated prospective of the mitochondrial machinery that drives various immune responses.

Interplay between Immune Checkpoint Proteins and Cellular Metabolism.

With the recent successes in immuno-oncology, renewed interest in the role of immune checkpoint modulators, such as the B7 family proteins, has escalated. The immune checkpoint proteins play a crucial role in the regulation of cellular immunity; however, their contribution to other aspects of cancer biology remains unclear. Accumulating evidence indicate that immune checkpoint proteins can regulate metabolic energetics of the tumor, the tumor microenvironment, and the tumor-specific immune response, leading to metabolic reprogramming of both malignant cells and immune cells involved in mounting and sustaining this response. Immune cell metabolism impacts the activation status of immune cells and ultimately the immune response in cancer. Tumor cells may deplete nutrients that immune cells require for optimal generation, expansion, and function. They may also generate toxic metabolites in the microenvironment or induce conserved inhibitory pathways that impair immune function and thus inhibit antitumor responses. In this review, we will discuss how cancer cells with altered expression of immune checkpoint proteins can potently inhibit immune function through the alteration of cellular and microenvironmental metabolism, providing a new perspective on the interplay between these pathways and offering a potential therapeutic intervention strategy in the treatment of malignant disease. Cancer Res; 77(6); 1245-9. ©2017 AACR.

BRD7 plays an anti-inflammatory role during early acute inflammation by inhibiting activation of the NF-кB signaling pathway.

Increasing evidence has shown a strong association between tumor-suppressor genes and inflammation. However, the role of BRD7 as a novel tumor suppressor in inflammation remains unknown. In this study, by observing BRD7 knockout mice for 6-12 months, we discovered that compared with BRD7+/+ mice, BRD7-/- mice were more prone to inflammation, such as external inflammation and abdominal abscess. By using mouse embryo fibroblast (MEF) cells from the BRD7 knockout mouse, an in vitro lipopolysaccharide (LPS)-stimulated MEF cell line was established. The mRNA levels of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), chemokine (C-X-C motif) ligand 1 (CXCL-1) and inducible nitric oxide synthase (iNOS) were significantly increased in BRD7-/- MEF cells compared with BRD7+/+ MEF cells after LPS stimulation for 1 or 6 h. In addition, the cytoplasm-to-nucleus translocation of nuclear factor kappa-B (NF-κB; p65) and an increased NF-κB reporter activity were observed in BRD7-/- MEF cells at the 1 h time point but not at the 6 h time point. Furthermore, an in vivo dextran sodium sulfate (DSS)-induced acute colitis model was created. As expected, the disease activity index (DAI) value was significantly increased in the BRD7-/- mice after DSS treatment for 1-5 days, which was demonstrated by the presence of a significantly shorter colon, splenomegaly and tissue damage. Moreover, higher expression levels of IL-6, TNF-α, p65, CXCL-1 and iNOS, and an increased level of NF-κB (p65) nuclear translocation were also found in the DSS-treated BRD7-/- mice. These findings suggest that BRD7 has an anti-inflammatory role during early acute inflammation by inhibiting activation of the NF-кB signaling pathway, which provides evidence to aid in understanding the therapeutic effects of BRD7 on inflammatory diseases.

Immunoregulatory Protein B7-H3 Reprograms Glucose Metabolism in Cancer Cells by ROS-Mediated Stabilization of HIF1α.

B7-H3 is a member of B7 family of immunoregulatory transmembrane glycoproteins expressed by T cells. While B7-H3 overexpression is associated with poor outcomes in multiple cancers, it also has immune-independent roles outside T cells and its precise mechanistic contributions to cancer are unclear. In this study, we investigated the role of B7-H3 in metabolic reprogramming of cancer cells in vitro and in vivo We found that B7-H3 promoted the Warburg effect, evidenced by increased glucose uptake and lactate production in B7-H3-expressing cells. B7-H3 also increased the protein levels of HIF1α and its downstream targets, LDHA and PDK1, key enzymes in the glycolytic pathway. Furthermore, B7-H3 promoted reactive oxygen species-dependent stabilization of HIF1α by suppressing the activity of the stress-activated transcription factor Nrf2 and its target genes, including the antioxidants SOD1, SOD2, and PRX3. Metabolic imaging of human breast cancer xenografts in mice confirmed that B7-H3 enhanced tumor glucose uptake and tumor growth. Together, our results illuminate the critical immune-independent contributions of B7-H3 to cancer metabolism, presenting a radically new perspective on B7 family immunoregulatory proteins in malignant progression. Cancer Res; 76(8); 2231-42. ©2016 AACR.

High Bak Expression Is Associated with a Favorable Prognosis in Breast Cancer and Sensitizes Breast Cancer Cells to Paclitaxel.

Breast cancer has become the leading cause of cancer-related death among women. A large number of patients become resistant to drug chemotherapy. Paclitaxel (Taxol) is an effective chemotherapeutic agent used to treat cancer patients. Taxol has been widely used in human malignancies including breast cancer because it can stabilize microtubules resulting in cell death by causing an arrest during the G2/M phase of the cell cycle. Pro-apoptotic Bcl-2 antagonist killer 1 (Bak) plays an important role in Taxol-induced apoptosis in breast cancer. In our present study, we investigated the expression of the Bak protein and clinicopathological correlations in a large sample of breast cancer tissues by immunohistochemistry. We found that the percentage of high scores of Bak expression in breast cancer was significantly lower than that of the non-cancerous breast control tissue. In addition, lower Bak expression was positively associated with the clinical TNM stage of breast cancer with a significant decrease in overall survival compared with those with higher Bak expression especially in the Luminal and HER2 subtypes. Importantly, higher Bak expression predicted a favorable clinical outcome in the cases treated with Taxol indicated by a higher overall survival than that of patients with lower Bak expression especially in Luminal and HER2 subtypes. Furthermore, these results were confirmed in vitro since overexpression of Bak sensitized breast cancer cells to Taxol by inhibiting proliferation and promoting apoptosis; in contrast, downregulation of Bak through siRNA transfection inhibited Taxol induced-apoptosis. Therefore, our results demonstrate that Bak acts as a sensitive biomarker and favorable prognostic factor for Taxol treatment in breast cancer. The restoration of Bak expression would be therapeutically beneficial for Taxol resistant breast cancer patients.

Natural product derivatives with bactericidal activity against Gram-positive pathogens including methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis.

We have shown that the intentional engineering of a natural product biosynthesis pathway is a useful way to generate stereochemically complex scaffolds for use in the generation of combinatorial libraries that capture the structural features of both natural products and synthetic compounds. Analysis of a prototype library based upon nonactic acid lead to the discovery of triazole-containing nonactic acid analogs, a new structural class of antibiotic that exhibits bactericidal activity against drug resistant, Gram-positive pathogens including Staphylococcus aureus and Enterococcus faecalis.

Nonactin biosynthesis: setting limits on what can be achieved with precursor-directed biosynthesis.

Nonactin, produced by Streptomyces griseus ETH A7796, is a macrotetrolide assembled from nonactic acid. It is an effective inhibitor of drug efflux in multidrug resistant erythroleukemia K562 cells at sub-toxic concentrations and has been shown to possess both antibacterial and antitumor activity. As total synthesis is impractical for the generation of nonactin analogs we have studied precursor-directed biosynthesis as an alternative as it is known that nonactic acid can serve as a nonactin precursor in vivo. To determine the scope of the approach we prepared and evaluated a furan-based nonactic acid derivative, 11. Although no new nonactin analogs were detected when 11 was administered to S. griseus fermentative cultures, a significant inhibition of nonactin biosynthesis was noted (IC(50) approximately 100 microM). Cell mass, nonactic acid production and the generation of other secondary metabolites in the culture were unaffected by 11 demonstrating that 11 selectively inhibited the assembly of nonactin from nonactic acid. While we were unable to generate new nonactin analogs we have discovered, however, a useful inhibitor that we can use to probe the mechanism of nonactin assembly with the ultimate goal of developing more successful precursor-directed biosynthesis transformations.