β2-adrenergic signaling promotes higher-affinity B cells and antibodies

Stress-induced β2-adrenergic receptor (β2AR) activation in B cells increases IgG secretion; however, the impact of this activation on antibody affinity and the underlying mechanisms remains unclear. In the current study, we demonstrate that stress in mice following ovalbumin (OVA) or SARS-CoV-2 RBD immunization significantly increases both serum and surface-expressed IgG binding to the immunogen, while concurrently reducing surface IgG expression and B cell clonal expansion. These effects were abolished by pharmacological β2AR blocking or when the experiments were conducted in β2AR -/- mice. In the second part of our study, we used single B cell sorting to characterize the monoclonal antibodies (mAbs) generated following β2AR activation in cultured RBD-stimulated B cells from convalescent SARS-CoV-2 donors. Ex vivo β2AR activation increased the affinities of the produced anti-RBD mAbs by 100-fold compared to mAbs produced by the same donor control cultures. Consistent with the mouse experiments, β2AR activation reduced both surface IgG levels and the frequency of expanded clones. mRNA sequencing revealed a β2AR-dependent upregulation of the PI3K pathway and B cell receptor (BCR) signaling through AKT phosphorylation, as well as an increased B cell motility. Overall, our study demonstrates that stress-mediated β2AR activation drives changes in B cells associated with BCR activation and higher affinity antibodies.

Human antibodies targeting a Mycobacterium transporter protein mediate protection against tuberculosis

Mycobacterium tuberculosis (Mtb) exposure drives antibody responses, but whether patients with active tuberculosis elicit protective antibodies, and against which antigens, is still unclear. Here we generate monoclonal antibodies from memory B cells of one patient to investigate the B cell responses during active infection. The antibodies, members of four distinct B cell clones, are directed against the Mtb phosphate transporter subunit PstS1. Antibodies p4-36 and p4-163 reduce Mycobacterium bovis-BCG and Mtb levels in an ex vivo human whole blood growth inhibition assay in an FcR-dependent manner; meanwhile, germline versions of p4-36 and p4-163 do not bind Mtb. Crystal structures of p4-36 and p4-170, complexed to PstS1, are determined at 2.1 Å and 2.4 Å resolution, respectively, to reveal two distinctive PstS1 epitopes. Lastly, a prophylactic p4-36 and p4-163 treatment in Mtb-infected Balb/c mice reduces bacterial lung burden by 50%. Our study shows that inhibitory anti-PstS1 B cell responses arise during active tuberculosis.

Bone marrow-derived fibroblasts are a functionally distinct stromal cell population in breast cancer

Raz et al. demonstrate that the expression of PDGFRα distinguishes two functional CAF populations in breast tumors and lung metastases and identify a subpopulation of CAFs that are specifically recruited to the tumor microenvironment from mesenchymal stromal cells in the BM.

Cancer-associated fibroblasts (CAFs) are highly prominent in breast tumors, but their functional heterogeneity and origin are still largely unresolved. We report that bone marrow (BM)–derived mesenchymal stromal cells (MSCs) are recruited to primary breast tumors and to lung metastases and differentiate to a distinct subpopulation of CAFs. We show that BM-derived CAFs are functionally important for tumor growth and enhance angiogenesis via up-regulation of Clusterin. Using newly generated transgenic mice and adoptive BM transplantations, we demonstrate that BM-derived fibroblasts are a substantial source of CAFs in the tumor microenvironment. Unlike resident CAFs, BM-derived CAFs do not express PDGFRα, and their recruitment resulted in a decrease in the percentage of PDGFRα-expressing CAFs. Strikingly, decrease in PDGFRα in breast cancer patients was associated with worse prognosis, suggesting that BM-derived CAFs may have deleterious effects on survival. Therefore, PDGFRα expression distinguishes two functionally unique CAF populations in breast tumors and metastases and may have important implications for patient stratification and precision therapeutics.

Fibroblasts drive an immunosuppressive and growth-promoting microenvironment in breast cancer via secretion of Chitinase 3-like 1

Cancer-Associated Fibroblasts (CAFs) are the most prominent stromal cell type in breast tumors. CAFs promote tumor growth and metastasis by multiple mechanisms, including by mediating tumor-promoting inflammation. Immune modulation in the tumor microenvironment plays a central role in determining disease outcome. However, the functional interactions of CAFs with immune cells are largely unknown. Here we report a novel signaling axis between fibroblasts, cancer cells and immune cells in breast tumors that drives an immunosuppressive microenvironment, mediated by CAF-derived Chi3L1. We demonstrate that Chi3L1 is highly upregulated in CAFs isolated from mammary tumors and pulmonary metastases of transgenic mice, and in the stroma of human breast carcinomas. Genetic ablation of Chi3L1 in fibroblasts in vivo attenuated tumor growth, macrophage recruitment and reprogramming to an M2-like phenotype, enhanced tumor infiltration by CD8⁺ and CD4⁺ T cells and promoted a Th1 phenotype. These results indicate that CAF-derived Chi3L1 promotes tumor growth and shifts the balance of the immune milieu towards type 2 immunity. Taken together, our findings implicate fibroblast-derived Chi3L1 as a novel key player in the complex reciprocal interactions of stromal cells that facilitate tumor progression and metastasis, and suggest that targeting Chi3L1 may be clinically beneficial in breast cancer.

Incipient Melanoma Brain Metastases Instigate Astrogliosis and Neuroinflammation

Malignant melanoma is the deadliest of skin cancers. Melanoma frequently metastasizes to the brain, resulting in dismal survival. Nevertheless, mechanisms that govern early metastatic growth and the interactions of disseminated metastatic cells with the brain microenvironment are largely unknown. To study the hallmarks of brain metastatic niche formation, we established a transplantable model of spontaneous melanoma brain metastasis in immunocompetent mice and developed molecular tools for quantitative detection of brain micrometastases. Here we demonstrate that micrometastases are associated with instigation of astrogliosis, neuroinflammation, and hyperpermeability of the blood-brain barrier. Furthermore, we show a functional role for astrocytes in facilitating initial growth of melanoma cells. Our findings suggest that astrogliosis, physiologically instigated as a brain tissue damage response, is hijacked by tumor cells to support metastatic growth. Studying spontaneous melanoma brain metastasis in a clinically relevant setting is the key to developing therapeutic approaches that may prevent brain metastatic relapse. Cancer Res; 76(15); 4359-71. ©2016 AACR.

Precision nanomedicine in neurodegenerative diseases

The treatment of neurodegenerative diseases remains a tremendous challenge due to the limited access of molecules across the blood-brain barrier, especially large molecules such as peptides and proteins. As a result, at most, a small percentage of a drug that is administered systemically will reach the central nervous system in its active form. Currently, research in the field focuses on developing safer and more effective approaches to deliver peptides and proteins into the central nervous system. Multiple strategies have been developed for this purpose. However, noninvasive approaches, such as nanostructured protein delivery carriers and intranasal administration, seem to be the most promising strategies for the treatment of chronic diseases, which require long-term interventions. These approaches are both target-specific and able to rapidly bypass the blood-brain barrier. In this Perspective, we detail some of these strategies and discuss some of the potential pitfalls and opportunities in this field. The next generation strategies will most likely be more cell-type-specific. Devising these strategies to target the brain may ultimately become a novel therapeutic modality to treat neurodegenerative diseases.

KL1 internal repeat mediates klotho tumor suppressor activities and inhibits bFGF and IGF-I signaling in pancreatic cancer

PURPOSE

Klotho is a transmembrane protein which can be shed, act as a circulating hormone and modulate the insulin-like growth factor (IGF)-I and the fibroblast growth factor (FGF) pathways. We have recently identified klotho as a tumor suppressor in breast cancer. Klotho is expressed in the normal pancreas and both the IGF-I and FGF pathways are involved in pancreatic cancer development. We, therefore, undertook to study the expression and activity of klotho in pancreatic cancer.

EXPERIMENTAL DESIGN

Klotho expression was studied using immunohistochemistry and quantitative RT-PCR. Effects of klotho on cell growth were assessed in the pancreatic cancer cells Panc1, MiaPaCa2, and Colo357, using colony and MTT assays and xenograft models. Signaling pathway activity was measured by Western blotting.

RESULTS

Klotho expression is downregulated in pancreatic adenocarcinoma. Overexpression of klotho, or treatment with soluble klotho, reduced growth of pancreatic cancer cells in vitro and in vivo, and inhibited activation of the IGF-I and the bFGF pathways. KL1 is a klotho subdomain formed by cleavage or alternative splicing. Compared with the full-length protein, KL1 showed similar growth inhibitory activity but did not promote FGF23 signaling. Thus, its administration to mice showed favorable safety profile.

CONCLUSIONS

These studies indicate klotho as a potential tumor suppressor in pancreatic cancer, and suggest, for the first time, that klotho tumor suppressive activities are mediated through its KL1 domain. These results suggest the use of klotho or KL1 as potential strategy for the development of novel therapeutic interventions for pancreatic cancer.

Functional variant of KLOTHO: a breast cancer risk modifier among BRCA1 mutation carriers of Ashkenazi origin

Klotho is a transmembrane protein that can be shed and act as a circulating hormone and is a putative tumor suppressor in breast cancer. A functional variant of KLOTHO (KL-VS) contains two amino acid substitutions F352V and C370S and shows reduced activity. Germ-line mutations in BRCA1 and BRCA2 substantially increase lifetime risk of breast and ovarian cancers. Yet, penetrance of deleterious BRCA1 and BRCA2 mutations is incomplete even among carriers of identical mutations. We examined the association between KL-VS and cancer risk among 1115 Ashkenazi Jewish women: 236 non-carriers, 631 BRCA1 (185delAG, 5382insC) carriers and 248 BRCA2 (6174delT) carriers. Among BRCA1 carriers, heterozygosity for the KL-VS allele was associated with increased breast and ovarian cancer risk (hazard ratio 1.40, 95% confidence intervals 1.08-1.83, P=0.01) and younger age at breast cancer diagnosis (median age 48 vs 43 P=0.04). KLOTHO and BRCA2 are located on 13q12, and we identified linkage disequilibrium between KL-VS and BRCA2 6174delT mutation. Studies in breast cancer cells showed reduced growth inhibitory activity and reduced secretion of klotho F352V compared with wild-type klotho. These data suggest KL-VS as a breast and ovarian cancer risk modifier among BRCA1 mutation carriers. If validated in additional cohorts, the presence of KL-VS may serve as a predictor of cancer risk among BRCA1 mutation carriers.

Nonsteroidal anti-inflammatory drugs suppress glioma via 15-hydroxyprostaglandin dehydrogenase

Studies have conjectured that nonsteroidal anti-inflammatory drugs (NSAID) inhibit growth of various malignancies by inhibiting cyclooxygenase-2 (COX-2) enzyme activity. Yet, several lines of evidence indicate that a COX-2-independent mechanism may also be involved in their antitumor effects. Here, we report that NSAIDs may inhibit the growth of glioblastoma multiforme (GBM) cells through COX-2-independent mechanisms, including up-regulation of both 15-hydroxyprostaglandin dehydrogenase (15-PGDH, the key prostaglandin catabolic enzyme) and the cell cycle inhibitor p21. Using Western blot and real-time PCR analysis in various GBM cell lines, we observed up-regulation of 15-PGDH and p21 after NSAIDs treatment. To elucidate the role of 15-PGDH in GBM, transfection assays were conducted using the T98G GBM cell line. Overexpression of 15-PGDH suppressed cell growth and was associated with increased expression of p21. In an attempt to investigate the roles of COX-2, 15-PGDH, and p21 in the inhibition of growth of GBM, small interfering RNA (siRNA) against each of these proteins was transfected into T98G cells. Inhibition of growth mediated by NSAIDs was partially reversed after knockdown of either 15-PGDH or p21, but not after COX-2 knockdown. Moreover, expression level of p21 was not affected in COX-2 siRNA transfected cells. Our studies provide evidence that the up-regulation of 15-PGDH induced by NSAIDs has the potential to inhibit growth of GBM, in part, by up-regulation of p21 possibly independent from COX-2 enzymatic function.

Dual role of NRSF/REST in activation and repression of the glucocorticoid response

Restriction of glutamine synthetase to the nervous system is mainly achieved through the mutual function of the glucocorticoid receptor and the neural restrictive silencing factor, NRSF/REST. Glucocorticoids induce glutamine synthetase expression in neural tissues while NRSF/REST represses the hormonal response in non-neural cells. NRSF/REST is a modular protein that contains two independent repression domains, at the N and C termini of the molecule, and is dominantly expressed in nonneural cells. Neural tissues express however splice variants, REST4/5, which contain the repression domain at the N, but not at the C terminus of the molecule. Here we show that full-length NRSF/REST or its C-terminal domain can inhibit almost completely the induction of gene transcription by glucocorticoids. By contrast, the N-terminal domain not only fails to repress the hormonal response but rather stimulates it markedly. The inductive activity of the N-terminal domain is mediated by hBrm, which is recruited to the promoter only in the concomitant presence of GR. Importantly, a similar inductive activity is also exerted by the splice variant REST4. These findings raise the possibility that NRSF/REST exhibits a dual role in regulation of glutamine synthetase. It represses gene induction in nonneural cells and enhances the hormonal response, via its splice variant, in the nervous system.

The unpredictability of seal after post space preparation: a fluid transport study

A root canal filling remaining after post space preparation is commonly expected to provide adequate seal. Coronal leakage of 30 endodontically treated teeth was measured before post space preparation using a fluid transport assay. In 10 of these teeth post space was prepared, using a two-step procedure, first to a remaining filling of 6 mm and then to 3 mm, with the leakage studied after each step. In 10 teeth the removal was done in one step to a remaining length of 3 mm. The other 10 teeth, with intact root canal fillings, served as controls and were tested twice for leakage. A significant difference was found between the sealing ability of intact fillings and that of partially removed ones (p < 0.05). The difference between the sealing ability of 3 and 6 mm remaining length group was not statistically significant. The lack of statistical differences between the 6 mm and 3 mm fillings was due to a great variability which existed among the 3 mm remaining fillings. These results suggest that 3 to 6 mm fillings provided a seal inferior to that of intact root canal fillings. Reduction of the fillings to 3 mm resulted in an unpredictable seal.

Correlation between remaining length of root canal fillings after immediate post space preparation and coronal leakage

The seal provided by root canal fillings after post space preparation was studied using a pressure-driven radioactive tracer assay. The coronal part of root canal fillings was immediately removed, using a hot plugger, to a remaining length of either 3, 5, 7, or 9 mm. Intact root canal fillings of 14 mm served as control. Application of air pressure of 130 mm Hg to the tracer solution drove it through the fillings and into phosphate-buffered saline surrounding the apex. Leakage gradually increased for 28 days, and differences in the leakage through 3 to 9 mm fillings were demonstrated. In a passive system by which an additional group of teeth were tested none of these differences could be detected. It was concluded that: (a) root canal fillings of 3, 5, and 7 mm have an inferior seal, compared with that of an intact filling; (b) the sealing is proportional to the length of the remaining filling; and (c) a passive system is unable to detect these differences, even when conducted for as long as 28 days.

Starved Saccharomyces cerevisiae cells have the capacity to support internal initiation of translation

Internal initiation of translation, whereby ribosomes are directed to internal AUG codon independently of the 5' end of the mRNA, has been observed rarely in higher eucaryotes and has not been demonstrated in living yeast. We report here that starved yeast cells are capable of initiating translation of a dicistronic message internally. The studied element that functions as an internal ribosome entry site (IRES) is hardly functional or not functional at all in logarithmically growing cells. Moreover, during the logarithmic growth phase, this element seems to inhibit translation reinitiation when placed as an intercistronic spacer or to inhibit translation when placed in the 5'-untranslated region of a monocistronic message. Inhibition of translation is likely due to the putative strong secondary structure of the IRES that interferes with the cap-dependent scanning process. When cells exit the logarithmic growth phase, or when artificially starved for carbon source, translation of the IRES-containing messages is substantially induced. Our findings imply that the capacity to translate internally is a characteristic of starved rather than vegetatively growing yeast cells.