Potential predictive role of gut microbiota to immunotherapy in HCC patients: a brief review.

The recent evolution of immunotherapy has revolutionised the treatment of hepatocellular carcinoma (HCC) and has led to new therapeutic standards. The advances in immunotherapy have been accompanied by the recognition of the role of the gut-liver axis in the progression of HCC but also of the clinical relevance of the gut microbiota, which influences host homeostasis but also cancer development and the response to treatment. Dysbiosis, by altering the tumour microenvironment, favours the activation of intracellular signalling pathways and promotes carcinogenesis. The gut microbiota, through their composition and immunomodulatory role, are thus strong predictors of the response to immune checkpoint inhibitor (ICI) treatment as well as an available target to improve ICI efficacy and reduce drug toxicities. In this review we examine the novel role of the gut microbiota as biomarkers in both the diagnosis of HCC and the clinical response to immunotherapy as well as its potential impact on clinical practice in the future.

Crosstalk between ILC3s and Microbiota: Implications for Colon Cancer Development and Treatment with Immune Check Point Inhibitors.

Type 3 innate lymphoid cells (ILC3s) are primarily tissue-resident cells strategically localized at the intestinal barrier that exhibit the fast-acting responsiveness of classic innate immune cells. Populations of these lymphocytes depend on the transcription factor RAR-related orphan receptor and play a key role in maintaining intestinal homeostasis, keeping host-microbial mutualism in check. Current evidence has indicated a bidirectional relationship between microbiota and ILC3s. While ILC3 function and maintenance in the gut are influenced by commensal microbiota, ILC3s themselves can control immune responses to intestinal microbiota by providing host defense against extracellular bacteria, helping to maintain a diverse microbiota and inducing immune tolerance for commensal bacteria. Thus, ILC3s have been linked to host-microbiota interactions and the loss of their normal activity promotes dysbiosis, chronic inflammation and colon cancer. Furthermore, recent evidence has suggested that a healthy dialog between ILC3s and gut microbes is necessary to support antitumor immunity and response to immune checkpoint inhibitor (ICI) therapy. In this review, we summarize the functional interactions occurring between microbiota and ILC3s in homeostasis, providing an overview of the molecular mechanisms orchestrating these interactions. We focus on how alterations in this interplay promote gut inflammation, colorectal cancer and resistance to therapies with immune check point inhibitors.

Mechanical bacterial lysate enhances antimicrobial barrier mechanisms in human airway epithelial cells.

Polyvalent mechanical bacterial lysate is effective in the prevention of respiratory tract infections, although its mechanism of action is not entirely elucidated. Because epithelial cells constitute the frontline defense against infections, we investigated the molecular mechanisms of innate response exerted by bronchial epithelial cells in the presence of polyvalent mechanical bacterial lysate. By using primary human bronchial epithelial cells, we observed that polyvalent mechanical bacterial lysate was able to increase the expression of cellular adhesion molecules such as ICAM-1 and E-cadherin, as well as the expression of amphiregulin, a growth factor able to support human bronchial epithelial cell proliferation. Remarkably, polyvalent mechanical bacterial lysate promoted in human bronchial epithelial cells the de novo expression of human ß-defensin-2, a major antimicrobial peptide, conferring them a direct antimicrobial activity. Moreover, polyvalent mechanical bacterial lysate-stimulated human bronchial epithelial cells provided signals for increased IL-22 production by innate lymphoid cells via IL-23, which could further contribute to the release of antimicrobial peptides by epithelial cells. In agreement with these in vitro data, the concentration of both IL-23 and antimicrobial peptides (human ß-defensin-2 and LL-37) increased in the saliva of healthy volunteers after sublingual administration of polyvalent mechanical bacterial lysate. Altogether, these results indicate that polyvalent mechanical bacterial lysate administration might support mucosal barrier integrity and promote mechanisms of antimicrobial activity in airway epithelial cells.

Cutting Edge: Hyperinflammatory Monocytes Expressing CD56 Abound in Severe COVID-19 Patients.

Proinflammatory monocytes play a preponderant role in the development of a cytokine storm causing fatal consequences in coronavirus disease 2019 (COVID-19) patients, highlighting the importance of analyzing in more detail monocyte distribution in these patients. In this study, we identified an atypical monocyte subpopulation expressing CD56 molecules that showed a low level of HLA-DR and high level of l-selectin. They released higher amounts of TNF-α and IL-6 and expressed genes associated with an excessive inflammatory process. Remarkably, the frequency of CD56+ monocytes inversely correlated with that of CD16+ monocytes and a high CD56+/CD16+monocyte ratio was associated with both disease severity and mortality, as well as with serum concentration of type I IFN, a factor able to induce the appearance of CD56+ monocytes. In conclusion, severe COVID-19 is characterized by the abundance of hyperinflammatory CD56+ monocytes, which could represent a novel marker with prognostic significance and, possibly, a therapeutic target for controlling the inflammatory process occurring during COVID-19.

Attenuated immune control of Epstein-Barr virus in humanized mice is associated with the multiple sclerosis risk factor HLA-DR15.

Immune responses to Epstein-Barr virus (EBV) infection synergize with the main genetic risk factor HLA-DRB1*15:01 (HLA-DR15) to increase the likelihood to develop the autoimmune disease multiple sclerosis (MS) at least sevenfold. In order to gain insights into this synergy, we investigated HLA-DR15 positive human immune compartments after reconstitution in immune-compromised mice (humanized mice) with and without EBV infection. We detected elevated activation of both CD4+ and CD8+ T cells in HLA-DR15 donor-reconstituted humanized mice at steady state, even when compared to immune compartments carrying HLA-DRB1*04:01 (HLA-DR4), which is associated with other autoimmune diseases. Increased CD8+ T cell expansion and activation was also observed in HLA-DR15 donor-reconstituted humanized mice after EBV infection. Despite this higher immune activation, EBV viral loads were less well controlled in the context of HLA-DR15. Indeed, HLA-DR15-restricted CD4+ T cell clones recognized EBV-transformed B cell lines less efficiently and demonstrated cross-reactivity toward allogeneic target cells and one MS autoantigen. These findings suggest that EBV as one of the main environmental risk factors and HLA-DR15 as the main genetic risk factor for MS synergize by priming hyperreactive T-cell compartments, which then control the viral infection less efficiently and contain cross-reactive CD4+ T cell clones.

Phytochemicals, Antioxidant and Antiproliferative Properties of Rosmarinus officinalis L on U937 and CaCo-2 Cells.

Rosmarinus officinalis L., a medicinal herb from the labiates family, has been reported to have potential benefit in the treatment and prevention of several diseases. In particular its phenolics have demonstrated protective effects on various types of cancer through several mechanisms. The present study aimed to determine the effects of rosemary phenolic extracts on human cell functions, with particular regard to their anti-proliferative properties in three cell types U937, CaCo-2 and the peripheral blood mononuclear cells (PBMCs). The radical scavenging and Ferric reducing abilities of the extracts have been assessed as well as their cyto-toxicity and effects on cell cycle distribution and apoptosis. About 13 compounds were identified with dominance of rosmarinic acid in the methanolic extract and phenolic diterpens in the ethyl acetate fraction (Carnosol, Carnosic acid and methyl Carnosate). The total polyphenolic content was important in the first extract with 2.589 ± 0.005 g/100 g in gallic acid equivalent compared to 0.763 ± 0.005 g/100 g. The methanolic fraction displayed higher antioxidant activity (DPPHIC50: 0.510 mg/mL and FRAP: 1.714 ± 0.068 mmol Fe2+/g) while ethyl acetate showed pronounced antiproliferative effects (IC50: 14.85 ± 0.20µg/mL and 14.95 ± 2.32 µg/mL respectively for U937 and CaCo-2 cells). The anti-proliferative effect was associated with a cell cycle arrest in S phase for U937 (62% of the population at 5 µg/mL) with a concomitant decrease in G1 and G2/M phases. Tested extracts displayed in addition early apoptotic effects in U937 and late apoptosis in CaCo-2 cells. The obtained data indicate that the identified phenolics are at least partially responsible for the observed cytotoxicity.

MiRNA expression profiling in human gliomas: upregulated miR-363 increases cell survival and proliferation.

The role of microRNAs (miRNAs) in glioma biology is increasingly recognized. To investigate the regulatory mechanisms governing the malignant signature of gliomas with different grades of malignancy, we analyzed miRNA expression profiles in human grade I-IV tumor samples and primary glioma cell cultures. Multiplex real-time PCR was used to profile miRNA expression in a set of World Health Organization (WHO) grade I (pilocytic astrocytoma), II (diffuse fibrillary astrocytoma), and IV (glioblastoma multiforme) astrocytic tumors and primary glioma cell cultures. Primary glioma cell cultures were used to evaluate the effect of transfection of specific miRNAs and miRNA inhibitors. miRNA microarray showed that a set of miRNAs was consistently upregulated in all glioma samples. miR-363 was upregulated in all tumor specimens and cell lines, and its expression correlated with tumor grading. The transfection of glioma cells with the specific inhibitor of miR-363 increased the expression level of tumor suppressor growth-associated protein 43 (GAP-43). Transfection of miR-363 induced cell survival, while inhibition of miR-363 significantly reduced glioma cell viability. Furthermore, miRNA-363 inhibition induced the downregulation of AKT, cyclin-D1, matrix metalloproteinase (MMP)-2, MMP-9, and Bcl-2 and upregulation of caspase 3. Together, these data suggest that the upregulation of miR-363 may play a role in malignant glioma signature.

Cognate HLA absence in trans diminishes human NK cell education.

NK cells are innate lymphocytes with protective functions against viral infections and tumor formation. Human NK cells carry inhibitory killer cell Ig-like receptors (KIRs), which recognize distinct HLAs. NK cells with KIRs for self-HLA molecules acquire superior cytotoxicity against HLA- tumor cells during education for improved missing-self recognition. Here, we reconstituted mice with human hematopoietic cells from donors with homozygous KIR ligands or with a mix of hematopoietic cells from these homozygous donors, allowing assessment of the resulting KIR repertoire and NK cell education. We found that co-reconstitution with 2 KIR ligand-mismatched compartments did not alter the frequency of KIR-expressing NK cells. However, NK cell education was diminished in mice reconstituted with parallel HLA compartments due to a lack of cognate HLA molecules on leukocytes for the corresponding KIRs. This change in NK cell education in mixed human donor-reconstituted mice improved NK cell-mediated immune control of EBV infection, indicating that mixed hematopoietic cell populations could be exploited to improve NK cell reactivity against leukotropic pathogens. Taken together, these findings indicate that leukocytes lacking cognate HLA ligands can disarm KIR+ NK cells in a manner that may decrease HLA- tumor cell recognition but allows for improved NK cell-mediated immune control of a human γ-herpesvirus.

Divergent signaling pathways regulate IL-12 production induced by different species of Lactobacilli in human dendritic cells.

Recent studies have indicated that different strains of Lactobacilli differ in their ability to regulate IL-12 production by dendritic cells (DCs), as some strains are stronger inducer of IL-12 while other are not and can even inhibit IL-12 production stimulated by IL-12-inducer Lactobacilli. In this report we demonstrate that Lactobacillus reuteri 5289, as previously described for other strains of L. reuteri, can inhibit DC production of IL-12 induced by Lactobacilllus acidophilus NCFM. Remarkably, L. reuteri 5289 was able to inhibit IL-12 production induced not only by Lactobacilli, as so far reported, but also by bacteria of different genera, including pathogens. We investigated in human DCs the signal transduction pathways involved in the inhibition of IL-12 production induced by L. reuteri 5289, showing that this potential anti-inflammatory activity, which is also accompanied by an elevated IL-10 production, is associated to a prolonged phosphorilation of ERK1/2 MAP kinase pathway. Improved understanding of the immune regulatory mechanisms exerted by Lactobacilli is crucial for a more precise employment of these commensal bacteria as probiotics in human immune-mediated pathologies, such as allergies or inflammatory bowel diseases.

Drag cells in immunity: Plasmacytoid DCs dress up as cancer cells.

Cross-dressing, in immunology, is a term originally coined to indicate the transfer of peptide-MHC complexes belonging to neighboring cells on antigen presenting cells. We have recently shown that plasmacytoid dendritic cells (pDCs) are particularly suited to be cross-dressed by tumor cells and that this phenomenon provides a unique pathway for abundant presentation of tumor antigens by pDCs.

Membrane transfer from tumor cells overcomes deficient phagocytic ability of plasmacytoid dendritic cells for the acquisition and presentation of tumor antigens.

The potential contribution of plasmacytoid dendritic cells (pDCs) in the presentation of tumor cell Ags remains unclear, and some controversies exist with regard to the ability of pDCs to phagocytose cell-derived particulate Ags and cross-present them to MHC class I-restricted T lymphocytes. In this study, we show that human pDCs, although inefficient in the internalization of cell membrane fragments by phagocytosis, can efficiently acquire membrane patches and associated molecules from cancer cells of different histotypes. The transfer of membrane patches to pDCs occurred in a very short time and required cell-to-cell contact. Membrane transfer also included intact HLA complexes, and the acquired Ags could be efficiently recognized on pDCs by tumor-specific CD8(+) T cells. Remarkably, pDCs isolated from human colon cancer tissues displayed a strong surface expression of epithelial cell adhesion molecule, indicating that the exchange of exogenous Ags between pDCs and tumor cells also can occur in vivo. These data demonstrate that pDCs are well suited to acquire membrane patches from contiguous tumor cells by a cell-to-cell contact-dependent mechanism that closely resembles "trogocytosis." This phenomenon may allow pDCs to proficiently present tumor cell-derived Ags, despite limited properties of endophagocytosis.

Novel perspectives on dendritic cell-based immunotherapy of cancer.

Advances in immunobiology knowledge as well as in cell culture processes that generate large numbers of purified and functionally mature dendritic cells (DCs) have raised the possibility that DCs might represent promising clinical agents to generate effective immune responses against cancer. Here, we discuss the present pitfalls of dendritic cell vaccines for the treatment of human cancer with regard to the most recent knowledge in the biology of DCs. In particular, we highlight the relevance of improving our current understanding of DC trafficking, functions and interactions with other cells of innate immunity for the development of more effective cancer vaccines.

Seroma fluid subsequent to axillary lymph node dissection for breast cancer derives from an accumulation of afferent lymph.

Seroma is a frequent complication of breast cancer surgery, the etiology of which remains indefinite. It represents a subcutaneous accumulation of fluid frequently reported after surgical procedures such as axillary lymph node dissection. Despite previous studies have associated seroma fluid to an inflammatory exudate, the surgical removal of draining lymph nodes may indicate that seroma might not represent a mere exudate but rather an accrual of lymph drained from tributary tissues. To verify this hypothesis, seromas were collected at different intervals of time in patients operated upon for axillary lymph node removal. Fluids were analyzed in details by flow cytometry and biochemical assays for their cellular content and for their molecular features and relevant cytokine content. Lymphocytes and other peculiar blood mononuclear cells were present, while erythrocytes, platelets and granulocytes were absent or extremely rare. The protein concentration resulted lower (median 64%) than in peripheral blood. However, specific proteins related to locoregional tissues resulted highly concentrated (e.g. up to 500% for ferritin and 300% for lactate deydrogenase and exclusive presence of interleukin-6) whereas all enzymes and proteins synthesized in the liver or other organs (e.g. alkaline phosphatase, ALT, gammaGT, prealbumin, transferrin, ceruloplasmin, C3 and C4, alpha2 macroglobulin from liver; apolipoproteins from liver and gut; amylase and lipase from pancreas) were represented in reduced concentrations, thus ruling out that seroma proteins derive directly from blood serum. As a whole, this comprehensive cytological and molecular analysis provided evidences that seroma is constituted by serum ultrafiltrated-derived extracellular fluid of regions located upstream of removed lymph nodes. This fluid is then enriched by proteins and cells collected in the drained regions. Remarkably, seroma fluids collected in the same patient at different time points (up to 50 days following surgery) displayed similar biochemical features, clearly indicating that fluid composition was not significantly affected by post-surgical locoregional flogosis. Finally, the period of seroma formation indicates that lymph accumulates in the axillary region during the interval of time needed for afferent lymphatic vessels to re-anastomose with the efferent ducts. Therefore, seroma fluid represents a font of biological material suitable for investigating the biology of breast cancer, healing tissues and lymph.

Susceptibility of human melanoma cells to autologous natural killer (NK) cell killing: HLA-related effector mechanisms and role of unlicensed NK cells.

BACKGROUND: Despite Natural Killer (NK) cells were originally defined as effectors of spontaneous cytotoxicity against tumors, extremely limited information is so far available in humans on their capability of killing cancer cells in an autologous setting. METHODOLOGY/PRINCIPAL FINDINGS: We have established a series of primary melanoma cell lines from surgically resected specimens and here showed that human melanoma cells were highly susceptible to lysis by activated autologous NK cells. A variety of NK cell activating receptors were involved in killing: particularly, DNAM-1 and NKp46 were the most frequently involved. Since self HLA class I molecules normally play a protective role from NK cell-mediated attack, we analyzed HLA class I expression on melanomas in comparison to autologous lymphocytes. We found that melanoma cells presented specific allelic losses in 50% of the patients analyzed. In addition, CD107a degranulation assays applied to NK cells expressing a single inhibitory receptor, revealed that, even when expressed, specific HLA class I molecules are present on melanoma cell surface in amount often insufficient to inhibit NK cell cytotoxicity. Remarkably, upon activation, also the so called "unlicensed" NK cells, i.e. NK cells not expressing inhibitory receptor specific for self HLA class I molecules, acquired the capability of efficiently killing autologous melanoma cells, thus additionally contributing to the lysis by a mechanism independent of HLA class I expression on melanoma cells. CONCLUSIONS/SIGNIFICANCE: We have investigated in details the mechanisms controlling the recognition and lysis of melanoma cells by autologous NK cells. In these autologous settings, we demonstrated an efficient in vitro killing upon NK cell activation by mechanisms that may be related or not to abnormalities of HLA class I expression on melanoma cells. These findings should be taken into account in the design of novel immunotherapy approaches against melanoma.

Human leukocyte antigen frequency in human high-grade gliomas: a case-control study in Sicily.

OBJECTIVE: Human leukocyte antigens (HLAs) are widely expressed cell surface molecules that present antigenic peptides to T lymphocytes and modulate immune response against inflammatory and malignant diseases. The aim of this study was to compare HLA distribution in patients with newly diagnosed high-grade gliomas (HGGs) and 2 control groups from a restricted geographic area (eastern Sicily). METHODS: HLA allele frequency, as determined from peripheral blood of 56 adult patients with HGGs, was compared with that of 2 different control groups: 140 healthy bone marrow donors (group A) and 69 virtually brain tumor-free patients (group B). HLA expression was evaluated using a reverse transcriptase polymerase chain reaction-sequence-specific oligonucleotide probe. RESULTS: There was significant expression of HLA-A*11 in patients with HGGs compared with control groups A and B (P < 0.003 and P < 0.018, respectively). Significant expression of HLA genotypes in patients with HGGs was also identified for HLA-DQB1*06 (P = 0.005), HLA-DRB1*14 (P = 0.001), and HLA-DRB3*01 (P = 0.007) compared with control group B. In HGG patients, there was statistically significantly decreased expression, compared with control groups A and B, of HLA-B*07 (P = 0.002 and P = 0.03, respectively) and HLA-C*04 (P = 0.007 and P = 0.016, respectively). There was statistically significant lower expression of HLA-C*05 in the HGG group compared with group B (P < 0.03). CONCLUSION: This is the first study to describe the frequency of distribution of HLAs in a population from a restricted geographic area. The findings suggest a possible correlation between HLA allele distribution and the occurrence of newly diagnosed malignant astroglial brain tumors.

Role of natural killer cells in the pathogenesis and progression of multiple sclerosis.

Natural killer (NK) cells are a subset of lymphocytes which have long been alleged to play an immunoregulatory role in the prevention of autoimmune diseases. Here, we briefly review NK cell features and the major findings from studies on NK cells in human and animals susceptible to multiple sclerosis (MS). Although most studies in human seem to suggest an association between disease and deficiencies in NK cells, it is also clear that NK cells can be both protective and pathogenic in MS models. These contrasting observations could result from differences in experimental procedures as well as from differences in NK cell subset targeted. Whatever the case, the functional features of these cells and their potential role in regulation of autoimmunity suggest that NK cell-based therapies might be an interesting approach for the treatment of multiple sclerosis.