Marine Invertebrates: A Promissory Still Unexplored Source of Inhibitors of Biomedically Relevant Metallo Aminopeptidases Belonging to the M1 and M17 Families

Proteolytic enzymes, also known as peptidases, are critical in all living organisms. Peptidases control the cleavage, activation, turnover, and synthesis of proteins and regulate many biochemical and physiological processes. They are also involved in several pathophysiological processes. Among peptidases, aminopeptidases catalyze the cleavage of the N-terminal amino acids of proteins or peptide substrates. They are distributed in many phyla and play critical roles in physiology and pathophysiology. Many of them are metallopeptidases belonging to the M1 and M17 families, among others. Some, such as M1 aminopeptidases N and A, thyrotropin-releasing hormone-degrading ectoenzyme, and M17 leucyl aminopeptidase, are targets for the development of therapeutic agents for human diseases, including cancer, hypertension, central nervous system disorders, inflammation, immune system disorders, skin pathologies, and infectious diseases, such as malaria. The relevance of aminopeptidases has driven the search and identification of potent and selective inhibitors as major tools to control proteolysis with an impact in biochemistry, biotechnology, and biomedicine. The present contribution focuses on marine invertebrate biodiversity as an important and promising source of inhibitors of metalloaminopeptidases from M1 and M17 families, with foreseen biomedical applications in human diseases. The results reviewed in the present contribution support and encourage further studies with inhibitors isolated from marine invertebrates in different biomedical models associated with the activity of these families of exopeptidases.

Bufadienolides preferentially inhibit aminopeptidase N among mammalian metallo-aminopeptidases; relationship with effects on human melanoma MeWo cells

Bufadienolides are steroids that inhibit Na⁺/K⁺-ATPase; recent evidence shows that bufalin inhibits the activity of porcine aminopeptidase N (pAPN). We evaluated the selectivity of some bufadienolides on metallo-aminopeptidases. Among the enzymes of the M1 and M17 families, pAPN and porcine aminopeptidase A (pAPA) were the only targets of some bufadienolides. ѱ-bufarenogin, telocinobufagin, marinobufagin, bufalin, cinobufagin, and bufogenin inhibited the activity of pAPN in a dose-dependent manner in the range of 10^-7-10^-6 M. The inhibition mechanism was classical reversible noncompetitive for telocinobufagin, bufalin and cinobufagin. Bufogenin had the lowest K_i value and a non-competitive behavior. pAPA activity was inhibited by ѱ-bufarenogin, cinobufagin, and bufogenin, with a classical competitive type of inhibition. The models of enzyme-inhibitor complexes agreed with the non-competitive type of inhibition of pAPN by telocinobufagin, bufalin, cinobufagin, and bufogenin. Since APN is a target in cancer therapy, we tested the effect of bufadienolides on the MeWo APN+ human melanoma cell line; they induced cell death, but we obtained scant evidence that inhibition of APN contributed to their effect. Thus, APN is a selective target of some bufadienolides, and we suggest that inhibition of APN activity by bufadienolides is not a major contributor to their antiproliferative properties in MeWo cells.

Assessment of changes in immune status linked to COVID-19 convalescent and its clinical severity in patients and uninfected exposed relatives

INTRODUCTION

The immune response during and after SARS-CoV-2 infection can be complex and heterogeneous, and it can be affected by the severity of the disease. It can also contribute to an unfavorable evolution and bring about short and long term effects. The aim of this study was to characterize the lymphocyte composition according to the severity of COVID-19, as well as its degree of relationship to the specific humoral response to SARS-CoV-2 in convalescents up to 106 days after the infection and in their exposed relatives.

METHODS

An applied research was carried out with a cross-section analytical design, from March 11 to June 11, 2020 in Cuba. The sample consisted of 251 convalescents from COVID-19 over 18 years of age and 88 exposed controls who did not become ill. The B and T cell subpopulations, including memory T cells, as well as the relationship with the humoral immune response against SARS-CoV-2, were identified by flow cytometry and enzyme immunoassay.

RESULTS

Convalescent patients, who evolved with severe forms, showed a decrease in frequency and a greater proportion of individuals with values ​​lower than the minimum normal range of B cells, CD3 + CD4 + cells and the CD4 + / CD8 + ratio, as well as a higher frequency and a greater proportion of individuals with values ​​above the normal maximum range of CD3 + CD8 + and NK cells. Convalescent patients with severe forms of COVID-19 that exhibited IgG / RBD titers ≥ 1/200 had a lower frequency of TEMRA CD8 + cells (p = 0.0128) and TEMRA CD4 + (p = 0.0068). IgG / RBD titers were positively correlated with the relative frequency of CD4 + CM T memory cells (r = 0.4352, p = 0.0018).

CONCLUSIONS

The identified alterations of B and T lymphocytes suggest that convalescent patients with the severe disease could be vulnerable to infectious, autoimmune or autotinflammatory processes; therefore, these individuals need medical follow-up after recovering from the acute disease. Furthermore, the role of T cells CD4 + CM in the production of antibodies against SARS-CoV-2 is confirmed, and it is noted that the defect of memory T cells CD8 + TEMRA could contribute to the development of severe forms of COVID-19.

Immuno-toxicological evaluation of her1 cancer vaccine in non-human primates: a 6-month subcutaneous study

Purpose: A vaccine composition based on the extracellular domain of the human epidermal growth factor receptor 1 (HER1-ECD) and the combination of VSSP (very small size proteoliposomes) and Montanide ISA 51 adjuvants when used by intramuscular route, demonstrated promising results in preclinical studies. However, in order to avoid potential adverse events due to the use of Montanide, it is proposed to modify the vaccine formulation by using VSSP (very small size proteoliposomes) adjuvant alone, and to evaluate the quality of subcutaneously induced immune response. This study aimed to assess the immunotoxicological effects of HER1 vaccine in Cercopithecus aethiops.Materials and methods: Fifteen monkeys were randomized into four groups: Negative Control (Tris/NaCl, s.c.), Positive Control (200 µg HER1-ECD/VSSP/Montanide ISA-51 VG, i.m), Low Dose (200 µg HER1-ECD/VSSP/Tris NaCl, s.c.) and High Dose (800 µg HER1-ECD/VSSP/Tris NaCl, s.c). All monkeys received 7 doses and were daily inspected for clinical signs. Body weight, rectal temperature, cardiac and respiratory rates were measured during the study, and electrocardiographical and ophthalmological studies were performed. Humoral and cellular immune response and clinical pathology parameters were analyzed.Results: Animal's survival in the study was 100% (n = 15). Administration site reactions were observed in the Positive Control animals (n = 4). HER1 vaccine administered subcutaneously (High Dose Group) achieved good IgG antibody titers although lower than the Positive Control group, but with higher ability to inhibit HER1 phosphorylation. Conclusions: This suggests that the alternative of eliminating the use of Montanide in the HER1 vaccine preparation and the using subcutaneous route is feasible.

Targeting autocrine amphiregulin robustly and reproducibly inhibits ovarian cancer in a syngeneic model: roles for wildtype p53

Ovarian cancer (OvCA) remains one of the most devastating malignancies, but treatment options are still limited. We report that amphiregulin (AREG) can serve as an effective and safe pharmacological target in a syngeneic murine model. AREG is highly abundant in abdominal fluids of patients with advanced OvCa. In immunocompetent animals, depletion or overexpression of AREG respectively prolonged or shortened animal survival. A new antibody we generated in AREG-knockout mice recognized murine AREG and reproducibly prolonged animal survival in the syngeneic model. The underlying mechanism likely involves binding of wildtype p53 to AREG's promoter and autocrine activation of the epidermal growth factor receptor (EGFR), a step blocked by the antibody. Accordingly, depletion of p53 downregulated AREG secretion and conferred tolerance, whereas blocking an adaptive process involving CXCL1, which transactivates EGFR, might increase therapeutic efficacy. Consistent with these observations, analysis of OvCa patients revealed that high AREG correlates with poor prognosis of patients expressing wildtype TP53. In conclusion, clinical tests of the novel antibody are warranted; high AREG, normal TP53, and reduced CXCL1 activity might identify patients with OvCa who may derive therapeutic benefit.

Growing spheroids of lung adenosquamous carcinoma on electrospun poly(ε-caprolactone)

Lung adenosquamous carcinomas, cell line H125, with an expression of human epidermal growth factor receptor 1 (HER1), were cultured on two scaffolds of poly(ε-caprolactone) produced through electrospinning, one with a nanometric size and the other with a micrometric size. Cytotoxicity, adhesion and proliferation assays demonstrated the non-cytotoxicity of the scaffolds and the capacity of the cells to grow on them. Tumorlike morphology of cells, HER1 expression and the initial formation of invadopodia were detected through fluorescence microscopy. In the nanometric scaffolds, spheroid formation of cancerous cells was observed. Cells cultured in nanometric scaffolds presented higher resistance to cetuximab than those cultured in micrometric ones and also than cells of two-dimensional cultures. This work demonstrated the potentialities of poly(ε-caprolactone) scaffolds for lung adenosquamous carcinoma cultures and is an initial step for further studies on the growth of cancer cell spheroids on electrospun nanofibers.

HER1-based vaccine: Simultaneous activation of humoral and cellular immune response

The human epidermal growth factor receptor 1 (HER1) is a tumor-associated antigen that has been validated as a clinical target for several passive, non-immune therapies currently approved for the treatment of epithelial tumors. HER1 is an oncogene that not only promotes tumor progression and survival, but also immune escape. Its overexpression in some epithelial malignancies has been correlated with a poor prognosis. We developed an approach to target HER1 by specific active immunotherapy, recognizing the extracellular domain of the receptor, using a combination of VSSP and Montanide ISA 51 as adjuvants. We summarize the results obtained with this vaccine in both the preclinical and clinical settings, emphasizing the importance of the induction of both humoral and cellular responses for the success of cancer vaccines as safe therapeutic alternatives for the treatment of cancer.

Anti-proliferative and pro-apoptotic effects induced by simultaneous inactivation of HER1 and HER2 through endogenous polyclonal antibodies

The human epidermal growth factor receptor (HER1) and its partner HER2 are extensively described oncogenes and validated targets for cancer therapy. However, the effectiveness of monospecific therapies targeting these receptors is hampered by resistance emergence, which is frequently associated with the upregulation of other members of HER family. Combined therapies using monoclonal antibodies or tyrosine kinase inhibitors have been suggested as a promising strategy to circumvent this resistance mechanism. We propose an alternative approach based on simultaneous inactivation of HER1 and HER2 by multi-epitope blockade with specific polyclonal antibodies induced by vaccination. Elicited antibodies impaired both receptors activation and induced their degradation, which caused the inhibition of down-signaling cascades. This effect was translated into cell cycle arrest and apoptosis induction of human tumor cells. Elicited antibodies were able to reduce the viability of a panel of human tumor lines with differential expression levels of HER1 and HER2. The most significant effects were obtained in the tumor lines with lower expression levels of both receptors. These new insights would contribute to the rational design of HER receptors targeting multivalent vaccines, as an encouraging approach for the treatment of cancer patients.

Pharmacokinetics and Biodistribution Study of 7A7 Anti-Mouse Epidermal Growth Factor Receptor Monoclonal Antibody and Its F(ab')(2) Fragment in an Immunocompetent Mouse Model

Immunocompetent mice, Fc receptor γ-chain deficient mice (Fcer1g^−/−), and molecular tools as F(ab′)₂ bivalent fragments appear as the most suitable biological models to study the mechanisms of the action of anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (mAbs). In vivo experiments contrasting antitumor effects of whole Abs and their bivalent fragments commonly involve a previous comparative pharmacokinetics study. In this paper, pharmacokinetics and biodistribution of an anti-mouse EGFR Ab were assessed using immunocompetent mice. ¹²⁵I-labeled 7A7 mAb holds an elimination half-life (t_1/2β) of 23.1 h in C57BL/6 mice. Accumulation of mAb was found in liver, spleen, kidneys, and mostly in lungs. We used an ELISA method to determine the t_1/2β of a 7A7 mAb using the same experimental setting. Results from this new analysis revealed a t_1/2β of 23.9 h, supporting this method as a safer and easier system to evaluate pharmacokinetics parameters of mAbs targeting mouse EGFR. Using this system we also studied pharmacokinetics of 7A7 F(ab′)₂ fragment. A tenfold difference between the mAb and fragment t_1/2β was found. These data support the use of the 7A7 F(ab′)₂ fragment in in vivo studies to explore the contribution of the EGFR signaling blockade and the Fc region to the antitumor effect of 7A7 mAb in this autologous scenario.

Lentiviral vector followed by protein immunisation breaks tolerance against the self-antigen Her1 and results in lung cancer immunotherapy

BACKGROUND

Lung cancer remains a leading cause of cancer mortality, and so the aim of the present study was to develop a therapeutic vaccine protocol.

METHODS

We constructed a lentiviral vector (LV) expressing the extracellular domain (ECD) of murine Her1, an antigen associated with poor prognosis in lung cancer.

RESULTS

A single LV injection, followed by two Her1 protein boosts, was effective in reducing the metastatic burden of Lewis lung carcinoma in mice. The Her1 LV immunisation generated CD8+ T cells that recognised Her1 ECD presented by dendritic cells, and that also homed to Her1-expressing tumours. Protein boosting further increased the CD8+ T cell response and generated anti-Her1 antibodies; in the antibody response, Her1 LV priming increased Th1-dependent immunoglobulin G2c production.

CONCLUSIONS

The ability of this vaccine protocol to break both T cell and B cell tolerance to a self-antigen likely explains its effectiveness.

HER1-ECD vaccination dispenses with emulsification to elicit HER1-specific anti-proliferative effects

EGFR (HER1) highlights as one of the most relevant tumor associated antigen in epithelial malignant cells. Monoclonal antibodies and tyrosine kinase inhibitors against EGFR remain as the most advanced approaches in clinical trials. More recently, an active immunotherapy using the HER1 extracellular domain (ECD) adjuvated in very small size proteoliposomes (VSSP) and emulsified in Montanide ISA-51 demonstrated its strength to inhibit tumor cell line proliferation by arresting cells in G(0)/G(1) stage and induction of apoptosis. In this study, we present a simpler HER1-ECD-based formulation, which is lacking the oily component Montanide ISA-51. Generated antibodies following non-emulsive formulation immunization recognized membrane EGFR; avoid EGF and TGFalpha coupling to EGFR leading to a marked abrogation of EGFR phosphorylation levels. Non-emulsive formulation also arrests cell cycle in G(0)/G(1) stage, demonstrating it preserves previous formulation quality in a newer and simpler formulation.

Active antimetastatic immunotherapy in Lewis lung carcinoma with self EGFR extracellular domain protein in VSSP adjuvant

The epidermal growth factor receptor (EGFR) plays a central role in regulating neoplastic processes. The EGFR overexpression in many human epithelial tumors has been correlated with disease progression and bad prognosis. Passive EGFR-directed immunotherapy, but not active specific approaches, has already been introduced in medical oncology practice. Then we wonder if mice immunization with the extracellular domain of murine EGFR (mEGFR-ECD) in adjuvants can circumvent tolerance to self EGFR, by inducing an immune response with consequent antitumor effect. The present study demonstrated that despite mEGFR expression in thymus, strong DTH response was induced by inoculation of mice with the mEGFR-ECD. This self-immunization, using both CFA and very small sized proteoliposomes from Neisseria meningitidis (VSSP), promoted highly specific IgG titers, predominantly IgG2a and IgG2b. Sera from mice immunized with mEGFR-ECD/VSSP not only recognized EGFR+ tumor cell lines by FACS, but also inhibited their in vitro growth, even in the absence of complement. Noteworthy, vaccination of mice with mEGFR-ECD/VSSP stimulated a potent antimetastatic effect in the EGFR+ Lewis lung carcinoma model, while reproduction-associated side effects were absent. Curiously, mice immunized with the human EGFR-ECD (Her1-ECD) in VSSP though induced highly specific IgG antibodies with strong in vitro cytotoxic effect over EGFR+ human cell lines, showed low cross-reactivity with the mEGFR-ECD. These results further encouraged the development of the Her1-ECD/VSSP vaccine project for patients with EGFR+ tumors.