Structural analysis of β-prism lectin from Colocasia esculenta (L.) S chott

Lectins of the Araceae family: Insights, distinctions, and future avenues-A three-decade investigation

The Araceae family boasts >3000 species of flowering plants that thrive across the tropics. Among the focal points of study within this family are lectins, proteins with affinity for binding carbohydrates. This review endeavors to gather data gleaned from numerous studies conducted over the past three decades on lectins extracted from Araceae plants. Our examination spans their extraction and purification methods, their specific interactions with carbohydrates, their molecular structures, and various physicochemical characteristics. Furthermore, we investigated the biological activities of these lectins and investigated the outcomes of cloning their genes. Despite their apparent similarities, these lectins exhibit notable distinctions, particularly regarding their unique preferences in interacting with erythrocytes from animals and humans, their sugar affinities, the critical amino acids for their functionality, the molecular weights of their subunits and their respective topologies, and ultimately, their dimerization and 3D β-prism-II structure, which reportedly diverge from those observed in other GNA-related lectins. These discrepancies not only deepen our understanding of monocot lectins but also render these proteins inherently captivating. This review marks the inaugural attempt at consolidating almost all published reports on lectins from the Araceae family, with the aim of furnishing glycobiology scientists with essential insights into potential laboratory challenges, the characteristics of these lectins, and avenues for future research.

Investigations on the Biological Activity of Allium sativum Agglutinin (ASA) Isolated from Garlic

Background:

Garlic (Allium sativum) from the family Amaryllidaceae is widely used in culinary and is reported to have potential anticancer, anti-diabetic, antimicrobial, and cardioprotective activities. Allium sativum agglutinin (ASA) is a bulb-type lectin (BTL) domaincontaining lectin isolated from garlic and has been studied for its various biological functions. Previous studies have reported the anti-cancer effects of ASA on histiocytic lymphoma (U937), promyelocytic leukemia (HL60), and oral cancer (KB).

Methods:

In this study, we have purified and characterized ASA and evaluated it for its anticancer effects on other cancer cell lines. MTT assay and FACS analysis was done to corroborate the anticancer findings against cervical (HeLa) and lung cancer (A549) cell lines.

Results:

IC50 value of 37 μg/ml in HeLa and a weak activity (26.4 ± 1.9% cellular inhibition at 100μg/ml treatment) in A549 were found in the MTT assay. FACS analysis further corroborated these findings and showed the apoptotic effects of ASA in these cell lines.

Conclusion:

Anticancer activity for members of bulb-type lectin (BTL) domain-containing lectins has been widely reported, and we hope that our study forms a basis for the development of ASA as a therapeutic agent.

An Extract of Taro (Colocasia esculenta) Mediates Potent Inhibitory Actions on Metastatic and Cancer Stem Cells by Tumor Cell-Autonomous and Immune-Dependent Mechanisms

The taro plant, Colocasia esculenta, contains bioactive proteins with potential as cancer therapeutics. Several groups have reported anti-cancer activity in vitro and in vivo of taro-derived extracts (TEs). We reported that TE inhibits metastasis in a syngeneic murine model of Triple-Negative Breast Cancer (TNBC).

Purpose

We sought to confirm our earlier studies in additional models and to identify novel mechanisms by which efficacy is achieved.

Methods

We employed a panel of murine and human breast and ovarian cancer cell lines to determine the effect of TE on tumor cell viability, migration, and the ability to support cancer stem cells. Two syngeneic models of TNBC were employed to confirm our earlier report that TE potently inhibits metastasis. Cancer stem cell assays were employed to determine the ability of TE to inhibit tumorsphere-forming ability and to inhibit aldehyde dehydrogenase activity. To determine if host immunity contributes to the mechanism of metastasis inhibition, efficacy was assessed in immune-compromised mice.

Results

We demonstrate that viability of some, but not all cell lines is inhibited by TE. Likewise, tumor cell migration is inhibited by TE. Using 2 immune competent, syngeneic models of TNBC, we confirm our earlier findings that tumor metastasis is potently inhibited by TE. We also demonstrate, for the first time, that TE directly inhibits breast cancer stem cells. Administration of TE to mice elicits expansion of several spleen cell populations but it was not known if host immune cells contribute to the mechanism by which TE inhibits tumor cell dissemination. In novel findings, we now show that the ability of TE to inhibit metastasis relies on immune T-cell-dependent, but not B cell or Natural Killer (NK)-cell-dependent mechanisms. Thus, both tumor cell-autonomous and host immune factors contribute to the mechanisms underlying TE efficacy. Our long-term goal is to evaluate TE efficacy in clinical trials. Most of our past studies as well as many of the results reported in this report were carried out using an isolation protocol described earlier (TE). In preparation for a near future clinical trial, we have now developed a strategy to isolate an enriched taro fraction, TE-method 2, (TE-M2) as well as a more purified subfraction (TE-M2F1) which can be scaled up under Good Manufacturing Practice (GMP) conditions for evaluation in human subjects. We demonstrate that TE-M2 and TE-M2F1 retain the anti-metastatic properties of TE.

Conclusions

These studies provide further support for the continued examination of biologically active components of Colocasia esculenta as potential new therapeutic entities and identify a method to isolate sufficient quantities under GMP conditions to conduct early phase clinical studies.

Crocetin and Crocin from Saffron in Cancer Chemotherapy and Chemoprevention

INTRODUCTION

Cancer is a disorder which has a powerful impact on the quality life and life expectancy despite the increase in drugs and treatments available for cancer patients. Moreover, many new therapeutic options are known to have adverse reactions without any improvement in outcome than before. Nowadays, natural products or plant derivatives are used as chemoprevention drugs and chemotherapy is the new approach that uses specific cell premalignant transformation in the malignant form. Natural substances derived from plants, such as polyphenols, flavonoids, carotenoids, alkaloids and others, can be biologically active and have a wide spectrum of effects. The protective effects of Saffron carotenoids (crocin and crocetin) have been extensively studied mainly for their antioxidant properties, however, they have various other biological activities including tumor growth inhibition with the induction of cell death.

METHODS

The relevant information on Saffron and its carotenoids was collected from scientific databases (such as PubMed, Web of Science, Science Direct). To identify all published articles in relation to saffron, crocin and crocetin, in different types of cancer, no language restriction has been used.

RESULTS

To date, crossing the words saffron and cancer, approximately 150 articles can be found. If crossing is made between crocin and cancer, approximately 60 articles can be found. With the crossing between crocetin and cancer, the number is approximately 55, while between carotenoids and cancer, the number exceeds 16.000 reports. In all the papers published to date, there are evidences that saffron and its carotenoids exert chemopreventive activity through anti-oxidant activity, cancer cells apoptosis, inhibition of cell proliferation, enhancement of cell differentiation, modulation of cell cycle progression and cell growth, modulation of tumor metabolism, stimulation of cell-to-cell communication and immune modulation.

CONCLUSION

Here, we have tried to offer an up-to-date overview of pre-clinical experimental investigations on the potential use of the main carotenoids of saffron in tumor models and focus the attention on the molecular mechanisms involved.

Tarin, a Potential Immunomodulator and COX-Inhibitor Lectin Found in Taro (Colocasia esculenta)

Taro (Colocasia esculenta) corm is a rustic staple food, rich in small starch granules, fibers, and bioactive phytoconstituents such as flavonoids, alkaloids, sterols, tannins, phytates, micronutrients, and proteins, including tarin, a GNA-related lectin. Tarin exhibits recognized biocide activities against viruses and insects, has antitumoral properties and is an immunomodulator molecule candidate. It has been isolated in highly purified form (>90%) from taro corms through low-cost and single-step affinity chromatography. It comprises 2-domain 27 to 28 kDa protomer, posttranslational cleaved into 2 nonidentical monomers, 11.9 and 12.6 kDa, held by noncovalent binding. At least 10 tarin isoforms sharing over 70% similarity have been described. The monomers assume the β-prism II fold, consisting of 3 antiparallel β-sheets formed by 4 β-strands each. Tarin exhibits an expanded-binding site for complex and high-mannose N-glycan chains 49, 212, 213, 358, 465, and 477 found on cell surface antigens of viruses, insects, cancer, and hematopoietic cells, explaining its broad biological activities. Tarin may stimulate innate and adaptive immune responses, enabling hosts to recover from infections or immunosuppressed status inherent to several pathological conditions. In a murine model, tarin stimulates the in vitro and in vivo proliferation of total spleen and bone marrow cells, especially B lymphocytes. Granulocyte repopulation has also been demonstrated in long-term mice bone marrow cell cultures. As a potential immunomodulator, tarin, administered to immunosuppressed mice, attenuated cyclophosphamide-induced leukopenia. We propose a molecular model that unites the potential prophylactic and therapeutic action of tarin on hematopoietic and cancer cells, as a potential immunomodulator.

Typhonium giganteum Lectin Exerts A Pro-Inflammatory Effect on RAW 264.7 via ROS and The NF-κB Signaling Pathway

Typhonii rhizoma, a widely used herb in traditional Chinese medicine, has acute irritating toxicity related to Typhonium giganteum lectin (TGL). TGL exhibits acute inflammatory effects, but the underlying molecular mechanisms are largely unknown. This paper is designed to assess the pro-inflammatory response of TGL on RAW 264.7 cells. RAW 264.7 treated with 6.25, 12.5, 25, and 50 µg/mL TGL showed elevated levels of inflammatory factors (TNF-α, IL-1β) and of p-IκB and p-p65, all dose-dependent, indicating that TGL had a substantial inflammatory effect and mobilized the nuclear factor-κB (NF-κB) pathway. All four TGL treatments also induced the up-regulation of reactive oxygen species (ROS) and cytosolic free Ca²⁺ and down-regulation of mitochondrial membrane potential (MMP). The production of cytokines and p-IκB, p-p65 were reduced by N-acetylcysteine (NAC), an ROS scavenger, which somewhat abrogated ROS production. The results showed the TGL-activated inflammatory signaling pathway NF-κB to be associated with the overproduction of ROS. Moreover, 50 μg/mL treatment with TGL led to cell apoptosis after 1 h and increased necrosis over time. These results provided potential molecular mechanisms for the observed inflammatory response to TGL including up-regulation of ROS and cytosolic free Ca²⁺, down-regulation of MMP, the mobilization of the NF-κB pathway, and the subsequent overproduction of pro-inflammatory factors resulting in apoptosis. Long-term stimulation with TGL resulted in strong toxic effects related to inflammation that induced necrosis in macrophages.