*Article* **Anticancer Activity of Mannose-Specific Lectin, BPL2, from Marine Green Alga** *Bryopsis plumosa*

**Jei Ha Lee, Set Byul Lee, Heabin Kim, Jae Min Shin, Moongeun Yoon, Hye Suck An and Jong Won Han \***

Department of Genetic Resources, National Marine Biodiversity Institute of Korea, Seocheon-gun 33662, Repulic of Korea

**\*** Correspondence: jwhan@mabik.re.kr; Tel.: +82-419500913

**Abstract:** Lectin is a carbohydrate-binding protein that recognizes specific cells by binding to cellsurface polysaccharides. Tumor cells generally show various glycosylation patterns, making them distinguishable from non-cancerous cells. Consequently, lectin has been suggested as a good anticancer agent. Herein, the anticancer activity of *Bryopsis plumosa* lectins (BPL1, BPL2, and BPL3) was screened and tested against lung cancer cell lines (A549, H460, and H1299). BPL2 showed high anticancer activity compared to BPL1 and BPL3. Cell viability was dependent on BPL2 concentration and incubation time. The IC50 value for lung cancer cells was 50 μg/mL after 24 h of incubation in BPL2 containing medium; however, BPL2 (50 μg/mL) showed weak toxicity in non-cancerous cells (MRC5). BPL2 affected cancer cell growth while non-cancerous cells were less affected. Further, BPL2 (20 μg/mL) inhibited cancer cell invasion and migration (rates were <20%). BPL2 induced the downregulation of epithelial-to-mesenchymal transition-related genes (Zeb1, vimentin, and Twist). Co-treatment with BPL2 and gefitinib (10 μg/mL and 10 μM, respectively) showed a synergistic effect compared with monotherapy. BPL2 or gefitinib monotherapy resulted in approximately 90% and 70% cell viability, respectively, with concomitant treatment showing 40% cell viability. Overall, BPL2 can be considered a good candidate for development into an anticancer agent.

**Keywords:** mannose-binding lectin; BPL2; *Bryopsis plumosa*; anticancer; lung cancer

#### **1. Introduction**

Lectin is a carbohydrate-binding protein that can agglutinate erythrocytes and cells by specifically binding to carbohydrate moieties on cells [1]. Owing to its carbohydratebinding properties, it is often suggested for pharmacological applications such as antiviral, antimicrobial, and anticancer therapeutics [2–4].

Cancer has high death rates when compared to other human diseases, with over a million people globally newly diagnosed with the condition every year [5]. Although many researchers and countries have invested in anticancer agents, it remains an intractable disease.

Anticancer agents are most commonly developed from antibodies (based on the human immune system) [6], natural products (primarily secondary metabolites) [7], and proteins or peptides [8]. Chemotherapy is the most commonly used anti-cancer approach; however, it has some limitations, such as toxicity [9].

Tumor cells have shown various glycosylation patterns as a common feature, making them distinguishable from non-cancerous cells. Cellular glycosylation mechanisms are associated with physiological and pathological functions [10]. The alteration of glycans on the cancer cell surface affects the invasion and migration of cancer cells. Glycan is also involved in signal transduction, cell adhesion, and cell-substrate interactions [11]. Owing to this, biomarkers for diagnosis have been developed based on the glycosylation pattern of tumor cells [12].

Lectin can recognize tumor cells by binding to cell surface-altered carbohydrates [13]. Therefore, some lectins have been studied as diagnostic agents against tumor cells. Because

**Citation:** Lee, J.H.; Lee, S.B.; Kim, H.; Shin, J.M.; Yoon, M.; An, H.S.; Han, J.W. Anticancer Activity of Mannose-Specific Lectin, BPL2, from Marine Green Alga *Bryopsis plumosa*. *Mar. Drugs* **2022**, *20*, 776. https:// doi.org/10.3390/md20120776

Academic Editors: Barbara De Filippis, Alessandra Ammazzalorso and Marialuigia Fantacuzzi

Received: 6 November 2022 Accepted: 7 December 2022 Published: 13 December 2022

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**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

lectins are also regulators of inflammation and the immune response toward tumor cells [10], they have been investigated as anticancer agents [14]. Lectin is a well-known protein that can inhibit tumor growth and induce cancer cell death. In the last several decades, several lectins with anticancer activities have been reported (e.g., ConA) [15]. Mistletoe (*Viscum album*) lectin is a well-known lectin that is effective against various neoplastic cells [16]. It induces apoptosis in colorectal cancer cells [17]. Moreover, RCA-I specifically binds to metastasis-associated cell surface glycans and inhibits cell invasion and migration [18].

Many marine algal lectins have been reported to be novel proteins. They are believed to have a unique feature compared with other lectins because marine algae have different carbohydrate complexes [19]. To date, various lectin or hemagglutination activities have been reported from the marine algal group [3,20], with various biomedical applications being proposed [21].

*Bryopsis plumosa* is a well-known coenocyte marine green alga containing abundant lectins involved in algal cell regeneration [22]. To date, *Bryopsis plumosa* lectins (BPLs), which specifically bind to different carbohydrates, have been reported. BPL1, 3, and 4 bind to GlcNAc and GalNAc, while BPL2 binds to D-mannose [22–25]. All *Bryopsis plumosa* lectins in literature were purified, and their amino acid sequences were determined. To date, the potential anticancer effect of *Bryopsis plumosa* lectin has been suggested [25]; however, few studies confirming this postulation have been reported.

In this study, the anticancer activity of BPLs (BPL1, 2, and 3) against lung cancer cell lines and their regulation of epithelial-to-mesenchymal transition (EMT) pathway-related genes were demonstrated.
