Lectins as a promising therapeutic agent for breast cancer: A review

Based on tumor type:

Based on hormone receptor status:

Based on HER2 status:

Luminal A: The PAM50 classifier identifies the Luminal A subtype, which is linked to a more favorable prognosis in comparison to other subtypes. The luminal A subtype is defined by the expression of hormone receptors, specifically estrogen receptor (ER) and progesterone receptor (PR), as well as low levels of human epidermal growth factor receptor 2 (HER2) [30]. Individuals with Luminal A tumors typically experience slower tumor growth and have a greater probability of responding positively to hormonal treatments like tamoxifen or aromatase inhibitors [31]. Nonetheless, it is important to note that not all Luminal A tumors exhibit identical clinical characteristics, and when determining treatment options, additional factors such as tumor size, lymph node involvement, and histological grade should also be taken into consideration. The primary components of treatment for luminal A breast cancer encompass surgery, radiation therapy, hormonal therapy, and targeted therapy [32].

Luminal B: The PAM50 classifier identifies the Luminal B subtype, characterized by the overexpression of genes associated with cell proliferation and hormone signaling pathways. Luminal B tumors typically have a higher proliferation rate compared to other luminal subtypes and are associated with a poorer prognosis [33]. Therefore, patients with luminal B breast cancer may benefit from more aggressive treatment strategies, such as chemotherapy, in addition to hormone therapy. This is because luminal B tumors have a higher risk of recurrence and are less responsive to hormone therapy alone [34].

HER-2 enriched: The PAM50 classification system identifies the HER-2 enriched subtype by assessing the expression patterns of genes associated with HER-2 amplification and activation, rendering it a valuable tool for molecular categorization [30]. This classification assists in the identification of individuals who may benefit from precision therapies and provides significant insights into the fundamental biology of HER-2 positive breast cancer. The HER-2 enriched subtype is characterized by the overexpression of the human epidermal growth factor receptor 2 (HER-2) gene [35]. Breast cancers with HER-2 positivity tend to be more aggressive and carry a higher risk of recurrence in comparison to other subtypes. However, the introduction of targeted treatments such as trastuzumab (Herceptin) has notably improved outcomes for patients with HER-2 positive breast cancer [36].

Basal-like: The basal-like subtype, commonly known as triple-negative breast cancer (TNBC) because it lacks the expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2), is associated with an elevated risk of recurrence and metastasis. The PAM50 basal-like molecular classification not only provides insights into the biology of basal-like breast cancer but also has implications for personalized medicine. It helps identify patients who are more likely to benefit from individualized treatments such as chemotherapy or targeted therapies [37].

Genetic clustering: The evidence of genetic clustering dates to 100AD in the medical scriptures of Rome [39]. It has been suggested, after taking into consideration various medical evidence, that a woman’s chance of getting breast cancer increases when she has a first-degree relative who has a history of breast cancer. This probability of occurrence of the disease increases more when two first-degree relatives show involvement with breast cancer. The risk was known to be higher when the occurrence of cancer was before menopause and the disease was bilateral [39,40]. It has also been identified can be transmitted through both maternal and paternal lines in an autosomal dominant pattern. Not much has been further studied to understand the pattern, Usually, the risk associated with cancer is related to the maternal line, but the paternal line inheritance is known to elevate it [41].

Intrinsic factors: A womans age at which the integral processes took place has also known to affect the occurrence of breast cancer [42]. Chances of getting breast cancer are known to increase if a woman has an early menarche, has never given birth, gave birth to a child after entering her 30s, or got her menopause late [43]. In all these cases, the breast tissues will be exposed to estrogen for a longer time, thus increasing the risk [44].

Obesity: Many studies have shown that obesity contributes to the occurrence of breast cancer. In the case of obese people, the formation of 2-OH estrogenic compound is much less that causing an increase in the effect of estrogen [45]. It has also been stated that the people who have high-fat consumption and obesity have reduced amounts of globulins (sex hormone-binding globulin (SHBG) Corticosteroid-binding globulin (CBG)) to which the sex hormones bind resulting in a higher amount of sex hormones circulating freely thus highly available to exert their effect on tissues of the breasts [46].

Radiation: Breasts are very sensitive organs to any kind of stimuli. The high sensitivity of breast tissue to radiation is because of its numerous dividing cells and high metabolic rate. It is crucial to grasp the impact of radiation on breast tissue and the potential risks it poses. Thus, exposing breasts to radiation for a longer period and or to a higher frequency can be damaging to them and can result in mutations which can ultimately increase the risk of breast cancer [47].

Contraceptives: They are known to contain synthetic forms of hormones of a female. Estrogen and progesterone act as promotors of the growth of cancer cells. Consuming birth control pills, causes increased exposure to hormones in the body thus increasing the risk of breast cancer [48].

Dietary factors: Although the relationship between diet and the incidence of breast cancer is not well understood it has been identified that consumption of higher amounts of fat increases the risk of breast cancer [49]. Also, the people who consume a good amount of omega-3 i.e., ∼1.1g per day for adult females and ∼1.6g for adult males have a lower risk of getting the disease [50,51]. Consumption of reduced carotene and fibers has been shown to increase the chances of occurrence of cancer [52].

Chemotherapy: Certain anti-cancer agents such as cyclophosphamide, methotrexate, 5-fluorouracil, vinorelbine, and doxorubicin are used to treat breast cancer [53]. They may be used to cure the cancer using combination therapy or to suppress the symptoms (depending on the case). Along with the therapeutic effects chemotherapeutics agents also exhibit adverse side effects like immunosuppression, myelosuppression, neutropenic enterocolitis, diarrhea, anemia, vomiting, nausea, loss of hair, and in some cases, development of secondary neoplasm. [54–61]

Immunotherapy: This therapy is employed to make our immune system strong enough to fight cancer [62]. Immunotherapy can cause some side effects like it can cause Immune-Related Adverse Events (irAEs) [63], Cytokine Release syndrome [64], and allergic reactions [65]

Surgery: The part where the cancer cells proliferate is removed from the body [66]. It can cause side effects like pain, swelling and bruising, scarring, infection, bleeding, nerve damage, impaired function, lymphedema, digestive problems, respiratory issues, blood clots, adverse reactions to anesthesia and delayed healing [67].

Stem cell transplant: The stem cells are taken from the matching donor; the stem cell converts into blood cells and replaces the blood cells that were lost due to radiation or chemotherapy [68]. Some side effects of this are Graft-Versus-Host Disease (GVHD), infection, organ damage, bone health, and gonadal dysfunction [69].

Radiation therapy: The size of the tumor shrinks and the tumor cells are killed due to the high dose of radiation in this therapy [70]. Some of the side effects of radiation therapy are mucositis, xerostomia, dermatitis, fatigue, and osteoradionecrosis [71].

Hormone therapy: Some cancers such as prostate cancer and breast cancer require hormones to grow, this therapy either stops the tumor growth or slows it down [72]. The side effects are hot flashes, loss of libido, breast tenderness or growth, decreased muscle mass, weight gain, memory and cognitive changes, and increased risk of cardiovascular disease [73].

Photodynamic therapy: Drugs which are sensitive to light and gets activated by them to kill the tumor cells [74]. Some of the side effects of Photodynamic therapy are Skin Sensitivity and sunburn, pain or discomfort, swelling and inflammation, hypersensitivity reactions, and pain or discomfort during light exposure [75].

Hyperthermia treatment: In this treatment the body tissue that has cancer is heated up to 45 degree celcius to kill the tumor cells without effecting the function of normal cells present in the tissue [76]. Side effects of this treatment are redness, blistering, or burns, pain and discomfort, nausea and vomiting, dehydration, blood pressure changes and muscle or joint pain [77]

Targeted cell therapy: In this, the changes in the tumor cells that help them to proliferate and mature are targeted [78]. Side effects of this treatment are hair loss (alopecia), nail changes, including nail dystrophy, paronychia, or onycholysis, skin discoloration, and Hand-Foot Skin Reaction (HFSR) [79].

Cryoablation- The tumor cell tissue is frozen with the help of the gas and then the tissue is thawed, this step is done multiple times to kill the tumor cells [80]. Some of the side effects of this treatment are urinary symptoms, erectile dysfunction, pain or discomfort, and swelling and bruising [81].

Ubiquitination: An important post-translational modification which helps in maintaining the activity of protein. In this process, ubiquitin molecules are attached to amino acids like lysine and degrade the damaged protein molecules. So, it also helps in clearing the accumulated protein debris [86]. Dysregulation in ubiquitination plays a significant role in promoting breast cancer by regulating the function of oncogenic proteins. One such example is the oncogenic protein c-Myc (also known as cellular myc), which can be ubiquitinated at specific lysine sites. This ubiquitination process increases c-Myc’s stability and activity, resulting in elevated c-Myc levels observed in various cancer types, including breast cancer. This increase in c-Myc levels is associated with enhanced cell proliferation, angiogenesis, and tumor development. Similarly, the oncogenic protein HER2 also undergoes ubiquitination, which can enhance its activity and contribute to the growth of cancerous tumors [83].

Phosphorylation: It is the process in which a phosphate group is added to a protein molecule to change its structure and function with the help of enzyme kinase. It is a reversible modification and usually occurs in amino acids like serine, threonine, and tyrosine. This process is very crucial in signaling pathways to activate or deactivate the cascade. Likewise, the phosphatase enzyme is responsible for removing the phosphate group (i.e., dephosphorylation). In almost 30% of the cells phosphorylation occurs, so, any mutation in a protein phosphate site can lead to cancer and other diseases [87,88]. Many signaling pathways like PI3K/AKT/mTOR pathway, and tyrosine kinase pathway which play an important role in maintaining the cell cycle need the phosphorylation process [89]. In cancer cells these pathways are unregulated and faults in the phosphorylation process are a reason for it. The progression and inhibition of breast cancer are significantly related to the phosphorylation of upstream and downstream regulatory factors of nitric oxide (NO) [90].

Acetylation: Acetylation is the process in which the acetyl group is added to the amino acid residues. Histone acetylation is one of the most crucial processes that occur in a cell. Acetyl, with the help of the acetyltransferase enzyme gets attached to the lysine residue present in the histone (binding protein) and gives a positive charge to the molecule. The electrostatic force between the positively charged histone and negatively charged DNA helps in loosening up the chromatin providing easier access for the DNA repair process to occur. Acetylation dysregulation can cause cancer because of a disrupted DNA repair process which can lead to the accumulation of damaged DNA and leading to genomic instability and over time it can progress into cancer. Recent studies have shown that the use of histone deacetylase (HDAC) can help in the re-expression of Estrogen receptors in Triple negative breast cancer in which there is an absence or low level of ER due to gene alteration [91]. With the help of this theory, the TNBC patient can be treated with hormonal therapy by re-expressing estrogen receptors.

Glycosylation: Glycosylation is a major co- & post-translational modification of proteins that is primarily catalyzed by glycosyltransferases. It is important as it leads to protein folding by acting as molecular chaperones and preventing faulty protein folding and degradation. Glycan protein also helps in transferring the protein molecules through the cell membrane and to their destined location where they are needed- sorting of protein [92]. Glycan protein attached to receptors present on the cell surface helps in more specific binding of ligands. Protein glycosylation changes alter the roles of proteins involved in cell-cell interactions that lead to tumor cell dissemination & local invasion, immune response regulation, and growth regulation in a variety of organ niches. In drug sensitivity cases, the role of glycoproteins is very prominent as the altered glycosylation of the ATP binding cassette transport proteins has been linked to drug-resistant tumor cells shown by many patients of TNBC who suffered a short relapse due to ineffective chemotherapy [93].

Glycosylation is altered during the progression and metastasis of breast cancer. Previous research into the relationship between both the malignant behavior of TNBC cells & glycosylation yielded some intriguing results. According to Zhou and colleagues [94], bindings of the RCA-I (Ricinus communis agglutinin I) to TNBC cell lines were found to correlate with their ability to metastasize, as well as RCA-I inhibited many processes in TNBC cells like cell adhesion, cell migration and invasion with high metastatic capacity. The mechanism of RCA-I lectin in the inhibition of cell adhesion, metastasis and invasion is not fully understood. Although it has been speculated by Zhou and colleagues that RCA-I inhibits the motility of TNBC cells by blocking the metastasis- associated surface glycans. It is worth noting that the majority of previous studies on this topic were conducted in vitro.

During glycosylation, sugars are enzymatically attached to specific amino acid residues in the protein sequence. The sugar moieties can be attached to the protein either through N-linked glycosylation, where the sugar is linked to the nitrogen atom of an asparagine residue, or through O-linked glycosylation, where the sugar is linked to the oxygen atom of a serine or threonine residue [95].

Breast cancer is a complex disease characterized by the uncontrolled proliferation of cells in breast tissue. Alterations in glycosylation have been identified as associated with breast cancer progression and metastasis, influencing multiple aspects of tumor biology [96].

Lectins can bind to the carbohydrate moiety which is present in the form of glycoprotein and glycolipids on the cell surface. As we know, altered glycosylation of the protein molecules (e.g., receptors) present on the cancer cell surface leads to cancer cell adhesion to extracellular matrix (ECM) or avoids immune responses through alteration of the stability of ligands of immune checkpoint receptors which results in cancer progression [97]. So, understanding the binding of lectins with different glycoproteins can help in treating cancer.

Some lectins like SNA and MAA have been found to identify the glycoproteins which are present in the breast cancer cells and agglutinate them by forming linkage with the sialic acid (that is the part of glycoprotein on the cancer cell surface) (Fig. 2) [98,99]. Sialic acid is overexpressed (hyper sialylation) in the tumor tissues in ovarian cancer, breast cancer, colorectal cancer, and leukemia in comparison to normal cells of these organs [100,101]. So, if there are natural compounds that can attach themselves to sialic acid and precipitate the glycoconjugates then this phenomenon can be used in targeting cancer cells. Lectins are not only able to detect cancer cells but also show anti-tumor effect (Table 1).

Assisting in signaling for proliferation: Cancer cells can multiply enormously, and it has been identified that glycosylation plays an integral role in providing the essential signals required for uncontrolled division of cells [106]. The management of the proteins that have importance in cell cycle continuation like c-MYC (Cellular myelocytomatosis oncogene) is known to be controlled by the modification of O-GlcNAc [98]. When there is an increase in the expression of modified c-MYC, it can affect the phosphorylation process stabilizing the modified protein [107]. Various growth factors like EGFR (epidermal growth factor receptor), and PDGF (platelet-derived growth factor) have also been identified that are managed by N- glycan modifications. Thus, glycosylation also controls signaling for growth factors [98].

ECM acts as an interface that contains various non- cellular components that support the various growth-related signaling processes that are taking place in the nearby cells. [108]. The modification of CD44 and regulation of growth factors dependent on integrin are also attributed to the glycosylation process that results in uncontrolled cell growth [109,110].

Escaping suppression of growth: The two of the most important tumor suppressors, p53 and retinoblastoma are also known to contain regions for glycosylation modification of O-GlcNAc or phosphorylation that is suspected to turn on their oncogenic activity resulting in the production and promotion of cancer cells [105].

Reducing cell energy processes: Cancer cells are known to exhibit the Warburg effect wherein; the cells shift their metabolic processes from oxidative phosphorylation to aerobic glycolysis [118]. As Cancer cells need to multiply rapidly and they need to have an increased metabolism and high energy production, this shifting is identified by a high glucose release, thus providing cancer cells with what they need. With the processes like hexosamine biosynthetic pathway, the high amount of glucose present causes an increased glycolysis and flux. The end product of this pathway is UDP-GlcNAc, an essential metabolite for the O-GlcNAc in both N and O liked modifications [120]. O-GlcNAc is identified as a “nutritional sensor” that helps regulate the nutrition processes and is capable of altering different metabolic enzymes, hence resulting in changes in metabolism [119].

Helping cells to escape death: Under normal circumstances, cells are prevented from multiplying uncontrollably through apoptosis [126]. The intercellular signaling pathways to control the process of apoptosis are significantly regulated by glycans [127]. With the help of glycosylation glycans present on the apoptosis, receptors can be altered to become resistant to cell death signals [127]. Below are a few examples of how glycosylation helps in the regulation of apoptosis:

Activation of immortality in cells-Normally the cells undergo senescence that happens due to the shortening of telomeres, but cancer cells can escape the senescence [133]. This happens due to the transcriptional reactivation of the human telomerase reverse transcriptase(hTERT). To date the direct effect of glycosylation in the activation if the telomerase has not been identified but it is thought that glycosylation has an indirect effect on the telomerase through c-MYC. The activation of telomerase is known to be mediated by c-MYC which is known to activate the hTERT gene [135]. As the c-MYC gets glycosylated and is modified, the telomerase activation is also induced through O-GlcNAc modification which has frequently been observed in many cases of cancer [134].

Okra lectin: Abelmoschus esculentus, popularly known as okra is a member of Malvaceae, first originated in Africa. It is mostly used as a food source but also has a significant role in traditional medicines for dysentery, urinary infections, constipation, and many more disorders [137]. Although the medicinal properties of the okra fruit have been known for a while, it is only a recent discovery that lectins were isolated from the seeds of this plant and not much has been studied about this lectin. This lectin affects the cell proliferation of breast cancer cells by inhibiting it (up to 63%). It also increases the expression of pro-caspase-9 and pro-caspase-3 proteins both of which are important in the intrinsic or mitochondrial pathway of apoptosis of cells. Also, it is known to increase the BAX/BCL-2 ratio which also plays a significant role in the apoptosis process [138].

Thus, the effect that is produced by the lectin isolated from okra is due to inhibition of cell growth and apoptosis.

Helilectin-3: The cancer treatment is significant when it acts on the cancer cells and at the same time does not cause any effect on the normal cells. This is what is the mode of action of this lectin which is isolated from a marine sponge called Haliclona caerulea [139]. It is seen that this lectin on its first encounter with the cancer cells has been known to reduce the viability of cells and not produce any effect on normal and healthy cells. When this lectin is allowed to be incubated with the cancer cells for more than 24 hours, it causes an arrest in the cell cycle at the G1 phase. Further, there is a remarkable increase in the expression of caspase-9 protein which is an important part of the intrinsic or mitochondrial pathway of apoptosis of the cell. Helilectin-3 has a negative effect on the adhesiveness of the breast cancer cells which is important for cell proliferation and their survival in the body. It is known to impair the adhesion capability of the cancer cells. This lectin is also known to cause autophagic death of the cancer cell due to the increased expression of microtubule-associated protein light chain 3(LC3) with an observable conversion of LC3-I to membrane-bound LC3-II which is an autophagic death marker [140].

Thus, the effect produced by helilectin-3 on breast cancer cells is due to contribution of both apoptotic and autophagic death.

Sclerotium rolfsiilectin:Sclerotium rolfsii lectin (SRL) is obtained from a pathogenic fungal source. SRL has been found to recognize and specifically bind oncofetal Thomsen-Friedenreich (Galβ1-3GalNAc-O-ser/thr, or TF) related O-linked glycan on the tumor cell surface [141]. For the betterment of cancer patients, research has been going on to find an alternative mode of action for treatment than chemotherapy and chemoprevention. In this regard, SRL has shown many properties that can be useful in combating tumor cells [142]. In many cancer therapies, we observe that along with tumor cell destruction, some normal cells are also affected which might be detrimental to the patients body. Surprisingly SRL was found to have a more apoptotic effect on the tumor cells of benign and metastatic cancer rather than the normal mammary cells. So SRL can be used in the targeted therapy, and it is obtained from a natural source can decrease the side effects of the treatment on the body [143]. It is to be noted that although some of the chemotherapy drugs are also obtained from natural sources it is still more toxic than SRL. It is because of pharmacokinetics i.e. These medications are typically given systemically, either through oral ingestion or intravenous delivery, enabling them to travel throughout the body. This broad dissemination enhances the chances of them coming into contact with normal cells and tissues. These drugs’ therapeutic index is also very narrow so even a slight accumulation of these drugs can cause lethal effects on the body. And SRL with its highly specific nature will not cause this issue thereby decreasing its toxicity level [144].

In recent studies, it has been found that SRL was inhibiting the neo-angiogenesis which will prevent cancer cells from getting sufficient nutrients for their growth, resulting in a decrease of tumor cell proliferation. After performing an adhesion assay, it was found that SRL has adhesive property that is it has significantly decreased the adhesion of tumor cells to fibronectin and collagen of ECM [145].

On a mice model that had MCF-7xenografts, SRL efficacy was observed. It was found that SRL was inhibiting tumor proliferation [142].

Helix pomatia: Helix pomatia agglutinin (HPA) obtained from the Roman snails is part of the carbohydrate-binding protein family. It specifically binds to N- acetyl galactosamine (called GalNAc). Glycan arrays were done to find the lectin specificity of the compound so that its use as a cancer marker can be explored [145].

A study was done in which HPA and c-erbB-2 oncoprotein were used to diagnose the patient and try to make an appropriate future treatment plan. It was seen that the levels of HPA staining, and c-erb-2 expression were associated with the axillary lymph node metastasis in breast cancer patients. Their level was used to predict the incidence of axillary lymph node metastasis as well as the tumor size. This may help in generating a better treatment plan in patients who did not have the dissection of the axillary lymph node, the levels of HPA and c-erb-2 can be checked, and they can be put on aggressive therapy to prolong their survival rate [146].

MAA: The plant Maackia amurensis produces a lectin called Maackia amurensis agglutinin (MAA), which is found in its seeds. The possible involvement of MAA in the diagnosis, prognosis, and therapy of breast cancer has been investigated [147]. Compared to normal cells, breast cancer cells frequently have modifications to their glycosylation patterns. A kind of glycan, sialic acids, can change in expression or structure because of these modifications.

The agglutination test used by MAA particularly detects 2,3-linked sialic acid and aids in the identification and characterization of these glycan changes. Increased tumor aggressiveness and metastatic potential have been linked to the presence of 2,3-linked sialic acid glycans in breast cancer cells. Increased MAA agglutination reactivity has been linked in studies to a worse prognosis, which includes a greater tumor grade, lymph node involvement, and lower overall survival rates [148,149]. MAA has also been explored as a potential therapeutic tool in breast cancer treatment. But the research for this is still on going and not completely established.

Mistletoe Mistletoe species like Viscum album var. coloratum (Korean mistletoe) is one of the most significant medicinal plants in anthroposophical medicine and can treat cancer. Because of its few adverse effects and the fact that they are not life-threatening, mistletoe extract is advised for the treatment of cancer, particularly breast cancer [150]. There have been a few reports of allergic responses. Mistletoe extract was first used in oncology as a novel form of cancer treatment by Rudolf Steiner, the developer of the anthroposophical medical system, in 1920 [151].

Despite being one of the more debatable lectins when it comes to cancer treatment, extracts of lectins from mistletoe plant species have been extensively examined due to their vast efficiency on a range of neoplastic cells [152]. Numerous studies demonstrate that mistletoe lectins can either promote or inhibit apoptosis depending on their concentration [153,154]. After treatment with the lectin-containing mistletoe extracts ISCADOR, tumor growth in glioblastoma xenograft-bearing mice was inhibited, and genes associated with glioblastoma progression and malignancy, such as transforming growth factor- and matrix-metalloproteinases, displayed downregulation [155]. Mistletoe lectin I, II, and III make up the majority of mistletoe lectin extracts, while further research is needed to fully understand their variances [156].

Viscum album var. coloratum agglutinin (VCA), has been shown in tests to have beneficial effects on human breast cancer cells. The VCA lectin and doxorubicin (DOX) combination produced even more potent results for programmed cell death, but DOX’s therapeutic applications are constrained because of its hazardous side effects, which include cardiotoxicity and myelosuppression. The use of VCA and DOX together led to the stimulation of apoptosis-inducing proteins like Bax and Puma and the suppression of Bcl-2 [157].

In both SK-Hep-1 (p53-positive) and Hep 3B (p53-negative) human hepatocarcinoma cells, the Korean mistletoe lectin (Viscum album L. coloratum agglutinin) induced apoptosis through p53- and p21-independent pathways by downregulating Bcl-2 and telomerase and upregulating Bax acting upstream of caspase-3 [158].

C-type lectin-Lebectin: Lebectin is the C-type protein isolated from the venom of Macrovipera lebetina. C-type lectin-like proteins from the viper venom also known as the snaclecs do not have the sugar -calcium binding loops which are generally found in C-type lectin proteins [159]. Lebectin has 129 amino acids in the α subunit and 131 amino acids in the β subunit. Snaclecs are known to have anticancer effects [160]. Lebectin also shows the anti-aggregation activity on the platelets. In the MDA-MB-231, which is a cell line of triple-negative breast cancer that is the subtype of breast cancer, Lebectin blocks the cell migration in a dose-dependent manner and also blocks the fibronectin and fibrinogen-dependent adhesion but does not affect the viability of the cells. Lebectin can block α5β1 integrins. Hence, Lebectin prevents the proliferation, adhesion, invasion, and migration of cancer cell lines [161,162].

Sambucus nigra Agglutinin (SNA): SNA lectin is extracted from the elderberry plant, Sambucus nigra. It is isolated from the seeds or bark through a process involving crushing and purification [163].

In breast cancer, SNA lectin may induce changes in glycosylation, the addition of sugar molecules to proteins or lipids on the cell surface, potentially leading to significant effects on cancer progression [164]. For example, Lomax-Browne et al. conducted a study where they examined the variations in glycosylation of IgA1 in the serum of both healthy volunteers and patients with breast cancer. They employed several well-established commercial lectins, namely HPA, SNA, and MAL-II, for their analysis. The study revealed a significant alteration in N-glycosylation, particularly a notable increase in disialo-biantennary N-glycans of IgA1 in breast cancer patients [165]. These alterations in glycosylation could impact various crucial aspects of breast cancer development and behavior [166].

Firstly, changes in cell adhesion may occur, affecting how cancer cells stick to each other and the surrounding extracellular matrix. Altered adhesion properties could, in turn, influence tumor growth, invasion, and the formation of metastases [167]. Secondly, modifications in glycosylation may interfere with important signaling pathways within cancer cells. These disruptions could lead to the activation of pro-cancer pathways or the inhibition of tumor-suppressive pathways, ultimately influencing cancer cell behavior and survival [168]. Thirdly, the interactions between cancer cells and the immune system could also be affected. Changes in glycosylation patterns caused by SNA lectin binding might allow breast cancer cells to evade immune surveillance and avoid destruction by immune cells, potentially contributing to tumor immune evasion [169]. Furthermore, glycosylation changes could play a role in the metastatic process of breast cancer. The migration and invasion of cancer cells to distant organs are essential steps in metastasis, and alterations in glycosylation may impact

these metastatic properties [170].