Applications of Plant Lectins in Detection and Targeted Therapy of Urological Cancers

Abstract

Urological Cancers pose a serious threat to human health and represent a major challenge to healthcare systems worldwide. Among these, bladder cancer (BC), prostate cancer (PCa), and renal cancer (RC) are the most prevalent. Primary clinical management involves local or radical resection. However, for patients with advanced or inoperable disease, as well as those at high risk of post-surgical recurrence, chemotherapy remains an essential alternative or adjuvant treatment. Nevertheless, the lack of tumor targetability leads to low bioavailability and significant side effects of drugs, limiting the clinical application of chemotherapeutic agents. In recent years, plant lectins have gained significant attention in cancer therapy research owing to their unique tumor-recognition capabilities. Unlike traditional chemotherapeutic agents, they inherently bind specifically to abnormal glycans on urological tumor cells, endowing them with unparalleled targeted therapy advantages and great potential to address traditional chemotherapy’s core limitations and improve clinical outcomes. This paper presents a systematic, comprehensive and structured review with integrated critical analysis of the progress in this field. It first describes the clinical treatment methods for common urinary system tumors, including an analysis of the importance and limitations of chemotherapy. It then elaborates on the biological activities and antitumor mechanisms of plant lectins, highlighting on recent advances in the use of native lectins and lectin-modified drug delivery systems (DDS) for treating these malignancies. Finally, based on full collation and overall understanding of the existing literature, the application limitations of plant lectins are summarized, and their prospects are discussed.

Introduction

Cancer is the second leading cause of human death. According to the latest statistics from the International Agency for Research on Cancer, nearly 20 million new cancer cases were diagnosed globally in 2022, while approximately 9.7 million people died from cancer.1 Among them, new urinary system tumor cases and cancer-related deaths accounted for 13.1% and 8.9% of all cancers, posing a significant challenge to the global healthcare system.2 BC, PCa, and RC are the most common malignant tumors of the urinary system. BC is typically classified into two types: non-muscle-invasive BC (NMIBC) and muscle-invasive BC (MIBC). Among newly diagnosed cases, NMIBC and MIBC patients account for 75% and 25%, respectively.3 Chemotherapy plays a crucial role in the clinical treatment of these tumors. For example, transurethral resection of BC combined with postoperative intravesical perfusion of chemotherapeutic drugs is the conventional clinical treatment for NMIBC.4 For PCa and RC, chemotherapy remains urgently needed as an alternative or adjuvant treatment for patients with advanced or inoperable disease. The combination of androgen deprivation therapy and docetaxel chemotherapy has become the gold standard for the treatment of metastatic castration-sensitive prostate cancer.5 However, due to the lack of tumor specificity, the use of chemotherapeutic drugs in the treatment of urinary system tumors often causes adverse reactions such as urinary tract infections and renal function damage. For example, chemical cystitis is the main adverse reaction of intravesical chemotherapy, and its severity depends on the dosage and frequency of administration.6 Enhancing the tumor targeting of chemotherapeutic agents can effectively reduce the dosage and prolong the administration interval while maintaining or even improving therapeutic efficacy, thereby alleviating chemotherapy-related toxicity and treatment burden. In addition, the clinical chemotherapeutic effect of prostate cancer is also limited by the high therapeutic threshold and severe non-targeted toxicity of the drugs.7 Therefore, developing a targeted drug delivery system for urinary system tumors is an effective strategy to overcome the non-specific adverse reactions of chemotherapy.8

While plant lectins show great potential as a novel targeted strategy for urological tumors, their clinical translation is still limited by key challenges, mainly their inherent immunogenicity as exogenous proteins and relatively limited targeting specificity, which remain the main bottlenecks to be addressed in their practical application.9,10

This review systematically summarizes the progress of plant lectins in urinary system tumors, clarifies key clinical translation issues, and provides a reference for novel targeted diagnostic and therapeutic strategies. By integrating findings across experimental models, it bridges basic research and clinical application, laying a foundation for developing highly specific, low-toxicity targeted DDS modified with plant lectins. This review employed a rigorous process of literature screening, data extraction and cross-validation to ensure objectivity. Extracted data were categorized by research themes, including antitumor mechanisms, diagnostic applications and therapeutic delivery systems. Comparative analysis across studies comprehensively outlines the current status of plant lectins in urological tumor therapy.

Plant Lectins: Carbohydrate-Binding Properties and Biological Functions

Based on the comprehensive analysis of the included literature, this section systematically elaborates on the origin, biological activities and core carbohydrate-binding properties of plant lectins, which is the molecular basis for their application in urological tumor diagnosis and targeted therapy. The study of plant lectins began in 1888 when Peter Hermann Stillmark first discovered that the seed extract of Ricinus communis could agglutinate red blood cells and isolated a lectin named ricin from it.11 Plant lectins exhibit multiple biological activities, including antitumor, antibacterial, antifungal, antiviral, and anti-inflammatory effects.12–14 For example, Concanavalin A (ConA), derived from Canavalia ensiformis, is one of the most studied legume lectins. It can induce apoptosis, activate immune responses, and interfere with angiogenesis, thereby exhibiting notable antitumor, anti-inflammatory, antibacterial, antifungal, and vasodilatory effects, among others.15–17 Wheat germ agglutinin (WGA) isolated from wheat germ specifically binds to the fungal cell wall and disrupts its structural integrity, while also exerting antitumor effects.18,19 Mistletoe lectin (ML) in the extract of Viscum album shows significant antitumor effects, and ML from Viscum album is the first plant lectin to enter the clinical trial phase for cancer treatment.20–22

The reversible binding to carbohydrates is crucial for plant lectins to participate in biological processes, and lectins possess at least one non-catalytic domain capable of reversibly binding to carbohydrates.23–25 Carbohydrate chains (ie, glycans) interact with other biomolecules through glycosylation. For example, proteins can covalently link sugars to the polypeptide backbone via glycosylation (with N-glycosylation and O-glycosylation being the most common), which provides “tags” for lectins to recognize biomolecules.26 Advances in glycobiology and tumor microenvironment research have highlighted the key role of abnormal glycosylation in tumorigenesis and progression. Glycosylation changes can interfere with the functions of Receptor tyrosine kinase and cell adhesion molecules (such as integrins and adhesion proteins), thereby affecting processes such as tumor cell growth, migration, proliferation, and apoptosis.27 As illustrated in Figure 1, abnormal glycosylation in tumor cells promotes metastasis, whereas plant lectins can bind specifically to these aberrant glycans on the cell membrane and inhibit this process. This specific recognition and binding underpins the potential of plant lectins in cancer diagnosis and treatment. Indeed, plant lectins have demonstrated antitumor activity through mechanisms such as inhibiting proliferation and inducing programmed cell death, highlighting their potential as stand-alone therapeutic agents.10,28,29 The functional modification of carrier surfaces with lectins that specifically recognize and bind to specific glycan structures on tumor cell membranes can enhance their targeting and adhesion to cells or tissues. Using such lectin-modified DDS for targeted therapy of urinary system tumors is expected to improve drug bioavailability and reduce adverse reactions.

Figure 1.

Abnormal glycosylation of cell membranes promotes tumor cell metastasis, while plant lectins bind to tumor cells and inhibit their metastasis by specifically recognizing the binding domains at the end of glycosylation structures on the surface of tumor cell membranes.

Antitumor Mechanisms of Plant Lectins

The antitumor mechanisms of lectins include inducing cell apoptosis and autophagy, regulating immune responses, inhibiting angiogenesis, suppressing tumor cell adhesion and migration, and arresting the cell cycle (Figure 2).30 Analysis of numerous existing studies indicates that plant lectins often possess multiple antitumor mechanisms and exhibit a synergistic enhancement effect of multiple mechanisms (Table 1).

Figure 2.

Anti-tumor mechanisms of plant lectins.

Table 1.

Specific Binding Sites and Antitumor Mechanisms of Plant Lectins

Lectin Name	Binding Site	Antitumor Mechanisms
ConA	α-D-Mannose α-D-Glucose	a15 b31 c32
Viscum album L. var. Coloratum agglutinin	Galactose N-acetyl-D-galactosamine	a33 c34 d35
AGG	Galactose (β1→3) N-acetylgalactosamine	a36
WGA	GlcNAc Sialic acid	a37 c38
Polygonatum cyrtonema lectin	Mannose Sialic acid	a39 b40
Dioclea violacea lectin	Glucose Mannose	a41 b42 d43
SFL	Mannose	a44
Maackia amurensis agglutinin	Sialic acid	a45
Datura stramonium agglutinin	N-acetyllactosamine	e46
Jacalin	D-galactose	a47
Ricinus communis lectin I	D-galactose	f48

Notes: (a) induction of cell apoptosis; (b) induction of cell autophagy; (c) regulation of immune response; (d) inhibition of angiogenesis; (e) arrest of the cell cycle; (f) inhibition of cancer cell adhesion and migration.

Abbreviations: AGG, Abrus agglutinin; SFL, Sophora flavescens Lectin; GlcNAc, N-acetylglucosamine.

Induction of Cell Apoptosis

Cell apoptosis (type I programmed cell death) is a specific form of cell death. The core of the apoptotic program is the activation of the caspase cascade. Studies have shown that most plant lectins induce cell apoptosis through the mitochondria-dependent intrinsic pathway (Figure 3).

Figure 3.

The mechanism by which plant lectins induce intracellular intrinsic apoptosis.

ConA can induce intrinsic apoptosis in tumor cells by interfering with the protein kinase B (Akt) signaling pathway. Specifically, Akt phosphorylates downstream Foxo transcription factors, preventing them from entering the nucleus to activate the transcription of pro-apoptotic genes (like Bim and Puma), thereby inhibiting tumor cell apoptosis. ConA inhibits the Akt survival signal, thus relieving its apoptotic inhibitory effect. For example, ConA activates the mitochondria-mediated intrinsic apoptotic pathway by suppressing the upstream Akt survival signal and activating the downstream Foxo-Bim signaling in p53-null cells.49 Additionally, ConA induces intrinsic apoptosis in human melanoma A375 cells by increasing cytochrome c levels, stimulating caspase-9 and caspase-3.50

Abrus agglutinin (AGG), derived from the seeds of Abrus precatorius (an Indian medicinal plant), has been confirmed by studies to induce intracellular intrinsic apoptosis through activating the caspase cascade. Mukhopadhyay et al51 found that AGG triggers tumor cell apoptosis by regulating the expression ratio of Bcl-2 family proteins (Bax/Bcl-2). Bax and Bcl-2 are pro-apoptotic and anti-apoptotic proteins, respectively. The increase in Bax/Bcl-2 ratio regulated by AGG promotes the increase of mitochondrial membrane permeability, releases cytochrome c, and finally activates the caspase pathway in a dual dose- and time-dependent manner to trigger the intrinsic cell apoptosis program.

Induction of Cell Autophagy

In addition to the key mechanism of inducing cell apoptosis, the inhibition of cancer cell growth by lectins also relies on an important pathway of inducing cell autophagy. Autophagy (also known as Type II programmed cell death) is a process in which cells destroy their organelles through the use of autophagosomes and lysosomes,52 and it also serves as another mechanism for lectins to inhibit cancer cell growth. The formation of autophagic marker LC3II is central to autophagosome generation. Nascimento et al41 observed the autophagic tendency of Dioclea violacea lectin and ConA in stimulating C6 glioma cells. Interestingly, by monitoring the conversion of LC3I to LC3II, this autophagic process appears to be dynamic, initiating early and achieving a robust effect after 12 hours. The autophagic tendency emerged after 6 hours of incubation with 30–100 μg/mL lectins, while after 24 hours, this effect was only observed at lectin concentrations of 30 and 50 μg/mL. Furthermore, Polygonatum cyrtonema lectin extracted from Polygonatum cyrtonema induces autophagy in non-small cell lung cancer A549 cells by blocking the Akt-mTOR pathway;53 it also triggers apoptosis and autophagy in human MCF-7 breast cancer cells by targeting the epidermal growth factor receptor-mediated Ras-Raf-MEK-ERK signaling pathway.54

Regulation of Immune Response

It is a common antitumor mechanism for lectins to enhance tumor cell killing ability by regulating immune responses. All lectins exhibit interactions with the immune system, ranging from strong to weak.52

Certain lectins demonstrate antitumor effects by regulating immune responses, specifically through enhancing the killing activity of autologous immune cells against tumor cells and promoting cytokine secretion. ML, a type II ribosome-inactivating protein, has remarkable immunogenicity and significantly enhances antitumor immune responses through glycosylation-dependent recognition mechanisms: on one hand, it directly activates the phagocytic function of antigen-presenting cells (such as macrophages) and promotes the killing activity of natural killer (NK) cells against tumor cells; on the other hand, it promotes the secretion of cytokines such as TNF-α, interleukin-1β (IL-1β), IL-6, and IL-12.55 For instance, Viscum album L. var. coloratum agglutinin, a lectin specific for galactose and N-acetyl-D-galactosamine, may enhance antitumor effects by upregulating IFN-γ and TNF-α to promote proliferation, differentiation, and activation of immune cells.56 Additionally, ML has been confirmed as a ligand for Toll-like receptors, capable of activating Toll-like receptors signaling pathways and promoting the maturation and activation of dendritic cells.57

Inhibition of Angiogenesis

The initiation and progression of tumors rely on complex angiogenic networks and the regulation of the blood microenvironment. Lectins can interfere with tumor angiogenesis via pathways such as inhibiting the expression of vascular endothelial growth factor (VEGF), thereby exerting antitumor effects. Anti-angiogenic therapies targeting tumor angiogenesis (eg, VEGF inhibitors) have emerged as important strategies in tumor therapy.

Lectins exhibit significant potential to interfere with the angiogenic cascade by recognizing abnormally expressed glycosylation sites on the surface of tumor endothelial cells. Mukhopadhyay team found that AGG treatment significantly reduced the level of CD31 (angiogenesis marker) in tumor xenografts induced by HepG2 cells.51 This indicates that in addition to inducing tumor cell apoptosis, AGG can also effectively inhibit angiogenesis and cell proliferation, revealing the multi-target synergistic mechanism underlying its antitumor effect. Therefore, utilizing the multi-target synergistic mechanism of AGG in combination with traditional chemotherapeutic drugs may represent a novel anti-cancer therapeutic strategy with high efficacy and low toxicity. In addition to regulating immune responses, Viscum album L. var. Coloratum agglutinin also possesses anti-cancer potential by upregulating the expression of the chemokine CXCL9.56 CXCL9 exhibits significant anti-angiogenic properties, which are thought to be achieved by inhibiting endothelial cell migration, tube formation, and antagonizing VEGF signaling.

Arrest of the Cell Cycle

Lectins can also exert antitumor effects by arresting the cell cycle of tumor cells. Studies have shown that soybean agglutinin can arrest human breast cancer MCF-7 cells at the G2/M phase and inhibit the activity of cyclin-dependent kinases by upregulating the expression of p53 protein, thereby suppressing cell entry into the mitotic phase. Beyond stimulating the immune system, ML-1 can also induce cell cycle arrest at G2 or M phase to inhibit cell division.45 In clinical trials, the cell cycle arrest-inducing effect of ML-1 has been applied in the adjuvant therapy of glioblastoma, providing a synergistic anti-cancer effect for standard therapy.58

Inhibition of Cancer Cell Adhesion and Migration

Inhibiting cancer cell adhesion and migration is an effective approach for lectins to suppress cancer progression. For example, Ricinus communis lectin I, which is specific for mono-terminal galactose, can specifically bind to galactosylated glycoproteins associated with high metastasis on the surface of triple-negative breast cancer cells, and the degree of binding is positively correlated with cell metastatic capacity.48 Mechanistically, Ricinus communis lectin I may inhibit metastasis-related biological behaviors by blocking the interactions of adhesion molecules mediated by glycosylation modifications on the cell surface, thereby interfering with the binding of cells to the extracellular matrix and signal transduction.

The leaf lectin from Korean Viscum album coloratum exhibits antitumor metastatic effects: intravenous injection of 20–50 ng lectin into mice two days in advance can prevent lung metastasis of B16-BL6 melanoma cells or colon 26-M3.1 cancer cells; while administration of lectin 24 hours after inoculation of L5178Y-ML25 lymphoma cells can effectively inhibit the metastasis of tumor cells to hepatic and splenic tissues.59

Application of Plant Lectins in the Treatment of Urinary System Tumors

Plant Lectins Against BC

The main clinical therapy for NMIBC involves patients undergoing transurethral resection of bladder tumor combined with postoperative adjuvant chemotherapy. However, existing therapies have certain limitations, such as a high recurrence rate, non-response, or intolerance to local/systemic toxic reactions of bacilli Calmette-Guérin in some patients, and limited efficacy in advanced or high-risk patients. Notably, the surface of BC cells contains various glycan residues (eg, GlcNAc, α-D-mannose) that can be specifically recognized and bound by lectins. The abnormal glycan or glycoprotein expression patterns associated with these residues are not only closely related to tumor initiation, invasion, and metastasis, but also provide a unique molecular basis and potential breakthroughs for developing novel lectin-based strategies targeting tumor-specific glycosylation features in precision diagnosis and targeted therapy.

Lectins Used in BC Detection and Diagnosis

Abnormal glycosylation modifications in tumor cells result in structural abnormalities such as elongation, branching, sialylation, or fucosylation of glycan chains, thereby affecting the recognition and binding of lectins to tumor cells. Based on the carbohydrate-binding properties of lectins, novel strategies for cancer detection and diagnosis have been developed, including lectin affinity chromatography, lectin microarrays, and nanoplatforms.60,61 Relevant strategies are summarized in Table 2.

Table 2.

Application of Plant Lectins in the Diagnosis and Treatment of BC

Methods/Technologies	Lectins	Applications	Research Level
Affinity chromatography	ConA	Identify and enrich glycoproteins related to GlcNAc and mannose residues62	Clinical
Glycoproteomics analysis	WGA	Differentiate molecular subtypes of BC63	Cell
Lectin staining technique	Vicia villosa lectin	Examine glycan alterations from early to advanced stages of BC64	Clinical
Nano-probe technology	ConA, WGA, Sambucus nigra agglutinin	Dynamic monitoring of bladder tumor progression65	Clinical
Immunohistochemistry and lectin blotting	Amaranthus caudatus agglutinin, Jacalin	Study subtypes of human urothelial carcinoma66	Clinical
Coating the surface of nanoparticles	UEA-I	Non-invasive differentiation between BC and benign diseases67	Clinical
NanoLC-ESI-MS/MS	Vicia villosa lectin	Discovering BC biomarkers68	- (in silico analysis)

Abbreviation: UEA-I, Ulex europaeus agglutinin-I.

Multiple lectins, such as WGA, ConA, and Vicia villosa lectin, have been applied in BC detection. Plattner et al63 demonstrated that WGA can specifically bind to the human 5637 BC cell line and enter the cells via endocytosis. By combining glycomics analysis, this team found that the binding patterns (eg, intensity and distribution) of WGA can dynamically reflect changes in the glycan composition on the surface of tumor cells, providing stable glycobiological indicators for the molecular subtyping of BC and further assisting in assessing tumor malignancy or prognosis. The Kreunin team innovated a proteomic analysis method using ConA affinity chromatography to identify 186 proteins from urine samples of BC patients and non-tumor controls.62 Among these, R-1B-glycoprotein (containing GlcNAc and mannose residues) was detected exclusively in the BC patient group.

In the field of non-invasive diagnosis of BC, the application potential of combining lectins with immunohistochemistry and nanoplatform technologies has been explored. Azevedo et al65 modified ConA, WGA, and Sambucus nigra agglutinin on the surface of magnetic nanoprobes to identify CD44, a BC stem cell marker associated with poor prognosis, in the urine of patients with low/high-grade NMIBC. This technology overcomes the limitations of traditional tissue biopsy and provides a new tool for dynamic monitoring of bladder tumor progression. The proposal of the combined lectin histochemistry and immunohistochemistry technique has significantly improved diagnostic resolution, enabling simultaneous detection of cellular sugar residues and proteins.66 This study demonstrated that in normal urothelium, Amaranthus caudatus agglutinin and jacalin co-localize with uroplakins on the apical plasma membrane; in papillary urothelial carcinoma, however, they only co-localize with uroplakins in some regions. This spatial distribution heterogeneity reveals dynamic changes in glycosylation modifications of cancer cells. Therefore, by integrating the binding characteristics of different lectins, the technique can provide a basis for detailed subtyping of urothelial carcinoma, contributing to improved diagnosis and personalized treatment strategies.

Research on Lectin-Modified DDS for BC Treatment

Intravesical chemotherapy instillation has been widely used in clinical local treatment of NMIBC.69 Intravesical instillation achieves local high-concentration drug delivery through mucosal contact. Local drug exposure also avoids systemic toxicity caused by traditional chemotherapy and enhances tumor-killing efficiency; however, its clinical efficacy is limited by multiple physiological barriers, including obstacles such as urinary flushing, the glycosaminoglycan layer barrier, and the uroepithelial tight junction layer, resulting in low drug penetration efficiency.70 To address these challenges, lectin-modified DDSs have shown breakthrough potential, such as WGA-modified DDSs and ConA-modified DDSs. Such delivery systems specifically bind to abnormal glycans on the tumor surface via the sugar recognition domains of lectins, achieving targeted adhesion and triggering endocytosis, thus exhibiting advantages of efficient tumor targeting and enhanced drug uptake.

WGA-Modified DDS

WGA is one of the most well-studied plant lectins and was among the first lectins discovered to distinguish between healthy cells and cancer cells.71 DDS constructed using WGA can specifically recognize GlcNAc and sialic acid residues on the surface of BC cells, mediate the active targeting and accumulation of the delivery system at the lesion site, enhance the contact efficiency between drugs and tumor cells, and optimize therapeutic effects. WGA also possesses excellent mucosal adhesiveness. After binding to cell surface receptors, it can promote cellular uptake, holding promise for improving the cellular internalization efficiency of drugs in DDS at the target site.72 Using quantum dot-based single-particle tracking technology, it was found that the endocytic process of WGA is dependent on actin and microtubules (Figure 4).73 In a study involving six lectins (WGA, Solanum tuberosum lectin, Lens culinaris agglutinin, Ulex europaeus agglutinin (UEA), Peanut agglutinin (PNA), and Dolichus biflorus agglutinin), WGA showed the highest binding potential to normal urothelial cells, as well as low-grade and high-grade malignant urothelial cells. In these three cell lines, 66% to 88% of surface-bound WGA was uniformly internalized within 4 hours.74 Additionally, Plattner et al63 conducted single-cell level studies on the invasion of 5637 BC cells, showing that 25% and 67% of WGA was internalized and accumulated in acidic compartments at 10 and 40 minutes, respectively. These studies fully demonstrate the great potential of surface-functionalized WGA in enhancing the intracellular internalization of DDS.

Figure 4.

The Mechanisms of Endocytosis and Exocytosis of WGA.73 Lectins bind to receptors on the cell surface (1), are trapped in vesicles near the cell membrane (2), move slowly along actin filaments (3), move rapidly along microtubules (4), and move intermittently around the microtubule-organizing center (5). Exocytosis is the reverse of endocytosis: lectins move intermittently around the microtubule-organizing center (I), move rapidly along microtubules (II), move slowly along actin filaments (III), slow down at the cell membrane for vesicle fusion (IV), and are finally released into the extracellular space or re-enter the cytoplasm in the reverse direction (V). “+” represents the plus end of microtubules, and “-” represents the minus end. The “?” indicates that the mechanism or destination of vesicle transport in the vicinity of the cell membrane is not yet fully understood.

Wu et al75 designed and synthesized lectin WGA-modified multiresponsive mesoporous polydopamine composite nanorods. Through a coupling reaction, WGA was modified on the surface of the nanoparticles, endowing the nanocarrier with a stronger ability to penetrate the bladder wall and enter tumor cells. Experimental results showed that after the human BC cell line BIU-87 was incubated with WGA-modified nanoparticles under laser for 48 hours, the cell apoptosis rate was 20.41%, which was significantly higher than that of the non-WGA-modified group (approximately 15%). This confirmed that the targeting effect of WGA can enhance the antitumor efficacy of drug-loaded systems. Anzengruber et al76 prepared N-acyl-gemcitabine-loaded Poly(lactic-co-glycolic acid) (PLGA) nanoparticles (GemCx-PLGA-NPs). They functionalized the nanoparticles’ surface with WGA to enhance their retention time in the bladder and cellular uptake efficiency. In vitro single-cell level experiments showed that the adhesion of WGA-modified nanoparticles to human 5637 BC cells increased nearly fivefold. Observation via fluorescence microscopy revealed that WGA-PLGA-NPs were internalized by cells, while PLGA-NPs without lectin modification mainly attached to the cell surface, indicating that WGA can promote cellular internalization of nanoparticles.

To exploit the dual potential of targeting and internalization of WGA-modified DDS in BC treatment, various conjugates of WGA and drug carriers have been developed. Apfelthaler et al77 proposed an F-PGA-WGA drug delivery system composed of WGA as the targeting vector and α-poly-(L)-glutamic acid (PGA) as the polymer backbone, with fluorescein cadaverine (F) for visualization and tracking. Competitive inhibition experiments showed that the specificity of the interaction between the F-PGA-WGA delivery system and human 5637 BC cells was as high as 98%. The PGA polymer backbone provided numerous coupling sites, enabling a high drug-loading capacity of 77 molecules of the model drug dansyl cadaverine, and the drug-loaded system could still be internalized into urothelial cells via WGA mediation. Furthermore, the F-PGA-WGA delivery system demonstrated a 2.3-fold greater affinity for malignant cells than for healthy ones. This selectivity enables optimized treatment regimens, reduced toxicity to normal tissues, and lower drug dosages. DOX has broad-spectrum antitumor activity and can be used for adjuvant intravesical instillation therapy after NMIBC surgery, as well as systemic chemotherapy for MIBC. In another related study by Apfelthaler et al,78 DOX was conjugated to the PGA backbone to prepare WGA-PGA-DOX, achieving a drug loading of 81 molecules per mole of the backbone. The results showed that WGA-PGA-DOX demonstrated to have 56-fold higher cell binding potential than DOX alone in urothelial cell monolayer studies, and it was successfully internalized into urothelial cells, inhibiting cell viability by up to 99%. Additionally, the covalent conjugation of fluorescein-labeled bovine serum albumin (fBSA) with WGA is another promising targeted drug delivery strategy.79 For instance, inspired by the invasion mechanism of the bacterial adhesin FimH, Neutsch et al80 developed a conjugate of WGA and fBSA (fBSA/WGA20). This biomimetic strategy significantly enhanced the adhesion to BC cells and promoted their cellular uptake. At the single-cell level, the fBSA/WGA20 bioconjugate demonstrated a significantly stronger binding preference for BC cells than for non-malignant SV-HUC-1 cells, with relative increases of 57% for 5637 cells and 125% for HT-1376 cells. Furthermore, there were differences in the endocytic pathways and distribution of the conjugate among different urothelial cells: it was more likely to enter acidic compartments and undergo long-term retention in SV-HUC-1 cells, while HT-1376 cancer cells might activate more endocytic pathways (like caveolin-dependent pathways), leading to rapid lysosomal degradation of the conjugate.

ConA-Modified DDS

In recent years, ConA lectin has attracted extensive attention in the field of tumor-targeted therapy due to its unique sugar-binding properties. The biological activity of ConA stems from the sugar-binding sites in its tetrameric structure, which can specifically recognize and bind to glycosylated structures containing α-D-Mannose, α-D-Glucose, and their derivatives on the cell membrane surface. Mannose is one of the most abnormally expressed monosaccharides on the surface of BC cells, providing a molecular basis for ConA-mediated targeted delivery. ConA can mediate the active targeting of tumor microenvironment-responsive (eg, pH and temperature) DDS to bladder tumor tissues, enabling efficient and precise drug release while reducing toxic side effects on normal tissues.

Li et al81 synthesized the amphiphilic block copolymer PCL-b-PManEA using polycaprolactone (PCL), whose micellar corona contains D-mannopyranoside groups. Utilizing the carbohydrate-lectin interaction between ConA and D-mannopyranoside groups, they constructed a DOX-loaded PCL-b-PManEA@ConA drug-loaded system (Figure 5A). The innovation of this system lies in its dual targeting strategy. The conjugation of ConA to the micelle surface not only enables site-specific carrier modification but also preserves its carbohydrate-binding activity. This allows the ConA-decorated micelles to adhere to α-D-mannose and α-D-glucose residues in the bladder mucosa, thereby enhancing retention by resisting urinary washout. Notably, the micelle size has a significant impact on ConA conjugation efficiency. After adding an equal amount of lectin, the time for ConA conjugation to reach saturation was 5 and 10 minutes for small-sized micelles with a diameter of 117.7 nm and micelles with a diameter of 152.4 nm, respectively. This may be attributed to the larger binding surface area provided by small-sized micelles. In vitro, the ConA-conjugated micelles displayed biphasic drug release kinetics—an initial burst followed by a sustained slow release—that was modulated by the PCL chain length. They can be taken up by UMUC3 human urothelial carcinoma cells via endocytosis, showing significant cytotoxicity and anticancer efficiency comparable to free DOX, thus holding potential for application in intravesical treatment of NMIBC.

Figure 5.

Preparation of ConA-modified DDS. (A)81 DOX-loaded PcL-b-PManEA@ConA; (B)82 ConA-EPI conjugate.

Intravesical instillation of EPI can prevent tumor recurrence and progression after transurethral resection of bladder tumors, but it lacks tumor selectivity. To address this, researchers used ConA as a targeting vector to construct a ConA-EPI conjugate that can be selectively internalized by BC cells (Figure 5B) and conducted a safety evaluation of ConA.82 The ConA-EPI conjugate exhibited selective toxicity to BC cells in vitro. This activity involves a sequential process: the conjugate is internalized via endocytosis, EPI is released within lysosomes, and subsequently traffics to the nucleus to induce cell death. In addition, the conjugate showed a longer retention time and enhanced tumor growth inhibitory effect compared with free EPI in the MB49 orthotopic mouse model of BC, demonstrating that ConA endows the drug delivery system with the ability of tumor-targeted adhesion and internalization accumulation. Safety monitoring of ConA via intravesical instillation revealed that after six instillations, there were no significant variations in mouse body weight or serum biochemical indicators, indicating that it can serve as a safe delivery vector for targeted chemotherapy of BC.

Plant Lectins Against PCa

Early-stage PCa has no obvious symptoms and is often detected incidentally during physical examinations involving prostate-specific antigen (PSA) testing or digital rectal examination. Increased detection of early-stage prostate cancer can reduce the incidence of metastatic prostate cancer.83 Prostate cancer cells have abundant N-acetylgalactosamine and GlcNAc residues on their surface, which form the basis for lectins to serve as potential tools in the detection, diagnosis of prostate cancer, and the development of chemotherapy DDS.

Lectins in the Detection and Diagnosis of PCa

Lectins exhibit significant value in the detection and diagnosis of PCa. Currently, PSA and prostate-specific membrane antigen are the most used biomarkers for PCa screening, among which prostate-specific membrane antigen has been approved by the U.S. Food and Drug Administration as a theranostic target.84,85 A variety of lectins have been applied to detection platforms for specific PSA glycomic analysis.86 For example, lectin-based immunoassays have been used to detect PSA in the serum of PCa patients.87

Lectins show significant potential in distinguishing between benign and malignant PCa as well as in assessing invasiveness. Koistinen et al88 further advanced the application of lectins in PCa detection by combining in situ proximity ligation assay with 25 glycan-binding lectins to screen for PSA glycoforms specifically expressed in prostate cancer tissues. They identified that succinylated WGA and Vicia villosa agglutinin could specifically recognize cancer-associated PSA glycoforms with GlcNAc and terminal GalNAc epitopes respectively, and these two lectins showed extremely significant enrichment in cancerous tissues compared with adjacent benign tissues (p<10⁻⁴ for both). This study for the first time confirmed the specific binding of lectins to aberrantly glycosylated PSA in situ at the tissue level, and excluded the suboptimal lectins such as Wisteria floribunda agglutinin and Maackia amurensis agglutinin I previously used in PSA glycoform detection, providing novel and specific lectin targets for the development of PCa serological diagnostic methods. Wang et al89 developed a glycoproteomic strategy based on two lectins, Lens culinaris agglutinin and Aleuria aurantia lectin, which effectively distinguished invasive PCa from non-invasive PCa by detecting fucosylated PSA in serum. Additionally, Cramoll lectin nanoelectrodes constructed using carboxylated carbon nanotubes and polylysine exhibit high sensitivity in distinguishing serum glycoprotein profiles between patients with benign prostatic hyperplasia and advanced PCa, providing a new method for the clinical staging of PCa.90 For patients with low PSA levels (<10 ng/mL), Kazuno et al91 found that detecting the serum level of clusterin recognized by Maclura pomifera agglutinin helps distinguish PCa from benign prostatic diseases, thereby improving clinical detection accuracy. Lectins also play a role in revealing prognosis-related glycosylation changes. Haq et al92 specifically detected glycosylation patterns on the surface of PCa cells using Maackia amurensis agglutinin (which recognizes α2,3-sialic acid) and Sambucus nigra agglutinin (which recognizes α2,6-sialic acid). They found that α2,6-sialic acid was upregulated in gemcitabine-resistant variants of PC3 cells. This indicates that specific glycosylation modifications (eg, α2,6-sialylation) may serve as prognostic markers for evaluating prostate tumor invasiveness or therapeutic response.

Lectin-Modified DDS for PCa Treatment

The lectin Bauhinia purprea agglutinin (BPA), with galactose-binding specificity, exhibits strong targeting ability for PCa. Ikemoto et al93 developed a BPA-modified PEG liposome encapsulating the antitumor drug DOX (BPA-PEG-LPDOX). In in vitro cytotoxicity experiments (3 or 10 μg/mL DOX), BPA-PEG-LPDOX containing lectin showed a stronger inhibitory effect on the proliferation of DU145 cells (a human PCa cell line) than PEG-LPDOX without lectin, confirming that BPA can enhance the anti-PCa efficacy of LPDOX. After tail vein injection of BPA-PEG-LPDOX at a dose of 2 mg/kg/day (once a week, 3 times in total) into tumor-bearing mice inoculated with DU145, the tumor volume of the mice was significantly smaller than that of the mice in the PEG-LPDOX treatment group. This is attributed to the interaction between the surface-modified lectin BPA and target molecules in tumor tissues, as the team observed the association of BPA-PEG-LP with cells, and the accumulation of BPA-PEG-LP in tumor tissues of tumor-bearing mice was significantly higher than that of non-lectin-modified PEG-LP.

Plant Lectins Against RC

Kidney diseases are a major global public health issue, among which the incidence of RC is increasing year by year worldwide, with a more pronounced upward trend in European countries and young populations.94 Renal cell carcinoma accounts for 85% of RC, of which approximately 70% is clear cell renal cell carcinoma (ccRCC).95 Clinical treatments for RC mainly include partial resection and radical resection; however, for patients with advanced disease or those ineligible for surgery, treatment still relies on systemic chemotherapy.

In clinical applications against RC, lectins are most adopted in assisting pathological diagnosis and provide important molecular markers for the pathological classification and differential diagnosis of RC. Rangel et al96 developed a biosensor using PNA lectin, which can distinguish case samples from cancer-free individuals and patients with various cancers, including RC, by detecting the expression of T antigen in samples. In addition, the surface of renal collecting duct carcinoma cells usually expresses glycostructures (including fucosylated structures) recognizable by UEA-I and PNA lectins, while ccRCC and renal papillary carcinoma do not express such structures. Therefore, the combination of these two lectins with immunohistochemistry can distinguish collecting duct tumors from other RC subtypes.97,98 For example, in a case of collecting duct carcinoma in a 29-year-old female, immunohistochemical detection showed positive expression of UEA-I-binding glycostructures in tumor cells, indicating the presence of α-linked fucosylated glycan structures on the surface of cancer cells.99 This result is consistent with the immunoreactive characteristics of collecting duct epithelial cells, supporting the diagnosis that the tumor originates from renal medullary collecting ducts, and differs from the immunophenotype of other types of RC (like ccRCC), providing a molecular marker basis for the pathological classification and differentiation of this rare case. Furthermore, in clinical trials, the recombinant ML-1 protein Aviscumine demonstrated a disease-stabilizing effect in patients with renal cancer, although no tumor shrinkage was observed.100

Summary and Prospect

This article provides an overview of clinical management for urinary system tumors and the bioactivities of plant lectins, while emphasizing recent research progress on plant lectins and their modified DDS in treating these malignancies. Surface functionalization with plant lectins can confer tumor-targeting capabilities to DDS, thereby enhancing chemotherapeutic efficacy while minimizing side effects. As multifunctional molecules, plant lectins exhibit a range of biological activities—including antibacterial, antiviral, and anti-inflammatory properties—and can exert antitumor effects through various pathways. By virtue of their specific binding to carbohydrates and recognition of tumor-specific aberrant glycosylation, plant lectins show great potential for the detection, diagnosis and targeted therapy of urological tumors, and lectin-functionalized DDS can effectively enhance tumor targeting and cellular uptake, thus improving chemotherapy efficacy and reducing systemic side effects.

The advantages of lectin-based detection and diagnostic technologies lie in their non-invasiveness and specificity. However, they are still limited by the complex biological activities of lectins, significant interspecific differences, and the potential for cross-reactivity between some lectins and glycosylated structures in normal tissues, which may lead to false positive results. For instance, WGA also exhibits a certain affinity for sialic acid residues in inflamed tissues. Future research on lectin-modified DDS shall be advanced in line with the hierarchical progressive principle of taking basic mechanisms as the foundation, technical optimization as the core and clinical translation as the ultimate goal. Priority should be given to investigating core basic mechanisms to elucidate the binding differences and selectivity rules between various lectins and the specific glycan epitopes of urological tumors, thereby addressing the off-target effects caused by glycosyl heterogeneity in cancer cells and the expression of analogous glycosyl groups in normal cells at the source. Multi-dimensional technological modifications are required to optimize key technologies and resolve the issues of stability, biosafety and cellular uptake efficiency of the delivery system, including developing multi-responsive “smart” carriers adapted to the tumor microenvironment, evading immune rejection via strategies such as PEGylation, and exploring the endocytosis-related functional regions on tumor cell membranes to realize the precise anchoring of the delivery system and enhance its cellular uptake efficiency. In addition, large-sample and multi-center comprehensive clinical trials should be launched to verify the clinical safety, anti-tumor efficacy and applicable scope of the delivery system, so as to facilitate its official application in the clinical diagnosis and treatment of urological tumors.

Notably, lectin-based strategies hold great promise for personalized medicine in urological cancer care. Owing to the heterogeneous glycosylation of tumor cells in different patients, lectins can be tailored to target patient-specific glycoepitopes, allowing personalized diagnosis and customized targeted drug delivery. Addressing these scientific and translational challenges requires interdisciplinary collaboration. Joint efforts in materials science, biomedical engineering, glycobiology and tumor biology are critical to breaking bottlenecks and accelerating clinical translation.

Although plant lectins and their modified DDS have various pending issues in the detection, diagnosis, and treatment of urinary system tumors, with the continuous advancement of biomedical technologies and in-depth exploration by scientists into tumor therapy and the activities of plant lectins, we believe these issues will be gradually overcome.

Funding Statement

This work was supported by Key Discipline Construction Projects of Shanghai Health System (2024ZDXK0062) and Xuhui Health System (SHXHZDXK202310), Shanghai Sixth People’s Hospital Medical Group Scientific Research Project, and Shanghai Eighth People’s Hospital Research Project (SHBY202518).

Author Contributions

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Disclosure

The authors report no conflicts of interest in this work.