Trichosanthin alleviates streptozotocin-induced type 1 diabetes mellitus in mice by regulating the balance between bone marrow-derived IL6+ and IL10+ MDSCs.

Myeloid-derived suppressor cells (MDSCs) occupy a pivotal role in the intricate pathogenesis of the autoimmune disorder, Type 1 diabetes mellitus (T1DM). Since our previous work demonstrated that trichosanthin (TCS), an active compound of Chinese herb medicine Tian Hua Fen, regulated immune response, we aimed to clarify the efficacy and molecular mechanism of TCS in the treatment of T1DM. To this end, T1DM mouse model was established by streptozotocin (STZ) induction. The mice were randomly divided into normal control group (Ctl), T1DM group (STZ), TCS treated diabetic group (STZ + TCS) and insulin-treated diabetic group (STZ + insulin). Our comprehensive evaluation encompassed variables such as blood glucose, glycosylated hemoglobin, body weight, pertinent biochemical markers, pancreatic histopathology, and the distribution of immune cell populations. Furthermore, we meticulously isolated MDSCs from the bone marrow of T1DM mice, probing into the expressions of genes pertaining to the advanced glycation end product receptor (RAGE)/NF-κB signaling pathway through RT-qPCR. Evidently, TCS exhibited a substantial capacity to effectively counteract the T1DM-induced elevation in random blood glucose, glycosylated hemoglobin, and IL-6 levels in plasma. Pathological scrutiny underscored the ability of TCS to mitigate the damage incurred by islets. Intriguingly, TCS interventions engendered a reduction in the proportion of MDSCs within the bone marrow, particularly within the IL-6+ MDSC subset. In contrast, IL-10+ MDSCs exhibited an elevation following TCS treatment. Moreover, we observed a significant down-regulation of relative mRNA of pro-inflammatory genes, including arginase 1 (Arg1), inducible nitric oxide synthase (iNOS), RAGE and NF-κB, within MDSCs due to the influence of TCS. It decreases total MDSCs and regulates the balance between IL-6+ and IL-10+ MDSCs thus alleviating the symptoms of T1DM. TCS also down-regulates the RAGE/NF-κB signaling pathway, making it a promising alternative therapeutic treatment for T1DM. Collectively, our study offered novel insights into the underlying mechanism by which TCS serves as a promising therapeutic intervention for T1DM.

Mitigation of Anti-Drug Antibody Production for Augmenting Anticancer Efficacy of Therapeutic Protein via Co-Injection of Nano-Rapamycin.

The induction of anti-drug antibody (ADA) is a formidable challenge for protein-based therapy. Trichosanthin (TCS) as a class of ribosome-inactivating proteins is widely studied in tumor treatment. However, the immunogenicity can induce the formation of ADA, which can cause hypersensitivity reactions and neutralize the efficacy of TCS, thus limiting its clinical application in cancer therapy. Here, a promising solution to this issue is presented by co-administration of the rapamycin nanoparticles and TCS. PEGylated rapamycin amphiphilic molecule is designed and synthesized as a prodrug and a delivery carrier, which can self-assemble into a nanoparticle system with encapsulation of free rapamycin, a hydrophobic drug. It is found that co-injection of the PEGylated rapamycin nanoparticles and TCS could mitigate the formation of anti-TCS antibody via inducing durable immunological tolerance. Importantly, the combination of TCS and the rapamycin nanoparticles has an enhanced effect on inhibit the growth of breast cancer. This work provides a promising approach for protein toxin-based anticancer therapy and for promoting the clinical translation.

Design and characterization of a novel tumor-homing cell-penetrating peptide for drug delivery in TGFBR3 high-expressing tumors.

Targeted therapy has attracted more and more attention in cancer treatment in recent years. However, due to the diversity of tumor types and the mutation of target sites on the tumor surface, some existing targets are no longer suitable for tumor therapy. In addition, the long-term administration of a single targeted drug can also lead to drug resistance and attenuate drug potency, so it is important to develop new targets for tumor therapy. The expression of Type III transforming growth factor ß receptor (TGFBR3) is upregulated in colon, breast, and prostate cancer cells, and plays an important role in the occurrence and development of these cancers, so TGFBR3 may be developed as a novel target for tumor therapy, but so far there is no report on this research. In this study, the structure of bone morphogenetic protein 4 (BMP4), one of the ligands of TGFBR3 was analyzed through the docking analysis with TGFBR3 and sequence charge characteristic analysis, and a functional tumor-targeting penetrating peptide T3BP was identified. The results of fluorescent labeling experiments showed that T3BP could target and efficiently enter tumor cells with high expression of TGFBR3, especially A549 cells. When the expression of TGFBR3 on the surface of tumor cells (HeLa) was knocked down by RNA interference, the high delivery efficiency of T3BP was correspondingly reduced by 40%, indicating that the delivery was TGFBR3-dependent. Trichosanthin (TCS, a plant-derived ribosome inactivating protein) fused with T3BP can enhance the inhibitory activity of the fusion protein on A549 cells by more than 200 times that of TCS alone. These results indicated that T3BP, as a novel targeting peptide that can efficiently bind TGFBR3 and be used for targeted therapy of tumors with high expression of TGFBR3. This study enriches the supply of tumor-targeting peptides and provides a new potential application option for the treatment of tumors with high expression of TGFBR3.

Corrigendum: Self-assembling and pH-Responsive protein nanoparticle as potential platform for targeted tumor therapy.

[This corrects the article DOI: 10.3389/fmolb.2023.1172100.].

Self-assembling and pH-responsive protein nanoparticle as potential platform for targeted tumor therapy.

Frequent injections at high concentrations are often required for many therapeutic proteins due to their short in vivo half-life, which usually leads to unsatisfactory therapeutic outcomes, adverse side effects, high cost, and poor patient compliance. Herein we report a supramolecular strategy, self-assembling and pH regulated fusion protein to extend the in vivo half-life and tumor targeting ability of a therapeutically important protein trichosanthin (TCS). TCS was genetically fused to the N-terminus of a self-assembling protein, Sup35p prion domain (Sup35), to form a fusion protein of TCS-Sup35 that self-assembled into uniform spherical TCS-Sup35 nanoparticles (TCS-Sup35 NP) rather than classic nanofibrils. Importantly, due to the pH response ability, TCS-Sup35 NP well retained the bioactivity of TCS and possessed a 21.5-fold longer in vivo half-life than native TCS in a mouse model. As a result, in a tumor-bearing mouse model, TCS-Sup35 NP exhibited significantly improved tumor accumulation and antitumor activity without detectable systemic toxicity as compared with native TCS. These findings suggest that self-assembling and pH responding protein fusion may provide a new, simple, general, and effective solution to remarkably improve the pharmacological performance of therapeutic proteins with short circulation half-lives.

Recombinant cell-penetrating trichosanthin synergizes anti-PD-1 therapy in colorectal tumor.

Alleviating immunosuppression of the tumor microenvironment is an important strategy to improve immune checkpoint therapy. It is an urgent but unmet need to develop adjuvant therapeutics for assisting the mainstay immunotherapies. Trichosanthin is an approved gynecology drug in China and its immunomodulatory effects have drawn much attention as an old drug for new applications in cancer. In this work, a recombinant cell-penetrating trichosanthin (rTCS-LMWP) was prepared via genetic fusion of a cell-penetrating peptide sequence (LMWP) to trichosanthin aiming to overcome the intratumoral penetration and intracellular delivery challenges. The potential of trichosanthin as an adjuvant therapy was explored, including its effects on tumor cells, antigen-presenting cells, tumor immune microenvironment, and the synergistic effect in combination with anti-PD-1. The results revealed that rTCS-LMWP can stimulate the maturation of dendritic cells via activating the STING-TBK1-IRF3 pathway, repolarize the protumor M2-type macrophages, and upregulate the pro-inflammatory cytokine expression. Moreover, rTCS-LMWP can enhance anti-PD-1 therapeutic efficacy in a CT26-bearing mouse model. The synergistic effect involved the induction of immunogenic cell death in the tumors, the proliferation and functionalization of cytotoxic T cells, and the suppression of the immunosuppressive regulatory T cells. These findings indicate that trichosanthin can be developed as an immunomodulator to facilitate cancer immunotherapy.

Screening and characterisation of a novel efficient tumour cell-targeting peptide derived from insulin-like growth factor binding proteins.

Targeted delivery of antitumor drugs is particularly important in tumour treatment. Tumour-targeted peptide is a very effective drug carrier for tumour therapy. Here, we screened and characterised a highly efficient targeted peptide named IHP5, which was derived from insulin-like growth factor binding proteins (IGFBPs). IHP5 exhibited preferential binding to the tested tumour cell lines. The delivery efficiency of IHP5 was higher in various tested tumour cells than in normal cells, especially in the human cervical cancer cell line HeLa, which was 11.7-fold higher than in normal human embryonic kidney cells HEK293. Moreover, the penetration efficiency of IHP5 was 13 times higher than that of the classical cell penetrating peptide TAT in HeLa cells. Detail analysis revealed that IHP5 endocytosis was possibly correlated with acetylated heparan sulphate proteoglycans including phosphatidylinositol proteoglycan 3 (GPC3), phosphatidylinositol proteoglycan 5 (GPC5) and syndecan 2 (SDC2). Subsequently, the introduction of IHP5 enhanced the inhibitory effect of trichosanthin (TCS) on tumour cells, resulting in at least 19-fold increase in tumour cells without enhanced cytotoxicity in normal cells HEK293. These results suggested that IHP5, as a novel tumour cell-targeting penetrating peptide with the ability to target tumour cells, has great potential in drug delivery applications.

Trichosanthin Promotes Anti-Tumor Immunity through Mediating Chemokines and Granzyme B Secretion in Hepatocellular Carcinoma.

Trichosanthin (TCS) is a type I ribosome-inactivating protein extracted from the tuberous root of the plant Trichosanthes. TCS shows promising potential in clinical drug abortion, anti-tumor and immunological regulation. However, the molecular mechanisms of its anti-tumor and immune regulation properties are still not well discovered. In the present study, we investigated the anti-tumor activity of TCS in hepatocellular carcinoma (HCC), both in vitro and in vivo. Both HCC cell lines and xenograft tumor tissues showed considerable growth inhibition after they were treated with TCS. TCS provoked caspase-mediated apoptosis in HCC cells and xenograft tumor tissues. The recruitment of CD8+ T cells to HCC tissues and the expression of chemokines, CCL2 and CCL22, were promoted upon TCS treatment. In addition, TCS induced an upregulation of Granzyme B (GrzB), TNF-α and IFN-γ in HCC tissues, which are the major cytotoxic mediators produced by T cells. Furthermore, TCS also resulted in an increase of mannose-6-phosphate receptor (M6PR), the major receptor of GrzB, in HCC tissues. In summary, these results suggest that TCS perhaps increases T-cell immunity via promoting the secretion of chemokines and accelerating the entry of GrzB to HCC cells, which highlights the potential role of TCS in anti-tumor immunotherapy.

Expanding role of ribosome-inactivating proteins: From toxins to therapeutics.

Ribosome-inactivating proteins (RIPs) are toxic proteins with N-glycosidase activity. RIPs exert their action by removing a specific purine from 28S rRNA, thereby, irreversibly inhibiting the process of protein synthesis. RIPs can target both prokaryotic and eukaryotic cells. In bacteria, the production of RIPs aid in the process of pathogenesis whereas, in plants, the production of these toxins has been attributed to bolster defense against insects, viral, bacterial and fungal pathogens. In recent years, RIPs have been engineered to target a particular cell type, this has fueled various experiments testing the potential role of RIPs in many biomedical applications like anti-viral and anti-tumor therapies in animals as well as anti-pest agents in engineered plants. In this review, we present a comprehensive study of various RIPs, their mode of action, their significance in various fields involving plants and animals. Their potential as treatment options for plant infections and animal diseases is also discussed.

Mannosylated engineered trichosanthin-legumain protein vaccine hydrogel for breast cancer immunotherapy.

The development of cancer vaccines based on tumor-associated antigens is hurdled by lack of an efficient adjuvant and insufficient efficacy. To improve the efficacy of vaccines, a genetically-engineered method was employed in this work to achieve the codelivery of antigen and adjuvant to enhance immune responses. Trichosanthin is a plant-derived protein that possesses cancer immune stimulation function. A genetically engineered protein vaccine composed of trichosanthin (adjuvant) and legumain domain (a peptidic antigen) was constructed, which was further chemically modified with mannose for targeting dendritic cells (DCs). The method is facile and ready for scaling up for massive production. Such a "two-in-one" vaccine is advantageous for codelivery for augmenting the immune responses. The vaccine inhibited the tumors by triggering a robust cytotoxic T lymphocyte response in the orthotopic-breast-tumor mice. Furthermore, the vaccine was loaded into the temperature-sensitive hydrogel based on Pluronic F127 for implanting use in the post-surgical site. The sustained-released vaccine from the hydrogel inhibited not only the tumor recurrence but also the lung metastases of breast cancer. These findings demonstrated that it was a safe and effective vaccination for breast cancer immunotherapy in a prophylactical and therapeutical manner for remodeling the tumor immune microenvironment and arresting tumor growth.

Tandem fusion of albumin-binding domains promoted soluble expression and stability of recombinant trichosanthin in vitro and in vivo.

Trichosanthin (TCS), as a type 1 ribosome-inactivating protein, has a very high cytoplasmic activity in vitro and can quickly kill cancer cells. However, it is easily filtered and cleared by the kidney, which results in the short half-life and severely limits its application. In this study, we constructed several recombinant proteins by fusing the albumin binding domain mutant ABD035(abbreviated as ABD) to the N- or C-terminus of TCS to endow the recombinant TCS fusion protein with a longer half-life property binding with endogenous human serum albumin (HSA) via ABD to effectively exert its anti-tumor activity in vivo. Pull down, Dynamic light scattering and ELISA assays all showed that TCS fused with two ABD sequences at the C-terminus of TCS, has stronger binding capacity to HSA in vitro than TCS with one ABD. In vivo studies in BALB/C mice were performed and the elimination half-life of TCS-ABD-ABD is about 15-fold longer compared to TCS and anti-tumor activity is about 30% higher than that of TCS alone in BALB/C mouse experiments. Moreover, we found that TCS with two ABDs in tandem have the highest soluble expression level, more than 5 times higher than that of TCS, and the yield of purified protein of TCS-ABD-ABD was as high as 68.9 mg/L culture solution, which was about 7-fold higher than that of TCS. Furthermore, MTT assay showed that the anti-tumor activity of TCS-ABD-ABD was significantly higher than TCS fused with only one ABD sequence, indicating that the repeated ABD sequences facilitated the biological activity of TCS. In this paper, the fusion of the albumin-binding domain in tandem with TCS can effectively improve its stability in vivo and also significantly increase its soluble expression, expanding the application of the albumin-binding domain in the high soluble expression and stability of protein drugs.

Advances on Delivery of Cytotoxic Enzymes as Anticancer Agents.

Cancer is one of the most serious human diseases, causing millions of deaths worldwide annually, and, therefore, it is one of the most investigated research disciplines. Developing efficient anticancer tools includes studying the effects of different natural enzymes of plant and microbial origin on tumor cells. The development of various smart delivery systems based on enzyme drugs has been conducted for more than two decades. Some of these delivery systems have been developed to the point that they have reached clinical stages, and a few have even found application in selected cancer treatments. Various biological, chemical, and physical approaches have been utilized to enhance their efficiencies by improving their delivery and targeting. In this paper, we review advanced delivery systems for enzyme drugs for use in cancer therapy. Their structure-based functions, mechanisms of action, fused forms with other peptides in terms of targeting and penetration, and other main results from in vivo and clinical studies of these advanced delivery systems are highlighted.

Trichosanthin inhibits cell growth and metastasis by promoting pyroptosis in non-small cell lung cancer.

Background: A number of studies have demonstrated that trichosanthin (TCS) can induce apoptosis in numerous types of tumor cell lines. However, whether TCS can induce pyroptosis has not yet been reported. This study aimed to investigate the role of TCS and its inhibitory effect on tumor growth by modulating pyroptosis in non-small cell lung cancer (NSCLC). Methods: Effects of different concentrations of TCS on the cell viability, proliferation, migration and invasion of NSCLC were detected by Cell Counting Kit-8 (CCK-8), colony formation, migration, and invasion assays. Immunofluorescence was used to detect the effect of TCS on the expression of pyroptosis marker protein gasdermin-D (GSDMD)-N in A549 cells. A tumor xenograft animal model was established by injecting A549 cells into nude mice. Results: In the present study, we found that TCS significantly inhibited the proliferation, migration, and invasion of A549 cells in a concentration-dependent manner. In addition, TCS at a high concentration (40 µg/mL) significantly promoted the expression of pyroptosis-related proteins [GSDMD-N, NLR family pyrin domain containing 3 (NLRP3), apoptosis-associated speck-like protein containing a CARD (ASC), caspase-1, and GSDMD], which showed an inhibitory effect on the pyroptosis of A549 cells. Additionally, we found that necrosulfonamide (NSA) significantly reversed the inhibitory effect of high concentrations of TCS on the pyroptosis of A549 cells. The in vivo experiments showed that TCS effectively reduced the tumor volume and inhibited the expression of Ki-67, whereas it increased the expression of GSDMD-N. Conclusions: Taken together, these results indicated that TCS could inhibit the progression of NSCLC by promoting pyroptosis. These findings provide further information on the possible underlying mechanism of TCS in the treatment of NSCLC.

A Sixty-Year Research and Development of Trichosanthin, a Ribosome-Inactivating Protein.

Tian Hua Fen, a herbal powder extract that contains trichosanthin (TCS), was used as an abortifacient in traditional Chinese medicine. In 1972, TCS was purified to alleviate the side effects. Because of its clinical applications, TCS became one of the most active research areas in the 1960s to the 1980s in China. These include obtaining the sequence information in the 1980s and the crystal structure in 1995. The replication block of TCS on human immunodeficiency virus in lymphocytes and macrophages was found in 1989 and started a new chapter of its development. Clinical studies were subsequently conducted. TCS was also found to have the potential for gastric and colorectal cancer treatment. Studies on its mechanism showed TCS acts as an rRNA N-glycosylase (EC 3.2.2.22) by hydrolyzing and depurinating A-4324 in α-sarcin/ricin loop on 28S rRNA of rat ribosome. Its interaction with acidic ribosomal stalk proteins was revealed in 2007, and its trafficking in mammalian cells was elucidated in the 2000s. The adverse drug reactions, such as inducing immune responses, short plasma half-life, and non-specificity, somehow became the obstacles to its usage. Immunotoxins, sequence modification, or coupling with polyethylene glycerol and dextran were developed to improve the pharmacological properties. TCS has nicely shown the scientific basis of traditional Chinese medicine and how its research and development have expanded the knowledge and applications of ribosome-inactivating proteins.

Emulsion Adjuvants for Use in Veterinary Vaccines.

The use of emulsion as adjuvants is widely used in veterinary vaccines. Emulsion adjuvants are inexpensive, stable, and relatively easy to prepare into vaccine formulations. Here we describe the preparation of oil-in-water emulsion adjuvant that has been shown to enhance immune responses and protect against diseases in pigs. This emulsion adjuvant and its variations could potentially be used alone or in combination with other adjuvants in veterinary vaccine formulations.

Genetically-engineered "all-in-one" vaccine platform for cancer immunotherapy.

An essential step for cancer vaccination is to break the immunosuppression and elicit a tumor-specific immunity. A major hurdle against cancer therapeutic vaccination is the insufficient immune stimulation of the cancer vaccines and lack of a safe and efficient adjuvant for human use. We discovered a novel cancer immunostimulant, trichosanthin (TCS), that is a clinically used protein drug in China, and developed a well-adaptable protein-engineering method for making recombinant protein vaccines by fusion of an antigenic peptide, TCS, and a cell-penetrating peptide (CPP), termed an "all-in-one" vaccine, for transcutaneous cancer immunization. The TCS adjuvant effect on antigen presentation was investigated and the antitumor immunity of the vaccines was investigated using the different tumor models. The vaccines were prepared via a facile recombinant method. The vaccines induced the maturation of DCs that subsequently primed CD8+ T cells. The TCS-based immunostimulation was associated with the STING pathway. The general applicability of this genetic engineering strategy was demonstrated with various tumor antigens (i.e., legumain and TRP2 antigenic peptides) and tumor models (i.e., colon tumor and melanoma). These findings represent a useful protocol for developing cancer vaccines at low cost and time-saving, and demonstrates the adjuvant application of TCS-an old drug for a new application.

The use of miR122 and its target sequence in adeno-associated virus-mediated trichosanthin gene therapy.

OBJECTIVE: Plant-derived cytotoxic transgene expression, such as trichosanthin (tcs), regulated by recombinant adeno-associated virus (rAAV) vector is a promising cancer gene therapy. However, the cytotoxic transgene can hamper the vector production in the rAAV producer cell line, human embryonic kidney (HEK293) cells. Here, we explored microRNA-122 (miR122) and its target sequence to limit the expression of the cytotoxic gene in the rAAV producer cells. METHODS: A miR122 target (122T) sequence was incorporated into the 3' untranslated region of the tcs cDNA sequence. The firefly luciferase (fluc) transgene was used as an appropriate control. Cell line HEK293-mir122 was generated by the lentiviral vector-mediated genome integration of the mir122 gene in parental HEK293 cells. The effects of miR122 overexpression on cell growth, transgene expression, and rAAV production were determined. RESULTS: The presence of 122T sequence significantly reduced transgene expression in the miR122-enriched Huh7 cell line (in vitro), fresh human hepatocytes (ex vivo), and mouse liver (in vivo). Also, the normal liver physiology was unaffected by delivery of 122T sequence by rAAV vectors. Compared with the parental cells, the miR122-overexpressing HEK293-mir122 cell line showed similar cell growth rate and expression of transgene without 122T, as well as the ability to produce liver-targeting rAAV vectors. Fascinatingly, the yield of rAAV vectors carrying the tcs-122T gene was increased by 77.7-fold in HEK293-mir122 cells. Moreover, the tcs-122T-containing rAAV vectors significantly reduced the proliferation of hepatocellular carcinoma cells without affecting the normal liver cells. CONCLUSION: HEK293-mir122 cells along with the 122T sequence provide a potential tool to attenuate the cytotoxic transgene expression, such as tcs, during rAAV vector production.

Phosphorylation of the conserved C-terminal domain of ribosomal P-proteins impairs the mode of interaction with plant toxins.

The ribosome is subjected to post-translational modifications, including phosphorylation, that affect its biological activity. Among ribosomal elements, the P-proteins undergo phosphorylation within the C terminus, the element which interacts with trGTPases or ribosome-inactivating proteins (RIPs); however, the role of phosphorylation has never been elucidated. Here, we probed the function of phosphorylation on the interaction of P-proteins with RIPs using the ribosomal P1-P2 dimer. We determined the kinetic parameters of the interaction with the toxins using biolayer interferometry and microscale thermophoresis. The results present the first mechanistic insight into the function of P-protein phosphorylation, showing that introduction of a negative charge into the C terminus of P1-P2 proteins promotes α-helix formation and decreases the affinity of the P-proteins for the RIPs.

Trichosanthin inhibits cervical cancer by regulating oxidative stress-induced apoptosis.

Based on many studies, trichosanthin (TCS) has an antiviral effect that regulates immune response, and targets cancer cells to exert broad-spectrum anti-tumor pharmacological activities. It is speculated that TCS may be a potential natural active drug for preventing as well as treating cervical cancer. But the clearer impact along with underlying TCS mechanism on cervical cancer are still unclear. The purpose of this study is to investigate the function and potential mechanism of TCS in cervical cancer. We measured the viability of cervical cancer cell lines (HeLa & caski cells) using CCK-8 analysis, detected cell proliferation efficiency through Ki-67 staining, analyzed cell apoptosis rate via flow cytometry as well as annexin V-FITC/PI double staining, performed apoptosis-related protein expression through western blotting, evaluated cell migration along with invasion by wound as well as transwell assays, carried out MMP via JC-1 and Rh123 fluorescent probes, as well as detected intracellular ATP and ROS levels by flow cytometry, respectively, to evaluate the effects of TCS. We found that TCS inhibited viability along with proliferation, induced apoptosis, as well as inhibited HeLa & caski cell migration along with invasion in a time- and dose-dependent manner. Additionally, TCS also reduced MMP, and the production of adenosine triphosphate, as well as induced the increase of intracellular reactive oxygen species in cancer cell lines. In accordance with the present studies, TCS inhibits HeLa & caski cell proliferation along with migration but promotes their apoptosis, which may be mediated by regulating oxidative stress.

Trichosanthin cooperates with Granzyme B to restrain tumor formation in tongue squamous cell carcinoma.

BACKGROUND: Tongue squamous cell carcinoma (TSCC) is a common type of oral cancer, with a relatively poor prognosis and low post-treatment survival rate. Various strategies and novel drugs to treat TSCC are emerging and under investigation. Trichosanthin (TCS), extracted from the root tubers of Tian-Hua-Fen, has been found to have multiple biological and pharmacological functions, including inhibiting the growth of cancer cells. Granzyme B (GrzB) is a common toxic protein secreted by natural killer cells and cytotoxic T cells. Our group has reported that TCS combined with GrzB might be a superior approach to inhibit liver tumor progression, but data relating to the use of this combination to treat TSCC remain limited. The aim of this study was to examine the effectiveness of TCS on TSCC processes and underlying mechanisms. METHODS: First, we screened the potential antitumor activity of TCS using two types of SCC cell lines. Subsequently, a subcutaneous squamous cell carcinoma xenograft model in nude mice was established. These model mice were randomly divided into four groups and treated as follows: control group, TCS treatment group, GrzB treatment group, and TCS/GrzB combination treatment group. Various tumorigenesis parameters, such as Ki67, PCNA, caspase-3, Bcl-2 and VEGFA, et al., were performed to determine the effects of these treatments on tumor development. RESULTS: Screening confirmed that the SCC25 line exhibited greater sensitivity than the SCC15 line to TCS in vitro studies. TCS or GrzB treatment significantly inhibited tumor growth compared with the inhibition seen in the control group. The TCS/GrzB combination inhibited tumor growth more than either drug alone. TCS treatment inhibited tumor proliferation by downregulating Ki67 and Bcl2 protein expression while accelerating tumor apoptosis. In the TCS/GrzB-treated group, expression of Ki67 was further downregulated, while the level of activated caspase-3 was increased, compared with their expression in either of the single drug treatment groups. CONCLUSION: These results suggest that the TCS/GrzB combination could represent an effective immunotherapy for TSCC.