Lipophilic recombinant-protein insertion endows lymphocytes with enhanced targeting-infiltration ability in EGFR positive cancer.

Adoptive T cell transfer is one of the most promising ways to combat solid tumors. However, the weak infiltration of T cells into tumor sites has restricted their antitumor efficacy. To overcome this obstacle, we used the lipophilic protein painting strategy to improve tumor targeting and penetrating capacity of lymphocytes for the first time. We synthesized the lipid anchor consisting of a bispecific recombinant protein iRGD-antiEGFR and DSPE-PEG derivates, then successfully inserted it into the membranes of T cells. This surface modification was non-invasive and could efficiently improve the infiltration ability of T cells into multicellular spheroids and tumor masses. The surface modified T cells also displayed superior antitumor activities in EGFR-positive tumor xenografts via systematic infusion. Moreover, the permeability and antitumor efficacy of these surface painted T cells could be remarkably enhanced when used in combination with local low-dose irradiation.

Membrane fusogenic nanoparticle-based HLA-peptide-addressing universal T cell receptor-engineered T (HAUL TCR-T) cell therapy in solid tumor.

T cell receptor-engineered T (TCR-T) cell therapy has demonstrated therapeutic effects in basic research and clinical trials for treating solid tumors. Due to the peptide-dependent recognition and the human leukocyte antigen (HLA)-restriction, TCR-T cell therapy is generally custom designed to target individual antigens. The lack of suitable universal targets for tumor cells significantly limits its clinical applications. Establishing a universal TCR-T treatment strategy is of great significance. This study designed and evaluated the HLA-peptide-addressing universal (HAUL) TCR-T cell therapy based on HLA-peptide (pHLA) loaded membrance fusogenic deliver system. The pHLA-NP-based tumor cell membrane modification technology can transfer the pHLA onto the surface of tumor cells through membrane fusogenic nanoparticles. Then tumor cells are recognized and killed by TCR-T cells specifically. The HAUL TCR-T cell therapy technology is a universal technology that enables tumor cells to be identified and killed by specific TCR-T cells, regardless of the HLA typing of tumor cells.

Individualised adjuvant immunotherapy with neoantigen-reactive T cells for gastric signet-ring cell carcinoma.

Objectives: The signet-ring cell carcinoma (SRCC) of the stomach is highly invasive. Patients with stage III gastric SRCC usually experience tumor recurrence within 2 years after radical surgery. Unfortunately, there is no effective treatment to postpone recurrence following adjuvant chemotherapy. Our study aimed to explore the safety and efficacy of neoantigen-reactive T lymphocytes (NRTs) in patients with stage III gastric SRCC. Methods: The study included 20 patients with stage III gastric SRCC who received radical surgery and adjuvant chemotherapy. Following the adjuvant chemotherapy, they underwent treatment with a range of one to four cycles of personalised neoantigen-reactive T cells. The primary endpoint was the median progression-free survival (mDFS). The secondary endpoint was safety and immune responses. The median duration of follow-up was 41 months (95% CI: 39-42.9 months). Results: Our results showed that patients who received adjuvant neoantigen-reactive T-cell immunotherapy demonstrated a propensity towards prolonged disease-free survival (DFS) and overall survival (OS) in comparison to previous studies. The 2-year DFS and OS rates reached 73.7% and 95%, respectively, whereas the 5-year DFS and OS rates were 44% and 69%. The median DFS was 41 months (95% CI: 28.9-53.1 months) and the median OS was not reached. In addition, there was a significant increase in serum concentrations of IL-2, IL-4, IL-6, IL-10, TNF-α and IFN-γ after cell immunotherapy. The adverse reactions were mild. Conclusion: In conclusion, adjuvant immunotherapy with NRTs showed promising efficacy alongside a manageable safety profile.

Neoadjuvant sintilimab in combination with concurrent chemoradiotherapy for locally advanced gastric or gastroesophageal junction adenocarcinoma: a single-arm phase 2 trial.

In this multicenter, single-arm phase 2 trial (ChiCTR1900024428), patients with locally advanced gastric/gastroesophageal junction cancers receive one cycle of sintilimab (anti-PD1) and chemotherapy (S-1 and nab-paclitaxel), followed by 5 weeks of concurrent chemoradiotherapy and sintilimab, and another cycle of sintilimab and chemotherapy thereafter. Surgery is preferably scheduled within one to three weeks, and three cycles of adjuvant sintilimab and chemotherapy are administrated. The primary endpoint is the pathological complete response. Our results meet the pre-specified primary endpoint. Thirteen of 34 (38.2%) enrolled patients achieve pathological complete response (95% CI: 22.2-56.4). The secondary objectives include disease-free survival (DFS), major pathological response, R0 resection rate, overall survival (OS), event-free survival (EFS), and safety profile. The median DFS and EFS were 17.0 (95%CI: 11.1-20.9) and 21.1 (95%CI: 14.7-26.1) months, respectively, while the median OS was not reached, and the 1-year OS rate was 92.6% (95%CI: 50.1-99.5%). Seventeen patients (50.0%) have grade ≥3 adverse events during preoperative therapy. In prespecified exploratory biomarker analysis, CD3+ T cells, CD56+ NK cells, and the M1/M1 + M2-like macrophage infiltration at baseline are associated with pathological complete response. Here, we show the promising efficacy and manageable safety profile of sintilimab in combination with concurrent chemoradiotherapy for the perioperative treatment of locally advanced gastric/gastroesophageal junction adenocarcinoma.

Hepatoid adenocarcinoma of the duodenal papilla with hepatic metastases: A case report and literature review.

Hepatoid adenocarcinoma of the duodenum is a rare special type of adenocarcinoma, featured by hepatocyte components in primary adenocarcinoma of the duodenum. It has the characteristics of high malignancy, invasiveness, rapid progress, and poor prognosis. An abnormal elevation of serum alpha-fetoprotein (AFP) may occur in most cases. The diagnosis is mainly based on pathological morphology. Here, we reported a case of hepatic adenocarcinoma of the duodenum. The middle-aged female patient had an ampulla mass at diagnosis and received radical pancreaticoduodenectomy. The postoperative pathology was stage IIIA duodenal adenocarcinoma. At 1 month after surgery, she had multiple intrahepatic metastases and retroperitoneal lymph node metastasis; the AFP level was 300 ng/ml at that time. As she refused target therapy, two cycles of capecitabine-oxaliplatin (XELOX) chemotherapy were performed. However, the AFP elevated from 300 to 1,931.90 ng/ml, and the disease progressed rapidly. Immunohistochemistry (IHC) of tissue samples from presurgical endoscopic ultrasound guided fine needle aspiration (EUS-FNA), surgery, and liver biopsy showed positive AFP staining. Combining the abnormal elevation of serum AFP and microscopic pathological morphology, this case is diagnosed as hepatoid adenocarcinoma of the duodenum with liver metastasis. The physical condition of this patient was too poor to receive follow-up treatment. She died of the rapid disease progression with an overall survival time of 161 days. Considering that in most patients with hepatoid adenocarcinoma the abnormal elevation of serum AFP occurs preoperatively and returns to normal postoperatively rather than normal before surgery and increased after surgery, the primary lesion is located in the stomach rather than the intestine, and the patients are more often older men rather than middle-aged women; this case is rare particularly. Therefore, reporting this case with complete case data may be helpful to further study, so as to improve the understanding of this special type of malignant tumor.

Modification of erythrocytes by internalizing Arg-Gly-Asp (iRGD) in boosting the curative effect of radiotherapy for gastric carcinoma.

Background: Radiation resistance remains the leading cause of radiotherapy (RT) failure. The development of tumor-specific targeted sensitizers is key to overcoming radiation resistance. Our early data showed that cancer cell penetration was simulated by internalizing arginine-glycine-aspartic acid (iRGD), and the irradiation efficacy was improved. The present study aims to design and fabricate iRGD-modified red blood cell (RBCs) for tumor targeting and RT enhancement, and to evaluate its safety and efficacy in vivo. Methods: 1,2-Distearoyl-sn-glycero-3-phosphoethanolamine-poly ethylene glycol-iRGD (DSPE-PEG-iRGD) was used to modify RBCs by a lipid-insertion method without direct chemical bioconjugation. Fluorescent dyes were used to trace the functional RBCs through confocal microscopy examination. In vitro stability evaluation was performed using cell culture medium incubation for 48 h followed by fluorescence decay assay. Furthermore, a subcutaneous cancer cell mouse model was constructed with MKN-45 cells for target efficacy and RT enhancement evaluation with DSPE-PEG-iRGD-modified RBCs (RBC-iRGD). Results: Successful construction of RBC-iRGD was verified by the presence of the yellow fluorescence, and an approximately 108 iRGD molecules were labeled on a single RBC. The final RBC-iRGD showed good stability without any hemolytic effects in the cell culture medium. Moreover, higher fluorescence intensity and decreased liver and spleen accumulation could be observed in RBC-iRGD compared to RBC + iRGD in vivo. The RBC-iRGD exerted enhanced radiosensitivity in subcutaneous gastric tumor mice. Conclusions: The RBC-iRGD exerted good tumor-targeting efficacy and favorable effects for RT enhancement in vivo.

In situ antigen modification-based target-redirected universal chimeric antigen receptor T (TRUE CAR-T) cell therapy in solid tumors.

BACKGROUND: Chimeric antigen receptor (CAR)-T cell therapy has demonstrated remarkable success in the treatment of hematologic malignancies, while the success has not yet been replicated in solid tumors. To some extent, the disappointing results can be attributed to the paucity and heterogeneity of target antigens in solid tumors since adequate antigens are the cornerstone for CAR-T cells to recognize and attack tumor cells. METHODS: We established a target-redirected universal CAR-T (TRUE CAR-T) cell therapeutic modality, in which exogenous antigens are loaded onto fusogenic nanoparticles to achieve in situ modification of cell membrane in solid tumors, providing targets for subsequent CAR-T cell therapy. The modification effect was evaluated by flow cytometry and confocal microscopic imaging. The in vivo metabolism and biodistribution of fusogenic antigen loaded nanoparticles (F-AgNPs) was explored using near infrared living imaging. Then F-AgNPs mediated in situ antigen modification were cooperated with corresponding CAR-T cell therapy, and its antitumor efficacy was evaluated using immune function experiments and further investigated in different tumor models. RESULTS: Using F-AgNPs, exogenous antigens were selectively modified onto tumor cell membranes through membrane fusion, spread deeper into tumor tissues through intercellular lipid transfer, further activating corresponding CAR-T cells and mediating antitumor immune responses towards multiple types of tumor cells, despite of their inherent antigen profiles. The cooperative treatment of F-AgNPs and CAR-T cell therapy successfully suppressed tumor proliferation and prolonged survival in both subcutaneous and peritoneally disseminated tumor models. CONCLUSION: The fusogenic nanoparticle-based in situ antigen modification overcome the limitation of target antigens paucity and heterogeneity in solid tumors, improving the efficacy and broadening the applications of CAR-T cells, thus establishing a novel TRUE CAR-T cell therapeutic modality with universal application and translational potential in immunotherapies for solid tumors.

Identification of a Glypican-3 Binding Peptide From a Phage-Displayed Peptide Library for PET Imaging of Hepatocellular Carcinoma.

Tumor-targeting peptides functioned as molecular probes are essential for multi-modality imaging and molecular-targeting therapy in caner theronostics. Here, we performed a phage-displayed bio-panning to identify a specific binding peptide targeting Glypican-3 (GPC-3), a promising biomarker in hepatocellular carcinoma (HCC). After screening in the cyclic peptide library, a candidate peptide named F3, was isolated and showed specific binding to HCC cell lines. In a bio-distribution study, higher accumulation of F3 peptide was observed in HepG-2 tumors compared to PC-3 tumors in xenograft models. After labeling with radioactive 68Ga, the F3 peptide tracer enabled the specific detection of tumors in HCC tumor models with PET imaging. More importantly, the expression of GPC-3 in human tissue samples may be distinguished by an F3 fluorescent peptide probe indicating its potential for clinical application. This cyclic peptide targeting GPC-3 has been validated, and may be an alternative to serve as an imaging probe or a targeting domain in the drug conjugate.

Bifunctional iRGD-anti-CD3 enhances antitumor potency of T cells by facilitating tumor infiltration and T-cell activation.

BACKGROUND: Poor infiltration and limited activation of transferred T cells are fundamental factors impeding the development of adoptive cell immunotherapy in solid tumors. A tumor-penetrating peptide iRGD has been widely used to deliver drugs deep into tumor tissues. CD3-targeting bispecific antibodies represent a promising immunotherapy which recruits and activates T cells. METHODS: T-cell penetration was demonstrated in tumor spheroids using confocal microscope, and in xenografted tumors by histology and in vivo real-time fluorescence imaging. Activation and cytotoxicity of T cells were assessed by flow cytometry and confocal microscope. Bioluminescence imaging was used to evaluate in vivo antitumor effects, and transmission electron microscopy was used for mechanistic studies. RESULTS: We generated a novel bifunctional agent iRGD-anti-CD3 which could immobilize iRGD on the surface of T cells through CD3 engaging. We found that iRGD-anti-CD3 modification not only facilitated T-cell infiltration in 3D tumor spheroids and xenografted tumor nodules but also induced T-cell activation and cytotoxicity against target cancer cells. T cells modified with iRGD-anti-CD3 significantly inhibited tumor growth and prolonged survival in several xenograft mouse models, which was further enhanced by the combination of programmed cell death protein 1 (PD-1) blockade. Mechanistic studies revealed that iRGD-anti-CD3 initiated a transport pathway called vesiculovacuolar organelles in the endothelial cytoplasm to promote T-cell extravasation. CONCLUSION: Altogether, we show that iRGD-anti-CD3 modification is an innovative and bifunctional strategy to overcome major bottlenecks in adoptive cell therapy. Moreover, we demonstrate that combination with PD-1 blockade can further improve antitumor efficacy of iRGD-anti-CD3-modified T cells.

Combination Therapy with iRGD-antiCD3 and PD-1 Blockade Enhances Antitumor Potency of Cord Blood-Derived T Cells.

BACKGROUND: T cell-redirecting bispecific antibodies (BsAbs) are emerging as a potent cancer therapy that crosslinks tumor cells and T cells by simultaneously binding to tumor-associated antigen and CD3ε. However, immune inhibitory molecules can be remarkably upregulated after BsAbs treatment, leading to a suppressive tumor microenvironment and treatment resistance. This can be partially reversed by combination with immune checkpoint inhibitors. In our previous work, we successfully constructed the recombinant protein iRGD-antiCD3 and demonstrated that it promoted antitumor efficacy of transferred T cells by promoting T cell activation and infiltration. METHODS: We detected the levels of both PD-1 and PD-L1 as resistance to iRGD-antiCD3 treatment. Using cord blood-derived T cells, we assessed the activation and effects of iRGD-antiCD3 combined with PD-1 as evidenced by activation markers, Th1/Th2-cytokines, and killing capability against tumor cells in vitro. Moreover, to better mimic the physiological characteristics of in vivo solid tumors, we generated 3D spheroids from target cell lines. Spheroids were stained with a Viability/Cytotoxicity Assay Kit and examined by confocal microscopy to study the in vitro antitumor effect of T cells co-administered with combination iRGD-antiCD3 and PD-1 blockade. The mouse peritoneal metastatic gastric tumor model was employed. The synergistic antitumor effect and safety profiles in vivo were evaluated by tumor and body weight of tumor-bearing mice. RESULTS: We found that expression of both PD-1 and PD-L1 were increased as resistance to iRGD-antiCD3 treatment. We found that PD-1 blockade partially restored T cell activation as evidenced by elevated activation markers, Th1-cytokines, and killing capability against tumor cells in vitro. The combination of PD-1 blockade consistently and significantly increased cord blood-derived T cell cytotoxicity against 3D tumor spheroids. In vivo, we observed synergistic antitumor activity without obvious side effects. CONCLUSION: These results demonstrated that combining iRGD-antiCD3 with PD-1 blockade could further improve antitumor efficacy of T cells, and this strategy holds great potential for the treatment of solid malignancies.

[Corrigendum] Tumor­penetrating peptide fused EGFR single­domain antibody enhances radiation responses following EGFR inhibition in gastric cancer.

Following the publication of the above article, the authors noticed that data shown in certain of the panels in Figs. 4 and 5 were selected incorrectly and presented wrongly in these figures. Essentially, in Fig. 4, the data shown for the Tunel, anti­EGFR­iRGD and Tunel, anti­EGFR­iGRD+IR data panels (i.e., the panels in the third row, columns 2 and 4), were chosen incorrectly, and in Fig. 5, the data panel for the Lung, IR experiment (fourth row, third column) was selected incorrectly. The revised versions of Figs. 4 and 5, featuring all the correct data panels, are shown on the next page. Furthermore, the results were re­analyzed based on the correct data. The errors made in the compilation of these Figures did not affect the overall conclusions reported in the paper. The authors are grateful to the Editor of Oncology Reports for allowing them the opportunity to publish this Corrigendum, and apologize to the readership for any inconvenience caused. [the original article was published in Oncology Reports 40: 1583-1591, 2018; DOI: 10.3892/or.2018.6532].

iRGD synergizes with PD-1 knockout immunotherapy by enhancing lymphocyte infiltration in gastric cancer.

Poor infiltration of activated lymphocytes into tumors represents a fundamental factor limiting the therapeutic effect of adoptive cell immunotherapy. A tumor-penetrating peptide, iRGD, has been widely used to deliver drugs into tumor tissues. In this study, we demonstrate for the first time that iRGD could also facilitate the infiltration of lymphocytes in both 3D tumor spheroids and several xenograft mouse models. In addition, combining iRGD modification with PD-1 knockout lymphocytes reveals a superior anti-tumor efficiency. Mechanistic studies demonstrate that the binding of iRGD to neuropilin-1 results in tyrosine phosphorylation of the endothelial barrier regulator VE-cadherin, which plays a role in the opening of endothelial cell contacts and the promotion of transendothelial lymphocyte migration. In summary, these results demonstrate that iRGD modification could promote tumor-specific lymphocyte infiltration, and thereby overcome the bottleneck associated with adoptive immune cell therapy in solid tumors.

Immune-Mediated Antitumor Effect By VEGFR2 Selective Inhibitor For Gastric Cancer.

BACKGROUND: It was previously reported that targeting vascular epithelial growth factor (VEGF)/VEGFR could modulate the antitumor immunity. VEGFR2 inhibitor YN968D1 is a highly selective VEGFR2 inhibitor and was approved for the treatment of late-stage gastric cancer in 2014, but its role in antitumor immunity remains unknown. MATERIALS AND METHODS: In this study, we investigated the effects of YN968D1 on the function of T cells in vitro by testing the cytotoxicity and cytokine production. Next, we constructed peritoneal dissemination and subcutaneous gastric cancer mouse model to assess the cytotoxicity of YN968D1-treated T cells in vivo, respectively. RESULTS: We found that the use of YN968D1 in CD8+ T cells could reduce the expression levels of inhibitory checkpoints, such as Lag-3, PD-1, and Tim3, escalate the production of IFN-γ and IL-2 and promote the cytotoxicity of T cells dramatically in vitro. The transfer of YN968D1-treated T cells achieved better tumor control compared to DMSO-treated T cells or control in both peritoneal dissemination and subcutaneous gastric cancer mouse models. CONCLUSION: Our results indicate that YN968D1 can enhance the T cell-mediated antitumor immunity.

Neoantigen identification strategies enable personalized immunotherapy in refractory solid tumors.

BACKGROUND: Recent genomic and bioinformatic technological advances have made it possible to dissect the immune response to personalized neoantigens encoded by tumor-specific mutations. However, timely and efficient identification of neoantigens is still one of the major obstacles to using personalized neoantigen-based cancer immunotherapy. METHODS: Two different pipelines of neoantigens identification were established in this study: (1) Clinical grade targeted sequencing was performed in patients with refractory solid tumor, and mutant peptides with high variant allele frequency and predicted high HLA-binding affinity were de novo synthesized. (2) An inventory-shared neoantigen peptide library of common solid tumors was constructed, and patients' hotspot mutations were matched to the neoantigen peptide library. The candidate neoepitopes were identified by recalling memory T-cell responses in vitro. Subsequently, neoantigen-loaded dendritic cell vaccines and neoantigen-reactive T cells were generated for personalized immunotherapy in six patients. RESULTS: Immunogenic neo-epitopes were recognized by autologous T cells in 3 of 4 patients who utilized the de novo synthesis mode and in 6 of 13 patients who performed shared neoantigen peptide library, respectively. A metastatic thymoma patient achieved a complete and durable response beyond 29 months after treatment. Immune-related partial response was observed in another patient with metastatic pancreatic cancer. The remaining four patients achieved the prolonged stabilization of disease with a median PFS of 8.6 months. CONCLUSIONS: The current study provided feasible pipelines for neoantigen identification. Implementing these strategies to individually tailor neoantigens could facilitate the neoantigen-based translational immunotherapy research.TRIAL REGSITRATION. ChiCTR.org ChiCTR-OIC-16010092, ChiCTR-OIC-17011275, ChiCTR-OIC-17011913; ClinicalTrials.gov NCT03171220. FUNDING: This work was funded by grants from the National Key Research and Development Program of China (Grant No. 2017YFC1308900), the National Major Projects for "Major New Drugs Innovation and Development" (Grant No.2018ZX09301048-003), the National Natural Science Foundation of China (Grant No. 81672367, 81572329, 81572601), and the Key Research and Development Program of Jiangsu Province (No. BE2017607).

Tumor­penetrating peptide fused EGFR single­domain antibody enhances radiation responses following EGFR inhibition in gastric cancer.

Radiotherapy has been the primary method for the local control of several types of unresectable tumor, including gastric cancer. Patients with gastric cancer frequently express high levels of epidermal growth factor receptor (EGFR), which have been found to increase following radiotherapy treatment. This provides a basis for the combination of antibodies targeting EGFR and radiotherapy. In our previous study, a protein (anti­EGFR­iRGD) with bispecific targets and high permeability was constructed, and its effects on inhibiting the proliferation of gastric cancer cells was investigated. In the present study, the capacity of anti­EGFR­iRGD to modulate a radiation response was investigated and the specific mechanisms underlying these interactions were evaluated in gastric cancer cell lines and xenografts exhibiting high levels of EGFR. The radioenhancement of anti­EGFR­iRGD was associated with inhibited radiation­induced upregulation of EGFR, inhibited cell proliferation and promotion of cell apoptosis. In addition, anti­EGFR­iRGD appeared to permeate more into the tumor tissue following radiation. These findings indicated that the recombinant protein anti­EGFR­iRGD was a selective and effective radiosensitizer in EGFR­overexpressing gastric cancer cells and xenografts. These results further suggested that anti­EGFR­iRGD is a potential superior EGFR­targeted therapy combined with radiotherapy. Overall, the present study suggested that anti­EGFR­iRGD may be a promising candidate for preclinical and clinical use.

CRISPR-Cas9-mediated disruption of PD-1 on human T cells for adoptive cellular therapies of EBV positive gastric cancer.

The successful use of immune cell checkpoint inhibitors PD-1 and PD-L1, over the past 5 y has raised the concern of using immunotherapy to treat various cancers. Epstein-Barr virus-associated gastric cancer (EBVaGC) exhibits high infiltration of lymphocytes and high amplification of immune-related genes including PD-L1 as distinguished from Epstein-Barr virus-non-associated gastric cancer (EBVnGC). Here, we presume that this PD-1/PD-L1 pathway may hinder the efficacy of adoptive T cell therapy toward EBVaGC. These studies reveal possibility of generating PD-1-disrupted CTL by CRISPR-Cas9 system and demonstrate enhanced immune response of these PD-1-disrupted CTLs to the EBV-LMP2A antigen and superior cytotoxicity to the EBV-positive gastric cancer cell. In addition, when combined with low-dose radiotherapy, these PD-1-disrupted CTLs mediated an impressive antitumor effect in a xenograft mouse model of EBVaGC. Taken together, these studies illustrate PD-1/PD-L1-mediated immune tolerance of EBVaGC and provide a new strategy for targeting immune checkpoints to break the tolerance for the T cell-based adoptive therapy.

Microcystin (-LR) induced testicular cell apoptosis via up-regulating apoptosis-related genes in vivo.

Microcystin-LR (MC-LR) can induce apoptosis of a wide range of tissue cells including testicular cells. The purpose of the study was to find out whether the expression and phosphorylation of p53, Bcl-2 protein family proteins, Cyt c, and caspases were involved in the induction of testicular cell apoptosis by MC-LR in mice. Results showed that following exposure to MC-LR, expression of Bax, caspase 3 and caspase 8 was up-regulated. Significant increases in the phosphorylation of both p53 and Bcl-2 were identified after the administration of MC-LR. The administration of MC-LR also resulted in significant increases of c-myc, c-jun, and c-fos. In conclusion, p53, Bcl-2, Bax, Caspase 3 and Caspase 8 are involved in the regulation of MC-LR-induced apoptosis of testicular cells. The overexpression of c-myc, c-jun and c-fos suggests that MC-LR may have carcinogenic potential for testes.