Salmonella-mediated blood‒brain barrier penetration, tumor homing and tumor microenvironment regulation for enhanced chemo/bacterial glioma therapy

Chemotherapy is an important adjuvant treatment of glioma, while the efficacy is far from satisfactory, due not only to the biological barriers of blood‒brain barrier (BBB) and blood‒tumor barrier (BTB) but also to the intrinsic resistance of glioma cells via multiple survival mechanisms such as up-regulation of P-glycoprotein (P-gp). To address these limitations, we report a bacteria-based drug delivery strategy for BBB/BTB transportation, glioma targeting, and chemo-sensitization. Bacteria selectively colonized into hypoxic tumor region and modulated tumor microenvironment, including macrophages repolarization and neutrophils infiltration. Specifically, tumor migration of neutrophils was employed as hitchhiking delivery of doxorubicin (DOX)-loaded bacterial outer membrane vesicles (OMVs/DOX). By virtue of the surface pathogen-associated molecular patterns derived from native bacteria, OMVs/DOX could be selectively recognized by neutrophils, thus facilitating glioma targeted delivery of drug with significantly enhanced tumor accumulation by 18-fold as compared to the classical passive targeting effect. Moreover, the P-gp expression on tumor cells was silenced by bacteria type III secretion effector to sensitize the efficacy of DOX, resulting in complete tumor eradication with 100% survival of all treated mice. In addition, the colonized bacteria were finally cleared by anti-bacterial activity of DOX to minimize the potential infection risk, and cardiotoxicity of DOX was also avoided, achieving excellent compatibility. This work provides an efficient trans-BBB/BTB drug delivery strategy via cell hitchhiking for enhanced glioma therapy.

Synergistic effects of resveratrol with gemcitabine in pancreatic cancer chemotherapy by inhibiting PARP1 / 西安交通大学学报(医学版)

【Objective】 To investigate the effects of resveratrol on gemcitabine chemotherapy in pancreatic cancer and the possible molecular mechanism. 【Methods】 Gemcitabine resistant cell lines were screened by continuous low concentration increasing induction. High-throughput RNA-seq was used to analyze the differential expression enrichment pathway, COMET assay was used to detect DNA damage, Western blotting was used to detect related pathway indicators, and Chou-Talalay was used to calculate drug combination synergistic index. AutoDock predicts docking targets for small molecules and proteins. 【Results】 DNA damage repair related pathways were activated in drug-resistant cell lines compared with their parents. Resveratrol enhanced the DNA damage effects induced by gemcitabine (P<0.01). Resveratrol inhibited the expression of PARP1, a key molecule of DNA damage repair, and played a synergic effect with gemcitabine (CI<1). Resveratrol has docking targets with the CAT domain of PARP1. 【Conclusion】 Resveratrol can inhibit PARP1, a key molecule of chemotherapy resistance, and has a synergistic effect with gemcitabine in pancreatic cancer chemotherapy.

DNA-PK inhibition by M3814 enhances chemosensitivity in non-small cell lung cancer

A significant proportion of non-small cell lung cancer (NSCLC) patients experience accumulating chemotherapy-related adverse events, motivating the design of chemosensitizating strategies. The main cytotoxic damage induced by chemotherapeutic agents is DNA double-strand breaks (DSB). It is thus conceivable that DNA-dependent protein kinase (DNA-PK) inhibitors which attenuate DNA repair would enhance the anti-tumor effect of chemotherapy. The present study aims to systematically evaluate the efficacy and safety of a novel DNA-PK inhibitor M3814 in synergy with chemotherapies on NSCLC. We identified increased expression of DNA-PK in human NSCLC tissues which was associated with poor prognosis. M3814 potentiated the anti-tumor effect of paclitaxel and etoposide in A549, H460 and H1703 NSCLC cell lines. In the four combinations based on two NSCLC xenograft models and two chemotherapy, we also observed tumor regression at tolerated doses

Achillea biebersteinii extracts suppress angiogenesis and enhance sensitivity to 5-fluorouracil of human colon cancer cells via the PTEN/AKT/mTOR pathway in vitro

To investigate the antiproliferative, anti-angiogenic, and apoptotic effects of extracts of Achillea biebersteinii (ABE) and combined treatments of ABE with 5-fluorouracil (5-FU) on HT-29 cells. Methods: The effects of ABE, 5-FU, and combined treatments on the viability of HT-29 cells were determined by 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Isobologram analysis was used to determine synergism between ABE and 5-FU. The apoptotic and anti-angiogenic effects were determined by cell death detection and human vascular endothelial growth factor ELISA method, respectively. Transcriptional and translational expressions of p53, Bax, Bcl-2, p38 MAPK, Akt, PTEN, and mTOR were also evaluated by real-time PCR and Western blotting analysis. Results: ABE decreased the viability of HT-29 cells in a dosedependent manner. Combined treatment of hexane, chloroform, and methanol extracts of Achillea biebersteinii with 5-FU at IC50 doses decreased the cell viability to 26.0%, 19.1%, and 14.9%, respectively (P0.001). Furthermore, ABE treatment alone and combination with 5-FU, induced apoptosis, significantly downregulated mTOR, Akt, Bcl-2 expression, upregulated p53, Bax, PTEN, p38 MAPK expression, and exhibited anti-angiogenetic effects. Conclusions: Our findings indicate that ABE shows synergism with 5-FU and inhibits the proliferation of HT-29 cells by inducing apoptosis and suppressing angiogenesis, which may provide biological evidence for further use of ABE in the treatment of colorectal cancer.

Achillea biebersteinii extracts suppress angiogenesis and enhance sensitivity to 5-fluorouracil of human colon cancer cells via the PTEN/AKT/mTOR pathway in vitro

Objective: To investigate the antiproliferative, anti-angiogenic, and apoptotic effects of extracts of Achillea biebersteinii (ABE) and combined treatments of ABE with 5-fluorouracil (5-FU) on HT-29 cells.Methods: The effects of ABE, 5-FU, and combined treatments on the viability of HT-29 cells were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Isobologram analysis was used to determine synergism between ABE and 5-FU. The apoptotic and anti-angiogenic effects were determined by cell death detection and human vascular endothelial growth factor ELISA method, respectively. Transcriptional and translational expressions of p53, Bax, Bcl-2, p38 MAPK, Akt, PTEN, and mTOR were also evaluated by real-time PCR and Western blotting analysis. Results: ABE decreased the viability of HT-29 cells in a dose-dependent manner. Combined treatment of hexane, chloroform, and methanol extracts of Achillea biebersteinii with 5-FU at IC50 doses decreased the cell viability to 26.0％, 19.1％, and 14.9％, respectively (P<0.001). Furthermore, ABE treatment alone and combination with 5-FU, induced apoptosis, significantly downregulated mTOR, Akt, Bcl-2 expression, upregulated p53, Bax, PTEN, p38 MAPK expression, and exhibited anti-angiogenetic effects. Conclusions: Our findings indicate that ABE shows synergism with 5-FU and inhibits the proliferation of HT-29 cells by inducing apoptosis and suppressing angiogenesis, which may provide biological evidence for further use of ABE in the treatment of colorectal cancer.

Blocking of methionine aminopeptidase-2 by TNP-470 induces apoptosis and increases chemosensitivity of cholangiocarcinoma

Context: Resistance of cancer cells to chemotherapeutic drugs is a major pitfall of the failure of chemotherapy treatment for cholangiocarcinoma (CCA). A new therapeutic strategy that can improve treatment efficacy is mandatory for CCA patients. Our previous findings demonstrated the overexpression of methionine aminopeptidase-2 (MetAP2) in CCA patients. In addition, supplementation of TNP-470, a MetAP2 inhibitor, significantly inhibited the growth and metastatic activities of CCA cell lines. However, the molecular mechanism of antitumor activity of TNP-470 and the synergistic antitumor activity of TNP-470 combined with chemotherapeutic drugs are still unknown. Aims: The aim of this study is to evaluate the molecular mechanism of anticancer activity and the potential use of TNP-470 as a chemosensitizing agent in CCA cell lines. Materials and Methods: Cell cycle and apoptosis of CCA cell lines were evaluated using flow cytometry with propidium iodide staining. Expression of apoptosis regulatory proteins was measured by Western blotting. The chemosensitizing effect of TNP-470 was determined using combination index. Results: TNP-470 inhibited the growth of CCA cells via induction of apoptosis through activation of the p38-phosphorylation and up- and down-regulation of Bax and Bcl-xL, respectively. Furthermore, TNP-470 significantly enhanced the antitumor activity of 5-fluorouracil, cisplatin, doxorubicin, and gemcitabine. Conclusions: The present results show that TNP-470 could be a potential therapeutic or adjuvant agent for CCA

Nitric oxide-releasing drug delivery systems for overcoming drug resistance in chemotherapy / 药学学报

Chemotherapeutic agents along with other treatments, such as chemotherapy and radiotherapy, have made significant contributions to cancer therapy, however multidrug resistance (MDR) in tumor remains an important developmental barrier to efficient chemotherapy. In recent research, there is increasing evidence that nitric oxide (NO) has the potential to overcome MDR. Unlike other chemosensitizers that ameliorate MDR but are potentially toxic, NO is endogenous and biocompatible molecule, which makes it even more promising as a cancer therapeutic. Nanoparticle-based drug delivery systems not only facilitate the delivery of multiple therapeutic agents, but also promote the avoidance of MDR, which are promising to both efficient delivery of NO and anti-cancer drugs in combination. Therefore, this review will discuss the mechanisms how NO reverse MDR and the recent advances in the application of NO functionalized nanoparticles for anticancer drug delivery.

Roles of physical therapies in chemosensitization of non-small cell lung cancer / 国际肿瘤学杂志

Chemotherapy is an important treatment of non-small cell lung cancer (NSCLC),the efficiency of chemotherapy directly affects the survival rate and living quality of patients.Studies show that physical therapies such as hyperthermia,tumor treating fields,alternating micro-current,hyperbaric oxygen treatment and photodynamic therapy play chemosensitization effects in NSCLC by means of improving the concentrations of chemotherapeutic agents in tumor cells,promoting tumor cell apoptosis,inhibiting the expressions of multidrug resistance gene and protein and other ways.

Evaluación del efecto del tratamiento combinado de mangiferina con cisplatino y 5-fluorouracilo en células CT26. WT y CHO-K1 / Evaluation of combination treatment effect of mangiferin with cisplatin and 5-fluorouracil in CT26. WT and CKO-K1 cells

INTRODUCCIÓN: la mangiferina posee diferentes propiedades farmacológicas, y otras están por ser investigadas, tal como su actividad antitumoral como agente adyuvante a la quimioterapia antineoplásica convencional en la terapia combinada. OBJETIVO: evaluar el efecto antiproliferativo de la mangiferina sola y combinada con concentraciones bajas de agentes quimioterapéuticos. MÉTODOS: las líneas celulares de carcinoma de colon de ratón CT26.WT y normal de ovario de hámster chino CHO-K1, se trataron con mangiferina en combinación con cisplatino y 5-fluorouracilo bajo diferentes esquemas de tratamiento (secuencial y simultáneo), a diferentes concentraciones y tiempos de incubación. La viabilidad celular se determinó por el ensayo de MTT. RESULTADOS: la mangiferina (1-200 µg/mL) no fue citotóxica para ambas líneas celulares. El cotratamiento secuencial con mangiferina (1-200 µg/mL) por 3 h y cisplatino a concentraciones no citotóxicas (1 µM y 5 µM) durante 72 h, mostró un incremento significativo de la muerte celular en CT26.WT, sin inducir incremento significativo de la muerte en células CHO-K1, a concentraciones bajas de ambos compuestos. En el caso de los cotratamientos con mangiferina y 5-fluorouracilo (0,1 µM y 0,5 µM), se incrementó significativamente la muerte celular en los cotratamientos simultáneo por 72 h y secuencial 5-fluorouracilo 72 h y mangiferina 24 h en células CT26.WT; pero solo en este último, no se incrementó significativamente la muerte celular en CHO-K1. CONCLUSIONES: la mangiferina en combinación con concentraciones bajas no citotóxicas de cisplatino y 5-fluorouracilo, promueve la muerte celular e incrementa la citotoxicidad de estos agentes quimioterapéuticos en las condiciones de experimentación realizadas(AU)

INTRODUCTION: mangiferin has several pharmacological properties, but others remain to be deeply explored, such as antitumor activity since it may serve as adjuvant agent in conventional antitumoral chemotherapy in a combined treatment. OBJECTIVE: to evaluate the antiproliferative effect of the use of mangiferin alone and in combination with low concentrations of chemotherapeutic agents. METHODS: the CT26.WT mouse colon carcinoma and the CHO-K1 hamster ovary normal cell lines were treated with mangiferin in combination with cisplatin and 5-fluorouracil in several treatment schedules (sequential and simultaneous), at different concentrations and incubation times. The cell viability was evaluated by MTT assay. RESULTS: mangiferin (1-200 µg/mL) was not cytotoxic in both cell lines. Mangiferin (1-200 µg/mL) for 3h plus cisplatin at not citotoxic concentrations (1 µM and 5 µM) for 72 h in sequential combined treatment showed a significant increase of cell death in CT26.WT, without inducing significant increase of cell death in CHO-K1 cells at low concentrations of both compounds. In the case of combined mangiferina and 5-fluorouracil (0,1 µM and 0,5 µM) treatments, cell death rose in a significant way in simultaneous combined treatments for 72 h whereas sequential combined therapy with 5-fluorouracil for 72 h plus mangiferin for 24 h in CT26.WT cells, a significant rise was not induced in the cell line death of CHO-K1 hamster CONCLUSIONS: mangiferin in combination with low non cytotoxic concentrations of cisplatin and 5-fluorouracil promotes cell death and increases the cytotoxicity of these chemotherapeutic agents in experimental conditions of this study(AU)

RasGAP-derived peptide GAP159 enhances cisplatin-induced cytotoxicity and apoptosis in HCT116 cells

To increase the efficacy of currently used anti-cancer genotoxins, one of the current efforts is to find agents that can sensitize cancer cells to genotoxins so that the efficacious doses of genotoxins can be lowered to reduce deleterious side-effects. In this study, we reported that a synthetic RasGAP-derived peptide GAP159 could enhance the effect of chemotherapeutic agent cisplatin (CDDP) in human colon carcinoma HCT116 cells. Our results showed that GAP159 significantly increased the CDDP-induced cytotoxicity and apoptosis in HCT116 cells. This synergistic effect was associated with the inhibitions of phospho-AKT, phospho-ERK and NF-κB. In mouse colon tumor CT26 animal models, GAP159 combined with CDDP significantly suppressed CT26 tumor growth, and GAP159 alone showed slight inhibitory effect. Our data suggests that co-treatment of GAP159 and chemotherapeutics will become a potential therapeutic strategy for colon cancers.

In vitro modulation of Bcl-2 levels in small cell lung cancer cells: effects on cell viability

Small cell lung cancer (SCLC) is an aggressive disease, representing 15 percent of all cases of lung cancer, has high metastatic potential and low prognosis that urgently demands the development of novel therapeutic approaches. One of the proposed approaches has been the down-regulation of BCL2, with poorly clarified and controversial therapeutic value regarding SCLC. The use of anti-BCL2 small interfering RNA (siRNA) in SCLC has never been reported. The aim of the present study was to select and test the in vitro efficacy of anti-BCL2 siRNA sequences against the protein and mRNA levels of SCLC cells, and their effects on cytotoxicity and chemosensitization. Two anti-BCL2 siRNAs and the anti-BCL2 G3139 oligodeoxynucleotide (ODN) were evaluated in SCLC cells by the simultaneous determination of Bcl-2 and viability using a flow cytometry method recently developed by us in addition to Western blot, real-time reverse-transcription PCR, and cell growth after single and combined treatment with cisplatin. In contrast to previous reports about the use of ODN, a heterogeneous and up to 80 percent sequence-specific Bcl-2 protein knockdown was observed in the SW2, H2171 and H69 SCLC cell lines, although without significant sequence-specific reduction of cell viability, cell growth, or sensitization to cisplatin. Our results question previous data generated with antisense ODN and supporting the present concept of the therapeutic interest in BCL2 silencing per se in SCLC, and support the growing notion of the necessity of a multitargeting molecular approach for the treatment of cancer.

Experiment of advancing chemosensitization of Etoposide by insulin in vitro / 中国临床药理学与治疗学

AIM:To investigate the effects of insulin on drug sensitivity of Etoposide(Vp-16) to MBA-MD-543(human breast cancer cell line) in vitro.METHODS:Insulin was applied directly to the MBA-MD-543 cultured in vitro.The effects of insulin and Vp-16 on the number of viable cell,the total number of cells were assayed by MTT method and cell count.RESULTS: Insulin could induce the cell growth and promote the cell metabolism at the concentration(4.0)-(32.0)(mU?ml~(-1))(8-18 hours).At the condition of same density of cells,the administration of insulin((7.5)(mU?ml~(-1))) before adding Vp-16 in 9-15 h,enhanced the chemocytotoxity of Vp-16((70.09)(?g?ml~(-1))) on human breast cancer cells as indicated by MTT colorimetry.CONCLUSION: Proliferation of human breast cancer cell line can be induced by insulin,and insulin can sensitize MBA-MD-543 to the anticancer activity of Vp-16 in vitro. The key of improving the chemotherapeutic effect is the selection of revulsant occasion and concentration.It is possible to increase the growth and metabolism of cancer cells first so as to enhance the chemosensibility,and then administer chemotherapeutic agents,thus improving their theraeutic effects.

The Effect of IkappaBalpha-SR Gene Transfer on the Sensitivity of Human Lung Cancer Cell Lines to Cisplation and Paclitaxel / 결핵

BACKGROUND: Some chemotherapeutic drugs induce NF-κB activation by degrading the IκBα protein in cancer cells which contributes to anticancer drug resistance. We hypothesized that inhibiting IκBα degradation would block NF-κB activation and result in increased tumor cell mortality in response to chemotherapy. METHODS: The "superrepressor" form of the NF-κB inhibitor was transferred by an adenoviral vector (Ad-IκBα-SR) to the human lung cancer cell lines (NCI H157 and NCI H460). With a MTT assay, the level of sensitization to cisplatin and paclitaxel were measured. To confirm the mechanism, an EMSA and Annexin V assay were performed. RESULTS: EMSA showed that IκBα-SR effectively blocked the NF-κB activation induced by cisplatin. Transduction with Ad-IκBα-SR resulted in an increased sensitivity of the lung cancer cell lines to cisplatin and paclitaxel by a factor of 2~3 in terms of IC50. Annexin-V analysis suggests that this increment in chemosensitivity to cisplatin probably occurs through the induction of apoptosis. CONCLUSION: The blockade of chemotherapeutics induced NF-κB activation by inducing Ad-IκBα-SR, increased apoptosis and increasing the chemosensitivity of the lung cancer cell lines tested, subsequently. Gene transfer of IκBα-SR appears to be a new therapeutic strategy of chemosensitization in lung cancer.

Research on the Effect of Kanglaite Injection on Enchancing Lung Cancer Cell' s Sensitivity to TXT Injection / 中药新药与临床药理

Objective To investigte the inhibit effects of drug combination of Kanglaite injection(KLT) and TXT on human pulmonary epithelial cells(95D) in vitro,and to find the best time of combination.Method 95D cell growth inhibition was measured with MTT assay.Results Various concentration of KLT and TXT could inhibit the proliferation of 95D cell,and KLT could enchance the sensiti vity of 95D cell to TXT(P

Restoration of Wild - type p53 Induces Chemo-sensitization in the Gastric Cancer Cell Line with Mutant p53 / 대한암학회지

PURPOSE: It has been theorized that p53 may be involved in the sensitivity to chemotherapeutic agents. We evaluated the chemosensitivity of wild p53 after transduction into gastric cancer cell lines with mutant p53. MATERIALS AND METHODS: YCC-3(parent cell line with mutant p53), YCC-3v(parent cell line transduced with vector alone) and YCC-3C3(clone with wild p53) cell lines were used in this study. p53 protein expression was measured by ELISA assay. Tumorigenicity and drug sensitivity were evaluated by soft agar and proliferation assay, respectively. Cell cycle analysis was performed by flowcytometry. Telomerase activity was measured by TRAP assay and terminal restriction fragment(TRF) length was measured after Southern blot analysis. RESULTS: Even though p53 production from the YCC-3C3 cell line was three times higher than those of YCC-3 and YCC-3v cell lines, the cell cycle was the same in these three cell lines. In the YCC-3C3 cell line, drug sensitivity to etoposide and cisplatin was increased when we compared it to those of the YCC-3v cell line(etoposide, 50% versus 83%; cisplatin, 67% versus 83%). However, there was no chemo-sensitization effect with vincristine, vinblastine and carboplatin. After exposure to cisplatin, a G0/G1 check-point effect was found in the YCC-3C3 cell line, but not in the YCC-3v cell line. No differences were found in telomerase activity, TRFs length or DNA fragmentation between the YCC-3v and YCC-3C3 cell lines after cisplatin treatment. CONCLUSION: Wild-type p53 gene transduction in the gastric cancer cell line induced sensitization to the cytotoxicity of etoposide and cisplatin. This suggests the possible application of combined chemo-gene therapy with an EP regimen and wild-type p53 in gastric cancer patients with p53 mutation.

Anti-tumor Effects of Growth Factor Inhibitors and Anti-metastatic Agents in Human Gastric Cancer Cell Lines / 대한암학회지

PURPOSE: For tumor growth, invasion and metastasis, a cascade of linked sequential biological events is essential; overproduction of growth factors, activation of proteolytic enzymes, induction of tumor angiogenesis, and enhanced tumor cell motility and attachment. We tried to test whether the biological therapy against the biological targets can modulate the specific biological characteristics, and furthermore increased anti-tumor effects can be induced when the biological therapy and cytotoxic chemotherapy were combined. MATERIALS AND METHODS: YCC-1, 2, 3, 7, and AGS human gastric cancer cell lines were used in these studies. Pentosan polysulfate (PPS) as a heparin-binding growth factor (HBGF) inhibitor, Tranexamic acid as a plasmin inhibitor, Adriamycin as a chemotherapeutic agent, were selected. The methods were Northern blot analysis for the detection of Midkine (MK) expression, soft agar assay for autocrine tumorigenicity. The expression of uPA, PAI-1 was determined by ELISA, while the MMPs activities were evaluated by zymography. The effects of each drug on tumorigenicity and tumor cell proliferation were evaluated by soft agar assay and cell proliferation assay, respectively. RESULTS: YCC-3, 7, AGS cell lines expressed MK mRNA, whereas YCC-1, 2 did not. YCC-2 cell line showed increased expression of uPA and MMP activities. Only MK expressing YCC-3 and 7 cell lines showed the tumorigenicity. PPS suppressed the colony forming activities as much as Adriamycin did (PPS; 8~24%, Adriamycin; 12~40%), but it showed only cytostatic effects in cell proliferation assay (PPS; 60~103%, Adriamycin; 22~97%). When PPS was combined with Adriamycin on the Adriamycin resistant, MK expressing YCC-7 cell line, the growth inhibition rate increased up to 84%, while that of PPS or Adriamycin single treatment was 40%, 22%, respectively (p=0.001). CONCLUSION: The modulation of specific biological targets can induce the anti-tumor effects. This suggests the possible clinical application of biological therapy in gastric cancer.

Chemosensitization to adriamycin by cyclosporin A and verapamil in human retinoblastoma cell lines

The chemosensitizing effects of cyclosporin A and verapamil on the cytotoxicity of adriamycin were investigated using MTT assay against two human retinoblastoma cell lines, Y79 and WERI-Rb-1. Y79 and WERI-Rb-1 were totally resistant to doses up to 5.0 micrograms/ml of verapamil. Cyclosporin A inhibited the survival of Y79 and WERI-Rb-1 dose-dependently, however, the maximum inhibition at the highest concentration tested (5.0 micrograms/ml) was less than 50% (% survival at 5.0 micrograms/ml of cyclosporin A: 65.6% and 66.9% in Y79 and WERI-Rb-1, respectively). Combination of cyclosporin A and verapamil did not further inhibit the survival of Y79 and WERI-Rb-1 compared with cyclosporin A alone. Adramycin inhibited the survival of Y79 and WERI-Rb-1 dose-dependently. The chemosensitizing effects of cyclosporin A and verapamil on the cytotoxicity of adriamycin were evaluated in terms of sensitizing index (SI: the ratio of IC50 to adriamycin alone to IC50 to adriamycin in the presence of cyclosporin A and/or verapamil). Cyclosporin A significantly enhanced SI and the addition of verapamil enhanced SI further: SI values at 5.0 micrograms/ml of cyclosporin A, 5.0 micrograms/ml of cyclosporin A plus 1.5 micrograms/ml of cyclosporin A plus 1.5 micrograms/ml of verapamil, 5.0 micrograms/ml of cyclosporin A plus 3.0 micrograms/ml of verapamil were 2.0, 2.6 and 2.8 in Y79 and 2.6, 5.8 and 9.7 in WERI-Rb-1, respectively. These results suggest that cyclosporin A and verapamil are promising chemosensitizers to adriamycin in the treatment of retinoblastoma.