Mechanism of 5-fluorouracil required resistance in human hepatocellular carcinoma cell line Bel7402

A minimalist multifunctional nano-prodrug for drug resistance reverse and integration with PD-L1 mAb for enhanced immunotherapy of hepatocellular carcinoma

Clinical treatment of hepatocellular carcinoma (HCC) with 5-fluorouracil (5-FU), the primary anticancer agent, remains unsatisfactory due to the glutathione (GSH)-associated drug resistance and immunosuppressive microenvironment of HCC. To develop a facile yet robust strategy to overcome 5-FU resistance for enhanced immunotherapy treatment of HCC via all dimensional GSH exhaustion, we report in this study construction of a minimalist prodrug consisting of 5-FU linked to an indoleamine-(2,3)-dioxygenase (IDO) inhibitor (IND) via a disulfide bridge, FU-SS-IND that can further self-assemble into stabilized nanoparticles, FU-SS-IND NPs. Specifically, besides the disulfide linker-induced GSH exhaustion, IND inhibits GSH biosynthesis and enhances the effector function of T cells for turning a "cold" tumor to a "hot" one, which synergistically achieving a tumor inhibition rate (TIR) of 92.5% in a 5-FU resistant mice model. Most importantly, FU-SS-IND NPs could upregulate programmed death ligand 1 (PD-L1) expression on the surface of tumor cells, which enables facile combination with immune checkpoint blockade (ICB) for a ultimate prolonged survival lifetime of 5-FU-resistant tumors-bearing mice. Overall, the minimalist bioreducible nano-prodrug developed herein demonstrates great translatable potential for efficiently reversing drug resistance and enhancing immunotherapy of HCC.

pH/H2O2 Cascade-Responsive Nanoparticles of Lipid-Like Prodrugs through Dynamic-Covalent and Coordination Interactions for Chemotherapy

Traditional lipid nanoparticles (LNPs) suffer from low drug loading capacity (DLC), weak stability, and lack of responsiveness. Conventional approaches to address these issues involve the synthesis of lipid-prodrug by incorporating responsive covalent linkers. However, such approaches often result in suboptimal sensitivity for drug release and undermine therapeutic effectiveness. Herein, the study reports a fundamentally different concept for designing lipid-like prodrugs through boron-nitrogen (B-N) coordination and dynamic covalent interaction. The 5-fluorouracil-based lipid-like prodrugs, featuring a borate ester consisting of a glycerophosphoryl choline head and a boronic acid-modified 5Fu/dodecanamine complex tail, are used to prepare pH/H2O2 cascade-responsive LNPs (5Fu-LNPs). The 5Fu-LNPs exhibit enhanced DLC and stability in a neutral physiological environment due to the B-N coordination and enhanced hydrophobicity. In tumors, acidic pH triggers the dissociation of B-N coordination to release prodrugs, which further responds to low H2O2 concentrations to release drugs, showcasing a potent pH/H2O2-cascade-responsive property. Importantly, 5Fu-LNPs demonstrate greater antitumor efficiency and lower toxicity compared to the commercial 5Fu. These results highlight 5Fu-LNPs as a safer and more effective alternative to chemotherapy. This work presents a unique LNP fabrication strategy that can overcome the limitations of conventional LNPs and broaden the range of intelligent nanomaterial preparation techniques.

Interplay of autophagy and cancer stem cells in hepatocellular carcinoma

Liver cancer is the sixth most common cancer and the fourth leading cause of cancer deaths in the world. The most common type of liver cancers is hepatocellular carcinoma (HCC). Autophagy is the cellular digestion of harmful components by sequestering the waste products into autophagosomes followed by lysosomal degradation for the maintenance of cellular homeostasis. The impairment of autophagy is highly associated with the development and progression of HCC although autophagy may be involved in tumour-suppressing cellular events. In regards to its protecting role, autophagy also shelters the cells from anoikis- a programmed cell death in anchorage-dependent cells detached from the surrounding extracellular matrix which facilitates metastasis in HCC. Liver cancer stem cells (LCSCs) have the ability for self-renewal and differentiation and are associated with the development and progression of HCC by regulating stemness, resistance and angiogenesis. Interestingly, autophagy is also known to regulate normal stem cells by promoting cellular survival and differentiation and maintaining cellular homeostasis. In this review, we discuss the basal autophagic mechanisms and double-faceted roles of autophagy as both tumour suppressor and tumour promoter in HCC, as well as its association with and contribution to self-renewal and differentiation of LCSCs.

Synergistic Antitumor Effect of 5-Fluorouracil Combined with Constituents from Pleurospermum lindleyanum in Hepatocellular Carcinoma SMMC-7721 Cells

BACKGROUND

A Chinese folk medicine plant Pleurospermum lindleyanum possesses pharmacological activities of heat-clearing, detoxifying and preventing from hepatopathy, coronary heart disease, hypertension, and high altitude sickness. We isolated and characterized its constituents to investigate its synergistic effects against human hepatoma SMMC-7721 cells.

OBJECTIVE

The aim of this study was to explore the synergistic anti-cancer activities of isolates from P. lindleyanum with 5-FU on hepatoma SMMC-7721 cells in vitro and their primary mechanisms.

METHODS

Sequential chromatographic techniques were conducted for the isolation studies. The isolate's structures were established by spectroscopic analysis as well as X-ray crystallographic diffraction. Growth inhibition was detected by MTT assay. The isobologram method was used to assess the effect of drug combinations. Flow cytometry and western blot were used to examine apoptosis and protein expression.

RESULTS

A new coumarin (16), along with sixteen known compounds, were isolated from the whole plant of P. lindleyanum and their structures were elucidated by spectroscopic methods. Four coumarins (2, 3, 5, and 16), two flavonoids (8 and 9) and three phytosterols and triterpenes (12-14) were found to synergistically enhance the inhibitory effect of 5-FU against SMMC-7721 cells. Among them, compounds 3 and 16 exhibited the best synergistic effects with IC50 of 5-FU reduced by 16-fold and 22-fold possessing the minimum Combination Index (CI) 0.34 and 0.27. The mechanism of action of combinations might be through synergistic arresting for the cell cycle at G1 phases and the induction of apoptosis. Moreover, western blotting and molecular docking revealed that compounds 3 or 5 might promote 5-FU-induced apoptosis by regulating the expression of Caspase 9 and PARP.

CONCLUSION

Constituents from P. lindleyanum may improve the treatment effectiveness of 5-FU against hepatocellular carcinoma cells.

5-FU resistant EMT-like pancreatic cancer cells are hypersensitive to photochemical internalization of the novel endoglin-targeting immunotoxin CD105-saporin

BACKGROUND

Development of resistance to 5-fluorouracil (5-FU) is a major problem in treatment of various cancers including pancreatic cancer. In this study, we reveal important resistance mechanisms and photochemical strategies to overcome 5-FU resistance in pancreatic adenocarcinoma.

METHODS

5-FU resistant (5-FUR), epithelial-to-mesenchymal-like sub-clones of the wild type pancreatic cancer cell line Panc03.27 were previously generated in our lab. We investigated the cytotoxic effect of the endosomal/lysosomal-localizing photosensitizer TPCS2a (fimaporfin) combined with light (photochemical treatment, PCT) using MTS viability assay, and used fluorescence microscopy to show localization of TPCS2a and to investigate the effect of photodamage of lysosomes. Flow cytometric analysis was performed to investigate uptake of photosensitizer and to assess intracellular ROS levels. Expression and localization of LAMP1 was assessed using RT-qPCR, western blotting, and structured illumination microscopy. MTS viability assay was used to assess the effect of combinations of 5-FU, chloroquine (CQ), and photochemical treatment. Expression of CD105 was investigated using RT-qPCR, western blotting, flow cytometry, and fluorescence microscopy, and co-localization of TPCS2a and anti-CD105-saporin was assessed using microscopy. Lastly, the MTS assay was used to investigate cytotoxic effects of photochemical internalization (PCI) of the anti-CD105-immunotoxin.

RESULTS

The 5-FUR cell lines display hypersensitivity to PCT, which was linked to increased uptake of TPCS2a, altered lysosomal distribution, lysosomal photodamage and increased expression of the lysosomal marker LAMP-1 in the 5-FUR cells. We show that inhibition of autophagy induced by either chloroquine or lysosomal photodamage increases the sensitivity to 5-FU in the resistant cells. The three 5-FUR sub-clones overexpress Endoglin (CD105). Treatment with the immunotoxin anti-CD105-saporin alone significantly reduced the viability of the CD105-expressing 5-FUR cells, whereas little effect was seen in the CD105-negative non-resistant parental cancer cell lines. Strikingly, using the intracellular drug delivery method photochemical internalization (PCI) by combining light-controlled activation of the TPCS2a with nanomolar levels of CD105-saporin resulted in strong cytotoxic effects in the 5-FUR cell population.

CONCLUSION

Our findings suggested that autophagy is an important resistance mechanism against the chemotherapeutic drug 5-FU in pancreatic cancer cells, and that inhibition of the autophagy process, either by CQ or lysosomal photodamage, can contribute to increased sensitivity to 5-FU. For the first time, we demonstrate the promise of PCI-based targeting of CD105 in site-specific elimination of 5-FU resistant pancreatic cancer cells in vitro. In conclusion, PCI-based targeting of CD105 may represent a potent anticancer strategy and should be further evaluated in pre-clinical models.

Aminopeptidase N inhibitor 4cc synergizes antitumor effects of 5-fluorouracil on human liver cancer cells through ROS-dependent CD13 inhibition

Aminopeptidase N (APN, also known as CD13) is involved in cellular processes of various types of tumors and a potential anti-cancer therapeutic target. Here, we report the effect of an APN inhibitor 4cc in enhancing sensitivity of hepatocellular carcinoma (HCC) cell lines and xenograft model in response to 5-fluorouracil (5-FU) in vivo and in vitro. The treatment of the combination of 4cc with 5-FU, compared to the combination of bestain with 5-FU, markedly suppressed cell growth and induced apoptosis of HCC cells, accompanying the increase in the level of reactive oxygen species (ROS) and followed by a decrease in the mitochondrial membrane potential (ΔΨM). Furthermore, the combination of 4cc and 5-FU showed a significant inhibitory effect on the growth of HCC xenograft tumors. In addition, following the treatment of 4cc, APN activity and clonogenic formation and the number of CD13-positive cells in PLC/PRF/5 cells were significantly decreased, suggesting that 4cc may also inhibit liver cancer stem cells by CD13 inhibition. These results showed that the APN inhibitor 4cc synergizes antitumor effects of 5-FU on human liver cancer cells via ROS-mediated drug resistance inhibition and concurrent activation of the mitochondrial pathways of apoptosis.

Liposome-mediated induction of apoptosis of human hepatoma cells by c-myc antisense phosphorothioate oligodeoxynucleotide and 5-fluorouracil

BACKGROUND

The aim of this study was to investigate the effect of a c-myc antisense oligodeoxynucleotide and 5-fluorouracil on the expression of c-myc, invasion and proliferation of HEPG-2 liver cancer cells.

MATERIALS AND METHODS

HEPG-2 cells were treated with lipiosome-mediated c-myc ADSON and 5-fluorouracil. The proliferation inhibition rate and invasion were measured by MTT and invasion assay, respectively. Cell apoptosis was detected by flow cytometry and expression of c-myc by RT-PCR and immunohistochemistry.

RESULTS

The proliferation inhibition rate was significantly higher in the antisense oligodeoxynucleotide added-5-fluorouracil group than single antisense oligodeoxynucleotide or 5-fluorouracil group (p<0.05). G0/G1 cells in the antisense oligodeoxynucleotide group and S cells in the 5-fluorouracil groups were significantly increased than that in the control group, respectively (P<0.01). The amplification strips of PCR products in 5-FU, ASODN and combination groups were significantly weaker than that in the control group (P<0.01). The percentage of c-myc-protein- positive cells were significantly lower in antisense oligodeoxynucleotide, 5-fluorouracil and combination groups than that in the control group (P<0.01).

CONCLUSIONS

A liposome-mediated c-myc antisense oligodeoxynucleotide and 5-fluorouracil can inhibit the proliferation and invasion of liver cancer cells by reducing the expression of c-myc. A c-myc antisense oligodeoxynucleotide can increase the sensitivity of liver cancer cells to 5-fluorouracil and decrease the dosage of the agent necessary for efficacy, providing an experimental basis for the clinical therapy of liver cancer.

Piper betle leaf extract enhances the cytotoxicity effect of 5-fluorouracil in inhibiting the growth of HT29 and HCT116 colon cancer cells

OBJECTIVE

The combination effect of Piper betle (PB) and 5-fluorouracil (5-FU) in enhancing the cytotoxic potential of 5-FU in inhibiting the growth of colon cancer cells was investigated.

METHODS

HT29 and HCT116 cells were subjected to 5-FU or PB treatment. 5-FU and PB were then combined and their effects on both cell lines were observed after 24 h of treatment. PB-5-FU interaction was elucidated by isobologram analysis. Apoptosis features of the treated cells were revealed by annexin V/PI stain. High-performance liquid chromatography (HPLC) was performed to exclude any possible chemical interaction between the compounds.

RESULTS

In the presence of PB extract, the cytotoxicity of 5-FU was observed at a lower dose (IC50 12.5 µmol/L) and a shorter time (24 h) in both cell lines. Both cell lines treated with 5-FU or PB alone induced a greater apoptosis effect compared with the combination treatment. Isobologram analysis indicated that PB and 5-FU interacted synergistically and antagonistically in inhibiting the growth of HT29 and HCT116 cells, respectively.

CONCLUSIONS

In the presence of PB, a lower dosage of 5-FU is required to achieve the maximum drug effect in inhibiting the growth of HT29 cells. However, PB did not significantly reduce 5-FU dosage in HCT116 cells. Our result showed that this interaction may not solely contribute to the apoptosis pathway.

Histone acetyltransferase PCAF accelerates apoptosis by repressing a GLI1/BCL2/BAX axis in hepatocellular carcinoma

P300/CBP-associated factor (PCAF), a histone acetyltransferase (HAT), has been found to regulate numerous cell signaling pathways controlling cell fate by acetylating both histone and non-histone proteins. We previously reported that PCAF upregulates cell apoptosis by inactivating Serine/Threonine Protein Kinase 1 (AKT1) signaling and consequently inhibits hepatocellular carcinoma (HCC) cell growth. Here, we show that PCAF can directly acetylate cytoplasmic GLI1 protein at lysine 518, preventing its nuclear translocation and promoter occupancy, and consequently suppressing Hedgehog (Hh) signaling in HCC. Further, our results show that GLI1 can increase Bcl-2 expression and downregulate BAX. Interestingly, forced expression of PCAF reduced Bcl-2 expression, upregulated BAX and repressed cell apoptosis. Further, we provide evidence that knockdown of GLI1 abrogates the inhibitory effect of PCAF on the growth of HCC in vitro. PCAF was also found to sensitize HCC cells to 5-fluorouracil (5-FU) treatment by regulating GLI1/Bcl-2/BAX axis-dependent apoptosis. In vivo experiments also confirmed the regulatory effect of PCAF on the GLI1/Bcl-2/BAX axis and its synergistic antitumor effects with 5-FU. Gene expression microarray studies showed that PCAF was downregulated in HCC tissues compared with adjacent liver tissues and that PCAF expression was significantly associated with longer overall survival and recurrence-free survival after surgery. Together, these results show that PCAF can induce cell apoptosis by modulating a GLI1/Bcl-2/BAX axis that in turn suppresses HCC progression, and suggest that 5-FU may exert a stronger anti-tumor effect in patients with PCAF expression in HCC tumors.

The role of C/EBP-β LIP in multidrug resistance

BACKGROUND

Chemotherapy triggers endoplasmic reticulum (ER) stress, which in turn regulates levels of the active (LAP) and the natural dominant-negative (LIP) forms of the transcription factor C/EBP-β. LAP upregulates and LIP downregulates the multidrug resistance (MDR) protein P-glycoprotein (Pgp), but it is not known how critical is their role in establishing MDR.

METHODS

Cell viability was quantitated by crystal violet staining and measuring absorbance at 540nm. Expression of various proteins was determined by immunoblotting. mRNA levels were determined by quantitative reverse transcriptase polymerase chain reaction (RT-PCR). LIP and LAP were overexpressed using expression plasmids followed by selection with blasticidin. Tumor cells expressing doxycycline-inducible LIP were orthotopically implanted in mice (n = 15 mice per group), and tumor size was measured daily by caliper. Tumor sections were stained with hematoxylin and eosin and immunostained for Pgp, proliferation, and ER stress markers.

RESULTS

MDR cells do not express basal, chemotherapy-triggered, or ER stress-triggered LIP and fail to activate the CHOP-caspase-3 death-triggering axis upon ER stress or chemotherapy challenge. Overexpression of LIP reversed the MDR phenotype in vitro and in tumors implanted in mice. LIP was undetectable in MDR cells, probably due to its ubiquitination, which was 3.56-fold higher, resulting in lysosomal and proteasomal degradation of LIP.

CONCLUSIONS

Spontaneous and drug-selected MDR cells lack LIP, which is eliminated by ubiquitin-mediated degradation. Loss of LIP drives MDR not only by increasing Pgp expression but also by a two-fold attenuation of ER stress-triggered cell death.

In vitro characterization of stem cell-like properties of drug-resistant colon cancer subline

The objective of this study was to investigate the stem cell-like properties of drug-resistant colon cancer cells. Oxaliplatin was used to induce the drug-resistant subline of HCT116(p53+/+) cell line. The stem cell-like characteristics of the drug-resistant subline were assayed for the proliferation capacity, cell cycle, adhesion, invasion, multiple drug resistance, and clone sphere formation capacity. The expression of ABCG2 (ATP-binding cassette superfamily G member 2) and "stemness" indicators SOX2 (SRY-related HMG box-containing transcription factor-2) and OCT4 (octamer-binding transcription factor 4) was determined by Western blot. We established the HCT116(p53+/+)-oxaliplatin subline (HCT116(p53+/+)OXA), which was resistant to oxaliplatin with a resistance index (RI) of 3.03 ± 0.14. The HCT116(p53+/+)OXA was also resistant to Taxol, showing lower proliferation, higher adhesion and invasion ability, greater proportion of G0/G1 phase, and higher sphere-forming capacity than its parental cells. SOX2, OCT4, and ABCG2 were expressed at higher levels in drug-resistant cells than in their parental cells. We verified that the HCT116(p53+/+)OXA was enriched with cancer stem cell properties and provided an ideal cell model for drug-resistance study.

The synergistic in vitro and in vivo antitumor effect of combination therapy with salinomycin and 5-fluorouracil against hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the few cancers in which a continuous increase in incidence has been observed over several years. Drug resistance is a major problem in the treatment of HCC. In the present study, we used salinomycin (Sal) and 5-fluorouracil (5-FU) combination therapy on HCC cell lines Huh7, LM3 and SMMC-7721 and nude mice subcutaneously tumor model to study whether Sal could increase the sensitivity of hepatoma cells to the traditional chemotherapeutic agent such as 5-FU. The combination of Sal and 5-FU resulted in a synergistic antitumor effect against liver tumors both in vitro and in vivo. Sal reversed the 5-FU-induced increase in CD133(+) EPCAM(+) cells, epithelial–mesenchymal transition and activation of the Wnt/β-catenin signaling pathway. The combination of Sal and 5-FU may provide us with a new approach to reverse drug resistant for the treatment of patients with HCC.

Priming cancer cells for drug resistance: role of the fibroblast niche

Conventional and targeted chemotherapies remain integral strategies to treat solid tumors. Despite the large number of anti-cancer drugs available, chemotherapy does not completely eradicate disease. Disease recurrence and the growth of drug resistant tumors remain significant problems in anti-cancer treatment. To develop more effective treatment strategies, it is important to understand the underlying cellular and molecular mechanisms of drug resistance. It is generally accepted that cancer cells do not function alone, but evolve through interactions with the surrounding tumor microenvironment. As key cellular components of the tumor microenvironment, fibroblasts regulate the growth and progression of many solid tumors. Emerging studies demonstrate that fibroblasts secrete a multitude of factors that enable cancer cells to become drug resistant. This review will explore how fibroblast secretion of soluble factors act on cancer cells to enhance cancer cell survival and cancer stem cell renewal, contributing to the development of drug resistant cancer.

The noncytotoxic dose of sorafenib sensitizes Bel-7402/5-FU cells to 5-FU by down-regulating 5-FU-induced Nrf2 expression

BACKGROUND

Acquired resistance to 5-fluorouracil (5-FU) is a serious therapeutic obstacle in advanced hepatocellular carcinoma (HCC) patients.

AIM

To investigate whether nuclear factor erythroid 2-related factor 2 (Nrf2) was associated with drug resistance in 5-FU resistant Bel-7402 (Bel-7402/5-FU) cells, and if sorafenib, an oral multikinase inhibitor targeting the tumor and vasculature, could reverse drug resistance in Bel-7402/5-FU cells at the noncytotoxic dosage.

METHODS

We used MTT to detect the resistance reversal activity of sorafenib, compared Nrf2 expression in various conditions by western blot and qRT-PCR, and analyzed subcellular localization of Nrf2 by immunofluorescence.

RESULTS

The endogenous expression of Nrf2 in Bel-7402/5-FU cells was similar to that observed in Bel-7402 cells. However, Nrf2 expression levels were increased by 5-FU treatment in Bel-7402/5-FU cells higher than that in Bel-7402 cells, which is to highlight the Nrf2 contribution to the enhanced resistance of Bel-7402/5-FU cells to 5-FU. Moreover, intracellular Nrf2 protein level was significantly down-regulated by Nrf2-shRNA in Bel-7402/5-FU cells, resulting in partial reversal of 5-FU resistance. Sorafenib down-regulated the increased expression of Nrf2 induced by 5-FU treatment and partly reversed 5-FU resistance in Bel-7402/5-FU cells.

CONCLUSIONS

These results suggested that more sensitive cell defense mediated by Nrf2 was associated with drug resistance of Bel-7402/5-FU cells. Sorafenib reversed drug resistance, and its reversal mechanism might be due to the suppression of Nrf2 expression induced by 5-FU, indicating the feasibility of using Nrf2 inhibitors to increase efficacy of chemotherapeutic drugs in HCC patients.

Changes in intracellular redox status influence multidrug resistance in gastric adenocarcinoma cells

Multidrug resistance (MDR) to chemotherapeutic agents is a major obstacle for the treatment of various types of cancers. The exact mechanism of MDR has not yet been fully clarified, although it has been frequently associated with the variation of intracellular redox status. The levels of intracellular glutathione (GSH) are considered to play a vital role in the regulation of the intracellular redox status. In our study, we investigated the effects of buthionine sulfoximine (BSO), an inhibitor of GSH biosynthesis, and NAC, a cysteine source for GSH synthesis, on sensitive gastric adenocarcinoma cells (SGC7901) and cisplatin-resistant SGC7901/DDP cells using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The two cell lines were pretreated with various non-toxic concentrations of BSO for 24 h and combined with fluorouracil (5-FU) or mitomycin (MMC) in the presence or absence of NAC before culturing further. After various treatments, the IC(50) values of MMC and 5-FU were calculated and intracellular GSH levels were measured using the glutathione reductase/5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) recycling assay without anticancer drug stimulation under the same microenvironments. The study demonstrated that BSO increased the sensitivity of the cells to chemotherapeutics while NAC exhibited the reverse effect, particularly in drug-resistant cells. It is, therefore, possible that changes in intracellular GSH levels affect the chemosensitivity of the resistant cells to a greater extent than that of their parent cells. This study indicates that variation in the intracellular redox status may be closely correlated with MDR and may provide a valuable basic strategy for anticancer therapy.

Opsin3 sensitizes hepatocellular carcinoma cells to 5-fluorouracil treatment by regulating the apoptotic pathway

Hepatocellular carcinoma (HCC) is the third most common cancer worldwide, causing over 0.5 million deaths per year, with approximately half of these in China. Chemotherapy is the optimal treatment for patients with advanced HCC, although chemoresistance has become a significant obstacle to successful anti-cancer therapy. The expression of opsin3 (OPN3), also called encephalopsin or panopsin, is lower in 5-fluorouracil (5-FU)-resistant Bel7402(5-FU) cells compared to 5-FU-sensitive Bel7402 cells. To explore the role of OPN3 in 5-FU resistance, OPN3 overexpressing (Bel7402(5-FU)-OPN3) and knockdown (Bel7402-RNAi-OPN3) cell lines were generated. Bel7402(5-FU)-OPN3 cells were more sensitive to 5-FU treatment than controls, while OPN3 knockdown resulted in a significant increase in 5-FU resistance. This result was replicated in a second HCC cell line, HepG2. Further investigation of the mechanism revealed that decreased OPN3 levels in Bel7402(5-FU) cells activated the anti-apoptotic pathway through increasing phospho-Akt and the Bcl2/Bax ratio, while overexpression of OPN3 inactivated this pathway. Taken together, these results suggest that OPN3 depletion is involved in 5-FU resistance, and that therapeutic strategies targeting OPN3 may improve HCC sensitivity to chemotherapy.

Reversal effect of Tween-20 on multidrug resistance in tumor cells in vitro

Multidrug resistance (MDR) is a major barrier for chemotherapy of many cancers. Non-ionic surfactants have great potential to reverse the MDR by preventing onset or delay progression of the carcinogenic process. However, the role of Tween-20 in the development of MDR remains unknown. The aim of this study was to explore the reversal effect and potential mechanism of Tween-20 on tumor cells in vitro. Alamar Blue assay was used to examine the reversal index of Tween-20 to vincristine (VCR), doxorubicin (DOX) and 5-fluorouracil (5-FU) in KBv200, HepG2/R and Bel-7402/5-FU, respectively. Morphological change was determined by Gimsa and Hoechst 33258 staining. The acumulation of DOX was confirmed by spectrofluorimetric assay. Cell cycle analysis was performed using flow cytometry. The mRNA and protein expression levels of MDR were assessed by semiquantitative RT-PCR and dot blot, respectively. The results showed that Tween-20 at concentrations of 0.0025%, 0.005%, 0.01% had little cytotoxicity. When combined with the cancer drugs, it significantly promoted the sensitivity of MDR cells. Fluorescence staining confirmed that the percentage of apoptotic cell increased when combined with Tween-20. This notion was further supported by the observation that Tween-20 treatment potentiated VIN-induced G2/M arrest of the cell cycle. Furthermore, Tween-20 treatment increased significantly intracellular accumulation of DOX. RT-PCR and dot blot revealed that Tween-20 could downregulate the expression of MDR and P-glycoprotein. Low concentrations of Tween-20 can efficiently reverse the multidrug resistance phenotype by enhancing accumulation of the anticancer drugs. The potential mechanism may be via inhibiting the multidrug-resistant gene expression.

Suicidal gene therapy in the effective control of primary human hepatocellular carcinoma as monitored by noninvasive bioimaging

Hepatocellular carcinoma (HCC) is usually refractory to the available treatments. For cancer gene therapy purposes, real-time imaging of therapeutic gene expression is of great importance because there are multiple factors that modulate the therapeutic gene expression in a complex tumor microenvironment. As a consequence, multiple doses of therapeutic viral vectors may be required for improved efficacy. In the present study, the luciferase reporter gene and the yeast cytosine deaminase (yCD) genes were bicistronically expressed using the foot-and-mouth disease virus 2A peptide under the regulation of the cytomegalovirus (CMV) promoter. The effectiveness of the yCD/5-FC (5-fluorocytosine) killing efficacy mediated by the herpes simplex virus type 1 (HSV-1) amplicon viral vector was shown using HCC and non-HCC cell lines in vitro. In addition, in vivo experiment also showed tumor regression of a primary HCC 26-1004 tumor xenograft in tumor expressing high levels of the yCD gene (as determined by noninvasive imaging) after intratumoral injection of 1.5 × 10(6) TU HGCX-L2C HSV-1 amplicon viral vector and 5-FC administration. The HSV-1 amplicon viral vector coupled with the yCD/5-FC prodrug activated suicide gene could potentially be of use in clinical gene therapy for HCC.

Syl611, a novel semisynthetic taxane derivative, reverses multidrug resistance by p-glycoprotein inhibition and facilitating inward transmembrane action

PURPOSE

To investigate the reversal mechanisms of a novel semisynthetic taxane derivative, Syl611. Syl611 is a structurally modified compound from Sinenxan A, and the chemical structure is entirely new. It was found to significantly increase paclitaxel-induced cytotoxicity in drug-resistant cells, while presenting a low level of cytotoxicity.

METHODS

The in vitro cytotoxic and MDR-reversing activities of the Syl611 were determined by MTT assays. The cytotoxicity enhancement of paclitaxel was performed using the acridine orange/ethidium bromide double staining. Rhodamine 123 accumulation and retention assay in KB/V cells, Caco-2 monolayer model were used to find mechanism of action.

RESULTS

The cytotoxicity of Syl611 was wondrously lower in all tested cell lines than that of paclitaxel. Cytotoxicity enhancement from Syl611 was dramatically higher than that of verapamil of the same concentration (10 muM): the reversal fold index for A549/Paclitaxel, KB/V, and Bel7402/5-FU were 45.95, 73.56, and 107.13 (Syl611) and 11.36, 23.92, and 70.42 (verapamil). AO/EB double staining assay equally showed that Syl611 could enhance the cytotoxicity induced by paclitaxel. Furthermore, Syl611 could also increase the intracellular accumulation of Rhodamine 123 in KB/V cells without affecting P-gp's expression, and this accumulation was reversible. In bidirectional permeability assay, Syl611 increased the permeability of paclitaxel but decreased the net secretory of paclitaxel.

CONCLUSIONS

Syl611 is an effective and potential agent in reversing multidrug resistance (MDR) by multiple actions, which attributed to p-glycoprotein inhibition and drug permeability enhancement.

Involvement of Nrf2 activation in resistance to 5-fluorouracil in human colon cancer HT-29 cells

Acquisition of drug resistance by cancer cells is attributed to various factors including alterations in apoptotic pathways, enhanced expression of multidrug resistance-associated proteins, altered drug metabolism or uptake and/or overexpression of cytoprotective genes. Thus, potential induction of defence pathways by anticancer drugs might have a marked incidence on cancer cell resistance. 5-Fluorouracil (5-FU) remains the most commonly used anticancer drug for the treatment of colorectal cancer, although objective response rates are as low as 20%. The aim of our study was to investigate the effects of 5-FU on cytoprotective systems in human colon HT-29 cells. Our results demonstrate that 5-FU induced the expression of mRNAs encoding glutathione transferases and antioxidant enzymes. To further determine the mechanisms involved in 5-FU effects, we investigated whether it activates the Nrf2/antioxidant response element pathway which is implicated in the regulation of several genes involved in cytoprotection. Translocation of Nrf2 into the nucleus after 5-FU exposure was demonstrated by immunocytochemistry and western blotting. Using an ARE-driven reporter gene assay, activation of the luciferase activity by 5-FU was also evidenced. Moreover, transfection of HT-29 cells with siRNA directed against Nrf2 inhibited induction of Nrf2 target genes and increased 5-FU cytotoxicity. In conclusion, we demonstrate for the first time that 5-FU activates the Nrf2/ARE pathway which in turn induces cytoprotective genes and modulates chemosensitivity of HT-29 colon cancer cells. Therefore, we postulate that Nrf2 might represent a potential therapeutic target in 5-FU treatment of colon cancer.

Cytosine deaminase expressing human mesenchymal stem cells mediated tumour regression in melanoma bearing mice

BACKGROUND

Previously, we validated capability of human adipose tissue-derived mesenchymal stem cells (AT-MSC) to serve as cellular vehicles for gene-directed enzyme prodrug molecular chemotherapy. Yeast fusion cytosine deaminase : uracil phosphoribosyltransferase expressing AT-MSC (CD y-AT-MSC) combined with systemic 5-fluorocytosine (5FC) significantly inhibited growth of human colon cancer xenografts. We aimed to determine the cytotoxic efficiency to other tumour cells both in vitro and in vivo.

METHODS

CD y-AT-MSC/5FC-mediated proliferation inhibition against a panel of human tumour cells lines was evaluated in direct and indirect cocultures in vitro. Antitumour effect was tested on immunodeficient mouse model in vivo.

RESULTS

Although culture expansion of CD y-AT-MSC sensitized these cells to 5FC mediated suicide effect, expanded CD y-AT-MSC/5FC still exhibited strong bystander cytotoxic effect towards human melanoma, glioblastoma, colon, breast and bladder carcinoma in vitro. Most efficient inhibition (91%) was observed in melanoma A375 cell line when directly cocultured with 2% of therapeutic cells CD y-AT-MSC/5FC. The therapeutic paradigm of the CD y -AT-MSC/5FC system was further evaluated on melanoma A375 xenografts on nude mice in vivo. Complete regression in 89% of tumours was achieved when 20% CD y-AT-MSC/5FC were co-injected along with tumour cells. More importantly, systemic CD y-AT-MSC administration resulted in therapeutic cell homing into subcutaneous melanoma and mediated tumour growth inhibition.

CONCLUSIONS

CD y-AT-MSC capability of targeting subcutaneous melanoma offers a possibility to selectively produce cytotoxic agent in situ. Our data further demonstrate beneficial biological properties of AT-MSC as a cellular vehicle for enzyme/prodrug therapy approach to molecular chemotherapy.

Reversal effect of tyroservatide (YSV) tripeptide on multi-drug resistance in resistant human hepatocellular carcinoma cell line BEL-7402/5-FU

Tyroservatide (YSV) is an active, low-molecular-weight polypeptide that has been shown to have antitumor effects on human hepatocellular carcinoma BEL-7402 cells in vitro and in vivo. Multi-drug resistance (MDR) represents a major obstacle to the success of cancer chemotherapy. To enhance the chemosensitivity of tumor cells, attention has been focused on MDR modulators. In this study, we evaluated the reversal effect of YSV on MDR, and explored its mechanism of action in vitro. Administration of YSV reversed the multi-drug resistance of human hepatocellular carcinoma BEL-7402/5-FU cells significantly. The intracellular accumulation of doxorubicin and Rhodamine-123 (Rh123) were increased, which implied that the function of the P-glycoprotein (P-gp) efflux pump was inhibited by YSV. Moreover, the mRNA and protein expression of multi-drug resistance gene (MDR1) were also decreased by YSV. We observe that lung-resistance protein (LRP) and multi-drug resistance-associated protein (MRP1) each contribute to MDR in BEL-7402/5-FU cells as well. The mRNA and protein expression of LRP were decreased by YSV. No significant change was observed in mRNA expression of MRP1. However, we observe that the MRP1 protein level was reduced after treatment with YSV. These data demonstrate that YSV effectively reverses MDR in BEL-7402/5-FU cells, and that its mechanism of action is associated with the down-regulation of MDR1, MRP1 and LRP expression, as well as the inhibition of P-gp function.

Lx2-32c, a novel taxane and its antitumor activities in vitro and in vivo

Lx2-32c, a novel taxane derivative, is a semisynthetic analogue from cephalomannine. Its antitumor activity in vivo and in vitro was investigated in this study. Lx2-32c was cytotoxic (IC50=1.7+/-1.6nM) to various human tumor cell lines after 72h incubation. In vitro it enhanced the rate of tubulin polymerization in a dose-dependent manner and induced the bundling of microtubule in BGC-823 cells with the mode similar to that of paclitaxel. As determined by flow cytometry, after either 12 or 24h exposure, Lx2-32c caused BGC-823 cells G2/M phase arrest in a time- and dose-dependent manner. Moreover, we demonstrated that Lx2-32c had significant antitumor activity on BGC-823 (human gastric carcinoma) and A549 (human non-small cell lung carcinoma) xenograft in nude mice. These data suggest that Lx2-32c is a microtubule-stabilizing agent, which has significant antitumor activity in vitro and in vivo.

Role of intracellular glutathione in cell sensitivity to the apoptosis induced by tumor necrosis factor {alpha}-related apoptosis-inducing ligand/anticancer drug combinations

PURPOSE

We have recently shown that combination of tumor necrosis factor alpha-related apoptosis-inducing ligand (TRAIL) with anticancer drugs induced an apoptotic cell death pathway involving both caspases and mitochondria. The present work further explores the role of intracellular reduced glutathione (GSH) level in cell sensitivity to this cell death pathway.

EXPERIMENTAL DESIGN

Intracellular GSH level was measured by high-performance liquid chromatography. Cell death was detected by immunofluorescence after Hoechst 33342/propidium iodide staining. Reactive oxygen species production was evaluated by flow cytometry after dihydroethidium probe labeling. Western blot analysis was done to study stress-activated protein kinase/c-jun NH(2)-terminal kinase (SAPK/JNK) phosphorylation. The Student's t test was used to determine significance of the results. Three to six experiments were done.

RESULTS

GSH depletion enhanced apoptosis induced by TRAIL/cisplatin (CDDP) or TRAIL/5-fluorouracil (5-FU) combinations in both human HT29 colon carcinoma and HepG2 hepatocarcinoma cells, whereas it enhanced cytotoxicity induced only by TRAIL/CDDP in human primary hepatocytes. Our results further suggested that GSH depletion enhanced SAPK/JNK phosphorylation upon TRAIL/5-FU exposure and likely reduced the detoxification mechanisms of CDDP in HT29 cells. Resistance of Bcl-2-expressing HT29 and HepG2 cells to combined treatment was not overcome by GSH depletion, thus indicating that Bcl-2-mediated antiapoptotic effect occurs independently of intracellular GSH level.

CONCLUSION

GSH depletion could be useful to increase the therapeutic efficacy of cancer treatment by TRAIL/anticancer drug combinations. Furthermore, TRAIL/5-FU combination might be a potential anticancer treatment of human tumors, being ineffective on human primary hepatocytes and thus could be of interest in clinical cancer treatment. Nevertheless, Bcl-2 expression remains an important resistance factor.

Correlation of expression of multidrug resistance protein and messenger RNA with 99mTc-methoxyisobutyl isonitrile (MIBI) imaging in patients with hepatocellular carcinoma

AIM

To explore whether P-glycoprotein (Pgp) and other pumps, multidrug resistance-associated protein (MRP) and lung resistance protein (LRP), could affect tumor accumulation and efflux of 99mTc-MIBI in liver cancer.

METHODS

Surgically treated 78 liver cancer patients were included in this study. Before surgery, 99mTc-MIBI SPECT was performed 15 min and 120 min after injection of 20 mCi 99mTc-MIBI, respectively. Early uptake, delayed uptake (L/Nd), and washout rate (L/Nwr) of 99mTc-MIBI were obtained. Expressions of Pgp, MRP and LRP were investigated with Western blotting and immunohistochemistry. Messenger RNA (mRNA) level of Pgp, MRP and LRP was determined by RT-PCR.

RESULTS

No 99mTc-MIBI uptakes in tumor lesions of 68 of 78 (87.2%) patients with hepatocellular carcinoma were found on 99mTc-MIBI SPECT. P-gp expression was observed in tumor tissues of the patients with no uptake of 99mTc-MIBI (P<0.017). No appreciable correlation was found between liver cancer 99mTc-MIBI images and expression of MRP or LRP on the level of protein or mRNA.

CONCLUSION

99mTc-MIBI SPECT is noninvasive, and useful in predicting the presence of MDR1 gene-encoded Pgp in patients with hepatocellular carcinoma.

Toxicities and therapeutic effect of 5-fluorouracil controlled release implant on tumor-bearing rats

AIM: To investigate the toxicities, biodistribution and anticancer effect of 5-fluorouracil controlled release implant (5-FUCI) on Walker 256 carcinosarcoma cells in Wistar rats.

METHODS: Experiment 1: Wistar rats were randomly divided into three groups (27 rats per group). Blank implant was implanted in left lobe of the liver, and rats were treated with saline solution (in group A) or 5-fluorouracil (subcutaneous injection, group B). 5-FUCI was inserted in left lobe of the liver (group C). The gastrointestinal and hematological toxicities were observed and contents of element F in group C were assayed. Experiment 2: on day 6 after Walker-256 carcinosarcoma transplantation in left lobe of the liver, 5-FUCI was implanted in right lobe of the liver (group E) or left lobe (group F), and rats in control group (group D) were inserted blank implant. Tumor inhibition rate and survival time were investigated.

RESULTS: 5-FUCI showed no obvious toxic effect, extraction of Evan’s blue from gastrointestinal tissue was normal, the peripheral white blood cells and bone marrow nucleated cells were not reduced, compared with control group (P > 0.05). Histological examination revealed that there were no visible changes in small intestinal mucosa, The concentration of 5-fluorouracil in left lobe of the liver was 9.84, 28, 34 times as much as those of right lobe of the liver, heart and kidney respectively after the implantation in group C. They kept a high level of fluorouracil in left lobe of the liver, ranging from (4.414% ± 0.482%) to (7.800% ± 0.804%), for eight weeks. Survival days were 28.0 ± 2.2, 30.0 ± 3.2 and 38.7 ± 6.7 d in group D, E and F, respectively.

CONCLUSION: 5-FUCI shows no obvious toxicities to gastrointestinal tract and myelotoxicity. After implantation, it kept a high level of 5- fluorouracil in surrounding tissues of the implant for eight weeks. Its antitumor effect on Walker-256 carcinosarcoma is demonstrated.