Functional study of intracellular P-gp- and MRP1-mediated pumping of free cytosolic pirarubicin into acidic organelles in intrinsic resistant SiHa cells

Chemotherapeutic Efficacy Enhancement in P-gp-Overexpressing Cancer Cells by Flavonoid-Loaded Polymeric Micelles

Multidrug resistance is the major problem in cancer treatment nowadays. Compounds from plants are the new targets to solve this problem. Quercetin (QCT), quercetrin (QTR), and rutin (RUT) are potential anticancer flavonoids but their poor water solubility leads to less efficacy. In this study, the polymeric micelles of benzoylated methoxy-poly (ethylene glycol)-b-oligo(ε-caprolactone) or mPEG-b-OCL-Bz loading with the flavonoids were prepared to solve these problems. The flavonoid-loaded micelles showed an average size of 13-20 nm and maximum loading capacity of 35% (w/w). The release of QCT (21%, 3 h) was lower than that of QTR (51%, 3 h) and RUT (58%, 3 h). QCT (free and micelle forms) exhibited significantly higher cytotoxicity against P-glycoprotein-overexpressing leukemia (K562/ADR) cells than QTR and RUT (p < 0.05). The results demonstrated that QCT-loaded micelles effectively reversed cytotoxicity of both doxorubicin (multidrug resistant reversing (δ) values up to 0.71) and daunorubicin (δ values up to 0.74) on K562/ADR cells. It was found that QCT-loaded micelles as well as empty polymeric micelles inhibited P-gp efflux of tetrahydropyranyl Adriamycin. Besides, mitochondrial membrane potential was decreased by QCT (in its free form and micellar formation). Our results suggested that the combination effects of polymeric micelles (inhibiting P-gp efflux) and QCT (interfering mitochondrial membrane potential) might be critical factors contributing to the reversing multidrug resistance of K562/ADR cells by QCT-loaded micelles. We concluded that QCT-loaded mPEG-b-OCL-Bz micelles are the attractive systems for overcoming multidrug-resistant cancer cells.

Oleanolic acid derivative methyl 3,11-dioxoolean-12-en-28-olate targets multidrug resistance related to ABCB1

Multidrug resistance (MDR) in leukemia patients is a great incentive to the development of new drugs. In a search for potential multidrug resistance modulators we tested a group of oleanolic acid (OA) analogues modified at C-3, C-11, C-12 and C-28 using an experimental model consisting of three human acute lymphoblastic leukemia cell lines (CCRF-CEM and the multidrug resistant sublines CCRF-VCR1000 and CCRF-ADR5000). The most effective compound, methyl 3,11-dioxoolean-12-en-28-olate (DIOXOL) was more potent in cell viability inhibition than its precursor - OA, and showed similar or even higher activity in the drug resistant than in the wild-type cells. Resistance factor (RF) values obtained for CCRF-VCR1000 and CCRF-ADR-5000 cells using MTT assay were 0.7 and 0.8 (24 h of treatment) and after 72 h of treatment 0.9 and 1.1, respectively. Moreover, 5 μM DIOXOL significantly reduced the expression of the ABCB1 gene in MDR cells by around 30%, and also decreased the level of P-gp protein. Compared to untreated control cells, DIOXOL treatment resulted in a significant P-gp decrease (30% in CCRF-ADR5000 and 50% in CCRF-VCR1000), that was detected by western blot and confirmed by flow cytometry analysis. Moreover, DIOXOL (at 10 μM) significantly inhibited P-gp transport function by more than twofold comparing to control, untreated cells that was demonstrated using rhodamine 123-based functional test. The compound exhibited synergistic activity with ABCB1 substrate - adriamycin in CCRF-VCR1000 cells, indicating partial but significant MDR reversing ability.

Transactivation activity of human papillomavirus type 16 E6*I on aldo-keto reductase genes enhances chemoresistance in cervical cancer cells

The oncogenic E6 proteins produced by high-risk human papillomaviruses (HPVs) are invariably expressed in cervical carcinomas and are multifunctional proteins capable of affecting host-cell proliferation by binding and deregulating key host molecules such as p53. High-risk HPVs, including HPV16, have the unique ability to splice the E6 viral transcript, resulting in the production of a truncated E6 protein known as E6*I whose precise biological function is unclear. This study explored the changes in gene expression of the cervical cancer C33A cell line stably expressing HPV16 E6*I (16E6*I) and observed the upregulation of ten genes. Two of these genes were aldo-keto reductases (AKR1Cs), AKR1C1 and AKR1C3, which have been implicated in drug resistance. The results demonstrated that expression of 16E6*I, but not full-length E6, specifically increased AKR1C1 transcript levels although it did not alter AKR1C2 transcript levels. HPV16 E7 alone also had the ability to cause a moderate increase in AKR1C3 at both mRNA and protein levels. Site-directed mutagenesis of 16E6*I revealed that transactivation activity was abolished in R8A, R10A and T17A 16E6*I mutants without altering their intracellular localization patterns. Loss of transactivation activity of the 16E6*I mutants resulted in a significant loss of AKR1C expression and a decrease in drug resistance. Analysis of the AKR1C1 promoter revealed that, unlike the E6 protein, 16E6*I does not mediate transactivation activity solely through Sp1-binding sites. Taken together, it was concluded that 16E6*I has a novel function in upregulating expression of AKR1C and, in concert with E7, has implications for drug treatment in HPV-mediated cervical cancer.

Cytotoxic activity of Thai medicinal plants against human cholangiocarcinoma, laryngeal and hepatocarcinoma cells in vitro

Background

Cholangiocarcinoma is a serious public health in Thailand with increasing incidence and mortality rates. The present study aimed to investigate cytotoxic activities of crude ethanol extracts of a total of 28 plants and 5 recipes used in Thai folklore medicine against human cholangiocarcinoma (CL-6), human laryngeal (Hep-2), and human hepatocarcinoma (HepG2) cell lines in vitro.

Methods

Cytotoxic activity of the plant extracts against the cancerous cell lines compared with normal cell line (renal epithelial cell: HRE) were assessed using MTT assay. 5-fluorouracil was used as a positive control. The IC₅₀ (concentration that inhibits cell growth by 50%) and the selectivity index (SI) were calculated.

Results

The extracts from seven plant species (Atractylodes lancea, Kaempferia galangal, Zingiber officinal, Piper chaba, Mesua ferrea, Ligusticum sinense, Mimusops elengi) and one folklore recipe (Pra-Sa-Prao-Yhai) exhibited promising activity against the cholangiocarcinoma CL-6 cell line with survival of less than 50% at the concentration of 50 μg/ml. Among these, the extracts from the five plants and one recipe (Atractylodes lancea, Kaempferia galangal, Zingiber officinal, Piper chaba, Mesua ferrea, and Pra-Sa-Prao-Yhai recipe) showed potent cytotoxic activity with mean IC₅₀ values of 24.09, 37.36, 34.26, 40.74, 48.23 and 44.12 μg/ml, respectively. All possessed high activity against Hep-2 cell with mean IC₅₀ ranging from 18.93 to 32.40 μg/ml. In contrast, activity against the hepatoma cell HepG2 varied markedly; mean IC₅₀ ranged from 9.67 to 115.47 μg/ml. The only promising extract was from Zingiber officinal (IC₅₀ = 9.67 μg/ml). The sensitivity of all the four cells to 5-FU also varied according to cell types, particularly with CL-6 cell (IC₅₀ = 757 micromolar). The extract from Atractylodes lancea appears to be both the most potent and most selective against cholangiocarcinoma (IC₅₀ = 24.09 μg/ml, SI = 8.6).

Conclusions

The ethanolic extracts from five plants and one folklore recipe showed potent cytotoxic activity against CL-6 cell. Sensitivity to other cancerous cell lines varied according to cell types and the hepatocarcinoma cell line. HepG2 appears to be the most resistant to the tested extracts.

pH-responsive nanoparticles for cancer drug delivery

Solid tumors have an acidic extracellular environment and an altered pH gradient across their cell compartments. Nanoparticles responsive to the pH gradients are promising for cancer drug delivery. Such pH-responsive nanoparticles consist of a corona and a core, one or both of which respond to the external pH to change their soluble/insoluble or charge states. Nanoparticles whose coronas become positively charged or become soluble to make their targeting groups available for binding at the tumor extracellular pH have been developed for promoting cellular targeting and internalization. Nanoparticles whose cores become soluble or change their structures to release the carried drugs at the tumor extracellular pH or lysosomal pH have been developed for fast drug release into the extracellular fluid or cytosol. Such pH-responsive nanoparticles have therapeutic advantages over the conventional pH-insensitive counterparts.

Drug sensitivity and drug resistance profiles of human intrahepatic cholangiocarcinoma cell lines

AIM: To study the effect of a number of chemotherapeutic drugs on five human intrahepatic cholangiocarcinoma (CCA) cell lines. The expressions of genes that have been proposed to influence the resistance of chemotherapeutic drugs including thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), glutathione-S-transferase P1 (GSTP1), multidrug resistance protein (MDR1) and multidrug resistance-associated proteins (MRPs) were also determined.

METHODS: Five human CCA cell lines (KKU-100, KKU-M055, KKU-M156, KKU-M214 and KKU-OCA17) were treated with various chemotherapeutic drugs and growth inhibition was determined by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay. Semi-quantitative levels of gene expression were determined by a reverse transcriptase polymerase chain reaction (RT-PCR). Results of IC₅₀ values and the ratios of gene expression were analyzed by linear regression to predict their relationship.

RESULTS: Among five CCA cell lines, KKU-M055 was the most sensitive cell line towards all chemotherapeutic drugs investigated, particularly taxane derivatives with IC₅₀ values of 0.02-3 nmol/L, whereas KKU-100 was apparently the least sensitive cell line. When compared to other chemotherapeutic agents, doxorubicin and pirarubicin showed the lowest IC₅₀ values (<5 μmol/L) in all five CCA cell lines. Results from RT-PCR showed that TS, MRP1, MRP3 and GSTP1 were highly expressed in these five CCA cell lines while DPD and MRP2 were only moderately expressed. It should be noted that MDR1 expression was detected only in KKU-OCA17 cell lines. A strong correlation was only found between the level of MRP3 expression and the IC₅₀ values of etoposide, doxorubicin and pirarubicin (r = 0.86-0.98, P<0.05).

CONCLUSION: Sensitivity to chemotherapeutic agents is not associated with the histological type of CCA. Choosing of the appropriate chemotherapeutic regimen for the treatment of CCA requires knowledge of drug sensitivity. MRP3 was correlated with resistance of CCA cell lines to etoposide, doxorubicin and pirarubicin, whereas other chemotherapeutic drugs showed no association. The role of this multidrug resistance-associated protein, MRP3, in chemotherapeutic resistance in CCA patients needs to be further investigated.