Impact of the cAMP efflux and extracellular cAMP-adenosine pathway on airway smooth muscle relaxation induced by formoterol and phosphodiesterase inhibitors

β2-adrenoceptors agonists and phosphodiesterase (PDE) inhibitors are effective bronchodilators, due to their ability to increase intracellular cyclic AMP (cAMP) levels and induce airway smooth muscle (ASM) relaxation. We have shown that increment of intracellular cAMP induced by β2-adrenoceptors agonist fenoterol is followed by efflux of cAMP, which is converted by ecto-PDE and ecto-5'-nucleotidases (ecto-5'NT) to adenosine, leading to ASM contraction. Here we evaluate whether other classical bronchodilators used to treat asthma and chronic obstructive pulmonary disease (COPD) could induce cAMP efflux and, as consequence, influence the ASM contractility. Our results showed that β2-adrenoceptor agonists formoterol and PDE inhibitors IBMX, aminophylline and roflumilast induced cAMP efflux and a concentration-dependent relaxation of rat trachea precontracted with carbachol. Pretreatment of tracheas with MK-571 (MRP transporter inhibitor), AMP-CP (ecto-5'NT inhibitor) or CGS-15943 (nonselective adenosine receptor antagonist) potentiated the relaxation induced by β2-adrenoceptor agonists but did not change the relaxation induced by PDE inhibitors. These data showed that all bronchodilators tested were able to induce cAMP efflux. However, only β2-adrenoceptor-induced relaxation of tracheal smooth muscle was affected by cAMP efflux and extracellular cAMP-adenosine pathway.

ABC Transporter-Mediated Multidrug-Resistant Cancer

ATP-binding cassette (ABC) transporters are involved in active pumping of many diverse substrates through the cellular membrane. The transport mediated by these proteins modulates the pharmacokinetics of many drugs and xenobiotics. These transporters are involved in the pathogenesis of several human diseases. The overexpression of certain transporters by cancer cells has been identified as a key factor in the development of resistance to chemotherapeutic agents. In this chapter, the localization of ABC transporters in the human body, their physiological roles, and their roles in the development of multidrug resistance (MDR) are reviewed. Specifically, P-glycoprotein (P-GP), multidrug resistance-associated proteins (MRPs), and breast cancer resistance protein (BCRP/ABCG2) are described in more detail. The potential of ABC transporters as therapeutic targets to overcome MDR and strategies for this purpose are discussed as well as various explanations for the lack of efficacy of ABC drug transporter inhibitors to increase the efficiency of chemotherapy.

In vitro bile acid-dependent hepatocyte toxicity assay system using human induced pluripotent stem cell-derived hepatocytes: Current status and disadvantages to overcome

Cholestatic drug-induced liver injury (DILI) is a type of hepatotoxicity. Its underlying mechanisms are dysfunction of bile salt export pump (BSEP) and multidrug resistance-associated protein 2/3/4 (MRP2/3/4), which play major roles in bile acid (BA) excretion into the bile canaliculi and blood, resulting in accumulation of BAs in hepatocytes. The sandwich-cultured hepatocyte (SCH) model can simultaneously analyze hepatic uptake and biliary excretion. Therefore, we investigated whether sandwich-cultured human induced pluripotent stem cell (iPS cell)-derived hepatocytes (SCHiHs) are suitable for evaluating cholestatic DILI. Fluorescent N-(24-[7-(4-N,N-dimethylaminosulfonyl-2,1,3-benzoxadiazole)]amino-3α,7α,12α-trihydroxy-27-nor-5β-cholestan-26-oyl)-2'-aminoethanesulfonate (tauro-nor-THCA-24-DBD, a BSEP substrate) was accumulated in bile canaliculi, which supports the presence of a functional bile canaliculi lumen. MRP2 was highly expressed in the Western blot analysis, whereas the mRNA expression of BSEP was hardly detectable. MRP3/4 mRNA levels were maintained. Of the 22 compounds known to cause DILI with BAs, 7 showed significant cytotoxicity. Most high-risk drugs were detected using the developed SCHiH system. However, a shortcoming was the considerably low expression level of BSEP, which prevented the detection of some relevant drugs whose risks should be detected in primary human hepatocytes.

Alteration of MRP2 expression and the graft outcome after liver transplantation

Purpose

Multidrug resistance-associated protein (MRP) 2 is a glutathione conjugate in the canalicular membrane of hepatocytes. Early graft damage after liver transplantation (LT) can result in alteration of MRP2 expression. The purpose of this study was to evaluate the relationship between the pattern of MRP2 alteration and graft outcome.

Methods

Forty-one paraffin-embedded liver graft tissues obtained by protocol biopsy within 2 months after LT; these were stained using monoclonal antibodies of MRP2. We selected 15 live donor biopsy samples as a control, that showed homogenous canalicular staining for MRP2. The pattern of canalicular MRP2 staining of graft was classified into 3 types: homogenous (type C0), focal (type C1), and no (type C2,) staining of the canaliculi.

Results

In total, 17.1% graft tissues were type C0, 36.6% were type C1, and 46.3% were type C2. The median operation time was longer in patients with type C2 (562.6 minutes) than in patients with type C0 (393.8 minutes) (P = 0.038). The rates of posttransplant complications were higher in patients with type C2 (100%) than in patients with type C0 (42.9%) and C1 (73.3%) (P < 0.001).

Conclusion

MRP2 expression pattern was altered in 82.9% after LT. The pattern of MRP2 alteration was associated with longer operation time and higher rates of post-LT complications.

Delivery of siRNA in vitro and in vivo using PEI-capped porous silicon nanoparticles to silence MRP1 and inhibit proliferation in glioblastoma

BACKGROUND

Multidrug resistance-associated protein 1 (MRP1) overexpression plays a major role in chemoresistance in glioblastoma multiforme (GBM) contributing to its notorious deadly nature. Although MRP1-siRNA transfection to GBM in vitro has been shown to sensitise the cells to drug, MRP1 silencing in vivo and the phenotypic influence on the tumour and normal tissues upon MRP1 down-regulation have not been established. Here, porous silicon nanoparticles (pSiNPs) that enable high-capacity loading and delivery of siRNA are applied in vitro and in vivo.

RESULT

We established pSiNPs with polyethyleneimine (PEI) capping that enables high-capacity loading of siRNA (92 µg of siRNA/mg PEI-pSiNPs), and optimised release profile (70% released between 24 and 48 h). These pSiNPs are biocompatible, and demonstrate cellular uptake and effective knockdown of MRP1 expression in GBM by 30%. Also, siRNA delivery was found to significantly reduce GBM proliferation as an associated effect. This effect is likely mediated by the attenuation of MRP1 transmembrane transport, followed by cell cycle arrest. MRP1 silencing in GBM tumour using MRP1-siRNA loaded pSiNPs was demonstrated in mice (82% reduction at the protein level 48 h post-injection), and it also produced antiproliferative effect in GBM by reducing the population of proliferative cells. These results indicate that in vitro observations are translatable in vivo. No histopathological signs of acute damage were observed in other MRP1-expressing organs despite collateral downregulations.

CONCLUSIONS

This study proposes the potential of efficient MRP1-siRNA delivery by using PEI-capped pSiNPs in achieving a dual therapeutic role of directly attenuating the growth of GBM while sensitising residual tumour cells to the effects of chemotherapy post-resection.

ATP-dependent activity and mitochondrial localization of drug efflux pumps in doxorubicin-resistant breast cancer cells

BACKGROUND

We hypothesized that, among the mechanisms of drug-resistance acquired by doxorubicin (DOX)-resistant breast cancer cells to maintain cell survival, ATP-dependent drug efflux pumps could be expressed in their mitochondrial membranes and this might limit the accumulation of DOX in this subcellular compartment in relation to mitochondrial ATP production.

METHODS/RESULTS

Mitochondrial DOX accumulation: the presence and the activity of mitochondrial efflux pumps and their relationship with mitochondrial ATP synthesis were analyzed in DOX-resistant (MCF-7dox^R) and -sensitive (MCF-7^S) breast cancer cells. Mitochondrial accumulation of DOX (autofluorescence) was decreased when ATP was produced, but only in MCF-7dox^R. In these DOX-resistant cells, breast cancer resistance protein (BCRP) and multidrug resistance-associated protein (MRP1) were expressed and localized in mitochondria (confocal microscopy and confocal spectral imaging studies). In addition, mitochondrial accumulation of DOX was increased by BCRP and MRP1 inhibitors and, to a lower extent, by the mitochondrial ATP synthase inhibitor, oligomycin, in MCF-7dox^R.

CONCLUSIONS

Both BCRP and MRP1 were localized in mitochondria and participated to the reduction of mitochondrial accumulation of DOX in MCF-7dox^R. This process was partly dependent of mitochondrial ATP synthesis.

GENERAL SIGNIFICANCE

The present study provides novel insights in the involvement of mitochondria in the underlying mechanisms of DOX-resistance in breast cancer cells.

Inhibition of ABC transport proteins by oil sands process affected water

The ATP-binding cassette (ABC) superfamily of transporter proteins is important for detoxification of xenobiotics. For example, ABC transporters from the multidrug-resistance protein (MRP) subfamily are important for excretion of polycyclic aromatic hydrocarbons (PAHs) and their metabolites. Effects of chemicals in the water soluble organic fraction of relatively fresh oil sands process affected water (OSPW) from Base Mine Lake (BML-OSPW) and aged OSPW from Pond 9 (P9-OSPW) on the activity of MRP transporters were investigated in vivo by use of Japanese medaka at the fry stage of development. Activities of MRPs were monitored by use of the lipophilic dye calcein, which is transported from cells by ABC proteins, including MRPs. To begin to identify chemicals that might inhibit activity of MRPs, BML-OSPW and P9-OSPW were fractionated into acidic, basic, and neutral fractions by use of mixed-mode sorbents. Chemical compositions of fractions were determined by use of ultrahigh resolution orbitrap mass spectrometry in ESI(+) and ESI(-) mode. Greater amounts of calcein were retained in fry exposed to BML-OSPW at concentration equivalents greater than 1× (i.e., full strength). The neutral and basic fractions of BML-OSPW, but not the acidic fraction, caused greater retention of calcein. Exposure to P9-OSPW did not affect the amount of calcein in fry. Neutral and basic fractions of BML-OSPW contained relatively greater amounts of several oxygen-, sulfur, and nitrogen-containing chemical species that might inhibit MRPs, such as O(+), SO(+), and NO(+) chemical species, although secondary fractionation will be required to conclusively identify the most potent inhibitors. Naphthenic acids (O2(-)), which were dominant in the acidic fraction, did not appear to be the cause of the inhibition. This is the first study to demonstrate that chemicals in the water soluble organic fraction of OSPW inhibit activity of this important class of proteins. However, aging of OSPW attenuates this effect and inhibition of the activity of MRPs by OSPW from Base Mine Lake does not occur at environmentally relevantconcentrations.

Thieno[2,3-b]pyridines--a new class of multidrug resistance (MDR) modulators

To identify new potent multidrug resistance modulators, we have synthesized a series of novel thieno[2,3-b]pyridines and furo[2,3-b]pyridines, and examined their structure-activity relationships. All synthesized compounds were tested to determine BCRP1, P-gp, and MRP1 inhibitor activity, and most potent MDR modulators were also screened for their toxicity, cytotoxicity and Ca(2+) channel antagonist activity. Among these compounds, thieno[2,3-b]pyridine (6r) was found to exhibit a potent P-gp inhibitory action with EC50 = 0.3 ± 0.2 μM, MRP1 inhibitory action with EC50 = 1.1 ± 0.1 μM and BCRP1 inhibitory action with EC50 = 0.2 ± 0.05 μM and may represent suitable candidate for further pharmacological studies.

Delivery of antihuman African trypanosomiasis drugs across the blood-brain and blood-CSF barriers

Human African trypanosomiasis (HAT or sleeping sickness) is a potentially fatal disease caused by the parasite, Trypanosoma brucei sp. The parasites are transmitted by the bite of insect vectors belonging to the genus Glossina (tsetse flies) and display a life cycle strategy that is equally spread between human and insect hosts. T.b. gambiense is found in western and central Africa whereas, T.b. rhodesiense is found in eastern and southern Africa. The disease has two clinical stages: a blood stage after the bite of an infected tsetse fly, followed by a central nervous system (CNS) stage where the parasite penetrates the brain; causing death if left untreated. The blood-brain barrier (BBB) makes the CNS stage difficult to treat because it prevents 98% of all known compounds from entering the brain, including some anti-HAT drugs. Those that do enter the brain are toxic compounds in their own right and have serious side effects. There are only a few drugs available to treat HAT and those that do are stage specific. This review summarizes the incidence, diagnosis, and treatment of HAT and provides a close examination of the BBB transport of anti-HAT drugs and an overview of the latest drugs in development.

In vivo disposition and metabolism of madecassoside, a major bioactive constituent in Centella asiatica (L.) Urb

ETHNOPHARMACOLOGICAL RELEVANCE

Centella asiatica (L.) Urb. herb is frequently used in traditional Chinese medicine for many indications, such as traumatic injuries, keloid and scar. Madecassoside is the main active ingredient of this herb drug with higher content than other triterpenoid constituents. Understandings of pharmacokinetic profiles of madecassoside should be beneficial for its development as a therapeutic agent.

MATERIALS AND METHODS

Sprague-Dawley rats were intravenously and orally administered madecassoside (100 mg/kg), respectively. Plasma, heart, liver, spleen, lung, kidney, brain, bile, urine and feces were collected at the designed time points. Madecassoside concentrations in biological samples were determined by a sensitive and well-validated liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) method. A liquid chromatography coupled with time-of-flight mass spectrometry (LC-TOF-MS) method was established to identify its major metabolites in feces. To further pursue the disposition characteristics of madecassoside in rats, the involvement of the hepatobiliary efflux transporters in biliary elimination were studied by combination with digoxin (P-glycoprotein inhibitor) or probenecid (multidrug resistance-associated protein inhibitor). A linked-rat model was also used to assess the role of enterohepatic circulation in the pharmacokinetics of madecassoside.

RESULTS

After a single oral dosing, madecassoside was widely distributed in heart, liver, spleen, lung and kidney of rats, and the levels of madecassoside in liver and kidney were relatively higher than other organs. The excretions of madecassoside in bile, urine and feces were 7.16% (0-12 h), 0.25% (0-72 h) and 24.68% (0-72 h), respectively. The findings suggested that madecassoside might excrete mainly by metabolites. The combination with either digoxin or probenecid significantly attenuated the excretion of madecassoside as parent from bile, indicating that P-glycoprotein and multidrug resistance-associated protein might contribute to the hepatobiliary elimination of madecassoside. The presence of enterohepatic circulation, as implied by double-humped profiles in plasma and tissue concentration-time curves, was confirmed by a linked-rat model. Furthermore, three metabolities of madecassoside were indentified in rat feces and the possible metabolic pathways were proposed.

CONCLUSIONS

These findings provide valuable information regarding in vivo process of madecassoside, and help us to recognize the efficacy and safety of madecassoside itself, the relevant herbs or herbal preparations.

Reversal of multidrug resistance by the inhibition of ATP-binding cassette pumps employing "Generally Recognized As Safe" (GRAS) nanopharmaceuticals: A review

Pumps of the ATP-binding cassette superfamily (ABCs) regulate the access of drugs to the intracellular space. In this context, the overexpression of ABCs is a well-known mechanism of multidrug resistance (MDR) in cancer and infectious diseases (e.g., viral hepatitis and the human immunodeficiency virus) and is associated with therapeutic failure. Since their discovery, ABCs have emerged as attractive therapeutic targets and the search of compounds that inhibit their genetic expression and/or their functional activity has gained growing interest. Different generations of pharmacological ABC inhibitors have been explored over the last four decades to address resistance in cancer, though clinical results have been somehow disappointing. "Generally Recognized As Safe" (GRAS) is a U.S. Food and Drug Administration designation for substances that are accepted as safe for addition in food. Far from being "inert", some amphiphilic excipients used in the production of pharmaceutical products have been shown to inhibit the activity of ABCs in MDR tumors, emerging as a clinically translatable approach to overcome resistance. The present article initially overviews the classification, structure and function of the different ABCs, with emphasis on those pumps related to drug resistance. Then, the different attempts to capitalize on the activity of GRAS nanopharmaceuticals as ABC inhibitors are discussed.

MDR-selective microbial-based therapy: a novel approach to cancer treatment. Med Hypotheses. 2013;81:207-211. [PMID: 23719029 DOI: 10.1016/j.mehy.2013.05.001]

Microbial-based therapy of cancer is one of the earliest non-surgical anticancer therapies. The main limitation of such therapies is the toxicity of the therapeutic dose. This article discusses a novel approach that exploits cancer multidrug resistance (MDR) to provide a safer microbial-based therapy. As multidrug resistant cells can only contain limited amounts of a variety of susceptible drugs including certain antibiotics, we can take advantage of MDR to create a micro-environment (antibiotic free) that favors growth of intracellular bacteria within cancer cells. Thus, this approach targets cancer cells and spares normal cells (shielded by antibiotic): providing a more selective thus safer anticancer treatment. This article also explores the potentials of Chlamydia pneumoniae as an anti-cancer agent in this MDR-selective microbial-based therapy: its unique life cycle and the immune response to its infection suggest that it could be used directly, in the proposed approach, without any pre-requirements.

Correlation between PgP, TP, GST-π and MRP expression and response to chemotherapy in patients with esophageal cancer

AIM: To study the relationship between expression of P-glycoprotein (PgP), thymidine phosphorylase (TP), glutathione S-transferase-π (GST-π), and multidrug resistance-associated protein (MRP) and response to chemotherapy in patients with esophageal cancer.

METHODS: Fifty-eight patients gastroscopically and pathologically diagnosed with esophageal cancer were included in this study. Esophageal cancer samples collected from these patients were used to detect the expression of PgP, TP, GST-π, and MRP by immunohistochemistry. All the patients underwent neoadjuvant chemotherapy with double-platinum regimen. Response to chemotherapy and expression of PgP, TP, GST-π, and MRP was analyzed.

RESULTS: PgP-positive particles were distributed in the membrane and cytoplasm, TP-positive particles in the cytoplasm and nucleus, GST-π-positive particles in the cytoplasm, and MRP-positive particles in the cytoplasm. The positive rates of PgP, TP, GST-π, and MRP expression in esophageal cancer were 41.37%, 32.76%, 20.69% and 37.93%, respectively. Compared to patients not responding to chemotherapy, the positive rates of PgP, GSH and MRP expression were significantly lower and that of TP was significantly higher in patients having response to chemotherapy.

CONCLUSION: Low expression of PgP, GST-π, and MRP and high expression of TP are conducive to chemotherapy in patients with esophageal cancer.

LY294002 combined with gemcitabine inhibits p-Akt and MRP expression in human pancreatic carcinoma PANC-1 cells

AIM: To investigate the effect of LY294002 (a PI3K inhibitor) combined with gemcitabine on p-Akt and multidrug resistance-associated protein (MRP) expression in human pancreatic carcinoma PANC-1 cells.

METHODS: After PANC-1 cells were treated with different concentrations of LY294002 and gemcitabine, the expression of MRP mRNA and p-Akt and MRP proteins was detected by semi-quantitative RT-PCR and Western blot, respectively.

RESULTS: Compared to untreated control cells, treatment with LY294002 combined with gemcitabine significantly decreased the expression of MRP mRNA (1.47 ± 0.03, 1.31 ± 0.05, 1.02 ± 0.04, 0.76 ± 0.06, 0.37 ± 0.02, P < 0.05) and p-Akt and MRP proteins (p-Akt: 0.80±0.02, 0.63±0.01, 0.52±0.01, 0.41 ± 0.02, 0.35 ± 0.02, P < 0.05; MRP: 0.93 ± 0.05, 0.87 ± 0.03, 0.81 ± 0.03, 0.71 ± 0.02, 0.40 ± 0.03, both P < 0.05) in a concentration-dependent manner.

CONCLUSION: LY294002 could effectively strengthen the sensitivity of human pancreatic carcinoma PANC-1 cells to gemcitabine. LY294002 may down-regulate MRP transcription by inhibiting p-Akt expression and therefore reverse resistance of PANC-1 cells to gemcitabine.

Down-regulation of extracellular signal-regulated kinase 1/2 activity in P-glycoprotein-mediated multidrug resistant hepatocellular carcinoma cells

AIM: To study the expression and phosphorylation of extracellular signal-regulated kinase (ERK) 1 and ERK2 in multidrug resistant (MDR) hepatocellular carcinoma (HCC) cells.

METHODS: MDR HCC cell lines, HepG2/adriamycin (ADM) and SMMC7721/ADM, were developed by exposing parental cells to stepwise increasing concentrations of ADM. MTT assay was used to determine drug sensitivity. Flow cytometry was employed to analyze cell cycle distribution and measure cell P-glycoprotein (P-gp) and multidrug resistant protein 1 (MRP1) expression levels. ERK1 and ERK2 mRNA expression levels were measured by quantitative real-time PCR (QRT-PCR). Expression and phosphorylation of ERK1 and ERK2 were analyzed by Western blot.

RESULTS: MTT assay showed that HepG2/ADM and SMMC7721/ADM were resistant not only to ADM, but also to multiple anticancer drugs. The P-gp expression was over 10-fold higher in HepG2/ADM cells than in HepG2 cells (8.92% ± 0.22% vs 0.88% ± 0.05%, P < 0.001) and over 4-fold higher in SMMC7721/ADM cells than in SMMC7721 cells (7.37% ± 0.26% vs 1.74% ± 0.25%, P < 0.001). However, the MRP1 expression was not significantly higher in HepG2/ADM and SMMC7721/ADM cells than in parental cells. In addition, the percentage of MDR HepG2/ADM and SMMC7721/ADM cells was significantly decreased in the G0/G1 phase and increased in the the S phase or G2/M phase. QRT-PCR analysis demonstrated that the ERK1 and ERK2 mRNA expression increased apparently in HepG2/ADM cells and decreased significantly in SMMC7721/ADM cells. Compared with the expression of parental cells, ERK1 and ERK2 protein expressions were markedly decreased in SMMC7721/ADM cells. However, ERK2 protein expression was markedly increased while ERK1 protein expression had no significant change in HepG2/ADM cells. Phosphorylation of ERK1 and ERK2 was markedly decreased in both HepG2/ADM and SMMC7721/ADM MDR cells.

CONCLUSION: ERK1 and ERK2 activities are down-regulated in P-gp-mediated MDR HCC cells. ERK1 or ERK2 might be a potential drug target for circumventing MDR HCC cells.

Expression and significance of multidrug resistance-associated protein-1 in gastric carcinoma

AIM: To explore the expression of multidrug resistance-associated protein 1 (MRP-1) in gastric carcinoma and its significance.

METHODS: The expression of MRP-1 were detected by immunohistochemistry (SP method) in 30 cases of chronic superficial gastritis (CSG), 30 cases of gastric intestinal metaplasia (IM), 45 cases of dysplasia (Dys) and 65 cases of gastric carcinoma (GC). Reverse transcription-polymerase chain reaction (RT-PCR) was used to examine the expression of MRP-1 mRNA. The comparison between mean values and rates was performed by t test and χ² test, respectively, and the relativity between two factors was evaluated by linear relative analysis.

RESULTS: The expression of MRP-1 showed a gradually increasing tendency as the disease progressed from CSG, IM, Dys to GC, and there was significant difference between GC and Dys as well as IM (43/65 vs 19/45, 6/30, P < 0.05). The protein and mRNA expression of MRP-1 in gastric carcinoma were significantly higher than those in the corresponding cancer adjacent tissues (66.2% vs 33.3%, P < 0.01; 63.1% vs 28.9%, P < 0.01). Positive correlation was found between MRP-1 protein and mRNA expression (r = 0.598, P < 0.05).

CONCLUSION: MRP-1 expression shows a gradually increasing tendency in gastric carcinogensis both at mRNA and protein level.

Immunohistochemical expression of carcinoembryonic antigen, P53, nm23, Ki-67, multidrug resistance-associated protein and their correlations with the clinicopathology in colorectal carcinoma

AIM: To investigate the mechanism of cyclooxygenase-2 (COX-2), basic fibroblast growth factor (bFGF) in the carcinogenesis of colorectal carcinoma and adenoma.

METHODS: The expression of CEA, P53, nm23, Ki-67 and MRP protein were detected by SP immunohistochemistry in colorectal carcinoma (n = 73) admitted from January 2003 to July 2006, and their clinical data and follow-up documents were analyzed retrospectively.

RESULTS: The positive rates of CEA, P53, nm23, Ki-67 and MRP protein expression in colorectal cancer were 82.2%, 68.5%, 75.3%, 84.9% and 64.4%, respectively. CEA and MRP expression had no correlations with the patients'ages, sex, tumor size or location and differentiation types of tumor, depth of invasion and lymph node metastasis, while P53, Ki-67 and nm23 expression were significantly correlated with the depth of invasion and lymph node metastasis. The positive rates of P53 and Ki-67 expression was significantly higher in Dukes C, D stages than those in Dukes A, B stages (82.8% vs 59.1%, P < 0.05; 100% vs 75.0%, P < 0.05), while the positive rate of nm23 expression was markedly lower (58.6% vs 86.4%, P < 0.05). The expression of CEA had a negative correlations with that of nm23 (r = -0.296, P = 0.011) in colorectal carcinoma. However, the expression of P53 had a positive correlations with that of Ki-67 (r = 0.308, P = 0.008). P53, Ki-67 and nm23 expression were significantly related to the prognosis. The positive rate of nm23 expression was notably higher in patients survived over or equal to 3 years than that in ones survived less than 3 years (92.9% vs 71.2%, P < 0.05), but the positive rates of P53 and Ki-67 expression were just in the opposite situation (42.9% vs 74.6%, P < 0.05; 64.3% vs 89.8%, P < 0.05).

CONCLUSION: P53, Ki-67 and nm23 were significantly correlated with the invasion, metastasis and prognosis of colorectal carcinoma. CEA may be a stimulative factor in the invasion and metastasis of colorectal cancer and MRP-induced drug resistance may be relatively independent. CEA, P53, nm23 and Ki-67 can serve as effective markers ini reflecting the invasion, metastasis and prognosis of colorectal carcinoma.

Construction of microsphere encapusulating recombinant adenovirus with antisense multidrug resistance-associated protein gene and its effect on hepatocellular carcinoma

AIM: To construct the microsphere, in which recombinant adenovirus (rAdV) was encapusulated, carrying antisense multidrug resistance-associated protein (MRP) gene (as-mrp) and to investigate its effect on reversing MRP-mediated mutidrug resistance of hepatocellular carcinoma.

METHODS: The microsphere was constructed with biodegradable poly-DL-lactide-poly (ethylene-glycol) encapsulating as-mrp rAdV, and its diameter, the encapsulating rate, the virus loads and the releasing kinetics were determined in vitro. Human hepatocellular carcinoma HepG₂/ADM cells were transfected with the microspheres, and the fluorescence intensity was assayed after 48 hours and 120 hours. IC₅₀ of adriamycin on drug-resistant cells was determined. The level of MRP mRNA expression was detected by reverse transcription polymerase chain reaction (RT-PCR), and the ratio of MRP mRNA to β-actin mRNA (MRP/β-actin) was calculated. Intracelluar rubidomycin (DNR) concentration was examined by flow cytometry. Wistar rats were implanted with Walker-256 tumor solid piece to establish a liver cancer model. After injected with rAdV, the tumor size, growth rate and the average survival time were determined.

RESULTS: The microsphere, in which as-mrp rAdV was encapusulated, was constructed successfully. Its diameter, the encapsulating rate and the virus loads were 1.765 μm, 52.4% and 5.5×10¹¹efu/g, respectively. Almost 50% of the viruses were released within 120 h, and the total releasing time lasted more than 240 h. The released viruses remained active. More than 90% HepG₂/ADM cells could be transfected with 10 mg microspheres. IC₅₀ of adriamycin on HepG₂/ADM cells 48 and 120 h after transfection were 9.72 and 4.15 μg, respectively. Intracellular DNR intensity of the cells 120 h after transfection was significantly higher than that 48 h after transfection and the non-transfected cells (168.6±6.97 vs 98.39±6.17, t = 13.68, P < 0.01; 168.6±6.97 vs 112.52±9.21, t = 9.69, P < 0.01). The values of MRP/β-actin 120 and 48 h after transfection were decreased by 16.7% and 63.6% respectively as compared with that before transfection, and the value after 120 h was decreased by 26.25% as compared with that after 48 h. Compared with control group, normal saline group, rAdv group and microsphere without rAdv group, the tumor growth rate was decreased significantly in rAdv microsphere group (0.96±0.25 vs 8.79±0.34, 4.82±0.30, 4.67±0.67, 2.97±0.29; P < 0.05). The mean life time was prolonged significantly (43.6±7.4 vs 23.4±3.2, 25.3±3.7, 26.5±4.1, 33.7±2.9; P < 0.05).

CONCLUSION: The microsphere, in which rAdV carrying antisense MRP was encapusulated, can effectively inhibit MRP expression and improve the sensitivity of drug-resistant cells. This provides an experimental basis for the combination of macromolecular chemistry and gene therapy in the treatment of hepatocellular carcinoma.