Multidrug resistance protein 2 genetic polymorphism and colorectal cancer recurrence in patients receiving adjuvant FOLFOX-4 chemotherapy

Blood-brain barrier transporters: An overview of function, dysfunction in Alzheimer's disease and strategies for treatment

The blood-brain-barrier (BBB) has a major function in maintaining brain homeostasis by regulating the entry of molecules from the blood to the brain. Key players in BBB function are BBB transporters which are highly expressed in brain endothelial cells (BECs) and critical in mediating the exchange of nutrients and waste products. BBB transporters can also influence drug delivery into the brain by inhibiting or facilitating the entry of brain targeting therapeutics for the treatment of brain disorders, such as Alzheimer's disease (AD). Recent studies have shown that AD is associated with a disrupted BBB and transporter dysfunction, although their roles in the development in AD are not fully understand. Modulation of BBB transporter activity may pose a novel approach to enhance the delivery of drugs to the brain for enhanced treatment of AD. In this review, we will give an overview of key functions of BBB transporters and known changes in AD. In addition, we will discuss current strategies for transporter modulation for enhanced drug delivery into the brain.

Taurine up-regulated 1 accelerates tumorigenesis of colon cancer by regulating miR-26a-5p/MMP14/p38 MAPK/Hsp27 axis in vitro and in vivo

AIMS

The purpose of this study was to investigate the role of long non-coding RNA taurine-upregulated gene 1 (TUG1) in colon cancer (Cc) and related molecular mechanisms.

MATERIALS AND METHODS

RT-qPCR, Western blot and immunohistochemistry were used to detect the expression of related proteins. BrdU and Transwell assays were used to detect cell proliferation and invasion, respectively. Immunofluorescence was used to detect the expression of Vimentin.

KEY FINDINGS

TUG1 expression was up-regulated in CaCO-2, SW620 and HT-29 cells, while miR-26a-5p was down-regulated. Bioinformatics analysis showed that miR-26a-5p was the target of TUG1, and the targeting relationship was further confirmed by dual-luciferase report analysis. Besides, matrix metalloproteinases-14 (MMP-14) was a target of mir-26a-5p. Knockdown of TUG1 by shRNA (sh-TUG1) inhibited MMP-14 expression. Functional analysis showed that sh-TUG1 significantly inhibited Cc cell proliferation, invasion and epithelial-mesenchymal transformation (EMT). Notably, miR-26a-5p inhibitor reversed the promotion of Cc caused by sh-TUG1. Mechanically, the overexpression of TUG1 significantly up-regulated the levels of MMP-14, VEGF, p-p38 mitogen-activated protein kinase (p-p38 MAPK) and p-HSP27 (heat shock protein 27), and promoted the proliferation, invasion and EMT of Cc cells. However, MAPK pathway inhibitor SB203580 has shown the opposite effect. Additionally, animal studies have shown that sh-TUG1 inhibited tumor growth and motility in vivo in the same way.

SIGNIFICANCE

This study demonstrated that TUG1 accelerates the development of colon cancer by regulating miR-26a-5p/MMP14/p38 MAPK/Hsp27 axis in vitro and in vivo. Therefore, TUG1 provides a new direction for the treatment of Cc.

Metabolite profiling and in-vitro colon cancer protective activity of Cycas revoluta cone extract

The methanolic extract of Cycas revoluta cone (MECR) was analyzed by GC-MS and UHPLC for metabolite profiling and was evaluated for anti-colon cancer property by using in vitro assays like Cell Viability Assay, Colony Formation Assay, ROS Determination, Flowcytometry, DAPI staining assay, Tunel assay. GC-MS and HPLC analysis confirmed the presence of different phytochemicals in the extract of Cycas revoluta cone. In-vitro studies showed MECR extract showed significant anti-colon cancer activity by reducing proliferation and inducing apoptosis in colon cancer cell (HCT-8) line, but no such activity was seen in normal colon cell (CCD-18Co) line. The investigation confirms that MECR may be a promising candidate in colon cancer protection.

miR-34a Regulates Multidrug Resistance via Positively Modulating OAZ2 Signaling in Colon Cancer Cells

Although aberrant expression of miR-34a, an essential tumor suppressor miRNA, has been frequently observed in colon cancer (CCa), whether miR-34a can regulate CCa progression by modulating other facets of this malignancy (such as multidrug resistance, MDR) remains unknown. Here, we report for the first time that miR-34a expression was significantly downregulated in clinical CCa samples from oxaliplatin-resistant patients and in experimentally established multidrug-resistant CCa cells. By using histoculture drug response assay, we further confirmed that clinical CCa samples with lower miR-34a expression appeared to be more resistant to chemotherapy. Functionally, ectopic expression of exogenous miR-34a resensitized multidrug-resistant HCT-8/OR cells to oxaliplatin treatment, whereas miR-34a inhibition augmented the oxaliplatin resistance in chemosensitive HCT-8 cells. Mechanistically, miR-34a positively regulated the mRNA stability of the ornithine decarboxylase antizyme 2 (OAZ2) by directly targeting its three prime untranslated region (3′UTR). Consequently, suppression of the expression of miR-34a/OAZ2 signaling by chemotherapeutic agents significantly enhanced the activation of MDR-associated ATP-binding cassette (ABC) transporters and antiapoptosis pathways, thus leading to MDR development in CCa cells. Collectively, our combined analysis reveals a critical role of miR-34a/OAZ2 cascade in conferring a proper cellular response to CCa chemotherapy.

Over-activation of AKT signaling leading to 5-Fluorouracil resistance in SNU-C5/5-FU cells

Here, we investigated whether over-activation of AKT pathway is important in the resistance to 5-fluorouracil (5-FU) in SNU-C5/5-FU cells, 5-FU-resistant human colon cancer cells. When compared to wild type SNU-C5 cells (WT), SNU-C5/5-FU cells showed over-activation of PI3K/AKT pathway, like increased phosphorylation of AKT, mTOR, and GSK-3β, nuclear localization of β-catenin, and decreased E-cadherin. Moreover, E-cadherin level was down-regulated in recurrent colon cancer tissues compared to primary colon cancer tissues. Gene silencing of AKT1 or treatment of LY294002 (PI3 kinase inhibitor) increased E-cadherin, whereas decreased phospho-GSK-3β. LY294002 also reduced protein level of β-catenin with no influence on mRNA level. PTEN level was higher in SNU-C5/WT than SNU-C5/5-FU cells, whereas the loss of PETN in SNU-C5/WT cells induced characteristics of SNU-C5/5-FU cells. In SNU-C5/5-FU cells, NF-κB signaling was activated, along with the overexpression of COX-2 and stabilization of survivin. However, increased COX-2 contributed to the stabilization of survivin, which directly interacts with cytoplasmic procaspase-3, while the inhibition of AKT reduced this cascade. We finally confirmed that combination treatment with 5-FU and LY294002 or Vioxx could induce apoptosis in SNU-C5/5-FU cells. These data suggest that inhibition of AKT activation may overcome 5-FU-resistance in SNU-C5/5-FU cells. These findings provide evidence that over-activation of AKT is crucial for the acquisition of resistance to anticancer drugs and AKT pathway could be a therapeutic target for cancer treatment.

Multidrug Resistance-Associated Protein 2 (MRP2) Mediated Transport of Oxaliplatin-Derived Platinum in Membrane Vesicles

The platinum-based anticancer drug oxaliplatin is important clinically in cancer treatment. However, the role of multidrug resistance-associated protein 2 (MRP2) in controlling oxaliplatin membrane transport, in vivo handling, toxicity and therapeutic responses is unclear. In the current study, preparations of MRP2-expressing and control membrane vesicles, containing inside-out orientated vesicles, were used to directly characterise the membrane transport of oxaliplatin-derived platinum measured by inductively coupled plasma mass spectrometry. Oxaliplatin inhibited the ATP-dependent accumulation of the model MRP2 fluorescent probe, 5(6)-carboxy-2,'7'-dichlorofluorescein, in MRP2-expressing membrane vesicles. MRP2-expressing membrane vesicles accumulated up to 19-fold more platinum during their incubation with oxaliplatin and ATP as compared to control membrane vesicles and in the absence of ATP. The rate of ATP-dependent MRP2-mediated active transport of oxaliplatin-derived platinum increased non-linearly with increasing oxaliplatin exposure concentration, approaching a plateau value (Vmax) of 2680 pmol Pt/mg protein/10 minutes (95%CI, 2010 to 3360 pmol Pt/mg protein/10 minutes), with the half-maximal platinum accumulation rate (Km) at an oxaliplatin exposure concentration of 301 μM (95% CI, 163 to 438 μM), in accordance with Michaelis-Menten kinetics (r² = 0.954). MRP2 inhibitors (myricetin and MK571) reduced the ATP-dependent accumulation of oxaliplatin-derived platinum in MRP2-expressing membrane vesicles in a concentration-dependent manner. To identify whether oxaliplatin, or perhaps a degradation product, was the likely substrate for this active transport, HPLC studies were undertaken showing that oxaliplatin degraded slowly in membrane vesicle incubation buffer containing chloride ions and glutathione, with approximately 95% remaining intact after a 10 minute incubation time and a degradation half-life of 2.24 hours (95%CI, 2.08 to 2.43 hours). In conclusion, MRP2 mediates the ATP-dependent active membrane transport of oxaliplatin-derived platinum. Intact oxaliplatin and its anionic monochloro oxalate ring-opened intermediate appear likely candidates as substrates for MRP2-mediated transport.

Role of ABC transporters in fluoropyrimidine-based chemotherapy response

Since over 50 years, 5-fluorouracil (5-FU) is in use as backbone of chemotherapy treatment regimens for a wide range of cancers including colon, breast, and head and neck carcinomas. However, drug resistance and severe toxicities such as mucositis, diarrhea, neutropenia, and vomiting in up to 40% of treated patients often lead to dose limitation or treatment discontinuation. Because the oral bioavailability of 5-FU is unpredictable and highly variable, 5-FU is commonly administered intravenously. To overcome medical complications and inconvenience associated with intravenous administration, the oral prodrugs capecitabine and tegafur have been developed. Both fluoropyrimidines are metabolically converted intracellularly to 5-FU, which then needs metabolic activation to exert its damaging activity on RNA and DNA. The low response rates of 10-15% of 5-FU monotherapy can be improved by combination regimens of infusional 5-FU and leucovorin together with oxaliplatin (FOLFOX) or irinotecan (FOLFIRI), thereby increasing response rates to 30-40%. The impact of metabolizing enzymes in the development of fluoropyrimidine toxicity and resistance has been studied in great detail. In addition, membrane drug transporters, which are critical determinants of intracellular drug concentrations, may play a role in occurrence of toxicity and development of resistance against fluoropyrimidine-based therapy as well. This review therefore summarizes current knowledge on the role of drug transporters with particular focus on ATP-binding cassette transporters in fluoropyrimidine-based chemotherapy response.

miR-34a-5p suppresses colorectal cancer metastasis and predicts recurrence in patients with stage II/III colorectal cancer

Although surgery remains the mainstay of curative treatment for colorectal cancer (CRC), many patients still have high chance to experience disease relapse. It is therefore imperative to identify prognostic markers that can help predict the clinical outcomes of CRC. Aberrant microRNA expression holds great potential as diagnostic and prognostic biomarker for CRC. Here we aimed to investigate clinical potential of miR-34a-5p as a prognostic marker for CRC recurrence and its functional significance. First, we validated that miR-34a-5p was downregulated in CRC tumour tissues (P<0.05). The expression level of tissue miR-34a-5p was then evaluated in two independent cohorts of 268 CRC patients. miR-34a-5p expression was positively correlated with disease-free survival in two independent cohorts (cohort I: n=205, P<0.001; cohort II: n=63, P=0.006). Moreover, the expression of miR-34a-5p was an independent prognostic factor for CRC recurrence by multivariate analysis (P<0.001 for cohort I, P=0.007 for cohort II). Ectopic expression of miR-34a-5p in p53 wild-type colon cancer cell HCT116 significantly inhibited cell growth, migration, invasion and metastasis. miR-34a-5p induced cell apoptosis, cell cycle arrest at G1 phase and p53 transcription activity in HCT116 cells, but not in the HCT116 p53 knockout (p53(-/-)) cells. miR-34a-5p significantly suppressed the HCT116 growth in vivo, whereas it showed no effect on the HCT116 p53(-/-) xenograft, indicating that the growth-inhibiting effect by miR-34a-5p was dependent on p53. In addition, the expression level of miR-34a-5p in patients with p53-positive expression was higher than that in patients with p53-negative expression (P<0.01). In conclusion, miR-34a-5p inhibits recurrence of CRC through inhibiting cell growth, migration and invasion, inducing cell apoptosis and cell cycle arrest in a p53-dependent manner.

miR-34a-5p suppresses colorectal cancer metastasis and predicts recurrence in patients with stage II/III colorectal cancer

Although surgery remains the mainstay of curative treatment for colorectal cancer (CRC), many patients still have high chance to experience disease relapse. It is therefore imperative to identify prognostic markers that can help predict the clinical outcomes of CRC. Aberrant microRNA expression holds great potential as diagnostic and prognostic biomarker for CRC. Here we aimed to investigate clinical potential of miR-34a-5p as a prognostic marker for CRC recurrence and its functional significance. First, we validated that miR-34a-5p was downregulated in CRC tumour tissues (P<0.05). The expression level of tissue miR-34a-5p was then evaluated in two independent cohorts of 268 CRC patients. miR-34a-5p expression was positively correlated with disease-free survival in two independent cohorts (cohort I: n=205, P<0.001; cohort II: n=63, P=0.006). Moreover, the expression of miR-34a-5p was an independent prognostic factor for CRC recurrence by multivariate analysis (P<0.001 for cohort I, P=0.007 for cohort II). Ectopic expression of miR-34a-5p in p53 wild-type colon cancer cell HCT116 significantly inhibited cell growth, migration, invasion and metastasis. miR-34a-5p induced cell apoptosis, cell cycle arrest at G1 phase and p53 transcription activity in HCT116 cells, but not in the HCT116 p53 knockout (p53(-/-)) cells. miR-34a-5p significantly suppressed the HCT116 growth in vivo, whereas it showed no effect on the HCT116 p53(-/-) xenograft, indicating that the growth-inhibiting effect by miR-34a-5p was dependent on p53. In addition, the expression level of miR-34a-5p in patients with p53-positive expression was higher than that in patients with p53-negative expression (P<0.01). In conclusion, miR-34a-5p inhibits recurrence of CRC through inhibiting cell growth, migration and invasion, inducing cell apoptosis and cell cycle arrest in a p53-dependent manner.

Expression of indocyanine green-related transporters in hepatocellular carcinoma

BACKGROUND

Indocyanine green (ICG), an organic anion used in liver function tests, is known to accumulate in hepatocellular carcinoma (HCC) tissues after an intravenous injection. Because the intratumoral expression of transporters for chemical agents influences the behaviors of some malignant tumors, we investigated whether the expression of ICG-related transporters influenced the clinicopathologic features of HCC.

MATERIALS AND METHODS

ICG accumulation patterns were examined using near-infrared spectroscopy and the protein expression of ICG-related transporters was assessed using immunohistochemistry and immunoblotting in 40 resected HCC specimens. We also determined whether the intratumor expression of these transporters affected intratumor lipid composition by imaging mass spectrometry.

RESULTS

Immunoblot analysis revealed that the expression of organic anion transporting polypeptide 1B3 (OATP1B3) and multidrug resistance p-glycoprotein (MDR)-3, as influx and efflux transporters, respectively, were significantly higher in ICG-accumulated HCC (ICG-high HCC) than in ICG-low HCC. ICG was fluorescently observed in the pseudoglands and bile canaliculi abundantly expressing MDR3. An immunohistochemical examination revealed significantly worse disease-free and overall survival rates in patients with MDR3-negative HCC, in which the intratumoral accumulation of some phosphatidylcholine species was observed under imaging mass spectrometry.

CONCLUSIONS

The intratumoral expression of MDR3, a key efflux transporter of ICG, affected the prognosis of patients with HCC, presumably by altering the lipid composition of the lipid bilayers.

Drug resistance reversed by silencing LIM domain-containing protein 1 expression in colorectal carcinoma

The role of LIM domain-containing protein 1 (LIMD1) in the multidrug resistance of colorectal carcinoma (CRC) has not yet been established. The aim of the current study was to investigate the chemosensitivity of CRC multidrug-resistant (MDR) cells following the silencing of LIMD1. The MDR phenotypic Colo205 and HCT-8 cell lines were examined, which were established by exposure to increasing doses of 5-fluorouracil (5-FU) over a period of one year. LIMD1 siRNA constructs were transfected into CRC MDR cells and the phenotypic effects were determined comprehensively. The Colo205 and HCT-8 cell lines were more resistant to 5-FU compared with their respective parental cell lines. In addition, the two MDR cell types expressed significantly more LIMD1 compared with their parental lines. The stably transfected cells showed various degrees of reversal of the MDR phenotype, and 5-FU-induced apoptosis was increased in the transfected cells compared with the controls. In conclusion, RNA interference targeting LIMD1 may present a novel therapeutic option for CRC.

A functional germline variant in GLI1 implicates hedgehog signaling in clinical outcome of stage II and III colon carcinoma patients

PURPOSE

Cumulating evidence indicates that germline variants in the Wnt, Notch, and Hedgehog pathways are involved in colon carcinoma progression and metastasis. We investigated germline polymorphisms in a comprehensive panel of Wnt, Notch, and Hedgehog pathway genes to predict time to recurrence (TTR) and overall survival in patients with stage II and III colon carcinoma.

EXPERIMENTAL DESIGN

A total of 742 consecutively collected patients with stage II and III colon carcinoma were included in this retrospective study. Genomic DNA was analyzed for 18 germline polymorphisms in Wnt, Notch, and Hedgehog pathway genes (SFRP, DKK 2 and 3, AXIN2, APC, MYC, TCF7L2, NOTCH2, and GLI1) by TaqMan 5'-exonuclease assays.

RESULTS

In univariate analysis, the homozygous mutant variant of GLI1 rs2228226 G>C was significantly associated with decreased TTR in a recessive genetic model after adjustment for multiple testing [HR = 2.35; confidence interval (95% CI), 1.48-3.74; P < 0.001] and remained significant in multivariate analysis including clinical stage, lymphovascular-, vascular-, and perineural-invasion (HR = 2.43; CI 95%, 1.52-3.87; P < 0.001). In subanalyses, the association was limited to patients with surgery alone (HR = 3.21; CI 95%, 1.59-6.49; P = 0.001), in contrast with patients with adjuvant chemotherapy (HR = 0.82; CI 95%, 0.35-1.95; P = 0.657). When the subgroup of patients with "high-risk" GLI1 rs2228226 C/C genotype was analyzed, no benefit of adjuvant 5-fluorouracil-based chemotherapy could be found.

CONCLUSION

This is the first study identifying GLI1 rs2228226 G>C as an independent prognostic marker in patients with stage II and III colon carcinoma. Prospective studies are warranted to validate our findings.