ABCB1/MDR1 gene polymorphism and colorectal cancer risk: a meta-analysis of case-control studies

Association of ABCB1 Polymorphisms with Efficacy and Adverse Drug Reactions of Valproic Acid in Children with Epilepsy

Genetic polymorphisms in ATP-binding cassette subfamily B member 1 (ABCB1, also known as MDR1) have been reported to be possibly associated with the regulation of response to antiseizure medications. The aim of this study was to investigate the association of ABCB1 polymorphisms with the efficacy of and adverse drug reactions to valproic acid among Chinese children with epilepsy. A total of 170 children from southern China with epilepsy treated with valproic acid for more than one year were recruited, including 61 patients with persistent seizures and 109 patients who were seizure-free. Two single nucleotide polymorphisms of ABCB1, rs1128503 and rs3789243, were genotyped using the Sequenom MassArray system. The two single nucleotide polymorphisms of ABCB1 were found to be significantly associated with treatment outcomes of valproic acid in children with epilepsy. Carriers with the TT genotype of ABCB1 rs1128503 were more inclined to exhibit persistent seizures after treatment with valproic acid (p = 0.013). The CC genotype of rs3789243 was observed to be a potential protective factor for valproic acid-induced gastrointestinal adverse drug reactions (p = 0.018), but possibly increased the risk of valproic acid-induced cutaneous adverse drug reactions (p = 0.011). In contrast, the CT genotype of rs3789243 was associated with a lower risk of valproic acid-induced cutaneous adverse drug reactions (p = 0.011). Haplotype analysis showed that CC haplotype carriers tended to respond better to valproic acid treatment (p = 0.009). Additionally, no significant association was found between ABCB1 polymorphisms and serum concentrations of valproic acid. This study revealed that the polymorphisms and haplotypes of the ABCB1 gene might be associated with the treatment outcomes of valproic acid in Chinese children with epilepsy.

Low Blood-As Levels and Selected Genotypes Appears to Be Promising Biomarkers for Occurrence of Colorectal Cancer in Women

In following study we examined whether blood arsenic (As) levels combined with specific polymorphisms in MT1B, GSTP1, ABCB1, NQO1, CRTC3, GPX1, SOD2, CAT, XRCC1, ERCC2 can be used as a marker for the detection of colorectal cancer (CRC) among Polish women. A retrospective case-control study of CRC included 83 CRC cases and 78 healthy controls. From each study participant pre-treatment peripheral blood was collected for As level measurement by inductively coupled–plasma mass spectrometry (ICP-MS). We estimated the odds ratio (OR) of the association between blood-As levels and CRC using multivariable unconditional logistic regression models. A low blood-As level (0.27–0.67 µg/L) was associated with an increased frequency of CRC (OR: 3.69; p = 0.005). This correlation was significantly greater when participants carried particular gene variants: CAT, rs1001179-nonCC (OR: 19.4; p = 0.001); ABCB1 rs2032582–CC (OR: 14.8; p = 0.024); GPX1 rs1050450-CC (OR: 11.6; p = 0.002) and CRTC3 rs12915189-nonGG (OR: 10.3; p = 0.003). Our study provides strong evidence that low blood-As levels are significantly associated with increased CRC occurrence and that particular gene variants significantly enhanced this correlation however, due to the novelty of these findings, we suggest further validation before a definitive statement that the combined effect of low blood-As levels with specific gene polymorphisms is a suitable CRC biomarker.

ABCB1 and ABCG2 restricts the efficacy of gedatolisib (PF-05212384), a PI3K inhibitor in colorectal cancer cells

Background

Overexpression of ABC transporters is a big challenge on cancer therapy which will lead cancer cells resistance to a series of anticancer drugs. Gedatolisib is a dual PI3K and mTOR inhibitor which is under clinical evaluation for multiple types of malignancies, including colorectal cancer. The growth inhibitory effects of gedatolisib on colorectal cancer cells have been specifically studied. However, the role of ABC transporters on gedatolisib resistance remained unclear. In present study, we illustrated the role of ABC transporters on gedatolisib resistance in colorectal cancer cells.

Methods

Cell viability investigations of gedatolisib on colorectal cancer cells were determined by MTT assays. The verapamil and Ko143 reversal studies were determined by MTT assays as well. ABCB1 and/or ABCG2 siRNA interference assays were conducted to verify the role of ABCB1- and ABCG2-overexpression on gedatolisib resistance. The accumulation assays of gedatolisib were conducted using tritium-labeled paclitaxel and mitoxantrone. The effects of gedatolisib on ATPase activity of ABCB1 or ABCG2 were conducted using PREDEASY ATPase Kits. The expression level of ABCB1 and ABCG2 after gedatolisib treatment were conducted by Western blotting and immunofluorescence assays. The well-docked position of gedatolisib with crystal structure of ABCB1 and ABCG2 were simulated by Autodock vina software. One-way ANOVA was used for the statistics analysis.

Results

Gedatolisib competitively increased the accumulation of tritium-labeled substrate-drugs in both ABCB1- and ABCG2-overexpression colorectal cancer cells. Moreover, gedatolisib significantly increased the protein expression level of ABCB1 and ABCG2 in colorectal cancer cells. In addition, gedatolisib remarkably simulated the ATPase activity of both ABCB1 and ABCG2, suggesting that gedatolisib is a substrate drug of both ABCB1 and ABCG2 transporters. Furthermore, a gedatolisib-resistance colorectal cancer cell line, SW620/GEDA, was selected by increasingly treatment with gedatolisib to SW620 cells. The SW620/GEDA cell line was proved to resistant to gedatolisib and a series of chemotherapeutic drugs, except cisplatin. The ABCB1 and ABCG2 were observed overexpression in SW620/GEDA cell line.

Conclusions

These findings suggest that overexpression of ABCB1 and ABCG2 may restrict the efficacy of gedatolisib in colorectal cancer cells, while co-administration with ABC transporter inhibitors may improve the potency of gedatolisib.

Sapitinib Reverses Anticancer Drug Resistance in Colon Cancer Cells Overexpressing the ABCB1 Transporter

The efficacy of anti-cancer drugs in patients can be attenuated by the development of multi-drug resistance (MDR) due to ATP-binding cassette (ABC) transporters overexpression. In this in vitro study, we determined the reversal efficacy of the epidermal growth factor receptor (EFGR) inhibitor, saptinib, in SW620 and SW720/Ad300 colon cancer cells and HEK293/ABCB1 cells which overexpress the ABCB1 transporter. Sapitinib significantly increased the efficacy of paclitaxel and doxorubicin in ABCB1 overexpressing cells without altering the expression or the subcellular location of the ABCB1 transporter. Sapitinib significantly increased the accumulation of [³H]-paclitaxel in SW620/AD300 cells probably by stimulating ATPase activity which could competitively inhibit the uptake of [³H]-paclitaxel. Furthermore, sapitinib inhibited the growth of resistant multicellular tumor spheroids (MCTS). The docking study indicated that sapitinib interacted with the efflux site of ABCB1 transporter by π-π interaction and two hydrogen bonds. In conclusion, our study suggests that sapitinib surmounts MDR mediated by ABCB1 transporter in cancer cells.

Association between MDR1 polymorphisms and XELIRI and XELOX chemoresistance in Saudi patients with colorectal cancer

Multidrug resistance member 1 (MDR1) is located on chromosome 7 and encodes P-glycoprotein, which is universally accepted as a drug resistance biomarker. MDR1 polymorphisms can alter protein expression or function, which has been previously reported to associate with various types of malignancies, such as colorectal cancer (CRC). Therefore, the present study aimed to determine the effects of MDR1 polymorphisms on drug responses of Saudi patients with CRC. DNA samples were obtained from 62 patients with CRC and 100 healthy controls. Genotypes and allele frequencies of MDR1 single nucleotide polymorphisms (SNPs) G2677T and T1236C were determined using the PCR-restriction fragment length polymorphism procedure. The results showed no significant differences in the genotype distribution and allele frequency of T1236C between patients with CRC and controls. However, G2677T was found to serve a highly significant role in protecting against the progression of CRC. In addition, none of the genotypes in SNPs T1236C and G2677T was found to affect chemoresistance to XELIRI and XELOX. In conclusion, although T1236C in the MDR1 gene is not associated with CRC risk, G2677T protects against the development of CRC. Neither of the MDR1 SNPs tested were associated with the risk of chemoresistance. Therefore, these two SNPs cannot be used as molecular markers for predicting drug response in patients with CRC.

Impact of genetic variants of ABCB1, APOB, CAV1, and NAMPT on susceptibility to pancreatic ductal adenocarcinoma in Chinese patients

BACKGROUND

Among the different types of cancer, pancreatic cancer, particularly pancreatic ductal adenocarcinoma (PDAC), is the most lethal malignancy, with poor early detection rates and prognosis. The aim of the present study was to investigate the potential genetic effects of the single-nucleotide polymorphisms (SNPs) in ABCB1 (rs1045642, rs3789243, rs4148737), APOB (rs693, rs1042031), CAV1 (rs12672038, rs1997623, rs3807987, rs7804372), and NAMPT (rs9034, rs2505568, rs61330082) on PDAC.

METHODS

A total of 273 patients with PDAC and 263 healthy controls were genotyped using PCR and direct Sanger sequencing. Unconditional logistic regression models were used to evaluate the potential effects of the genotypes, alleles, and haplotypes on the risk of developing PDAC.

RESULTS

Patients with PDAC possessed a considerably lower frequency of genotypes AG, GG, and allele G at ABCB1 rs4148737 compared with controls. Based on age, sex, smoking status, drinking status, diabetes, and family history of cancer, stratified analyses showed a significant correlation between SNPs at rs4148737 and PDAC. According to specific SNPs, eight haplotypes were constructed along with ABCB1 rs4148737, rs1045642, and rs3789243. Carriers with haplotypes ACC and ATC were more susceptible to developing PDAC, whereas haplotypes GCC and GTC were associated with a reduced likelihood of developing PDAC. The distributions of the other SNPs in each group were not significantly associated with PDAC risk.

CONCLUSIONS

These results suggested that genetic polymorphisms of ABCB1 rs4148737 may influence an individual's risk of developing PDAC.

Association between ABCB1 (3435C>T) polymorphism and susceptibility of colorectal cancer: A meta-analysis

Studies on the relationship between ABCB1 3435C>T polymorphism (rs1045642) and colorectal cancer (CRC)susceptibility have yielded inconclusive results. To clarify this issue, we undertook a meta-analysis to investigate the relationship between rs1045642 and CRC risk.Three electronic scientific publication databases (Cochrane Library, Pubmed, Embase) were screened using specific search terms. Relevant literature was identified using literature traceability methods. Selected publications were evaluated according to the inclusion and exclusion criteria. Effect size information (odds ratio and the corresponding 95% confidence interval [CI]) was obtained following quality assessment and data extraction from the included publications, and a meta-analysis conducted. Statistical analysis was performed with the Stata sofz (Version 13.0) software.Overall, 17 case-control studies involving 7129 CRC patients and 7710 healthy control subjects satisfied the criteria for inclusion in the meta-analysis. There was no significant association between ABCB1 3435C>T polymorphism and CRC risk in any of the genetic models. In the CC versus CT model (I = 20.9%, Pheterogeneity = .276), CC versus CT + TT model (I = 45.6%, Pheterogeneity = .102) and CT versus CC + TT model (I = 17.8%, Pheterogeneity = .298) analyses, between-study heterogeneities were detected as significant in Asian populations. In the CT versus TT model (I = 24%, Pheterogeneity = .254) and CC + CT versus TT model (I = 0, Pheterogeneity = .55), between-study heterogeneities were found to be significant in groups of different populations.The meta-analysis described here suggests that the ABCB1 3435C>T polymorphism is not related to CRC susceptibility.

Association between ABCB1, ABCG2 carrier protein and COX-2 enzyme gene polymorphisms and breast cancer risk in a Turkish population

Aim

Breast cancer is the most common cancer and the second leading cause of cancer-related deaths among women. Several genetic and environmental factors are known to be involved in breast cancer pathogenesis, but the exact etiology of this disease is complicated and not completely understood. We aimed to investigate whether the gene polymorphisms of ABCB1 and ABCG2 carrier proteins and COX-2 enzyme affect breast cancer risk.

Method

ABCG2 C421A (rs2231142), ABCB1 C3435T (rs1045642), COX-2 T8473C (rs5275) and COX-2 G306C (rs5277) were genotyped 104 breast cancer patients and 90 healthy controls using a real-time PCR for breast cancer susceptibility.

Results

Patients carrying ABCG2 C421A, the CC genotype, had a higher risk of disease compared with patients carrying any A allele (OR = 3.06; 95% CI = 1.49–6.25, p = 0.0019). The other variants showed no association with breast cancer (p > 0.05). Comparing the pathological parameters with the variants, only, the frequency of C allele of ABCB1 C3435T was significantly lower in the estrogen receptor-α (ERα) (OR = 2.25; 95% CI: 0.75–6.76; p = 0.041) and progesterone receptor (PgR) (OR = 3.67; 95% CI: 1.34–10.03; p = 0.008) positive breast cancer patients.

Conclusion

ABCB1 C3435T and ABCG2 C421A might represent a potential risk factor for breast cancer for Turkish women.

ABCB1 variants C3435T and T129C are not associated with colorectal cancer risk

Background

Colorectal cancer (CRC) is one of the most prevalent cancers in Saudi Arabia that is highly characterized with poor survival rate and advanced metastasis. Many studies contribute this poor outcome to the expression of ABC transporters on the surface of cancer cells.

Objectives

In this study, two ABCB1 variants, C3435T and T129C, were examined to evaluate their contribution to CRC risk.

Methods

125 subjects (62 CRC patients and 63 healthy controls) were involved. The DNA was isolated and analyzed with PCR-RFLP to determine the different genotypes. The hardy-Weinberg equilibrium was performed to determine genotype distribution and allele frequencies. Fisher's exact test (two-tailed) was used to compare allele frequencies between patients and control subjects.

Results

The study showed that for SNP C3435T, the population of both CRC patients and controls were out of Hardy-Weinberg equilibrium. Genotype distribution for CRC patients was (Goodness of fit χ2 = 20, df= 1, P≤0.05), whereas, for the controls the genotype distribution was (Goodness of fit χ2 = 21, df =1, P ≤0.05). For SNP T129C, all subjects showed normal (TT) genotype.

Conclusion

There was no significant association between ABCB1 3435C>T and 129T>C polymorphisms with CRC risk.

Low penetrance genetic polymorphisms as potential biomarkers for colorectal cancer predisposition

Colorectal cancer is a leading form of cancer in both males and females. Early detection of individuals at risk of colorectal cancer allows proper treatment and management of the disease to be implemented, which can potentially reduce the burden of colorectal cancer incidence, morbidity and mortality. In recent years, the role of genetic susceptibility factors in mediating predisposition to colorectal cancer has become more and more apparent. Identification of high-frequency, low-penetrance genetic polymorphisms associated with the cancer has therefore emerged as an important approach which can potentially aid prediction of colorectal cancer risk. However, the overwhelming amount of genetic epidemiology data generated over the past decades has made it difficult for one to assimilate the information and determine the exact genetic polymorphisms that can potentially be used as biomarkers for colorectal cancer. This review comprehensively consolidates, based primarily on results from meta-analyses, the recent progresses in the search of colorectal cancer-associated genetic polymorphisms, and discusses the possible mechanisms involved.

Common variants in glucuronidation enzymes and membrane transporters as potential risk factors for colorectal cancer: a case control study

Background

Associations between polymorphisms of UDP-glucuronosyltransferases (UGTs) or efflux transporters (e.g., P-glycoprotein and MRP2) and different types of cancer have been described, whereas the role of influx transporters (e.g. OATP1B1 and OATP2B1) has been seldom explored. The GenColon study investigated potential associations between variant alleles of UGTs, efflux and influx transporters and CRC.

Methods

Three hundred CRC cases were matched with 300 controls for age, sex and enrolment site. Fifteen SNPs in UGT1A6–9, UGT2B7, ABCB1, ABCC2, SLCO1B1 and SLCO2B1 genes were characterized using Taqman® PCR. Using multivariate conditional logistic regression, we investigated the relationships between CRC and “environmental” risk factors (physical activity, housing and working areas, consumption of red meat, tobacco, alcohol); genetic polymorphisms, in the study population and in the subgroups with “environmental” risk factors.

Results

No significant association was observed for the analyzed SNPs (or haplotypes). However, an increased CRC risk was found in carriers of the UGT1A8 rs1042597-G variant allele (additive risk OR = 3.39[1.29–8.89], p = 0.02951) in the subgroup of meat-consumers (n = 84), and in carriers of the ABCB1 rs1045642-T (exon26) variant allele (additive risk; OR = 1.89[1.10–3.39], p = 0.0257) in the “never alcohol consumption subgroup” (n = 125). In addition, as previously reported, the following CRC risk factors were identified: absence of physical activity (OR = 6.35[3.70–10.9], p < 0.0001), living or working in rural or mix area (OR = 2.50[1.48–4.23], p = 0.0006 and OR = 2.99[1.63–5.48], p = 0.004, respectively) and tobacco exposure >30 years (3.37[1.63–6.96], p = 0.0010).

Conclusions

Variant genotypes of influx transporters (OATP1B1 and 2B1) were not associated with CRC. This study confirmed the influence of lifestyle factors, but not the previously reported detrimental effect of SNPs in intestinal UGTs or efflux transporters, except for a UGT1A8 variant in subjects consuming meat and the exon 26 SNP of ABCB1 in the never alcohol consumption subgroup.

Trial registration

Registered in Direction Générale de la Santé the 1st July 2008 under the number DGS2008–0144.

Electronic supplementary material

The online version of this article (10.1186/s12885-017-3728-0) contains supplementary material, which is available to authorized users.

MDR1A deficiency restrains tumor growth in murine colitis-associated carcinogenesis

Patients with Ulcerative Colitis (UC) have an increased risk to develop colitis-associated colorectal cancer (CAC). Here, we found that protein expression of ABCB1 (ATP Binding Cassette Subfamily B Member 1) / MDR1 (multidrug resistance 1) was diminished in the intestinal mucosa of patients with active UC with or without CAC, but not in non-UC patients with sporadic colon cancer. We investigated the consequences of ABCB1/MDR1 loss-of-function in a common murine model for CAC (AOM/DSS). Mice deficient in MDR1A (MDR1A KO) showed enhanced intratumoral inflammation and cellular damage, which were associated with reduced colonic tumor size and decreased degree of dysplasia, when compared to wild-type (WT). Increased cell injury correlated with reduced capacity for growth of MDR1A KO tumor spheroids cultured ex-vivo. Gene expression analysis by microarray demonstrated that MDR1A deficiency shaped the inflammatory response towards an anti-tumorigenic microenvironment by downregulating genes known to be important mediators of cancer progression (PTGS2 (COX2), EREG, IL-11). MDR1A KO tumors showed increased gene expression of TNFSF10 (TRAIL), a known inducer of cancer cell death, and CCL12, a strong trigger of B cell chemotaxis. Abundant B220+ B lymphocyte infiltrates with interspersed CD138+ plasma cells were recruited to the MDR1A KO tumor microenvironment, concomitant with high levels of immunoglobulin light chain genes. In contrast, MDR1A deficiency in RAG2 KO mice that lack both B and T cells aggravated colonic tumor progression. MDR1A KO CD19+ B cells, but not WT CD19+ B cells, suppressed growth of colonic tumor-derived spheroids from AOM/DSS-WT mice in an ex-vivo co-culture system, implying that B-cell regulated immune responses contributed to delayed tumor development in MDR1A deficiency. In conclusion, we provide first evidence that loss of ABCB1/MDR1 function may represent an essential tumor-suppressive host defense mechanism in CAC.

Overexpression of long non-coding RNA GHET1 promotes the development of multidrug resistance in gastric cancer cells

BACKGROUND AND AMID

Multidrug resistance (MDR) is the main obstacle to successful chemotherapy for patients with gastric cancer (GC). The GHET1 affects a variety of cancer development, and increased GHET1 promotes gastric carcinoma cell proliferation. This study amid to investigate the effect of GHET1 on the development of MDR in gastric cancer cells.

METHODS AND RESULTS

In this study, we observed an increased expression levels of GHET1 in drug-resistant gastric cancer patients and cisplatin-resistant gastric cancer cell lines (BGC823/DPP and SGC7901/DDP cell line). Next, the two cell lines were used to in vitro validation of the effect of GHET1 expression on the MDR development. Silence of GHET1 in the two cisplatin-resistant gastric cancer cell lines inhibited the MDR with rising inhibition rate tested by MTT (methyl thiazolyl tetrazolium) assay. The apoptotic cell rate was analyzed by staining with Annexin V/PI. The results showed that the IC50 (half maximal inhibitory concentration) of the two cisplatin-resistant gastric cancer cell lines transfected with si-GHET1 were significantly reduced. Contrary to inhibition of GHET1 in the two cisplatin-resistant gastric cancer cell lines, we found that overexpression of GHET1 reduced sensitivity of BGC823 and SGC7901 cells to cisplatin with decreased inhibition rate and apoptotic cell rate and increased IC50. Furthermore, the qRT-PCR and western blot results showed that overexpression of GHET1 downregulated Bax expression and upregulated Bcl-2, MDR1 and MRP1 expression in BGC823 and SGC7901 cells.

CONCLUSION

Highly expressing GHET1 promoted the development of MDR which was related to the Bax, Bcl-2, MDR1 and MRP1 genes expression in gastric cancer cells.

Synergistic anticancer effect of exogenous wild-type p53 gene combined with 5-FU in human colon cancer resistant to 5-FU in vivo

AIM

To investigate the anticancer effect of a recombinant adenovirus-mediated p53 (rAd-p53) combined with 5-fluorouracil (5-FU) in human colon cancer resistant to 5-FU in vivo and the mechanism of rAd-p53 in reversal of 5-FU resistance.

METHODS

Nude mice bearing human colon cancer SW480/5-FU (5-FU resistant) were randomly assigned to four groups (n = 25 each): control group, 5-FU group, rAd-p53 group, and rAd-p53 + 5-FU group. At 24 h, 48 h, 72 h, 120 h and 168 h after treatment, 5 mice were randomly selected from each group and sacrificed using an overdose of anesthetics. The tumors were removed and the protein expressions of p53, protein kinase C (PKC), permeability-glycoprotein (P-gp) and multidrug resistance-associated protein 1 (MRP1) (Western blot) and apoptosis (TUNEL) were determined.

RESULTS

The area ratios of tumor cell apoptosis were larger in the rAd/p53 + 5-FU group than that in the control, 5-FU and rAd/p53 groups (P < 0.05), and were larger in the rAd/p53 group than that of the control group (P < 0.05) and the 5-FU group at more than 48 h (P < 0.05). The p53 expression was higher in the rAd/p53 and the rAd/p53 + 5-FU groups than that of the control and 5-FU groups (P < 0.05), and were higher in the rAd/p53 + 5-FU group than that of the rAd/p53 group (P < 0.05). Overexpression of PKC, P-gp and MRP1 was observed in the 5-FU and control groups. In the rAd/p53 + 5-FU group, the expression of P-gp and MRP1 was lower that of the control and 5-FU groups (P < 0.05), and the expression of PKC was lower than that of the control, 5-FU and rAd/p53 groups at more than 48 h (P < 0.05). In the rAd/p53 group, the expression of P-gp and MRP1 was lower that of the control and 5-FU groups at more than 48 h (P < 0.05), and the expression of PKC was lower than that of the control and 5-FU groups at more than 120 h (P < 0.05).

CONCLUSION

5-FU combined with rAd-p53 has a synergistic anticancer effect in SW480/5-FU (5-FU resistance), which contributes to reversal of 5-FU resistance.

Silencing of long non-coding RNA ANRIL inhibits the development of multidrug resistance in gastric cancer cells

The development of multidrug resistance (MDR) is a crucial cause of therapy failure in gastric cancer, which results in disease recurrence and metastasis. Long non-coding RNAs (lncRNAs) have been proven to be critical in carcinogenesis and metastasis of gastric cancer. However, little is known about the roles of ANRIL (antisense non-coding RNA in the INK4 locus) in gastric cancer MDR. The aim of our study is to identify the biological function of ANRIL in gastric cancer MDR. In our results, ANRIL was highly expressed in gastric cancer tissues of cisplatin-resistant and 5-fluorouracil (5-FU)-resistant patients, and the same upregulation trends were observed in cisplatin-resistant cells (BGC823/DDP) and 5-FU-resistant cells (BGC823/5-FU). In addition, BGC823/DDP and BGC823/5-FU cells transfected with ANRIL siRNA and treated with cisplatin or 5-FU, respectively, exhibited significant lower survival rate, decreased invasion capability, and high percentage of apoptotic tumor cells. The influence of ANRIL knockdown on MDR was assessed by measuring IC50 of BGC823/DDP and BGC823/5-FU cells to cisplatin and 5-FU, the result showed that silencing ANRIL decreased the IC50 values in gastric cancer cells. Moreover, qRT-PCR and western blotting revealed that ANRIL knockdown decreased the expression of MDR1 and MRP1, both of which are MDR related genes; regression analysis showed that the expression of ANRIL positively correlated with the expression of MDR1 and MRP1, resprectively In summary, knockdown of lncRNA ANRIL in gastric cancer cells inhibits the development of MDR, suggesting an efficacious target for reversing MDR in gastric cancer therapy.

HIF-1α/MDR1 pathway confers chemoresistance to cisplatin in bladder cancer

Bladder cancer (BCa) is the 9th most common malignant tumor and the 13th leading cause of death due to cancer. The development of surgery and target drugs bring new challenges for the traditional concept for BCa therapy, and chemotherapy is still the final option for many BCa patients, and cisplatin-containing regimen the most effective one. However, the ubiquitous application of cisplatin-containing regimen in BCa results in the cisplatin-resistance, in addition, the cisplatin‑resistant BCa manifests enhanced malignant behavior, the mechanism of which is unclear. In the present study, we used BCa cell lines to to clarify this point. BCa cell lines T24/J82 were pretreated with cisplatin >3 months to construct stable cisplatin-resistant cell lines (tagged T24(Cis-R) and J82(Cis-R)), which manifested as enhanced capacity of proliferation and malignant behavior in vivo and in vitro, accompanied by cisplatin, and even doxorubicin resistance. The following mechanism dissection revealed that prolonged treatment time of T24/J82 cells led to elevated expression of HIF-1α, which targeted the increased expression of MDR1 on the one hand, and contributed to BCa cell proliferation, migration/invasion on the other hand. Finally, IHC staining of human BCa tissue supported our conclusion that the expression of HIF-1α and MDR1 was higher in chemoresistant tissue vs. chemosensitive tissue. Our results provided a new view of HIF-1α in chemotherapy.

Novel understanding of ABC transporters ABCB1/MDR/P-glycoprotein, ABCC2/MRP2, and ABCG2/BCRP in colorectal pathophysiology

AIM: To evaluate ATP-binding cassette (ABC) transporters in colonic pathophysiology as they had recently been related to colorectal cancer (CRC) development.

METHODS: Literature search was conducted on PubMed using combinations of the following terms: ABC transporters, ATP binding cassette transporter proteins, inflammatory bowel disease, ulcerative, colitis, Crohns disease, colorectal cancer, colitis, intestinal inflammation, intestinal carcinogenesis, ABCB1/P-glycoprotein (P-gp/CD243/MDR1), ABCC2/multidrug resistance protein 2 (MRP2) and ABCG2/breast cancer resistance protein (BCRP), Abcb1/Mdr1a, abcc2/Mrp2, abcg2/Bcrp, knock-out mice, tight junction, membrane lipid function.

RESULTS: Recently, human studies reported that changes in the levels of ABC transporters were early events in the adenoma-carcinoma sequence leading to CRC. A link between ABCB1, high fat diet and gut microbes in relation to colitis was suggested by the animal studies. The finding that colitis was preceded by altered gut bacterial composition suggests that deletion of Abcb1 leads to fundamental changes of host-microbiota interaction. Also, high fat diet increases the frequency and severity of colitis in specific pathogen-free Abcb1 KO mice. The Abcb1 KO mice might thus serve as a model in which diet/environmental factors and microbes may be controlled and investigated in relation to intestinal inflammation. Potential molecular mechanisms include defective transport of inflammatory mediators and/or phospholipid translocation from one side to the other of the cell membrane lipid bilayer by ABC transporters affecting inflammatory response and/or function of tight junctions, phagocytosis and vesicle trafficking. Also, diet and microbes give rise to molecules which are potential substrates for the ABC transporters and which may additionally affect ABC transporter function through nuclear receptors and transcriptional regulation. Another critical role of ABCB1 was suggested by the finding that ABCB1 expression identifies a subpopulation of pro-inflammatory Th17 cells which were resistant to treatment with glucocorticoids. The evidence for the involvement of ABCC2 and ABCG2 in colonic pathophysiology was weak.

CONCLUSION: ABCB1, diet, and gut microbes mutually interact in colonic inflammation, a well-known risk factor for CRC. Further insight may be translated into preventive and treatment strategies.

Potentially functional SNPs (pfSNPs) as novel genomic predictors of 5-FU response in metastatic colorectal cancer patients

5-Fluorouracil (5-FU) and its pro-drug Capecitabine have been widely used in treating colorectal cancer. However, not all patients will respond to the drug, hence there is a need to develop reliable early predictive biomarkers for 5-FU response. Here, we report a novel potentially functional Single Nucleotide Polymorphism (pfSNP) approach to identify SNPs that may serve as predictive biomarkers of response to 5-FU in Chinese metastatic colorectal cancer (CRC) patients. 1547 pfSNPs and one variable number tandem repeat (VNTR) in 139 genes in 5-FU drug (both PK and PD pathway) and colorectal cancer disease pathways were examined in 2 groups of CRC patients. Shrinkage of liver metastasis measured by RECIST criteria was used as the clinical end point. Four non-responder-specific pfSNPs were found to account for 37.5% of all non-responders (P<0.0003). Five additional pfSNPs were identified from a multivariate model (AUC under ROC = 0.875) that was applied for all other pfSNPs, excluding the non-responder-specific pfSNPs. These pfSNPs, which can differentiate the other non-responders from responders, mainly reside in tumor suppressor genes or genes implicated in colorectal cancer risk. Hence, a total of 9 novel SNPs with potential functional significance may be able to distinguish non-responders from responders to 5-FU. These pfSNPs may be useful biomarkers for predicting response to 5-FU.

Colorectal cancer susceptibility: apparent gender-related modulation by ABCB1 gene polymorphisms

BACKGROUND

The ATP-binding cassette transporter B1 (ABCB1) gene codes for a membrane efflux pump localized in epithelial cells. Together with other Permeability-glycoproteins in the small and large intestine, its product represents a barrier against xenobiotics, bacterial toxins, drugs and other substances introduced with diet, including carcinogens. The aim of this investigation was to verify the possible contribution of ABCB1 single nucleotide polymorphisms (SNPs) to the genetic risk of colorectal cancer (CRC).

RESULTS

DNA obtained from the peripheral blood of 98 CRC patients and 100 healthy controls was genotyped for the three selected SNPs: 1236C > T (rs1128503), 2677G > T/A (rs2032582), and 3435C > T (rs1045642). Molecular data were analyzed to asses allele and haplotype association with CRC. No evidence of an association between ABCB1 alleles and CRC occurrence as a whole was found. However, ABCB1 showed either association with carcinoma of the sigmoid colon, and appeared able to influence the sex ratio among CRC patients. These two effects seemed to act independently based on multivariate analysis. We showed that ABCB1 polymorphisms were able to influence CRC susceptibility related to tumor localization and patient gender.

CONCLUSIONS

We suggest that sensitivity to undetermined risk factors could depend on the genetic background of ABCB1 locus, with a mechanism that also depends on patient gender.

Pharmacogenetics research on chemotherapy resistance in colorectal cancer over the last 20 years

During the past two decades the first sequencing of the human genome was performed showing its high degree of inter-individual differentiation, as a result of large international research projects (Human Genome Project, the 1000 Genomes Project International HapMap Project, and Programs for Genomic Applications NHLBI-PGA). This period was also a time of intensive development of molecular biology techniques and enormous knowledge growth in the biology of cancer. For clinical use in the treatment of patients with colorectal cancer (CRC), in addition to fluoropyrimidines, another two new cytostatic drugs were allowed: irinotecan and oxaliplatin. Intensive research into new treatment regimens and a new generation of drugs used in targeted therapy has also been conducted. The last 20 years was a time of numerous in vitro and in vivo studies on the molecular basis of drug resistance. One of the most important factors limiting the effectiveness of chemotherapy is the primary and secondary resistance of cancer cells. Understanding the genetic factors and mechanisms that contribute to the lack of or low sensitivity of tumour tissue to cytostatics is a key element in the currently developing trend of personalized medicine. Scientists hope to increase the percentage of positive treatment response in CRC patients due to practical applications of pharmacogenetics/pharmacogenomics. Over the past 20 years the clinical usability of different predictive markers has been tested among which only a few have been confirmed to have high application potential. This review is a synthetic presentation of drug resistance in the context of CRC patient chemotherapy. The multifactorial nature and volume of the issues involved do not allow the author to present a comprehensive study on this subject in one review.

Reversing multidrug resistance in Caco-2 by silencing MDR1, MRP1, MRP2, and BCL-2/BCL-xL using liposomal antisense oligonucleotides

Multidrug resistance (MDR) is a major impediment to chemotherapy. In the present study, we designed antisense oligonucleotides (ASOs) against MDR1, MDR-associated protein (MRP)1, MRP2, and/or BCL-2/BCL-xL to reverse MDR transporters and induce apoptosis, respectively. The cationic liposomes (100 nm) composed of N-[1-(2,3-dioleyloxy)propyl]-n,n,n-trimethylammonium chloride and dioleoyl phosphotidylethanolamine core surrounded by a polyethylene glycol (PEG) shell were prepared to carry ASOs and/or epirubicin, an antineoplastic agent. We aimed to simultaneously suppress efflux pumps, provoke apoptosis, and enhance the chemosensitivity of human colon adenocarcinoma Caco-2 cells to epirubicin. We evaluated encapsulation efficiency, particle size, cytotoxicity, intracellular accumulation, mRNA levels, cell cycle distribution, and caspase activity of these formulations. We found that PEGylated liposomal ASOs significantly reduced Caco-2 cell viability and thus intensified epirubicin-mediated apoptosis. These formulations also decreased the MDR1 promoter activity levels and enhanced the intracellular retention of epirubicin in Caco-2 cells. Epirubicin and ASOs in PEGylated liposomes remarkably decreased mRNA expression levels of human MDR1, MRP1, MRP2, and BCL-2. The combined treatments all significantly increased the mRNA expressions of p53 and BAX, and activity levels of caspase-3, -8, and -9. The formulation of epirubicin and ASOs targeting both pump resistance of MDR1, MRP1, and MRP2 and nonpump resistance of BCL-2/BCL-xL demonstrated more superior effect to all the other formulations used in this study. Our results provide a novel insight into the mechanisms by which PEGylated liposomal ASOs against both resistance types act as activators to epirubicin-induced apoptosis through suppressing MDR1, MRP1, and MRP2, as well as triggering intrinsic mitochondrial and extrinsic death receptor pathways. The complicated regulation of MDR highlights the necessity for a multifunctional approach using an effective delivery system, such as PEGylated liposomes, to carry epirubicin and ASOs as a potent nanomedicine for improving the clinical efficacy of chemotherapy.

Pharmacogenetics of ABC and SLC transporters in metastatic colorectal cancer patients receiving first-line FOLFIRI treatment

OBJECTIVE

Membrane transporters are widely recognized as important determinants of drug disposition and response, generating increasing interest on the pharmacological implications of their genetic variations. The aim of this study was to elucidate the predictive/prognostic role of ATP-binding cassette (ABC) and solute carrier (SLC) protein polymorphisms on irinotecan (FOLFIRI regimen) outcome.

PATIENTS AND METHODS

A total of 250 White metastatic colorectal cancer patients homogenously treated with a first-line FOLFIRI regimen were genotyped for a panel of variants in five transporter genes. The primary study endpoints were the response rate (partial or complete response), overall survival, and time to progression. Toxicity was considered a secondary endpoint. Irinotecan pharmacokinetic data of 71 patients were used for polymorphism functional analysis.

RESULTS

Two variants of the ABCG2 (-15622C>T, rs7699188) gene were found to be predictive (P < 0.01) of the response rate. High-order relationships of ABC/SLC markers with previously investigated genetic (UGT1A1 polymorphisms) and nongenetic (primary tumor site) factors that helped determine the response rate were highlighted. A prognostic effect of the ABCB1 rs2032582 variant on patient overall survival emerged (P = 0.0074). The ABCG2 rs7699788 variant was also seen to be associated with grade 3-4 nonhematological toxicity (P = 0.0012). The ABCG2 (-15622C>T, rs7699188) and ABCB1 (rs2032582) polymorphisms were not found to be associated with pharmacokinetic parameters.

CONCLUSION

This study showed that ABC/SLC polymorphisms have a crucial contribution toward the FOLFIRI outcome. This could represent a further step toward personalized therapy.

Low ABCB1 gene expression is an early event in colorectal carcinogenesis

The ABCB1/MDR1 gene product ABCB1/P-glycoprotein is implicated in the development of colorectal cancer (CRC). NFKB1 encodes transcription factors regulating expression of a number of genes including ABCB1. We have previously found association between the ABCB1 C-rs3789243-T polymorphism and CRC risk and interactions between the ABCB1 C-rs3789243-T and C3435T polymorphisms and meat intake in relation to CRC risk (Andersen, BMC Cancer, 2009, 9, 407). ABCB1 and NFKB1 mRNA levels were assessed in intestinal tissue from 122 CRC cases, 101 adenoma cases (12 with severe dysplasia, 89 with mild-moderate dysplasia) and from 18 healthy individuals, together with gene polymorphisms in ABCB1 and NFKB1. ABCB1 mRNA levels were highest in the healthy individuals and significantly lower in mild/moderate and severe dysplasia tissue (P<0.05 for both), morphologically normal tissues close to the tumour (P<0.05), morphologically normal tissue at a distance from the tumour (P<0.05) and CRC tissue (P<0.001). Furthermore, ABCB1 mRNA levels were lower in adenomas and carcinomas compared to morphologically normal tissue from the same individuals (P<0.01). The ABCB1 C-rs3789243-T and NFKB1 -94ins/del homozygous variant genotypes were associated with low ABCB1 mRNA levels in morphologically normal sigmoid tissue from adenoma cases (P<0.05 for both). NFKB1 mRNA levels were lower in both tumour and normal tissue from cancer patients (P<0.001) as compared to healthy individuals but we were unable to show association between NFKB1 -94ins/del genotype and NFKB1 mRNA levels. This study suggests that low ABCB1 mRNA levels are an early event in CRC development and that the two polymorphisms affect ABCB1 mRNA levels whereas low NFKB1 mRNA levels occur later in carcinogenesis. Low ABCB1 protein levels may promote colorectal carcinogenesis through increasing intracellular exposure to carcinogenic ABCB1 substrates.