Characterization and analyses of multidrug resistance-associated protein 1 (MRP1/ABCC1) polymorphisms in Chinese population

Structural and functional implications of ABCC1 variants on clinical statin response

ATP-binding cassette (ABC) proteins are membrane transporters responsible for metabolites and active substances removal from cells. Their genes' variations have been associated with protein function and expression defects. Familial Hypercholesterolemia (FH) patients hosting those alterations might compromise the efficacy of high-dose statin treatment, a primary therapeutic strategy. ABCC1 is a member of the ABC-transporter superfamily, potentially relevant to pharmacological therapy responses and toxicity risks in hypercholesterolemic patients. Here, we evaluated specific non-synonymous (SNV) missense variants in the ABCC1 gene from a FH patient cohort, assessing potential impacts on protein structure, molecular dynamics and interactions with rosuvastatin, atorvastatin, pravastatin, pitavastatin, and lovastatin. Molecular docking, complemented by motion, visual and binding affinity analysis using the PLANNET model, suggested that these mutations had minimal impact on drug interactions. These findings prompted further analysis of two other efflux pumps, ABCG2 and P-gp, and their statin interactions. Interestingly, diminished binding affinities hinted at a compensatory mechanism wherein other transporters might mitigate potential ABCC1 mutation effects, ensuring effective drug efflux. Clinical profiles from the patient cohort did not show a correlation between these variants and clinical outcomes, potentially pointing to the role of alternate drug transporters in statin interaction.

Impact of Genetic Polymorphisms on Treatment Outcomes of Proteasome Inhibitors and Immunomodulatory Drugs in Multiple Myeloma

OPINION STATEMENT

Multiple myeloma (MM) is classified as a lymphoproliferative disorder that remains an incurable malignancy despite improved patient survival with new drug therapies. Polymorphisms are essential in determining the effectiveness and outcome of treatments in MM. Despite significant advances, there needs to be more understanding of the underlying biological mechanisms that determine treatment outcomes. studies show that investigating gene polymorphisms involved in drug metabolism, DNA repair, inflammation, and apoptosis pathways can predict the effectiveness of treatment in MM patients. Therefore, these findings emphasize the potential of genetic profiling for predicting treatment outcomes and tailoring treatments to individual genetic profiles, which increases the efficiency and reduces the toxicity of MM treatments.

Ningalins, Pyrrole-Bearing Metabolites Isolated from Didemnum spp. Synthesis and MDR-Reversion Activity in Cancer Therapy

Multi-Drug Resistance (MDR) is one of the most frequent problems observed in the course of cancer chemotherapy. Cells under treatment, tend to develop survival mechanisms to drug-action thus generating drug-resistance. One of the most important mechanism to get it is the over expression of P-gp glycoprotein, which acts as an efflux-pump releasing the drug outside of the cancer cell. A strategy for a succesfull treatment consists in the co-administration of one compound that acts against P-gp and another which acts against the cell during chemotherapy. Ningalins are pyrrole-containing naturally occurring compounds isolated mainly from the marine tunicate Didemnum spp and also they are some of the top reversing agents in MDR treatment acting on P-gp. Considering the relevance displayed for some of these isolated alkaloids or their core as a drug for co-administration in cancer therapy, all the total synthesis described to date for the members of ningalins family are reviewed herein.

ABCC1, ABCG2 and FOXP3: Predictive Biomarkers of Toxicity from Methotrexate Treatment in Patients Diagnosed with Moderate-to-Severe Psoriasis

BACKGROUND

Methotrexate (MTX) is one of the most extensively used drugs in the treatment of moderate-to-severe psoriasis (PS). However, it frequently must be suspended owing to the toxicity in certain patients.

OBJECTIVE

To evaluate the influence of ABCC1, ABCG2, and FOXP3 in the development of MTX toxicity in PS.

METHODS

Retrospective cohort study with 101 patients. Five single-nucleotide polymorphisms (SNPs) were genotyped using real-time polymerase chain reaction with TaqMan probes.

RESULTS

Patients carrying ABCC1 rs2238476-AG genotype (AG vs. GG: OR = 8.04; 95% CI = 1.48-46.78; p = 0.015); FOXP3 rs376154-GT and GG genotypes (GT vs. TT/GG: OR = 3.86; 95% CI = 1.17-13.92; p = 0.031) and ABCG2 rs13120400-T allele (T vs. CC: OR = 8.33; 95% CI = 1.24-164.79; p = 0.059) showed a higher risk of developing more than one adverse effect. The toxicity analysis by subtypes showed that the ABCC1 rs2238476-AG genotype (AG vs. GG: OR = 8.10; 95% CI = 1.69-46.63; p = 0.011) and FOXP3 rs376154-GT genotype (OR = 4.11; 95% CI = 1.22-15.30; p = 0.027) were associated with the appearance of asthenia. No association of the other ABCC1 polymorphisms (rs35592 and rs246240) with MTX toxicity was found.

CONCLUSION

ABCC1, ABCG2, and FOXP3 polymorphisms can be considered to be risk biomarkers of toxicities in PS patients treated with MTX.

FACS-based genome-wide CRISPR screens define key regulators of DNA damage signaling pathways

DNA damage-activated signaling pathways are critical for coordinating multiple cellular processes, which must be tightly regulated to maintain genome stability. To provide a comprehensive and unbiased perspective of DNA damage response (DDR) signaling pathways, we performed 30 fluorescence-activated cell sorting (FACS)-based genome-wide CRISPR screens in human cell lines with antibodies recognizing distinct endogenous DNA damage signaling proteins to identify critical regulators involved in DDR. We discovered that proteasome-mediated processing is an early and prerequisite event for cells to trigger camptothecin- and etoposide-induced DDR signaling. Furthermore, we identified PRMT1 and PRMT5 as modulators that regulate ATM protein level. Moreover, we discovered that GNB1L is a key regulator of DDR signaling via its role as a co-chaperone specifically regulating PIKK proteins. Collectively, these screens offer a rich resource for further investigation of DDR, which may provide insight into strategies of targeting these DDR pathways to improve therapeutic outcomes.

Genetic variations in ABC transporter genes as a predictive biomarker for toxicity in North Indian lung cancer patients undergoing platinum-based doublet chemotherapy

ATP-binding cassette (ABC) transporters are expressed in various human tissues and play a vital role in the efflux of various chemotherapeutic drugs. The current study has assessed genetic variants of ABCB1, ABCC1, ABCC2, and ABCG2 genes in 407 lung cancer patients undergoing platinum-based doublet chemotherapy. The association of ABCB1 (C1236 T, C3435 T, and G2677 T/A), ABCC1 (G3173 A and G2168 A),ABCC2 (G4544 A), and ABCG2 (C421 A) polymorphisms with chemotherapy-induced adverse events were assessed, and statistical analysis was conducted. Our data showed that patients harboring heterozygous (GA) genotype for ABCC1 G3173 A had an increased risk of developing leukopenia (odds ratio [OR] = 1.88, p = 0.04) and anemia (adjusted odds ratio [AOR] = 2.70, p = 0.03). For ABCC2 G4544 A polymorphism, patients harboring one copy of the mutant (GA) allele showed an increased risk of developing anemia (OR = 4.24, p = 0.03). After adjusting with various confounding factors, the heterozygous (GA) genotype showed a 5.63-fold increased risk of developing anemia (AOR = 5.63, p = 0.03). The ABCB1 G2677 A (OR = 0.37, p = 0.008) and ABCC1 G3173 A (OR = 0.54, p = 0.04) polymorphism showed a lower incidence of developing nephrotoxicity. In ABCG2 C421 A polymorphism, patients harboring heterozygous (CA) genotype had a lower incidence of having diarrhea (OR = 0.25, p = 0.04). An increased risk of having diarrhea was observed in the heterozygous genotype (GA) for ABCC1 G3173 A polymorphism (AOR = 2.78, p = 0.04). An increased risk of liver injury was found in the patients carrying heterozygous genotype of the ABCC1 G3173 A (OR = 2.06, p = 0.02) and ABCB1 C1236 T (OR = 1.85, p = 0.01). This study demonstrates the role of polymorphic variations in ABCB1, ABCC1, ABCC2, and ABCG2 in predicting hematological, nephrotoxicity, gastrointestinal, and hepatotoxicity.

Impact of ABCB1, ABCC1, ABCC2, and ABCG2 variants in predicting prognosis and clinical outcomes of north Indian lung cancer patients undergoing platinum-based doublet chemotherapy

BACKGROUND

ABC transporters are membrane proteins expressed in the lungs and are crucial for efflux of various chemotherapeutic agents. Polymorphisms of ABC transporters have a certain impact on the transporter activity because their expression levels may influence the extent and longevity of chemotherapeutic drug outflow, affecting patient outcomes. The present study aimed to assess the impact of ABCB1, ABCC1/2, and ABCG2 gene variants in predicting prognosis and clinical outcomes in lung carcinoma patients.

METHODS

In total, 502 lung cancer patients undergoing platinum-based chemotherapy were recruited in this prospective study. Genotyping of ABCB1 (C1236 T, C3435 T, and G2677 T/A), ABCC1 (G3173 A and G2168 A), ABCC2 (G4544 A), and ABCG2 (C421 A) polymorphisms in Northern Indian lung carcinoma patients were evaluated using polymerase chain reaction-restriction fragment length polymorphism analysis.

RESULTS

Poor survival outcomes were noted in patients carrying a heterozygous genotype (CT) for the ABCB1 C1236 T polymorphism compared to the wild-type genotype (CC) (p = 0.04). The mutant genotype (AA) for ABCC1 G3173 A exhibited a lower median survival time compared to the reference genotype (GG) (p = 0.009). Lower survival was observed in individuals carrying a heterozygous genotype (GA) for ABCC2 G4544 A polymorphism compared to the wild-type genotype (GG) (p = 0.017). Small cell lung cancer patients with the ABCB1 G2677 A polymorphism having a heterozygous genotype (GA) showed poor survival compared to the wild-type genotype (GG) (p = 0.03). For ABCC1 G3173 A, adenocarcinoma patients having a mutant genotype (AA) had reduced survival compared to the wild-type (GG) genotype (p = 0.03). For ABCB1 C3435 T, individuals carrying a heterozygous (CT) (p = 0.018) and mutant (TT) genotype (p = 0.007) had poor survival compared to the wild-type (CC) genotype in patients treated with pemetrexed and cisplatin. The patients administered cisplatin and irinotecan and having mutant alleles (AA) for the ABCB1 G2677 A polymorphism showed a lower survival compared to the individuals carrying wild-type alleles (GG) (p = 0.009).

CONCLUSIONS

Our findings suggest that ABCB1 C1236 T, ABCB1 C3435 T, ABCB1 G2677 A, ABCC1 G3173 A, and ABCC2 G4544 A are involved in predicting prognosis. Genotyping of the ABC polymorphism is essential for predicting prognosis in lung carcinoma patients.

2-Hydroxyestradiol Overcomes Mesenchymal Stem Cells-Mediated Platinum Chemoresistance in Ovarian Cancer Cells in an ERK-Independent Fashion

Ovarian cancer (OC) is the second most common type of gynecological malignancy. Platinum (Pt)-based chemotherapy is the standard of care for OC, but toxicity and acquired chemoresistance has proven challenging. Recently, we reported that sensitivity to platinum was significantly reduced in a co-culture of OC cells with MSC. To discover compounds capable of restoring platinum sensitivity, we screened a number of candidates and monitored ability to induce PARP cleavage. Moreover, we monitored platinum uptake and expression of ABC transporters in OC cells. Our results showed that 2-hydroxyestradiol (2HE2), a metabolite of estradiol, and dasatinib, an Abl/Src kinase inhibitor, were significantly effective in overcoming MSC-mediated platinum drug resistance. Dasatinib activity was dependent on ERK1/2 activation, whereas 2HE2 was independent of the activation of ERK1/2. MSC-mediated platinum drug resistance was accompanied by reduced intracellular platinum concentrations in OC cells. Moreover, MSC co-cultured with OC cells resulted in downregulation of the expression of cellular transporters required for platinum uptake and efflux. Exposure to 2HE2 and other modulators resulted in an increase in intracellular platinum concentrations. Thus, 2HE2 and dasatinib might act as sensitizers to restore platinum drug sensitivity to OC cells and thus to limit TME-mediated chemoresistance in OC.

Current Understanding of Membrane Transporters as Regulators or Targets for Cisplatin-Induced Hearing Loss

Cisplatin is a platinum-based drug, which remains among the most efficacious anticancer treatment options. Unfortunately, use of cisplatin is hindered by dose-limiting toxicities, including irreversible hearing loss, which can grossly affect patient quality of life. Cisplatin-induced ototoxicity is the result of cochlear hair cell damage through a mechanism that is poorly understood. However, cisplatin cytotoxicity is reliant on intracellular accumulation, a process that is largely dependent on the presence of particular membrane transporters. This review will provide an update on our current understanding of the various transporters known to be involved in the disposition and cytotoxicity of platinum drugs or their metabolites, as well as their role in mediating cisplatin-induced hearing loss. We also provide a summary of the successes and opportunities in therapeutically targeting membrane transporters to alleviate platinum-induced hearing loss. Moreover, we describe how this approach could be used to reduce the severity or onset of other adverse events associated with exposure to various forms of platinum drugs, without diminishing antitumor efficacy. SIGNIFICANCE STATEMENT: Cisplatin-induced hearing loss is a dose-limiting and irreversible adverse event with no current preventative or curative treatment measures. Pharmacological targeting of membrane transporters that regulate platinum uptake into cochlear hair cells, if conducted appropriately, may alleviate this devastating side effect and could be applied to alleviate other platinum-induced toxicities.

Drug resistance: from bacteria to cancer

The phenomenon of drug resistance has been a hindrance to therapeutic medicine since the late 1940s. There is a plethora of factors and mechanisms contributing to progression of drug resistance. From prokaryotes to complex cancers, drug resistance is a prevailing issue in clinical medicine. Although there are numerous factors causing and influencing the phenomenon of drug resistance, cellular transporters contribute to a noticeable majority. Efflux transporters form a huge family of proteins and are found in a vast number of species spanning from prokaryotes to complex organisms such as humans. During the last couple of decades, various approaches in analyses of biochemistry and pharmacology of transporters have led us to understand much more about drug resistance. In this review, we have discussed the structure, function, potential causes, and mechanisms of multidrug resistance in bacteria as well as cancers.

ATP-binding cassette (ABC) transporters in cancer: A review of recent updates

The ATP-binding cassette (ABC) transporter superfamily is one of the largest membrane protein families existing in wide spectrum of organisms from prokaryotes to human. ABC transporters are also known as efflux pumps because they mediate the cross-membrane transportation of various endo- and xenobiotic molecules energized by ATP hydrolysis. Therefore, ABC transporters have been considered closely to multidrug resistance (MDR) in cancer, where the efflux of structurally distinct chemotherapeutic drugs causes reduced itherapeutic efficacy. Besides, ABC transporters also play other critical biological roles in cancer such as signal transduction. During the past decades, extensive efforts have been made in understanding the structure-function relationship, transportation profile of ABC transporters, as well as the possibility to overcome MDR via targeting these transporters. In this review, we discuss the most recent knowledge regarding ABC transporters and cancer drug resistance in order to provide insights for the development of more effective therapies.

The effect of eIF3a on anthracycline-based chemotherapy resistance by regulating DSB DNA repair

BACKGROUND

Anthracycline are inhibitors of topoisomerase II leading to DNA double strand breaks, and it is widely used for treatment of breast cancer. eIF3a is the largest subunit of eukaryotic translation initiation factor 3 (eIF3) and highly expressed in breast cancer. In this study, we investigated the role of eIF3a in DSB DNA repair and the response of breast cancer patients to anthracycline-based chemotherapy.

METHODS

MTT assay was used to detect anthracycline sensitivity in cell lines. Real-time reverse transcriptase PCR, western blotting and immunofluorescence were performed to assess changes in gene expression levels. Cometassay and end-joining activity assay were conducted to explore the effect of eIF3a in NHEJ repair. Luciferase reporter assay was performed to detect LIG4 5'UTR activity. Immunohistochemistry was used to detect eIF3a, LIG4 and DNA-PKcs expression levels in breast cancer tissues.

RESULTS

The results showed that eIF3a increased cellular response to anthracyclines by regulating DSB repair activity via influencing the expression of LIG4 and DNA-PKcs at translational level. Breast cancer patients with high level of eIF3a or low level of LIG4 or low level of DNA-PKcs had better anthracycline-based chemotherapy prognosis compared. Moreover, Combined expressions of eIF3a, LIG4 and DNA-PKcs could be better to predict PFS in breast cancer patients with anthracycline-based chemotherapy.

CONCLUSION

Our findings suggest that eIF3a effects anthracycline-based chemotherapy response by regulating DSB DNA repair.

KRAS and EGFR Mutations Differentially Alter ABC Drug Transporter Expression in Cisplatin-Resistant Non-Small Cell Lung Cancer

Lung carcinoma is still the most common malignancy worldwide. One of the major subtypes of non-small cell lung cancer (NSCLC) is adenocarcinoma (AC). As driver mutations and hence therapies differ in AC subtypes, we theorized that the expression and function of ABC drug transporters important in multidrug resistance (MDR) would correlate with characteristic driver mutations KRAS or EGFR. Cisplatin resistance (CR) was generated in A549 (KRAS) and PC9 (EGFR) cell lines and gene expression was tested. In three-dimensional (3D) multicellular aggregate cultures, both ABCB1 and ABCG2 transporters, as well as the WNT microenvironment, were investigated. ABCB1 and ABCG2 gene expression levels were different in primary AC samples and correlated with specific driver mutations. The drug transporter expression pattern of parental A549 and PC9, as well as A549-CR and PC9-CR, cell lines differed. Increased mRNA levels of ABCB1 and ABCG2 were detected in A549-CR cells, compared to parental A549, while the trend observed in the case of PC9 cells was different. Dominant alterations were observed in LEF1, RHOU and DACT1 genes of the WNT signalling pathway in a mutation-dependent manner. The study confirmed that, in lung AC-s, KRAS and EGFR driver mutations differentially affect both drug transporter expression and the cisplatin-induced WNT signalling microenvironment.

Current Insights into Interethnic Variability in Testicular Cancers: Population Pharmacogenetics, Clinical Trials, Genetic Basis of Chemotherapy- Induced Toxicities and Molecular Signal Transduction

Testicular cancer is an aggressive malignancy with a rising incidence rate across the globe. Testicular germ cell tumors are the most commonly diagnosed cancers, and surgical removal of the testes is often a radical necessity along with chemotherapy and radiotherapy. While seminomas are receptive to radiotherapy as well as chemotherapy, non-seminomatous germ cell tumors respond to chemotherapy only. Due to the singular nature of testicular cancers with associated orchiectomy and mortality, it is important to study the molecular basis and genetic underpinnings of this group of cancers across male populations globally. In this review, we shed light on the population pharmacogenetics of testicular cancer, pediatric and adult tumors, current clinical trials, genetic determinants of chemotherapy-induced toxicity in testicular cancer, as well as the molecular signal transduction pathways operating in this malignancy. Taken together, our discussions will help in enhancing our understanding of genetic factors in testicular carcinogenesis and chemotherapy-induced toxicity, augment our knowledge of this aggressive cancer at the cellular and molecular level, as well as improve precision medicine approaches to combat this disease.

Association between ABCB1 Polymorphisms and Artesunate-Mefloquine Treatment Responses of Patients with Falciparum Malaria on the Thailand-Myanmar Border

A decrease in the clinical efficacy of a 3-day artesunate-mefloquine combination treatment was reported in the areas of multidrug-resistant Plasmodium falciparum along the Thailand-Myanmar border. The current study investigated the possible contribution of genetic polymorphisms of the three major genes encoding drug efflux transporters, ABCB1, ABCG2, and ABCC1, to responses to the aforementioned treatment in 91 patients with acute uncomplicated falciparum malaria residing along the Thailand-Myanmar border. Patients carrying homozygous mutant genotype ABCB1 c.1236C>T (TT) were found to have a three-times higher chance of successful treatment with this combination compared with other genotypes (CC and CT). Furthermore, whole blood mefloquine concentrations in these patients with the TT genotype were significantly lower than those of patients carrying the CC genotype. Patients with heterozygous mutant genotype (CT), however, were three-times more likely to experience treatment failure. No significant association was found with the ABCG2 and ABCC1 gene polymorphisms. The results suggest that ABCB1 c.1236CT polymorphisms could be useful genetic markers for predicting responses to the 3-day artesunate-mefloquine treatment; however, studies using larger sample sizes in different malaria-endemic areas are necessary to confirm this finding. This study highlights the impact of pharmacogenetic factors on antimalarial treatment responses and the basis for the application of control policies in various malaria-endemic areas.

Overexpression of ABCC1 Confers Drug Resistance to Betulin

Betulin is a lupane-type pentacyclic triterpene, which is isolated from birch bark. It has a broad spectrum of biological and pharmacological properties, such as anti-inflammatory, anti-tumor, anti-viral, and anti-bacterial activity. Herein, we explored the factors that may result in betulin resistance, especially with respect to its interaction with ATP-binding cassette subfamily C member 1 (ABCC1). ABCC1 is an important member of the ATP-binding cassette (ABC) transporter family, which is central to mediating multidrug resistance (MDR) in naturally derived anticancer agents. An MTT-based cell viability assay showed that ABCC1 overexpression has the ability to desensitize both cancer cell line and gene-transfected cell line to betulin and that this betulin-induced resistance can be antagonized by a known ABCC1 inhibitor MK571 at 25 μM. Additionally, betulin upregulates the ABCC1 protein expression level in both concentration-dependent and time-dependent manners, also blocks the transport function mediated by ABCC1. Subsequently, a high affinity score of betulin was achieved in a computational docking analysis, demonstrating a strong interaction of betulin with ABCC1.

New Evidence for P-gp-Mediated Export of Amyloid-β PEPTIDES in Molecular, Blood-Brain Barrier and Neuronal Models

Defective clearance mechanisms lead to the accumulation of amyloid-beta (Aβ) peptides in the Alzheimer’s brain. Though predominantly generated in neurons, little is known about how these hydrophobic, aggregation-prone, and tightly membrane-associated peptides exit into the extracellular space where they deposit and propagate neurotoxicity. The ability for P-glycoprotein (P-gp), an ATP-binding cassette (ABC) transporter, to export Aβ across the blood-brain barrier (BBB) has previously been reported. However, controversies surrounding the P-gp–Aβ interaction persist. Here, molecular data affirm that both Aβ₄₀ and Aβ₄₂ peptide isoforms directly interact with and are substrates of P-gp. This was reinforced ex vivo by the inhibition of Aβ₄₂ transport in brain capillaries from P-gp-knockout mice. Moreover, we explored whether P-gp could exert the same role in neurons. Comparison between non-neuronal CHO-APP and human neuroblastoma SK-N-SH cells revealed that P-gp is expressed and active in both cell types. Inhibiting P-gp activity using verapamil and nicardipine impaired Aβ₄₀ and Aβ₄₂ secretion from both cell types, as determined by ELISA. Collectively, these findings implicate P-gp in Aβ export from neurons, as well as across the BBB endothelium, and suggest that restoring or enhancing P-gp function could be a viable therapeutic approach for removing excess Aβ out of the brain in Alzheimer’s disease.

MDR1 Gene Polymorphisms and Its Association With Expression as a Clinical Relevance in Terms of Response to Chemotherapy and Prognosis in Ovarian Cancer

In spite of the significant advancements in the treatment modalities, 30% of advanced stage ovarian cancer (OC) patients do not respond to the standard chemotherapeutic regimen and most of the responders finally relapse over time due to the escalation of multidrug resistance (MDR) Phenomenon. Our present study evaluated chemotherapeutic sensitivity response among 47 ovarian tumor patients of which we found 37 (78.8%) sensitive and remaining 10 (21.2%) resistant. Among the resistant, seven tumor samples were found to be platinum resistant or refractory to platinum (CB/TX), one to carboplatin, and two to 5FU. Notably, all these resistant cases were observed in the disease recurrence group of patients identified at stage III or IV. The stage III resistant cases revealed heterozygous mutation (C/T) in exon 12 (C1236T) and 26 (C3435T) and increased level of mRNA, whereas homozygous mutation (T/T) was found at stage IV tumor patients. The genotypic difference was found to be significant (p = 0.03) for exon 12, and p = 0.003 for exon 26 mutant genotypes. No significant association between genotypes of different exons with tumor stages and tumor grade was observed (p > 0.05). However, a significant association was observed between the genotype of exon-12 and histopathology of tumor tissue (p = 0.028). Statistically, the chemotherapy response was found to be significantly associated with the tumor stage (p = 0.019). We also observed a significant difference in PFS (P = 0.019) and OS (P = 0.047) between tumor grades 1 and 3. Notably, the highest mRNA expression was observed in resistant tumor sample T-32, where interestingly we found homozygosity TT in all of the exons 12, 21, and 26. Thus, we suggest that exons 12 (C1236T) and exon 26 (C3435T) polymorphism may play a role in inducing drug resistance by altering the expression level of the MDR1 gene. To summarize, we suggest that the expression of MDR1 in OC is influenced by tumor stage and genotype variants as well as by chemotherapeutic drugs. Thus our findings suggest that inter individual variability in platinum based therapy may be anticipated by MDR1 genotypes. Further studies on a large number of samples shall eventually lead to provide beneficial information for the individualized chemotherapy.

Novel association between heterozygous genotype of single nucleotide polymorphism C218T in drug transporter ABCC1 gene and increased risk of colon cancer

Objectives:

To determine the role of G128C and C218T variants in ABCC1 gene with the risk of developing colon cancer in Jeddah, Kingdom of Saudi Arabia.

Methods:

This case-control study was conducted on 51 colon cancer patients and 65 controls from King Abdulaziz University Hospital and King Abdullah Medical City in the period from January 2015 to April 2017, and was approved by the Unit of Biomedical Ethics (no: 261-15). Experiments were performed in the experimental biochemistry unit at King Fahd Medical Research Center. The genotype distributions and allele frequencies were determined by polymerase chain reaction-restriction fragments length polymorphism (PCR-RFLP) and DNA sequencing. A Chi-square test was used to determine allele and genotype distributions, odds ratio (OR), risk ratio (RR) and 95% confidence intervals (CI). P-values of <0.05 were considered statistically significant.

Results:

The results showed a novel association between heterozygous (CT) genotype for variant C218T and increased risk of colon cancer [OR=3.4, 95% CI (1.56-7.48), and RR=1.92, 95% CI (1.26-2.93), p=0.002]. These ratios were correlated with high-grade stages (III and IV). In contrast, for variant G128C, there was no significant association with the risk of developing colon cancer.

Conclusion:

The novel findings of the study revealed that the CT genotype of variant C218T in ABCC1 gene may increase the risk of developing colon cancer.

Association between MDR1 gene polymorphism and clinical course of pediatric pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease with a complex pathogenesis. The polymorphism of the gene of multidrug resistance-1 (MDR1) has been associated with many diseases including PAH.

Objective. In this study we aimed to investigate the relevance of the MDR1 polymorphism to pediatric PAH clinical course.

Methods. A total of 40 pediatric patients with PAH (secondary to congenital heart defects or idiopathic) and 40 control subjects were enrolled. Patients with PAH were divided into 2 groups, according to their evolution: 28 patients who remained clinically stable at 12-months (non-worsening group) and 12 patients who presented clinical worsening at 12-months (worsening group). Genomic DNA was genotyped for MDR1 gene polymorphisms as follows: C1236T, G2677T and C3435T.

Results. There were no significant differences between PAH children groups (clinical worsening and non-worsening) nor between PAH children and controls in terms of frequency distribution of the three studied genotypes or alleles.

Conclusions. The MDR1 polymorphism could not be correlated with the clinical evolution of pediatric PAH patients in our study.

Acridone-pyrimidine hybrids- design, synthesis, cytotoxicity studies in resistant and sensitive cancer cells and molecular docking studies

Hybrid systems of acridones with substituted pyrimidines were designed with an objective of discovering next generation anticancer agents targeting multiple mechanisms in the cancer cell. Hybrid compounds were synthesized by simple and convenient methods in the lab, characterized by NMR and Mass spectral methods and screened for cytotoxicity against A549 (lung), Hela (cervical), MCF7 (breast) and MDA-MB-231 (breast) cancer cell lines respectively. Evaluation of compounds for cell proliferation identified active compounds 11b, 11d and 11h against MCF7, MDA-MB-231 and A549 cell lines. Further absorption titrations with CT-DNA and gel electrophoresis identified that hybrid molecules displayed anticancer activity partly by DNA intercalation. Also further results of western blotting assay with Akt kinase identified that hybrid compounds have the ability to inhibit the Akt kinase activity and induce apoptosis, with ABCC1 suggests that active compounds too have the ability to modulate multidrug resistance (MDR) associated with ABCC1/MRP1. Selective Akt1 kinase assay have identified 11a, 11b, 11d and 11h as potential inhibitors. Molecular docking studies identified the orientation and binding interactions at the active site of Akt1 and DNA. Compounds 12e and 12f have shown good cytotoxicity profile against lung cancer cell lines of sensitive and resistant type. Acute toxicity study of compound 12f at the dose of 5000 mg/kg has identified no signs of clinical toxicity. Prediction of ADMET properties and oral toxicity of the drug likeness features of new hybrid systems were carried out using software's. This experimental data suggests that hybrid systems of acridone with substituted pyrimidines can be taken as a lead for the design of efficient inhibitors and active compounds which can be taken up for further studies.

Gene-gene and gene-environment interactions influence platinum-based chemotherapy response and toxicity in non-small cell lung cancer patients

Platinum-based chemotherapy is a major therapeutic regimen of lung cancer. Various single nucleotide polymorphisms (SNPs) reported were associated with platinum-based chemotherapy response and drug toxicity. However, neither of the studies explored this association from SNP-SNP interaction perspective nor taking into effects of SNP-environment consideration simultaneously. We genotyped 504 polymorphisms and explore the association of gene-gene and gene-environment interactions with platinum-based chemotherapy response and toxicity in 490 NSCLC patients. 16 SNPs were found significantly associated with platinum-based chemotherapy, and they were picked out as study object in the validation cohort. We recruited 788 patients in the validation cohort. We found that HSPD1 rs17730989-SUMF1 rs2633851 interaction was associated with platinum-based chemotherapy-induced hematologic toxicity (adjusted OR = 0.233, P = 0.018). In addition, the combined effect of ABCG2 rs2231142-CES5A rs3859104 was significantly associated with overall toxicity (adjusted OR = 8.044, P = 4.350 × 10-5). Besides, the model of ARHGAP26 rs3776332-ERCC6 rs2228528-SLC2A1 rs4658-histology was associated with platinum-based chemotherapeutic response. Gene-gene and gene-environment interactions have been identified to contribute to chemotherapy sensitivity and toxicity. They can potentially predict drug response and toxicity of platinum-based chemotherapy in NSCLC patients.

ABCB1 and ABCG2 drug transporters are differentially expressed in non-small cell lung cancers (NSCLC) and expression is modified by cisplatin treatment via altered Wnt signaling

BACKGROUND

Lung cancer (LC) is still the most common cause of cancer related deaths worldwide. Non-small cell lung cancer (NSCLC) accounts for 85% of all LC cases but is not a single entity. It is now accepted that, apart from the characteristic driver mutations, the unique molecular signatures of adeno- (AC) and squamous cell carcinomas (SCC), the two most common NSCLC subtypes should be taken into consideration for their management. Therapeutic interventions, however, frequently lead to chemotherapy resistance highlighting the need for in-depth analysis of regulatory mechanisms of multidrug resistance to increase therapeutic efficiency.

METHODS

Non-canonical Wnt5a and canonical Wnt7b and ABC transporter expressions were tested in primary human LC (n = 90) resections of AC and SCC. To investigate drug transporter activity, a three dimensional (3D) human lung aggregate tissue model was set up using differentiated primary human lung cell types. Following modification of the canonical, beta-catenin dependent Wnt pathway or treatment with cisplatin, drug transporter analysis was performed at mRNA, protein and functional level using qRT-PCR, immunohistochemistry, immune-fluorescent staining and transport function analysis.

RESULTS

Non-canonical Wnt5a is significantly up-regulated in SCC samples making the microenvironment different from AC, where the beta-catenin dependent Wnt7b is more prominent. In primary cancer tissues ABCB1 and ABCG2 expression levels were different in the two NSCLC subtypes. Non-canonical rhWnt5a induced down-regulation of both ABCB1 and ABCG2 transporters in the primary human lung aggregate tissue model recreating the SCC-like transporter pattern. Inhibition of the beta-catenin or canonical Wnt pathway resulted in similar down-regulation of both ABC transporter expression and function. In contrast, cisplatin, the frequently used adjuvant chemotherapeutic agent, activated beta-catenin dependent signaling that lead to up-regulation of both ABCB1 and ABCG2 transporter expression and activity.

CONCLUSIONS

The difference in the Wnt microenvironment in AC and SCC leads to variations in ABC transporter expression. Cisplatin via induction of canonical Wnt signaling up-regulates ABCB1 and ABCG2 drug transporters that are not transporters for cisplatin itself but are transporters for drugs that are frequently used in combination therapy with cisplatin modulating drug response.

Pharmacogenomics of platinum-based chemotherapy sensitivity in NSCLC: toward precision medicine

Lung cancer is one of the leading causes of cancer-related death in the world. Platinum-based chemotherapy is the first-line treatment for non-small-cell lung cancer (NSCLC), however, the therapeutic efficiency varies remarkably among individuals. A large number of pharmacogenomics studies aimed to identify genetic variations which can be used to predict platinum response. Those studies are leading NSCLC treatment to the new era of precision medicine. In the current review, we provided a comprehensive update on the main recent findings of genetic variations which can be used to predict platinum sensitivity in the NSCLC patients.

eIF3a improve cisplatin sensitivity in ovarian cancer by regulating XPC and p27Kip1 translation

The eukaryotic translation initiation factor 3a (eIF3a) is one of the core subunits of the translation initiation complex eIF3, responsible for ribosomal subunit joining and mRNA recruitment to the ribosome. Our previous study identified that it was correlated with platinum response in lung cancer. The current study aims to test the hypothesis that eIF3a may affect the drug response and prognosis of ovarian cancer patients receiving platinum-based chemotherapy by regulating xeroderma pigmentosum complementation group C (XPC) and p27^Kip1. Immunohistochemistry and western blot was used to determine the expression of eIF3a in 126 human ovarian cancer tissues followed by association analysis of eIF3a expression with patient's response and survival. Ectopic over-expression and RNA interference knockdown of eIF3a were carried out in A2780/cisplatin (DDP) and its parental A2780 cells, respectively, to determine the effect of altered eIF3a expression on cellular response to cisplatin by employing MTT assay. Western Blot analyses were also carried out to determine the regulation of eIF3a on XPC and p27^Kip1. eIF3a expression was associated with response of ovarian cancer patients to DDP-based chemotherapy and their survival. Overexpression and knockdown of eIF3a increased and decreased the cellular response to cisplatin in A2780/DDP and A2780 cells, respectively. In addition, XPC and p27^Kip1 were down regulated by eIF3a. eIF3a improves ovarian cancer patients' response to DDP-based chemotherapy via down regulating XPC and p27^Kip1.

Association of ABCB1 (C3435T) and ABCC1 (G2012T) Polymorphisms with Clinical Response to Atorvastatin in Iranian Patients with Primary Hyperlipidemia

BACKGROUND

Atorvastatin is prescribed for the primary and the secondary prevention of coronary artery diseases. A wide variation in inter-individual statin response suggests that genetic differences may contribute to this variation. This study investigated the association of ABCB1 (C3435T) and ABCC1 (G2012T) polymorphisms with clinical response to atorvastatin in Iranian primary hyperlipidemic patients.

METHODS

Individuals (n=179) with primary hypercholesterolemia were enrolled, and peripheral blood samples were collected. Genotyping of two polymorphisms were performed by amplification refractory mutation system PCR.

RESULTS

Following four weeks of treatment, a significant reduction of LDL-C was observed in variant groups (CT+TT) of ABCB1 (P=0.018) and wild-type group (GG) of ABCC1 genes (P=0.029). Logistic regression analysis revealed a significant difference between male and female responses to 10 mg/day atorvastatin (P=0.004, odds ratio=0.2, CI 95%=0.06-0.6).

CONCLUSION

Our finding indicated that these polymorphisms may be attributed to LDL-C serum levels in the primary hypercholesterolemia patients receiving atorvastatin.

Association of well-characterized lung cancer lncRNA polymorphisms with lung cancer susceptibility and platinum-based chemotherapy response

Long non-coding RNAs (lncRNAs) play important roles in carcinogenesis and drug efficacy. Platinum-based chemotherapy is first-line treatment for lung cancer chemotherapy. In this study, we aimed to investigate the association of well-characterized lung cancer lncRNA genetic polymorphisms with the lung cancer susceptibility and platinum-based chemotherapy response. A total of 498 lung cancer patients and 213 healthy controls were recruited in the study. Among them, 467 patients received at least two cycles of platinum-based chemotherapy. Thirteen polymorphisms in HOXA distal transcript antisense RNA (HOTTIP), HOX transcript antisense intergenic RNA (HOTAIR), H19, CDKN2B antisense RNA 1 (ANRIL), colon cancer-associated transcript 2 (CCAT2), metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), and maternally expressed gene 3 (MEG3) genes were genotyped by allele-specific MALDI-TOF mass spectrometry. We found that patients with HOTTIP rs5883064 C allele or rs1859168 A allele had increased lung cancer risk (P = 0.01, P = 0.01, respectively). CCAT2 rs6983267 (P = 0.02, adenocarcinoma) and H19 rs2107425 (P = 0.02, age under 50 years) showed strong relationship with lung cancer susceptibility. CCAT2 rs6983267, H19 rs2839698, MALAT1 rs619586, and HOTAIR rs7958904 were associated with platinum-based chemotherapy response in dominant model ((P = 0.02, P = 0.04, P = 0.04, P = 0.01, respectively). ANRIL rs10120688 (P = 0.02, adenocarcinoma) and rs1333049 (P = 0.04, small-cell lung cancer), H19 rs2107425 (P = 0.02, small-cell lung cancer) and HOTAIR rs1899663 (P = 0.03, male; P = 0.03, smoker) were associated with response to platinum-based chemotherapy. HOTTIP, CCAT2, H19, HOTAIR, MALATI, ANRIL genetic polymorphisms were significantly associated with lung cancer susceptibility or platinum-based chemotherapy response. They may be potential clinical biomarkers to predict lung cancer risk and platinum-based chemotherapy response.

Genetic variation of the ABC transporter gene ABCC1 (Multidrug resistance protein 1-MRP1) in the Polish population

Background

Multidrug resistance-associated protein 1 (MRP1), encoded by the ABCC1 gene, is an ATP-binding cassette transporter mediating efflux of organic anions and xenobiotics; its overexpression leads to multidrug resistance. In this study, 30 exons (from 31 in total) of the ABCC1 gene as well as and their flanking intron sequences were screened for genetic variation, using the High Resolution Melting (HRM) method, for 190 healthy volunteers representing the Polish population. Polymorphism screening is an indispensable step in personalized patient therapy. An additional targeted SNP verification study for ten variants was performed to verify sensitivity of the scanning method.

Results

During scanning, 46 polymorphisms, including seven novel ones, were found: one in 3’ UTR, 21 in exons (11 of them non-synonymous) and 24 in introns, including one deletion variant. These results revealed some ethnic differences in frequency of several polymorphisms when compared to literature data for other populations. Based on linkage disequilibrium analysis, 4 haplotype blocks were determined for 9 detected polymorphisms and 12 haplotypes were defined. To capture the common haplotypes, haplotype-tagging single nucleotide polymorphisms were identified.

Conclusions

Targeted genotyping results correlated well with scanning results; thus, HRM is a suitable method to study genetic variation in this model. HRM is an efficient and sensitive method for scanning and genotyping polymorphic variants. Ethnic differences were found for frequency of some variants in the Polish population compared to others.

Thus, this study may be useful for pharmacogenetics of drugs affected by MRP1-mediated efflux.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-015-0271-3) contains supplementary material, which is available to authorized users.

Association of Two Polymorphic Codons in P53 and ABCC1 Promoter with Prostate Cancer

BACKGROUND

In prostate cancer, mutated p53 alleles typically contain missense single-base substitution in codon 72 that resides within exons 5-8. Stable p53 proteins in tumor cell nuclei have been associated with malignancy. A role of p53 is the regulation of drug transporters like ABCC1 (MRP1) by an effect on promoter region.

OBJECTIVES

The objective of this study was to identify association of mutations of p53 at codon 72 and 282 and promoter region of ABCC1 with increased risks of prostate cancer.

MATERIALS AND METHODS

Formalin fixed, paraffin-embedded malignant tissues of 45 patients and 45 control samples were evaluated. PCR-RFLP using BstUI for codon 72 and HpaII restriction enzyme for codon 282 p53 gene, and G-1666A promoter region of ABCC1 gene was performed. To assess the frequency of these mutations and to detect new mutations in cancerous samples, PCR-SSCP analysis was performed.

RESULTS

The frequencies of CC, GC and GG genotypes of codon 72 of p53 were 33.33%, 46.67% and 20.00% in patients with cancer and 15.56%, 48.89% and 35.55% in controls, respectively. The relative allele frequencies of ABCC1 promoter polymorphism were 60.00% A and 40.00% G in patients as opposed to 37.78% for A and 62.22% for G in controls. Genotypic frequencies of p53 codon 72 and G1666A of ABCC1 in patients vs. Controls were statistically significant(p<0.05). The study of these samples with PCR-SSCP displayed some new banding patterns.

CONCLUSIONS

The present findings suggest that CC homozygosity in codon 72 of p53 gene and AA genotype in G-1666A of ABCC1 gene may play a role in combination in prostate cancer and increased susceptibility for this malignancy in the Iranian Kurdish population.

Association of HMGB1 and HMGB2 genetic polymorphisms with lung cancer chemotherapy response

The aim of the present study was to investigate the association of genetic polymorphisms in high mobility group box 1 and 2 (HMGB1 and HMGB2, respectively) with platinum-based chemotherapy responses in Chinese lung cancer patients. In total, 338 Chinese lung cancer patients (154 responders and 184 non-responders) were recruited to the study. All patients received at least two cycles of first-line platinum-based chemotherapy. Three tagging single nucleotide polymorphisms (SNPs) of HMGB1 and two tagging SNPs of HMGB2 were detected in patients. We found that rs1412125 and rs2249825 of HMGB1 were significantly associated with the platinum-based chemotherapy response in both recessive and genotypic models. In addition, rs1412125 showed significant association with platinum-based chemotherapy response for the subgroup of patients aged >55 years in additive, recessive and genotypic models. No significant associations were detected between other SNPs and the platinum-based chemotherapy response. The HMGB1 SNPs (rs1412125 and rs2249825) were associated with platinum-based chemotherapy responses in Chinese lung cancer patients. In conclusion, HMGB1 SNPs may serve as potential biomarkers for predicting the efficacy of platinum-based chemotherapy.

Multidrug resistance gene 1 C1236T polymorphism and susceptibility to leukemia: A meta-analysis

Several studies have investigated the association between multidrug resistance gene (MDR1) C1236T polymorphism and leukemia risk, however, these published studies have yielded conflicting results. Thus, the present study carried out a meta-analysis to provide a more precise estimate of the effect of this polymorphism on the susceptibility to leukemia. The published case-control studies regarding the association between MDR1 C1236T polymorphism and leukemia risk were included following a computerized search of PubMed, Elsevier, The Cochrane Library, China National Knowledge Infrastructure and Wanfang Database. Either fixed- or random-effects models were applied to calculate the combined odds ratios (ORs) and 95% confidence intervals (CIs) by RevMan 5.2 software. Seven studies, including 846 cases and 1,523 controls, were included in the present meta-analysis. The results indicated that there was no significant association between the MDR1 C1236T polymorphism and leukemia risk in overall comparisons in all four genetic models (CT vs. CC: OR, 1.31, 95% CI, 0.89-1.91, P=0.17; TT vs. CC: OR, 2.16, 95% CI, 0.99-4.70, P=0.05; TT vs. CC+CT: OR, 1.72, 95% CI, 0.91-3.25, P=0.09; and CT+TT vs. CC: OR, 1.57, 95% CI, 0.96-2.56, P=0.07). In the subgroup analysis according to specific ethnicity, age and the type of leukemia, a significant association was found in adult leukemia (CT+TT vs. CC: OR, 2.77, 95% CI, 1.05-7.31, P=0.04) and chronic myeloid leukemia (CT vs. CC: OR, 1.71, 95% CI, 1.05-2.80, P=0.03). No significant publication bias was detected by funnel plot. Therefore, the meta-analysis indicated that the MDR1 C1236T polymorphism may contribute to the susceptibility to adult leukemia and chronic myeloid leukemia. Furthe well-designed studies based on larger sample sizes are required to validate these findings.

Non-coding polymorphisms in nucleotide binding domain 1 in ABCC1 gene associate with transcript level and survival of patients with breast cancer

OBJECTIVES

ATP-Binding Cassette (ABC) transporters may cause treatment failure by transporting of anticancer drugs outside of the tumor cells. Multidrug resistance-associated protein 1 coded by the ABCC1 gene has recently been suggested as a potential prognostic marker in breast cancer patients. This study aimed to explore tagged haplotype covering nucleotide binding domain 1 of ABCC1 in relation with corresponding transcript levels in tissues and clinical phenotype of breast cancer patients.

METHODS

The distribution of twelve ABCC1 polymorphisms was assessed by direct sequencing in peripheral blood DNA (n = 540).

RESULTS

Tumors from carriers of the wild type genotype in rs35623 or rs35628 exhibited significantly lower levels of ABCC1 transcript than those from carriers of the minor allele (p = 0.003 and p = 0.004, respectively). The ABCC1 transcript levels significantly increased in the order CT-GT>CC-GT>CC-GG for the predicted rs35626-rs4148351 diplotype. Chemotherapy-treated patients carrying the T allele in rs4148353 had longer disease-free survival than those with the GG genotype (p = 0.043). On the other hand, hormonal therapy-treated patients with the AA genotype in rs35628 had significantly longer disease-free survival than carriers of the G allele (p = 0.012).

CONCLUSIONS

Taken together, our study shows that genetic variability in the nucleotide binding domain 1 has a significant impact on the ABCC1 transcript level in the target tissue and may modify survival of breast cancer patients.

Clinical impact of ABCC1 and ABCC2 genotypes and haplotypes in mediating imatinib resistance among chronic myeloid leukaemia patients

WHAT IS KNOWN AND OBJECTIVE

The introduction and success of imatinib mesylate (IM) has brought about a paradigm shift in chronic myeloid leukaemia (CML) treatment. However, despite the high efficacy of IM, clinical resistance develops due to a heterogeneous array of mechanisms. Pharmacogenetic variability as a result of genetic polymorphisms could be one of the most important factors influencing resistance to IM. The aim of this study was to investigate the association between genetic variations in drug efflux transporter ABCC1 (MRP1) and ABCC2 (MRP2) genes and response to IM in patients with CML.

METHODS

We genotyped 215 Malaysian patients with CML (comprising of two groups with 108 IM resistant and 107 IM responsive) for polymorphisms of ABCC1 (2012G>T and 2168G>A) and ABCC2 (-24C>T, 1249G>A and 3972C>T) genes. Genotype, allele and haplotype frequencies were compared between two groups of patients. Patients with CML were further stratified according to their clinical response to IM into those having cytogenetics and molecular responses, and the associations with genotypes were evaluated.

RESULTS AND DISCUSSION

We observed no significant differences in the distribution of any of the tested genotypes between the investigated groups. However, on evaluating the risk association, ABCC2 T₋₂₄ G₁₂₄₉ T₃₉₇₂ haplotype was found to be associated with IM resistance (P = 0·046). These results suggest that haplotype variants -24T and 3972T might be associated with lower expression of ABCC2 protein and reduced transport activity and hence might be contributing to development of IM resistance.

WHAT IS NEW AND CONCLUSION

Our results suggest the ABCC2 T₋₂₄ G₁₂₄₉ T₃₉₇₂ haplotype was associated with imatinib resistance. However, the evidence is as yet insufficient to establish this haplotype as a predictive biomarker for response to the drug.

The ATP7B genetic polymorphisms predict clinical outcome to platinum-based chemotherapy in lung cancer patients

This study aims to investigate the influence of ATP7B genetic polymorphism to platinum-based chemotherapy in Chinese Han lung cancer patients. A total of 338 Chinese Han lung cancer patients were enrolled in this study. All patients underwent at least two cycles of platinum-based chemotherapy. Four tag SNPs of ATP7B (rs1061472, rs9535826, rs7999812, and rs9535828) were selected to evaluate their impacts to platinum-based chemotherapy in these patients. ATP7B rs9535828 and rs9535826 were found to be associated with platinum resistance in Chinese Han lung cancer patients. Patients with A allele in ATP7B rs9535828 presented an increased susceptibility to platinum drugs (OR 1.96, 95 % CI 1.17-3.30, p < 0.01). Patients with G allele in ATP7B rs9535826 had the highest susceptibility to platinum drugs (OR 2.05, 95 % CI 1.19-3.52, p < 0.01). Our findings suggest that ATP7B genetic polymorphisms could affect the therapeutic efficacy of platinum-based chemotherapy, and ATP7B gene might be considered as predictive markers for the efficacy evaluation of platinum-based chemotherapy in Chinese Han lung cancer patients.

Importance of ABCC1 for cancer therapy and prognosis

Multidrug resistance presents one of the most important causes of cancer treatment failure. Numerous in vitro and in vivo data have made it clear that multidrug resistance is frequently caused by enhanced expression of ATP-binding cassette (ABC) transporters. ABC transporters are membrane-bound proteins involved in cellular defense mechanisms, namely, in outward transport of xenobiotics and physiological substrates. Their function thus prevents toxicity as carcinogenesis on one hand but may contribute to the resistance of tumor cells to a number of drugs including chemotherapeutics on the other. Within 48 members of the human ABC superfamily there are several multidrug resistance-associated transporters. Due to the well documented susceptibility of numerous drugs to efflux via ABC transporters it is highly desirable to assess the status of ABC transporters for individualization of treatment by their substrates. The multidrug resistance associated protein 1 (MRP1) encoded by ABCC1 gene is one of the most studied ABC transporters. Despite the fact that its structure and functions have already been explored in detail, there are significant gaps in knowledge which preclude clinical applications. Tissue-specific patterns of expression and broad genetic variability make ABCC1/MRP1 an optimal candidate for use as a marker or member of multi-marker panel for prediction of chemotherapy resistance. The purpose of this review was to summarize investigations about associations of gene and protein expression and genetic variability with prognosis and therapy outcome of major cancers. Major advances in the knowledge have been identified and future research directions are highlighted.

Two polymorphic variants of ABCC1 selectively alter drug resistance and inhibitor sensitivity of the multidrug and organic anion transporter multidrug resistance protein 1

In this study we compared the in silico predictions of the effect of ABCC1 nonsynonymous single nucleotide polymorphisms (nsSNPs) with experimental data on MRP1 transport function and response to chemotherapeutics and multidrug resistance protein 1 (MRP1) inhibitors. Vectors encoding seven ABCC1 nsSNPs were stably expressed in human embryonic kidney (HEK) cells, and levels and localization of the mutant MRP1 proteins were determined by confocal microscopy and immunoblotting. The function of five of the mutant proteins was determined using cell-based drug and inhibitor sensitivity and efflux assays, and membrane-based organic anion transport assays. Predicted consequences of the mutations were determined by multiple bioinformatic methods. Mutants C43S and S92F were correctly routed to the HEK cell plasma membrane, but the levels were too low to permit functional characterization. In contrast, levels and membrane trafficking of R633Q, G671V, R723Q, A989T, and C1047S were similar to wild-type MRP1. In cell-based assays, all five mutants were equally effective at effluxing calcein, but only two exhibited reduced resistance to etoposide (C1047S) and vincristine (A989T; C1047S). The GSH-dependent inhibitor LY465803 (LY465803 [N-[3-(9-chloro-3-methyl-4-oxo-4H-isoxazolo-[4,3-c]quinolin-5-yl)-cyclohexylmethyl]-benzamide)] was less effective at blocking calcein efflux by A989T, but in a membrane-based assay, organic anion transport by A989T and C1047S was inhibited by MRP1 modulators as well as wild-type MRP1. GSH accumulation assays suggest cellular GSH efflux by A989T and C1047S may be impaired. In conclusion, although six in silico analyses consistently predict deleterious consequences of ABCC1 nsSNPs G671V, changes in drug resistance and inhibitor sensitivity were only observed for A989T and C1047S, which may relate to GSH transport differences.

Nuclear multidrug-resistance related protein 1 contributes to multidrug-resistance of mucoepidermoid carcinoma mainly via regulating multidrug-resistance protein 1: a human mucoepidermoid carcinoma cells model and Spearman's rank correlation analysis

Background

Multidrug resistance-related protein 1 (MRP1/ABCC1) and multidrug resistance protein 1 (MDR1/P-glycoprotein/ABCB1) are both membrane-bound drug transporters. In contrast to MDR1, MRP1 also transports glutathione (GSH) and drugs conjugated to GSH. Due to its extraordinary transport properties, MRP1/ABCC1 contributes to several physiological functions and pathophysiological incidents. We previously found that nuclear translocation of MRP1 contributes to multidrug-resistance (MDR) of mucoepidermoid carcinoma (MEC). The present study investigated how MRP1 contributes to MDR in the nuclei of MEC cells.

Methods

Western blot and RT-PCR was carried out to investigate the change of multidrug-resistance protein 1 (MDR1) in MC3/5FU cells after MRP1 was downregulated through RNA interference (RNAi). Immunohistochemistry (IHC) staining of 127 cases of MEC tissues was scored with the expression index (EI). The EI of MDR1 and MRP1 (or nuclear MRP1) was analyzed with Spearman's rank correlation analysis. Using multiple tumor tissue assays, the location of MRP1 in other tissues was checked by HIC. Luciferase reporter assays of MDR1 promoter was carried out to check the connection between MRP1 and MDR1 promoter.

Results

MRP1 downregulation led to a decreased MDR1 expression in MC3/5FU cells which was caused by decreased activity of MDR1 promoter. IHC study of 127 cases of MEC tissues demonstrated a strong positive correlation between nuclear MRP1 expression and MDR1 expression. Furthermore, IHC study of multiple tumor tissue array sections showed that although nuclear MRP1 widely existed in MEC tissues, it was not found in normal tissues or other tumor tissues.

Conclusions

Our findings indicate that nuclear MRP1 contributes to MDR mainly through regulating MDR1 expression in MEC. And the unique location of MRP1 made it an available target in identifying MEC from other tumors.

The association between polymorphisms in the MDR1 gene and risk of cancer: a systematic review and pooled analysis of 52 case-control studies

Background

The multidrug resistance (MDR) 1 gene encodes a 170-kDa membrane transporter called P-glycoprotein, which plays an important role in protecting cells against lipophilic xenobiotics by the way of an ATP-dependent cellular efflux mechanism. Three polymorphisms of MDR1, 3435C > T located in exon 26, 1236C > T in exon 12 and 2677G > T/A in exon 21 were the most extensively studied and were identified functionally important and ethnically diverse mapping to the gene region. Considering the potential influence of altering MDR1 activity, it is plausible that MDR1 polymorphisms might play a role in the development of cancer. Although the effects of MDR1 polymorphisms on susceptibility to human cancer have been investigated in many studies, the results still remain conflicting.

Methods

To resolve these conflicts, we performed a quantitative synthesis of the association between these three polymorphisms and cancer risk, including 52 studies (15789 cases and 20274 controls) for 3435C > T polymorphism, 10 studies (2101 cases and 2842 controls) for 1236C > T polymorphism and 18 studies (3585 cases and 4351 controls) for 2677G > T/A polymorphism.

Results

The stratified analyses for 3435C > T polymorphism, individuals with T-allele in 3435C > T had significantly higher ALL risks (TT versus CC: OR =1.286, 95% CI =1.123-1.474); significantly elevated risks were observed among Caucasian populations (TT versus CC: OR =1.276, 95% CI =1.112-1.464). When restricting the analysis to the source of controls, we found that HB (hospital-based) genetic models had higher risks (TT versus CC: OR =1.307, 95% CI =1.046-1.632), as well as in PB (population-based) genetic models (TT versus CC: OR =1.294, 95% CI =1.079-1.55).

The T/A-allele frequency of 2677G > T/A polymorphism was associated with higher risk of cancer (TT + TA + AA vs. GG: OR =1.348, 95% CI =1.031-1.762), significantly elevated risks were observed among Asian populations (TT + TA + AA vs. GG: OR =1.642, 95% CI =1.340-2.012), and elevated risks could be associated with PB models (TT + TA + AA vs. GG: OR =1.641, 95% CI =1.018-2.646).

Conclusions

Our meta-analysis suggested that 3435C > T polymorphism and 2677G > T/A polymorphism were associated with cancer risk when all studies were pooled together, while 1236C > T polymorphism not.

Translational regulation of RPA2 via internal ribosomal entry site and by eIF3a

RPA2 is a subunit of a trimeric replication protein A (RPA) complex important for DNA repair and replication. Although it is known that RPA activity is regulated by post-translational modification, whether RPA expression is regulated and the mechanism therein is currently unknown. eIF3a, the largest subunit of eIF3, is an important player in translational control and has been suggested to regulate translation of a subset of messenger RNAs important for tumorigenesis, metastasis, cell cycle progression, drug response and DNA repair. In the present study, we show that RPA2 expression is regulated at translational level via internal ribosome entry site (IRES)-mediated initiation in response to DNA damage. We also found that eIF3a suppresses RPA2 synthesis and inhibits its cellular IRES activity by directly binding to the IRES element of RPA2 located at -50 to -150 bases upstream of the translation start site. Taken together, we conclude that RPA2 expression is translationally regulated via IRES and by eIF3a and that this regulation is partly accountable for cellular response to DNA damage and survival.

Multidrug resistance-associated protein 1 (MRP1/ABCC1) polymorphism: from discovery to clinical application

Multidrug resistance-associated protein 1(MRP1/ABCC1) is the first identified member of ABCC subfamily which belongs to ATP-binding cassette (ABC) transporter superfamily. It is ubiquitously expressed in almost all human tissues and transports a wide spectrum of substrates including drugs, heavy metal anions, toxicants, and conjugates of glutathione, glucuronide and sulfate. With the advance of sequence technology, many MRP1/ABCC1 polymorphisms have been identified. Accumulating evidences show that some polymorphisms are significantly associated with drug resistance and disease susceptibility. In vitro reconstitution studies have also unveiled the mechanism for some polymorphisms. In this review, we present recent advances in understanding the role and mechanism of MRP1/ABCC1 polymorphisms in drug resistance, toxicity, disease susceptibility and severity, prognosis prediction, and Methods to select and predict functional polymorphisms.

Meta-analysis on pharmacogenetics of platinum-based chemotherapy in non small cell lung cancer (NSCLC) patients

AIM

To determine the pharmacogenetics of platinum-based chemotherapy in Non Small Cell Lung Cancer (NSCLC) patients.

METHODS

Publications were selected from PubMed, Cochrane Library and ISI Web of Knowledge. A meta-analysis was conducted to determine the association between genetic polymorphisms and platinum-based chemotherapy by checking odds ratio (OR) and 95% confidence interval (CI).

RESULTS

Data were extracted from 24 publications, which included 11 polymorphisms in 8 genes for meta-analysis. MDR1 C3435T (OR = 1.97, 95% CI: 1.11-3.50, P = 0.02), G2677A/T (OR = 2.61, 95% CI: 1.44-4.74, P = 0.002) and GSTP1 A313G (OR = 0.32, 95% CI: 0.17-0.58, P = 0.0002) were significantly correlated with platinum-based chemotherapy in Asian NSCLC patients.

CONCLUSION

Attention should be paid to MDR1 C3435T, G2677A/T and GSTP1 A313G for personalized chemotherapy treatment for NSCLC patients in Asian population in the future.

ABCC1 polymorphism Arg723Gln (2168G> A) is associated with lung cancer susceptibility in a Chinese population

1. In a previous in vitro study, we showed that the Arg723Gln (2168G > A) polymorphism significantly ABCC1-induced multidrug resistance. The aim of the present study was to further investigate the association of this polymorphism with lung cancer susceptibility and chemotherapy response in a Chinese population. 2. A total of 77 lung cancer patients (54 men, 23 women) and 71 cancer-free controls (49 men, 22 women) were enrolled in the study. Genomic DNA was extracted from peripheral blood and all samples were genotyped using polymerase chain reaction-restriction fragment length polymorphism. 3. Individuals carrying the 723Gln (A) allele have a 3.4-fold increased risk (adjusted odds ratio (OR) 3.42; 95% confidence interval (CI) 1.29-9.06; P = 0.013) of lung cancer compared with wild-type individuals. Further stratified analysis indicated that older individuals (> 50 years) carrying the 723Gln (A) allele have the highest susceptibility to lung cancer (adjusted OR 4.10; 95% CI 1.25-13.48; P = 0.020). However, no substantial association was found between the Arg723Gln (2168G > A) polymorphism and chemotherapy response in Chinese lung cancer patients. 4. In conclusion, the Arg723Gln (2168G > A) polymorphism of ABCC1 appears to be a potential susceptibility marker for lung cancer in the Chinese population, especially in older people.

Effect of eIF3a on response of lung cancer patients to platinum-based chemotherapy by regulating DNA repair

PURPOSE

The purpose of this study is to test the hypothesis that eIF3a may regulate the expression of DNA repair proteins which, in turn, affects response of lung cancer patients to treatments by DNA-damaging anticancer drugs.

EXPERIMENTAL DESIGN

Immunohistochemistry was used to determine the expression of eIF3a in 211 human lung cancer tissues followed by association analysis of eIF3a expression with patient's response to platinum-based chemotherapy. Ectopic overexpression and RNA interference knockdown of eIF3a were carried out in NIH3T3 and H1299 cell lines, respectively, to determine the effect of altered eIF3a expression on cellular response to cisplatin, doxorubicine, etoposide (VP-16), vincristine, and vinblastine by using MTT assay. The DNA repair capacity of these cells was evaluated by using host-cell reactivation assay. Real-time reverse transcriptase PCR and Western Blot analyses were carried out to determine the effect of eIF3a on the DNA repair genes by using cells with altered eIF3a expression.

RESULTS

eIF3a expression associates with response of lung cancer patients to platinum-based chemotherapy. eIF3a knockdown or overexpression, respectively, increased and decreased the cellular resistance to cisplatin and anthrocycline anticancer drugs, DNA repair activity, and expression of DNA repair proteins.

CONCLUSIONS

eIF3a plays an important role in regulating the expression of DNA repair proteins which, in turn, contributes to cellular response to DNA-damaging anticancer drugs and patients' response to platinum-based chemotherapy.