PHARMACOGENOMICS OF ACUTE LEUKEMIA

Pharmacogenetics of ABCB1, CDA, DCK, GSTT1, GSTM1 and outcomes in a cohort of pediatric acute myeloid leukemia patients from Colombia

BACKGROUND AND AIM

Different studies have shown pharmacogenetic variants related to drug toxicity in acute myeloid leukemia (AML) patients. Our aim was to identify the association between ABCB1, CDA, DCK, GSTT1, and GSTM1 variants with clinical outcomes and toxicity in pediatric patients with AML.

METHODS

Fifty-one confirmed de novo AML pediatric patients were included. A SNaPshot™ assay and conventional PCR were used to evaluate ABCB1, CDA, DCK, GSTT1, and GSTM1 variants. Clinical outcomes and toxicity associations were evaluated using odds ratios and Chi-square analysis.

RESULTS

Patients carrying ABCB1 (1236C > T, rs1128503) GG genotype in had a 6.8 OR (CI 95% 1.08-42.73, p = .044) for cardiotoxicity as compared to patients carrying either AA or GA genotypes 0.14 OR (CI 95% 0.023-0.92, p = .044). For ABCB1 (1236G > A rs1128503/2677C > A/T rs2032582/3435G > A rs1045642) AA/AA/AA combined genotypes had a strong association with death after HSTC OR 13.73 (CI 95% 1.94-97.17, p = .009). Combined genotypes GG/CC/GG with CDA (79A > C, rs2072671) CA genotype or CDA (-451G > A, rs532545) CT genotype, had a 4.11 OR (CI 95% 2.32-725, p = .007) and 3.8 OR (CI 95% 2.23-6.47, p = .027) with MRD >0.1% after first chemotherapy cycle, respectively.

CONCLUSION

Our results highlight the importance of pharmacogenetic analysis in pediatric AML, particularly in populations with a high degree of admixture, and might be useful as a future tool for patient stratification for treatment.

Pharmacogenetics and the treatment of chronic myeloid leukemia: how relevant clinically? An update

Despite the excellent efficacy and improved clinical responses obtained with imatinib mesylate (IM), development of resistance in a significant proportion of chronic myeloid leukemia (CML) patients on IM therapy have emerged as a challenging problem in clinical practice. Resistance to imatinib can be due to heterogeneous array of factors involving BCR/ABL-dependent and BCR/ABL-independent pathways. Although BCR/ABL mutation is the major contributory factor for IM resistance, reduced bio-availability of IM in leukemic cells is also an important pharmacokinetic factor that contributes to development of resistance to IM in CML patients. The contribution of polymorphisms of the pharmacogenes in relation to IM disposition and treatment outcomes have been studied by various research groups in numerous population cohorts. However, the conclusions arising from these studies have been highly inconsistent. This review encompasses an updated insight into the impact of pharmacogenetic variability on treatment response of IM in CML patients.

ABCB1 genetic variants in leukemias: current insights into treatment outcomes

Despite improvements in treatment of different types of leukemia, not all patients respond optimally for a particular treatment. Some treatments will work better for some, while being harmful or ineffective for others. This is due to genetic variation in the form of single-nucleotide polymorphisms (SNPs) that affect gene expression or function and cause inherited interindividual differences in the metabolism and disposition of drugs. Drug transporters are one of the determinants governing the pharmacokinetic profile of chemotherapeutic drugs. The ABCB1 transporter gene transports a wide range of drugs, including drugs used in leukemia treatment. Polymorphisms in the ABCB1 gene do affect intrinsic resistance and pharmacokinetics of several drugs used in leukemia treatment protocols and thereby affect the efficacy of treatment and event-free survival. This review focuses on the impact of three commonly occurring SNPs (1236C>T, 2677G>T/A, and 3435C>T) of ABCB1 on treatment response of various types of leukemia. From the literature available, some of the genotypes and haplotypes of these SNPs have been found to be potential determinants of interindividual variability in drug disposition and pharmacologic response in different types of leukemia. However, due to inconsistencies in the results observed across the studies, additional studies, considering novel genomic methodologies, comprehensive definition of clinical phenotypes, adequate sample size, and uniformity in all the confounding factors, are warranted.

Methotrexate resistance in relation to treatment outcome in childhood acute lymphoblastic leukemia

Background

Methotrexate (MTX) eradicates leukemic cells by disrupting de novo nucleotide biosynthesis and DNA replication, resulting in cell death. Since its introduction in 1947, MTX-containing chemotherapeutic regimens have proven instrumental in achieving curative effects in acute lymphoblastic leukemia (ALL). However, drug resistance phenomena pose major obstacles to efficacious ALL chemotherapy. Moreover, clinically relevant molecular mechanisms underlying chemoresistance remain largely obscure. Several alterations in MTX metabolism, leading to impaired accumulation of this cytotoxic agent in tumor cells, have been classified as determinants of MTX resistance. However, the relation between MTX resistance and long-term clinical outcome of ALL has not been shown previously.

Methods

We have collected clinical data for 235 childhood ALL patients, for whom samples taken at the time of diagnosis were also broadly characterized with respect to MTX resistance. This included measurement of concentrations of MTX polyglutamates in leukemic cells, mRNA expression of enzymes involved in MTX metabolism (FPGS, FPGH, RFC, DHFR, and TS), MTX sensitivity as determined by the TS inhibition assay, and FPGS activity.

Results

Herein we demonstrate that higher accumulation of long-chain polyglutamates of MTX is strongly associated with better overall (10-year OS: 90.6 vs 64.1 %, P = 0.008) and event-free survival (10-year EFS: 81.2 vs 57.6 %, P = 0.029) of ALL patients. In addition, we assessed both the association of several MTX resistance-related parameters determined in vitro with treatment outcome as well as clinical characteristics of pediatric ALL patients treated with MTX-containing combination chemotherapy. High MTX sensitivity was associated with DNA hyperdiploid ALL (P < 0.001), which was linked with increased MTX accumulation (P = 0.03) and elevated reduced folate carrier (RFC) expression (P = 0.049) in this subset of ALL patients. TEL-AML1 fusion was associated with increased MTX resistance (P = 0.023). Moreover, a low accumulation of MTX polyglutamates was observed in MLL-rearranged and TEL-AML1 rearranged ALL (P < 0.05).

Conclusions

These findings emphasize the central role of MTX in ALL treatment thereby expanding our understanding of the molecular basis of clinical differences in treatment response between ALL individuals. In particular, the identification of patients that are potentially resistant to MTX at diagnosis may allow for tailoring novel treatment strategies to individual leukemia patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-015-0158-9) contains supplementary material, which is available to authorized users.

Role of single nucleotide polymorphisms in pharmacogenomics and their association with human diseases

Global statistical data shed light on an alarming trend that every year thousands of people die due to adverse drug reactions as each individual responds in a different way to the same drug. Pharmacogenomics has come up as a promising field in drug development and clinical medication in the past few decades. It has emerged as a ray of hope in preventing patients from developing potentially fatal complications due to adverse drug reactions. Pharmacogenomics also minimizes the exposure to drugs that are less/non-effective and sometimes even found toxic for patients. It is well reported that drugs elicit different responses in different individuals due to variations in the nucleotide sequences of genes encoding for biologically important molecules (drug-metabolizing enzymes, drug targets and drug transporters). Single nucleotide polymorphisms (SNPs), the most common type of polymorphism found in the human genome is believed to be the main reason behind 90% of all types of genetic variations among the individuals. Therefore, pharmacogenomics may be helpful in answering the question as to how inherited differences in a single gene have a profound effect on the mobilization and biological action of a drug. In the present review, we have discussed clinically relevant examples of SNP in associated diseases that can be utilized as markers for "better management of complex diseases" and attempted to correlate the drug response with genetic variations. Attention is also given towards the therapeutic consequences of inherited differences at the chromosomal level and how associated drug disposition and/or drug targets differ in various diseases as well as among the individuals.

Prevalence of TPMT and ITPA gene polymorphisms and effect on mercaptopurine dosage in Chilean children with acute lymphoblastic leukemia

BACKGROUND

Mercaptopurine (6-MP) plays a pivotal role in treatment of childhood acute lymphoblastic leukemia (ALL); however, interindividual variability in toxicity of this drug due to genetic polymorphism in 6-MP metabolizing enzymes has been described. We determined the prevalence of the major genetic polymorphisms in 6-MP metabolizing enzymes in Chilean children with ALL.

METHODS

103 Chilean pediatric patients with a confirmed diagnosis of ALL were enrolled. DNA was isolated from whole blood and genetic polymorphism in thiopurine S-methyltransferase (TPMT) and inosine triphosphate pyrophosphatase (ITPA) coding genes were detected by polymorphism chain reaction-restriction fragment length (PCR-RFLP) assay.

RESULTS

The total frequency of variant TPMT alleles was 8%. TPMT*2, TPMT*3A and TPMT*3B alleles were found in 0%, 7%, and 1% of patients, respectively. For ITPA, the frequency of P32T allele was 3%. We did not observe any homozygous variant for TPMT and ITPA alleles. We also analyzed a subgroup of 40 patients who completed the maintenance phase of ALL treatment, and we found that patients carrying a TPMT gene variant allele required a significantly lower median cumulative dosage and median daily dosage of 6-MP than patients carrying wild type alleles.

CONCLUSION

TMPT genotyping appears an important tool to further optimize 6-MP treatment design in Chilean patients with ALL.

Lymphohematopoietic cancers induced by chemicals and other agents and their implications for risk evaluation: An overview

Lymphohematopoietic neoplasia are one of the most common types of cancer induced by therapeutic and environmental agents. Of the more than 100 human carcinogens identified by the International Agency for Research on Cancer, approximately 25% induce leukemias or lymphomas. The objective of this review is to provide an introduction into the origins and mechanisms underlying lymphohematopoietic cancers induced by xenobiotics in humans with an emphasis on acute myeloid leukemia, and discuss the implications of this information for risk assessment. Among the agents causing lymphohematopoietic cancers, a number of patterns were observed. Most physical and chemical leukemia-inducing agents such as the therapeutic alkylating agents, topoisomerase II inhibitors, and ionizing radiation induce mainly acute myeloid leukemia through DNA-damaging mechanisms that result in either gene or chromosomal mutations. In contrast, biological agents and a few immunosuppressive chemicals induce primarily lymphoid neoplasms through mechanisms that involve alterations in immune response. Among the environmental agents examined, benzene was clearly associated with acute myeloid leukemia in humans, with increasing but still limited evidence for an association with lymphoid neoplasms. Ethylene oxide and 1,3-butadiene were linked primarily to lymphoid cancers. Although the association between formaldehyde and leukemia remains controversial, several recent evaluations have indicated a potential link between formaldehyde and acute myeloid leukemia. The four environmental agents examined in detail were all genotoxic, inducing gene mutations, chromosomal alterations, and/or micronuclei in vivo. Although it is clear that rapid progress has been made in recent years in our understanding of leukemogenesis, many questions remain for future research regarding chemically induced leukemias and lymphomas, including the mechanisms by which the environmental agents reviewed here induce these diseases and the risks associated with exposures to such agents.

Validation of a genotyping method for analysis of TPMT polymorphisms

BACKGROUND

Thiopurine methyltransferase (TPMT) catalyzes the methylation of thiopurine drugs such as azathioprine and 6-mercaptopurine. Several mutations in the TPMT gene correlate with low enzyme activity and adverse effects such as myelotoxicity. Hence, genotyping TPMT makes it possible to identify patients at high risk for drug toxicity.

OBJECTIVE

The aim of this study was to validate a TPMT genotyping method by comparing it with a conventional polymerase chain reaction (PCR) approach.

METHODS

LightSNiP is a real-time PCR method for the detection of TPMT*2, *3B, and *3C without a sequencing step. We evaluated the frequencies of 3 TPMT alleles in 111 white adult patients by comparing genotyping by LightSNiP with conventional PCR (sequencing).

RESULTS

No differences were observed between conventional genotyping with sequencing and LightSNiP for *2, *3B, and *3C, suggesting the validity of this method.

CONCLUSIONS

Compared with the conventional PCR sequencing method, the data suggest that LightSNiP correctly detected the TPMT *2, *3B, and *3C in this select population.

Polymorphisms of the SLCO1B1 gene predict methotrexate-related toxicity in childhood acute lymphoblastic leukemia

BACKGROUND

Methotrexate (MTX) is an important component of the therapy for childhood acute lymphoblastic leukemia. Treatment with high-dose MTX often causes toxicity, recommending a dose reduction and/or cessation of treatment. Polymorphisms in genes involved in the MTX metabolism have been associated with toxicity with controversial results. The discrepancies could be due to differences in treatment protocols among studies, small, or non-homogeneous populations or the use of different toxicity criteria. The aim of the present study was to analyze the possible correlation of polymorphisms of genes involved in the MTX metabolism with the toxicity during therapy with the well-established LAL/SHOP protocol.

PROCEDURE

We analyzed 10 polymorphisms in seven genes (MTHFR, TS, SHMT1, RFC1, ABCB1, ABCG2, and SLCO1B1) from the MTX metabolism in 115 Spanish pediatric B-ALL patients, using MTX plasma concentration as an objective and quantifiable marker of toxicity.

RESULTS

We confirmed the suitability of MTX plasma levels as a toxicity marker. We found a statistically significant association between MTX plasma concentration and the SLCO1B1 rs11045879 CC genotype (P = 0.030). The rs4149081 AA genotype, in the same gene, could also be an indicator for high-MTX plasma concentrations. We did not find any significant association in the other genetic polymorphisms analyzed.

CONCLUSIONS

Identification of the rs4149081 and rs11045879 SLCO1B1 polymorphisms in children with ALL could be a useful tool for monitoring patients at risk of low-MTX clearance in order to avoid MTX-related toxicity.

Patterns of pharmacogenetic diversity in African populations: role of ancient and recent history

AIMS

The knowledge that genetic variation influencing drug response is clearly structured among human populations has prompted many studies aimed at obtaining pharmacogenetic profiles in specific populations. While large amounts of data are being produced for populations from developed countries, the African continent still remains very poorly studied. To help to fill this gap, this work characterized three previously uncharacterized African populations for a set of pharmacogenetically relevant polymorphisms.

MATERIALS & METHODS

Seven polymorphic variations in four genes that encode enzymes from phase I (CYP2C9, CYP3A4 and CYP3A5) or phase III (ABCB1) of drug metabolism were analyzed in population samples from Cabinda (n = 107), Mozambique (n = 109) and São Tomé e Príncipe (n = 126). All three populations shared strong recent historical links with Portugal.

RESULTS

The majority of the screened variations displayed large contrasts in allele frequencies between European and African populations, and this study identified a substantial higher European influence in São Tomé e Príncipe than in Cabinda or Mozambique. Admixture analysis demonstrated that the European contribution to the population of São Tomé e Príncipe amounted to 13.3 +/- 3.3%. Furthermore, the proportion of African or European pharmacogenetic ancestry varied widely across each São Tomean individual.

DISCUSSION & CONCLUSION

This implies that genetic association studies conducted in São Tomé e Príncipe should take into account the confounding factor of admixture to avoid spurious positive or negative results. Our findings also indicate that drug dosage requirements may be different in São Tomé e Príncipe than in other African populations. Thus, the search for pharmacogenetic risk factors should be assessed at an individual level, therefore fulfilling the perspective of personalized medicine. This study further indicates that the common notion of 'African population' might hide a pattern of pharmacogenetic heterogeneity whose real extent still needs to be evaluated by means of a refined sampling of the entire continent.

Pharmacogenomics in acute myeloid leukemia

Acute myeloid leukemia (AML) in adults is a heterogeneous malignant pathology with a globally unfavorable prognosis. The classification of AML allows identification of subgroups with favorable prognosis. However, besides these specific subgroups, most patients will have an intermediate or unfavorable prognosis often resulting in induction failure, probably due to drug resistance of the leukemic blasts, and more frequently resulting in early relapse after achieving complete remission. This unfavorable situation leads to a strong need to develop new diagnostic and therapeutic options. However, development of these therapies and their efficient use requires a better understanding of the biology and the molecular pathogenesis of AML. Pharmacogenomics focuses on the genetic variation of drug-metabolizing enzymes, targets and transporters, and how these genetic variations interact to produce specific drug-related phenotypes. Potential genetic markers may serve to functionally subclassify patients by their disease and therefore influence the nature and intensity of treatment. This review summarizes important aspects of and recent advances in the field of pharmacogenomics in AML.

Pharmacogenetics influence treatment efficacy in childhood acute lymphoblastic leukemia

Pharmacogenetics covers the genetic variation affecting pharmacokinetics and pharmacodynamics, and their influence on drug-response phenotypes. The genetic variation includes an estimated 15 million single nucleotide polymorphisms (SNPs) and is a key determinator for the interindividual differences in treatment resistance and toxic side effects. As most childhood acute lymphoblastic leukemia treatment protocols include up to 13 different chemotherapeutic agents, the impact of individual SNPs has been difficult to evaluate. So far focus has mainly been on the widely used glucocorticosteroids, methotrexate, and thiopurines, or on metabolic pathways and transport mechanisms that are common to several drugs, such as the glutathione S-transferases. However, beyond the thiopurine methyltransferase polymorphisms, the candidate-gene approach has not established clear associations between polymorphisms and treatment response. In the future, high-throughput, low-cost, genetic platforms will allow screening of hundreds or thousands of targeted SNPs to give a combined gene-dosage effect (=individual SNP risk profile), which may allow pharmacogenetic-based individualization of treatment.

Host factors and consequence of chemotherapy in pediatric cancer patients

The 5-year survival rates for childhood ALL are approaching 80%, but therapy-related toxicities are common. One of the challenges in this population is determining the most efficacious therapeutic regimens for these individuals. Factors such as drug metabolism, genetics, and concomitant disease affect drug efficacy and may be important in determining therapeutic outcomes in these patients. This review will focus on these factors in the treatment of childhood ALL.

Highly multiplexed genotyping of thiopurine s-methyltransferase variants using MALD-TOF mass spectrometry: reliable genotyping in different ethnic groups

BACKGROUND

To avoid severe hematotoxicity in patients, determination of the TPMT (thiopurine S-methyltransferase) genotype before commencing thiopurine therapy has become accepted.

METHODS

We used MALDI-TOF mass spectrometry (MS) based on Sequenom iPLEX technology to develop novel multiplex assays for comprehensive testing of TPMT. Two assays, a 15-plex and a 7-plex assay, consisting of multiplex PCR, shrimp alkaline phosphatase treatment, primer extension, and MALDI-TOF MS analysis, allow detection of all currently known functionally relevant 24 TPMT alleles (TPMT*2 to *18, *20 to *23). Previously identified variant DNA samples and newly constructed synthetic templates were used as quality controls.

RESULTS

Assay evaluation performed on a panel of 586 genomic DNA samples previously genotyped by other methods (denaturing HPLC, sequencing) resulted in 100% agreement. Analyses of the distribution of TPMT alleles in 116 samples from a Ghanaian population revealed a TPMT*8 allele frequency of 3.4%. In a Korean population of 118 unrelated individuals, we found a TPMT*6 allele frequency of 1.3%.

CONCLUSIONS

The newly developed multiplex MALDI-TOF MS assay allows efficient genotyping for all currently known functional TPMT variants. To achieve the most accurate prediction of TPMT phenotype, molecular diagnosis of TPMT should include all these variants.

Polymorphisms in transporter and phase II metabolism genes as potential modifiers of the predisposition to and treatment outcome of de novo acute myeloid leukemia in Israeli ethnic groups

Drug metabolism/disposition and transporter genes may influence predisposition or prognosis of AML (acute myeloid leukemia) patients. We analyzed polymorphisms in 3 transporters and 4 drug metabolism genes in 293 Israeli individuals (112 AML patients and 181 controls). We analyzed: ABCC3 (MRP3) C-211T; ABCG2 (BCRP) C421A; CNT1 (SLC28A1) G565A and NAT1, NAT2, and GSTT1 and GSTM1 null alleles for influence on predisposition, as well as treatment response and survival. We found that the ABCC3 C-211T polymorphism and GSTM1 null genotype have adverse prognostic significance in AML. None of the other polymorphisms studied were found to influence either predisposition or prognosis in Israeli AML patients.

Pharmacogenomics of acute leukemia

Pharmacogenomics provides knowledge regarding how genetic polymorphisms affect treatment responses. Such an approach is particularly needed in cancer therapy, as most chemotherapeutics drugs affect both tumor and normal cells, are ineffective in many patients and exhibit serious side effects. Leukemia exists in two different forms, myeloid and lymphoid. Acute lymphoblastic leukemia more frequently occurs in children, whereas the risk of acute myeloid leukemia is more common in adults. Despite significant progress in the treatment of these diseases, therapy is still unsuccessful in many patients. Prognosis is particularly poor in adult acute myeloid leukemia. Treatment failure in childhood acute lymphoblastic leukemia due to drug resistance remains the leading cause of cancer-related death in children. Here, we provide an overview of pharmacogenetics studies carried out in children and adults with acute lymphoblastic leukemia and acute myeloid leukemia, attempting to find the associations between treatment responses and polymorphisms in the genes whose products are needed for metabolism, and effects of drugs used in the treatment of leukemia.

Pharmacogenomics in cancer treatment defining genetic bases for inter-individual differences in responses to chemotherapy

PURPOSE OF REVIEW

Pharmacogenomics is evolving rapidly due to the expansion of genomics and proteomics, the emerging technologies, knowledge of the molecular basis of neoplasms and of drug pathways. This article will give an update on the genetic basis of variable therapeutic responses to anticancer agents in children.

RECENT FINDINGS

The majority of recent findings concern the pharmacogenetics of key components of acute lymphoblastic leukemia treatment, 6-mercaptopurine and methotrexate. This is not surprising given that leukemia is the most common cancer affecting children, accounting for 25-35% of childhood malignancies worldwide with acute lymphoblastic leukemia comprising 80% of leukemia cases. In certain patients treatment fails due to drug resistance, rendering acute lymphoblastic leukemia the leading cause of cancer-related death in children. Most of the studies use a candidate gene approach adding a new body of evidence to existing knowledge. Recent findings relating to other childhood tumors and the potential to optimize treatment of these malignancies are briefly discussed.

SUMMARY

Interindividual differences in drug responses are an important cause of resistance to treatment and adverse drug reactions. Pharmacogenetics tends to identify the genetic basis of these suboptimal responses allowing traditional treatment to be complemented by genotype-based drug dose adjustment.

HapMap, pharmacogenomics, and the goal of personalized prescribing

Most of the gene variants that have been identified in the last 50 years have affected individual drug responses through effects on pharmacokinetics. Gene variants that affect a drug's pharmacodynamics, such as polymorphisms in receptors or signalling molecules, have been more difficult to identify. This often requires a more systematic and genome-wide approach, prompting the emergence of the new discipline of pharmacogenomics. The provision of the human genomic sequence and now data from the HapMap project look set to bring 'personalized prescription' a step closer.

Pharmacogenomics of acute lymphoblastic leukemia

PURPOSE OF REVIEW

The cure rate in children with acute lymphoblastic leukemia now exceeds almost 80% in most treatment protocols in industrialized countries. This has mainly been achieved empirically through carefully controlled, randomized clinical trials. Due to relative nonspecific action and narrow therapeutic indices of antileukemic medications, however, current therapy can be associated with significant short and long-term adverse effects, and around 20% of patients will not be cured despite intensified treatment. Pharmacogenomics, which studies the role of inheritance in individual variation in drug disposition and response, could be a useful tool to further improve outcome in this heterogeneous disease by individualization of therapy based on information gained from the genetic 'make-up' of normal host cells and lymphoblastic leukemia cells.

RECENT FINDINGS

The focus of this review is on recent progress in the field by discussing the results of selected studies in which information from functional genomics, high-throughput molecular analyses, and pharmacodynamics has been integrated to establish pharmacogenomic models. These models may be used to both maximize efficacy and minimize toxicity of existing antileukemic medications, or to identify novel therapeutic targets in lymphoblasts that are resistant to conventional antileukemic drugs.

SUMMARY

The findings from recent pharmacogenomic studies can be integrated into decision-making in future clinical trials. Thus there is great promise for advancing event-free survival in childhood leukemia in the future.

Personalized medicine: new perspectives - new ethics?

Are new concepts in biomedical ethics required to keep pace with the developments in post-Human Genome Project (HGP) genomics? This paper traces the place of ethics in the post-HGP landscape. The need for a revision of the approach taken by biomedical ethics toward questions in genomics has been appreciated for years. Traditional biomedical ethics, led by the protection paradigm, was devised to serve a very different context. Today, compelling ethical questions arise from the tension between individual and collective interests in the context of population-based data collection and research. The collection of phenotype data, and the development of new sequencing technologies, raises burning questions that call for innovative tools and models in ethics. Future developments that will likely include the routine availability of personal genome information, and the advent of systems biology as a framework for interpretation, will require ongoing flexibility and a creative approach.