Advances in the development of genetic markers for the diagnosis of disease and drug response

The Translation of Nanomedicines in the Contexts of Spinal Cord Injury and Repair

PURPOSE OF THIS REVIEW

Manipulating or re-engineering the damaged human spinal cord to achieve neuro-recovery is one of the foremost challenges of modern science. Addressing the restricted permission of neural cells and topographically organised neural tissue for self-renewal and spontaneous regeneration, respectively, is not straightforward, as exemplified by rare instances of translational success. This review assembles an understanding of advances in nanomedicine for spinal cord injury (SCI) and related clinical indications of relevance to attempts to design, engineer, and target nanotechnologies to multiple molecular networks.

RECENT FINDINGS

Recent research provides a new understanding of the health benefits and regulatory landscape of nanomedicines based on a background of advances in mRNA-based nanocarrier vaccines and quantum dot-based optical imaging. In relation to spinal cord pathology, the extant literature details promising advances in nanoneuropharmacology and regenerative medicine that inform the present understanding of the nanoparticle (NP) biocompatibility-neurotoxicity relationship. In this review, the conceptual bases of nanotechnology and nanomaterial chemistry covering organic and inorganic particles of sizes generally less than 100 nm in diameter will be addressed. Regarding the centrally active nanotechnologies selected for this review, attention is paid to NP physico-chemistry, functionalisation, delivery, biocompatibility, biodistribution, toxicology, and key molecular targets and biological effects intrinsic to and beyond the spinal cord parenchyma.

SUMMARY

The advance of nanotechnologies for the treatment of refractory spinal cord pathologies requires an in-depth understanding of neurobiological and topographical principles and a consideration of additional complexities involving the research's translational and regulatory landscapes.

Molecular diagnostics of acute intermittent porphyria

Acute intermittent porphyria (AIP) is an inherited metabolic disease with an autosomal dominant pattern of inheritance. The disease is caused by a partial deficiency of porphobilinogen deaminase (PBGD) in heme biosynthesis. Since biochemical measurements of patients and their healthy relatives overlap, the diagnosis of AIP may remain undetermined at the symptom-free phase. Mutation detection in AIP, which provides 95% sensitivity and around 100% specificity, has quickly been incorporated into good clinical practice. During an acute attack, which includes various neurovisceral symptoms, measurement of urinary porphobilinogen (PBG) is a method of choice to confirm diagnosis, and DNA testing is unnecessary at that stage. DNA testing has revealed many new patients and excluded AIP from many healthy relatives despite slightly increased excretions of porphyrin precursors and erythrocyte PBGD in the low or borderline zone. Thus, quality-assured DNA testing is accurate enough to confirm or exclude the diagnosis of AIP. The clinical utility of DNA testing is limited for those individuals whose mutation is currently unknown, in which biochemical analyses are essential and the majority of the patients can be identified using urinary PBG and erythrocyte PBGD measurements. The measurement of urinary PBG can be used to evaluate the prognosis for symptom-free individuals. Currently, DNA testing of AIP at the population level is not recommended unless the frequency of gene carriers is locally very high and large-scale population-based mutation screening is reasonable. In the future, the knowledge of gene-gene and gene-environment interactions and protein networks using gene array and proteomics technologies may provide more precise information about pathogenetic mechanisms and novel therapeutic strategies for an acute attack and the long-term complications of AIP. Increasing knowledge of pharmacogenetics may identify the patients who are at high risk for clinical manifestations.

Eosinophil cationic protein: overview of biological and genetic features

The eosinophil cationic protein (ECP) is a small polypeptide that originates from activated eosinophil granulocytes. A wide range of stimuli has been shown to induce the secretion of ECP. The gene that encodes the human ECP is located on chromosome 14, and the protein shares the overall three-dimensional structure and the RNase active-site residues with other proteins in the RNase A superfamily. Several single-nucleotide polymorphisms in the human ECP gene have been currently described. ECP has many biological functions, including an immunoregulatory function, the regulation of fibroblast activity, and the induction of mucus secretion in the airway. Additionally, the protein is a potent cytotoxic molecule and has the capacity to kill mammalian and nonmammalian cells. The purpose of this article was to review the known biological and genetic characteristics of ECP that contribute to the understanding of this protein's role in the development and progression of a wide variety of diseases.

Gene expression variations in microsatellite stable and unstable colon cancer cells

BACKGROUND

Microsatellite instability (MSI) is a marker of chemoresistance, but it is associated with improved survival compared with microsatellite-stable (MSS) colon cancers. We hypothesized that MSI tumors overexpress chemoresistance-associated genes and underexpress DNA damage/repair genes. We used ultra high-throughput sequencing (UHTS) to assess the expression of representative genes in MSI and MSS colon cancer cell lines.

METHODS

Solexa UHTS was used to examine gene expression in HCT116 (MSI) and HT29 (MSS) cells, and normal colonic mucosa (NCM). We compared expression of 40 genes involved in chemoresistance, DNA repair, DNA damage, and drug metabolism pathways.

RESULTS

We observed gene expression differences between MSI and MSS cell lines in 8 out of 40 genes involved in mismatch repair (MMR), DNA repair, drug metabolism, and chemoresistance. MMR gene expression was lower in MSI cells, which is consistent with the MSI phenotype, whereas DNA repair genes were highly expressed in these cells. Genes associated with chemoresistance and drug metabolism also had increased expression in MSI cells. No difference in expression of DNA damage genes was observed between MSI and MSS cell lines.

CONCLUSION

Using UHTS gene expression analysis, we identified differential expression of genes between MSI and MSS cell lines which may account for resistance to chemotherapy in MSI tumors. UHTS expression analysis has the potential to identify genome-wide predictors of response or resistance to chemotherapy.

Epistatic interactions between loci of one-carbon metabolism modulate susceptibility to breast cancer

In view of growing body of evidence substantiating the role of aberrations in one-carbon metabolism in the pathophysiology of breast cancer and lack of studies on gene-gene interactions, we investigated the role of dietary micronutrients and eight functional polymorphisms of one-carbon metabolism in modulating the breast cancer risk in 244 case-control pairs of Indian women and explored possible gene-gene interactions using Multifactor dimensionality reduction analysis (MDR). Dietary micronutrient status was assessed using the validated Food Frequency Questionnaire. Genotyping was done for glutamate carboxypeptidase II (GCPII) C1561T, reduced folate carrier (RFC)1 G80A, cytosolic serine hydroxymethyltransferase (cSHMT) C1420T, thymidylate synthase (TYMS) 5'-UTR tandem repeat, TYMS 3'-UTR ins6/del6, methylenetetrahydrofolate reductase (MTHFR) C677T, methyltetrahydrofolate-homocysteine methyltransferase (MTR) A2756G, methyltetrahydrofolate-homocysteine methyltransferase reductase (MTRR) A66G polymorphisms by using the PCR-RFLP/AFLP methods. Low dietary folate intake (P < 0.001), RFC1 G80A (OR: 1.38, 95% CI 1.06-1.81) and MTHFR C677T (OR: 1.74 (1.11-2.73) were independently associated with the breast cancer risk whereas cSHMT C1420T conferred protection (OR: 0.72, 95% CI 0.55-0.94). MDR analysis demonstrated a significant tri-variate interaction among RFC1 80, MTHFR 677 and TYMS 5'-UTR loci (P (trend) < 0.02) with high-risk genotype combination showing inflated risk for breast cancer (OR 4.65, 95% CI 1.77-12.24). To conclude, dietary as well as genetic factors were found to influence susceptibility to breast cancer. Further, the current study highlighted the importance of multi-loci analyses over the single-locus analysis towards establishing the epistatic interactions between loci of one-carbon metabolism modulate susceptibility to the breast cancer.

Nanomedicine and personalized medicine toward the application of pharmacotyping in clinical practice to improve drug-delivery outcomes

Recent technological advances in nanomedicine and nanotechnology in parallel with knowledge accumulated from the clinical translation of disease- and drug-related genomic data have created fertile ground for personalized medicine to emerge as the new direction in diagnosis and drug therapy. To this end, the development of sophisticated nano-based systems for targeted drug delivery, along with the advent of pharmacogenomics, moves the drug-prescription process toward pharmacotyping, e.g., the individualized adjustment of drug selection and dosage. However, the clinical validity and utility of pharmacogenomic testing must be demonstrated by cost-effectiveness analysis and establishment of clinical-practice reimbursement codes. Within this framework, and to achieve major benefits for all patients worldwide, a multidisciplinary scientific and technological infrastructure has to be organized in the healthcare system to address better the issues affecting regulatory environment, clinical pharmacology guidelines, education, bioethics and genomics data dissemination.

FROM THE CLINICAL EDITOR

Individualized pharmacotyping, patient and disease-specific delivery of drugs, combining nanotechnology and pharmagenomics-based approaches would result in much more specific and efficient treatment of a variety of illnesses. While this clearly is one of the main cornerstones of individualized medicine; the cost effective integration of this complex technology is far from trivial, as discussed in details in this opinion paper.

Proteomics in asthma

Proteomic approaches have already been successfully implemented in areas such as cancer research. Surprisingly, only a few proteomics analyses have been published reporting on the protein profiles associated with asthma. Although proteomics has its limitations and experimental challenges, it can successfully contribute to the understanding of a complex disease such as asthma. We have reviewed the current literature that has reported the use of proteomic techniques to identify proteins that may contribute to altered lung function in asthma. Only a few of these studies have used proteomic techniques on human tissues associated with asthma, while most research has been performed with animal models of asthma. Proteomic applications have been used as a complimentary technique to verify the suspected candidate proteins involved in asthma. In addition, novel proteins have been identified as potential therapeutic targets. Future collaboration between the different scientific disciplines using proteomic studies of animal models of asthma and confirmation of these findings in human tissues will significantly contribute to the understanding of the etiology of asthma and lead to the development of new therapeutic strategies for this highly prevalent disease.

Neuronal signaling modulates protein homeostasis in Caenorhabditis elegans post-synaptic muscle cells

Protein homeostasis maintains proper intracellular balance by promoting protein folding and clearance mechanisms while minimizing the stress caused by the accumulation of misfolded and damaged proteins. Chronic expression of aggregation-prone proteins is deleterious to the cell and has been linked to a wide range of conformational disorders. The molecular response to misfolded proteins is highly conserved and generally studied as a cell-autonomous process. Here, we provide evidence that neuronal signaling is an important modulator of protein homeostasis in post-synaptic muscle cells. In a forward genetic screen in Caenorhabditis elegans for enhancers of polyglutamine aggregation in muscle cells, we identified unc-30, a neuron-specific transcription factor that regulates the synthesis of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). We used additional sensors of protein conformational states to show that defective GABA signaling or increased acetylcholine (ACh) signaling causes a general imbalance in protein homeostasis in post-synaptic muscle cells. Moreover, exposure to GABA antagonists or ACh agonists has a similar effect, which reveals that toxins that act at the neuromuscular junction are potent modifiers of protein conformational disorders. These results demonstrate the importance of intercellular communication in intracellular homeostasis.

Potential role of pharmacogenetics in anti-TNF treatment of rheumatoid arthritis and Crohn's disease

Etanercept, infliximab and adalimumab have shown clinical benefit in immune-mediated inflammatory diseases; however, the outcome of treatment with these tumour-necrosis factor inhibitors remains insufficient in approximately 40-60% and approximately 25-40% of individuals with rheumatoid arthritis and Crohn's disease, respectively. Moreover, their use is accompanied by adverse events and unintentional immune suppression. Pharmacogenetics has the potential to increase efficacy and ameliorate adverse events and immune suppression, and its application might be of clinical benefit for patients with rheumatoid arthritis and Crohn's disease. Pharmacogenetic studies have shown associations between single nucleotide polymorphisms in genes encoding enzymes related to the pharmacodynamics of these drugs and treatment outcome. As we discuss here, replication and prospective validation are warranted before pharmacogenetics can be used in clinical practice.

Improving pharmacotherapy outcomes by pharmacogenomics: from expectation to reality?

The genomic era is now a reality and the extraction of genomic information with a practical value in healthcare represents the next challenge following the completion of the Human Genome Project. To this end, the first pharmacogenomics test approved by the US Food & Drug Administration for assessing cytochrome P450 (CYP)2D6 and CYP2C19 genotype in the implementation of pharmacotherapy decisions in patients, is expected to improve pharmaceutical care outcomes, at least for drugs that are substrates or inhibitors of these enzymes. Furthermore, the progress already achieved and the experience gained in the fields of pharmacogenomics and personalized medicine has clearly demonstrated that an interdisciplinary approach could better serve the target of improving pharmacotherapy outcomes in routine clinical practice. Such an approach will obviously move drug prescription towards pharmacotyping, a stage where the drug selection and dosage process carried out by medical practitioners for any given patient will be advanced by genomic knowledge and information.