Two-color quantitative multiplex methylation-specific PCR

Discovery and technical validation of high-performance methylated DNA markers for the detection of cervical lesions at risk of malignant progression in low- and middle-income countries

BACKGROUND

Cervical cancer remains a leading cause of death, particularly in developing countries. WHO screening guidelines recommend human papilloma virus (HPV) detection as a means to identify women at risk of developing cervical cancer. While HPV testing identifies those at risk, it does not specifically distinguish individuals with neoplasia. We investigated whether a quantitative molecular test that measures methylated DNA markers could identify high-risk lesions in the cervix with accuracy.

RESULTS

Marker discovery was performed in TCGA-CESC Infinium Methylation 450 K Array database and verified in three other public datasets. The panel was technically validated using Quantitative Multiplex-Methylation-Specific PCR in tissue sections (N = 252) and cervical smears (N = 244) from the USA, South Africa, and Vietnam. The gene panel consisted of FMN2, EDNRB, ZNF671, TBXT, and MOS. Cervical tissue samples from all three countries showed highly significant differential methylation in squamous cell carcinoma (SCC) with a sensitivity of 100% [95% CI 74.12-100.00], and specificity of 91% [95% CI 62.26-99.53] to 96% [95% CI 79.01-99.78], and receiver operating characteristic area under the curve (ROC AUC) = 1.000 [95% CI 1.00-1.00] compared to benign cervical tissue, and cervical intraepithelial neoplasia 2/3 with sensitivity of 55% [95% CI 37.77-70.84] to 89% [95% CI 67.20-98.03], specificity of 93% [95% CI 84.07-97.38] to 96% [95% CI 79.01-99.78], and a ROC AUC ranging from 0.793 [95% CI 0.68-0.89] to 0.99 [95% CI 0.97-1.00] compared to CIN1. In cervical smears, the marker panel detected SCC with a sensitivity of 87% [95% CI 77.45-92.69], specificity 95% [95% CI 88.64-98.18], and ROC AUC = 0.925 [95% CI 0.878-0.974] compared to normal, and high-grade squamous intraepithelial lesion (HSIL) at a sensitivity of 70% (95% CI 58.11-80.44), specificity of 94% (95% CI 88.30-97.40), and ROC AUC = 0.884 (95% CI 0.822-0.945) compared to low-grade intraepithelial lesion (LSIL)/normal in an analysis of pooled data from the three countries. Similar to HPV-positive, HPV-negative cervical carcinomas were frequently hypermethylated for these markers.

CONCLUSIONS

This 5-marker panel detected SCC and HSIL in cervical smears with a high level of sensitivity and specificity. Molecular tests with the ability to rapidly detect high-risk HSIL will lead to timely treatment for those in need and prevent unnecessary procedures in women with low-risk lesions throughout the world. Validation of these markers in prospectively collected cervical smear cells followed by the development of a hypermethylated marker-based cervical cancer detection test is warranted.

CDH1 (E-cadherin) Gene Methylation in Human Breast Cancer: Critical Appraisal of a Long and Twisted Story

Simple Summary

Genes can be inactivated by specific modifications of DNA bases, most often by adding a methyl group to the DNA base cytosine if it is followed by guanosine (CG methylation). This modification prevents gene expression and has been reported for many different genes in nearly all types of cancer. A prominent example is the gene CDH1, which encodes the cell-adhesion molecule E-cadherin. This is an important player in the spreading of tumor cells within the body (metastasis). Particularly in human breast cancer, many different research groups have studied the inactivation of the CDH1 gene via DNA methylation using various methods. Over the last 20 years, different, in part, even contradicting results have been published for the CDH1 gene in breast cancer. This review summarizes the most important publications and explains the bewildering heterogeneity of results through careful analysis of the methods which have been used.

Abstract

Epigenetic inactivation of a tumor suppressor gene by aberrant DNA methylation is a well-established defect in human tumor cells, complementing genetic inactivation by mutation (germline or somatic). In human breast cancer, aberrant gene methylation has diagnostic, prognostic, and predictive potential. A prominent example is the hypermethylation of the CDH1 gene, encoding the adhesion protein E-Cadherin (“epithelial cadherin”). In numerous publications, it is reported as frequently affected by gene methylation in human breast cancer. However, over more than two decades of research, contradictory results concerning CDH1 gene methylation in human breast cancer accumulated. Therefore, we review the available evidence for and against the role of DNA methylation of the CDH1 gene in human breast cancer and discuss in detail the methodological reasons for conflicting results, which are of general importance for the analysis of aberrant DNA methylation in human cancer specimens. Since the loss of E-cadherin protein expression is a hallmark of invasive lobular breast cancer (ILBC), special attention is paid to CDH1 gene methylation as a potential mechanism for loss of expression in this special subtype of human breast cancer. Proper understanding of the methodological basis is of utmost importance for the correct interpretation of results supposed to demonstrate the presence and clinical relevance of aberrant DNA methylation in cancer specimens.

A phase 2 trial of gemcitabine and docetaxel in patients with metastatic colorectal adenocarcinoma with methylated checkpoint with forkhead and ring finger domain promoter and/or microsatellite instability phenotype

Abstract

We previously reported CHFR methylation in a subset of colorectal cancer (CRC; ∼30%) with high concordance with microsatellite instability (MSI). We also showed that CHFR methylation predicted for sensitivity to docetaxel, whereas the MSI‐high phenotypes were sensitive to gemcitabine. We hypothesized that this subset of patients with CRC would be selectively sensitive to gemcitabine and docetaxel. We enrolled a Phase 2 trial of gemcitabine and docetaxel in patients with MSI‐high and/or CHFR methylated CRC. The primary objective was Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 response rate. Enrolled patients were treated with gemcitabine 800 mg/m² on days 1 and 8 and docetaxel 70 mg/m² on day 8 of each 21‐day cycle. A total of 6 patients with CHFR‐methylated, MSI‐high CRC were enrolled from September 2012 to August 2016. The study was closed in September of 2017 due to poor accrual prior to reaching the first interim assessment of response rate, which would have occurred at 10 patients. No RECIST criteria tumor responses were observed, with 3 patients (50%) having stable disease as best response, 1 lasting more than 9 months. Median progression‐free survival (PFS) was 1.79 months (95% confidence interval [CI] = 1.28, not available [NA]) and median overall survival (OS) was 15.67 months (95% CI = 4.24, NA). Common grade 3 toxicities were lymphopenia (67%), leukopenia (33%), and anemia (33%). Although negative, this study establishes a proof‐of‐concept for the implementation of epigenetic biomarkers (CHFR methylation/MSI) as inclusion criteria in a prospective clinical trial to optimize combinatorial strategies in the era of personalized medicine.

Quantitation of DNA Methylation by Quantitative Multiplex Methylation-Specific PCR (QM-MSP) Assay

The defining feature of the Quantitative Multiplex Methylation-Specific PCR (QM-MSP) method to sensitively quantify DNA methylation is the two-step PCR approach for a multiplexed analysis of a panel of up to 12 genes in clinical samples with minimal quantities of DNA. In the first step, for up to 12 genes tested, one pair of gene-specific primers (forward and reverse) amplifies the methylated and unmethylated copies of the same gene simultaneously and in multiplex, in one PCR reaction. This methylation-independent amplification step produces amplicons of up to 10⁹ copies per μL after 36 cycles of PCR. In the second step, the amplicons of the first reaction (STEP 1) are quantified with a standard curve using real-time PCR and two independent fluorophores to detect methylated/unmethylated DNA of each gene in the same well (e.g., 6FAM and VIC). One methylated copy is detectable in 100,000 reference gene copies. Methylation is reported on a continuous scale. For the gene panel, the highest level of normal DNA methylation above which a sample would be called positive is derived by using Receiver Operating Characteristic (ROC), maximizing assay specificity and sensitivity to distinguish between normal/benign versus tumor DNA. QM-MSP can be applied to clinical samples of fresh or fixed ductal cells, ductal fluid, nipple fluid, fine needle aspirates, core biopsies, and tumor tissue sections.

Salivary DNA methylation panel to diagnose HPV-positive and HPV-negative head and neck cancers

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) is a heterogeneous group of tumours with a typical 5 year survival rate of <40 %. DNA methylation in tumour-suppressor genes often occurs at an early stage of tumorigenesis, hence DNA methylation can be used as an early tumour biomarker. Saliva is an ideal diagnostic medium to detect early HNSCC tumour activities due to its proximity to tumour site, non-invasiveness and ease of sampling. We test the hypothesis that the surveillance of DNA methylation in five tumour-suppressor genes (RASSF1α, p16 ^INK4a , TIMP3, PCQAP/MED15) will allow us to diagnose HNSCC patients from a normal healthy control group as well as to discriminate between Human Papillomavirus (HPV)-positive and HPV-negative patients.

METHODS

Methylation-specific PCR (MSP) was used to determine the methylation levels of RASSF1α, p16 ^INK4a , TIMP3 and PCQAP/MED15 in DNA isolated from saliva. Statistical analysis was carried out using non-parametric Mann-Whitney's U-test for individually methylated genes. A logistic regression analysis was carried out to determine the assay sensitivity when combing the five genes. Further, a five-fold cross-validation with a bootstrap procedure was carried out to determine how well the panel will perform in a real clinical scenario.

RESULTS

Salivary DNA methylation levels were not affected by age. Salivary DNA methylation levels for RASSF1α, p16 ^INK4a , TIMP3 and PCQAP/MED15 were higher in HPV-negative HNSCC patients (n = 88) compared with a normal healthy control group (n = 122) (sensitivity of 71 % and specificity of 80 %). Conversely, DNA methylation levels for these genes were lower in HPV-positive HNSCC patients (n = 45) compared with a normal healthy control group (sensitivity of 80 % and specificity of 74 %), consistent with the proposed aetiology of HPV-positive HNSCCs.

CONCLUSIONS

Salivary DNA tumour-suppressor methylation gene panel has the potential to detect early-stage tumours in HPV-negative HNSCC patients. HPV infection was found to deregulate the methylation levels in HPV-positive HNSCC patients. Large-scale double-blinded clinical trials are crucial before this panel can potentially be integrated into a clinical setting.

DNA methylation and detection of cervical cancer and precancerous lesions using molecular methods

Cervical cancer is the third most common cancer disease affecting the female population, and a key factor in the development of the disease is the human papillomavirus infection (HPV). The disease is also impacted by epigenetic changes such as DNA methylation, which causes activation or exclusion of certain genes. The aim of our review is to summarize and compare the most common molecular methods for detection of methylated promoter regions in biomarkers occurring in cervical carcinoma and also show the importance of connections of HR-HPV testing with methylation analysis in patients with cervical intraepithelial neoplasia. Insight into genetic and epigenetic alterations associated with cervical cancer development can offer opportunities for the molecular biomarkers that can be useful for screening, diagnosis, and also as new ways of treatment of cervical cancer precursor lesions.

RASSF1A Promoter Methylation Levels Positively Correlate with Estrogen Receptor Expression in Breast Cancer Patients

The aim of this study was to investigate the relationship between the promoter methylation in five cancer-associated genes and clinicopathologic features for identification of molecular markers of tumor metastatic potential and hormone therapy response efficiency in breast cancer. The methylation levels in paraffin-embedded tumor tissues, plasma, and blood cells from 151 sporadic breast cancer patients and blood samples of 50 controls were evaluated by quantitative multiplex methylation-specific polymerase chain reaction. DNA methylation of RAS-association domain family member 1 (RASSF1A), estrogen receptor 1 (ESR1), cadherin 1, type 1, E-cadherin (CDH1), TIMP metallopeptidase inhibitor 3 (TIMP3) and spleen tyrosine kinase (SYK) genes was detected in the tumors of 124, 19, 15, 15, and 6 patients with mean levels of 48.45%, 3.81%, 2.36%, 27.55%, and 10.81%, respectively. Plasma samples exhibited methylation in the same genes in 25, 10, 15, 17, and 3 patients with levels of 22.54%, 17.20%, 22.87%, 31.93%, and 27.42%, respectively. Cumulative methylation results confirmed different spectra in tumor and plasma samples. Simultaneous methylation in tumors and plasma were shown in less than 17% of patients. RASSF1A methylation levels in tumor samples statistically differ according to tumor size (P = .029), estrogen receptor (ER) and progesterone receptor (PR) status (P = .000 and P = .004), and immunohistochemical subtype (P = .000). Moreover, the positive correlation was found between RASSF1A methylation levels and percentage of cancer cells expressing ER and PR. The direct relationship between RASSF1A promoter methylation and expression of ER could aid the prognosis of hormonal therapy response.

Biomarker modulation following short-term vorinostat in women with newly diagnosed primary breast cancer

PURPOSE

Agents that target the epigenome show activity in breast cancer models. In preclinical studies, the histone deacetylase inhibitor vorinostat induces cell-cycle arrest, apoptosis, and differentiation. We evaluated biomarker modulation in breast cancer tissues obtained from women with newly diagnosed invasive disease who received vorinostat and those who did not.

EXPERIMENTAL DESIGN

Tumor specimens were collected from 25 women who received up to 6 doses of oral vorinostat 300 mg twice daily and from 25 untreated controls in a nonrandomized study. Candidate gene expression was analyzed by reverse transcription PCR (RT-PCR) using the Oncotype DX 21-gene assay, and by immunohistochemistry for Ki-67 and cleaved caspase-3. Matched samples from treated women were analyzed for gene methylation by quantitative multiplex methylation-specific PCR (QM-MSP). Wilcoxon nonparametric tests were used to compare changes in quantitative gene expression levels pre- and post-vorinostat with changes in expression in untreated controls, and changes in gene methylation between pre- and post-vorinostat samples.

RESULTS

Vorinostat was well tolerated and there were no study-related delays in treatment. Compared with untreated controls, there were statistically significant decreases in the expression of proliferation-associated genes Ki-67 (P = 0.003), STK15 (P = 0.005), and Cyclin B1 (P = 0.03) following vorinostat, but not in other genes by the Oncotype DX assay, or in expression of Ki-67 or cleaved caspase-3 by immunohistochemistry. Changes in methylation were not observed.

CONCLUSIONS

Short-term vorinostat administration is associated with a significant decrease in expression of proliferation-associated genes in untreated breast cancers. This demonstration of biologic activity supports investigation of vorinostat in combination with other agents for the management of breast cancer.

Recent progress in the study of methylated tumor suppressor genes in gastric cancer

Gastric cancer is one of the most common malignancies and a leading cause of cancer mortality worldwide. The pathogenesis mechanisms of gastric cancer are still not fully clear. Inactivation of tumor suppressor genes and activation of oncogenes caused by genetic and epigenetic alterations are known to play significant roles in carcinogenesis. Accumulating evidence has shown that epigenetic silencing of the tumor suppressor genes, particularly caused by hypermethylation of CpG islands in promoters, is critical to carcinogenesis and metastasis. Here, we review the recent progress in the study of methylations of tumor suppressor genes involved in the pathogenesis of gastric cancer. We also briefly describe the mechanisms that induce tumor suppressor gene methylation and the status of translating these molecular mechanisms into clinical applications.

Genome-wide methylation analysis identifies genes specific to breast cancer hormone receptor status and risk of recurrence

To better understand the biology of hormone receptor-positive and-negative breast cancer and to identify methylated gene markers of disease progression, we carried out a genome-wide methylation array analysis on 103 primary invasive breast cancers and 21 normal breast samples, using the Illumina Infinium HumanMethylation27 array that queried 27,578 CpG loci. Estrogen and/or progesterone receptor-positive tumors displayed more hypermethylated loci than estrogen receptor (ER)-negative tumors. However, the hypermethylated loci in ER-negative tumors were clustered closer to the transcriptional start site compared with ER-positive tumors. An ER-classifier set of CpG loci was identified, which independently partitioned primary tumors into ER subtypes. A total of 40 (32 novel and 8 previously known) CpG loci showed differential methylation specific to either ER-positive or ER-negative tumors. Each of the 40 ER subtype-specific loci was validated in silico, using an independent, publicly available methylome dataset from the Cancer Genome Atlas. In addition, we identified 100 methylated CpG loci that were significantly associated with disease progression; the majority of these loci were informative particularly in ER-negative breast cancer. Overall, the set was highly enriched in homeobox containing genes. This pilot study shows the robustness of the breast cancer methylome and illustrates its potential to stratify and reveal biological differences between ER subtypes of breast cancer. Furthermore, it defines candidate ER-specific markers and identifies potential markers predictive of outcome within ER subgroups.

Methylated genes in breast cancer: associations with clinical and histopathological features in a familial breast cancer cohort

BACKGROUND

Hundreds of hypermethylated genes have been described in breast cancer, yet the nature and contribution of these genes in their methylated state to overall risk and prognosis is under-characterized in non-sporadic breast cancers. We therefore compared associations of DNA methylation with tumor stage, hormone/growth receptor status, and clinical outcomes in a familial breast cancer cohort. Because few previous methylation studies have considered the oncogenic or tumor suppressor properties of their gene sets, this functional status was included as part of our correlative analysis.

RESULTS

We found methylation of oncogenes was associated with better prognostic indicators, whereas tumor suppressor gene methylation was associated with a more severe phenotype in women that were either HER2+ or lymph node positive at diagnosis, and/or tended to recur or develop distant metastases. For example, the methylation of the tumor suppressor gene APC was strongly associated with a specific subset of tumors that were both ER+ and HER2+, while methylation of the TWIST oncogene was associated with breast cancers that did not metastasize.

METHODS

This was a retrospective, hospital-based study of n = 99 archival breast tumors derived from women with a germline genetic BRCA1 or BRCA2 mutation and/or familial breast cancer history. DNA methylation was quantified from formalin fixed, paraffin embedded tumors using the established protocol of quantitative multiplex-methylation specific PCR (QM-MSP). Non-parametric statistics were used to analyze candidate gene methylation in association with clinical outcomes.

CONCLUSION

We report several novel, positive associations between percent methylation of the APC, RASSF1A, TWIST, ERα, CDH1, and Cyclin D2 genes and key variables such as tumor stage, hormone and growth receptor status, and a history of recurrent or metastatic disease. Our data suggest the potential utility of parsing gene methylation by functional status and breast tumor subtype.

Epigenomics and ovarian carcinoma

Ovarian cancer is the leading cause of death among gynecological cancers. It is now recognized that in addition to genetic alterations, epigenetic mechanisms, such as DNA methylation, histone modifications and nucleosome remodeling, play an important role in the development and progression of ovarian cancer by modulating chromatin structure, and gene and miRNA expression. Furthermore, epigenetic alterations have been recognized as useful tools for the development of novel biomarkers for diagnosis, prognosis, therapeutic prediction and monitoring of diseases. Moreover, new epigenetic therapies, such as DNA methyltransferase inhibitors and histone deacetylase inhibitors, have been found to be a potential therapeutic option, especially when used in combination with other agents. Here we discuss current developments in ovarian carcinoma epigenome research, the importance of the ovarian carcinoma epigenome for development of diagnostic and prognostic biomarkers, and the current epigenetic therapies used in ovarian cancer.

Quantitative assessment of DNA methylation for the detection of cervical neoplasia in liquid-based cytology specimens

Previously, we have shown that methylation-specific PCR (MSP) analysis of a key panel of genes may be useful as an ancillary tool for diagnosing squamous cell carcinomas (SCC) and high-grade squamous intraepithelial lesions (HSIL) in cervical scrapings. Because quantitative MSP (QMSP) is more suitable as a screening tool than conventional MSP, we investigated the diagnostic role of QMSP for the detection of SCC and HSIL in cervical scrapings. A quantitative multiplex-MSP approach was used to examine promoter methylation of five genes (APC, HIN-1, RAR-beta, RASSF1A, and Twist) in biopsy-confirmed SCC (n = 63), HSIL (n = 45), low-grade SIL (LSIL, n = 26), and negative (n = 28) liquid-based cytology samples. For four genes (HIN-1, RAR-beta, RASSF1A, and Twist), the methylation levels among four groups were significantly different (p < 0.001 for each). Methylation levels of HIN-1, RAR-beta, RASSF1A, and Twist were increased in HSIL and SCC samples, compared with either negative or LSIL samples. However, methylation levels were not significantly different between SCC and HSIL, with the exception of RASSF1A. Receiver-operating characteristic analysis demonstrated that HIN-1, RAR-beta, RASSF1A, and Twist had the ability to distinguish HSIL/SCC from LSIL/negative samples. The two-gene combination (RASSF1A/Twist) showed the best performance in distinguishing HSIL/SCC from LSIL/negative samples. The estimated specificity of this two-gene panel for detecting HSIL/SCC was 90.7%, and its sensitivity was 74.1%. These results suggest that quantitative detection of aberrant DNA methylation in cervical scrapings may be a promising high-throughput approach for the diagnosis of HSIL/SCC.

MethySYBR, a novel quantitative PCR assay for the dual analysis of DNA methylation and CpG methylation density

Development of facile, sensitive, specific, and economical assays for the analysis of methylated alleles is crucial to the use of methylated biomarkers for cancer detection. We hereby report a novel method, MethySYBR, a SYBR green-based PCR assay for the dual analysis of DNA methylation and CpG methylation density. MethySYBR begins with multiplex PCR to enable the simultaneous amplification of many discrete target alleles in a single reaction using as little as 3 pg of bisulfite-converted DNA. In the second round of PCR, the specific methylated target is quantified from multiplex products using both nested methylation-independent and methylation-specific primer sets. Moreover, the use of SYBR green dye during quantitative PCR enables melting curve analysis of target amplicons to determine the methylation density of CpG sites on target alleles. To establish proof of principle, two cancer-specific methylated genes, RASSF1A and OGDHL, were assessed by MethySYBR. We demonstrated that MethySYBR sensitively detected methylated alleles in the presence of a 100,000-fold excess of unmethylated allele. Furthermore, MethySYBR was shown to be capable of analyzing minute amounts of DNA from paraffin-embedded tissue. Therefore, the MethySYBR assay is a simple, highly specific, highly sensitive, high-throughput, and cost-effective method that is widely applicable to basic and clinical studies of DNA methylation.

Epigenomics and breast cancer

Breast carcinogenesis involves genetic and epigenetic alterations that cause aberrant gene function. Recent progress in the knowledge of epigenomics has had a profound impact on the understanding of mechanisms leading to breast cancer, and consequently the development of new strategies for diagnosis and treatment of breast cancer. Epigenetic regulation has been known to involve three mutually interacting events--DNA methylation, histone modifications and nucleosomal remodeling. These processes modulate chromatin structure to form euchromatin or heterochromatin, and in turn activate or silence gene expression. Alteration in expression of key genes through aberrant epigenetic regulation in breast cells can lead to initiation, promotion and maintenance of carcinogenesis, and is even implicated in the generation of drug resistance. We currently review known roles of the epigenetic machinery in the development and recurrence of breast cancer. Furthermore, we highlight the significance of epigenetic alterations as predictive biomarkers and as new targets of anticancer therapy.

Epigenetic alterations of the dopaminergic system in major psychiatric disorders

Although there is evidence to link schizophrenia (SCZ) and bipolar disorder (BD) to genetic and environmental factors, specific individual or groups of genes/factors causative of the disease have been elusive to the research community. An understanding of the molecular aberrations that cause these mental illnesses requires comprehensive approaches that examine both genetic and epigenetic factors. Because of the overwhelming evidence for the role of environmental factors in the disease presentation, our initial approach involved deciphering how epigenetic changes resulting from promoter DNA methylation affect gene expression in SCZ and BD. Apparently, the central reversible but covalent epigenetic modification to DNA is derived from methylation of the cytosine residues that is potentially heritable and can affect gene expression and downstream activities. Environmental factors can influence DNA methylation patterns and hence alter gene expression. Such changes can be especially problematic in individuals with genetic susceptibilities to specific diseases. Recent reports from our laboratory provided compelling evidence that both hyper- and hypo-DNA methylation changes of the regulatory regions play critical roles in defining the altered functionality of genes in major psychiatric disorders such as SCZ and BD. In this chapter, we outline the technical details of the methods that could help to expand this line of research to assist with compiling the differential methylation-mediated epigenetic alterations that are responsible for the pathogenesis of SCZ, BD, and other mental diseases. We use the genes of the extended dopaminergic (DAergic) system such as membrane-bound catechol-O-methyltransferase (MB-COMT), monoamine oxidase A (MAOA), dopamine transporter 1 (DAT1), tyrosine hydroxylase (TH), dopamine (DA) receptors1 and 2 (DRD1/2), and related genes (e.g., reelin [RELN] and brain-derived neurotrophic factor [BDNF]) to illustrate the associations between differential promoter DNA methylations and disease phenotype. It is our hope that comprehensive analyses of the DAergic system as the prototype could provide the impetus and molecular basis to uncover early markers for diagnosis, help in the understanding of differences in disease severity in individuals with similar or identical genetic makeup, and assist with the identification of novel targets for therapeutic applications.