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Tong YK, Jin S, Chiu RWK, Ding C, Chan KCA, Leung TY, Yu L, Lau TK, Lo YMD. Noninvasive prenatal detection of trisomy 21 by an epigenetic-genetic chromosome-dosage approach. Clin Chem 2009; 56:90-8. [PMID: 19850629 DOI: 10.1373/clinchem.2009.134114] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
BACKGROUND The use of fetal DNA in maternal plasma for noninvasive prenatal diagnosis of trisomy 21 (T21) is an actively researched area. We propose a novel method of T21 detection that combines fetal-specific epigenetic and genetic markers. METHODS We used combined bisulfite restriction analysis to search for fetal DNA markers on chromosome 21 that were differentially methylated in the placenta and maternal blood cells and confirmed any target locus with bisulfite sequencing. We then used methylation-sensitive restriction endonuclease digestion followed by microfluidics digital PCR analysis to investigate the identified marker. Chromosome-dosage analysis was performed by comparing the dosage of this epigenetic marker with that of the ZFY (zinc finger protein, Y-linked) gene on chromosome Y. RESULTS The putative promoter of the HLCS (holocarboxylase synthetase) gene was hypermethylated in the placenta and hypomethylated in maternal blood cells. A chromosome-dosage comparison of the hypermethylated HLCS and ZFY loci could distinguish samples of T21 and euploid placental DNA. Twenty-four maternal plasma samples from euploid pregnancies and 5 maternal plasma samples from T21 pregnancies were analyzed. All but 1 of the euploid samples were correctly classified. CONCLUSIONS The epigenetic-genetic chromosome-dosage approach is a new method for noninvasive prenatal detection of T21. The epigenetic part of the analysis can be applied to all pregnancies. Because the genetic part of the analysis uses paternally inherited, fetal-specific genetic markers that are abundant in the genome, broad population coverage should be readily achievable. This approach has the potential to become a generally usable technique for noninvasive prenatal diagnosis.
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Chan RWY, Wong J, Chan HLY, Mok TSK, Lo WYW, Lee V, To KF, Lai PBS, Rainer TH, Lo YMD, Chiu RWK. Aberrant concentrations of liver-derived plasma albumin mRNA in liver pathologies. Clin Chem 2009; 56:82-9. [PMID: 19833836 DOI: 10.1373/clinchem.2009.133355] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
BACKGROUND We hypothesized that liver-derived mRNA, such as ALB (albumin) mRNA, would be released into human plasma with liver cell death. METHODS We genotyped ALB mRNA molecules in samples of plasma and whole blood from liver and bone marrow transplant recipients by RNA single-nucleotide polymorphism analysis. Plasma and whole blood ALB mRNA genotypes were compared with the DNA genotypes of the recipients and donors. A reverse-transcription quantitative real-time PCR assay was used to measure plasma ALB mRNA concentrations in 107 patients [hepatocellular carcinoma (HCC), cirrhosis, or chronic hepatitis B (CHB)] and 207 healthy controls. RESULTS The RNA genotype data revealed ALB mRNA in plasma to be liver derived, whereas tissue compartments other than the liver also contributed to the ALB mRNA detected in whole blood. Statistically significant increases in plasma ALB mRNA concentrations were observed for HCC, cirrhosis, and active CHB, compared with controls. A cutoff of 835 copies/mL of plasma ALB mRNA identified by ROC curve analysis showed 85.5% diagnostic sensitivity and 92.8% diagnostic specificity for the detection of liver pathologies. Only 21.5% of patients with liver pathologies had increased alanine aminotransferase (ALT) activities, whereas 73.8% had increased plasma ALB mRNA concentrations. Only 48.6% of the HCC patients had increased serum alpha-fetoprotein concentrations, whereas 91.4% had increased plasma ALB mRNA concentrations. CONCLUSIONS ALB mRNA is liver specific in plasma, but not in whole blood. Plasma ALB mRNA is increased in some liver pathologies and may be more diagnostically sensitive than alpha-fetoprotein and ALT.
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Pang WWI, Tsui MHY, Sahota D, Leung TY, Lau TK, Lo YMD, Chiu RWK. A strategy for identifying circulating placental RNA markers for fetal growth assessment. Prenat Diagn 2009; 29:495-504. [PMID: 19226523 DOI: 10.1002/pd.2230] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE To evaluate whether circulating placental mRNAs in maternal plasma could serve as markers for the assessment of fetal growth or intrauterine growth restriction (IUGR). METHODS From a panel of placental transcripts detectable in maternal plasma identified by microarray previously, we chose growth-related transcripts, namely CSH1, GH2, KISS1, and ADAM12, as potential growth markers. Relationships between the maternal plasma mRNA concentrations with several fetal growth indicators were studied. Maternal plasma mRNA concentrations from IUGR pregnancies with or without pre-eclampsia (PET) were compared with gestational age matched controls cross-sectionally and longitudinally. The four transcripts were quantified by one-step real-time RT-PCR. RESULTS Maternal plasma GH2 mRNA significantly correlated with birth weight and fetal biometric measurements. Maternal plasma ADAM12 mRNA concentration was significantly higher in IUGR with PET than normal pregnancies in the cross-sectional comparison. No significant difference was observed for all markers between IUGR without PET and controls in both the cross-sectional and longitudinal comparisons. CONCLUSION This study presents a potential strategy in identifying surrogate markers for the study of fetal growth. Circulating GH2 mRNA in maternal plasma appeared to be associated with fetal growth. The utility of this strategy and the currently assessed markers could be explored in further studies.
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Hung ECW, Chiu RWK, Lo YMD. Detection of circulating fetal nucleic acids: a review of methods and applications. J Clin Pathol 2009; 62:308-13. [PMID: 19329710 DOI: 10.1136/jcp.2007.048470] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
The discovery of cell-free circulating fetal nucleic acids in maternal plasma has opened up new possibilities in non-invasive prenatal diagnosis. The rapid advancement of this field in the past decade is catalysed by the discovery of new classes of fetal nucleic acid markers and technological developments in nucleic acid detection and amplification. In this review, some of the more significant recent developments in this field will be discussed, including the detection of single molecule, chromosomal aneuploidies, single nucleotide variations and placental microRNAs in maternal plasma.
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Heung MMS, Jin S, Tsui NBY, Ding C, Leung TY, Lau TK, Chiu RWK, Lo YMD. Placenta-derived fetal specific mRNA is more readily detectable in maternal plasma than in whole blood. PLoS One 2009; 4:e5858. [PMID: 19516908 PMCID: PMC2690655 DOI: 10.1371/journal.pone.0005858] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2009] [Accepted: 05/06/2009] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Placental mRNA was detected in maternal whole blood, raising the possibility of using maternal blood for noninvasive prenatal diagnosis. We investigated fetal mRNA detection in maternal whole blood and determined if it offered advantages over maternal plasma analysis. METHODOLOGY The concentrations of placental expressed genes, CSH1, KISS1, PLAC4 and PLAC1 in plasma and whole blood from healthy pregnant and non-pregnant individuals were compared by real-time quantitative reverse-transcriptase polymerase chain reaction analysis. Their fetal specificity was investigated by comparing the transcript concentrations in pre- and post-delivery samples and through SNP genotyping by matrix-assisted laser-desorption and ionization time-of-flight mass spectrometry. The gene expression profiles of pregnant and non-pregnant whole blood were investigated by microarray analysis. Upregulated genes in pregnant whole blood were selected for further quantitative analysis. PRINCIPAL FINDINGS The concentrations of the four transcripts were significantly higher in third trimester maternal whole blood than corresponding plasma without significant correlations. KISS1, PLAC4 and PLAC1 were detected in non-pregnant whole blood but not plasma. The transcripts remained detectable in some postpartum whole blood samples. The PLAC4 mRNA in maternal plasma showed fetal genotype while that in corresponding whole blood indicated both fetal and maternal contributions. Microarray analysis revealed upregulation of genes involved in neutrophil functions in pregnant whole blood including DEFA4, CEACAM8, OLFM4, ORM1, MMP8 and MPO. Though possibly pregnancy-related, they were not pregnancy-specific as suggested by the lack of post-delivery reduction in concentrations. CONCLUSIONS Maternal plasma is preferred over maternal whole blood for placenta-derived fetal RNA detection. Most studied 'placental' mRNA molecules in maternal whole blood were of maternal origin and might be derived from processes such as 'illegitimate transcription'.
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Heung MMS, Tsui NBY, Leung TY, Lau TK, Lo YMD, Chiu RWK. Development of extraction protocols to improve the yield for fetal RNA in maternal plasma. Prenat Diagn 2009; 29:277-9. [PMID: 19165816 DOI: 10.1002/pd.2191] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Hung ECW, Shing TKF, Chim SSC, Yeung PC, Chan RWY, Chik KW, Lee V, Tsui NBY, Li CK, Wong CSC, Chiu RWK, Lo YMD. Presence of Donor-Derived DNA and Cells in the Urine of Sex-Mismatched Hematopoietic Stem Cell Transplant Recipients: Implication for the Transrenal Hypothesis. Clin Chem 2009; 55:715-22. [DOI: 10.1373/clinchem.2008.113530] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Abstract
Background: The term “transrenal DNA” was coined in 2000 to signify that DNA in urine may come from the passage of plasma DNA through the kidney barrier. Although DNA in the urine has the potential to provide a completely noninvasive source of nucleic acids for molecular diagnosis, its existence remains controversial.
Methods: We obtained blood and urine samples from 22 hematopoietic stem cell transplant (HSCT) recipients and used fluorescence in situ hybridization, PCR for short tandem repeats, mass spectrometry, quantitative PCR, and immunofluorescence detection to study donor-derived DNA in the urine.
Results: All HSCT recipients exhibited high amounts of donor-derived DNA in buffy coat and plasma samples. Male donor–derived DNA was detected in supernatants of urine samples from all 5 female sex-mismatched HSCT recipients. Surprisingly, the amount of DNA in urine supernatants was not correlated with the plasma value. Moreover, cell-free urine supernatants contained DNA fragments >350 bp that were absent in plasma. Donor-derived polymorphs were detected in urine by fluorescence in situ hybridization. Coincidentally, donor-derived cytokeratin-producing epithelial cells were discovered in urine samples from 3 of 10 sex-mismatched HSCT recipients as long as 14.2 years after transplantation.
Conclusions: This report is the first to demonstrate the presence of donor-derived DNA in the urine of HSCT recipients; however, we show that much of this DNA originates from donor-derived cells, rather than from the transrenal passage of cell-free plasma DNA. Our discovery of donor-derived cytokeratin-producing epithelial cells raises interesting biological and therapeutic implications, e.g., the capacity of marrow stem cells to serve as an extrarenal source for renal tubule regeneration.
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Lo YMD. Noninvasive prenatal detection of fetal chromosomal aneuploidies by maternal plasma nucleic acid analysis: a review of the current state of the art. BJOG 2009; 116:152-7. [PMID: 19076946 DOI: 10.1111/j.1471-0528.2008.02010.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Fetal nucleic acids in maternal plasma have opened up new possibilities for noninvasive prenatal diagnosis of chromosomal aneuploidies. One approach is based on the measurement of the allelic ratio of single nucleotide polymorphisms in the coding region of placental mRNA. Another approach is through the analysis of DNA fragments with different patterns of DNA methylation between fetal and maternal DNA. One other alternative is to enrich the fractional concentration of fetal DNA in maternal plasma using physical or chemical methods. Finally, the development of more precise digital polymerase chain reaction-based methods for fetal nucleic acid analysis might further catalyse the developments in this area. It is hoped that plasma-based molecular prenatal diagnosis might ultimately make prenatal testing safer for pregnant women and their fetuses.
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Yung TKF, Chan KCA, Mok TSK, Tong J, To KF, Lo YMD. Single-molecule detection of epidermal growth factor receptor mutations in plasma by microfluidics digital PCR in non-small cell lung cancer patients. Clin Cancer Res 2009; 15:2076-84. [PMID: 19276259 DOI: 10.1158/1078-0432.ccr-08-2622] [Citation(s) in RCA: 332] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE We aim to develop a digital PCR-based method for the quantitative detection of the two common epidermal growth factor receptor (EGFR) mutations (in-frame deletion at exon 19 and L858R at exon 21) in the plasma and tumor tissues of patients suffering from non-small cell lung cancers. These two mutations account for >85% of clinically important EGFR mutations associated with responsiveness to tyrosine kinase inhibitors. EXPERIMENTAL DESIGN DNA samples were analyzed using a microfluidics system that simultaneously performed 9,180 PCRs at nanoliter scale. A single-mutant DNA molecule in a clinical specimen could be detected and the quantities of mutant and wild-type sequences were precisely determined. RESULTS Exon 19 deletion and L858R mutation were detectable in 6 (17%) and 9 (26%) of 35 pretreatment plasma samples, respectively. When compared with the sequencing results of the tumor samples, the sensitivity and specificity of plasma EGFR mutation analysis were 92% and 100%, respectively. The plasma concentration of the mutant sequences correlated well with the clinical response. Decreased concentration was observed in all patients with partial or complete clinical remission, whereas persistence of mutation was observed in a patient with cancer progression. In one patient, tyrosine kinase inhibitor was stopped after an initial response and the tumor-associated EGFR mutation reemerged 4 weeks after stopping treatment. CONCLUSION The sensitive detection and accurate quantification of low abundance EGFR mutations in tumor tissues and plasma by microfluidics digital PCR would be useful for predicting treatment response, monitoring disease progression and early detection of treatment failure associated with acquired drug resistance.
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Lo YMD, Chiu RWK. Next-generation sequencing of plasma/serum DNA: an emerging research and molecular diagnostic tool. Clin Chem 2009; 55:607-8. [PMID: 19233905 DOI: 10.1373/clinchem.2009.123661] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Chan KCA, Leung SF, Yeung SW, Chan ATC, Lo YMD. Quantitative analysis of the transrenal excretion of circulating EBV DNA in nasopharyngeal carcinoma patients. Clin Cancer Res 2008; 14:4809-13. [PMID: 18676752 DOI: 10.1158/1078-0432.ccr-08-1112] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE The existence of transrenal clearance of circulating cell-free DNA is controversial. In this study, we used NPC as a model to investigate if circulating EBV DNA can be excreted into urine and to quantify the contribution of renal excretion to the clearance of plasma EBV DNA. EXPERIMENTAL DESIGN Quantitative analysis of urine EBV DNA was done for 74 NPC patients using real-time PCR with two different amplicon sizes. The urine concentration of EBV DNA was expressed as copies per millimole of creatinine (copies/mmol Cr) to minimize the effects of interindividual variations in hydration status. RESULTS EBV DNA was detectable in the urine of 56% NPC patients using a 59-bp real-time PCR assay. The median urine EBV DNA concentrations measured by the 59- and 76-bp assays were 7,040 and 290 copies/mmol Cr, respectively. Patients with detectable urine EBV DNA had significantly higher plasma concentrations, with a positive correlation between the plasma and urine concentrations of EBV DNA. The fraction of plasma EBV DNA excreted into the urine was 0.0026% of that for creatinine. CONCLUSIONS We have shown that circulating EBV DNA can be excreted transrenally into urine in NPC patient and the fraction of excretion is negatively associated with the size of the DNA molecules. Because there is a positive correlation between plasma and urine EBV DNA concentration, urine EBV DNA analysis may potentially be applicable as an ultra-noninvasive test for the monitoring and prognostication of NPC patients.
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Lun FMF, Chiu RWK, Chan KCA, Leung TY, Lau TK, Lo YMD. Microfluidics digital PCR reveals a higher than expected fraction of fetal DNA in maternal plasma. Clin Chem 2008; 54:1664-72. [PMID: 18703764 DOI: 10.1373/clinchem.2008.111385] [Citation(s) in RCA: 348] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
BACKGROUND The precise measurement of cell-free fetal DNA in maternal plasma facilitates noninvasive prenatal diagnosis of fetal chromosomal aneuploidies and other applications. We tested the hypothesis that microfluidics digital PCR, in which individual fetal-DNA molecules are counted, could enhance the precision of measuring circulating fetal DNA. METHODS We first determined whether microfluidics digital PCR, real-time PCR, and mass spectrometry produced different estimates of male-DNA concentrations in artificial mixtures of male and female DNA. We then focused on comparing the imprecision of microfluidics digital PCR with that of a well-established nondigital PCR assay for measuring male fetal DNA in maternal plasma. RESULTS Of the tested platforms, microfluidics digital PCR demonstrated the least quantitative bias for measuring the fractional concentration of male DNA. This assay had a lower imprecision and higher clinical sensitivity compared with nondigital real-time PCR. With the ZFY/ZFX assay on the microfluidics digital PCR platform, the median fractional concentration of fetal DNA in maternal plasma was > or =2 times higher for all 3 trimesters of pregnancy than previously reported. CONCLUSIONS Microfluidics digital PCR represents an improvement over previous methods for quantifying fetal DNA in maternal plasma, enabling diagnostic and research applications requiring precise quantification. This approach may also impact other diagnostic applications of plasma nucleic acids, e.g., in oncology and transplantation.
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Lei KIK, Chan LY, Chan WY, Johnson PJ, Lo YMD. Quantitative analysis of circulating cell-free Epstein-Barr virus (EBV) DNA levels in patients with EBV-associated lymphoid malignancies. Br J Haematol 2008. [DOI: 10.1111/j.1365-2141.2000.02344.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Chan KCA, Leung SF, Yeung SW, Chan ATC, Lo YMD. Persistent aberrations in circulating DNA integrity after radiotherapy are associated with poor prognosis in nasopharyngeal carcinoma patients. Clin Cancer Res 2008; 14:4141-5. [PMID: 18593992 DOI: 10.1158/1078-0432.ccr-08-0182] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE Aberrations of circulating nucleic acid integrity have been observed in cancer patients. However, the clinical significance of such changes has not been completely elucidated. In this study, we investigated the plasma DNA integrity in nasopharyngeal carcinoma (NPC) patients and its association with patients' survival after radiotherapy. EXPERIMENTAL DESIGN Plasma DNA integrity was analyzed for 105 NPC patients before and after curative-intent radiotherapy and for 40 healthy controls. The plasma DNA concentration of each sample was measured by two real-time PCRs targeting the leptin gene. The amplicon sizes of the two assays were 105 and 201 bp. The integrity index was calculated as the ratio of the two concentrations (201 bp/105 bp). More intact circulating DNA would give a higher integrity index. RESULTS The plasma DNA integrity index of the NPC patients was significantly higher than that of the healthy controls (median, 0.356 versus 0.238; P < 0.001). After radiotherapy, a reduction in plasma DNA integrity index was observed in 70% NPC patients. Patients with persistent aberrations of plasma DNA integrity had significantly poorer survival probability than those with reduced DNA integrity after treatment (P < 0.001, Kaplan-Meier). CONCLUSIONS NPC is associated with disturbances in the integrity of circulating cell-free DNA. The persistence of DNA integrity aberrations after radiotherapy is associated with reduced probability of disease-free survival. Therefore, the measurement of plasma DNA integrity may serve as a useful marker for the detection and monitoring of malignant diseases.
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Chan KCA, Lai PBS, Mok TSK, Chan HLY, Ding C, Yeung SW, Lo YMD. Quantitative analysis of circulating methylated DNA as a biomarker for hepatocellular carcinoma. Clin Chem 2008; 54:1528-36. [PMID: 18653827 DOI: 10.1373/clinchem.2008.104653] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND Hypermethylation of the RASSF1A [Ras association (RalGDS/AF-6) domain family member 1A] gene is frequently observed in hepatocellular carcinoma (HCC). We evaluated the analysis of circulating hypermethylated RASSF1A for detecting HCC and assessing its prognosis. METHODS In module 1, we studied 63 pairs of HCC patients and age- and sex-matched chronic hepatitis B virus (HBV) carriers, as well as 50 healthy volunteers. In module 2, we studied 22 HCC patients with cancer detected through a surveillance program. The concentrations of circulating hypermethylated RASSF1A sequences were measured by real-time PCR after digestion with a methylation-sensitive restriction enzyme. RESULTS We detected hypermethylated RASSF1A sequences in the sera of 93% of HCC patients, 58% of HBV carriers, and 8% of the healthy volunteers. The median RASSF1A concentrations for the HCC patients and HBV carriers were 7.70 x 10(5) copies/L and 1.18 x 10(5) copies/L, respectively (P < 0.01). The detection of low concentrations in HBV carriers is consistent with previous findings that RASSF1A hypermethylation is an early event in HCC pathogenesis and can be found in premalignant liver tissues. Use of a marker cutoff value of 1 x 10(6) copies/L also identifies 50% of alpha-fetoprotein-negative HCC cases. Patients with higher RASSF1A concentrations at diagnosis or 1 year after tumor resection showed poorer disease-free survival (P < 0.01). For the HBV carriers who underwent HCC surveillance and subsequently developed HCC, the circulating concentration of RASSF1A increased significantly from the time of enrollment to cancer diagnosis (P = 0.014). CONCLUSIONS Detection and quantification of circulating methylated RASSF1A sequences are useful for HCC screening, detection, and prognostication.
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Tsui DWY, Chan KCA, Chim SSC, Chan LW, Leung TY, Lau TK, Lo YMD, Chiu RWK. Quantitative aberrations of hypermethylated RASSF1A gene sequences in maternal plasma in pre-eclampsia. Prenat Diagn 2008; 27:1212-8. [PMID: 17994635 DOI: 10.1002/pd.1897] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
OBJECTIVE To study if quantitative aberrations in circulating placental-derived hypermethylated RASSF1A DNA in maternal plasma are associated with pre-eclamptic pregnancies. METHOD Maternal plasma and placental tissues from third-trimester pre-eclamptic women and gestational-age matched normotensive controls were studied. Real-time PCR was performed to quantify RASSF1A concentrations before and after methylation-sensitive restriction digestion in a duplex assay, where ss-actin concentrations were quantified as an internal control to confirm complete enzyme digestion. RESULTS The median concentrations of hypermethylated RASSF1A were 4.3-fold higher in maternal plasma of pre-eclamptic subjects than in controls. There was no significant difference between the extent of RASSF1A hypermethylation in placental tissues obtained from pre-eclamptic and control pregnancies. CONCLUSION This study demonstrated the potential utility of hypermethylated RASSF1A sequences in maternal plasma as a gender- and polymorphism-independent marker for pre-eclampsia.
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Chim SSC, Shing TKF, Hung ECW, Leung TY, Lau TK, Chiu RWK, Lo YMD. Detection and characterization of placental microRNAs in maternal plasma. Clin Chem 2008; 54:482-90. [PMID: 18218722 DOI: 10.1373/clinchem.2007.097972] [Citation(s) in RCA: 630] [Impact Index Per Article: 39.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND The discovery of circulating fetal nucleic acids in maternal plasma has opened up new possibilities for noninvasive prenatal diagnosis. MicroRNAs (miRNAs), a class of small RNAs, have been intensely investigated recently because of their important regulatory role in gene expression. Because nucleic acids of placental origin are released into maternal plasma, we hypothesized that miRNAs produced by the placenta would also be released into maternal plasma. METHODS We systematically searched for placental miRNAs in maternal plasma to identify miRNAs that were at high concentrations in placentas compared with maternal blood cells and then investigated the stability and filterability of this novel class of pregnancy-associated markers in maternal plasma. RESULTS In a panel of TaqMan MicroRNA Assays available for 157 well-established miRNAs, 17 occurred at concentrations >10-fold higher in the placentas than in maternal blood cells and were undetectable in postdelivery maternal plasma. The 4 most abundant of these placental miRNAs (miR-141, miR-149, miR-299-5p, and miR-135b) were detectable in maternal plasma during pregnancy and showed reduced detection rates in postdelivery plasma. The plasma concentration of miR-141 increased as pregnancy progressed into the third trimester. Compared with mRNA encoded by CSH1 [chorionic somatomammotropin hormone 1 (placental lactogen)], miR-141 was even more stable in maternal plasma, and its concentration did not decrease after filtration. CONCLUSION We have demonstrated the existence of placental miRNAs in maternal plasma and provide some information on their stability and physical nature. These findings open up a new class of molecular markers for pregnancy monitoring.
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Chim SSC, Jin S, Lee TYH, Lun FMF, Lee WS, Chan LYS, Jin Y, Yang N, Tong YK, Leung TY, Lau TK, Ding C, Chiu RWK, Lo YMD. Systematic search for placental DNA-methylation markers on chromosome 21: toward a maternal plasma-based epigenetic test for fetal trisomy 21. Clin Chem 2008; 54:500-11. [PMID: 18202156 DOI: 10.1373/clinchem.2007.098731] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND The presence of fetal DNA in maternal plasma represents a source of fetal genetic material for noninvasive prenatal diagnosis; however, the coexisting background maternal DNA complicates the analysis of aneuploidy in such fetal DNA. Recently, the SERPINB5 gene on chromosome 18 was shown to exhibit different DNA-methylation patterns in the placenta and maternal blood cells, and the allelic ratio for placenta-derived hypomethylated SERPINB5 in maternal plasma was further shown to be useful for noninvasive detection of fetal trisomy 18. METHODS To develop a similar method for the noninvasive detection of trisomy 21, we used methylation-sensitive single nucleotide primer extension and/or bisulfite sequencing to systematically search 114 CpG islands (CGIs)-76% of the 149 CGIs on chromosome 21 identified by bioinformatic criteria-for differentially methylated DNA patterns. The methylation index (MI) of a CpG site was estimated as the proportion of molecules methylated at that site. RESULTS We identified 22 CGIs which were shown to contain CpG sites that were either completely unmethylated (MI = 0.00) in maternal blood cells and methylated in the placenta (MI range, 0.22-0.65), or completely methylated (MI = 1.00) in maternal blood cells and hypomethylated in the placenta (MI range, 0.00-0.75). We detected, for the first time, placental DNA-methylation patterns on chromosome 21 in maternal plasma during pregnancy and observed their postpartum clearance. CONCLUSION Twenty-two (19%) of the 114 studied CGIs on chromosome 21 showed epigenetic differences between samples of placenta and maternal blood cells; these CGIs may provide a rich source of markers for noninvasive prenatal diagnosis.
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Lo YMD, Chiu RWK. Noninvasive prenatal diagnosis of fetal chromosomal aneuploidies by maternal plasma nucleic acid analysis. Clin Chem 2008; 54:461-6. [PMID: 18202154 DOI: 10.1373/clinchem.2007.100016] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
BACKGROUND The discovery of circulating cell-free fetal nucleic acids in maternal plasma has opened up new possibilities for noninvasive prenatal diagnosis. The potential application of this technology for the noninvasive prenatal detection of fetal chromosomal aneuploidies is an aspect of this field that is being actively investigated. The main challenge of work in this area is the fact that cell-free fetal nucleic acids represent only a minor fraction of the total nucleic acids in maternal plasma. METHODS AND RESULTS We performed a review of the literature, which revealed that investigators have applied methods based on the physical and molecular enrichment of fetal nucleic acid targets from maternal plasma. The former includes the use of size fractionation of plasma DNA and the use of the controversial formaldehyde treatment method. The latter has been achieved through the development of fetal epigenetic and fetal RNA markers. The aneuploidy status of the fetus has been explored through the use of allelic ratio analysis of plasma fetal epigenetic and RNA markers. Digital PCR has been shown to offer high precision for allelic ratio and relative chromosome dosage analyses. CONCLUSIONS After a decade of work, the theoretical and practical feasibility of prenatal fetal chromosomal aneuploidy detection by plasma nucleic acid analysis has been demonstrated in studies using small sample sets. Larger scale independent studies will be needed to validate these initial observations. If these larger scale studies prove successful, it is expected that with further development of new fetal DNA/RNA markers and new analytical methods, molecular noninvasive prenatal diagnosis of the major chromosomal aneuploidies could become a routine practice in the near future.
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Tsui NBY, Lo YMD. A microarray approach for systematic identification of placental-derived RNA markers in maternal plasma. Methods Mol Biol 2008; 444:275-89. [PMID: 18425489 DOI: 10.1007/978-1-59745-066-9_22] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Circulating fetal RNA in maternal plasma has offered a new approach for noninvasive prenatal diagnosis and monitoring. Circulating fetal RNA markers could potentially be used for all pregnant women without being limited by fetal-maternal genetic polymorphisms and fetal gender. Over the past few years, encouraging findings have been reported on the detection and possible clinical applications of circulating fetal RNA. Placental-derived RNA has been shown to be easily detectable in maternal plasma during pregnancy and rapidly cleared after delivery. Such observations suggest that the placenta is an important organ for releasing fetal RNA into maternal plasma. Noninvasive prenatal gene expression profiling of the placenta also has been demonstrated to be feasible by analyzing the circulating placental RNA in maternal plasma. Thus, circulating placental RNA is a potentially useful tool for noninvasive investigation of the placenta. Here, we describe a systematic method for efficient development of new placental-specific RNA markers that could be detected in maternal plasma. The method is based on the use of oligonucleotide microarray (Affymetrix, Santa Clara, CA) technology to simultaneously analyze >39,000 RNA transcripts in the placenta. This development has implication for the development of new markers\break for studying disease conditions associated with placental pathology, such as preeclampsia.
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Wong CK, Wong BCK, Chan KCA, Joynt GM, Yap FYHY, Lam CWK, Lee N, Lee SS, Cockram CS, Sung JJY, Chan PKS, Lo YMD, Tang JW. Cytokine profile in fatal human immunodeficiency virus tuberculosis Epstein-Barr virus associated hemophagocytic syndrome. ACTA ACUST UNITED AC 2007; 167:1901-3. [PMID: 17893313 DOI: 10.1001/archinte.167.17.1901] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Tong YK, Chiu RWK, Leung TY, Ding C, Lau TK, Leung TN, Lo YMD. Detection of restriction enzyme-digested target DNA by PCR amplification using a stem-loop primer: application to the detection of hypomethylated fetal DNA in maternal plasma. Clin Chem 2007; 53:1906-14. [PMID: 17901110 DOI: 10.1373/clinchem.2007.092619] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND The discovery of cell-free fetal DNA in maternal plasma has opened up new possibilities for noninvasive prenatal diagnosis and monitoring. Among the fetal markers that have been described, methylation markers are sex and polymorphism independent. Methylation-sensitive restriction endonucleases are commonly used to digest hypomethylated DNA molecules, and the hypermethylated molecules remain intact for detection. The positive detection of the cleaved hypomethylated molecules would be useful for certain targets but has not been reported. METHODS The use of a stem-loop primer in microRNA detection has previously been described. In this study, DNA assays were designed and performed on maternal plasma, which contained the hypomethylated placental serpin peptidase inhibitor, clade B (ovalbumin), member 5 (SERPINB5; maspin) gene in an excess background of hypermethylated maternal SERPINB5. Detection of the enzyme-digested placenta-derived hypomethylated SERPINB5 molecules was achieved by performing stem-loop extension followed by real-time PCR on maternal plasma. The placental origin of the stem-loop-extended SERPINB5 molecules was confirmed by genotyping. RESULTS From the real-time PCR results on maternal plasma, stem-loop-extended SERPINB5 promoter sequences were detectable in all 11 enzyme-digested predelivery maternal plasma samples. Postpartum clearance was demonstrated. In 9 cases in which the fetal and maternal SERPINB5 genotypes were distinguishable, the placental-specific genotypes were detected in all predelivery maternal plasma samples. CONCLUSION Detection of restriction enzyme-digested hypomethylated placental DNA molecules in maternal plasma by the use of a stem-loop primer represents a novel approach in fetal epigenetic marker detection. The analytical approach may also be generally applicable to the detection of restriction enzyme-digested nucleic acid fragments.
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Abstract
Since the discovery of circulating nucleic acids in plasma in 1948, many diagnostic applications have emerged. For example, diagnostic and prognostic potentials of circulating tumour-derived DNA have been demonstrated for many types of cancer. The parallel development of fetal-derived DNA detection in maternal plasma has opened up the possibility of non-invasive prenatal diagnosis and monitoring of many pregnancy-associated disorders. In this regard, non-invasive fetal rhesus blood group genotyping has already been translated to clinical practice. Other applications of circulating DNA in traumatology and transplant monitoring have also been reported. The more recent discoveries of circulating tumour-derived RNA and fetal-derived RNA have proven to be equally important as their DNA counterparts. Successful prenatal diagnosis of Down's syndrome by fetal RNA analysis has recently been reported. However, the definite origin and release mechanisms of circulating nucleic acids have remained incompletely understood, with cell death being suggested to be associated with such nucleic acid release. Pre-analytical standardisation will become increasingly relevant when comparing data from different laboratories. In conclusion, studies of circulating nucleic acids have promised exciting developments in molecular diagnostics in the years to come.
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Ma B, Hui EP, King A, To KF, Mo F, Leung SF, Kam M, Lo YMD, Zee B, Mok T, Ahuja A, Chan ATC. A phase II study of patients with metastatic or locoregionally recurrent nasopharyngeal carcinoma and evaluation of plasma Epstein-Barr virus DNA as a biomarker of efficacy. Cancer Chemother Pharmacol 2007; 62:59-64. [PMID: 17762933 DOI: 10.1007/s00280-007-0575-8] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2007] [Accepted: 08/07/2007] [Indexed: 11/30/2022]
Abstract
BACKGROUND The epidermal growth factor receptor (EGFR) is commonly overexpressed in nasopharyngeal carcinoma (NPC) and gefitinib inhibits NPC growth in vitro. METHOD Patients who progressed after prior platinum-based chemotherapy for recurrent NPC were given gefitinib orally at 500 mg/day at a 28-day cycle. Plasma Epstein-Barr virus (pEBV) DNA levels were obtained at specific intervals. RESULTS Sixteen patients enrolled and 15 were evaluable for response. The median age was 49 years (range 34-64 years), and most patients were males with metastatic NPC. No objective response was seen and three patients had stable disease (SD) for 2.8 to 8.5 months. Radiological progression of disease coincided with rising levels of pEBV DNA in most patients, while the level of a patient with the longest duration of SD fell to an undetectable level at study completion. The mean time to progression and overall survival was 2.7 (standard error, SE +/- 0.5 months) and 12 months (SE +/- 1.7 months), respectively. No unexpected drug-related toxicities were seen. The study was prematurely terminated because there was insufficient activity to warrant progression to the second stage of accrual. CONCLUSION This study found limited activity of gefitinib in recurrent NPC. Further evaluation of pEBV DNA as a biomarker of response in clinical trials of target-based agents is warranted.
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