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Ivy H N Wong

Publications and source records attributed to Ivy H N Wong.

7 recordsLinked to original sources
PubMed2006

Qualitative and quantitative polymerase chain reaction-based methods for DNA methylation analyses.

DNA methylation can be analyzed easily by qualitative or quantitative polymerase chain reaction (PCR)-based methods, including methylation-specific PCR (MSP), bisulfite sequencing, methylation-sensitive restriction enzyme PCR, combined bisulfite restriction analysis (COBRA), methylation-sensitive single nucleotide primer extension (Ms-SNuPE), and quantitative real-time MSP. MSP, which couples the bisulfite modification of DNA and PCR, is fast, highly sensitive, specific, and widely applied for DNA methylation analyses. Bisulfite modification converts unmethylated cytosine to uracil, whereas methylcytosine remains unmodified. Most of these methods require specific PCR primers that are designed to distinguish between methylated and unmethylated DNA sequences. Bisulfite sequencing is comparatively time-consuming. Methylation-sensitive restriction enzyme PCR combines methylation-sensitive restriction enzyme digestion and PCR. After enzyme digestion, PCR products are obtained if the enzyme does not digest the methylated CpG sites within the specified DNA region. COBRA, Ms-SNuPE, and quantitative real-time MSP allow the quantitative analyses of DNA methylation.

DNA↗
PubMed2004

Ubiquitous aberrant RASSF1A promoter methylation in childhood neoplasia.

PURPOSE AND EXPERIMENTAL DESIGN: The role of RASSF1A has been elucidated recently in regulating apoptosis and cell cycle progression by inhibiting cyclin D1 accumulation. Aberrant RASSF1A promoter methylation has been found frequently in multiple adult cancer types. Using methylation-specific PCR and reverse transcription-PCR, we investigated epigenetic deregulation of RASSF1A in primary tumors, adjacent nontumor tissues, secondary metastases, peripheral blood cells, and plasma samples from children with 18 different cancer types, in association with their clinicopathologic features. RESULTS: Regardless of the tumor size, ubiquitous RASSF1A promoter methylation was found in 67% (16 of 24) of pediatric tumors, including neuroblastoma, thyroid carcinoma, hepatocellular carcinoma, pancreatoblastoma, adrenocortical carcinoma, Wilms' tumor, Burkitt's lymphoma, and T-cell lymphoma. A majority (75%) of pediatric cancer patients with tumoral RASSF1A methylation was male. Methylated RASSF1A alleles were also detected in 4 of 13 adjacent nontumor tissues, suggesting that this epigenetic change is potentially an early and critical event in childhood neoplasia. RASSF1A promoter methylation found in 92% (11 of 12) of cell lines largely derived from pediatric cancer patients was significantly associated with transcriptional silencing/repression. After demethylation treatment with 5-aza-2'-deoxycytidine, transcriptional reactivation was shown in KELLY, RD, and Namalwa cell lines as analyzed by reverse transcription-PCR. For the first time, RASSF1A methylation was detected in 54% (7 of 13), 40% (4 of 10), and 9% (1 of 11) of buffy coat samples collected before, during, and after treatment, correspondingly, from pediatric patients with neuroblastoma, thyroid carcinoma, hepatocellular carcinoma, rhabdomyosarcoma, Burkitt's lymphoma, T-cell lymphoma, or acute lymphoblastic leukemia. Concordantly, RASSF1A methylation was found during treatment in plasma of the same patients, suggesting cell death and good response to chemotherapy. CONCLUSIONS: RASSF1A methylation in tumor or buffy coat did not correlate strongly with age, tumor size, recurrence/metastasis, or overall survival in this cohort of pediatric cancer patients. Of importance, epigenetic inactivation of RASSF1A may potentially be crucial in pediatric tumor initiation.

Adolescent↗
PubMed2003

Quantitative analysis of tumor-derived methylated p16INK4a sequences in plasma, serum, and blood cells of hepatocellular carcinoma patients.

PURPOSE AND EXPERIMENTAL DESIGN: Using real-time quantitative methylation-specific PCR (RTQ-MSP), we quantified methylated p16INK4a sequences and determined the fractional concentrations of circulating tumor DNA in plasma, serum, and peripheral blood cells collected preoperatively, intraoperatively, and postoperatively from 49 patients with hepatocellular carcinoma (HCC). RESULTS: RTQ-MSP was sufficiently sensitive to detect down to 10 genome-equivalents of methylated p16INK4a sequences. Quantitative MSP data were expressed in terms of the methylation index, which was the percentage of bisulfite converted unmethylated and methylated p16INK4a sequences that consisted of methylated p16INK4a sequences. Quantities of methylated p16INK4a sequences were detected in peripheral circulation of 80% (23 of 29) of HCC patients. No significant difference was seen in the detectability and concentrations of methylated p16INK4a sequences (range: 10-4046 genome-equivalents/ml) between preoperative plasma and serum samples from HCC patients. Preoperatively, the p16INK4a methylation indices ranged from 0.2 to 100% and from 0.012 to 0.075% in the patients' plasma and buffy coat samples, respectively. After surgical resection, the median p16INK4a methylation indices in plasma and buffy coat concordantly decreased 12- and 15-fold, respectively. These results demonstrated the clinical usefulness and effectiveness of peripheral blood RTQ-MSP for detecting and monitoring HCC after treatment. Furthermore, none of the intraoperative plasma samples and only two of the intraoperative buffy coat samples were p16INK4a methylation positive. CONCLUSIONS: Quantification of epigenetic changes in peripheral blood by RTQ-MSP is useful for the detection and monitoring of HCC.

Apoptosis↗
PubMed2002

New markers for cancer detection.

Circulating tumor nucleic acids in blood have been demonstrated to reflect the biologic characteristics of tumors. During tumor progression, aberrant DNA methylation can lead to transcriptional silencing of tumor suppressor genes, DNA repair genes, and metastasis-inhibitor genes. Hypermethylation of multiple genes, detectable in the blood of cancer patients, has demonstrated increasing promise as a specific and sensitive molecular marker for detecting and monitoring cancer. In addition to these epigenetic markers, a number of mRNA markers may also enable cancer detection in the blood of patients with different cancer types. Quantification of circulating tumor cell mRNAs in cancer patients appears to be useful for monitoring cancer progression and response to treatment. DNA methylation markers and mRNA markers in the blood may open up diagnostic and prognostic possibilities.

Biomarkers, Tumor↗
PubMedDate not supplied

Transcriptional profiling of circulating tumor cells: quantification and cancer progression (Review).

Circulating tumor cells in peripheral blood have been demonstrated to reflect the biological characteristics of tumors including the potential for metastasis development and tumor recurrence. A number of mRNA markers may feasibly enable the detection of circulating tumor cells from virtually all patients with different cancer types. Of clinical relevance, quantification of circulating tumor cell mRNAs in cancer patients may prove valuable for monitoring disease progression and patients' response to treatment, and assessing the risk for metastasis or recurrence. With prognostic implications, the quantities of mRNA markers in blood could indicate the stage of cancer progression and the need for more intensive therapeutic intervention to better the outcome of cancer patients.

Biomarkers, Tumor↗
PubMedDate not supplied

Tumor-derived aberrant methylation in plasma of invasive ductal breast cancer patients: clinical implications.

Progressive p16 methylation has been associated with metastasis and invasive phenotypes in many cancers. Loss of E-cadherin (CDH1) function contributes to breast cancer progression by promoting cell proliferation, invasion and metastasis. Using methylation-specific PCR, aberrant hypermethylation of p16 and CDH1 in tumor and plasma was analyzed and correlated with levels of serum protein markers, carcinoembryonic antigen (CEA) and carcinoma antigen 15-3 (CA15.3), in 36 patients with invasive ductal breast cancer. Aberrant p16 methylation was found in 11% (4/36) of primary tumors and 8% (3/36) of plasma samples. Aberrant CDH1 methylation was detected in 25% (9/36) of primary tumors and 20% (7/36) of plasma samples. p16 and/or CDH1 hypermethylation was found in 31% (11/36) of primary breast carcinomas and 82% (9/11) of breast cancer patients with tumoral methylation showing identical epigenetic changes in plasma. The 25 patients without tumoral methylation did not show epigenetic changes in the plasma. Tumoral p16 methylation was significantly associated with advanced tumor stage (p=0.028; Fisher's exact test), tumor size (p=0.017) and nodal metastasis (p=0.002). However, p16 methylation in plasma was only associated with nodal metastasis (p=0.012). Altogether, aberrant p16 methylation in plasma and elevated serum CEA level were associated with advanced tumor stage (p=0.033), tumor size (p=0.022) and extensive nodal metastasis (p=0.003). With clinical implications, p16 hypermethylation in plasma and/or raised serum CEA levels may prove useful as diagnostic and prognostic markers for breast cancer.

Adult↗