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Lee NY, Hum M, Wong M, Ong PY, Lee SC, Lee ASG. Alleviating misclassified germline variants in underrepresented populations: A strategy using popmax. Genet Med 2024; 26:101124. [PMID: 38522067 DOI: 10.1016/j.gim.2024.101124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Revised: 03/14/2024] [Accepted: 03/18/2024] [Indexed: 03/26/2024] Open
Abstract
PURPOSE Germline variant interpretation often depends on population-matched control cohorts. This is not feasible for population groups that are underrepresented in current population reference databases. METHODS We classify germline variants with population-matched controls for 2 ancestrally diverse cohorts of patients: 132 early-onset or familial colorectal carcinoma patients from Singapore and 100 early-onset colorectal carcinoma patients from the United States. The effects of using a population-mismatched control cohort are simulated by swapping the control cohorts used for each patient cohort, with or without the popmax computational strategy. RESULTS Population-matched classifications revealed a combined 62 pathogenic or likely pathogenic (P/LP) variants in 34 genes across both cohorts. Using a population-mismatched control cohort resulted in misclassification of non-P/LP variants as P/LP, driven by the absence of ancestry-specific rare variants in the control cohort. Popmax was more effective in alleviating misclassifications for the Singapore cohort than the US cohort. CONCLUSION Underrepresented population groups can suffer from higher rates of false-positive P/LP results. Popmax can partially alleviate these misclassifications, but its efficacy still depends on the degree with which the population groups are represented in the control cohort.
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Affiliation(s)
- Ning Yuan Lee
- Division of Cellular and Molecular Research, National Cancer Centre Singapore, Singapore
| | - Melissa Hum
- Division of Cellular and Molecular Research, National Cancer Centre Singapore, Singapore
| | - Matthew Wong
- Division of Cellular and Molecular Research, National Cancer Centre Singapore, Singapore
| | - Pei-Yi Ong
- Department of Hematology-Oncology, National University Cancer Institute, Singapore (NCIS), National University Health System, Singapore
| | - Soo-Chin Lee
- Department of Hematology-Oncology, National University Cancer Institute, Singapore (NCIS), National University Health System, Singapore; Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Cancer Science Institute, Singapore (CSI), National University of Singapore, Singapore
| | - Ann S G Lee
- Division of Cellular and Molecular Research, National Cancer Centre Singapore, Singapore; SingHealth Duke-NUS Oncology Academic Clinical Programme (ONCO ACP), Duke-NUS Medical School, Singapore; Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
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Lee NY, Hum M, Tan GP, Seah AC, Kin PT, Tan NC, Law HY, Lee ASG. Degradation of methylation signals in cryopreserved DNA. Clin Epigenetics 2023; 15:147. [PMID: 37697422 PMCID: PMC10496221 DOI: 10.1186/s13148-023-01565-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Accepted: 09/06/2023] [Indexed: 09/13/2023] Open
Abstract
BACKGROUND Blood-based DNA methylation has shown great promise as a biomarker in a wide variety of diseases. Studies of DNA methylation in blood often utilize samples which have been cryopreserved for years or even decades. Therefore, changes in DNA methylation associated with long-term cryopreservation can introduce biases or otherwise mislead methylation analyses of cryopreserved DNA. However, previous studies have presented conflicting results with studies reporting hypomethylation, no effect, or even hypermethylation of DNA following long-term cryopreservation. These studies may have been limited by insufficient sample sizes, or by their profiling of methylation only on an aggregate global scale, or profiling of only a few CpGs. RESULTS We analyzed two large prospective cohorts: a discovery (n = 126) and a validation (n = 136) cohort, where DNA was cryopreserved for up to four years. In both cohorts there was no detectable change in mean global methylation across increasing storage durations as DNA. However, when analysis was performed on the level of individual CpG methylation both cohorts exhibited a greater number of hypomethylated than hypermethylated CpGs at q-value < 0.05 (4049 hypomethylated but only 50 hypermethylated CpGs in discovery, and 63 hypomethylated but only 6 hypermethylated CpGs in validation). The results were the same even after controlling for age, storage duration as buffy coat prior to DNA extraction, and estimated cell type composition. Furthermore, we find that in both cohorts, CpGs have a greater likelihood to be hypomethylated the closer they are to a CpG island; except for CpGs at the CpG islands themselves which are less likely to be hypomethylated. CONCLUSION Cryopreservation of DNA after a few years results in a detectable bias toward hypomethylation at the level of individual CpG methylation, though when analyzed in aggregate there is no detectable change in mean global methylation. Studies profiling methylation in cryopreserved DNA should be mindful of this hypomethylation bias, and more attention should be directed at developing more stable methods of DNA cryopreservation for biomedical research or clinical use.
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Affiliation(s)
- Ning Yuan Lee
- Division of Cellular and Molecular Research, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
| | - Melissa Hum
- Division of Cellular and Molecular Research, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
| | - Guek Peng Tan
- DNA Diagnostic and Research Laboratory, KK Women's and Children's Hospital, 100 Bukit Timah Rd, Singapore, 229899, Singapore
| | - Ai Choo Seah
- SingHealth Polyclinics, 167 Jalan Bukit Merah, Singapore, 150167, Singapore
| | - Patricia T Kin
- SingHealth Polyclinics, 167 Jalan Bukit Merah, Singapore, 150167, Singapore
| | - Ngiap Chuan Tan
- SingHealth Polyclinics, 167 Jalan Bukit Merah, Singapore, 150167, Singapore
- SingHealth Duke-NUS Family Medicine Academic Clinical Programme, Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore
| | - Hai-Yang Law
- DNA Diagnostic and Research Laboratory, KK Women's and Children's Hospital, 100 Bukit Timah Rd, Singapore, 229899, Singapore
| | - Ann S G Lee
- Division of Cellular and Molecular Research, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore.
- SingHealth Duke-NUS Oncology Academic Clinical Programme (ONCO ACP), Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore.
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, 2 Medical Drive, Singapore, 117593, Singapore.
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Lee NY, Hum M, Zihara S, Wang L, Myint MK, Lim DWT, Toh CK, Skanderup A, Samol J, Tan MH, Ang P, Lee SC, Tan EH, Lai GGY, Tan DSW, Yap YS, Lee ASG. Correction: Landscape of germline pathogenic variants in patients with dual primary breast and lung cancer. Hum Genomics 2023; 17:74. [PMID: 37580755 PMCID: PMC10424336 DOI: 10.1186/s40246-023-00518-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/16/2023] Open
Affiliation(s)
- Ning-Yuan Lee
- Division of Cellular and Molecular Research, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
| | - Melissa Hum
- Division of Cellular and Molecular Research, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
| | - Sabna Zihara
- Division of Cellular and Molecular Research, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
| | - Lanying Wang
- Division of Medical Oncology, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
| | - Matthew K Myint
- Division of Cellular and Molecular Research, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
| | - Darren Wan-Teck Lim
- Division of Medical Oncology, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
- SingHealth Duke-NUS Oncology Academic Clinical Programme (ONCO ACP), Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore
| | - Chee-Keong Toh
- Division of Medical Oncology, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
| | - Anders Skanderup
- Genome Institute of Singapore, 60 Biopolis St, Singapore, 138672, Singapore
| | - Jens Samol
- Medical Oncology Department, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, Singapore, 308433, Singapore
- Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Min-Han Tan
- Lucence Diagnostics Pte Ltd, 211 Henderson Road, Singapore, 159552, Singapore
| | - Peter Ang
- Oncocare Cancer Centre, Gleneagles Medical Centre, 6 Napier Road, Singapore, 258499, Singapore
| | - Soo-Chin Lee
- Department of Hematology-Oncology, National University Cancer Institute, Singapore (NCIS), National University Health System, 5 Lower Kent Ridge Road, Singapore, 119074, Singapore
- Cancer Science Institute, Singapore (CSI), National University of Singapore, 14 Medical Dr, Singapore, 117599, Singapore
| | - Eng-Huat Tan
- Division of Medical Oncology, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
- Clinical Trials and Epidemiological Sciences, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
| | - Gillianne G Y Lai
- Division of Medical Oncology, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
- SingHealth Duke-NUS Oncology Academic Clinical Programme (ONCO ACP), Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore
| | - Daniel S W Tan
- Division of Medical Oncology, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
- SingHealth Duke-NUS Oncology Academic Clinical Programme (ONCO ACP), Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore
- Genome Institute of Singapore, 60 Biopolis St, Singapore, 138672, Singapore
- Clinical Trials and Epidemiological Sciences, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
| | - Yoon-Sim Yap
- Division of Medical Oncology, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
- SingHealth Duke-NUS Oncology Academic Clinical Programme (ONCO ACP), Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore
| | - Ann S G Lee
- Division of Cellular and Molecular Research, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore.
- SingHealth Duke-NUS Oncology Academic Clinical Programme (ONCO ACP), Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore.
- Department of Physiology, Yong Loo Lin School of Medicine, Medical Drive, National University of Singapore, Singapore, 117593, Singapore.
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Lee NY, Hum M, Zihara S, Wang L, Myint MK, Lim DWT, Toh CK, Skanderup A, Samol J, Tan MH, Ang P, Lee SC, Tan EH, Lai GGY, Tan DSW, Yap YS, Lee ASG. Landscape of germline pathogenic variants in patients with dual primary breast and lung cancer. Hum Genomics 2023; 17:66. [PMID: 37461096 PMCID: PMC10353088 DOI: 10.1186/s40246-023-00510-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Accepted: 07/10/2023] [Indexed: 07/20/2023] Open
Abstract
BACKGROUND Cancer predisposition is most often studied in the context of single cancers. However, inherited cancer predispositions can also give rise to multiple primary cancers. Yet, there is a paucity of studies on genetic predisposition in multiple primary cancers, especially those outside of well-defined cancer predisposition syndromes. This study aimed to identify germline variants associated with dual primary cancers of the breast and lung. METHODS Exome sequencing was performed on germline DNA from 55 Singapore patients (52 [95%] never-smokers) with dual primaries in the breast and lung, confirmed by histopathology. Using two large control cohorts: the local SG10K_Health (n = 9770) and gnomAD non-cancer East Asians (n = 9626); and two additional local case cohorts of early-onset or familial breast cancer (n = 290), and lung cancer (n = 209), variants were assessed for pathogenicity in accordance with ACMG/AMP guidelines. In particular, comparisons were made with known pathogenic or likely pathogenic variants in the ClinVar database, pathogenicity predictions were obtained from in silico prediction software, and case-control association analyses were performed. RESULTS Altogether, we identified 19 pathogenic or likely pathogenic variants from 16 genes, detected in 17 of 55 (31%) patients. Six of the 19 variants were identified using ClinVar, while 13 variants were classified pathogenic or likely pathogenic using ACMG/AMP guidelines. The 16 genes include well-known cancer predisposition genes such as BRCA2, TP53, and RAD51D; but also lesser known cancer genes EXT2, WWOX, GATA2, and GPC3. Most of these genes are involved in DNA damage repair, reaffirming the role of impaired DNA repair mechanisms in the development of multiple malignancies. These variants warrant further investigations in additional populations. CONCLUSIONS We have identified both known and novel variants significantly enriched in patients with primary breast and lung malignancies, expanding the body of known cancer predisposition variants for both breast and lung cancer. These variants are mostly from genes involved in DNA repair, affirming the role of impaired DNA repair in the predisposition and development of multiple cancers.
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Affiliation(s)
- Ning-Yuan Lee
- Division of Cellular and Molecular Research, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
| | - Melissa Hum
- Division of Cellular and Molecular Research, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
| | - Sabna Zihara
- Division of Cellular and Molecular Research, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
| | - Lanying Wang
- Division of Medical Oncology, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
| | - Matthew K Myint
- Division of Cellular and Molecular Research, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
| | - Darren Wan-Teck Lim
- Division of Medical Oncology, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
- SingHealth Duke-NUS Oncology Academic Clinical Programme (ONCO ACP), Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore
| | - Chee-Keong Toh
- Division of Medical Oncology, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
| | - Anders Skanderup
- Genome Institute of Singapore, 60 Biopolis St, Singapore, 138672, Singapore
| | - Jens Samol
- Medical Oncology Department, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, Singapore, 308433, Singapore
- Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Min-Han Tan
- Lucence Diagnostics Pte Ltd, 211 Henderson Road, Singapore, 159552, Singapore
| | - Peter Ang
- Oncocare Cancer Centre, Gleneagles Medical Centre, 6 Napier Road, Singapore, 258499, Singapore
| | - Soo-Chin Lee
- Department of Hematology-Oncology, National University Cancer Institute, Singapore (NCIS), National University Health System, 5 Lower Kent Ridge Road, Singapore, 119074, Singapore
- Cancer Science Institute, Singapore (CSI), National University of Singapore, 14 Medical Dr, Singapore, 117599, Singapore
| | - Eng-Huat Tan
- Division of Medical Oncology, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
- Clinical Trials and Epidemiological Sciences, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
| | - Gillianne G Y Lai
- Division of Medical Oncology, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
- SingHealth Duke-NUS Oncology Academic Clinical Programme (ONCO ACP), Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore
| | - Daniel S W Tan
- Division of Medical Oncology, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
- SingHealth Duke-NUS Oncology Academic Clinical Programme (ONCO ACP), Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore
- Genome Institute of Singapore, 60 Biopolis St, Singapore, 138672, Singapore
- Clinical Trials and Epidemiological Sciences, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
| | - Yoon-Sim Yap
- Division of Medical Oncology, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore
- SingHealth Duke-NUS Oncology Academic Clinical Programme (ONCO ACP), Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore
| | - Ann S G Lee
- Division of Cellular and Molecular Research, National Cancer Centre Singapore, 30 Hospital Boulevard, Singapore, 168583, Singapore.
- SingHealth Duke-NUS Oncology Academic Clinical Programme (ONCO ACP), Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore.
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, 2 Medical Drive, Singapore, 117593, Singapore.
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5
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Lee NY, Hum M, Amali AA, Lim WK, Wong M, Myint MK, Tay RJ, Ong PY, Samol J, Lim CW, Ang P, Tan MH, Lee SC, Lee ASG. Whole-exome sequencing of BRCA-negative breast cancer patients and case-control analyses identify variants associated with breast cancer susceptibility. Hum Genomics 2022; 16:61. [PMID: 36424660 PMCID: PMC9685974 DOI: 10.1186/s40246-022-00435-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 11/14/2022] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND For the majority of individuals with early-onset or familial breast cancer referred for genetic testing, the genetic basis of their familial breast cancer remains unexplained. To identify novel germline variants associated with breast cancer predisposition, whole-exome sequencing (WES) was performed. METHODS WES on 290 BRCA1/BRCA2-negative Singaporeans with early-onset breast cancer and/or a family history of breast cancer was done. Case-control analysis against the East-Asian subpopulation (EAS) from the Genome Aggregation Database (gnomAD) identified variants enriched in cases, which were further selected by occurrence in cancer gene databases. Variants were further evaluated in repeated case-control analyses using a second case cohort from the database of Genotypes and Phenotypes (dbGaP) comprising 466 early-onset breast cancer patients from the United States, and a Singapore SG10K_Health control cohort. RESULTS Forty-nine breast cancer-associated germline pathogenic variants in 37 genes were identified in Singapore cases versus gnomAD (EAS). Compared against SG10K_Health controls, 13 of 49 variants remain significantly enriched (False Discovery Rate (FDR)-adjusted p < 0.05). Comparing these 49 variants in dbGaP cases against gnomAD (EAS) and SG10K_Health controls revealed 23 concordant variants that were significantly enriched (FDR-adjusted p < 0.05). Fourteen variants were consistently enriched in breast cancer cases across all comparisons (FDR-adjusted p < 0.05). Seven variants in GPRIN2, NRG1, MYO5A, CLIP1, CUX1, GNAS and MGA were confirmed by Sanger sequencing. CONCLUSIONS In conclusion, we have identified pathogenic variants in genes associated with breast cancer predisposition. Importantly, many of these variants were significant in a second case cohort from dbGaP, suggesting that the strategy of using case-control analysis to select variants could potentially be utilized for identifying variants associated with cancer susceptibility.
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Affiliation(s)
- Ning Yuan Lee
- grid.410724.40000 0004 0620 9745Division of Cellular and Molecular Research, Humphrey Oei Institute of Cancer Research, National Cancer Centre Singapore, 11 Hospital Crescent, Singapore, 169610 Singapore
| | - Melissa Hum
- grid.410724.40000 0004 0620 9745Division of Cellular and Molecular Research, Humphrey Oei Institute of Cancer Research, National Cancer Centre Singapore, 11 Hospital Crescent, Singapore, 169610 Singapore
| | - Aseervatham Anusha Amali
- grid.410724.40000 0004 0620 9745Division of Cellular and Molecular Research, Humphrey Oei Institute of Cancer Research, National Cancer Centre Singapore, 11 Hospital Crescent, Singapore, 169610 Singapore
| | - Wei Kiat Lim
- grid.410724.40000 0004 0620 9745Division of Cellular and Molecular Research, Humphrey Oei Institute of Cancer Research, National Cancer Centre Singapore, 11 Hospital Crescent, Singapore, 169610 Singapore
| | - Matthew Wong
- grid.410724.40000 0004 0620 9745Division of Cellular and Molecular Research, Humphrey Oei Institute of Cancer Research, National Cancer Centre Singapore, 11 Hospital Crescent, Singapore, 169610 Singapore
| | - Matthew Khine Myint
- grid.410724.40000 0004 0620 9745Division of Cellular and Molecular Research, Humphrey Oei Institute of Cancer Research, National Cancer Centre Singapore, 11 Hospital Crescent, Singapore, 169610 Singapore
| | - Ru Jin Tay
- Lucence Diagnostics Pte Ltd, 211 Henderson Road, Singapore, 159552 Singapore
| | - Pei-Yi Ong
- grid.440782.d0000 0004 0507 018XDepartment of Hematology-Oncology, National University Cancer Institute, Singapore (NCIS), National University Health System, 5 Lower Kent Ridge Road, Singapore, 119074 Singapore
| | - Jens Samol
- grid.240988.f0000 0001 0298 8161Medical Oncology Department, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, Singapore, 308433 Singapore ,grid.21107.350000 0001 2171 9311Johns Hopkins University, Baltimore, MD 21218 USA
| | - Chia Wei Lim
- grid.240988.f0000 0001 0298 8161Department of Personalised Medicine, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, Singapore, 308433 Singapore
| | - Peter Ang
- grid.415572.00000 0004 0620 9577Oncocare Cancer Centre, Gleneagles Medical Centre, 6 Napier Road, Singapore, 258499 Singapore
| | - Min-Han Tan
- Lucence Diagnostics Pte Ltd, 211 Henderson Road, Singapore, 159552 Singapore
| | - Soo-Chin Lee
- grid.440782.d0000 0004 0507 018XDepartment of Hematology-Oncology, National University Cancer Institute, Singapore (NCIS), National University Health System, 5 Lower Kent Ridge Road, Singapore, 119074 Singapore ,grid.4280.e0000 0001 2180 6431Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, 10 Medical Dr, Singapore, 117597 Singapore ,grid.4280.e0000 0001 2180 6431Cancer Science Institute, Singapore (CSI), National University of Singapore, 14 Medical Dr, Singapore, 117599 Singapore
| | - Ann S. G. Lee
- grid.410724.40000 0004 0620 9745Division of Cellular and Molecular Research, Humphrey Oei Institute of Cancer Research, National Cancer Centre Singapore, 11 Hospital Crescent, Singapore, 169610 Singapore ,grid.4280.e0000 0001 2180 6431Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, 2 Medical Drive, Singapore, 117593 Singapore ,grid.428397.30000 0004 0385 0924SingHealth Duke-NUS Oncology Academic Clinical Programme (ONCO ACP), Duke-NUS Graduate Medical School, 8 College Road, Singapore, 169857 Singapore
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Yuan J, Ng WH, Lam PYP, Wang Y, Xia H, Yap J, Guan SP, Lee ASG, Wang M, Baccarini M, Hu J. The dimer-dependent catalytic activity of RAF family kinases is revealed through characterizing their oncogenic mutants. Oncogene 2018; 37:5719-5734. [PMID: 29930381 PMCID: PMC6202329 DOI: 10.1038/s41388-018-0365-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Revised: 05/18/2018] [Accepted: 05/21/2018] [Indexed: 12/19/2022]
Abstract
Although extensively studied for three decades, the molecular mechanisms that regulate the RAF/MEK/ERK kinase cascade remain ambiguous. Recent studies identified the dimerization of RAF as a key event in the activation of this cascade. Here, we show that in-frame deletions in the β3-αC loop activate ARAF as well as BRAF and other oncogenic kinases by enforcing homodimerization. By characterizing these RAF mutants, we find that ARAF has less allosteric and catalytic activity than the other two RAF isoforms, which arises from its non-canonical APE motif. Further, these RAF mutants exhibit a strong oncogenic potential, and a differential inhibitor resistance that correlates with their dimer affinity. Using these unique mutants, we demonstrate that active RAFs, including the BRAF(V600E) mutant, phosphorylate MEK in a dimer-dependent manner. This study characterizes a special category of oncogenic kinase mutations, and elucidates the molecular basis that underlies the differential ability of RAF isoforms to stimulate MEK-ERK pathway. Further, this study reveals a unique catalytic feature of RAF family kinases that can be exploited to control their activities for cancer therapies.
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Affiliation(s)
- Jimin Yuan
- Division of Cellular and Molecular Research, Singapore, Singapore
| | - Wan Hwa Ng
- Division of Cellular and Molecular Research, Singapore, Singapore
| | - Paula Y P Lam
- Division of Cellular and Molecular Research, Singapore, Singapore.,Cancer and Stem Cell Program, Duke-NUS Medical School, 8 College Road, 169857, Singapore, Singapore
| | - Yu Wang
- Division of Cellular and Molecular Research, Singapore, Singapore
| | - Hongping Xia
- Division of Cellular and Molecular Research, Singapore, Singapore
| | - Jiajun Yap
- Division of Cellular and Molecular Research, Singapore, Singapore
| | - Shou Ping Guan
- Division of Cellular and Molecular Research, Singapore, Singapore
| | - Ann S G Lee
- Division of Medical Sciences, National Cancer Centre Singapore, 11 Hospital Drive, Singapore, 169610, Singapore.,Office of Clinical & Academic Faculty Affairs, Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore.,Department of Physiology, National University of Singapore, 2 Medical Drive, 117597, Singapore, Singapore
| | - Mei Wang
- Cancer and Stem Cell Program, Duke-NUS Medical School, 8 College Road, 169857, Singapore, Singapore
| | - Manuela Baccarini
- Max F. Perutz Laboratories, University of Vienna, Doktor-Bohr-Gasse 9, 1030, Vienna, Austria
| | - Jiancheng Hu
- Division of Cellular and Molecular Research, Singapore, Singapore. .,Cancer and Stem Cell Program, Duke-NUS Medical School, 8 College Road, 169857, Singapore, Singapore.
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7
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Kwong A, Shin VY, Ho JCW, Kang E, Nakamura S, Teo SH, Lee ASG, Sng JH, Ginsburg OM, Kurian AW, Weitzel JN, Siu MT, Law FBF, Chan TL, Narod SA, Ford JM, Ma ESK, Kim SW. Comprehensive spectrum of BRCA1 and BRCA2 deleterious mutations in breast cancer in Asian countries. J Med Genet 2015; 53:15-23. [PMID: 26187060 DOI: 10.1136/jmedgenet-2015-103132] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Accepted: 07/02/2015] [Indexed: 12/20/2022]
Abstract
Approximately 5%-10% of breast cancers are due to genetic predisposition caused by germline mutations; the most commonly tested genes are BRCA1 and BRCA2 mutations. Some mutations are unique to one family and others are recurrent; the spectrum of BRCA1/BRCA2 mutations varies depending on the geographical origins, populations or ethnic groups. In this review, we compiled data from 11 participating Asian countries (Bangladesh, Mainland China, Hong Kong SAR, Indonesia, Japan, Korea, Malaysia, Philippines, Singapore, Thailand and Vietnam), and from ethnic Asians residing in Canada and the USA. We have additionally conducted a literature review to include other Asian countries mainly in Central and Western Asia. We present the current pathogenic mutation spectrum of BRCA1/BRCA2 genes in patients with breast cancer in various Asian populations. Understanding BRCA1/BRCA2 mutations in Asians will help provide better risk assessment and clinical management of breast cancer.
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Affiliation(s)
- Ava Kwong
- Department of Surgery, The University of Hong Kong, Hong Kong, Hong Kong Hong Kong Hereditary Breast Cancer Family Registry, Hong Kong, Hong Kong Departments of Medicine (Oncology) and Genetics, Stanford University School of Medicine, Stanford, California, USA Department of Surgery, Hong Kong Sanatorium & Hospital, Hong Kong, Hong Kong
| | - Vivian Y Shin
- Department of Surgery, The University of Hong Kong, Hong Kong, Hong Kong
| | - John C W Ho
- Department of Surgery, The University of Hong Kong, Hong Kong, Hong Kong Department of Molecular Pathology, Hong Kong Sanatorium & Hospital, Hong Kong, Hong Kong
| | - Eunyoung Kang
- Department of Surgery, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea
| | - Seigo Nakamura
- Department of Surgery, Division of Breast Surgical Oncology, Showa University School of Medicine, Tokyo, Japan
| | - Soo-Hwang Teo
- Cancer Research Initiatives Foundation, Sime Darby Medical Centre, Subang Jaya, Selangor, Malaysia Faculty of Medicine, University Malaya Cancer Research Institute, University Malaya, Subang Jaya, Malaysia
| | - Ann S G Lee
- Division of Medical Sciences, National Cancer Centre, Singapore, Singapore Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore Office of Clinical & Academic Faculty Affairs, Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Jen-Hwei Sng
- Department of Surgery, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Ophira M Ginsburg
- Women's College Research Institute, University of Toronto, Toronto, Ontario, Canada
| | - Allison W Kurian
- Departments of Medicine (Oncology) and Genetics, Stanford University School of Medicine, Stanford, California, USA
| | - Jeffrey N Weitzel
- Division of Clinical Cancer Genetics, City of Hope National Medical Center, Duarte, California, USA
| | - Man-Ting Siu
- Department of Surgery, The University of Hong Kong, Hong Kong, Hong Kong
| | - Fian B F Law
- Hong Kong Hereditary Breast Cancer Family Registry, Hong Kong, Hong Kong Department of Molecular Pathology, Hong Kong Sanatorium & Hospital, Hong Kong, Hong Kong
| | - Tsun-Leung Chan
- Hong Kong Hereditary Breast Cancer Family Registry, Hong Kong, Hong Kong Department of Molecular Pathology, Hong Kong Sanatorium & Hospital, Hong Kong, Hong Kong
| | - Steven A Narod
- Women's College Research Institute, University of Toronto, Toronto, Ontario, Canada
| | - James M Ford
- Departments of Medicine (Oncology) and Genetics, Stanford University School of Medicine, Stanford, California, USA
| | - Edmond S K Ma
- Hong Kong Hereditary Breast Cancer Family Registry, Hong Kong, Hong Kong Department of Molecular Pathology, Hong Kong Sanatorium & Hospital, Hong Kong, Hong Kong
| | - Sung-Won Kim
- Department of Surgery, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea
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8
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9
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Shekar S, Yeo ZX, Wong JCL, Chan MKL, Ong DCT, Tongyoo P, Wong SY, Lee ASG. Detecting novel genetic variants associated with isoniazid-resistant Mycobacterium tuberculosis. PLoS One 2014; 9:e102383. [PMID: 25025225 PMCID: PMC4099304 DOI: 10.1371/journal.pone.0102383] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2013] [Accepted: 06/18/2014] [Indexed: 12/30/2022] Open
Abstract
Background Isoniazid (INH) is a highly effective antibiotic central for the treatment of Mycobacterium tuberculosis (MTB). INH-resistant MTB clinical isolates are frequently mutated in the katG gene and the inhA promoter region, but 10 to 37% of INH-resistant clinical isolates have no detectable alterations in currently known gene targets associated with INH-resistance. We aimed to identify novel genes associated with INH-resistance in these latter isolates. Methodology/Principal Findings INH-resistant clinical isolates of MTB were pre-screened for mutations in the katG, inhA, kasA and ndh genes and the regulatory regions of inhA and ahpC. Twelve INH-resistant isolates with no mutations, and 17 INH-susceptible MTB isolates were subjected to whole genome sequencing. Phylogenetically related variants and synonymous mutations were excluded and further analysis revealed mutations in 60 genes and 4 intergenic regions associated with INH-resistance. Sanger sequencing verification of 45 genes confirmed that mutations in 40 genes were observed only in INH-resistant isolates and not in INH-susceptible isolates. The ratios of non-synonymous to synonymous mutations (dN/dS ratio) for the INH-resistance associated mutations identified in this study were 1.234 for INH-resistant and 0.654 for INH-susceptible isolates, strongly suggesting that these mutations are indeed associated with INH-resistance. Conclusion The discovery of novel targets associated with INH-resistance described in this study may potentially be important for the development of improved molecular detection strategies.
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Affiliation(s)
- Sandhya Shekar
- Division of Medical Sciences, National Cancer Centre, Singapore, Singapore
| | - Zhen Xuan Yeo
- Division of Medical Sciences, National Cancer Centre, Singapore, Singapore
| | - Joshua C. L. Wong
- Division of Medical Sciences, National Cancer Centre, Singapore, Singapore
| | - Maurice K. L. Chan
- Division of Medical Sciences, National Cancer Centre, Singapore, Singapore
| | - Danny C. T. Ong
- Division of Medical Sciences, National Cancer Centre, Singapore, Singapore
| | - Pumipat Tongyoo
- Division of Medical Sciences, National Cancer Centre, Singapore, Singapore
| | - Sin-Yew Wong
- Department of Infectious Diseases, Singapore General Hospital, Singapore, Singapore
| | - Ann S. G. Lee
- Division of Medical Sciences, National Cancer Centre, Singapore, Singapore
- Office of Clinical & Academic Faculty Affairs, Duke-NUS Graduate Medical School, Singapore, Singapore
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- * E-mail:
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Ong DCT, Ho YM, Rudduck C, Chin K, Kuo WL, Lie DKH, Chua CLM, Tan PH, Eu KW, Seow-Choen F, Wong CY, Hong GS, Gray JW, Lee ASG. LARG at chromosome 11q23 has functional characteristics of a tumor suppressor in human breast and colorectal cancer. Oncogene 2009; 28:4189-200. [PMID: 19734946 PMCID: PMC2844776 DOI: 10.1038/onc.2009.266] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Deletion of 11q23-q24 is frequent in a diverse variety of malignancies, including breast and colorectal carcinoma, implicating the presence of a tumor suppressor gene at that chromosomal region. We examined a 6-Mb region on 11q23 by high-resolution deletion mapping, using both loss of heterozygosity analysis and customized microarray comparative genomic hybridization. LARG (leukemia-associated Rho guanine-nucleotide exchange factor) (also called ARHGEF12), identified from the analysed region, is frequently underexpressed in breast and colorectal carcinomas with a reduced expression observed in all breast cancer cell lines (n=11), in 12 of 38 (32%) primary breast cancers, 5 of 10 (50%) colorectal cell lines and in 20 of 37 (54%) primary colorectal cancers. Underexpression of the LARG transcript was significantly associated with genomic loss (P=0.00334). Hypermethylation of the LARG promoter was not detected in either breast or colorectal cancer, and treatment of four breast and four colorectal cancer cell lines with 5-aza-2'-deoxycytidine and/or trichostatin A did not result in a reactivation of LARG. Enforced expression of LARG in breast and colorectal cancer cells by stable transfection resulted in reduced cell proliferation and colony formation, as well as in a markedly slower cell migration rate in colorectal cancer cells, providing functional evidence for LARG as a candidate tumor suppressor gene.
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Affiliation(s)
- DCT Ong
- Division of Medical Sciences, National Cancer Centre, Singapore
| | - YM Ho
- Division of Medical Sciences, National Cancer Centre, Singapore
| | - C Rudduck
- Department of Pathology, Singapore General Hospital, Singapore
| | - K Chin
- UCSF Comprehensive Cancer Center, University of California, San Francisco, CA, USA
| | - W-L Kuo
- UCSF Comprehensive Cancer Center, University of California, San Francisco, CA, USA
- Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - DKH Lie
- Division of Medical Sciences, National Cancer Centre, Singapore
| | - CLM Chua
- Division of Medical Sciences, National Cancer Centre, Singapore
| | - PH Tan
- Department of Pathology, Singapore General Hospital, Singapore
| | - KW Eu
- Department of Colorectal Surgery, Singapore General Hospital, Singapore
| | - F Seow-Choen
- Department of Colorectal Surgery, Singapore General Hospital, Singapore
| | - CY Wong
- Department of General Surgery, Singapore General Hospital, Singapore
| | - GS Hong
- Department of General Surgery, Singapore General Hospital, Singapore
| | - JW Gray
- UCSF Comprehensive Cancer Center, University of California, San Francisco, CA, USA
- Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - ASG Lee
- Division of Medical Sciences, National Cancer Centre, Singapore
- Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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Ang P, Lim IHK, Yong RYY, Lee ASG. A molecular approach for identifying individuals with Li-Fraumeni syndrome who have a limited family history. Clin Genet 2009; 75:294-7. [PMID: 19250386 DOI: 10.1111/j.1399-0004.2008.01133.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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12
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Lee ASG, Ang P. CHEK2*1100delC screening of Asian women with a family history of breast cancer is unwarranted. J Clin Oncol 2008; 26:2419; author reply 2419-20. [PMID: 18467741 DOI: 10.1200/jco.2008.16.4335] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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13
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Lee TC, Lee ASG, Li KB. Incorporating the amino acid properties to predict the significance of missense mutations. Amino Acids 2008; 35:615-26. [DOI: 10.1007/s00726-008-0087-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2008] [Accepted: 02/26/2008] [Indexed: 11/25/2022]
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Abstract
Previous studies have suggested that Mycobacterium tuberculosis kasA G312S and G269S gene mutations may represent sequence polymorphisms of the M. tuberculosis East-African-Indian (EAI) and T families, respectively, rather than relating to isoniazid resistance. The present study examined polymorphisms of these two codons in 98 drug-susceptible M. tuberculosis isolates (68 EAI and 30 T isolates). Twenty-eight isolates belonging to a sub-lineage of the EAI family had the kasA G312S mutation, but none of the 30 T isolates had the G269S mutation. The data suggest that the kasA G312S mutation is not related to isoniazid resistance, but represents a sequence polymorphism in a sub-lineage of the EAI family.
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Affiliation(s)
- Y-J Sun
- Department of Infectious Diseases, Tan Tock Seng Hospital, Singapore.
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15
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Sun YJ, Lee ASG, Wong SY, Heersma H, Kremer K, van Soolingen D, Paton NI. Genotype and phenotype relationships and transmission analysis of drug-resistant tuberculosis in Singapore. Int J Tuberc Lung Dis 2007; 11:436-42. [PMID: 17394691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2023] Open
Abstract
SETTING The small urban country of Singapore. OBJECTIVES To investigate the relationships between Mycobacterium tuberculosis genotypes and drug-resistant phenotypes and to analyse the transmission of drug-resistant tuberculosis (DR-TB). DESIGN A 29-month population-based study comparing drug-resistant and drug-susceptible M. tuberculosis isolates. RESULTS We found that multidrug-resistant (MDR) isolates (n = 41, OR 2.66, 95%CI 1.28-5.50), rifampicin-resistant isolates (n = 48, OR 2.88, 95%CI 1.44-5.76), and streptomycin (SM) resistant isolates (n = 103, OR 3.35, 95%CI 1.99-5.62) were more common among Beijing genotype strains than among non-Beijing strains, while SM-resistant isolates were less common in East-African-Indian (EAI) genotype strains than in non-EAI strains (OR 0.30, 95%CI 0.14-0.64). Based on clustering analysis and drug-resistant patterns, 22 of 230 drug-resistant isolates were found to have likely resulted from recent transmission. The estimated transmission rate of DR-TB was 9.6% and that of MDR-TB was 7.7%. The transmission rate of DR-TB was significantly higher among Beijing genotype strains than non-Beijing strains (12.9% vs. 4.4%; P = 0.034). CONCLUSIONS Compared to other genotypes, Beijing genotype strains are associated with a higher frequency of drug resistance, including multidrug resistance, and are more transmissible. However, the overall transmission rate of DR-TB in Singapore is low.
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Affiliation(s)
- Y-J Sun
- Infectious Disease Research Laboratory, Department of Infectious Diseases, TTSH Medical Centre, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, Singapore 308433.
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Zhou Q, Cheung YB, Jada SR, Lim WT, Kuo WL, Gray JW, Lee ASG, Chowbay B. EGFR Intron 1 polymorphism in Asian Populations and its correlation with EGFR gene expression and amplification in breast tumor tissues. Cancer Biol Ther 2006; 5:1445-9. [PMID: 17102595 DOI: 10.4161/cbt.5.11.3457] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
AIM The purpose of this study was to test the hypothesis if longer CA dinucleotide repeats are more common in the Asian population and also to gain insights into the interplay between the CA dinucleotide repeats and the frequencies of EGFR gene expression and amplifications as this might have therapeutic implications with regards to treatment with tyrosine kinase inhibitors. MATERIALS AND METHODS The EGFR intron 1 polymorphism was analysed in three distinct healthy Asian subjects, namely, Chinese (N = 96), Malays (N = 98) and Indians (N = 100). Comparative genomic hybridisation was performed to investigate for changes in DNA copy number in relation to the polymorphic CA dinucleotide repeats in breast tumor tissues (N = 22). RESULTS The frequency of short alleles with 14 and 15 CA repeats were most common in the Asian populations and significantly higher than those reported for Caucasians. The frequency of 20 CA repeats was 5%, almost 13-fold lower than previous reports. EGFR amplifications were detected in 23% and 11% of breast tumor tissues harboring short and long CA repeats, respectively. CONCLUSION Our results show that the frequency of alleles encoding for short CA dinucleotide repeats is common in Asian populations. EGFR expression and amplification levels were also higher in Asian breast tumor tissues with short CA dinucleotide repeats. These findings suggest that the EGFR intron 1 polymorphism may influence response to treatment with tyrosine kinase inhibitors in breast cancer patients and further studies are warranted.
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Affiliation(s)
- Qingyu Zhou
- Laboratory of Clinical Pharmacology, National Cancer Centre, Singapore
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Affiliation(s)
- Han Chong Toh
- Department of Medical Oncology, National Cancer Centre, Singapore
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Sun YJ, Lee ASG, Wong SY, Paton NI. Association of Mycobacterium tuberculosis Beijing genotype with tuberculosis relapse in Singapore. Epidemiol Infect 2005; 134:329-32. [PMID: 16207386 PMCID: PMC2870406 DOI: 10.1017/s095026880500525x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/21/2005] [Indexed: 11/07/2022] Open
Abstract
The relationship of Mycobacterium tuberculosis Beijing genotype with tuberculosis relapse was examined. Beijing strains were detected from 32 out of 45 (71%) relapsed cases and 148 out of 290 (51%) non-relapsed cases. Multivariate logistic regression analysis revealed that Beijing genotype was significantly associated with tuberculosis relapse (OR 2.64, 95% CI 1.30-5.34, P=0.005).
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Affiliation(s)
- Y-J Sun
- Department of Infectious Diseases, Tan Tock Seng Hospital, Singapore.
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Abstract
Evidence for deletion of 9q as a two-step process in chronic myeloid leukemia. Chronic myeloid leukemia (CML) is characterized by the Philadelphia translocation t(9;22)(q34;q11) resulting in the BCR/ABL fusion gene. Submicroscopic deletion of the derivative chromosome 9 occurs in a subset of these patients and is associated with poor prognosis. In the current study, we present two unusual cases of CML selected from a series of 54 consecutive cases. A detailed study using classical cytogenetics and fluorescence in situ hybridization (FISH) analysis was done using dual color extra signal FISH and whole chromosome paint in order to elucidate the mechanism of 9q deletion. One case had two clones on interphase FISH, one with and one without chromosome 9q deletion. The other case had two clones on both cytogenetic and FISH analyses, one with and one without a marker chromosome carrying chromosome 9q sequences. In this latter case, the clone with deletion of the derivative chromosome 9 comprised 21.1% at diagnosis, increasing to 36.8% after 11 months, suggesting a growth advantage. We report here evidence that deletions on 9q in CML may occur through breakage and rearrangement of chromosomes resulting in derivative chromosomes and either a marker chromosome or fragment/episome, followed by loss of chromosome material from the cell.
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Lee ASG, Lim IHK, Tang LLH, Wong SY. High frequency of mutations in the rpoB gene in rifampin-resistant clinical isolates of Mycobacterium tuberculosis from Singapore. J Clin Microbiol 2005; 43:2026-7. [PMID: 15815052 PMCID: PMC1081311 DOI: 10.1128/jcm.43.4.2026-2027.2005] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Sun YJ, Lee ASG, Ng ST, Ravindran S, Kremer K, Bellamy R, Wong SY, van Soolingen D, Supply P, Paton NI. Characterization of ancestral Mycobacterium tuberculosis by multiple genetic markers and proposal of genotyping strategy. J Clin Microbiol 2005; 42:5058-64. [PMID: 15528696 PMCID: PMC525198 DOI: 10.1128/jcm.42.11.5058-5064.2004] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sixty-eight ancestral Mycobacterium tuberculosis isolates were previously identified by using the tuberculosis-specific deletion 1 (TbD1) PCR and mycobacterial interspersed-repetitive-unit-variable-number tandem repeat (MIRU-VNTR) typing (Y. J. Sun, R. Bellamy, A. S. G. Lee, S. T. Ng, S. Ravindran, S.-Y. Wong, C. Locht, P. Supply, and N. I. Paton, J. Clin. Microbiol. 42:1986-1993, 2004). These TbD1(+) ancestral isolates were further characterized and typed in this study by IS6110 restriction fragment length polymorphism (RFLP) typing, VNTR typing using exact tandem repeats (VNTR-ETR), and spoligotyping of the direct-repeat region. To our knowledge, this is the first characterization of this genogroup by multiple genetic markers based on a fairly large sample size. In this genogroup, all spoligotypes were characterized by the absence of spacers 29 to 32 and 34. In addition, VNTR-ETR typing could add further resolution to the clustered isolates identified by MIRU-VNTR, and the combination of MIRU-VNTR and VNTR-ETR, called MIRU-ETR, showed the highest discriminatory power for these strains compared to IS6110 RFLP typing and spoligotyping alone. However, MIRU-ETR appeared to still cluster some probably epidemiologically unrelated strains, as judged by IS6110 RFLP divergence. Therefore, a typing strategy based on stepwise combination of MIRU-ETR and IS6110 RFLP is proposed to achieve maximal discrimination for unrelated TbD1(+) strains. This typing strategy may be useful in areas where TbD1(+) ancestral strains are prevalent.
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Affiliation(s)
- Yong-Jiang Sun
- Department of Infectious Diseases, Tan Tock Seng Hospital, Singapore 308433.
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Tien SL, Rudduck-Sivaswaren C, Lim P, Lim E, Lie DKH, Tan PHC, Lee ASG. High incidence of derivative chromosome arm 9q deletions in Asian chronic myelogenous leukemia. Genes Chromosomes Cancer 2005; 42:433-4. [PMID: 15645497 DOI: 10.1002/gcc.20146] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
MESH Headings
- Adolescent
- Adult
- Aged
- Chromosomes, Human, Pair 9
- Female
- Gene Deletion
- Genes, abl
- Humans
- In Situ Hybridization, Fluorescence
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/ethnology
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/genetics
- Male
- Middle Aged
- Singapore
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Lee ASG, Othman SNK, Ho YM, Wong SY. Novel mutations within the embB gene in ethambutol-susceptible clinical isolates of Mycobacterium tuberculosis. Antimicrob Agents Chemother 2004; 48:4447-9. [PMID: 15504879 PMCID: PMC525425 DOI: 10.1128/aac.48.11.4447-4449.2004] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Genetic analysis of the embB gene revealed mutations in 17 (68%) of 25 ethambutol (EMB) resistant isolates (M306I, M306V, M306L, Q497R) but also in 4 (20%) of 20 EMB-susceptible isolates of Mycobacterium tuberculosis, namely, an ATG-->ATM substitution resulting in M306I, G406N, and the novel alterations M423I and A659T.
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Affiliation(s)
- Ann S G Lee
- Division of Medical Sciences, National Cancer Centre, Singapore 169610, Republic of Singapore.
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Sun YJ, Bellamy R, Lee ASG, Ng ST, Ravindran S, Wong SY, Locht C, Supply P, Paton NI. Use of mycobacterial interspersed repetitive unit-variable-number tandem repeat typing to examine genetic diversity of Mycobacterium tuberculosis in Singapore. J Clin Microbiol 2004; 42:1986-93. [PMID: 15131159 PMCID: PMC404681 DOI: 10.1128/jcm.42.5.1986-1993.2004] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Strain typing using variable-number tandem repeats of mycobacterial interspersed repetitive units (MIRU-VNTR) is a powerful tool for studying the epidemiology and genetic relationships of Mycobacterium tuberculosis isolates. For this study, isolates from 291 patients in Singapore were genotyped by this method. One hundred sixty-six distinct MIRU-VNTR patterns were detected. One hundred sixty-two strains were grouped into 1 of 35 different MIRU-VNTR clusters and 131 isolates were unique. In this sample collection, 9 of the 12 MIRU-VNTR loci were moderately or highly discriminative according to their allelic diversities. The Hunter-Gaston discriminatory index was 0.975, indicating the high power of discrimination of MIRU-VNTR typing. By direct comparisons with previously typed MIRU-VNTR patterns and by genetic relationship analyses, we could identify and clearly define four epidemic groups of M. tuberculosis in our sample, corresponding to the W/Beijing, East-Africa-Indian, Haarlem, and Delhi genotype families. Furthermore, MIRU-VNTR typing was able to clearly distinguish ancestral and modern M. tuberculosis strains as defined by TbD1 genomic deletion analysis. These results indicate that MIRU-VNTR typing can be a useful first-line tool for studying the genetic diversity of M. tuberculosis isolates in a large urban setting such as Singapore.
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Affiliation(s)
- Yong-Jiang Sun
- Department of Infectious Diseases, Tan Tock Seng Hospital, Singapore, Republic of Singapore.
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Lee ASG, Ho GH, Oh PC, Balram C, Ooi LL, Lim DTH, Wong CY, Hong GS. Founder mutation in the BRCA1 gene in Malay breast cancer patients from Singapore. Hum Mutat 2003; 22:178. [PMID: 12872263 DOI: 10.1002/humu.9162] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The mutation spectrum of the BRCA1 gene among ethnic groups from Asia has not been well studied. We investigated the frequency of mutations in the BRCA1 gene among Malay breast cancer patients from Singapore, independent of family history. By using the protein truncation test (PTT) and direct sequencing, BRCA1 mutations were detected in 6 of 49 (12.2%) unrelated patients. Four novel missense mutations in exon 11, T557A (1788A>G), T582A (1863A>G), N656S (2086A>G) and P684S (2169C>T) were identified in one patient. Two patients had missense mutations in exon 23, V1809A (5545T>C), which has been previously detected in individuals from Central and Eastern Europe. Three unrelated patients had the deleterious 2846insA frameshift mutation in exon 11. Methylation specific PCR (MSP) of the promoter region of the BRCA1 gene detected hypermethylation of tumor DNA in an additional 2 patients. Haplotype analysis using the microsatellite markers D17S855, D17S1323 and D17S1325 revealed a common haplotype for the three unrelated patients and their three relatives with the 2846insA mutation. These findings strongly suggest that the 2846insA mutation, the most common deleterious mutation in this study, may possibly be a founder mutation in breast cancer patients of Malay ethnic background.
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Affiliation(s)
- Ann S G Lee
- Laboratory of Molecular Oncology, Division of Medical Sciences, National Cancer Centre, Singapore.
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Lee ASG, Tang LLH, Lim IHK, Wong SY. Characterization of pyrazinamide and ofloxacin resistance among drug resistant Mycobacterium tuberculosis isolates from Singapore. Int J Infect Dis 2002; 6:48-51. [PMID: 12044302 DOI: 10.1016/s1201-9712(02)90136-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
OBJECTIVES To evaluate rapid molecular approaches for the detection of pyrazinamide (PZA) and ofloxacin resistance, by screening 100 known drug-resistant Mycobacterium tuberculosis isolates. METHODS Mycobacterium tuberculosis isolates were tested for phenotypic resistance to pyrazinamide and ofloxacin using the BACTEC 460 radiometric method and the E-test, respectively. Mutation screening was done by amplifying the pncA, gyrA, and gyrB genes by the polymerase chain reaction (PCR) and direct automated sequencing. RESULTS Twelve isolates were PZA-resistant and 8 of 12 (66.7%) isolates had missense mutations or deletions at the pncA gene, suggesting that mutation or deletion at the pncA gene is the major molecular mechanism of PZA resistance among the Singaporean isolates. Using the E-test, 48 isolates were resistant to ofloxacin, with minimum inhibitory concentrations of 4 microg/mL or higher. No mutations were observed at the quinolone resistance-determining region (QRDR) of gyrA in all isolates. At the QRDR of gyrB, mutations were present in 1 of 48 ofloxacin-resistant isolates and 0 of 19 ofloxacin-susceptible isolates. CONCLUSIONS In Singapore, genotypic analysis of resistance to PZA and ofloxacin is inadequate and should be complemented by conventional methods.
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Affiliation(s)
- Ann S G Lee
- Department of Clinical Research, Singapore General Hospital, Singapore.
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Lee ASG, Tang LLH, Lim IHK, Bellamy R, Wong SY. Discrimination of single-copy IS6110 DNA fingerprints of Mycobacterium tuberculosis isolates by high-resolution minisatellite-based typing. J Clin Microbiol 2002; 40:657-9. [PMID: 11825989 PMCID: PMC153360 DOI: 10.1128/jcm.40.2.657-659.2002] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Seven isoniazid-resistant isolates with mutations in the NADH dehydrogenase (ndh) gene were molecularly typed by IS6110-based restriction fragment length polymorphism analysis. All seven isolates with the R268H mutation had identical 1.4-kb IS6110 fingerprints. High-resolution minisatellite-based typing discriminated five of these isolates; two isolates were identical.
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Affiliation(s)
- Ann S G Lee
- Department of Clinical Research, Singapore General Hospital, Singapore 169608.
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Chow WC, Lee ASG, Seo YC, Tan CK, Ng HS. Prevalence of hepatitis G virus infection in patients with liver diseases in Singapore. Singapore Med J 2002; 43:067-9. [PMID: 11993892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
The prevalence of hepatitis G virus (HGV) infection in patients with liver diseases in Singapore and its pathogenic role in these patients was studied. One hundred and forty-eight patients who had chronic hepatitis or acute non A-E hepatitis were studied. Presence of HGV RNA was determined by nested polymerase chain reaction of the 5'non-coding region of the virus in all the patients. Hepatitis G IgG antibody to the envelope (E2) antigen was tested with an enzyme immunoassay (Boehringer Mannheim, Singapore) in 76 of them. Most patients (93%) were ethnically Chinese, predominantly males (74%) and chronic hepatitis B (72%) patients. Others had chronic hepatitis C (19%) or cryptogenic cirrhosis (6%). Four patients had acute non A-E hepatitis. HGV RNA and anti-HGenv were present in 3.5% and 8.3% of those with chronic liver disease. HGV infection did not account for any of the acute non A-E hepatitis and most of the cryptogenic cirrhosis.
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Affiliation(s)
- W C Chow
- Department of Gastroenterology, Singapore General Hospital, Singapore.
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