Chuen SEng Tan | NUS (original) (raw)

Papers by Chuen SEng Tan

International Journal of Cancer, 2005

Breast cancer incidence in Sweden has always been approximately twice as high as in Singapore. In... more Breast cancer incidence in Sweden has always been approximately twice as high as in Singapore. In recent years, this difference is limited to postmenopausal women. The aim of this study was to explore the reasons behind these differences through the use of age-period-cohort modeling. This population-based study included all breast cancer cases reported to the Swedish and the Singapore cancer registries from 1968 to 1997, with a total of 135,581 Swedish and 10,716 Singaporean women. Poisson regression using age-period and age-cohort models was used to determine the effects of age at diagnosis, calendar period and birth cohort. Incidence rate ratios were used to summarize these effects. An age-cohort model provided the best fit to the data in both countries, indicating that changes over lifetime, rather than recent differences in medical surveillance, might account for the observed differences in these 2 populations. The changes over birth cohort were much greater among Singaporean women. The relative effect of age was very similar in the 2 countries. Analyses show that age and cohort effects may explain the differences in trends of female breast cancer incidence between Sweden and Singapore. The larger cohort effect seen in Singaporean women may be attributed to more rapid changes in reproduction and lifestyle patterns than that of Swedish women during the period studied. The incidence of breast cancer in postmenopausal women in Singapore will probably continue to rise in the coming decades to match the current Swedish rates.

Atherosclerosis, 2006

Peroxisome proliferators activated receptor ␣ (PPAR␣) regulates the transcription of several prot... more Peroxisome proliferators activated receptor ␣ (PPAR␣) regulates the transcription of several proteins involved in human lipoprotein metabolism. We screened the PPARA locus for polymorphisms in 20 unrelated subjects from each of three ethnic groups (Chinese, Malays and Asian Indians). Only the V227A polymorphism was observed. We genotyped 4248 subjects (2899 Chinese, 761 Malay and 588 Asian Indians) and found allele frequencies for the A227 allele of 0.04 in Chinese, 0.006 in Malays and 0.003 in Asian Indians. We examined the associations between this polymorphism and serum lipid concentrations in Chinese. In women, but not in men, the presence of the A227 allele was associated with lower serum concentrations of total cholesterol [5.38 mmol/l (95%CI: 5.22-5.54) versus 5.21 mmol/l (95%CI: 4.99-5.43), p = 0.047] and triglycerides [1.19 mmol/l (95%CI: 1.10-1.28) versus 1.09 mmol/l (95%CI: 0.98-1.21), p = 0.048]. We also found that the V227A polymorphism modulates the association between dietary polyunsaturated fatty acid intake and serum high density lipoprotein concentration (p-value for interaction = 0.049). Our findings implicate PPAR␣ in the lipid lowering associated with diets high in PUFA and suggests that genetic variation at the PPARA locus may determine the lipid response to changes in PUFA intake. (E.S. Tai). glucose metabolism, the inflammatory response and energy homeostasis . The PPARA locus is polymorphic in humans. Several of these polymorphisms have been associated with variation in obesity, serum lipid concentrations and coronary artery disease .

BMC Cancer, 2006

Background From 1968 to 2002, Singapore experienced an almost three-fold increase in breast cance... more Background From 1968 to 2002, Singapore experienced an almost three-fold increase in breast cancer incidence. This increase appeared to be different across the three main ethnic groups: Chinese, Malays and Indians. This paper used age-period-cohort (APC) modelling, to determine the effects of age at diagnosis, calendar period, and birth cohort on breast cancer incidence for each ethnic group. Methods This study included all breast cancer cases (n = 15,269) in the three ethnic groups, reported to the Singapore Cancer Registry from 1968 to 2002 between the ages 25 to 79. Age-specific fertility rates from the Department of Statistics were used to explore the role of fertility. Results In the 1970s, Indian women had the highest age-standardized breast cancer but by the mid-1980s the highest rates were seen among the Chinese. Remarkable differences were seen in the age-specific incidence rates by ethnic groups. After age 49, the incidence rates for the Chinese and Malays leveled off whereas it continued to rise in the Indians. While our analyses provided some evidence that an age-drift model described the trend seen in the Indians, age-period-cohort model and age-cohort model had the best fit for the Chinese and Malays aged 25 to 79 respectively. Overall, Chinese and Malay women born in later cohorts were at increased risk of developing breast cancer relative to their counterparts in the earlier cohorts. The three ethnic groups experienced similar changes in their fertility in the 1970s, which likely explained much of the increase in their breast cancer incidence but not the ethnic differences. There was a stronger inverse association between total fertility rate and pre-menopausal breast cancer incidence in the Chinese and Malays than the Indians. Conclusion The observed dissimilarity among ethnic groups suggests ethnic differences in exposure or response to certain risk factors. It is likely that longer and subtler differences in childbearing trends and other risk factors may further explain these ethnic differences.

Bioinformatics/computer Applications in The Biosciences, 2006

Motivation: There is a well-recognized potential of protein expression profiling using the surfac... more Motivation: There is a well-recognized potential of protein expression profiling using the surface-enhanced laser desorption and ionization technology for discovering biomarkers that can be applied in clinical diagnosis, prognosis and therapy prediction. The pre-processing of the raw data, however, is still problematic. Methods: We focus on the peak detection step, where the standard method is marked by poor specificity. Currently, scientists need to inspect individual spectra visually and laboriously in order to verify that spectral peaks identified by the standard method are real. Motivated by this multi-spectral process, we investigate an analytical approach-called RS for 'regions of significance'-that reduces the data to a single spectrum of F-statistics capturing significant variability between spectra. To account for multiple testing, we use a false discovery rate criterion for identifying potentially interesting proteins. Results: We show that RS has better operating characteristics than several existing methods and demonstrate routine applications on a number of large datasets. Availability: RS is implemented in an R package called ProSpect which is available at

International Journal of Cancer, 2005

Breast cancer incidence in Sweden has always been approximately twice as high as in Singapore. In... more Breast cancer incidence in Sweden has always been approximately twice as high as in Singapore. In recent years, this difference is limited to postmenopausal women. The aim of this study was to explore the reasons behind these differences through the use of age-period-cohort modeling. This population-based study included all breast cancer cases reported to the Swedish and the Singapore cancer registries from 1968 to 1997, with a total of 135,581 Swedish and 10,716 Singaporean women. Poisson regression using age-period and age-cohort models was used to determine the effects of age at diagnosis, calendar period and birth cohort. Incidence rate ratios were used to summarize these effects. An age-cohort model provided the best fit to the data in both countries, indicating that changes over lifetime, rather than recent differences in medical surveillance, might account for the observed differences in these 2 populations. The changes over birth cohort were much greater among Singaporean women. The relative effect of age was very similar in the 2 countries. Analyses show that age and cohort effects may explain the differences in trends of female breast cancer incidence between Sweden and Singapore. The larger cohort effect seen in Singaporean women may be attributed to more rapid changes in reproduction and lifestyle patterns than that of Swedish women during the period studied. The incidence of breast cancer in postmenopausal women in Singapore will probably continue to rise in the coming decades to match the current Swedish rates.

Atherosclerosis, 2006

Peroxisome proliferators activated receptor ␣ (PPAR␣) regulates the transcription of several prot... more Peroxisome proliferators activated receptor ␣ (PPAR␣) regulates the transcription of several proteins involved in human lipoprotein metabolism. We screened the PPARA locus for polymorphisms in 20 unrelated subjects from each of three ethnic groups (Chinese, Malays and Asian Indians). Only the V227A polymorphism was observed. We genotyped 4248 subjects (2899 Chinese, 761 Malay and 588 Asian Indians) and found allele frequencies for the A227 allele of 0.04 in Chinese, 0.006 in Malays and 0.003 in Asian Indians. We examined the associations between this polymorphism and serum lipid concentrations in Chinese. In women, but not in men, the presence of the A227 allele was associated with lower serum concentrations of total cholesterol [5.38 mmol/l (95%CI: 5.22-5.54) versus 5.21 mmol/l (95%CI: 4.99-5.43), p = 0.047] and triglycerides [1.19 mmol/l (95%CI: 1.10-1.28) versus 1.09 mmol/l (95%CI: 0.98-1.21), p = 0.048]. We also found that the V227A polymorphism modulates the association between dietary polyunsaturated fatty acid intake and serum high density lipoprotein concentration (p-value for interaction = 0.049). Our findings implicate PPAR␣ in the lipid lowering associated with diets high in PUFA and suggests that genetic variation at the PPARA locus may determine the lipid response to changes in PUFA intake. (E.S. Tai). glucose metabolism, the inflammatory response and energy homeostasis . The PPARA locus is polymorphic in humans. Several of these polymorphisms have been associated with variation in obesity, serum lipid concentrations and coronary artery disease .

BMC Cancer, 2006

Background From 1968 to 2002, Singapore experienced an almost three-fold increase in breast cance... more Background From 1968 to 2002, Singapore experienced an almost three-fold increase in breast cancer incidence. This increase appeared to be different across the three main ethnic groups: Chinese, Malays and Indians. This paper used age-period-cohort (APC) modelling, to determine the effects of age at diagnosis, calendar period, and birth cohort on breast cancer incidence for each ethnic group. Methods This study included all breast cancer cases (n = 15,269) in the three ethnic groups, reported to the Singapore Cancer Registry from 1968 to 2002 between the ages 25 to 79. Age-specific fertility rates from the Department of Statistics were used to explore the role of fertility. Results In the 1970s, Indian women had the highest age-standardized breast cancer but by the mid-1980s the highest rates were seen among the Chinese. Remarkable differences were seen in the age-specific incidence rates by ethnic groups. After age 49, the incidence rates for the Chinese and Malays leveled off whereas it continued to rise in the Indians. While our analyses provided some evidence that an age-drift model described the trend seen in the Indians, age-period-cohort model and age-cohort model had the best fit for the Chinese and Malays aged 25 to 79 respectively. Overall, Chinese and Malay women born in later cohorts were at increased risk of developing breast cancer relative to their counterparts in the earlier cohorts. The three ethnic groups experienced similar changes in their fertility in the 1970s, which likely explained much of the increase in their breast cancer incidence but not the ethnic differences. There was a stronger inverse association between total fertility rate and pre-menopausal breast cancer incidence in the Chinese and Malays than the Indians. Conclusion The observed dissimilarity among ethnic groups suggests ethnic differences in exposure or response to certain risk factors. It is likely that longer and subtler differences in childbearing trends and other risk factors may further explain these ethnic differences.

Bioinformatics/computer Applications in The Biosciences, 2006

Motivation: There is a well-recognized potential of protein expression profiling using the surfac... more Motivation: There is a well-recognized potential of protein expression profiling using the surface-enhanced laser desorption and ionization technology for discovering biomarkers that can be applied in clinical diagnosis, prognosis and therapy prediction. The pre-processing of the raw data, however, is still problematic. Methods: We focus on the peak detection step, where the standard method is marked by poor specificity. Currently, scientists need to inspect individual spectra visually and laboriously in order to verify that spectral peaks identified by the standard method are real. Motivated by this multi-spectral process, we investigate an analytical approach-called RS for 'regions of significance'-that reduces the data to a single spectrum of F-statistics capturing significant variability between spectra. To account for multiple testing, we use a false discovery rate criterion for identifying potentially interesting proteins. Results: We show that RS has better operating characteristics than several existing methods and demonstrate routine applications on a number of large datasets. Availability: RS is implemented in an R package called ProSpect which is available at