Choonnam Ong - Academia.edu (original) (raw)

Papers by Choonnam Ong

JNCI: Journal of the National Cancer Institute, 2006

Background: Retinol and its derivatives (retinoids), which have antioxidant activity and promote ... more Background: Retinol and its derivatives (retinoids), which have antioxidant activity and promote cell differentiation, may protect against the development of hepatocellular carcinoma (HCC) by controlling hepatocellular differentiation and re ducing infl ammatory responses. Methods: We examined prospectively the relationship between prediagnostic serum concentrations of retinol, α-carotene; β-carotene; β-cryptoxanthin; lutein; lycopene; zeaxanthin; α-, γ-, and δ-tocopherols; and selenium and the risk of developing HCC among 213 patients with HCC and 1087 matched control subjects from a cohort of 18 244 men in Shanghai, China, who were monitored from 1986 through 2001. Odds ratios (ORs) and 95% confi dence intervals (CIs) for men by quartile of serum concentrations of micronutrients were estimated by using logistic regression with adjustment for cigarette smoking status, alcohol intake, self-reported history of physician-diagnosed hepatitis or liver cirrhosis at recruitment, and seropositivity for hepatitis B surface antigen (HBsAg). All statistical tests were two-sided. Results: Men with high prediagnostic serum retinol levels had a lower risk of HCC than men in the lowest quartile (Q2 versus Q1, OR = 0.37, 95% CI = 0.22 to 0.61; Q3 versus Q1, OR = 0.30, 95% CI = 0.17 to 0.50; and Q4 versus Q1, OR = 0.13, 95% CI = 0.06 to 0.26; P trend <.001). A statistically significant interaction was observed between retinol and HBsAg seropositivity on HCC risk; HBsAg-positive men in the lowest tertile of retinol had a greater than 70-fold higher risk (OR = 72.7, 95% CI = 31.6 to 167.4) of HCC than HBsAgnegative men in the highest tertile of retinol (P interaction = .018). No independent effect of serum levels of α-carotene; β-carotene; β-cryptoxanthin; lutein; lycopene; zeaxanthin; α-, γ-, and δ-tocopherols; or selenium on HCC risk were observed. Conclusion: High prediagnostic serum level of retinol is associated with a decreased risk of HCC in this population. [J Natl Cancer Inst 2006;98:482-90] Chronic infection with hepatitis B virus (HBV) is by far the most important risk factor for hepatocellular carcinoma (HCC) in humans and is the primary cause of this cancer in high-risk areas, including China and Africa (1 , 2). Chronic infection with hepatitis C virus (HCV) is another risk factor for HCC and has an increasingly prominent role in the development of HCC in countries where rates of infection with HBV are relatively low (3). Other environmental risk factors for HCC include dietary afl atoxin, which plays a prominent role in high-risk areas such as China and Africa; excessive alcohol intake; cigarette smoking; diabetes; and obesity (4-6). Carcinogenesis is characterized by aberrant cell differentiation (7). Retinol and its derivatives (retinoids) have vital roles in controlling cellular growth and differentiation (8). Retinoids

Clinical Chemistry, 2003

Background: Epidemiologic evidence suggests that the concentrations of antioxidant vitamins in hu... more Background: Epidemiologic evidence suggests that the concentrations of antioxidant vitamins in human plasma may play an important role in numerous chronic diseases, such as cancer and cardiovascular disease. However, methods for simultaneous measurement of these antioxidants are scarce. We developed and validated a new HPLC method for simultaneous determination of these vitamers in human plasma that uses a novel column-switching approach. Methods: The new method uses liquid–liquid extraction and isocratic separation with two monomeric C18 columns maintained at 35 and 4 °C coupled with ultraviolet–visible and fluorometric detection. This method could separate 14 vitamers and 3 internal standards within 27 min. No additional modifier was required; the mobile phase was acetonitrile–methanol (65:35 by volume), and the flow rate was 1 mL/min. Results: For photodiode array detection, the detection limits (signal-to-noise ratio >3) were 0.02 mg/L for β-carotene, lutein, zeaxanthin, and ...

Biomaterials, 2010

Impurities in the synthesized gold nanoparticle (AuNP) solution are systematically identified fol... more Impurities in the synthesized gold nanoparticle (AuNP) solution are systematically identified followed by determining an optimal purification process and evaluating the stability as well as oxidation state of the purified 20-nm AuNPs. Quantified non-AuNP components and a newly speciated byproduct (acetate) complete the stoichiometric equation of AuNP synthesis through the citrate reduction method. Among the five tested centrifugation forces (3000e11,000g) and durations (10e60 min), optimal purification of AuNPs was achieved by centrifugation operating at 7000g for 20 min which satisfactorily recovers w80% of AuNPs without detectable impurities. Storage in the dark at 4 C prolongs the stability of the purified AuNP suspensions up to 20 days. AuNPs employed in this study persist in their atomic status without being oxidized, even after they were aerosolized in air or heated at 500 C. This work demonstrates how impurities are identified and removed, and the purified AuNPs can be a reference material to evaluate toxicity or reactivity of other engineered nanomaterials.

Cancer Letters, 2004

Parthenolide is one of the main components responsible for the anti-inflammatory property of Feve... more Parthenolide is one of the main components responsible for the anti-inflammatory property of Feverfew. Recently, parthenolide has shown to induce apoptosis in cancer cells. Here we further studied the mechanism of parthenolide-induced apoptosis by focusing on the role of intracellular thiols and calcium in a human colorectal cancer cell, COLO 205. Parthenolide rapidly depleted intracellular thiols, including both free glutathione

Cancer letters, 2000

Salvia miltiorrhiza (SM) is a traditional Chinese herbal medicine, commonly used to treat liver d... more Salvia miltiorrhiza (SM) is a traditional Chinese herbal medicine, commonly used to treat liver diseases in China for centuries. Several earlier studies have indicated that SM exhibits anti-tumor properties, but its mechanism remains to be elucidated. In this study, we evaluated the molecular mechanism of SM in a human hepatoma cell line, HepG(2). Our results show that SM exerted clear cytotoxic effects, and strongly inhibited the proliferation of HepG(2) cells. It was also observed that SM treatment caused apoptotic cell death as evaluated by: (a), morphological changes by using acridine orange/ethidium bromide staining; (b), DNA fragmentation by TdT-mediated dUTP nick end labeling (TUNEL); and (c), sub-G(1) cell analysis. Furthermore, depletion of intracellular glutathione (GSH) and reduction of mitochondrial membrane potential were found to be involved in the initiation of apoptosis by SM.

JNCI: Journal of the National Cancer Institute, 2006

Background: Retinol and its derivatives (retinoids), which have antioxidant activity and promote ... more Background: Retinol and its derivatives (retinoids), which have antioxidant activity and promote cell differentiation, may protect against the development of hepatocellular carcinoma (HCC) by controlling hepatocellular differentiation and re ducing infl ammatory responses. Methods: We examined prospectively the relationship between prediagnostic serum concentrations of retinol, α-carotene; β-carotene; β-cryptoxanthin; lutein; lycopene; zeaxanthin; α-, γ-, and δ-tocopherols; and selenium and the risk of developing HCC among 213 patients with HCC and 1087 matched control subjects from a cohort of 18 244 men in Shanghai, China, who were monitored from 1986 through 2001. Odds ratios (ORs) and 95% confi dence intervals (CIs) for men by quartile of serum concentrations of micronutrients were estimated by using logistic regression with adjustment for cigarette smoking status, alcohol intake, self-reported history of physician-diagnosed hepatitis or liver cirrhosis at recruitment, and seropositivity for hepatitis B surface antigen (HBsAg). All statistical tests were two-sided. Results: Men with high prediagnostic serum retinol levels had a lower risk of HCC than men in the lowest quartile (Q2 versus Q1, OR = 0.37, 95% CI = 0.22 to 0.61; Q3 versus Q1, OR = 0.30, 95% CI = 0.17 to 0.50; and Q4 versus Q1, OR = 0.13, 95% CI = 0.06 to 0.26; P trend <.001). A statistically significant interaction was observed between retinol and HBsAg seropositivity on HCC risk; HBsAg-positive men in the lowest tertile of retinol had a greater than 70-fold higher risk (OR = 72.7, 95% CI = 31.6 to 167.4) of HCC than HBsAgnegative men in the highest tertile of retinol (P interaction = .018). No independent effect of serum levels of α-carotene; β-carotene; β-cryptoxanthin; lutein; lycopene; zeaxanthin; α-, γ-, and δ-tocopherols; or selenium on HCC risk were observed. Conclusion: High prediagnostic serum level of retinol is associated with a decreased risk of HCC in this population. [J Natl Cancer Inst 2006;98:482-90] Chronic infection with hepatitis B virus (HBV) is by far the most important risk factor for hepatocellular carcinoma (HCC) in humans and is the primary cause of this cancer in high-risk areas, including China and Africa (1 , 2). Chronic infection with hepatitis C virus (HCV) is another risk factor for HCC and has an increasingly prominent role in the development of HCC in countries where rates of infection with HBV are relatively low (3). Other environmental risk factors for HCC include dietary afl atoxin, which plays a prominent role in high-risk areas such as China and Africa; excessive alcohol intake; cigarette smoking; diabetes; and obesity (4-6). Carcinogenesis is characterized by aberrant cell differentiation (7). Retinol and its derivatives (retinoids) have vital roles in controlling cellular growth and differentiation (8). Retinoids

Clinical Chemistry, 2003

Background: Epidemiologic evidence suggests that the concentrations of antioxidant vitamins in hu... more Background: Epidemiologic evidence suggests that the concentrations of antioxidant vitamins in human plasma may play an important role in numerous chronic diseases, such as cancer and cardiovascular disease. However, methods for simultaneous measurement of these antioxidants are scarce. We developed and validated a new HPLC method for simultaneous determination of these vitamers in human plasma that uses a novel column-switching approach. Methods: The new method uses liquid–liquid extraction and isocratic separation with two monomeric C18 columns maintained at 35 and 4 °C coupled with ultraviolet–visible and fluorometric detection. This method could separate 14 vitamers and 3 internal standards within 27 min. No additional modifier was required; the mobile phase was acetonitrile–methanol (65:35 by volume), and the flow rate was 1 mL/min. Results: For photodiode array detection, the detection limits (signal-to-noise ratio >3) were 0.02 mg/L for β-carotene, lutein, zeaxanthin, and ...

Biomaterials, 2010

Impurities in the synthesized gold nanoparticle (AuNP) solution are systematically identified fol... more Impurities in the synthesized gold nanoparticle (AuNP) solution are systematically identified followed by determining an optimal purification process and evaluating the stability as well as oxidation state of the purified 20-nm AuNPs. Quantified non-AuNP components and a newly speciated byproduct (acetate) complete the stoichiometric equation of AuNP synthesis through the citrate reduction method. Among the five tested centrifugation forces (3000e11,000g) and durations (10e60 min), optimal purification of AuNPs was achieved by centrifugation operating at 7000g for 20 min which satisfactorily recovers w80% of AuNPs without detectable impurities. Storage in the dark at 4 C prolongs the stability of the purified AuNP suspensions up to 20 days. AuNPs employed in this study persist in their atomic status without being oxidized, even after they were aerosolized in air or heated at 500 C. This work demonstrates how impurities are identified and removed, and the purified AuNPs can be a reference material to evaluate toxicity or reactivity of other engineered nanomaterials.

Cancer Letters, 2004

Parthenolide is one of the main components responsible for the anti-inflammatory property of Feve... more Parthenolide is one of the main components responsible for the anti-inflammatory property of Feverfew. Recently, parthenolide has shown to induce apoptosis in cancer cells. Here we further studied the mechanism of parthenolide-induced apoptosis by focusing on the role of intracellular thiols and calcium in a human colorectal cancer cell, COLO 205. Parthenolide rapidly depleted intracellular thiols, including both free glutathione

Cancer letters, 2000

Salvia miltiorrhiza (SM) is a traditional Chinese herbal medicine, commonly used to treat liver d... more Salvia miltiorrhiza (SM) is a traditional Chinese herbal medicine, commonly used to treat liver diseases in China for centuries. Several earlier studies have indicated that SM exhibits anti-tumor properties, but its mechanism remains to be elucidated. In this study, we evaluated the molecular mechanism of SM in a human hepatoma cell line, HepG(2). Our results show that SM exerted clear cytotoxic effects, and strongly inhibited the proliferation of HepG(2) cells. It was also observed that SM treatment caused apoptotic cell death as evaluated by: (a), morphological changes by using acridine orange/ethidium bromide staining; (b), DNA fragmentation by TdT-mediated dUTP nick end labeling (TUNEL); and (c), sub-G(1) cell analysis. Furthermore, depletion of intracellular glutathione (GSH) and reduction of mitochondrial membrane potential were found to be involved in the initiation of apoptosis by SM.