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Letter regarding "CD95 rs1800682 polymorphism and cervical cancer risk: evidence from a meta-analysis" by Zhang et al

Tan SC

Tumour Biol., 2015 Nov;36(11):8275-6.
PMID: 26515334 DOI: 10.1007/s13277-015-4330-1
Use of Arbitrary Reference Genes May Lead to Misleading Conclusions

Tan SC

Gynecol. Obstet. Invest., 2019;84(5):519-520.
PMID: 31269498 DOI: 10.1159/000501684
Low penetrance genetic polymorphisms as potential biomarkers for colorectal cancer predisposition

Tan SC

J Gene Med, 2018 04;20(4):e3010.
PMID: 29424105 DOI: 10.1002/jgm.3010

Colorectal cancer is a leading form of cancer in both males and females. Early detection of individuals at risk of colorectal cancer allows proper treatment and management of the disease to be implemented, which can potentially reduce the burden of colorectal cancer incidence, morbidity and mortality. In recent years, the role of genetic susceptibility factors in mediating predisposition to colorectal cancer has become more and more apparent. Identification of high-frequency, low-penetrance genetic polymorphisms associated with the cancer has therefore emerged as an important approach which can potentially aid prediction of colorectal cancer risk. However, the overwhelming amount of genetic epidemiology data generated over the past decades has made it difficult for one to assimilate the information and determine the exact genetic polymorphisms that can potentially be used as biomarkers for colorectal cancer. This review comprehensively consolidates, based primarily on results from meta-analyses, the recent progresses in the search of colorectal cancer-associated genetic polymorphisms, and discusses the possible mechanisms involved.
Genetic susceptibility to cervical cancer: role of common polymorphisms in apoptosis-related genes

Tan SC, Ankathil R

Tumour Biol., 2015 Sep;36(9):6633-44.
PMID: 26242271 DOI: 10.1007/s13277-015-3868-2

Cervical cancer is a common malignancy which poses a significant health burden among women, especially those living in the developing countries. Although human papillomavirus (HPV) infection has been unequivocally implicated in the etiopathogenesis of the cancer, it alone is not adequate to contribute to the malignant transformation of cervical cells. Most HPV infections regress spontaneously, and only a small proportion of women have persistent infections which eventually lead to malignancy. This suggests that interplays between HPV infection and other cofactors certainly exist during the process of cervical carcinogenesis, which synergistically contribute to the differential susceptibility of an individual to the malignancy. Undoubtedly, host genetic factors represent a major element involved in such a synergistic interaction, and accumulating evidence suggests that polymorphisms in apoptosis-related genes play an important role in the genetic susceptibility to cervical cancer. This review consolidates the recent literatures on the role of common polymorphisms in apoptosis-related genes in genetic susceptibility to cervical cancer.
Genetic polymorphisms as potential pharmacogenetic biomarkers for platinum-based chemotherapy in non-small cell lung cancer

Sito H, Tan SC

Mol Biol Rep, 2024 Jan 13;51(1):102.
PMID: 38217759 DOI: 10.1007/s11033-023-08915-2

Platinum-based chemotherapy (PBC) is a widely used treatment for various solid tumors, including non-small cell lung cancer (NSCLC). However, its efficacy is often compromised by the emergence of drug resistance in patients. There is growing evidence that genetic variations may influence the susceptibility of NSCLC patients to develop resistance to PBC. Here, we provide a comprehensive overview of the mechanisms underlying platinum drug resistance and highlight the important role that genetic polymorphisms play in this process. This paper discussed the genetic variants that regulate DNA repair, cellular movement, drug transport, metabolic processing, and immune response, with a focus on their effects on response to PBC. The potential applications of these genetic polymorphisms as predictive indicators in clinical practice are explored, as are the challenges associated with their implementation.
Fulltext DNA, RNA, and protein extraction: the past and the present

Tan SC, Yiap BC

J Biomed Biotechnol, 2009;2009:574398.
PMID: 20011662 DOI: 10.1155/2009/574398

Extraction of DNA, RNA, and protein is the basic method used in molecular biology. These biomolecules can be isolated from any biological material for subsequent downstream processes, analytical, or preparative purposes. In the past, the process of extraction and purification of nucleic acids used to be complicated, time-consuming, labor-intensive, and limited in terms of overall throughput. Currently, there are many specialized methods that can be used to extract pure biomolecules, such as solution-based and column-based protocols. Manual method has certainly come a long way over time with various commercial offerings which included complete kits containing most of the components needed to isolate nucleic acid, but most of them require repeated centrifugation steps, followed by removal of supernatants depending on the type of specimen and additional mechanical treatment. Automated systems designed for medium-to-large laboratories have grown in demand over recent years. It is an alternative to labor-intensive manual methods. The technology should allow a high throughput of samples; the yield, purity, reproducibility, and scalability of the biomolecules as well as the speed, accuracy, and reliability of the assay should be maximal, while minimizing the risk of cross-contamination.
Fulltext Budget impact analysis of wider adoption of biphasic insulin Aspart (Biasp) in the treatment of type 2 diabetes mellitus (T2DM): a perspective of patients treated by public providers in Singapore. [Abstract]

Tan SC, Matzen P, Khoo SP

Value Health, 2014 Nov;17(7):A743.
PMID: 27202681 DOI: 10.1016/j.jval.2014.08.153

Objectives
Economic evaluations of BIAsp have been published in the context of different countries. This study aimed to evaluate the financial impact from a perspective of patients treated by public providers of different adoption rates of Biphasic Insulin Aspart (BIAsp; NovoMix 30 FlexPen®) versus Biphasic Human Insulin (BHI; Mixtard Penfill®) in treating T2DM.
Methods
An Excel based 5-year budget impact model was built to estimate insulin treated patients by public providers using the local prevalence data. The published demographic, efficacy and adverse event data for ASEAN subgroup analyses of A1chieve study was applied. Both insulin acquisition costs and medical costs for major hypoglycaemia and other complications were applied with a 3% discount rate to the estimated corresponding incidence rates derived from the UKPDS equations. The projected adoption rates were based on the 2013 utilisation volume data. Other local specific considerations e.g. subsidized selling prices and co-payments were included in the analyses for an assumed size of eligible patients. Sensitivity analyses were conducted.
Results
The adoption rates of BIAsp were assumed to increase from 23.6% in 2013 to 30% or 36.5% in 2018 for base case and upside scenario, respectively. In comparison to base case scenario, increases in adoption rate of BIAsp were associated with a cumulative increase up to slightly greater than S$ 2.02M in insulin acquisition cost but a potential cumulative net saving up to approximately S$0.92M in overall total costs over 5 years, attributing to subsidized selling price of BIAsp assuming it is included standard drug list and its significantly lower major hypoglycaemia risk, respectively. Cost savings were predicted for other complications.
Conclusions
The wider adoption of BIAsp was predicted to result in net cost savings from patient perspective in Singapore. More cost saving would be estimated in analyses with reduced productivity loss from a societal perspective.
Fulltext Budget impact analysis of biphasic insulin Aspart in the treatment of type 2 diabetes mellitus In Malaysia: a public payer perspective. [Abstract]

Tan SC, Matzen P, Yeo LN

Value Health, 2014 Nov;17(7):A743.
PMID: 27202679 DOI: 10.1016/j.jval.2014.08.151

Objectives
Budget impact analysis (BIA) is a useful tool for reimbursement decision-makers in health technology assessments by authorities across different countries. This study aimed to evaluate the financial impact from the Ministry of Health (MOH) perspective of different adoption rates of Biphasic Insulin Aspart (BIAsp) versus Biphasic Human Insulin (BHI) in treating type 2 diabetes mellitus.
Methods
An Excel basfed 5-year budget impact model was built to estimate insulin treated patients by public providers using local prevalence data. The published demographic, efficacy and adverse event data for ASEAN subgroup analyses of A1chieve study was applied. Both insulin acquisition costs and other medical costs for complications e.g. major hypoglycaemia, myocardial infarction, stroke, end-stage renal disease, blindness and amputation were included at a discount rate of 3%. The incidence rates of these complications were derived from the established UKPDS equations. The adoption rates were assumed and projected from the 2013 utilisation volume data of BIAsp and BHI by public providers. Sensitivity analyses were conducted.
Results
The adoption rates of BIAsp were assumed to increase from 1.8% in 2013 to 4.5% or 6.9% in 2018 for base case and upside scenario, respectively. Compared to the base case, upside scenario of wider BIAsp adoption was associated with an increased insulin cost up to RM 8.2M which was offset by avoided complication costs resulting in an overall net budget saving of approximately RM 5.5M over 5 years, primarily driven by estimated reduction in major hypoglycaemia events for patients treated with BIAsp.
Conclusions
The higher and wider adoption of BIAsp would likely be associated with cost savings in Malaysia from the MOH perspective attributed to its superiority in H1Ac reduction and lower major hypoglycemia risk in comparison to BHI. More cost saving would be concluded if productivity loss is included from a societal perspective.
A rapid and cost effective method in purifying small RNA

Citartan M, Tan SC, Tang TH

World J Microbiol Biotechnol, 2012 Jan;28(1):105-11.
PMID: 22806785 DOI: 10.1007/s11274-011-0797-0

Purification of RNA fragments from a complex mixture is a very common technique, and requires consideration of the time, cost, purity and yield of the purified RNA fragments. This study describes the fastest method of purifying small RNA with the lowest cost possible, without compromizing the yield and purity. The technique describes the purification of small RNA from polyacrylamide gel, resulting in a good yield of small RNA with minimum experimental steps in avoiding degradation of the RNA, obviating the use of ethidium bromide and phenol-chloroform extraction, as well as siliconized glass wools to remove the polyacrylamide gel particles. The purified small RNA is suitable for a wide variety of applications such as ligation, end labelling with radio isotope, RT-PCR (Reverse Transcriptase-PCR), Northern blotting, experimental RNomics study and also Systematic Evolution of Ligands by Exponential Enrichment (SELEX).
Fulltext Immunogenic recombinant Burkholderia pseudomallei MprA serine protease elicits protective immunity in mice

Chin CY, Tan SC, Nathan S

Front Cell Infect Microbiol, 2012;2:85.
PMID: 22919676 DOI: 10.3389/fcimb.2012.00085

Burkholderia pseudomallei is resistant to a diverse group of antimicrobials including third generation cephalosporins whilst quinolones and aminoglycosides have no reliable effect. As therapeutic options are limited, development of more effective forms of immunotherapy is vital to avoid a fatal outcome. In an earlier study, we reported on the B. pseudomallei serine MprA protease, which is relatively stable over a wide pH and temperature range and digests physiological proteins. The present study was carried out to evaluate the immunogenicity and protective efficacy of the MprA as a potential vaccine candidate. In BALB/c mice immunized with recombinant MprA protease (smBpF4), a significantly high IgG titer was detectable. Isotyping studies revealed that the smBpF4-specific antibodies produced were predominantly IgG(1), proposing that immunization with smBpF4 triggered a Th2 immune response. Mice were immunized with smBpF4 and subsequently challenged with B. pseudomallei via the intraperitoneal route. Whilst control mice succumbed to the infection by day 9, smBpF4-immunized mice were protected against the lethal challenge and survived beyond 25 days post-infection. In conclusion, MprA is immunogenic in melioidosis patients whilst also eliciting a strong immune response upon bacterial challenge in mice and presents itself as a potential vaccine candidate for the treatment of melioidosis.
Rotavirus electropherotypes from the Kuala Lumpur Hospital: a re-examination after an interval of seven years

Yap KL, Lim YH, Tan SC

Malays J Pathol, 1998 Jun;20(1):25-30.
PMID: 10879260

The objective of this study was to ascertain the extent changes have occurred in the epidemiology of human rotavirus electropherotypes from the same location 7 to 8 years after an earlier study. Genomic RNA profiles of rotaviruses from diarrhoeic children admitted to the Kuala Lumpur Hospital from April to December 1996 were determined by polyacrylamide gel electrophoresis and silver staining. A total of 179 group A rotaviruses were detected from 870 children: 175 with legible staining of all RNA segments were classified into 14 distinct electropherotypes (10 and 4 with long and short migration patterns respectively). In addition, the results revealed: high predominance of long pattern electropherotypes (94% of the total electropherotypes); most long electropherotypes with RNA profiles which all 11 RNAs migrated separately (8 of 10 electropherotypes); all short electropherotypes had segments 2 and 3 that co-migrated; presence of a very numerically dominant electropherotype (75% of all electropherotypes); frequent co-circulation of the dominant electropherotype-present throughout the study period--with other electropherotypes present for limited periods; sequential temporal appearances by similar electropherotypes. These observations were similar to that of an earlier study conducted in 1988/89. Nevertheless, the dominant electropherotype in the present study was different and not among the electropherotypes detected in the earlier study.
Selective extraction of salbutamol from human plasma with the use of phenylboronic acid

Koh YM, Saleh MI, Tan SC

J Chromatogr A, 2003 Feb 14;987(1-2):257-67.
PMID: 12613820

An investigation was conducted on the usage of a single-step extraction procedure involving the retention of a phenylboronate-salbutamol complex on an end-capped C18 solid-phase sorbent to determine the level of salbutamol in human plasma samples. Propranolol, a beta-blocker, was chosen as the internal standard for this assay. In this solid-phase clean-up method, 50 mM sodium carbonate buffer, pH 9.60, was used for conditioning the column as well as washing the endogenous interference. Under the optimal conditions, the recovery of salbutamol from spiked plasma samples was found to be high and reproducible with mean recoveries (n = 3) of more than 90% after elution by using 50% 1 M trifluoroacetic acid in methanol. This sample clean-up step was effectively analyzed under reversed-phase high-performance liquid chromatography with fluorimetric detection. The method was successfully applied to the routine measurement of salbutamol in human plasma from the bioequivalence study on the different administration route of salbutamol. Quantification of salbutamol was convincingly reported with the correlation of coefficient of 0.9980 for the concentration range from 0 to 1000 ng ml(-1). An adequate precision was achieved with both between- and within-day precisions of less than 10% (n = 6) for 100 and 1000 ng ml(-1) and less than 15% (n = 6) for 10 ng ml(-1).
Fulltext Predictive factors in the evolution of neural deficit in tuberculosis of the spine

Tan SC, Harwant S, Selvakumar K, Kareem BA

Med J Malaysia, 2001 Jun;56 Suppl C:46-51.
PMID: 11814249 MyJurnal

This study was conducted to determine the factors involved in predicting the onset of paraplegia in tuberculosis of the spine. A cross-sectional, case control review of 85 cases of spinal tuberculosis was conducted at the National Tuberculosis Centre in Kuala Lumpur. Sixty-nine of these cases were normal neurologically, whilst 16 cases experienced neural deficit. The data was analysed using backward logistic regression and Fishers exact probability test. The factors studied included symptoms and signs of spinal tuberculosis, common investigations for tuberculosis, and physical factors of the disease. Only the erythrocyte sedimentation rate (ESR) showed a significant difference between the neural deficit and neurologically normal groups. This suggests that the ESR may be a factor in predicting evolution of paraplegia in spinal tuberculosis. In addition, it was noted that a low proportion of patients had positive sputum smear results and bacterial culture growth for mycobacterium tuberculosis suggesting these tests are of limited value for tuberculosis of the spine.
Fulltext Osteomyelitis: An Uncommon Complication of BCG Vaccination

Pancharatnam D, Yong SM, Tan SC

Malays Orthop J, 2021 Mar;15(1):144-145.
PMID: 33880166 DOI: 10.5704/MOJ.2103.026
Fulltext Biomaterial application strategies to enhance stem cell-based therapy for ischemic stroke

Mohd Satar A, Othman FA, Tan SC

World J Stem Cells, 2022 Dec 26;14(12):851-867.
PMID: 36619694 DOI: 10.4252/wjsc.v14.i12.851

BACKGROUND: Ischemic stroke is a condition in which an occluded blood vessel interrupts blood flow to the brain and causes irreversible neuronal cell death. Transplantation of regenerative stem cells has been proposed as a novel therapy to restore damaged neural circuitry after ischemic stroke attack. However, limitations such as low cell survival rates after transplantation remain significant challenges to stem cell-based therapy for ischemic stroke in the clinical setting. In order to enhance the therapeutic efficacy of transplanted stem cells, several biomaterials have been developed to provide a supportable cellular microenvironment or functional modification on the stem cells to optimize their reparative roles in injured tissues or organs.
AIM: To discuss state-of-the-art functional biomaterials that could enhance the therapeutic potential of stem cell-based treatment for ischemic stroke and provide detailed insights into the mechanisms underlying these biomaterial approaches.
METHODS: The PubMed, Science Direct and Scopus literature databases were searched using the keywords of "biomaterial" and "ischemic stroke". All topically-relevant articles were then screened to identify those with focused relevance to in vivo, in vitro and clinical studies related to "stem cells" OR "progenitor cells" OR "undifferentiated cells" published in English during the years of 2011 to 2022. The systematic search was conducted up to September 30, 2022.
RESULTS: A total of 19 articles matched all the inclusion criteria. The data contained within this collection of papers comprehensively represented 19 types of biomaterials applied on seven different types of stem/progenitor cells, namely mesenchymal stem cells, neural stem cells, induced pluripotent stem cells, neural progenitor cells, endothelial progenitor cells, neuroepithelial progenitor cells, and neuroblasts. The potential major benefits gained from the application of biomaterials in stem cell-based therapy were noted as induction of structural and functional modifications, increased stem cell retention rate in the hostile ischemic microenvironment, and promoting the secretion of important cytokines for reparative mechanisms.
CONCLUSION: Biomaterials have a relatively high potential for enhancing stem cell therapy. Nonetheless, there is a scarcity of evidence from human clinical studies for the efficacy of this bioengineered cell therapy, highlighting that it is still too early to draw a definitive conclusion on efficacy and safety for patient usage. Future in-depth clinical investigations are necessary to realize translation of this therapy into a more conscientious and judicious evidence-based therapy for clinical application.
Fulltext Selection of best reference genes for qRT-PCR analysis of human neural stem cells preconditioned with hypoxia or baicalein-enriched fraction extracted from Oroxylum indicum medicinal plant

Kang IN, Lee CY, Tan SC

Heliyon, 2019 Jul;5(7):e02156.
PMID: 31388587 DOI: 10.1016/j.heliyon.2019.e02156

Whilst the potential of neural stem cell (NSC)-based treatment is recognized worldwide and seems to offer a promising therapeutic option for stroke treatments, there is currently no full understanding regarding the effects of hypoxic and baicalein-enriched fraction (BEF) preconditioning approaches on the therapeutic potential of these cells for stroke. The potential of preconditioned NSC can be determined based on the expression of several key neuroprotective genes using qRT-PCR technique. However, prior to that, it is imperative and extremely important to carefully select reference gene(s) for accurate qRT-PCR data normalization to avoid error in data interpretation. This study aimed to evaluate the stability of ten candidate reference genes via comprehensive analysis using three algorithms software: geNorm, NormFinder and BestKeeper. Our results revealed that HPRT1 and RPL13A were the most reliable reference genes for BEF-preconditioned NSCs, but ironically, HPRT1 was ranked as the least stable reference gene for hypoxic-preconditioned NSCs. On the other hand, RPLP1 and RPL13A were selected as the most stably expressed pair of reference genes for hypoxic-preconditioned NSCs. In conclusion, this study has pointed out the importance of identifying valid reference genes and has presented the first significant validation on best reference genes recommended for qRT-PCR study involves NSC preconditioned with hypoxia or with BEF extracted from Oroxylum indicum medicinal plant.
On the critical importance of meticulous data extraction for meta-analysis of genetic association study

Low TY, Chin KY, Tan SC

Arch Physiol Biochem, 2023 Dec;129(4):1007-1008.
PMID: 33689514 DOI: 10.1080/13813455.2021.1890132
Development of a simultaneous liquid-liquid extraction and chiral derivatization method for stereospecific GC-MS analysis of amphetamine-type stimulants in human urine using fractional factorial design

Aasim WR, Gan SH, Tan SC

Biomed Chromatogr, 2008 Sep;22(9):1035-42.
PMID: 18655218 DOI: 10.1002/bmc.1073

A stereospecific gas chromatography-mass spectrometry analysis method for amphetamine-type stimulants in human urine was recently developed. For maximum efficiency, liquid-liquid extraction and chiral derivatization of the analytes using (R)-(-)-alpha-methoxy-alpha-(trifluoromethyl)phenylacetyl chloride were performed simultaneously. The effects of (1) use of saturated sodium chloride in 2.0 M sodium hydroxide, (2) extraction solvent volume, (3) percentage of triethylamine, (4) derivatization reagent volume, (5) sample mixing time, (6) incubation temperature and (7) incubation time on method sensitivity and variability were assessed using a two-level, eight-run Plackett-Burman design followed by a fold-over design. The use of saturated sodium chloride solution and the derivatization reagent volume were significant factors (ANOVA, p<0.01). The saturated sodium chloride solution decreased sensitivity whereas an increased volume of derivatization reagent increased sensitivity. Calibration curves for all analytes were linear between 5 and 500 microg/L, with correlation coefficients of >0.99. Detection limits were
Detection of false positives by incorporation of a confirmatory blocking test into a commercial enzyme-linked immunosorbent assay specific for adenovirus antigen

Kirnpal-Kaur BS, Yap KL, Tan SC

Malays J Pathol, 1997 Dec;19(2):133-6.
PMID: 10879254

A blocking test was incorporated into the commercial IDEIA Adenovirus test (DAKO Diagnostics Ltd., Cambridgeshire, UK) to detect false positive results when faecal specimens were tested for adenovirus antigen. Immune rabbit serum raised against pooled adenovirus particles from human faecal specimens, together with the pre-immune serum, was used. Assessment of positive showed that false positives were produced under two different conditions: when results were based on visual determination instead of a cut-off value determined from photometric reading, and when absorbance values were not immediately read at the end of the test. Under the optimum condition for reading and assessment of test results (immediate reading and photometric determination), 11% of 65 adenovirus-positive samples were checked by the blocking ELISA as false positives. The rest of the specimens showed blocking of positive absorbance values by 70 to 98%. ELISA was found to be more sensitive than immune electron microscopy on samples with lower antigen concentration.
Clean-up, detection and determination of salbutamol in human urine and serum

Saleh MI, Koh YM, Tan SC, Aishah AL

Analyst, 2000 Sep;125(9):1569-72.
PMID: 11064937

Salbutamol ¿2-(tert-butylamino)-1-[4-hydroxy-3- (hydroxymethyl)phenyl]ethanol¿, also known as albuterol, is clinically the most widely used beta 2-adrenoceptor agonist in the treatment of bronchial asthma. During this study, we evaluated liquid-liquid extraction (LLE) and solid-phase extraction (SPE) in order to develop a reliable extraction method followed by analysis using liquid chromatography and gas chromatography. An assay is described which involves SPE as the clean-up method followed by gas chromatography-mass spectrometry to determine salbutamol levels in human serum after oral administration. The SPE method requires the use of a hyper-cross-linked styrene-divinylbenzene bonded phase (ENV+) without involving any sample pre-treatment to obtain 60-65% recoveries for salbutamol and terbutaline as the internal standard. Distilled water and 1% trifluoroacetic acid in methanol were found to be the most suitable washing solvent and eluting solvent, respectively. A detection limit of 2 ng mL-1 was achieved by derivatization with N-methyl-N-trimethylsilyltrifluoroacetamide to form trimethylsilyl (TMS)-salbutamol (m/z 369) and TMS-terbutaline (m/z 356). The relationship between the ratio of the peak area of salbutamol to that of the internal standard and concentration was linear for the range tested (2-200 ng mL-1) and the correlation of coefficient was 0.9999 with a y-intercept not significantly different from zero. The inter-day relative standard deviation (RSD) was < 10% for all three concentrations. The intra-day RSD was 14% for 2 ng mL-1. This assay was then successfully applied to human serum samples obtained from clinical trials after oral administration of salbutamol.

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