Displaying publications 1 - 20 of 46 in total

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  1. Hoe SL, Sam CK
    Malays J Pathol, 2006 Jun;28(1):35-9.
    PMID: 17694957 MyJurnal
    This study reports the results of mutation detection of tumour suppressor genes, p53 and RB2/p130 genes in Malaysian nasopharyngeal carcinoma (NPC) studied by PCR-CSGE analysis and direct DNA sequencing method. Frequent sites of mutation in both genes (exons 5-8 of p53 and exons 19-21 of RB2/p130) were examined. Thirty-six NPC blood samples and three NPC cell lines were investigated for the presence of mutations. No mutation of p53 and RB2/p130 genes was identified in any of the blood samples. Nonetheless, there was an identical G-->4 C nucleotide change at codon 280 of p53 gene in all the cell lines. A larger study that includes biopsy tissues should be carried out to provide a more in-depth look into the pathogenesis of NPC in Malaysia.
  2. Tan EL, Sam CK
    Exp. Oncol., 2007 Sep;29(3):166-74.
    PMID: 18004239
    Epstein-Barr virus (EBV), a human gammaherpesvirus is intimately associated with nasopharyngeal carcinoma (NPC), with the incidence of the virus detected in malignant tissues being close to 100% in NPC endemic areas. The viral latent gene, latent membrane protein 1 (LMP1), has all the typical characteristics of an oncogene and extensive studies have shown beyond doubt its abilities in cellular transformation giving rise to malignant phenotypes. The present study compares the gene sequence and biological properties of LMP1 gene derived from two patients with different stages of NPC--one presented with dysplastic, pre-malignant lesion and the other with malignant lesion.
  3. Yeoh SM, Sam CK
    Asian Pac J Allergy Immunol, 2001 Mar;19(1):7-10.
    PMID: 11495303
    The significance of food specific serum IgG4 antibody in food allergy is unclear and this led us to investigate the relevance of specific IgG4, along with IgG and IgE antibodies to two common food allergens in Malaysia. Enzyme-linked immunosorbent assay (ELISA) was used to measure the serum antibodies in 143 allergic rhinitis patients' sera, of which 47 were from patients with clinical indication of shrimp allergy, 46 with clinical indication of crab allergy and 50 without indication to either allergy. Clinical indication of allergy was based on answers to a questionnaire or results of the skin prick test. We found that the elevation of specific IgE or IgG4 is associated with shrimp and crab allergies but elevation of specific IgG is not associated with either allergy. However, the clinical utility of elevated specific IgG and IgG4 levels is pending further investigation.
    Study site: Allergic rhinitis clinic, University Malaya Medical Centre (UMMC), Kuala Lumpur, Malaysia
  4. Sam CK, Prasad U, Pathmanathan R
    Eur J Surg Oncol, 1989 Aug;15(4):357-60.
    PMID: 2547665
    The titres of IgA against Epstein-Barr virus, viral capsid antigens and the titres of IgG against early antigen were found to be useful markers for the diagnosis of different histopathological types of nasopharyngeal carcinoma.
  5. Cheng HM, Sam CK
    Immunol. Lett., 1990 Oct;26(1):7-10.
    PMID: 2276764
    The anti-phospholipid antibody (aPL) in 26 heat-inactivated normal human sera (NHS) was tested for IgG subclass in ELISA. The specific antibody in NHS included all four IgG antibody subclasses, as well as IgA. The incidence of IgG subclasses ranged from 50% (13/26) for IgG1 to 92% (24/26) for IgG2. Specific IgA anti-phospholipid antibody (aPL) was detected by ELISA in 38% (28/73) of normal human saliva. The salivary IgA aPL bound preferentially to anionic phospholipids including cardiolipin, phosphatidylserine and phosphatidic acid but not to phosphatidylcholine or sphingomyelin. Unlike aPL in normal human sera, aPL in saliva was predominantly not associated with the previously described heat-labile inhibitor of aPL. This may indicate a role of salivary IgA aPL in local immunity by binding to cross-reactive bacterial cell surface components including phospholipids.
  6. Tan EL, Selvaratnam G, Kananathan R, Sam CK
    BMC Cancer, 2006;6:227.
    PMID: 16995954
    Nasopharyngeal carcinoma (NPC) is a common epithelial neoplasm among the Chinese populations in Southern China and South East Asia. Epstein-Barr virus (EBV) is known to be an important etiologic agent of NPC and the viral gene products are frequently detected in NPC tissues along with elevated antibody titres to the viral proteins (VCA and EA) in a majority of patients. Elevated plasma EBV DNA load is regarded as an important marker for the presence of the disease and for the monitoring of disease progression. However, other serum/plasma parameters such as the levels of certain interleukins and growth factors have also been implicated in NPC. The objectives of the present study are, 1) to investigate the correlations between plasma EBV DNA load and the levels of interleukin (IL)-6, IL-10, TGF-beta1 and SCF (steel factor) and 2) to relate these parameters to the stages of NPC and the effect of treatment.
  7. Tan EL, Looi LM, Sam CK
    Singapore Med J, 2006 Sep;47(9):803-7.
    PMID: 16924363
    Nasopharyngeal carcinoma (NPC) is an important cancer in Malaysia and is one of the major causes of cancer mortality in this country. This study evaluates the diagnostic and prognostic values in the quantitative relationship between the cell-free Epstein-Barr virus (EBV) deoxyribonucleic acid (DNA) load and the tumour burden.
  8. Tan EL, Peh SC, Sam CK
    J Med Virol, 2003 Feb;69(2):251-7.
    PMID: 12683415
    Nasopharyngeal carcinoma, a malignancy associated closely with Epstein-Barr virus (EBV), is prevalent among Chinese of Southern China origin. Epidemiological studies indicate a high prevalence of EBV in Asia with viral isolates having typical characteristics of the putative viral oncogene, latent membrane protein 1 (LMP-1), such as the loss of the Xho1 restriction site in Exon 1 and the 30-bp deletion in Exon 3. The EBV LMP-1 gene from throat washings of 120 nasopharyngeal carcinoma patients and 14 healthy individuals were analyzed. Similar analyses were also carried out on 30 and 12 postnasal space biopsies from nasopharyngeal carcinoma patients and healthy individuals, respectively. The 30-bp deletion was detected in 20% of nasopharyngeal carcinoma throat washes and in 100% of nasopharyngeal carcinoma postnasal space biopsies. Interestingly, 16% of the nasopharyngeal carcinoma biopsies possessed both the deleted and the undeleted variants, suggestive of dual infections. The notion of dual infections in nasopharyngeal carcinoma was further supported by the coexistence of both "F" and "f" (BamH1F region) EBV variants in 11% of the nasopharyngeal carcinoma biopsies. All of the throat washes and biopsies from the healthy controls showed the undeleted variant. The loss of the Xho1 restriction site was found with higher frequency both in throat washes and biopsies from patients with nasopharyngeal carcinoma. The discrepancy in the frequency of the 30-bp deletion between throat washes (20%) and postnasal space biopsies (100%) was an indication that this deletion is specific for viral isolates from primary tumour sites.
  9. Sam CK, Abu-Samah AJ, Prasad U
    Eur J Surg Oncol, 1994 Oct;20(5):561-4.
    PMID: 7926060
    Titers of IgA/VCA from 92 nasopharyngeal carcinoma (NPC) patients were monitored for 3 to 11 years from the time of diagnosis. The fluctuations in the IgA/VCA titers during follow-up did not correlate with the clinical status of the patients, suggesting that IgA/VCA is of marginal significance in the monitoring of NPC patients during follow-up. In addition, the frequency of recurrence of NPC was independent of presence or absence of elevated IgA/VCA at diagnosis.
  10. Mathew A, Cheng HM, Sam CK, Prasad U
    Clin. Immunol. Immunopathol., 1994 May;71(2):164-8.
    PMID: 7514112
    Inhibition studies were carried out to study possible cross-reactivity between a peptide fragment of the Epstein-Barr virus nuclear antigen, EBNA-1, and keratin/collagen. The 20-amino acid peptide (pAG), derived from a glycine-alanine repeat region of EBNA-1, uniquely makes up about one-third of the viral protein and is a dominant IgA antigenic epitope in patients with nasopharyngeal carcinoma (NPC). A small percentage of normal human sera (NHS) also binds pAG and this reactivity is examined in this study. Ten percent (2/20) and 13.4% (2/15) of IgA-pAG-positive NPC sera and NHS, respectively, were significantly inhibited by keratin in a competitive ELISA system. Conversely, 31.6% (6/19) and 30.8% (4/13) of IgA-keratin-positive NPC sera and NHS, respectively, were significantly inhibited by pAG. This indicated minimum cross-reactivity between IgA serum antibodies to EBNA-1 and keratin. Using collagen as inhibitor, none of 18 and only 2/13 IgA-pAG-positive NPC sera and NHS, respectively, were inhibited. In the collagen ELISA system, only 2/19 (10.5%) and 4/25 (16%) of IgA-collagen-positive NPC sera and NHS, respectively, were inhibited with pAG. Therefore, cross-reactivity with collagen was also low. IgA-pAG-positive NHS may therefore not be a false positive phenomenon, but whether it may represent an early serological profile related to NPC carcinogenesis remains to be determined.
  11. Cheng HM, Ngeow YF, Sam CK
    J Immunol Methods, 1989 Nov 30;124(2):235-8.
    PMID: 2600427
    Heat treatment of sera at 56 degrees C for 30 min results in positive ELISA reactions for anti-cardiolipin antibody (aCL) in sera that had undetectable or low levels of aCL before heat inactivation. The positive, potentiated reactivity of the heated sera in the aCL ELISA could be inhibited with the cardiolipin antigen and was abolished by prior IgG depletion using staphylococcal protein A. The heat-potentiating effect of aCL binding in ELISA was evident in both normal human sera and clinical sera including sera from patients with systemic lupus erythematosus and syphilis.
  12. Lim CS, Krishnan G, Sam CK, Ng CC
    Clin. Chim. Acta, 2013 Jan 16;415:158-61.
    PMID: 23043757 DOI: 10.1016/j.cca.2012.08.031
    Because blocking agent occupies most binding surface of a solid phase, its ability to prevent nonspecific binding determines the signal-to-noise ratio (SNR) and reliability of an enzyme-linked immunosorbent assay (ELISA).
  13. Ho SL, Tan EL, Sam CK, Goh KL
    J Dig Dis, 2010 Apr;11(2):101-5.
    PMID: 20402836 DOI: 10.1111/j.1751-2980.2010.00423.x
    To determine the prevalence of primary clarithromycin resistance amongst Helicobacter pylori (H. pylori) strains in Malaysian patients with gastroduodenal diseases, by using restriction fragment length polymorphism (RFLP) in domain V of 23S rRNA.
  14. Chan KG, Yin WF, Sam CK, Koh CL
    J. Ind. Microbiol. Biotechnol., 2009 Feb;36(2):247-51.
    PMID: 18946694 DOI: 10.1007/s10295-008-0491-x
    A novel chemically defined medium, named KG medium, supplemented with N-3-oxo-hexanoylhomoserine lactone (3-oxo-C6-HSL), an acylhomoserine lactone (AHL) used as signalling molecules in Gram-negative bacterial cell-to-cell communication, as the sole source of carbon and nitrogen, was designed and successfully used for the enrichment and isolation of AHL-degrading bacteria. A 3-oxo-C6-HSL-degrading bacterium, 13sw7, was isolated from sewage after six enrichment transfers in the 3-oxo-C6-HSL-containing KG medium. On the basis of the almost complete 16S ribosomal DNA sequence, isolate 13sw7 was clustered with unculturable beta-proteobacteria. This study indicates that the AHL-containing KG medium is effective in isolating AHL-degrading bacteria, including those previously considered unculturable, from environmental sources. To the best of our knowledge, this is the first documentation of the isolation of an AHL-degrading proteobacterium from sewage.
  15. Lee LK, Tan EL, Gopala K, Sam CK
    Singapore Med J, 2007 Jul;48(7):632-4.
    PMID: 17609824
    Nasopharyngeal carcinoma (NPC) is the second most common cancer among Malaysian Chinese males. We determined the frequencies of 17 human leukocyte antigens (HLA), HLA-A and HLA-B, alleles in 88 Malaysian Chinese with NPC.
  16. Wong MM, Lye MS, Cheng HM, Sam CK
    Asian Pac J Allergy Immunol, 2005 Mar;23(1):65-7.
    PMID: 15997877
    The antibody levels to viral capsid antigen (VCA) and early antigen (EA) of Epstein-Barr virus (EBV) in 164 nasopharyngeal carcinoma (NPC) patients from Sarawak, East Malaysia were significantly higher than those in 147 sex, age and ethnically matched healthy controls. As diagnostic markers of NPC, IgG/VCA at reciprocal titers > or =160 was the most sensitive (89%, with 98% specificity), while IgA/EA at > or =5 was the most specific (100%) but the least sensitive (75%). The sensitivity and specificity of IgA/VCA at reciprocal titers > or =10 were 84% and 97%. IgA/VCA has an advantage over IgG/VCA despite the slightly lower sensitivity due to its consistently more distinct fluorescence reaction. The sensitivity and specificity can be marginally improved by a combination of two tests.
  17. Mathew A, Cheng HM, Sam CK, Joab I, Prasad U, Cochet C
    Cancer Immunol. Immunother., 1994 Jan;38(1):68-70.
    PMID: 8299121
    The BamHI Z EBV replication activator (ZEBRA) protein is involved in the switch from latency to productive cycle of Epstein-Barr virus. A recombinant ZEBRA protein was synthesized and assessed in enzyme-linked immunosorbent assay (ELISA) for serum IgG response in nasopharyngeal carcinoma (NPC) patients. In 100 NPC serum samples that were positive for IgA to the EBV viral capsid antigen (VCA), 75% had IgG anti-ZEBRA antibodies. In contrast, only 3/83 (3.6%) serum samples from healthy donors and 2/50 (4%) from other cancers were positive for IgG to ZEBRA. Interestingly, in a selected group of 100 NPC sera negative for IgA to VCA, 25% contained IgG anti-ZEBRA antibodies. This suggests that the ELISA for IgG anti-ZEBRA may also identify earlier cases of NPC not detected by the conventional immunofluorescence test for IgA to VCA.
  18. Sam CK, Soon SC, Liam CK, Padmaja K, Cheng HM
    Asian Pac J Allergy Immunol, 1998 Mar;16(1):17-20.
    PMID: 9681124
    We investigated the aeroallergens affecting 200 asthmatics from the University Hospital in Kuala Lumpur, Malaysia and found 164 (82%) patients with skin prick test (SPT) reactivity to one or more of a panel of 14 allergens, which included indoor and outdoor animal and plant aeroallergens. Reactivity was most frequent to the indoor airborne allergens, with 159 (79.5%) reacting to either or both house dust mite (Dermatophagoides) species and 87 (43.5%) to cockroach. The SPT reactivity to house dust mites corresponded with the finding that patients found house dust to be the main precipitant of asthmatic attacks.
  19. Cheng HM, Foong YT, Mathew A, Sam CK, Dillner J, Prasad U
    J. Virol. Methods, 1993 Apr;42(1):45-51.
    PMID: 7686558
    An ELISA using the Epstein-Barr virus nuclear antigen 1 (EBNA 1) was found to detect selectively specific IgA in sera from patients with nasopharyngeal carcinoma (NPC). The antigen, p107, was a 20-amino acid synthetic peptide, representing a major epitope of EBNA 1.267/294 (90.8%) of NPC patients had IgA antibodies to p107 but in normal individuals, only 41/577 (7.1%) had IgA/p107. In sera from patients with other cancers, 11/77 (14.3%) had IgA/p107 reactivity. 124 IgA/VCA positive and 86 IgA/VCA negative NPC sera were also tested for IgA/p107 binding in ELISA. The majority of IgA/VCA positive sera (117) also contained IgA/p107 antibodies. Of interest was the detection of 74/86 IgA/p107 reactive sera in the IgA/VCA negative group. The results suggest that the IgA/p107 ELISA could become a useful, complementary screening assay to the IgA/VCA immunofluorescence test for detection of NPC.
  20. Foong YT, Cheng HM, Sam CK, Dillner J, Hinderer W, Prasad U
    Int J Cancer, 1990 Jun 15;45(6):1061-4.
    PMID: 1693600
    The Epstein-Barr virus nuclear antigen I (EBNA I) is the only latent EBV antigen consistently expressed in malignant tissues of the nasopharynx. A 20-amino-acid synthetic peptide, p107 contains a major epitope of EBNA I. We tested sera from 210 patients with nasopharyngeal carcinoma (NPC) and from 128 normal individuals (NHS) for IgA antibodies to p107 using an enzyme-linked immunosorbent assay (ELISA). Whereas 191/210 (91%) of NPC patients had IgA antibodies to p107, only 17/128 (13.3%) of NHS had such antibodies and only 6/57 (10.5%) of sera from patients with malignancies other than NPC had IgA-p107 reactivity. Thirty-nine salivary samples from 46 NPC patients (84.8%) also contained IgA-p107 antibodies whereas only 3/42 (7.1%) of normal saliva samples were IgA-p107 positive. The results suggest that IgA antibodies to EBNA I may become a useful, easily measurable, marker for NPC.
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