Biomedical subjects
Albert Chang
Publications and source records attributed to Albert Chang.
Human kallikrein 13: production and purification of recombinant protein and monoclonal and polyclonal antibodies, and development of a sensitive and specific immunofluorometric assay.
BACKGROUND: The aims of this study were to develop immunologic reagents and a sensitive and specific immunoassay for human kallikrein 13 (hK13) and to examine the presence of hK13 in human tissues and biological fluids. METHODS: Recombinant hK13 protein was produced and purified with use of a Pichia pastoris yeast expression system. The protein was used as an immunogen to generate mouse monoclonal and rabbit polyclonal anti-hK13 antibodies. A sandwich-type immunoassay was developed with these antibodies. The assay was used to measure hK13 in various biological fluids and tissue extracts. Immunohistochemical analysis was also performed on nondiseased and cancerous prostatic sections. RESULTS: The hK13 immunoassay had a detection limit of 0.05 micro g/L and showed no cross-reactivity with homologous kallikreins. The assay was linear at 0-20 micro g/L, and within-and between-run CVs were <10% (n = 12). hK13 was detected in tissues, including esophagus, tonsil, trachea, lung, cervix, and prostate. hK13 was also found in seminal plasma, amniotic fluid, follicular fluid, ascites of ovarian cancer patients, breast milk, and cytosolic extracts of ovarian cancer tissues. hK13 was immunohistochemically localized in epithelial cells of both nondiseased and cancerous prostate. hK13 appears to be overexpressed in 50% of ovarian cancer tissues compared with healthy ovarian tissues. Recovery of active enzyme added to milk or amniotic fluid was 70-98%, but was <20% when added to serum, suggesting rapid sequestration by protease inhibitors. In fluids and tissue extracts, hK13 was found in its free (approximately 30 kDa) form. CONCLUSIONS: This immunofluorometric assay for hK13 may be used to examine the value of hK13 as a disease biomarker and to further explore the physiologic and pathobiologic role of this enzyme in human disease.
Down-regulation of the human kallikrein gene 5 (KLK5) in prostate cancer tissues.
BACKGROUND: Kallikreins are a subgroup of serine proteases with diverse physiological functions. Many kallikrein genes are differentially expressed in various malignancies and prostate specific antigen (PSA; encoded by the KLK3 gene) is the best tumor marker for prostate cancer. Human glandular kallikrein (hK2; encoded by the KLK2 gene) is an emerging tumor marker for prostate cancer. KLK5 is a newly discovered human kallikrein gene which shares a high degree of homology and is located adjacent to KLK2 and KLK3 genes on chromosome 19q13.4. Like KLK2 and KLK3, the KLK5 gene is regulated by steroid hormones in the BT-474 breast cancer cell line. We have previously shown that KLK5 is differentially expressed in ovarian and breast cancer. METHODS: We compared the expression of KLK5 in 29 pairs of histologically confirmed normal and prostate cancer tissues by quantitative RT-PCR using the LightCycler technology. RESULTS: KLK5 expression was significantly lower in cancer tissues compared to their normal counterparts. Lowest levels of expression were found in T3 stage tumors compared with T1 and T2. Also, a significant negative correlation was found between Gleason score and KLK5 expression. CONCLUSIONS: KLK5 should be further studied as a potential new prognostic marker in prostate cancer, whose expression is negatively correlated with cancer aggressiveness.
Line sepsis in home parenteral nutrition patients: are there socioeconomic risk factors? A Canadian study.
BACKGROUND: Line sepsis complicates home parenteral nutrition (HPN). This study examined nonmedical risk factors that may contribute to line sepsis and compared 2 HPN programs with different administrative structures (Ontario and British Columbia [BC]) in terms of line sepsis and patient satisfaction. METHODS: A survey was developed to evaluate possible correlation between line sepsis and (1) patients' perceptions of HPN care, (2) family support, (3) community support, and (4) socioeconomic status. Data were analyzed by categorizing into high- and low-risk groups using a cutoff point. A second method analyzed the incidences of line sepsis as a continuous variable. RESULTS: Sixty-eight patients responded to the survey: 33 from Ontario (62%), 35 from BC (44%). Community agency, socioeconomic and educational status were not significant in determining line sepsis. Patients who had (1) medication or blood work done through the catheter, (2) a higher number of dependents, or (3) had a trained family member involved in HPN were in the high-risk category for line sepsis, in addition to patients who were part-time students or receiving social assistance. When comparing the provinces, there was no difference in line sepsis. However, significant differences between the provinces include (1) BC patients rate their level of care lower; (2) Ontario patients rely more on family members for HPN; and (3) Ontario patients have more community support. CONCLUSIONS: Line sepsis may be increased by some nonmedical risk factors. However, when comparing the 2 programs, rates of line sepsis were not influenced by different administrative structures.