Enzymatic activity of prostate-specific antigen (PSA) in prostate cancer and human bone-metastasizing prostate cancer LNCaP cells
Bibliographic record
Abstract
5617 Patients with prostate cancer frequently have a poor prognosis as a result of the spread of cancer to bone. The presence of tumour cells frequently stimulates osteoblastic activity resulting in increased bone mass in these patients. The serum PSA (prostate-specific antigen) test is widely used for the early diagnosis, staging and monitoring of prostate cancer. There is evidence suggesting that the serine protease activity of PSA could be involved in the osteoblastic activity observed in bone metastasis from prostate cancer. PSA is expressed as a prepro-protein. The predominant form of PSA in serum is PSA bound to α1-antichymotrypsin (ACT). Substrates of PSA include semenogelin, fibronectin, and laminin. On the other hand, in tumour tissue an inverse correlation between Gleason score and PSA staining intensity has been shown by immunohistochemistry. This discrepancy between serum and tissue PSA underlines the need for clarification of the biological role of PSA in prostate cancer, which is still unknown. The objectives of this study were to determine the prevalent form of PSA in human prostate adenocarcinoma samples and the enzymatic activity towards various substrates of PSA. Tumour samples were obtained from prostate cancer patients undergoing prostatectomy, snap-frozen in liquid nitrogen, and homogenized in 125 mM Tris, 10% SDS. Sera were obtained from prostate cancer patients with PSA values above 100 ng/ml. For comparison recombinant PSA and PSA found in the conditioned media (CM) of human prostate cancer LNCaP cells were used. Homogenates of tumour samples and sera were subjected to SDS-PAGE followed by Western blotting using antibodies against PSA and PSA bound to ACT. PSA activity was determined in tumour homogenates, serum, and LNCaP-CM using a synthetic substrate (S-2586). Samples (5 μg of tumour homogenate, 1 μl of serum, or 20 μl of CM) were incubated with 0.5 mM S-2586 and absorbance at 405 nm was measured spectrophotometrically. Degradation experiments were carried out by incubating samples in the presence of 2.5 μg human fibronectin or 5 μg laminin for 4 hrs at 37 °C, followed by separation by 5-20% SDS-PAGE and staining with Coomassie Blue. Our results show that in most tumour homogenates and in the LNCaP-conditioned media the majority of the PSA was present in the 31 kDa form (pro-PSA). In the sera the predominant form of PSA was PSA-ACT. All prostate cancer homogenates showed activity towards S-2586, however one sample (R256) demonstrated very high activity. Tumour sample R256 was also capable of degrading fibronectin and laminin, which was inhibitable by the addition of 200 μM Zn2+ but only in part by 100 μg/ml TPCK. Fibronectin enzymography showed proteolytic activity at 29 kDa further confirming the presence of active PSA. (This research is supported by the Canadian Institutes of Health Research and the Northern Cancer Research Foundation.)
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".