Enzymatic activity of prostate-specific antigen (PSA) in prostate cancer and human bone-metastasizing prostate cancer LNCaP cells
Notice bibliographique
Résumé
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.)
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 0,001 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».