Biomedical subjects

J F Santibañez

Publications and source records attributed to J F Santibañez.

5 recordsLinked to original sources

PubMed1998

Soluble factors secreted by PC-3 cells induce structural changes in proteoglycans produced by fetal rat osteoblasts.

Metastatic prostate cancer is unique in its ability to induce an osteoblastic reaction in the skeleton, a phenomenon which is followed by impairment of the mineralization process. We have proposed previously that soluble factors present in a medium conditioned by prostatic PC-3 cells (PC-3 CM) induce a rearrangement of bone extracellular matrix (ECM) which precedes the inhibition of mineralization. Interstitial collagen is the ECM component which is most affected by these prostatic factors. In this study, we evaluated the synthesis and molecular characteristics of proteoglycans (PG) derived from fetal rat osteoblasts cultured in the presence of PC-3 CM. These soluble factors induce a decrease (15-20%) in the production of PG. The in vitro produced PG display a decreased mean charge density and an increase in the hydrodynamic size of glycosaminoglycan (GAG) chains. No changes were observed in the size of the core protein or in the type of GAG chains of chondroitin sulfate. From these results, we suggest that fetal rat osteoblasts cultured in the presence of PC-3 CM synthesize PG which generate an ECM unable to support proper mineralization. We speculate that the modification of the ECM offers an advantage for tumor expansion.

Animals↗

PubMed1995

The secretion of urokinase-like plasminogen activator is inhibited by microtubule-interacting drugs.

The secretion of proteinases into the extracellular matrix is one of the main features of tumour cells, as related to their invasive behaviour. Considering the role of the microtubule cytoskeleton, and particularly the action of microtubule-associated protein (MAPs) in mediating protein secretion, the effects of the anti-microtubule drugs estramustine and taxol, on the secretion of urokinase-type plasminogen activator (u-PA) and the 72 kDa gelatinase were investigated. Treatment of 5637 bladder carcinoma cells with estramustine and taxol inhibited u-PA secretion into the conditioned medium in a drug concentration-dependent fashion. This inhibition was confirmed by determinations of u-PA enzymatic activities and by measurements of the levels of immunoreactive activator. Studies using gelatin zymograms also showed an inhibition of another tumoural proteinase namely the 72 kDa gelatinase. Time-course uptake experiments showed that estramustine was incorporated into the cells, a process which depended on temperature. On the other hand, immunofluorescence studies indicated that the microtubule network was affected by taxol with the formation of bundles of microtubules at different cell domains. Minor effects were visualized after treatment of the cells with estramustine-phosphate, a drug that blocks primarily the action of microtubule-associated proteins. The studies provide a way to analyse the relationships between u-PA secretion and the integrity of the cytoskeletal network.

Estramustine↗

PubMed1994

Surface-associated plasminogen activation in leukemic cells: interaction with extracellular matrix.

In WEHI-3B murine leukemic cells, plasminogen activator and plasminogen binding sites are associated with the cell membrane. The putative receptor for the zymogen exhibits low affinity for the ligand (dissociation constant of 0.38 microM and a high binding capacity (40,000 sites per cell). Plasminogen also binds in a cooperative fashion to type I collagen with an affinity which is higher than that displayed by cells. Collagen-bound plasminogen can be activated by cells preincubated with plasminogen in a manner that cells develop the capacity to adhere to type I collagen. The activation of collagen-bound plasminogen by cellular urokinase-like plasminogen activator (u-PA) was 60% more efficient than the activation of the soluble (not bound) form of plasminogen. These results suggest that in the invasive phenomena, WEHI cells operate as carriers of plasminogen from plasma to tissue. In addition, collagen can serve as a reservoir of zymogen in the extracellular matrix milieu through direct binding to plasminogen and at the same time allow more efficient plasminogen activation.

Animals↗

PubMed1993

Extracellular calcium modulates proliferation of factor dependent hemopoietic cells.

Blockade of the calcium channel inhibited, in a dose-dependent manner, the proliferation of the IL-3 dependent FDCP-1 cell line and normal murine bone marrow cells. Similar results were obtained by lowering the amount of extracellular calcium using specific chelators or a calcium-free medium. These results suggest that factor-dependent cell proliferation is highly sensitive to fluctuations in the concentration of extracellular calcium.

Animals↗

PubMed1993

Membrane-associated procollagenase of leukemic cells is activated by urokinase-type plasminogen activator.

Murine leukemic cells from the WEHI-3B line, present in the cell surface a latent collagenase activity which is activated proteolytically. In this paper we show that this enzyme is activated by plasmin generated by the activity of a urokinase-like plasminogen activator (u-PA) also present in the surface of these cells. Using a reverse fibrin autography method we found that u-PA is the major proteolytic activity present in the cell membranes. This fact suggests that u-PA could represent a normal activating system for this collagenase.

Animals↗