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Effect of fibroblast growth factor saporin mitotoxins on human bladder cell lines
T A Tetzke1, M C Caton, P A Maher
1Prizm Pharmaceuticals Inc., San Diego, California, USA.
Abstract:
Mitotoxins targeted via high-affinity growth factor receptors on the cell surface are a potential means of anticancer therapy. We have evaluated the effect of a chemically conjugated (FGF2-SAP) and a fusion protein (rFGF2-SAP) mitotoxin containing FGF-2 and saporin on normal (FHs 738B1) and malignant bladder cell lines (HT1197, TCCSUP, EJ-6, and RT4). The FGF-saporins demonstrated potent cytotoxicity in malignant bladder cell lines with an ID50 range of 0.13-13.6 nM, whereas cells derived from normal fetal bladder (FHs 738B1) were less sensitive to FGF2-saporins (ID50 > 100 nM). Greater than a 100-fold difference in cytotoxicity between FGF-saporins and unconjugated saporin was observed. Assessment of cellular FGF-2 content and secretion showed that FHs 738B1 and TCCSUP contained and secreted significantly more FGF-2 compared to other cell lines tested. (125)I-FGF-2 receptor binding studies showed the presence of high-affinity (pM) FGF receptors on all bladder cell lines. Cross-linking studies revealed the presence of a major receptor-ligand complex of 90 kDa on FHs 738B1 and 160-170 kDa on the other bladder cell lines. All cell lines studied, except RT4, expressed solely FGFR-1. These studies demonstrate that FGF2-saporins have antiproliferative activity on human bladder cancer cell lines. However, the number of high-affinity FGF receptors, and FGF-2 cellular content and secretion are not absolute determinants of cellular sensitivity to FGF2-saporins.
Insights
FGF2-saporin mitotoxins show potent anticancer activity against bladder cancer cell lines, offering a targeted therapy approach. Sensitivity varies, indicating complex interactions beyond receptor levels.
Area of Science:
- Oncology
- Molecular Biology
- Biochemistry
Background:
- Targeted cancer therapies utilize mitotoxins linked to growth factors for selective cell killing.
- Fibroblast Growth Factor 2 (FGF-2) and saporin are components of novel mitotoxin conjugates.
Purpose of the Study:
- To evaluate the efficacy of FGF2-saporin mitotoxins against normal and malignant human bladder cell lines.
- To investigate the relationship between FGF receptor expression, FGF-2 levels, and cellular sensitivity to these mitotoxins.
Main Methods:
- Chemically conjugated (FGF2-SAP) and fusion protein (rFGF2-SAP) mitotoxins were tested on bladder cell lines.
- Cytotoxicity was assessed via ID50 values.
- FGF-2 content, secretion, and FGF receptor binding were analyzed.
Main Results:
- FGF2-saporins exhibited significant cytotoxicity against malignant bladder cell lines (ID50: 0.13-13.6 nM) compared to normal cells (ID50 > 100 nM).
- A >100-fold difference in potency was observed between FGF-saporins and unconjugated saporin.
- While high-affinity FGF receptors were present on all cell lines, FGF-2 cellular content and receptor levels did not solely determine sensitivity.
Conclusions:
- FGF2-saporins demonstrate antiproliferative activity against human bladder cancer cells.
- Cellular sensitivity to FGF2-saporins is influenced by factors beyond FGF receptor number and FGF-2 levels.