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Mitomycin C induces multidrug resistance in glaucoma surgery
Arno Hueber1, Johannes M Esser, Norbert Kociok
1Centre of Ophthalmology, University of Cologne, Cologne, Germany. arno.hueber@uni-koeln.de
Background:
Despite the adjuvant use of mitomycin C during trabeculectomy, failures still occur. We investigated whether cultured human Tenon fibroblasts exposed to low-dose mitomycin C developed a multidrug resistance phenotype in vitro, and whether mitomycin C treatment during previous filtration surgery induces P-glycoprotein expression in vivo.
Methods:
Cultured human Tenon fibroblasts treated with low-dose 0.01 nM mitomycin C for 2 weeks were subsequently treated with 0.1 to 100 microM mitomycin C in the absence or presence of 4 microM verapamil, and allowed to recover for 24 hours. Low-dose mitomycin C-treated fibroblasts were analysed for P-glycoprotein expression using flow cytometry, immunoblotting, and RT-PCR for mdr-1 mRNA. In addition, fibroblasts were treated with low dose 0.1 nM 5-fluorouracil for 2 weeks and analysed for P-glycoprotein expression using flow cytometry. Expression of P-glycoprotein was analysed in surgically removed Tenon tissue (n = 30) using immunohistochemistry. Of the 30 patients, 20 had a previous trabeculectomy, of which nine had previous adjuvant therapy with mitomycin C during trabeculectomy.
Results:
Partial resistance to mitomycin C after low-dose mitomycin C pre-treatment was significantly neutralised by the addition of verapamil. Low-dose mitomycin C up-regulated P-glycoprotein expression, but not mdr-1 mRNA expression. 5-Fluorouracil did not induce P-glycoprotein expression. P-glycoprotein expression was detected in all nine patients exposed to mitomycin C during previous trabeculectomies. Only six of 21 specimens from patients not previously exposed to mitomycin C showed faint P-glycoprotein expression.
Conclusion:
The induction of P-glycoprotein by mitomycin C could explain some failures that occur after repeated use of mitomycin C during trabeculectomy. The concomitant use of verapamil or the use of 5-fluorouracil alone could increase the success rate of repeat trabeculectomies.
Insights
Mitomycin C treatment can cause drug resistance in eye surgery by increasing P-glycoprotein. Verapamil or 5-fluorouracil may improve success rates in repeat trabeculectomies.
Area of Science:
- Ophthalmology
- Cell Biology
- Molecular Biology
Background:
- Trabeculectomy is a glaucoma surgery that sometimes fails despite using mitomycin C.
- Investigating the development of multidrug resistance in Tenon fibroblasts due to mitomycin C exposure.
Purpose of the Study:
- To determine if low-dose mitomycin C induces a multidrug resistance phenotype in human Tenon fibroblasts in vitro.
- To assess if mitomycin C treatment during prior glaucoma surgery leads to P-glycoprotein expression in vivo.
Main Methods:
- Human Tenon fibroblasts were treated with low-dose mitomycin C, then exposed to varying concentrations of mitomycin C with or without verapamil.
- P-glycoprotein expression was analyzed using flow cytometry, immunoblotting, and RT-PCR.
- Tenon tissue from patients with and without prior mitomycin C exposure was examined via immunohistochemistry.
Main Results:
- Pre-treatment with low-dose mitomycin C induced partial resistance, which was reversed by verapamil.
- Mitomycin C increased P-glycoprotein expression but not mdr-1 mRNA levels.
- P-glycoprotein was detected in Tenon tissue from patients previously treated with mitomycin C, but less so in those without prior exposure.
Conclusions:
- Mitomycin C-induced P-glycoprotein expression may contribute to trabeculectomy failures after repeated use.
- Concomitant use of verapamil or alternative agents like 5-fluorouracil could enhance the success of repeat trabeculectomies.
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