Cytotoxicity of antineoplastic agents on rabbit corneal epithelium in vitro

Abstract

We studied the cytotoxic effects of antineoplastic agents in vitro including cytosine arabinoside (Ara-C), methotrexate, melphalan, 5-fluorouracil (5-FU), and triethylenethiophosphoramide (thiotepa), using rabbit corneal epithelial cell primary tissue cultures. Twenty-four hour [³H]thymidine incorporation was measured 6 hr after the addition of drug or vehicle. A dose-response effect was noted for all agents. Significant (p <0.05) inhibition of thymidine incorporation was reached with Ara-C (10⁻⁷M), methotrexate (10⁻³M), melphalan (10-⁶M), 5-FU (10⁻⁴M), and thiotepa (10⁻⁴M). Visual inspection of the cultures was a less sensitive indicator of drug-induced cytotoxicity; except for melphalan, drug concentrations much greater than those that inhibited thymidine incorporation did not alter cell morphology. At a concentration of 10⁻⁴M, 2′-deoxycytidine, a competitive inhibitor of Ara-C, protected corneal epithelial cells exposed to Ara-C concentrations up to 10⁻⁵M. When used alone, concentrations of deoxycytidine greater than 10⁻⁴M were associated with significant impairment of thymidine uptake by cells. This in vitro model may be useful in quantitatively evaluating the epithelial cytotoxicity of other current and future antineoplastic agents, as a means for predicting and possibly moderating corneal toxicity of these agents clinically.