Flow cytometric evaluation of Fas expression in relation to response and resistance to anthracyclines in leukemic cells

✍ Scribed by Gilles Labroille; Patrice Dumain; Francis Lacombe; Francis Belloc

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 202 KB
• Volume: 39
• Category: Article
• ISSN: 0196-4763
• DOI: 10.1002/(sici)1097-0320(20000301)39:3<195::aid-cyto4>3.0.co;2-a

✦ Synopsis

Background: Cell chemosensitivity to cytotoxic drugs has been attributed to their ability to trigger apoptosis. The emergence of resistance in drug-exposed cells is often characterized by the appearance of drug efflux mechanisms including P-gp transport. Nevertheless, mdr1 expression may coexist with other resistance features, in particular those interfering with apoptotic signaling pathways. Methods: Leukemic cell lines cultured in a progressively toxic environment were analyzed for Fas and P-gp expression by immunostaining and flow cytometry. Their mdr1 mRNA expression level was determined by reverse transcriptase-polymerase chain reaction (RT-PCR), and their apoptotic response was microscopically evaluated. Activation of the Fas pathway was obtained by cross-linking the Fas receptor with the 7C11 anti-Fas agonist.

Results:

We demonstrate a dose-dependent Fas overexpression after short-term (18 h) incubation with daunorubicin. The subsequent sensitization to Fas activators led to a significant increase in the apoptotic response induced by 7C11. After long-term exposure to daunorubicin and acquisition of drug resistance, expression of P-gp was accompanied by a decrease in the number of Fas sites at the cell surface with a correlated desensitization to Fasinduced apoptosis. Additional alterations in the Fas signaling pathway can also be hypothesized in the most resistant Jurkat cell line.

Conclusions:

The induction of Fas expression could be one of the mechanisms of action of chemotoxic drugs and thus might enhance the cell susceptibility to Fas-mediated apoptosis. On the contrary, the emergence of the multidrug resistance phenotype is associated with a downregulation of Fas expression and possible defects in the Fas signaling pathway.