Despite some expression of folate receptor alpha in human mesothelioma cells, internalization of methotrexate is predominantly carrier mediated.

Objective: As a response to a published report documenting some expression of folate receptor alpha in human mesothelioma, studies were carried out examining the role of this receptor versus that of the reduced folate carrier in the internalization of folate analogs in this neoplasm.

Methods: Influx measurements of tritiated methotrexate were carried out in 4 mesothelioma cell lines, and 2 additional cell lines were used as comparators. Relative gene-expression analysis for the carrier and receptor gene was done by using real-time reverse transcriptase-polymerase chain reaction in the above-mentioned cell lines and mesothelioma tumor tissues obtained from patients.