In vitro chemosensitivity of freshly explanted tumor cells to pemetrexed is correlated with target gene expression.
OBJECTIVE
mRNA expression of genes involved in the mechanism of action of pemetrexed was correlated with in vitro chemosensitivity of freshly explanted human tumor specimens.


METHODS
Chemosensitivity to pemetrexed was studied in soft-agar. Multiplex rtPCR experiments for reduced folate carrier (RFC), folate receptor-alpha (FR-alpha), folylpolyglutamate synthetase (FPGS), thymidylate synthase (TS), dihydrofolate reductase (DHFR), glycinamide ribonucleotide formyl transferase (GARFT), mrp4, and mrp5 were performed in parallel. Correlations, threshold optimization, sensitivity, specificity, and efficiency were analyzed using the appropriate statistical methodologies.


RESULTS
In 61 samples, low levels of TS, GARFT, DHFR, and mrp4 gene expression significantly correlated with chemosensitivity to pemetrexed. Optimization analyses demonstrated threshold values of 144 copies for TS and six copies for mrp4 relative to 10(4) copies of beta-actin.


CONCLUSIONS
These results form a rational basis for the design of clinical trials to evaluate the expression of these enzymes as predictors for treatment outcome.
Hanauske
Axel-Rainer
AR
Asklepios Klinik, St. Georg, Lohmühlenstr. 5, 20099 Hamburg, Germany. hanauske.ind-synergen@t-online.de
Eismann
Ulrike
U
Oberschmidt
Olaf
O
Pospisil
Heike
H
Hoffmann
Steve
S
Hanauske-Abel
Hartmut
H
Ma
Doreen
D
Chen
Victor
V
Paoletti
Paolo
P
Niyikiza
Clet
C
D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D005971:Glutamates / Q000494:pharmacology*; D006147:Guanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics; D009369:Neoplasms / Q000188:drug therapy* / Q000235:genetics*; D000068437:Pemetrexed; D051026:Phosphoribosylglycinamide Formyltransferase / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors / Q000235:genetics; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay
D000964:Antimetabolites, Antineoplastic; D005971:Glutamates; D006147:Guanine; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D000068437:Pemetrexed; D051026:Phosphoribosylglycinamide Formyltransferase; D012333:RNA, Messenger; D013762:Tetrahydrofolate Dehydrogenase; D013940:Thymidylate Synthase; C073492:ABCC4 protein, human