RRM1 modulated in vitro and in vivo efficacy of gemcitabine and platinum in non-small-cell lung cancer.
OBJECTIVE
RRM1 encodes the regulatory subunit of ribonucleotide reductase and is a molecular target of gemcitabine. Previous studies showed increased RRM1 expression on continuous exposure of cell lines to gemcitabine and suggested improved survival for patients with low as opposed to high tumoral RRM1 expression when treated with gemcitabine-containing chemotherapy. However, the principal hypothesis that intratumoral levels of gene expression are associated with disease response has not been addressed.


METHODS
We constructed genetically modified lung cancer cell lines with increased and decreased RRM1 expression to investigate the in vitro 50% inhibitory concentration (IC50) for gemcitabine, cisplatin, and carboplatin. A prospective phase II clinical trial in patients with locally advanced non-small-cell lung cancer was conducted with pretreatment tumor collection for determination of RRM1 and ERCC1 expression by real-time reverse transcriptase polymerase chain reaction. The levels of gene expression were correlated with tumor response after two cycles of gemcitabine and carboplatin.


RESULTS
In cell lines with a genetically engineered 15-fold RRM1 expression range, the gemcitabine IC50 had a 100-fold range, and the cisplatin and carboplatin IC50 had a two-fold range. They were highest in constructs with high RRM1 expression. In the prospective clinical trial, RRM1 expression was significantly (P = .002) and inversely correlated (r = -0.498) with disease response. ERCC1 expression showed a similar trend (P = .099).


CONCLUSIONS
The results strongly suggest that tumoral RRM1 expression is a major predictor of disease response to gemcitabine/platinum chemotherapy. ERCC1 expression is predictive of response albeit to a lesser degree.
Bepler
Gerold
G
H. Lee Moffitt Cancer Center and Research Institute, MRC-4W, Room 4046, 12902 Magnolia Dr, Tampa, FL 33612-9497, USA. beplerg@moffitt.usf.edu
Kusmartseva
Irina
I
Sharma
Swati
S
Gautam
Ashish
A
Cantor
Alan
A
Sharma
Anupama
A
Simon
George
G
D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D016190:Carboplatin / Q000008:administration & dosage; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000235:genetics*; D002945:Cisplatin / Q000008:administration & dosage; D004268:DNA-Binding Proteins / Q000378:metabolism; D003841:Deoxycytidine / Q000008:administration & dosage / Q000031:analogs & derivatives; D004720:Endonucleases / Q000378:metabolism; D020869:Gene Expression Profiling; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000235:genetics*; D011237:Predictive Value of Tests; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012262:Ribonucleoside Diphosphate Reductase; D016019:Survival Analysis; D016896:Treatment Outcome; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins / Q000378:metabolism*; D000093542:Gemcitabine
D004268:DNA-Binding Proteins; D025521:Tumor Suppressor Proteins; D003841:Deoxycytidine; D016190:Carboplatin; C475286:RRM1 protein, human; D012262:Ribonucleoside Diphosphate Reductase; C071447:ERCC1 protein, human; D004720:Endonucleases; D002945:Cisplatin; D000093542:Gemcitabine