The changes in the levels of dihydrofolate reductase mRNA and its gene dosage in 5-fluorouracil-resistant L1210 cells

Intratumoral gene expression of dihydrofolate reductase and folylpoly-c-glutamate synthetase affects the sensitivity to 5-fluorouracil in non-small cell lung cancer

BACKGROUND

Various factors related to the sensitivity of non-small cell lung carcinoma (NSCLC) to 5-fluorouracil (5-FU) have been reported, and some of them have been clinically applied. In this single-institutional prospective analysis, the mRNA expression level of five folic acid-associated enzymes was evaluated in surgical specimens of NSCLC. We investigated the correlation between the antitumor effect of 5-FU in NSCLC using an anticancer drug sensitivity test and the gene expression levels of five enzymes.

MATERIALS AND METHODS

Forty patients who underwent surgery for NSCLC were enrolled, and the antitumor effect was measured using an in vitro anticancer drug sensitivity test (histoculture drug response assay) using freshly resected specimens. In the same sample, the mRNA expression levels of five enzymes involved in the sensitivity to 5-FU were measured in the tumor using real-time PCR. The expression levels and the result of the sensitivity test were compared.

RESULTS

No correlation was found between dihydropyrimidine dehydrogenase (DPD), orotate phosphoribosyltransferase (OPRT), or DPD/OPRT expression and the antitumor effects of 5-FU. On the other hand, a correlation was found between thymidylate synthase (TS), folylpoly-c-glutamate synthetase (FPGS), and dihydrofolate reductase (DHFR) expression and 5-FU sensitivity.

CONCLUSION

Expression of FPGS and DHFR may be useful for predicting the efficacy of 5-FU-based chemotherapy for NSCLC.

Lack of in vivo cross-resistance with 4'-thio-ara-C against drug-resistant murine P388 and L1210 leukemias

PURPOSE

4'-Thio-β-D-arabinofuranosylcytosine (4'-thio-ara-C), which has shown a broad spectrum of antitumor activity against human tumor systems in mice and is undergoing clinical trials, was evaluated for cross-resistance to seven clinical agents in order to identify potentially useful guides for patient selection for further clinical trials of 4'-thio-ara-C and possible noncross-resistant drug combinations with 4'-thio-ara-C.

METHODS

A drug resistance profile for 4'-thio-ara-C, which was administered intraperitoneally daily for nine consecutive days, was obtained using seven drug-resistant P388 and L1210 leukemias that were implanted intraperitoneally in mice.

RESULTS

Multidrug-resistant P388 leukemias (leukemias resistant to doxorubicin, etoposide, or paclitaxel) exhibited no cross-resistance to 4'-thio-ara-C. Leukemias resistant to camptothecin, cisplatin, and 5-fluorouracil were also not cross-resistant to 4'-thio-ara-C. Only the leukemia resistant to 1-β-D-arabinofuranosylcytosine was cross-resistant to 4'-thio-ara-C.

CONCLUSIONS

The data suggest that (1) it may be important to exclude or to monitor with extra care patients who have previously been treated with 1-β-D-arabinofuranosylcytosine and (2) the lack of cross-resistance seen with 4'-thio-ara-C may contribute to therapeutic synergism when 4'-thio-ara-C is combined with other agents.

Tumor quantification of several fluoropyrimidines resistance gene expression with a unique quantitative RT-PCR method. Implications for pretherapeutic determination of tumor resistance phenotype

Pretherapeutic determination of tumor resistance to chemotherapy is a main challenge, hindered by the low number of mechanisms characterized at the same time, the small size of the clinical specimens and the heterogeneity of the techniques or the lack of true quantification. The aim of the present study was to determine in real time quantitative RT-PCR, tumor cell expression of several transcripts involved in cancer cell resistance with a unique cDNA sample from a tumor biopsy. The technique had to be suitable in clinical practice for determination of several factors involved in resistance to a given drug family, for example, fluoropyrimidines resistance factors: thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), thymidine kinase (TK), dihydrofolate reductase (DHFR), folylpolyglutamate synthetase (FPGS). A frame-shifted artificial construct was designed specifically to work within the same conditions. We validated our technique by quantifying expressions of these 5 genes starting from tissue samples of colorectal carcinoma and the surrounding normal mucosa of 33 different patients. That real time quantitative RT-PCR technique using the frame-shifted artificial construct as a standard provided a real comparison and quantification of different resistance factors. Tumor resistance phenotype determination based on that approach will be investigated in a control study.

Chemotherapeutic drug resistance in the management of head and neck cancer

Considerable progress has been made in the development of more effective chemotherapy regimens for squamous cell head and neck carcinomas. Unfortunately, increased response rates have not been translated into marked improvements in survival since durations of response have been brief, and the natural history of the disease has ultimately remained unaltered. Since the development of drug resistance is a major obstacle to successful antineoplastic chemotherapy, comprehensive efforts have been focused on understanding the underlying mechanisms. In this review, general and specific aspects of drug resistance related to head and neck cancer are addressed. In particular, mechanisms of resistance towards the most widely used antineoplastic drugs in head and neck malignancies--methotrexate, cisplatin, 5-fluorouracil, bleomycin, and vincristine--are discussed.