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Development of MeCCNU-resistance in clonally derived lines of Lewis lung carcinoma
T J McMillan1, T C Stephens, J H Peacock
1Radiotherapy Research Unit, Institute of Cancer Research, Sutton, Surrey, U.K.
Abstract:
The development of resistance to MeCCNU in four clonal lines of Lewis lung carcinoma derived from lung colonies has been examined. Treatment of the clones with 15 mg/kg MeCCNU once in each in vivo passage resulted in a rapid reduction in tumour responsiveness to this drug. This shows that MeCCNU resistance can arise at rates which may be applicable in spontaneous tumours and their metastases. Karyotypic heterogeneity was evident very early after isolation of the clones and this has potentially important implications for the experimental use of clones and for the features of metastatic disease. Karyotype analysis of one of the clones at each passage suggested that development of resistance was associated with the selection of a single sub-population of tumour cells but the kinetics of resistance development cannot be totally explained in terms of this simple selection.
Insights
This study shows that Lewis lung carcinoma rapidly develops resistance to MeCCNU chemotherapy. Tumor cells exhibit early karyotypic heterogeneity, complicating simple selection models for resistance development.
Area of Science:
- Oncology
- Cancer Biology
- Pharmacology
Background:
- Lewis lung carcinoma is a model for studying cancer drug resistance.
- MeCCNU (Semustine) is a chemotherapy agent used in cancer treatment.
- Understanding resistance mechanisms is crucial for improving therapeutic outcomes.
Purpose of the Study:
- To investigate the development of MeCCNU resistance in Lewis lung carcinoma.
- To analyze the role of karyotypic heterogeneity in drug resistance.
- To explore the kinetics of resistance development in clonal tumor lines.
Main Methods:
- Derivation of four clonal lines of Lewis lung carcinoma from lung colonies.
- In vivo treatment of clones with MeCCNU (15 mg/kg) during serial passages.
- Karyotype analysis of tumor cells at each passage to assess genetic heterogeneity.
Main Results:
- Rapid reduction in tumor responsiveness to MeCCNU observed after treatment.
- Early and evident karyotypic heterogeneity within the clonal lines.
- Resistance development suggested association with a specific sub-population, but kinetics were complex.
Conclusions:
- MeCCNU resistance can emerge rapidly, mirroring rates in spontaneous tumors and metastases.
- Karyotypic heterogeneity has significant implications for experimental cancer models and metastatic disease.
- Simple clonal selection may not fully explain the complex kinetics of acquired drug resistance.