Related Experiment Videos
Relationship between topoisomerase II level and chemosensitivity in human tumor cell lines
A M Fry1, C M Chresta, S M Davies
1Imperial Cancer Research Fund, University of Oxford, John Radcliffe Hospital, United Kingdom.
Abstract:
Patients with metastatic testis tumors are generally curable using chemotherapy, whereas those with disseminated bladder carcinomas are not. We have compared levels of the nuclear enzyme topoisomerase II in three testis (SuSa, 833K, and GH) and three bladder (RT4, RT112, and HT1376) cancer cell lines which differ in their sensitivity to chemotherapeutic agents. The testis cell lines were more sensitive than the bladder lines to three drugs whose cytotoxicity is mediated in part by inhibiting topoisomerase II: amsacrine; Adriamycin; and etoposide (VP16). The frequency of DNA strand breaks induced by amsacrine was higher (1.5- to 13-fold) in the testis cells than in the bladder cells. The level of topoisomerase II-mediated DNA strand breakage in vitro, measured by filter trapping of amsacrine-induced protein:DNA cross-links, was similarly higher in nuclear extracts from the testis than the bladder cells. Western blot analysis showed a generally higher level of topoisomerase II protein in testis than in bladder cell nuclear extracts. Topoisomerase II protein expression broadly correlated with drug-induced strand breakage in both protein extracts and whole cells, but not with population doubling time. However, despite a 2- to 20-fold increased sensitivity to the different topoisomerase II inhibitors, the testis line 833K had a less than 2-fold higher level of topoisomerase II protein than that of the bladder line RT4. These results indicate that the level of expression of topoisomerase II is an important determinant of the relative chemosensitivity of testis and bladder tumor cell lines, but that additional factors must contribute to the extreme chemosensitivity of testis cells.
Insights
Testis cancer cell lines show higher sensitivity to topoisomerase II inhibitors compared to bladder cancer cells. This increased sensitivity is linked to higher topoisomerase II enzyme levels, though other factors also contribute to testis cancer
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Metastatic testis tumors are generally curable with chemotherapy, unlike disseminated bladder carcinomas.
- Chemotherapeutic agents like amsacrine, Adriamycin, and etoposide (VP16) exhibit varying efficacy against different cancer types.
- Topoisomerase II is a nuclear enzyme crucial for DNA replication and a target for several chemotherapeutic drugs.
Purpose of the Study:
- To compare the levels of topoisomerase II in testis and bladder cancer cell lines.
- To investigate the correlation between topoisomerase II levels and sensitivity to topoisomerase II-inhibiting chemotherapeutic agents.
- To explore factors contributing to the differential chemosensitivity between testis and bladder tumors.
Main Methods:
- Cultured three human testis (SuSa, 833K, GH) and three bladder (RT4, RT112, HT1376) cancer cell lines.
- Assessed cellular sensitivity to amsacrine, Adriamycin, and etoposide (VP16).
- Measured DNA strand breaks, topoisomerase II-mediated DNA strand breakage in vitro, and topoisomerase II protein levels via Western blot analysis.
Main Results:
- Testis cancer cell lines were more sensitive to amsacrine, Adriamycin, and etoposide than bladder cancer cell lines.
- Higher frequencies of drug-induced DNA strand breaks were observed in testis cells compared to bladder cells.
- Nuclear extracts from testis cell lines generally showed higher levels of topoisomerase II protein and activity than those from bladder cell lines.
Conclusions:
- Topoisomerase II protein expression is a significant determinant of chemosensitivity in testis and bladder tumor cell lines.
- While higher topoisomerase II levels contribute to increased sensitivity, other unelucidated factors are also involved in the extreme chemosensitivity of testis cells.
- The findings suggest potential therapeutic strategies targeting topoisomerase II for testis cancer treatment.