DNA damage induced by cis- and carboplatin as indicator for in vitro sensitivity of ovarian carcinoma cells

Abstract

Background: The DNA damage by platinum cytostatics is thought to be the main cause of their cytotoxicity. Therefore the measurement of the DNA damage induced by cis- and carboplatin should reflect the sensitivity of cancer cells toward the platinum chemotherapeutics.

Methods: DNA damage induced by cis- and carboplatin in primary cells of ovarian carcinomas was determined by the alkaline comet assay. In parallel, the reduction of cell viability was measured by the fluorescein diacetate (FDA) hydrolysis assay.

Results: While in the comet assay the isolated cells showed a high degree of DNA damage after a 24 h treatment, cell viability revealed no cytotoxicity after that incubation time. The individual sensitivities to DNA damage of 12 tumour biopsies differed up to a factor of about 3. DNA damage after a one day treatment with cis- or carboplatin correlated well with the cytotoxic effects after a 7 day treatment (r = 0,942 for cisplatin r = 0.971 for carboplatin). In contrast to the platinum compounds the correlation of DNA damage and cytotoxicity induced by adriamycin was low (r = 0,692), or did not exist for gemcitabine.

Conclusion: The measurement of DNA damage induced by cis- and carboplatin is an accurate method to determine the in vitro chemosensitivity of ovarian cancer cells towards these cytostatics, because of its quickness, sensitivity, and low cell number needed.

Figure 1

Time dependent DNA damage (black square) presented as median with first and third quartile and cytotoxicity (black triangle) presented as mean with standard deviation induced by 100% SPK cisplatin (A), or 100% SPK carboplatin (B) in primary ovarian carcinoma cells. DNA damage is shown as reduction of MMS induced tail moments (tm) by the platinum compound (50 comets/sample evaluated). MMS alone induced a tail moment ranging from 80-90. The platinum compounds alone induced no tail moments.

Figure 2

Concentration dependent DNA damage (black square) presented as median with first and third quantile, and cytotoxicity (black triangle) presented as mean with standard deviation, induced by cisplatin (A), or carboplatin (B). DNA damage was measured after a 24 h incubation, cytotoxicity after a 7 day incubation with the cytostatics. MMS alone induced a tail moment ranging from 80-90. The platinum compounds alone induced no tail moments.

Figure 3

DNA damage by a 24 hour incubation of cisplatin (white bars) and carboplatin (dark bars) in ovarial cancer cells from 12 biopsies presented as median with first and third quartile. The platinum concentration was 50% peak serum. MMS alone induced a tail moment ranging from 80-90. The platinum compounds alone induced no tail moments.

Figure 4

Concentration dependent DNA damage (black square) presented as median with first and third quartile, and cytotoxicity (black triangle) presented as mean with standard deviation, induced by adriamycin (A) and gemcitabine (B). DNA damage was measured after a 24 h incubation, cytotoxicity after a 7 day incubation.

Figure 5

Correlation of DNA damage in ovarian cancer cells induced by cisplatin (A) (24 h treatment; r = 0,9422), or carboplatin (B) (24 h treatment; r = 0,9711) and cytotoxicity (induced by a 7 day treatment). Data were obtained from 12 biopsies.

Figure 6

Correlation of DNA damage induced by adriamycin (A) (24 h treatment; r = 0,6918), or gemcitabine (B) (24 h treatment) and cytotoxicity (induced by a 7 day treatment). Data were obtained from 7 biopsies.