The Relationship of DNA Double-strand Break Induction to Radiosensitivity in Human Tumour Cell Lines

Abstract

Recent data suggest that the differences in radiosensitivity between cell lines can be related to differences in dsb induction (Radford 1986a). In the light of this we have set out to assess the extent to which differences in radiation survival between human tumour cell lines can be attributed to differences in dsb induction. For nine human tumour lines survival was assayed by clonogenic assay and compared with dsb induction by irradiation at ice-bath temperature as measured by neutral filter elution. The lines varied widely in their sensitivity, ranging from a sensitive neuroblastoma (surviving fraction at 2 Gy, SF2 = 0.13) to a resistant bladder carcinoma (SF2 = 0.62). Dsb induction was found to vary between the cell lines, such that resistant cells generally suffered less damage than sensitive ones. However, the relationship between damage induction and cellular sensitivity was not a simple one, and other factors which may influence sensitivity need to be invoked. These data suggest that, in human tumour cell lines, differences in radiosensitivity may at least in part be due to different levels of damage induction, but that some lines may vary in their tolerance of damage due to differences in biological characteristics such as repair capacity.

Radiosensitivity of human tumour cells is correlated with the induction but not with the repair of DNA double-strand breaks

“…For the nine tumuor cell lines tested, the number of dsb induced was found to vary by a factor of 2 from 5.75 to 11.0 Â 10 À12 dsb/Gy/ Da (Table 2), which in principle agreed with most previous studies (Kelland et al, 1988;McMillan et al, 1990;Schwartz et al, 1990Schwartz et al, , 1991Ruiz de Almodovar et al, 1994;Zaffaroni et al, 1994;Whitaker et al, 1995;Woudstra et al, 1998;Eastham et al, 2001) using either PFGE or neutral filter elution. Some authors did not mention differences in particular; however, variations were in the same order of magnitude as the above reports (Giaccia et al, 1992;Olive et al, 1994;McKay and Kefford, 1995).…”

“…Cell lines with a high number of dsb induced found to be much more sensitive than cell lines with a low number of induced dsb. This was similarly found by Ruiz de Almodovar et al (McMillan et al, 1990;Ruiz de Almodovar et al, 1994;Whitaker et al, 1995), other studies showed an insignificant trend (Schwartz et al, 1988;Giaccia et al, 1992;Zaffaroni et al, 1994;McKay and Kefford, 1995;Woudstra et al, 1998). In our study, one (LNCaP, Figure 7A) out of the nine cell lines fell off the general relationship between initial damage and cell survival indicating that the cellular radiosensitivity is eventually not only determined by the number of induced dsb but also by other still unknown factors.…”

“…High fractions of replicating cells and high retention values decrease the slope and apparently the number of induced dsb. This might well be the reason why only three out of 13 studies found a relationship between induced damage and tumour cell radiosensitivity (Kelland et al, 1988;Schwartz et al, 1988Schwartz et al, , 1990Schwartz et al, , 1991McMillan et al, 1990;Giaccia et al, 1992;Olive et al, 1994;Ruiz de Almodovar et al, 1994;Zaffaroni et al, 1994;McKay and Kefford, 1995;Whitaker et al, 1995;Woudstra et al, 1998;Eastham et al, 2001). In conclusion, GFGE is the preferable method over a standard FDR assay to measure dsb induction in tumour cells.…”

“…11 out of 13 studies reported on a variation in the number of induced dsb (Kelland et al, 1988;Schwartz et al, 1988Schwartz et al, , 1990Schwartz et al, , 1991McMillan et al, 1990;Giaccia et al, 1992;Olive et al, 1994;Ruiz de Almodovar et al, 1994;Zaffaroni et al, 1994;McKay and Kefford, 1995;Whitaker et al, 1995;Woudstra et al, 1998;Eastham et al, 2001), but only three found a correlation with cell killing (McMillan et al, 1990;Ruiz de Almodovar et al, 1994;Whitaker et al, 1995). In repair studies, a correlation between cell killing and the number of dsb was only found after short repair intervals (up to 2 h) (Schwartz et al, 1988(Schwartz et al, , 1990Giaccia et al, 1992;Zaffaroni et al, 1994), but never for nonreparable dsb.…”

The ratio of initial/residual DNA damage predicts intrinsic radiosensitivity in seven cervix carcinoma cell lines

“…However, for tumour cells, no firm consensus exists for a correlation between in vitro radiosensitivity and the magnitude of radiation-induced DNA dsb damage or repair. A number of reports indicate that tumour cell radiosensitivity is positively correlated with the levels of initial radiation-induced DNA dsbs (Kelland et al, 1988;Peacock et al, 1989;McMillan et al, 1990;Ruiz de Almodovar et al, 1994), while others have shown no correlation (Smeets et al, 1993;Olive et al, 1994;McKay and Kefford, 1995). Positive correlations between tumour cell radiosensitivity and the extent of residual DNA dsbs (Giaccia et al, 1992;Zaffaroni et al, 1994), the rate of DNA dsb repair (Schwartz et al, 1988) and the misrepair of radiation-induced DNA damage (Powell et al, 1992;Powell and McMillan, 1994) have also been reported.…”