The use of non-clonogenic assays in measuring the response of cells in vitro to ionising radiation

Determination of cell survival after irradiation via clonogenic assay versus multiple MTT Assay--a comparative study

For studying proliferation and determination of survival of cancer cells after irradiation, the multiple MTT assay, based on the reduction of a yellow water soluble tetrazolium salt to a purple water insoluble formazan dye by living cells was modified from a single-point towards a proliferation assay. This assay can be performed with a large number of samples in short time using multi-well-plates, assays can be performed semi-automatically with a microplate reader. Survival, the calculated parameter in this assay, is determined mathematically. Exponential growth in both control and irradiated groups was proven as the underlying basis of the applicability of the multiple MTT assay. The equivalence to a clonogenic survival assay with its disadvantages such as time consumption was proven in two setups including plating of cells before and after irradiation. Three cell lines (A 549, LN 229 and F 98) were included in the experiment to study its principal and general applicability.

Establishment and characterization of chronic-hypoxia-resistant gastric cancer cell line MNK45/HYP

The chronic-hypoxia-resistant gastric cancer cell line was established, and its biological characteristics were explored and compared with the parental cell line. Gastric cancer cell lines were cultured under the degressive oxygen concentration. Cell doubling time was calculated by cell counting method. Chemo-resistance ability of cells was tested by MTT assay. Irradiation tolerance of cells was evaluated by colony forming method. Cell cycle distribution was tested with flow cytometry. Invasive ability was tested by Transwell method. The expression levels of GLUT-1 and HIF-1α were detected by using Western blot. MNK45/HYP cells successfully survived under the 1% concentration of oxygen and its cell doubling time was 35.01±1.02 h, while that of MNK45 was 27.35±0.83 h (P<0.01). The percentage of MNK45/HYP cells in G(0)/G(1) stage was (58.3±6.1)%, and that of MNK45 cells was (42.2±6.0)% (P<0.05). Comparing with the parental cells MNK45, drug resistance indexes of 5-Fu, PTX, OXA, Sn38, GEM and VP16 in MNK45/HYP cells were respectively 5.3, 1.3, 3.6, 2.2, 4.8 and 4.4. Colony forming ability of MNK45/HYP cells after irradiation was also significantly higher than MNK45 cells. The invasive number of MNK45/HYP cells was 107.7±17.5, while that of MNK45 cells was 59.0±9.9. The expression levels of GLUT-1 and HIF-1α in MNK45/HYP cells were significantly higher than those in MNK45 cells. MNK45/HYP cells hold biological characteristics of hypoxia tumor with good tolerance to chronic hypoxia, and can be used for the research of solid tumor under chronic hypoxia condition.

Comparison between the clonogenic, MTT, and SRB assays for determining radiosensitivity in a panel of human bladder cancer cell lines and a ureteral cell line

Using a series of human bladder cancer cell lines and an immortalised normal ureteral cell line, radiosensitivities measured by three different methods after a single dose of X-radiation are compared. Clear differences between cell survival curves obtained using the clonogenic, microtetrazoline (MTT) and sulforhodamine B (SRB) assays are shown. The most sensitive of the assays investigated was the clonogenic assay. The MTT and SRB assays were found to be relatively insensitive especially at lower radiation levels, suggesting that these assays may not be suitable for predicting therapeutic dose schedules in vivo, but will be important for investigating radio-sensitivity in cell lines with very low plating efficiencies. Each assay discriminated between a range of sensitivities in the cell lines examined, and with some minor differences, the ordering of sensitivities using the three assays was similar. Possible explanations for the differences between results obtained with the three assays are discussed.

Cellular radiosensitivity of small-cell lung cancer cell lines

PURPOSE

The objective of this study was to determine the radiobiological characteristics of a panel of small-cell lung cancer (SCLC) cell lines by use of a clonogenic assay. In addition, we tested whether comparable results could be obtained by employing a growth extrapolation method based on the construction of continuous exponential growth curves.

METHODS AND MATERIALS

Fifteen SCLC cell lines were studied, applying a slightly modified clonogenic assay and a growth extrapolation method. A dose-survival curve was obtained for each experiment and used for calculating several survival parameters. The multitarget single hit model was applied to calculate the cellular radiosensitivity (D0), the capacity for sublethal damage repair (Dq), and the extrapolation number (n). Values for alpha and beta were determined from best-fit curves according to the linear-quadratic model and these values were applied to calculate the surviving fraction after 2-Gy irradiation (SF2).

RESULTS

In our investigation, the extrapolation method proved to be inappropriate for the study of in vitro cellular radiosensitivity due to lack of reproducibility. The results obtained by the clonogenic assay showed that the cell lines studied were radiobiologically heterogeneous with no discrete features of the examined parameters including the repair capacity.

CONCLUSION

The results indicate that SCLC tumors per se are not generally candidates for hyperfractionated radiotherapy.