World J Oncol

World Journal of Oncology, ISSN 1920-4531 print, 1920-454X online, Open Access

Article copyright, the authors; Journal compilation copyright, World J Oncol and Elmer Press Inc

Journal website http://www.wjon.org

Original Article

Volume 6, Number 4, August 2015, pages 398-409

The Effect of p53 Status of Tumor Cells on Radiosensitivity of Irradiated Tumors With Carbon-Ion Beams Compared With γ-Rays or Reactor Neutron Beams

Figure 1. Surviving fractions and net micronucleus frequencies following γ-ray irradiation. The clonogenic cell survival curves for total tumor cell populations and the net micronucleus frequencies for total and quiescent cell populations immediately and 9 h after γ-ray irradiation with high dose-rate irradiation (HDRI) and immediately after γ-ray irradiation with reduced dose-rate irradiation (RDRI) are shown in (a) and (b), respectively. The left and right panels show SAS/neo and SAS/mp53 tumor cells, respectively. Bars represent standard errors (n = 6).

Figure 2. Surviving fractions and net micronucleus frequencies following accelerated carbon-ion beam (18 MeV/μm) irradiation. The clonogenic cell survival curves for total tumor cell populations and the net micronucleus frequencies for total and quiescent cell populations immediately and 9 h after irradiation using accelerated carbon-ion beams with a linear energy transfer of 18 MeV/μm with high dose-rate irradiation (HDRI) and immediately after irradiation with reduced dose-rate irradiation (RDRI) are shown in (a) and (b), respectively. The left and right panels show SAS/neo and SAS/mp53 tumor cells, respectively. Bars represent standard errors (n = 6).

Figure 3. Surviving fractions and net micronucleus frequencies following accelerated carbon-ion beam (50 MeV/μm) irradiation. The clonogenic cell survival curves for total tumor cell populations and the net micronucleus frequencies for total and quiescent cell populations immediately and 9 h after irradiation using accelerated carbon-ion beams with a linear energy transfer of 50 MeV/μm with high dose-rate irradiation (HDRI) and immediately after irradiation with reduced dose-rate irradiation (RDRI) are shown in (a) and (b), respectively. In addition, the cell survival curves for total cells and the net micronucleus frequencies for total and quiescent cells immediately after irradiation using reactor thermal and epithermal neutron beams are also shown in (a) and (b), respectively. The left and right panels show SAS/neo and SAS/mp53 tumor cells, respectively. Bars represent standard errors (n = 6).

**Table 1.** Plating Efficiency and Micronucleus Frequency at 0 Gy
	Total tumor cells	Quiescent cells
^aMean ± standard error (n = 6).
SAS/neo
Plating efficiency (%)	45.5 ± 8.9^a
Micronucleus frequency	0.038 ± 0.006	0.056 ± 0.007
SAS/mp53
Plating efficiency (%)	23.5 ± 4.1
Micronucleus frequency	0.072 ± 0.008	0.111 ± 0.010

Table 1. Plating Efficiency and Micronucleus Frequency at 0 Gy

Total tumor cells

Quiescent cells

^aMean ± standard error (n = 6).

SAS/neo

Plating efficiency (%)

45.5 ± 8.9^a

Micronucleus frequency

0.038 ± 0.006

0.056 ± 0.007

SAS/mp53

Plating efficiency (%)

23.5 ± 4.1

Micronucleus frequency

0.072 ± 0.008

0.111 ± 0.010

**Table 2.** Dose-Modifying Factors Due to a Delayed Assay or Reduced Irradiation Dose-Rate^a
Employed Radiation beams	High dose-rate 9 h after	Reduced dose-rate
^aThe ratio of the dose of radiation necessary to obtain each endpoint with a delayed assay or reduced dose-rate irradiation to that needed to obtain each endpoint with an assay immediately after high dose-rate irradiation. ^bMean ± standard error (n = 6).
SAS/neo
Surviving fraction = 0.03
Total cells
γ-rays	1.3 ± 0.1^b	1.4 ± 0.1
Carbon beams (18 keV/μm)	1.2 ± 0.1	1.15 ± 0.1
Carbon beams (50 keV/μm)	1.15 ± 0.1	1.1 ± 0.1
Net micronucleus frequency = 0.1
Total cells
γ-rays	1.35 ± 0.1	1.45 ± 0.1
Carbon beams (18 keV/μm)	1.15 ± 0.1	1.2 ± 0.1
Carbon beams (50 keV/μm)	1.15 ± 0.1	1.15 ± 0.1
Quiescent cells
γ-rays	1.45 ± 0.15	1.55 ± 0.15
Carbon beams (18 keV/μm)	1.3 ± 0.1	1.35 ± 0.1
Carbon beams (50 keV/μm)	1.25 ± 0.15	1.3 ± 0.1
SAS/mp53
Surviving fraction = 0.03
Total cells
γ-rays	1.05 ± 0.1^b	1.1 ± 0.1
Carbon beams (18 keV/μm)	1.05 ± 0.1	1.05 ± 0.1
Carbon beams (50 keV/μm)	1.05 ± 0.1	1.05 ± 0.1
Net micronucleus frequency = 0.1
Total cells
γ-rays	1.05 ± 0.1	1.1 ± 0.1
Carbon beams (18 keV/μm)	1.05 ± 0.1	1.1 ± 0.1
Carbon beams (50 keV/μm)	1.05 ± 0.1	1.05 ± 0.1
Quiescent cells
γ-rays	1.05 ± 0.1	1.1 ± 0.1
Carbon beams (18 keV/μm)	1.05 ± 0.1	1.1 ± 0.1
Carbon beams (50 keV/μm)	1.05 ± 0.1	1.1 ± 0.1

Table 2. Dose-Modifying Factors Due to a Delayed Assay or Reduced Irradiation Dose-Rate^a

Employed Radiation beams

High dose-rate 9 h after

Reduced dose-rate

^aThe ratio of the dose of radiation necessary to obtain each endpoint with a delayed assay or reduced dose-rate irradiation to that needed to obtain each endpoint with an assay immediately after high dose-rate irradiation. ^bMean ± standard error (n = 6).

SAS/neo

Surviving fraction = 0.03

Total cells

γ-rays

1.3 ± 0.1^b

1.4 ± 0.1

Carbon beams (18 keV/μm)

1.2 ± 0.1

1.15 ± 0.1

Carbon beams (50 keV/μm)

1.15 ± 0.1

1.1 ± 0.1

Net micronucleus frequency = 0.1

Total cells

γ-rays

1.35 ± 0.1

1.45 ± 0.1

Carbon beams (18 keV/μm)

1.15 ± 0.1

1.2 ± 0.1

Carbon beams (50 keV/μm)

1.15 ± 0.1

Quiescent cells

γ-rays

1.45 ± 0.15

1.55 ± 0.15

Carbon beams (18 keV/μm)

1.3 ± 0.1

1.35 ± 0.1

Carbon beams (50 keV/μm)

1.25 ± 0.15

1.3 ± 0.1

SAS/mp53

Surviving fraction = 0.03

Total cells

γ-rays

1.05 ± 0.1^b

1.1 ± 0.1

Carbon beams (18 keV/μm)

1.05 ± 0.1

Carbon beams (50 keV/μm)

1.05 ± 0.1

Net micronucleus frequency = 0.1

Total cells

γ-rays

1.05 ± 0.1

1.1 ± 0.1

Carbon beams (18 keV/μm)

1.05 ± 0.1

1.1 ± 0.1

Carbon beams (50 keV/μm)

1.05 ± 0.1

Quiescent cells

γ-rays

1.05 ± 0.1

1.1 ± 0.1

Carbon beams (18 keV/μm)

1.05 ± 0.1

1.1 ± 0.1

Carbon beams (50 keV/μm)

1.05 ± 0.1

1.1 ± 0.1

**Table 3.** Dose-Modifying Factors for SAS/mp53 Relative to SAS/neo Tumor Cells^a
High dose-rate immediately after	High dose-rate 9 h after	Reduced dose-rate
^aThe ratio of the physical radiation dose of external beams necessary to obtain each endpoint in SAS/mp53 tumor cells to that needed to obtain each endpoint in SAS/neo tumor cells. ^bMean ± standard error (n = 6).
Surviving fraction = 0.03
Total cells
γ-rays (1.35 ± 0.1^b)	1.15± 0.1	1.1 ± 0.1
Carbon beams (18 keV/μm) (1.35 ± 0.1^b)	1.1 ± 0.1	1.05 ± 0.1
Carbon beams (50 keV/μm) (1.1 ± 0.1)	1.05 ± 0.1	1.0 ± 0.1
Thermal beams		1.1 ± 0.1
Epithermal beams		1.05 ± 0.1

Table 3. Dose-Modifying Factors for SAS/mp53 Relative to SAS/neo Tumor Cells^a

High dose-rate immediately after

High dose-rate 9 h after

Reduced dose-rate

^aThe ratio of the physical radiation dose of external beams necessary to obtain each endpoint in SAS/mp53 tumor cells to that needed to obtain each endpoint in SAS/neo tumor cells. ^bMean ± standard error (n = 6).

Surviving fraction = 0.03

Total cells

γ-rays (1.35 ± 0.1^b)

1.15± 0.1

1.1 ± 0.1

Carbon beams (18 keV/μm) (1.35 ± 0.1^b)

1.1 ± 0.1

1.05 ± 0.1

Carbon beams (50 keV/μm) (1.1 ± 0.1)

1.05 ± 0.1

1.0 ± 0.1

Thermal beams

1.1 ± 0.1

Epithermal beams

1.05 ± 0.1

**Table 4.** Relative Biological Effectiveness for Carbon Beams Compared With γ-Rays^a in Total and Quiescent Tumor Cells
LET values of carbon beams	High dose-rate immediately after	High dose-rate 9 h after	Reduced dose-rate
^aRatio of radiation dose necessary to obtain each endpoint with γ-rays and radiation dose necessary to obtain each endpoint with carbon-ion beams. ^bMean ± standard error (n = 6).
SAS/neo
Surviving fraction = 0.03
Total cells
18 keV/μm	1.35 ± 0.1^b	1.5 ± 0.15	1.5 ± 0.15
50 keV/μm	2.2 ± 0.2	2.6 ± 0.25	2.6 ± 0.25
Thermal			3.2 ± 0.3
Epithermal			3.7 ± 0.35
Net micronucleus frequency = 0.1
Total cells
18 keV/μm	1.6 ± 0.15	1.7 ± 0.15	1.7 ± 0.15
50 keV/μm	1.85 ± 0.2	2.45 ± 0.25	2.6 ± 0.25
Thermal			4.2 ± 0.4
Epithermal			4.7 ± 0.45
Quiescent cells
18 keV/μm	1.9 ± 0.2	2.4 ± 0.25	2.4 ± 0.25
50 keV/μm	3.45 ± 0.35	4.2 ± 0.4	5.0 ± 0.5
Thermal			6.4 ± 0.65
Epithermal			7.3 ± 0.75
SAS/mp53
Surviving fraction = 0.03
Total cells
18 keV/μm	1.6 ± 0.15^b	1.6 ± 0.15	1.65 ± 0.15
50 keV/μm	2.65 ± 0.25	2.65 ± 0.25	2.7 ± 0.25
Thermal			3.1 ± 0.3
Epithermal			3.3 ± 0.35
Net micronucleus frequency = 0.1
Total cells
18 keV/μm	1.25 ± 0.1	1.2 ± 0.1	1.2 ± 0.1
50 keV/μm	1.3 ± 0.15	1.35 ± 0.15	1.4 ± 0.15
Thermal			2.3 ± 0.25
Epithermal			2.45 ± 0.25
Quiescent cells
18 keV/μm	2.05 ± 0.2	2.4 ± 0.25	2.4 ± 0.25
50 keV/μm	1.6 ± 0.15	1.75 ± 0.15	1.85 ± 0.2
Thermal			3.8 ± 0.4
Epithermal			4.2 ± 0.4

Table 4. Relative Biological Effectiveness for Carbon Beams Compared With γ-Rays^a in Total and Quiescent Tumor Cells

LET values of carbon beams

High dose-rate immediately after

High dose-rate 9 h after

Reduced dose-rate

^aRatio of radiation dose necessary to obtain each endpoint with γ-rays and radiation dose necessary to obtain each endpoint with carbon-ion beams. ^bMean ± standard error (n = 6).

SAS/neo

Surviving fraction = 0.03

Total cells

18 keV/μm

1.35 ± 0.1^b

1.5 ± 0.15

50 keV/μm

2.2 ± 0.2

2.6 ± 0.25

Thermal

3.2 ± 0.3

Epithermal

3.7 ± 0.35

Net micronucleus frequency = 0.1

Total cells

18 keV/μm

1.6 ± 0.15

1.7 ± 0.15

50 keV/μm

1.85 ± 0.2

2.45 ± 0.25

2.6 ± 0.25

Thermal

4.2 ± 0.4

Epithermal

4.7 ± 0.45

Quiescent cells

18 keV/μm

1.9 ± 0.2

2.4 ± 0.25

50 keV/μm

3.45 ± 0.35

4.2 ± 0.4

5.0 ± 0.5

Thermal

6.4 ± 0.65

Epithermal

7.3 ± 0.75

SAS/mp53

Surviving fraction = 0.03

Total cells

18 keV/μm

1.6 ± 0.15^b

1.6 ± 0.15

1.65 ± 0.15

50 keV/μm

2.65 ± 0.25

2.7 ± 0.25

Thermal

3.1 ± 0.3

Epithermal

3.3 ± 0.35

Net micronucleus frequency = 0.1

Total cells

18 keV/μm

1.25 ± 0.1

1.2 ± 0.1

50 keV/μm

1.3 ± 0.15

1.35 ± 0.15

1.4 ± 0.15

Thermal

2.3 ± 0.25

Epithermal

2.45 ± 0.25

Quiescent cells

18 keV/μm

2.05 ± 0.2

2.4 ± 0.25

50 keV/μm

1.6 ± 0.15

1.75 ± 0.15

1.85 ± 0.2

Thermal

3.8 ± 0.4

Epithermal

4.2 ± 0.4

**Table 5.** Dose-Modifying Factors for Quiescent Relative to Total Tumor Cells^a at Net Micronucleus Frequency of 0.1
High dose-rate immediately after	High dose-rate 9 h after	Reduced dose-rate
^aThe ratio of the dose of radiation necessary to obtain each endpoint in the quiescent cell population to that needed to obtain each endpoint in the total tumor cell population. ^bMean ± standard error (n = 6).
SAS/neo
γ-rays (2.3 ± 0.25^b)	2.35 ± 0.25	2.4 ± 0.25
Carbon beams (18 keV/μm) (2.0 ± 0.2)	1.7 ± 0.15	1.65 ± 0.15
Carbon beams (50 keV/μm) (1.9 ± 0.1)	1.75 ± 0.15	1.9 ± 0.2
Thermal beams		1.2 ± 0.1
Epithermal beams		1.1 ± 0.1
SAS/mp53
γ-rays (2.0 ± 0.2^b)	2.0 ± 0.2	2.0 ± 0.2
Carbon beams (18 keV/μm) (1.25 ± 0.15)	1.3 ± 0.1	1.3 ± 0.15
Carbon beams (50 keV/μm) (1.0 ± 0.1)	1.0 ± 0.1	1.0 ± 0.1
Thermal beams		1.2 ± 0.1
Epithermal beam		1.15 ± 0.1

Table 5. Dose-Modifying Factors for Quiescent Relative to Total Tumor Cells^a at Net Micronucleus Frequency of 0.1

High dose-rate immediately after

High dose-rate 9 h after

Reduced dose-rate

^aThe ratio of the dose of radiation necessary to obtain each endpoint in the quiescent cell population to that needed to obtain each endpoint in the total tumor cell population. ^bMean ± standard error (n = 6).

SAS/neo

γ-rays (2.3 ± 0.25^b)

2.35 ± 0.25

2.4 ± 0.25

Carbon beams (18 keV/μm) (2.0 ± 0.2)

1.7 ± 0.15

1.65 ± 0.15

Carbon beams (50 keV/μm) (1.9 ± 0.1)

1.75 ± 0.15

1.9 ± 0.2

Thermal beams

1.2 ± 0.1

Epithermal beams

1.1 ± 0.1

SAS/mp53

γ-rays (2.0 ± 0.2^b)

2.0 ± 0.2

Carbon beams (18 keV/μm) (1.25 ± 0.15)

1.3 ± 0.1

1.3 ± 0.15

Carbon beams (50 keV/μm) (1.0 ± 0.1)

1.0 ± 0.1

Thermal beams

1.2 ± 0.1

Epithermal beam

1.15 ± 0.1