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 2, Number 1, February 2011, pages 1-9

Radiosensitivity and Capacity to Recover from Radiation-Induced Damage in Pimonidazole-Unlabeled Intratumor Quiescent Cells Depend on p53 Status

Figure 1. Cell survival curves for the whole tumor cell fraction in the total tumor cell population of SAS/neo (left panel) and SAS/mp53 (right panel) tumors as a function of radiation dose. Circles, triangles and squares represent the surviving fractions immediately after (I.A.), at 24 h after (24h later) high dose-rate (HDR), and reduced dose-rate (RDR) γ-ray irradiation, respectively. Bars represent standard errors.

Figure 2. Dose response curves of the normalized micronucleus frequency for the whole tumor cell fraction in the total and quiescent (Q) tumor cell populations of SAS/neo (left panel) and SAS/mp53 (right panel) tumors as a function of radiation dose. Open and solid symbols represent the normalized micronucleus frequencies for total and quiescent tumor cell populations, respectively. Circles, triangles and squares represent the normalized micronucleus frequency immediately after (I.A.), at 24 h after (24h later) high dose-rate (HDR), and reduced dose-rate (RDR) γ-ray irradiation, respectively. Bars represent standard errors.

Figure 3. Dose response curves for the normalized apoptosis frequency of the total and quiescent (Q) tumor cell populations of SAS/neo (left panel) and SAS/mp53 (right panel) tumors as a function of radiation dose are shown in the upper and lower panels, respectively. Open and solid symbols represent the normalized apoptosis frequencies for the whole tumor cell fraction and the cell fraction not labeled with pimonidazole (Pimo (-)) in both the total and Q tumor cell populations, respectively. Circles, triangles and squares represent the normalized apoptosis frequency immediately after (I.A.), at 24 h after (24h later) high dose-rate (HDR), and reduced dose-rate (RDR) γ-ray irradiation, respectively. Bars represent standard errors.

**Table 1.** Plating Efficiency and Micronucleus Frequency at 0 Gy
	Total tumor cells	Quiescent cells
a): Mean ± standard error (n = 9)
SAS/neo
Plating efficiency (%)	45.5 ± 8.9^a)
Micronucleus frequency	0.038 ± 0.006	0.056 ± 0.007
Apoptosis frequency	0.083 ± 0.008	0.106 ± 0.015
Especially in pimonidazole unlabeled cell fraction	0.045 ± 0.005	0.058 ± 0.008
SAS/mp53
Plating efficiency (%)	23.5 ± 4.1
Micronucleus frequency	0.072 ± 0.008	0.111 ± 0.010
Apoptosis frequency	0.021 ± 0.003	0.033 ± 0.004
Especially in pimonidazole unlabeled cell fraction	0.011 ± 0.001	0.019 ± 0.003

Table 1. Plating Efficiency and Micronucleus Frequency at 0 Gy

Total tumor cells

Quiescent cells

a): Mean ± standard error (n = 9)

SAS/neo

Plating efficiency (%)

45.5 ± 8.9^a)

Micronucleus frequency

0.038 ± 0.006

0.056 ± 0.007

Apoptosis frequency

0.083 ± 0.008

0.106 ± 0.015

Especially in pimonidazole unlabeled cell fraction

0.045 ± 0.005

0.058 ± 0.008

SAS/mp53

Plating efficiency (%)

23.5 ± 4.1

Micronucleus frequency

0.072 ± 0.008

0.111 ± 0.010

Apoptosis frequency

0.021 ± 0.003

0.033 ± 0.004

Especially in pimonidazole unlabeled cell fraction

0.011 ± 0.001

0.019 ± 0.003

**Table 2.** Dose-Modifying Factors for the Pimonidazole-Unlabeled Cell Fraction Compared with the All Cell Fraction in the Total or Quiescent Cell Population^a)
	High dose-rate Immediately after	High dose-rate 24 hours after	Reduced dose-rate
a): The ratio of the dose of radiation necessary to obtain the normalized apoptosis frequency of 0.05 in a whole cell fraction to that needed to obtain the frequency in the pimonidazole unlabeled cell fraction.
b): Mean ± standard error (n = 9)
SAS/neo
Total cell population	1.45 ± 0.15^b)	1.45 ± 0.15	1.45 ± 0.15
Quiescent cell population	1.6 ± 0.2	1.55 ± 0.15	1.55 ± 0.15
SAS/mp53
Total cell population	1.5 ± 0.15	1.5 ± 0.15	1.5 ± 0.15
Quiescent cell population	1.8 ± 0.25	1.75 ± 0.2	1.7 ± 0.2

Table 2. Dose-Modifying Factors for the Pimonidazole-Unlabeled Cell Fraction Compared with the All Cell Fraction in the Total or Quiescent Cell Population^a)

High dose-rate Immediately after

High dose-rate 24 hours after

Reduced dose-rate

a): The ratio of the dose of radiation necessary to obtain the normalized apoptosis frequency of 0.05 in a whole cell fraction to that needed to obtain the frequency in the pimonidazole unlabeled cell fraction.

b): Mean ± standard error (n = 9)

SAS/neo

Total cell population

1.45 ± 0.15^b)

1.45 ± 0.15

Quiescent cell population

1.6 ± 0.2

1.55 ± 0.15

SAS/mp53

Total cell population

1.5 ± 0.15

Quiescent cell population

1.8 ± 0.25

1.75 ± 0.2

1.7 ± 0.2

**Table 3.** Dose-Modifying Factors due to a Delayed Assay or Reduced Irradiation Dose-Rate^a)
	High dose-rate 24 hours after	Reduced dose-rate
a): The ratio of the dose of radiation necessary to obtain each end-point with a delayed assay or reduced dose-rate irradiation to that needed to obtain each end-point with an assay immediately after high dose-rate irradiation.
b): Mean ± standard error (n = 9)
SAS/neo
Surviving fraction = 0.2
Total cells	1.1 ± 0.05^b)	1.2 ± 0.1
Normalized micronucleus frequency = 0.1
Total cells	1.15 ± 0.05	1.25 ± 0.1
Quiescent cells	1.3 ± 0.1	1.6 ± 0.2
Normalized apoptosis frequency = 0.05
Total cells	1.15 ± 0.05	1.25 ± 0.1
Especially in pimonidazole unlabeled cell fraction	1.15 ± 0.05	1.3 ± 0.1
Quiescent cells	1.2 ± 0.1	1.4 ± 0.15
Especially in pimonidazole unlabeled cell fraction	1.35 ± 0.15	1.6 ± 0.2
SAS/mp53
Surviving fraction = 0.2
Total cells	1.05 ± 0.05	1.1 ± 0.05
Normalized micronucleus frequency = 0.1
Total cells	1.05 ± 0.05	1.1 ± 0.05
Quiescent cells	1.1 ± 0.05	1.15 ± 0.05
Normalized apoptosis frequency = 0.05>
Total cells	1.1 ± 0.05	1.15 ± 0.05
Especially in pimonidazole unlabeled cell fraction	1.15 ± 0.05	1.2 ± 0.1
Quiescent cells	1.15 ± 0.05	1.2 ± 0.1
Especially in pimonidazole unlabeled cell fraction	1.25 ± 0.1	1.3 ± 0.1

Table 3. Dose-Modifying Factors due to a Delayed Assay or Reduced Irradiation Dose-Rate^a)

High dose-rate 24 hours after

Reduced dose-rate

a): The ratio of the dose of radiation necessary to obtain each end-point with a delayed assay or reduced dose-rate irradiation to that needed to obtain each end-point with an assay immediately after high dose-rate irradiation.

b): Mean ± standard error (n = 9)

SAS/neo

Surviving fraction = 0.2

Total cells

1.1 ± 0.05^b)

1.2 ± 0.1

Normalized micronucleus frequency = 0.1

Total cells

1.15 ± 0.05

1.25 ± 0.1

Quiescent cells

1.3 ± 0.1

1.6 ± 0.2

Normalized apoptosis frequency = 0.05

Total cells

1.15 ± 0.05

1.25 ± 0.1

Especially in pimonidazole unlabeled cell fraction

1.15 ± 0.05

1.3 ± 0.1

Quiescent cells

1.2 ± 0.1

1.4 ± 0.15

Especially in pimonidazole unlabeled cell fraction

1.35 ± 0.15

1.6 ± 0.2

SAS/mp53

Surviving fraction = 0.2

Total cells

1.05 ± 0.05

1.1 ± 0.05

Normalized micronucleus frequency = 0.1

Total cells

1.05 ± 0.05

1.1 ± 0.05

Quiescent cells

1.1 ± 0.05

1.15 ± 0.05

Normalized apoptosis frequency = 0.05>

Total cells

1.1 ± 0.05

1.15 ± 0.05

Especially in pimonidazole unlabeled cell fraction

1.15 ± 0.05

1.2 ± 0.1

Quiescent cells

1.15 ± 0.05

1.2 ± 0.1

Especially in pimonidazole unlabeled cell fraction

1.25 ± 0.1

1.3 ± 0.1

**Table 4.** Dose-Modifying Factors for Quiescent Cell Population Relative to Total Tumor Cell Population^a)
	High dose-rate Immediately after	High dose-rate 24 hours after	Reduced dose-rate
a): The ratio of the dose of radiation necessary to obtain each end-point in the quiescent cell population to that needed to obtain each end-point in the total tumor cell population.
b): Mean ± standard error (n = 9)
SAS/neo
Normalized micronucleus frequency = 0.1	2.0 ± 0.2^b)	2.35 ± 0.2	2.65 ± 0.25
Normalized apoptosis frequency = 0.05	1.7 ± 0.15	1.75 ± 0.2	1.85 ± 0.2
Especially in pimonidazole unlabeled cell fraction	1.55 ± 0.1	1.6 ± 0.15	1.65 ± 0.15
SAS/mp53
Normalized micronucleus frequency = 0.1	1.8 ± 0.2	1.8 ± 0.2	1.85 ± 0.2
Normalized apoptosis frequency = 0.05	1.65 ± 0.15	1.7 ± 0.15	1.75 ± 0.2
Especially in pimonidazole unlabeled cell fraction	1.5 ± 0.1	1.55 ± 0.1	1.6 ± 0.15

Table 4. Dose-Modifying Factors for Quiescent Cell Population Relative to Total Tumor Cell Population^a)

High dose-rate Immediately after

High dose-rate 24 hours after

Reduced dose-rate

a): The ratio of the dose of radiation necessary to obtain each end-point in the quiescent cell population to that needed to obtain each end-point in the total tumor cell population.

b): Mean ± standard error (n = 9)

SAS/neo

Normalized micronucleus frequency = 0.1

2.0 ± 0.2^b)

2.35 ± 0.2

2.65 ± 0.25

Normalized apoptosis frequency = 0.05

1.7 ± 0.15

1.75 ± 0.2

1.85 ± 0.2

Especially in pimonidazole unlabeled cell fraction

1.55 ± 0.1

1.6 ± 0.15

1.65 ± 0.15

SAS/mp53

Normalized micronucleus frequency = 0.1

1.8 ± 0.2

1.85 ± 0.2

Normalized apoptosis frequency = 0.05

1.65 ± 0.15

1.7 ± 0.15

1.75 ± 0.2

Especially in pimonidazole unlabeled cell fraction

1.5 ± 0.1

1.55 ± 0.1

1.6 ± 0.15