Normal Tissue and Tumors – Assays and Response to Radiation

Question 1

the only event in the cell cycle that can be identified with a light microscope

Answer 1

The condensation of chromosomes during M phase

Question 2

G0

Answer 2

cells stop progressing through the cell cycle

Question 3

G1 and G2

Answer 3

the gaps in activity,

Question 4

Radiation will cause primary cells to arrest in

Answer 4

both G1 and G2, while tumor cells would show only a G2 arrest point

Question 5

most sensitive cell types

Answer 5

that divide

Question 6

Cells are most sensitive during

Answer 6

G2 and M

Question 7

Cells in ____ phase are most resistant

Answer 7

S

Question 8

Mitotic Index (MI):

Answer 8

proportion of cells in mitosis

MI = TM(time for mitosis)/TC (total cycle time)

Question 9

Labeling Index (LI):

Answer 9

the proportion of cells in S phase

LI = TS (time for DNA synthesis)/TC(total cell cycle time)

Question 10

Labeling Index can be determined by

Answer 10

pulse labeling (10-30 min)cells
with DNA precursors (3H-thymidine or with BrdUrd), fixing, staining as appropriate and counting labeled cells.

Question 11

Cell cycle time frame

Answer 11

10h to 10 days

Question 12

G1 phase length

Answer 12

150 h

Question 13

S phase length

Answer 13

6-10 h

Question 14

G2 phase length

Answer 14

1-2 h

Question 15

M phase length

Answer 15

1h

Question 16

The “percent-labeled mitoses technique” entails:

Answer 16

the feeding of a population of cells in the S-phase and the subsequent observation of the stained cells in the M phase.

Question 17

Growth fraction

Answer 17

proliferating cells/total #cells = P/(Q+P) Q-quiescent cells

Question 18

Potential Doubling Time (Tpot)

Answer 18

the cell cycle time/fraction of cycling cells: Tpot = TC/GF=(TS/LI). Does not take into account cell loss

Question 19

Tumor growth

Answer 19

net result of cell growth and cell loss:• inadequate nutrition (necrosis, hypoxia, inability of vascular supply to keep up with growth)
• apoptosis
• immunological surveillance
• metastasis
• exfoliation

Question 20

Cell loss factor

Answer 20

φ=1–(Tpot/TD) or TD (tumor volme doubling time)= Tpot/(1-φ).
If TC = 22h, GF = 0.6, and φ = 0.9, the TD = 366 hrs
In experimental animal tumors, cell loss factors range from 0 to 90%.

Question 21

Three factors determine tumor growth

Answer 21

Cell cycle time of proliferating cells
• Growth fraction
• Cell loss fraction

Question 22

Metastases appear to grow

Answer 22

more rapidly than the primaries in the same individual.

Question 23

determine response to chemotherapy

Answer 23

GF, LI, cell loss factor

Question 24

tumors with high LI

Answer 24

cured by chemotherapy

Question 25

TCD50

Answer 25

Tumor Control Dose - dose to control 50% of tumor cells. Compare treated and untreated cells number

Question 26

Hewitt Dilution Assay

Answer 26

Withdraw a few tumor cells from donor mouse (lymphocytic leukemia). Irradiate withdrawn cells in vitro. Inject cells into target mouse

Question 27

LD50

Answer 27

mean lethal dose -dose required to kill 50% of the animals in a given time period,
e.g., 30 days, LD50/30

Question 28

Lung Colony Assay

Answer 28

Tumor irradiated in situ, then excised and made into single cell suspension. Injected into animal and in 18-21 days lung cancer

Question 29

In Vitro-In Vivo Assays

Answer 29

tumor extracted from mouse, suspension prepared and plate tumor cells-> produce clones. The fastest and cheapest and most accurate assay but assume that there is no difference whether the tumor in vivo or in vitro

Question 30

spheroids

Answer 30

3-D spheres formed by cells aggregated in soft agar or suspension. Show in vitro tumor model

Question 31

Three basic types Dose-response assays for normal tissues

Answer 31

direct clonogenic assay;
functional assay;
multi fraction experiments used to assemble dose-response relationship or α/β ratios

Question 32

Spleen Colony Assay

Answer 32

normal bone marrow cells, blood, and spleen transferred to the lethally irradiated animal. Check spleen colonies

Question 33

Human A-T cells

Answer 33

one of the most radiation-sensitive human cell lines.

Question 34

Multifraction Experiments

Answer 34

• log (S/nd) = 𝜶 + 𝜷d

Question 35

differences in G1,

Answer 35

the difference in cell cycle between fast- and slow growing cells

Question 36

Dose-response curves for functional endpoints, distinct from cell
survival, can be obtained for:

Answer 36

pig skin and rodent skin by measuring skin reactions
early and late response of the lung by measuring breathing rate
spinal cord by observing myelopathy