Impact of preirradiation of the tumour bed on cell production rate and cell loss of human FaDu squamous cell carcinoma growing in nude mice.
OBJECTIVE
To explore whether the tumour bed effect (TBE) in FaDu squamous cell carcinoma growing in nude mice is caused by a reduced tumour cell production rate and/or by increased tumour cell loss.


METHODS
Human FaDu tumours were studied in NMRI nude mice. The volume doubling time (VDT) between 100 and 400 mm3 was determined for tumours in unirradiated subcutaneous (sc) tissues (group 1), tumours in sc tissues preirradiated with 12.5 Gy (group 2), tumours irradiated in situ with 12.5 Gy (group 3), and tumours from group 3 re-transplanted into unirradiated sc tissues (group 4). Labelling index (LI), potential doubling time (Tpot), relative necrotic area and apoptotic index (AI) were evaluated in tumours from groups 1 and 2.


RESULTS
The median VDT were 2.6 days (95% CI 2-4) in group 1 and 7.0 days (4-15) in group 2 (p<0.001). The VDT were not significantly different between groups 2 and 3, and group 1 and 4. In groups 1 and 2, the Tpot values (3.1 +/- 0.6 days (SD) versus 2.9 +/- 0.5 days) and the LI were identical (10 +/- 1.5%). The median relative necrotic area was significantly larger in group 2 (37% [23-42]) compared with group (6% [0.3-27]). The apoptotic index was low (0.2%) and did not differ between groups 1 and 2.


CONCLUSIONS
The results indicate that the TBE in FaDu squamous cell carcinoma is not caused by a reduced cell production rate in the viable tumour compartment. Rather, the TBE reflects a decreased viable tumour cell compartment due to increased cell loss. Necrosis appears to be the major component of the tumour bed induced cell loss in FaDu tumours, whereas apoptosis has no impact on the TBE in this model.
Petersen
C
C
Department of Radiation Oncology, Medical Faculty Carl Gustav Carus, Technical University of Dresden, Germany.
Eicheler
W
W
Baisch
H
H
Zips
D
D
Baumann
M
M
D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000473:pathology* / Q000532:radiotherapy*; D016923:Cell Death / Q000528:radiation effects; D002455:Cell Division / Q000528:radiation effects; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D009336:Necrosis; D009368:Neoplasm Transplantation; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured