Preclinical evaluation of molecular-targeted anticancer agents for radiotherapy.

The combination of molecular-targeted agents with irradiation is a highly promising avenue for cancer research and patient care. Molecular-targeted agents are in themselves not curative in solid tumours, whereas radiotherapy is highly efficient in eradicating tumour stem cells. Recurrences after high-dose radiotherapy are caused by only one or few surviving tumour stem cells.

Effects of single-dose irradiation on bronchial epithelium: a comparison of BEAS 2B cell monolayers, human organ cultures, and Goettinger minipigs.

To assess the effects of radiation on bronchial epithelium, BEAS 2B cells cultured as monolayers and human bronchial epithelium cultured as organ cultures were exposed to single doses of 0, 10 and 30 Gy. The lactate dehydrogenase in the supernatant of the BEAS 2B cells increased markedly 24 h after irradiation, whereas in the organ cultures only a minor increase was found after 48 h. The nucleosomes in the supernatant of the BEAS 2B cells showed a massive increase in response to irradiation, whereas in the organ cultures no change could be seen.

Tumour stem cells--the evidence and the ambiguity.

Progressive growth of malignant tumours, metastatic spread and local recurrence after treatment can only be explained by the presence of cells with unlimited proliferative ability. While this is generally accepted, the proportion of such cells and their organization in a hierarchical system of stem cells and non-stem cell progeny is still a matter of controversy. Results of quantitative transplantation and dose requirement of curative radiotherapy have indicated low stem cell fractions in human and early passage rodent tumours, but uncertainty is introduced by uncontrollable experimental or biological factors and the probabilistic nature of stem cell performance itself Studies using a particular mouse carcinoma (AT17) have given direct insight into the number and clonal expansion of stem cells in situ, strongly supporting the hierarchical concept.

The influence of autologous tumor fibroblasts on the radiosensitivity of squamous cell carcinoma megacolonies.

Purpose: To study the influence of tumor fibroblasts on radiosensitivity and stem cell fraction of tumor cells in squamous cell carcinoma megacolonies by determining colony cure and clonogen survival.

Methods And Materials: Murine squamous cell carcinoma cells (AT478c) grown as flat but multilayered megacolonies were co-cultured with pre-irradiated tumor fibroblasts derived from the same carcinoma, and irradiated with 1, 2, 4, or 8 fractions. Recurrent clones and their growth pattern in situ were recorded.

Regrowth delay analysis of irradiated tumors in the curative dose region.

Purpose: To develop a method to analyze regrowth delay times, including cured tumors.

Methods And Materials: Regrowth delay measured in the in vitro squamous cell carcinoma megacolony system following fractionated irradiation was analyzed using two different approaches. A conventional regrowth delay analysis based on means or medians of dose groups was contrasted with a one-step procedure using the inverse of individual regrowth delay times, where cured tumors are represented by an infinite delay time.

Radiation-induced impairment of bone healing in the rat femur: effects of radiation dose, sequence and interval between surgery and irradiation.

Background And Purpose: Impairment of osseous healing in treatment combining surgery and radiotherapy is a frequent complication. Its dependence on sequence and interval was studied in a defined experimental model.

Materials And Methods: The effect of pre- and postoperative irradiation by single doses of X-rays on osseous closure of a 1.

The radiosensitivity of recurrent clones of an irradiated murine squamous cell carcinoma in the in vitro megacolony system.

Purpose: To measure changes in spontaneous growth rate and radiation response in the progeny of irradiated squamous cell carcinoma cells.

Materials And Methods: Murine SCC cells of the line AT478 were grown as epithelial megacolonies in vitro, using both the original line and two subsequent passages derived from a clone that had recurred after a high radiation dose. Radiosensitivity was evaluated in terms of local control following single dose irradiation of standard size megacolonies (0.

[Combined intraoperative and external irradiation of the celiac artery in the rabbit: the effects on the blood flow of the gastric mucosa].

Aim: To demonstrate changes in gastric mucosal blood flow caused by intraoperative radiotherapy of the celiac artery combined with external radiotherapy of the upper abdomen in a rabbit model. The study was designed to identify a possible correlation between a radiation-induced reduction in mucosal blood flow and the induction of gastric ulcer.

Material And Method: Intraoperative radiation doses of 0 or 30 Gy were given to the celiac artery in rabbits.

Complications of combined intraoperative radiation (IORT) and external radiation (ERT) of the upper abdomen: an experimental model.

An experimental model in the rabbit is presented which is suitable for analysis of clinically relevant, early side-effects of combined upper abdominal IORT and ERT. Fractionated ERT alone given through an upper abdominal a.-p.

The proliferative capacity of mouse fibrosarcoma cells that survived x-irradiation.

Delayed reproductive death, the appearance of colonies with a reduced cell density (impaired colonies) and the number of giant cells per colony were investigated in murine fibrosarcoma cells after irradiation with 3 to 9 Gy of x-rays. Radiation survivors were replated after reaching confluence, which occurred after 13 to 15 doublings; this procedure was repeated three times. The replating efficiency decreased in a dose-dependent manner, the survivors of 9 Gy achieving only 30% of the plating efficiency of unirradiated cells.

Effects of stimulated repopulation on oral mucositis during conventional radiotherapy.

The effect of local conditioning of human oral mucosa by silver nitrate solution (3%) on epithelial proliferation rates was tested in 11 healthy volunteers by in vitro labelling of biopsies with tritiated thymidine. Compared to control biopsies from 13 volunteers, stimulation over 3 days, 3 times per day, yielded a significant (p = 0.006) increase in the epithelial labelling index (LI) from 4.

Radiation-induced impairment of osseous healing: quantitative studies using a standard drilling defect in rat femur.

The femora of adult Wistar rats were locally irradiated with single doses of X rays and 1 day later were wounded by a standardized drilling defect that extended through the diaphyseal cortex into the marrow cavity. Healing of the lesion was followed over 30 weeks to assess the time course of osseous closure. In unirradiated bones healing was complete by week 7.

Quantitative distinction of cisplatin-sensitive and -resistant mouse fibrosarcoma cells grown in multicell tumor spheroids.

As a suitable model to study the growth behavior and therapeutic response of drug-resistant and -sensitive cells in three-dimensional coculture we have established multicellular spheroids generated from both cisplatin-sensitive and -resistant cells of a murine fibrosarcoma cell line. A drug resistant clone was derived from the parent cisplatin-sensitive cells by intermittent drug exposure in vitro. As a prerequisite for analysis of differential growth and treatment response of spheroid subpopulations, two efficient methods to discriminate between the two morphologically indistinguishable subpopulations in mixed spheroids were established.

Proliferation equivalent of 'accelerated repopulation' in mouse oral mucosa.

The proliferation response and changes in cellularity of mouse tongue epithelium were studied after single doses of X-rays and during 3 weeks of daily irradiation. A single dose of 13 Gy resulted in minimum cellularity (70% of control values) on days 3-5 and complete restoration on day 7. Mitotic activity ceased for 1 day followed by normal-to-supranormal values until day 15.

Cell kinetic analysis of murine squamous cell carcinomas: a comparison of single versus double labelling using flow cytometry and immunohistochemistry.

The study was originally set up to measure accurate cell kinetic parameters in two murine squamous cell carcinomas (scc) for comparison with radiobiological data on proliferation during radiotherapy. The tumours, AT84 and AT478, were both moderately well differentiated aneuploid scc. In the course of the study, several comparisons of techniques were made in two different centres.

Capacity and kinetics of SLD repair in mouse tongue epithelium.

The effect of dose fractionation on the radiation response of mouse tongue epithelium was quantified in fractionation protocols involving 1, 3, 4, 5 and 10 fractions, separated by at least 4 h. Fractionated irradiation was given either to the whole snout by 300 kV X-rays or locally to the tongue using 25 kV X-rays. Each protocol was terminated by a final local top-up dose (25 kV X-rays) of 5 Gy.

Increased radiation tolerance of mouse tongue epithelium after local conditioning.

The effect of local stimulation on mitotic activity and radiation tolerance was studied in mouse tongue mucosa. Silver nitrate solution (0.5-20%) was used for local conditioning.

Rapid repopulation in radiotherapy: a debate on mechanism. Accelerated repopulation in tumours and normal tissues.

Accelerated repopulation is a well established response pattern of normal epithelial to fractionated irradiation. It is delayed until the tissue recognises functional injury. It is well regulated to maintain a steady state and continues until integrity of the tissue is restored.

Acute mucositis in the stimulated oral mucosa of patients during radiotherapy for head and neck cancer.

In 16 patients treated for squamous cell carcinoma of the oral cavity or oropharynx with an accelerated split course regimen, acute mucosal reactions were significantly less in the left buccal mucosa which had been repeatedly painted with 2% silver-nitrate solution for several days before radiotherapy than in the unpainted right buccal mucosa.