Cell adhesion-mediated radioresistance (CAM-RR). Extracellular matrix-dependent improvement of cell survival in human tumor and normal cells in vitro.
BACKGROUND
Cell-extracellular matrix (ECM) contact is thought to have great impact on cellular mechanisms resulting in increased cell survival upon exposure to ionizing radiation. Several human tumor cell lines and normal human fibroblastic cell strains of different origin, all of them expressing the wide-spread and important integrin subunit beta1, were irradiated, and clonogenic cell survival, beta 1-integrin cell surface expression, and adhesive functionality were investigated.


METHODS
Human tumor cell lines A172 (glioblastoma), PATU8902 (pancreas carcinoma), SKMES1 (lung carcinoma), A549 (lung carcinoma), and IPC298 (melanoma) as well as normal human skin (HSF1) and lung fibroblasts (CCD32) and human keratinocytes (HaCaT) were irradiated with 0-8 Gy. Besides colony formation assays, beta 1-integrin cell surface expression by flow cytometry and adhesive functionality by adhesion assays were analyzed.


RESULTS
All cell lines showed improved clonogenic survival after irradiation in the presence of fibronectin as compared to plastic. Irradiated cells exhibited a significant, dose-dependent increase in beta 1-integrin cell surface expression following irradiation. As a parameter of the adhesive functionality of the beta 1-integrin, a radiation-dependent elevation of cell adhesion to fibronectin in comparison with adhesion to plastic was demonstrated.


CONCLUSIONS
The in vitro cellular radiosensitivity is highly influenced by fibronectin according to the phenomenon of cell adhesion-mediated radioresistance. Additionally, our emerging data question the results of former and current in vitro cytotoxicity studies performed in the absence of an ECM. These findings might also be important for the understanding of malignant transformation, anchorage-independent cell growth, optimization of radiotherapeutic regimes and the prevention of normal tissue side effects on the basis of experimental radiobiological data.
Institute of Radiology, Medical Academy of German Armed Forces, Munich, Germany. nils_cordes@web.de
Nils
N
Cordes
Viktor
V
Meineke
D000704:Analysis of Variance; D002448:Cell Adhesion / Q000528:radiation effects*; D002470:Cell Survival / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005109:Extracellular Matrix / Q000502:physiology*; D016326:Extracellular Matrix Proteins; D005347:Fibroblasts / Q000528:radiation effects; D005353:Fibronectins / Q000502:physiology; D005434:Flow Cytometry; D006801:Humans; D019012:Integrin beta1 / Q000502:physiology*; D015603:Keratinocytes / Q000528:radiation effects; D011829:Radiation Dosage; D011836:Radiation Tolerance; D011839:Radiation, Ionizing; D014407:Tumor Cells, Cultured / Q000528:radiation effects*
D016326:Extracellular Matrix Proteins; D005353:Fibronectins; D019012:Integrin beta1