The Presence of Wild-Type TP53 Is Necessary for the Radioprotective Effect of the Bowman-Birk Proteinase Inhibitor in Normal Fibroblasts

Abstract

In the present study we have demonstrated that the Bowman-Birk proteinase inhibitor (BBI) protected normal fibroblasts from a radiation-induced reduction in cell survival, whereas in transformed fibroblasts no radioprotective effect was observed. It was shown that BBI reduced the radiation-induced protein stabilization and DNA-binding activity of TP53 (formerly known as p53) in normal fibroblasts. In transformed fibroblasts, BBI failed to induce these effects. The analysis of the TP53 gene in transformed fibroblasts revealed a mutation in exon 5. As a consequence of this mutation, the expression of the TP53 downstream gene CDKN1A (p21/WAF1/Cip1) is blocked. Based on experiments using TP53 antisense oligonucleotides, the radioprotective effect of BBI could be correlated with the function of wild-type TP53. Thus BBI can be considered as a selective radioprotective agent for normal human fibroblasts.

O-phospho-L-tyrosine protects TP53 wild-type cells against ionizing radiation

“…Comparable results were published for BBI [9]. For BBI a significant correlation between cellular radioprotection and TP53-genotype was observed [9]. A corresponding correlation was observed for P-Tyr (Table 1).…”

“…Moreover, for cell lines lacking the radioprotective effect mediated by P-Tyr, a radiosensitizing effect was observed. Comparable results were published for BBI [9]. For BBI a significant correlation between cellular radioprotection and TP53-genotype was observed [9].…”

“…The cell line HH4dd derived spontaneously from the normal cell strain HH4 and is characterized by a TP53 mutation [9], growth in soft agar, aneuploidy, and tumor induction in nude mice. Additionally, two human squamous carcinoma cell lines HTB-35 (ATCC, origin cervical cancer, passage unknown, used in passage 10 after receipt) and HTB-43 (ATCC, origin head and neck cancer, passage 124) were tested.…”

Bowman-Birk Inhibitors from Legumes: Utilisation in Disease Prevention and Therapy

“…In a cell line with inducible expression of mutated p53, the radioprotective effect of BBI was only detected when the expression of the mutated p53 was switched off [75]. The activation of the DNA-repair machinery, induced by pre-treatment of fibroblastic cells with soybean BBI, suggests a possible BBI-mediated p53-dependent mechanism for radioprotection [82,83]. Since a high number of tumors have lost p53 function during their development, the clinical application of BBI to protect normal tissue from radiation damage would effectively improve the therapeutic outcome of radiotherapy.…”

P53-dependent induction of serine proteases in irradiated mouse colon

“…47 Interestingly, for the Bowman-Birk proteinase inhibitor to have protective behavior after irradiation, p53 needs to be present. 48 Previous in vitro studies in intestinal epithelial cells (T84) have shown that chemoattractant-induced polymorphonuclear neutrophil (PMN) transmigration is associated with increased epithelial apoptosis. This apoptosis may be induced by the rearrangement of the epithelial actin cytoskeleton associated with PMN transmigration.…”