Receptor tyrosine kinase inhibition suppresses growth of pediatric renal tumor cells in vitro

Purpose: Children who undergo standard therapy for renal tumors are at an increased risk for treatment sequelae such as congestive heart failure, abnormal trunk development, and secondary malignancies. Therefore, research on the use of novel chemotherapeutic agents with fewer side effects is justified. Recent experimental evidence suggests that growth factor receptors such as epidermal growth factor receptor (EGFR) and platelet-derived growth factor receptor (PDGFR) play an important role in growth and development of pediatric renal tumors especially that of Wilms' tumor. In this study we investigated the effects of genistein, AG1478, and AG1295, from the class of growth factor receptor tyrosine kinase (GFR-TK) inhibitors, on proliferation and colonigenic growth of 2 pediatric renal tumor cell lines. Methods: The authors studied the effect of genistein (broad-spectrum GFR-TK inhibitor), AG1478 (EGFR-specific GFR-TK inhibitor), and AG1295 (PDGFR-specific GFR-TK inhibitor) on proliferation and colonigenic growth of rhabdoid tumor of the kidney and Wilms' tumor cell lines: G-401 and SK-NEP-1, respectively. The effect of genistein at concentrations of 0 to 200 mu mol/L, and AG1478 and AG1295 at 0 to 10,000 eta mol/L were tested on proliferation by using a growth inhibition assay. Viable cell counts at each concentration were obtained by hemocytometer and trypan blue exclusion, and percent growth inhibition was calculated based on control cultures at the same time-point. As a measure of colonigenic survival, the percent inhibition of colony formation in drug-treated dishes was calculated based on the number of colonies (>50 cells) in control dishes. Results: Genistein at concentrations of 25 and 50 mu mol/L inhibited the colonigenic growth of G-401 by 37% and 79% (P = .01 and 5E-06, P-tailed t test, respectively) and that of SK-NEP-1 by 44% and 74% (P = .0001 and 9.9E-07). The mean percent growth inhibition at the above doses was 57% +/- 7.9% and 96% +/- 0.2% for G-401, and 47% +/- 11.2% and 60% +/- 2.7% for SK-NEP-1. AG1478 at concentrations of 1,000 and 5,000 eta mol/L inhibited the colonigenic growth of G401 by 75% and 78% (P = .0005 and 7.38E-06, respectively) and that of SK NEP-1 by 19% and 40% (P = .02 and .0001). The percent growth inhibition at the mentioned concentrations for G-401 were 53% +/- 9.3% and 63% +/- 6.30%, and for SK-NEP-1 were 55% +/- 14.5% and 65% +/- 20.1%, respectively. AG1295 did not appear to be as effective as AG1478. Conclusions: This is the first experimental study on the use of GFR-TK inhibitors as a potential treatment for pediatric renal tumors. GFR-TK inhibitors such as genistein occur naturally in soybean foods and have been shown to reach therapeutic levels in blood after consuming a soybean-based diet. Considering the significance of growth factor receptor activity in Wilms' tumor development, inhibition of GFR-TKs should be investigated as effective and potentially nontoxic adjunctive treatment for this childhood tumor. Furthermore, GFR-TK inhibitors may offer an effective alternative to the treatment of commonly fatal rhabdoid tumor of the kidney in children. Copyright (C) 2000 by W.B. Saunders Company.