Antitumor effect in medulloblastoma cells by gefitinib: Ectopic HER2 overexpression enhances gefitinib effects in vivo

¹ Department of Pediatric Oncology, Catholic University, Largo A. Gemelli, 8, 00168 Rome, Italy
² Department of Pediatric Oncology, Catholic University, Rome, Italy
³ Department of Obstetrics and Gynecology, Catholic University, Rome, Italy
⁴ Department of Pathology, Catholic University, Rome, Italy
⁵ Department of Experimental Medicine, University La Sapienza, Rome, Italy; I.R.C.C.S. Neuromed, Pozzilli, Italy

^* To whom correspondence should be addressed. E-mail: tservidei{at}rm.unicatt.it.

	Abstract

The effects of the epidermal growth factor receptor (EGFR) inhibitor gefitinib on cell growth and signaling were evaluated in 3 medulloblastoma (MB) cell lines (D283, D341, Daoy), one supratentorial PNET cell line (PFSK) and 4 MB primary cultures. Cell lines showed diverse expression of EGFR and HER2, with high levels of constitutively activated HER2 in the HER2-overexpressing D341 and D283 cells. Gefitinib sensitivity varied across lines, being related neither with the expression of HER receptors, nor with receptor baseline activation. Gefitinib determined a G₀/G₁ arrest in all lines, whereas apoptosis was dose-dependently induced only in D283 and D341 cells. The molecular response to gefitinib was investigated in Daoy and D341 lines, which showed a higher (IC₅₀ 3.8 µM) and lower (IC₅₀ 6.6 µM) sensitivity to the agent, respectively. Gefitinib inhibited constitutive and EGF-triggered EGFR phosphorylation in both lines, whereas was ineffective on constitutive activation of HER2 in D341 cells. pAkt inhibition paralleled that of pEGFR, suggesting the presence of an autocrine gefitinib-sensitive EGFR/Akt pathway. On the whole, the EGF-dependent signaling was less responsive to ligand stimulation and gefitinib inhibition in D341 cells, that correlated with the lower sensitivity to gefitinib antiproliferative effect of this line. In vivo, the growth of D341 and Daoy xenografts was inhibited at 150 mg/Kg/day gefitinib by approximately 50%. Ectopically overexpressed HER2 in Daoy cells significantly increased sensitivity to gefitinib antitumor effects in vivo (TVI = 78%). Our data indicate that gefitinib might be a molecularly targeted agent for the treatment of MB.

Key Words: medulloblastoma, gefitinib, in vivo, EGFR, HER2

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