Abstract 3482: Combination of temsirolimus, a mTOR targeting drug, with the association of EGFR-targeting drug cetuximab, VEGF-targeting drug bevacizumab, and irradiation: A pre-clinical study on head and neck tumour
Authors: Bozec Alexandre , Etienne-Grimaldi Marie-Christine , Fischel Jean-Louis , Sudaka Anne , Toussan Nicolas , Formento Patricia , Milano Gérard 
Published: February 2011

Background : Constitutive activation of AKT following PTEN inactivation is a well-known mechanism involved in tumor initiation and progression. Since mTOR is one of the main AKT-related messengers, mTOR inhibitors such as temsirolimus are promising anticancer drugs. Our group (Bozec A. Br J Cancer, 2007) previously reported, on head and neck tumour xenografts, that the tumour regression induced by the combination of radiotherapy (RT) with anti-EGFR and anti-angiogenic therapies was followed (after treatment arrest) by tumor re-growth. Importantly, this tumour re-growth was accompanied by a significant decrease in PTEN expression and an increase in phospho-AKT expression. The aim of this study was thus to add a mTOR targeting drug (temsirolimus) to a tri-therapy consisting of RT + anti-EGFR + anti-angiogenic drugs so as to prolong anti-tumor effects.

Methods : The human head and neck cancer cell line CAL33 (exhibiting high EGFR content and secreting VEGF-A) was xenografted in the flank of nude mice. Treatment (20 mice per treatment group) was administered for 2 weeks, starting 14 days after cell injection. It consists of either vehicule (control), temsirolimus (5 mg/kg i.p. 5 times a week), tri-therapy with RT (6 Gy 3 times a week) + cetuximab (0.5 mg/kg i.p. 5 times a week) + bevacizumab (5 mg/kg i.p. 5 times a week) or the temsirolimus-tri-therapy combination. Mice were sacrificed when tumor volumes reached 2500 mm3. Tumor volume and mice weight (estimation of global toxicity) were measured once a week.

Results : The time to reach a tumor volume of 2000 mm3 was significantly different between the 4 treatment groups (Log Rank p &lt; 0.0001), with a median of 29.5, 44.5, 67.0 and 70.0 days for control, temsirolimus, tri-therapy and combination groups, respectively. The combination of temsirolimus and the tri-therapy produced the longest growth-inhibiting effects (tri-therapy versus combination, p = 0.01). No significant interaction was observed between temsirolimus and combination treatments, suggesting that temsirolimus on one hand and RT-cetuximab-bevacizumab on the other hand, exert additive effects on tumor growth inhibition. No animal weight loss could be attributed to any of the tested treatments. IHC analyses of tumor vasculature, proliferation status (Ki67) and downstream signalling phospho-proteins (pAKT . . .) are ongoing.

Conclusion : These experimental results suggest that temsirolimus could represent a promising drug for testing in combination with irradiation, anti-EGFR and anti-angiogenic therapies in head and neck cancer patients.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3482.