Cell experiment:

Cancer cells are seeded in 96-well plates and are treated with different doses of Gefitinib (0.01-20 μM), Metformin or both for 72 hours. Cell proliferation is measured with the MTT assay. The IC50 values are determined by interpolation from the dose-response curves. Results represent the median of 3 separate experiments each conducted in quadruplicate. The results of the combined treatment are analyzed according to the method of Chou and Talalay by using the CalcuSyn software program[3].

Animal experiment:

Mice[3] Four- to 6-week old female balb/c athymic (nu+/nu+) mice are acclimatized for 1 week before being injected with cancer cells and injected subcutaneously with 107 H1299 and CALU-3 GEF-R cells that has been resuspended in 200 μL of Matrigel. When established tumors of approximately 75 mm3 in diameter are detected, mice are left untreated or treated with oral administrations of metformin (200 mg/mL metformin diluted in drinking water and present throughout the experiment), gefitinib (150 mg/kg daily orally by gavage), or both for the indicated time periods. Each treatment group consists of 10 mice. Tumor volume is measured using the formula π/6×larger diameter×(smaller diameter)2. Rats[4] The rats are randomly assigned to 1 of 4 experimental groups: 1) the unirradiated rats treated with oral administration of vehicle (0.1% Tween 80) once daily; 2) the unirradiated rats treated with oral administration of gefitinib (50 mg/kg/day) once daily; 3) the irradiated rats treated with oral administration of vehicle once daily; 4) the irradiated rats treated with oral administration of gefitinib once daily. Each experimental group comprised 5-6 rats and all treatments are delivered for 14 days.

The EGFR is a Mr 170,000 transmembrane glycoprotein with an external binding domain and an intracellular tyrosine kinase domain. Gefitinib (ZD-1839, Iressa) is an Epidermal Growth Factor Receptor-selective Tyrosine Kinase Inhibitor.

In vitro: Gefitinib inhibited colony formation in soft agar in a dose dependent manner in all cancer cell lines. However, treatment with higher doses resulted in a 2–4-fold increases in apoptosis. Dose-dependent supra-additive increase in growth inhibition was observed when cancer cells were treated with totoxic drugs and Gefitinib. The combined treatment markedly enhanced apoptotic cell death induced by single agent treatment [1].

In vivo: Gefitinib treatment of nude mice bearing established human GEO colon cancer xenografts revealed a reversible dose-dependent inhibition of tumor growth because GEO tumors resumed the growth rate of controls at the end of the treatment [1].

Clinical trial: Administration of a 250-mg dose of gefitinib as a dispersion preparation by drink or nasogastric tube achieved a systemic exposure to gefitinib that was consistent with that achieved when gefitinib was administered as a whole tablet. No evidence of tolerability problems associated with the routes of administration studied was observed in these healthy volunteers [2].

References:
[1] Ciardiello F, Caputo R, Bianco R, Damiano V, Pomatico G, De Placido S, Bianco AR, Tortora G.  Antitumor effect and potentiation of cytotoxic drugs activity in human cancer cells by ZD-1839 (Iressa), an epidermal growth factor receptor-selective tyrosine kinase inhibitor. Clin Cancer Res. 2000;6(5):2053-63.
[2] Cantarini MV, McFarquhar T, Smith RP, Bailey C, Marshall AL.  Relative bioavailability and safety profile of gefitinib administered as a tablet or as a dispersion preparation via drink or nasogastric tube: results of a randomized, open-label, three-period crossover study in healthy volunteers. Clin Ther. 2004;26(10):1630-6.