الفهرس 
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Abstract
Head and neck squamous cell carcinoma is the most common epithelial malignancy arising in the upper aerodigestive tract. Angiogenesis is a physiological process of formation of new capillaries from pre-existing vessels. It plays a crucial role in survival of cancer cells, tumor growth and development of distant metastasis.
The intensity of angiogenesis was shown to increase in various human tumors, including HNSCC. VEGF is considered the key player that regulates the angiogenesis process pre¬dominantly.
Imatinib is a tyrosine kinase inhibitor that was first used for the treatment of CML. The use of Imatinib as an anti- angiogenic drug was widely supported by many researches. It proved to be an effective agent in inhibiting VEGF in many types of cancer cell lines including HNSCC cell lines.
EGCG is the most abundant green tea catechin that represents approximately 59% of the total catechins. Studies conducted on cell-culture systems, animal models as well as human studies showed that EGCG in green tea could protect against a variety of cancer types. It is a potent VEGF inhibitor in many types of cancer. It was also reported that EGCG has low toxicity to normal tissues.
The aim of the present study was to evaluate the antiangiogenic effect of Imatinib and Epigallocatechin-3-gallate, used separately or in combination, on VEGF expression in Hep2 cell line.
The IC50 dose was calculated for imatinib and EGCG on Hep-2 cell line. The doses used in the study were the IC50 dose, one higher dose for each drug and two combination doses.
A. Cell culture and Drug treatment
• Hep-2 cell line was cultured and then incubated with different concentrations of Imatinib, Epigallocatechin-3-gallate and their combination, for two different durations 24 and 48hours, in addition to an untreated control group for the same durations.
B. Groups of the Study
The groups of the study were divided into a control group in 24 hours (G1T1) and 48 hours (G1T2). Imatinib treated group which was divided into two doses for 24 hours (I1T1 and I2T1) and two doses for 48 hours (I1T2 and I2T2). Two EGCG treated subgroups for 24 hours (EGCG1T1 and EGCG2T1) and two for 48 hours (EGCG1T2 and EGCG2T2). In addition to two subgroups treated with a combination of Imatinib and EGCG for 24 hours (C1T1 and C2T1) and two for 48 hours (C1T2 and C2T2).
RT- PCR was performed to measure the quantity of VEGF RNA and western blot analysis was performed to detect the expression of VEGF protein in different subgroups in addition to MTT assay.
Our results revealed a statistically significant reduction in the mean VEGF gene and protein expressions from G1T1 to I1T1 and I2T1 and from G1T2 to I1T2 and I2T2 in Imatinib and EGCG. I1T1 had less mean VEGF gene and protein expressions than EGCG1T1 with a statistically significant difference between both groups. In addition, I1T1showed a statistically significant reduction in mean VEGF expression than EGCG2T1 at the protein level only.
Moreover, I2T1 revealed a statistically significant reduction in mean of VEGF gene and protein expressions than EGCG1T1 and EGCG2T1. Furthermore, I1T2 showed a statistically significant decrease in the mean VEGF expression when compared to EGCG1T2 at gene and protein levels. On the other hand, I2T2 had a statistically significant reduction in the mean gene and protein expressions than EGCG1T2 and had a statistically significant reduction than EGCG2T2 at the gene level only.
Furthermore, a synergistic effect could be detected when combining both drugs, Imatinib and EGCG. The mean viability and VEGF gene and protein expressions in the combination groups were less than that in each drug individually. C2T2 was considered the most effective in all subgroups with the least mean viability, VEGF gene and protein expressions (0.06, 0.16 and 0.25 respectively).
Based on the results of the present study, it was concluded that Imatinib and EGCG could both effectively inhibit VEGF expression at gene and protein levels at 24 and 48 hours. Imatinib was more effective than EGCG in inhibiting VEGF gene and protein expressions at the two doses and in both durations. Imatinib and EGCG combination subgroups had synergistic effect in reducing VEGF gene and protein expressions.