Cytotoxic Influence of Khat (<i>Catha edulis (Vahl) Forssk. ex Endl)</i> on Oral Fibroblasts, Squamous Carcinoma Cells, and Expression of α Smooth Muscle Actin oleh Azeem Ul Yaqin Syed, Muhammad A. Ahmed, Eman I. AlSagob, Mansour Al-Askar, Abdulrahman M. AlMubarak, Rizwan Jouhar, Abdul R. Ahmed, Sameer A. Mokeem, Nada Aldahiyan, Fahim Vohra, Tariq Abduljabbar