*4.2. Chemicals and Other Reagents*

Human epidermoid carcinoma cell lines A431 and human NSCLC cell lines A549 were purchased from the Cell Bank of the Chinese Academy of Sciences (Shanghai, China). Cells were maintained in 60 mm cell culture dishes and cultured using DMEM supplemented with 10% FBS, 100 units/mL penicillin, 100 μg/mL streptomycin, and 2 mM l-glutamate at 37 ◦C in a 5% CO2 atmosphere with 95% humidity.

#### *4.3. MTT Assay for In Vitro Anti-Proliferative Activity*

The e ffect of compounds on cell proliferation was determined using the MTT assay, which is one of the most versatile and popular assays to assess the rate of cell proliferation caused by drugs and cytotoxic agents [53]. The assays were performed as previously described [52,54,55].
