A human ESCC tissue microarray (Catalog No. ES244) was purchased from US Biomax, Inc. (Rockville, MD) and DFMO (Catalog No. K100) was from AK Scientific, Inc. (Union City, CA). The primary antibodies against ODC (Catalog No. sc-390366), Bcl-2 (Catalog No. sc-7382), Bax (Catalog No. sc-7480), p21 (Catalog No. sc-6246), p27 (Catalog No. sc-1641), cyclin B1 (Catalog No. sc-245) and β-actin (Catalog No. sc-47778) were obtained from Santa Cruz Biotechnology (Santa Cruz, CA). The primary antibodies to detect cleaved PARP (Catalog No. 5625), phosphorylated ERKs (T202/Y204; Catalog No. 14474), E-cadherin (Catalog No. 3195), cleaved caspase 3 (Catalog No. 9661), p53 (Catalog No. 2524), phosphorylated CDK1 (Tyr15; Catalog No. 4539) were purchased from Cell Signaling Biotechnology (Beverly, MA) and the Ki-67 (Catalog No. MA5-14520) antibody was from Thermo Scientific (Fremont, CA). The shODC plasmids cloned into the lentiviral expression vector pLKO.1 were obtained from the University of Minnesota (Minneapolis, MN). Human shODC full hairpin sequence is #1. 5′-CCGGGCCATATGGAAGACTAGGATACTCGAGTATCCTAGTCTTCCATATGGCTTTTTG-3′; #2. 5′-CCGGGCCGACGATCTACTATGTGATCTCGAGATCACATAGTAGATCGTCGGCTTTTTG-3′; #3. 5′-CCGGCCTTGTAAACAAGTATCTCAACTCGAGTTGAGATACTTGTTTACAAGGTTTTTG-3′; #4. 5′-CCGGGCGTCTATGGATCATTTAATTCTCGAGAATTAAATGATCCATAGACGCTTTTTG-3′; #5. 5′-CCGGCCTCCAGAGAGGATTATCTATCTCGAGATAGATAATCCTCTCTGGAGGTTTTTG-3′.