Zn medication eliminates established ESCCs in ZD rats. (A) Study design. (B) Body weights, serum Zn, and testis Zn levels. (C) Tumor multiplicity (number of tumors/esophagus, mean ± SD) (two-tailed Welch t test, n = 8 to 20 rats/cohort); large tumor (size >2 mm) and ESCC incidence (%) (two-tailed Fisher’s exact test; n = 8 to 20 rats/cohort). (D) qPCR analysis of esophageal miR-31 and miR-21 in Zn-treated and Zn-untreated rat esophagus (rat snoRNA as normalizer, two-tailed Welch t test. Error bars represent SD; n = 8 rats per group). (E) Zn treatment induces upregulation of tumor suppressor target PDCD4 (miR-21) and STK40/EGLN3 (miR-31). Black arrowheads in H&E-stained section indicate the presence of apoptotic cells in esophageal epithelium; black arrowheads in near serial PDCD4-stained sections showing abundant/intense nuclear overexpression of PDCD4 in Zn-treated esophagus, compared with sporadic occurrence of apoptotic cells (H&E section) and PDCD4 nuclear expression in isolated/sporadic cells of a Zn-untreated rat (white arrowheads). Representative photos of Zn-treated (n = 21) vs. Zn-untreated (n = 10) esophagus showing H&E staining, IHC staining for STK40, & EGLN3 (brown, 3,3′-diaminobenzidine tetrahydrochloride, DAB) and PDCD4, & PCNA (red, 3-amino-9-ethylcarbazole substrate-chromogen, AEC).