MKI67 and head and neck squamous cell carcinoma: In contrast to the knockdown of Ki67 full-length isoform with exon 7, stable overexpression of Ki67-F significantly promoted cell proliferation in both non-tumorigenic HEK 293 cells and HNSCC cell line SCC-9 compared with Ki67-Δ7 overexpression and vector control (Figure 4A–C), as well as colony formation in SCC-9 cells (Figure 4D,E).