Gigaxonin Suppresses Epithelial-to-Mesenchymal Transition of Human Cancer Through Downregulation of Snail.

Gigaxonin is an E3 ubiquitin ligase that plays a role in cytoskeletal stability. Its role in cancer is not yet clearly understood. Our previous studies of head and neck cancer had identified gigaxonin interacting with p16 for NFκB ubiquitination. To explore its role in cancer cell growth suppression, we analyzed normal and tumor DNA from cervical and head and neck cancers. There was a higher frequency of exon 8 SNP (c.1293 C>T, rs2608555) in the tumor (46% vs. 25% normal, P = 0.011) pointing to a relationship to cancer. Comparison of primary tumor with recurrence and metastasis did not reveal a statistical significance. Two cervical cancer cell lines, ME180 and HT3 harboring exon 8 SNP and showing T allele expression correlated with higher gigaxonin expression, reduced in vitro cell growth and enhanced cisplatin sensitivity in comparison with C allele expressing cancer cell lines. Loss of gigaxonin expression in ME180 cells through CRISPR-Cas9 or siRNA led to aggressive cancer cell growth including increased migration and Matrigel invasion. The in vitro cell growth phenotypes were reversed with re-expression of gigaxonin. Suppression of cell growth correlated with reduced Snail and increased e-cadherin expression. Mouse tail vein injection studies showed increased lung metastasis of cells with low gigaxonin expression and reduced metastasis with reexpression of gigaxonin. We have found an association between C allele expression and RNA instability and absence of multimeric protein formation. From our results, we conclude that gigaxonin expression is associated with suppression of epithelial-mesenchymal transition through inhibition of Snail. SIGNIFICANCE: Our results suggest that GAN gene exon 8 SNP T allele expression correlates with higher gigaxonin expression and suppression of aggressive cancer cell growth. There is downregulation of Snail and upregulation of e-cadherin through NFκB ubiquitination. We hypothesize that exon 8 T allele and gigaxonin expression could serve as diagnostic markers of suppression of aggressive growth of head and neck cancer.

A xenograft study of human adipose stromal cell-based vocal fold mucosal replacement in rabbits.

Objectives: Vocal fold (VF) scarring, manifested by increased collagen, decreased glycosaminoglycans (GAGs), and disrupted elastic fibers, remains a negative consequence of VF injury or resection. The objective of this study is to compare four reconstructive options after Vf mucosal resection in rabbits. A Cell-Based Outer Vocal fold Replacement (COVR) using human adipose-derived mesenchymal stromal cells (hASCs) in fibrin scaffold is directly compared with a decellularized scaffold implant, hASC injection, and resection alone without reconstruction. The primary hypothesis is that the cells-in-scaffold construct better reconstitutes the VF structure than either cells or scaffold alone, or than healing by secondary intention. Methods: A total of49 rabbits received bilateral VF cordectomy, followed by either COVR implant, decellularized scaffold implant, hASC injection, or no reconstruction (injured control group). Larynges were harvested after 6 weeks. Results: Histology demonstrated greater lamina propria thickness, less collagen deposition, and more GAGs in COVR animals versus all other treatment groups. Evidence of persistent human cells was found in about half of the cell-treated animals. RNA levels of fibrosis pathway and macrophage phenotype markers were statistically unchanged among treatment groups at 6 weeks. Conclusion: These data support the efficacy of COVR implantation in restoring VF microstructure in rabbits. The intact COVR was required; isolated components of decellularized scaffold or injected hASC still produced histologic scarring. We propose that the unique bilayered cell structure within fibrin enables controlled matrix remodeling to minimize wound contraction and fibrosis, and to promote GAG deposition. Level of Evidence: Basic science study.