TGF-β1-dependent induction and nuclear translocation of FHL2 promotes keratin expression in pilomatricoma

Virchows Arch. 2015 Feb;466(2):199-208. doi: 10.1007/s00428-014-1692-5. Epub 2014 Dec 5.

Abstract

Pilomatricoma is a tumour derived from hair matrix cells, which shows progressive keratin expression. Tumorigenesis is frequently associated with activating mutations in β-catenin gene inducing nuclear expression of β-catenin protein. The present study analysed the role of transforming growth factor-β1 (TGF-β1) and four-and-a-half LIM domain protein 2 (FHL2) in pilomatricoma in synopsis with their expression patterns in human anagen hair. Human anagen hair showed TGF-β1 and nuclear FHL2 expression in the outer root sheath layer separated from nuclear β-catenin staining, which was observed in cells of matrix and inner root sheath layers. Correspondingly, 41 out of 50 pilomatricomas showed co-labelling of TGF-β1 and nuclear FHL2 in tumour cells, which mostly lacked nuclear β-catenin expression. Tumoural proliferation (ki67) was associated with nuclear β-catenin staining but not with expression of nuclear FHL2. In early pilomatricomas, TGF-β1 expression was observed in few peripheral tumour cells showing absent or faint nuclear FHL2 co-staining. TGF-β1 expression extended in growing tumours going along with strong nuclear FHL2 co-labelling as well as progressive keratin 14 and keratin 1 expression. In vitro, cultured human keratinocytes showed weak to marked autocrine TGF-β1 expression; in case of enhanced TGF-β1 expression associated with keratin 10 staining. TGF-β1-treatment of cultured human keratinocytes induced nuclear and cytoplasmatic FHL2 staining as well as keratin 14 staining. Accordingly, siRNA-mediated FHL2 knockdown of TGF-β1-stimulated keratinocytes reduced keratin 14 staining. In conclusion, tumoural TGF-β1 secretion seems to induce nuclear translocation of co-factor FHL2 mediating progressive keratin expression in pilomatricoma.

MeSH terms

  • Active Transport, Cell Nucleus / physiology
  • Adolescent
  • Adult
  • Aged
  • Child
  • Child, Preschool
  • Female
  • Hair Diseases / metabolism*
  • Hair Diseases / pathology
  • Humans
  • Immunohistochemistry
  • Infant
  • Infant, Newborn
  • Keratins / biosynthesis*
  • LIM-Homeodomain Proteins / metabolism*
  • Male
  • Middle Aged
  • Muscle Proteins / metabolism*
  • Pilomatrixoma / metabolism*
  • Pilomatrixoma / pathology
  • Skin Neoplasms / metabolism*
  • Skin Neoplasms / pathology
  • Transcription Factors / metabolism*
  • Transforming Growth Factor beta1 / metabolism
  • Young Adult

Substances

  • FHL2 protein, human
  • LIM-Homeodomain Proteins
  • Muscle Proteins
  • Transcription Factors
  • Transforming Growth Factor beta1
  • Keratins