Cystatin D has tumor suppresor activity and is regulated by1 , 25-dihydroxyvtamin D3 in colon cancer

• Autores: Silvia Álvarez Díaz
• Directores de la Tesis: Alberto Muñoz (dir. tes.)
• Lectura: En la Universidad Autónoma de Madrid ( España ) en 2009
• Idioma: inglés
• Tribunal Calificador de la Tesis: Juan Bernal Carrasco (presid.), Amparo Cano (secret.), Eva Hernando Monge (voc.), Miguel Quintanilla Avila (voc.), Roberto Erwin Knecht (voc.)
• Materias:
  • Química
    • Bioquímica
      • Vitaminas
  • Ciencias de la vida
    • Biología celular
    • Biología molecular
  • Ciencias médicas
    • Patología
      • Oncología
• Enlaces
  • Tesis en acceso abierto en: Biblos-e Archivo
• Resumen

  • Colorectal cancer (CRC) is one of the most common human neoplasias. Epidemiological and preclinical studies have shown that 1¿,25-dihydroxyvitamin D3 (1¿,25(OH)2D3), the most active metabolite of vitamin D3, has wide but not fully understood antitumor activity. Most, if not all, 1¿,25(OH)2D3 actions are mediated by vitamin D receptor (VDR), a member of the nuclear receptor superfamily of transcription factors whose expression is lost during CRC progression. Cystatin D (CST5 gene product) is an inhibitor of several cysteine proteases of the cathepsin family. Cystatin D has a more restricted pattern of tissue expression and narrower inhibitory profile than other members of the cystatin family, as well as an unknown biology. A previous transcriptomic analysis of 1¿,25(OH)2D3 action on human colon cancer cells revealed CST5 as a candidate target gene.

    The results described in this Thesis show that 1¿,25(OH)2D3 increases CST5 RNA and protein levels in human CRC cells. Consistently, diminished cathepsin L activity was detected in 1¿,25(OH)2D3-treated cells. 1¿,25(OH)2D3 promotes VDR binding to, and transcriptional activation of, the CST5 promoter. In cells lacking endogenous cystatin D, ectopic cystatin D expression inhibited cell proliferation, migration and anchorageindependent growth. Moreover, cystatin D antagonized the Wnt/ß-catenin signaling pathway and repressed c-MYC expression. Additionally, cystatin D repressed the epithelialmesenchymal transition inducers SNAI1, SNAI2, ZEB1 and ZEB2, and, conversely, induced E-cadherin and other adhesion proteins. Transcriptomic analyses have identified a panel of candidate target genes whose RNA levels in CRC cells are modulated by cystatin D. Furthermore, ectopic cystatin D expression blunted xenograft tumor growth in immunodeficient mice. CST5 knockdown using shRNA abrogated the antiproliferative effect of 1¿,25(OH)2D3, attenuated E-cadherin expression, and increased c-MYC expression. Interestingly, mutant cystatin D proteins with reduced antiproteolytic activity preserve the antiproliferative but not the cell migration-inhibitory effects. In human CRC tumors, we found a strong correlation between the expression of VDR and E-cadherin and that of cystatin D. Additionally, the loss of cystatin D correlated with poor tumor differentiation. Our results show that CST5 acts as a tumor suppressor gene with unpredicted effects that may contribute to the antitumoral action of 1¿,25(OH)2D3 in colon cancer.