Tesis doctoral de Silvia Alvarez Diaz
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/íY-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.
Datos académicos de la tesis doctoral «Cystatin d has tumor suppressor activity and is regulated by 1¿,25-dihydroxyvitamin d3 in colon cancer«
- Título de la tesis: Cystatin d has tumor suppressor activity and is regulated by 1¿,25-dihydroxyvitamin d3 in colon cancer
- Autor: Silvia Alvarez Diaz
- Universidad: Autónoma de Madrid
- Fecha de lectura de la tesis: 21/12/2009
Dirección y tribunal
- Director de la tesis
- Alberto Muñoz Terol
- Tribunal
- Presidente del tribunal: Juan Bernal carrasco
- roberto Erwin knecht (vocal)
- eva Hernando monge (vocal)
- Miguel Quintanilla avila (vocal)