- Email: [email protected]
Antitumoral effects of metformin on cancer stem cells
296 Déclaration d’intérêts d’intérêts.
SFE Angers 2015 / Annales d’Endocrinologie (2015) 295–296 L’auteur n’a pas transmis de déclaration de conflits
http://dx.doi.org/10.1016/j.ando.2015.07.019 PL-005
Génétique de la maladie de Cushing M. Reincke (Pr) Klinikum der Ludwig-Maximilians-Universität München, Medizinische Klinik IV, Munich, Germany E-mail address: [email protected] Cushing’s disease is caused by corticotroph adenomas of the pituitary. To explore molecular mechanisms of endocrine autonomy, we recently performed exome sequencing of 10 corticotroph adenomas [1] identifying somatic mutations in the USP8 deubiquitinase gene in 4 of 10 adenomas. The mutations clustered in the 14-3-3 protein-binding motif enhancing proteolytic cleavage and catalytic activity of USP8. Cleaved USP8 led to increased EGF receptor deubiquitination impairing its downregulation and sustaining EGF signaling. USP8 mutants enhanced promoter activity of the gene for proopiomelanocortin. Our data show that dominant mutations in USP8 cause Cushing’s disease via activation of EGF receptor signaling. In a follow-up study, we performed a retrospective, multicentric, genetic analysis of 134 functioning and 11 silent corticotroph pituitary adenomas using Sanger sequencing. Clinical data from these patients have been collected and examined within the context of the mutational status of USP8. New mutations were characterized by functional studies. Somatic mutations in USP8 were found in 48 (36%) adenomas from patients with Cushing’s disease, but in none of the 11 silent corticotropinomas. The prevalence was higher in adults than in pediatric cases and in females than in males. Adults having USP8mutated adenomas were diagnosed at an earlier age (36 vs. 44 years) than those with wild-type adenomas. Future research will be directed towards therapeutic targeting of USP8 in corticotroph adenomas. Disclosure of interest The author has not supplied his declaration of conflict of interest. Reference [1] Reincke M, et al. Mutations in the deubiquitinase gene USP8 cause Cushing’s disease. Nat Genet 2015;47(1):31–8 [doi:10.1038/ng.3166. Epub 2014 Dec 8]. http://dx.doi.org/10.1016/j.ando.2015.07.020
PL-006
Antitumoral effects of metformin on cancer stem cells T. Florio (Pr) University of Genova, Genova, Italy E-mail address: [email protected] Epidemiological and preclinical studies suggested that metformin, the first-line drug for type-2 diabetes, exerts direct antitumoral activity. Clinical trials are currently ongoing for several human tumors, although the molecular mechanisms of metformin antiproliferative activity are still not completely identified. Several studies reported the involvement of AMP-activated kinase-dependent pathway, and the downstream effectors (e.g., mTOR) in metformin metabolic activity. Nevertheless, contrasting evidence was obtained on the involvement of this pathway in metformin antitumor effect, and several reports showed AMPKindependent antiproliferative activity. According to the hierarchical theory of tumorigenesis, cancer stem cells (CSC) are considered the real pharmacological target to obtain cancer remission. Here, we show that metformin inhibits proliferation of human glioblastoma cells, selectively acting on CSC viability, through the direct inhibition of chloride intracellular channel-1 (CLIC1). CLIC1 chloride current is specifically induced upon translocation and transient membrane insertion of this channel during cell cycle progression. By means of patch clamp experiments, we show that the antiproliferative effect of metformin correlates with the inhibition of CLIC1 current, causing the arrest of the G1-S transition. Furthermore, point mutation of the putative CLIC1 pore region impairs metformin interaction with the channel, highlighting an inhibitory activity from the extracellular side. This effect is rather specific for CSC, since no cytotoxic effects, using metformin at the same concentration, were observed in human normal stem cells. These findings highlight the role of CLIC1 as a principal target of metformin’s antiproliferative activity in human CSCs, paving the way for novel and needed pharmacological approach for cancer treatment. Disclosure of interest The author has not supplied his declaration of conflict of interest. http://dx.doi.org/10.1016/j.ando.2015.07.021
SFE Angers 2015 / Annales d’Endocrinologie (2015) 295–296 L’auteur n’a pas transmis de déclaration de conflits
http://dx.doi.org/10.1016/j.ando.2015.07.019 PL-005
Génétique de la maladie de Cushing M. Reincke (Pr) Klinikum der Ludwig-Maximilians-Universität München, Medizinische Klinik IV, Munich, Germany E-mail address: [email protected] Cushing’s disease is caused by corticotroph adenomas of the pituitary. To explore molecular mechanisms of endocrine autonomy, we recently performed exome sequencing of 10 corticotroph adenomas [1] identifying somatic mutations in the USP8 deubiquitinase gene in 4 of 10 adenomas. The mutations clustered in the 14-3-3 protein-binding motif enhancing proteolytic cleavage and catalytic activity of USP8. Cleaved USP8 led to increased EGF receptor deubiquitination impairing its downregulation and sustaining EGF signaling. USP8 mutants enhanced promoter activity of the gene for proopiomelanocortin. Our data show that dominant mutations in USP8 cause Cushing’s disease via activation of EGF receptor signaling. In a follow-up study, we performed a retrospective, multicentric, genetic analysis of 134 functioning and 11 silent corticotroph pituitary adenomas using Sanger sequencing. Clinical data from these patients have been collected and examined within the context of the mutational status of USP8. New mutations were characterized by functional studies. Somatic mutations in USP8 were found in 48 (36%) adenomas from patients with Cushing’s disease, but in none of the 11 silent corticotropinomas. The prevalence was higher in adults than in pediatric cases and in females than in males. Adults having USP8mutated adenomas were diagnosed at an earlier age (36 vs. 44 years) than those with wild-type adenomas. Future research will be directed towards therapeutic targeting of USP8 in corticotroph adenomas. Disclosure of interest The author has not supplied his declaration of conflict of interest. Reference [1] Reincke M, et al. Mutations in the deubiquitinase gene USP8 cause Cushing’s disease. Nat Genet 2015;47(1):31–8 [doi:10.1038/ng.3166. Epub 2014 Dec 8]. http://dx.doi.org/10.1016/j.ando.2015.07.020
PL-006
Antitumoral effects of metformin on cancer stem cells T. Florio (Pr) University of Genova, Genova, Italy E-mail address: [email protected] Epidemiological and preclinical studies suggested that metformin, the first-line drug for type-2 diabetes, exerts direct antitumoral activity. Clinical trials are currently ongoing for several human tumors, although the molecular mechanisms of metformin antiproliferative activity are still not completely identified. Several studies reported the involvement of AMP-activated kinase-dependent pathway, and the downstream effectors (e.g., mTOR) in metformin metabolic activity. Nevertheless, contrasting evidence was obtained on the involvement of this pathway in metformin antitumor effect, and several reports showed AMPKindependent antiproliferative activity. According to the hierarchical theory of tumorigenesis, cancer stem cells (CSC) are considered the real pharmacological target to obtain cancer remission. Here, we show that metformin inhibits proliferation of human glioblastoma cells, selectively acting on CSC viability, through the direct inhibition of chloride intracellular channel-1 (CLIC1). CLIC1 chloride current is specifically induced upon translocation and transient membrane insertion of this channel during cell cycle progression. By means of patch clamp experiments, we show that the antiproliferative effect of metformin correlates with the inhibition of CLIC1 current, causing the arrest of the G1-S transition. Furthermore, point mutation of the putative CLIC1 pore region impairs metformin interaction with the channel, highlighting an inhibitory activity from the extracellular side. This effect is rather specific for CSC, since no cytotoxic effects, using metformin at the same concentration, were observed in human normal stem cells. These findings highlight the role of CLIC1 as a principal target of metformin’s antiproliferative activity in human CSCs, paving the way for novel and needed pharmacological approach for cancer treatment. Disclosure of interest The author has not supplied his declaration of conflict of interest. http://dx.doi.org/10.1016/j.ando.2015.07.021