ABSTRACT
PURPOSE: Phosphoinositide-dependent kinase 1 (PDK1) is highly expressed in many solid tumors. And several studies have demonstrated that PDK1 has been an emerging and promising target for anti-cancer therapies. However, the role of PDK1 has not been studied so far in malignant pheochromocytoma (PCC). METHODS: In this study, immunohistochemical staining was performed to investigate the protein level of PDK1 in 63 PCC tissue samples, of which 49 were benign and 14 were malignant. In addition, we evaluated the effect of inhibition of PDK1 with siRNA on cell growth, apoptosis and invasive capacity in PC12 cells and identified the underlying mechanisms. RESULTS: We found that PDK1 was overexpressed in malignant PCC tissues, and knockdown of PDK1 with siRNA significantly inhibited cell proliferation, increased apoptosis induction, and attenuated cell migration and invasive capacity in PC12 cells. We also showed that knockdown of PDK1 significantly reduced the phosphorylation of Akt at threonine 308 (p-Akt T308) but did not alter the serine phosphorylation of Akt on the S473 site (p-Akt S473). Furthermore, we found that the p-Akt expression was noticeably decreased after knockdown of PDK1, but the t-Akt expression did not show a significant decrease. CONCLUSION: We have demonstrated for the first time that PDK1 is overexpressed in human malignant PCC and plays an important role in the malignant biological behaviors of PC12 cell. Specifically, we have revealed that knockdown of PDK1 could attenuate activation of the Akt signaling. These data suggest that PDK1 could be a new promising potential therapeutic target in human cancer treatment for malignant PCC.
Subject(s)
3-Phosphoinositide-Dependent Protein Kinases/analysis , Adrenal Gland Neoplasms/enzymology , Neoplasm Proteins/analysis , Pheochromocytoma/enzymology , Adrenal Glands/chemistry , Apoptosis , Cell Line, Tumor , Cell Movement , Gene Knockdown Techniques , Humans , RNA, Small Interfering , TransfectionABSTRACT
BACKGROUND: We have previously described a p.G533C substitution in the rearranged during transfection (RET) oncogene in a large family with medullary thyroid carcinoma. Here, we explore the functional transforming potential of RET p.G533C mutation. METHODS: Plasmids expressing RET mutants (p.G533C and p.C634Y) and RET wild type were stable transfected into a rat thyroid cell line (PCCL3). Biological and biochemical effects of RET p.G533C were investigated both in vitro and in vivo. Moreover, we report the first case of pheochromocytoma among the RET p.G533C-carriers in this Brazilian family and explore the RET mutational status in DNA isolated from pheochromocytoma. RESULTS: Ectopic expression of RET p.G533C and p.C634Y activates RET/MAPK/ERK pathway at similar levels and significantly increased cell proliferation, compared with RET wild type. We additionally show that p.G533C increased cell viability, anchorage-independent growth, and micronuclei formation while reducing apoptosis, hallmarks of the malignant phenotype. RET p.G533C down-regulates the expression of thyroid specific genes in PCCL3. Moreover, RET p.G533C-expressing cells were able to induce liver metastasis in nude mice. Finally, we described two novel RET variants (G548V and S556T) in the DNA isolated from pheochromocytoma while they were absent in the DNA isolated from blood. CONCLUSIONS: Our in vitro and in vivo analysis indicates that this mutation confers a malignant phenotype to PCCL3 cells. These findings, in association with the report of first case of pheochromocytoma in the Brazilian kindred, suggest that this noncysteine mutation may be more aggressive than was initially considered.
Subject(s)
Adrenal Gland Neoplasms/genetics , Cell Transformation, Neoplastic/genetics , Multiple Endocrine Neoplasia Type 2a/genetics , Mutation , Neoplastic Syndromes, Hereditary/genetics , Pheochromocytoma/genetics , Proto-Oncogene Proteins c-ret/genetics , Thyroid Gland/enzymology , Thyroid Neoplasms/genetics , Adolescent , Adrenal Gland Neoplasms/enzymology , Adrenal Gland Neoplasms/pathology , Analysis of Variance , Animals , Apoptosis , Brazil , Carcinoma, Medullary/congenital , Cell Adhesion , Cell Line , Cell Proliferation , Cell Survival , Cell Transformation, Neoplastic/metabolism , Cell Transformation, Neoplastic/pathology , Enzyme Activation , Extracellular Signal-Regulated MAP Kinases/metabolism , Female , Gene Expression Regulation, Neoplastic , Genetic Predisposition to Disease , Humans , Liver Neoplasms/enzymology , Liver Neoplasms/genetics , Liver Neoplasms/secondary , Male , Mice , Mice, Nude , Micronuclei, Chromosome-Defective , Middle Aged , Multiple Endocrine Neoplasia Type 2a/enzymology , Multiple Endocrine Neoplasia Type 2a/secondary , Neoplastic Syndromes, Hereditary/enzymology , Pedigree , Phenotype , Pheochromocytoma/enzymology , Pheochromocytoma/pathology , Phosphorylation , Proto-Oncogene Proteins c-ret/metabolism , Rats , Rats, Inbred F344 , Thyroid Gland/pathology , Thyroid Neoplasms/enzymology , Thyroid Neoplasms/secondary , TransfectionABSTRACT
Thallium (Tl) is a highly toxic metal though yet its mechanisms are poorly understood. Previously, we demonstrated that rat pheochromocytoma (PC12) cells exposure to thallous (Tl(I)) or thallic (Tl(III)) cations leads to mitochondrial damage and reduced cell viability. In the present work we comparatively characterized the possible pathways involved in Tl(I)- and Tl(III)- (10-100 muM) mediated decrease in PC12 cells viability. We observed that these cations do not cause cell necrosis but significantly increased the number of cells with apoptotic features. Both cations lead to Bax oligomerization and caused apoptosis inducing factor (AIF), endonuclease G (Endo G), and cytochrome c release from mitochondria, but they did not activate caspase dependent DNAse (CAD). Tl(I)- and Tl(III)-dependent caspases 9 and 3 activation followed similar kinetics, with maximal effects at 18 h of incubation. In addition, Tl(I) promoted phosphatidylserine (PS) exposure. Tl(III) induced 2- and 18-fold increase in Fas content and caspase 8 activity, respectively. Together, experimental results show that Tl(I) and Tl(III) induce PC12 cells apoptosis, although differential pathways are involved. While Tl(I)-mediated cell apoptosis was mainly associated with mitochondrial damage, Tl(III) showed a mixed effect triggering both the intrinsic and extrinsic pathways of apoptosis. These findings contribute to a better understanding of the mechanisms underlying Tl-induced loss of cell viability in PC12 cells.
Subject(s)
Adrenal Gland Neoplasms/pathology , Apoptosis/drug effects , Mitochondria/drug effects , Pheochromocytoma/pathology , Thallium/toxicity , Adrenal Gland Neoplasms/enzymology , Animals , Apoptosis Inducing Factor/metabolism , Caspase 3/metabolism , Caspase 8/metabolism , Caspase 9/metabolism , Cell Survival/drug effects , Cytochromes c/metabolism , Deoxyribonucleases/metabolism , Dose-Response Relationship, Drug , Endodeoxyribonucleases/metabolism , Mitochondria/enzymology , Mitochondria/pathology , Necrosis , PC12 Cells , Pheochromocytoma/enzymology , Phosphatidylserines/metabolism , Poly(ADP-ribose) Polymerases/metabolism , Proto-Oncogene Proteins c-bcl-2/metabolism , Rats , Time Factors , bcl-2-Associated X Protein/metabolism , fas Receptor/metabolismABSTRACT
Adrenarche is the maturational increase of adrenal androgens that takes place in 6-8 year old children. In order to study the role of 3 beta HSD in the regulation of the synthesis of human adrenal androgens, the abundance of 3 beta HSD mRNA (Dot Blot and semiquantitative RT-PCR) was measured in 11 human prepubertal and early pubertal adrenal tissues. Subjects were divided in 2 age groups (Gr): Gr1, < 8 years (y) old (n = 6, range 0.1-2.5) and Gr2, > or = 8 y old (n = 5, range 8.0-13.0). Tissue from one adrenal tumor with Cushing's syndrome (TSC) and 2 virilizing adrenal tumors (TV), as well as adrenal cells prepared from the TSC and from 1 TV were also studied. They were maintained in culture for 3 days in basal conditions (BC) and under ACTH and IGF-1 stimulation. mRNA in Gr1 was higher than in Gr2 (Dot blot: 4.65 +/- 2.70 and 0.28 +/- 0.27 AU, p = 0.006; RT-PCR: 21.5 +/- 12.5 and 6.77 +/- 3.78 AU, p = 0.039, respectively). 3 beta HSD mRNA in TSC (8.74 +/- 1.74) was higher than in the 2 TVs (0.47 +/- 0.02 and 0.87 +/- 0.08) p = 0.001. In TSC cells, basal mRNA (0.82 +/- 0.10) decreased under ACTH (0.55 +/- 0.06), p = 0.005, and increased under IGF-1 (2.36 +/- 0.07), p = 0.006. No changes were observed in TV cells. On day 3, TV cells in BC secreted 1170.0 +/- 210.0 and 335.0 +/- 29.0 pmol/10(6) cells in 24 hs of DHEAS and androstenedione, while TSC cells secreted 17.1 +/- 3.5 and 73.7 +/- 11.7, respectively. Values increased under ACTH in TV cells (2006.0 +/- 360.0 and 525.0 +/- 76.0) and in TSC cells (29.8 +/- 5.4 and 366.8 +/- 129) p < 0.05, but they decreased under IGF-1 only in TSC cells (7.9 +/- 2.4 and 43.7 +/- 6.1) p < 0.05. These data support the hypothesis that human adrenarche could be secondary to a decrease of 3 beta HSD mRNA. Our finding that when 3 beta HSD mRNA decreases androgen secretion increases (ACTH) and when 3 beta HSD mRNA increases androgen secretion decreases (IGF-1), strongly suggests that 3 beta HSD has a modulatory role in adrenal androgen steroidogenesis.
Subject(s)
3-Hydroxysteroid Dehydrogenases/metabolism , Adrenal Gland Neoplasms/enzymology , Adrenal Glands/enzymology , Androgens/metabolism , Adolescent , Child , Child, Preschool , Humans , Infant , Male , RNA, Messenger/analysis , RNA, Messenger/metabolismABSTRACT
La adrenarca se caracteriza por el aumento de secreción de andrógenos adrenales. Ocurre entre los 6-8 años de edad en humanos. Con el objetivo de evaluar el posible rol regulatorio de la 3beta HSD en la síntesis de andrógenos en la adrenal humana, se analizó la abundancia del ARNm de 3beta HSD (Dot blot y RT-PCR semicuantitativa(S)) en 11 tejidos adrenales humanos normales en dos grupos (Gr) de edades, Gr1: <8 años (a) (n= 6, r: 0.1-2.5) y Gr2: si 8a (n = 5, r: 8.0-13.0); en tejido de un tumor adrenal con Síndrome de Cushing (TSC) y de 2 T virilizante (TV) y en células adrenales del TSC y 1 TV al 3er día de cultivo (basal y con ACTH e IGF-1). El ARNm de 3beta HSD fue más alto en el Gr1 que en el Gr2 (Dot blot: 4.65 + 2.70 y 0.28 + 0.27 UA, p = 0.006; RT-PCRS: 21.50 + 12.50 y 6.77 + 3.78 UA, p = 0.039 resp). Por otra parte, en el tejido TSC (8.74 + 1.74) fue más alto que en los TV (0.47 + 0.02, 0.87 + 0.08) p = 0.001. En cultivo del TSC el ARNm basal (0.82 + 0.10) disminuyó con ACTH (0.55 + 0.06), p = 0.005 y se incrementó con IGF-1 (2.36 + 0.07) p = 0.006. En el TV no hubo cambios. Al 3er día de cultivo la DHEAS y androstenediona basales fueron en TV 1170.0 + 210.0 y 335.0 + 29.0, TSC 17.1 + 3.5 y 73.7 + 11.7 pmol/10(6) células en 24 hs respectivamente y se incrementaron bajo ACTH en TV (2006.0 + 360.0 y 525.0 + 76.0) y en TSC 29.8 + 5.4 y 366.8 + 129) p<0.05 y disminuyeron con IGF-1 sólo en TSC (7.9 + 2.4 y 43.7 + 6.1) p<0.05. Estos datos sugieren que la adrenarca humana podría ser secundaria a una disminución de la abundancia del ARNm de 3beta HSD. El hecho de que bajo ACTH aumenta la secreción de andrógenos y disminuye el ARNm de 3beta HSD, mientras que el IGF-1 ejerce un efecto inverso, aporta nuevas evidencias del rol regulador ejercido por la 3beta en la síntesis de andrógenos adrenales.
Subject(s)
Child , Humans , Male , Adolescent , Child, Preschool , Infant , 3-Hydroxysteroid Dehydrogenases/metabolism , Adrenal Gland Neoplasms/enzymology , Adrenal Glands/enzymology , Androgens/metabolism , Reverse Transcriptase Polymerase Chain Reaction , RNA, Messenger/analysis , RNA, Messenger/metabolismABSTRACT
La adrenarca se caracteriza por el aumento de secreción de andrógenos adrenales. Ocurre entre los 6-8 años de edad en humanos. Con el objetivo de evaluar el posible rol regulatorio de la 3beta HSD en la síntesis de andrógenos en la adrenal humana, se analizó la abundancia del ARNm de 3beta HSD (Dot blot y RT-PCR semicuantitativa(S)) en 11 tejidos adrenales humanos normales en dos grupos (Gr) de edades, Gr1: <8 años (a) (n= 6, r: 0.1-2.5) y Gr2: si 8a (n = 5, r: 8.0-13.0); en tejido de un tumor adrenal con Síndrome de Cushing (TSC) y de 2 T virilizante (TV) y en células adrenales del TSC y 1 TV al 3er día de cultivo (basal y con ACTH e IGF-1). El ARNm de 3beta HSD fue más alto en el Gr1 que en el Gr2 (Dot blot: 4.65 + 2.70 y 0.28 + 0.27 UA, p = 0.006; RT-PCRS: 21.50 + 12.50 y 6.77 + 3.78 UA, p = 0.039 resp). Por otra parte, en el tejido TSC (8.74 + 1.74) fue más alto que en los TV (0.47 + 0.02, 0.87 + 0.08) p = 0.001. En cultivo del TSC el ARNm basal (0.82 + 0.10) disminuyó con ACTH (0.55 + 0.06), p = 0.005 y se incrementó con IGF-1 (2.36 + 0.07) p = 0.006. En el TV no hubo cambios. Al 3er día de cultivo la DHEAS y androstenediona basales fueron en TV 1170.0 + 210.0 y 335.0 + 29.0, TSC 17.1 + 3.5 y 73.7 + 11.7 pmol/10(6) células en 24 hs respectivamente y se incrementaron bajo ACTH en TV (2006.0 + 360.0 y 525.0 + 76.0) y en TSC 29.8 + 5.4 y 366.8 + 129) p<0.05 y disminuyeron con IGF-1 sólo en TSC (7.9 + 2.4 y 43.7 + 6.1) p<0.05. Estos datos sugieren que la adrenarca humana podría ser secundaria a una disminución de la abundancia del ARNm de 3beta HSD. El hecho de que bajo ACTH aumenta la secreción de andrógenos y disminuye el ARNm de 3beta HSD, mientras que el IGF-1 ejerce un efecto inverso, aporta nuevas evidencias del rol regulador ejercido por la 3beta en la síntesis de andrógenos adrenales. (AU)