Genetic variations in the PI3K-AKT-mTOR pathway and bladder cancer susceptibility and clinical outcomes

Bladder cancer is the fourth most common cancer in men in the United States. There is compelling evidence supporting that genetic variations contribute to the risk and outcomes of bladder cancer. The PI3K-AKT-mTOR pathway is a major cellular pathway involved in proliferation, invasion, inflammation, tumorigenesis, and drug response. Somatic aberrations of PI3K-AKT-mTOR pathway are frequent events in several cancers including bladder cancer; however, no studies have investigated the role of germline genetic variations in this pathway in bladder cancer. In this project, we used a large case control study to evaluate the associations of a comprehensive catalogue of SNPs in this pathway with bladder cancer risk and outcomes. Three SNPs in RAPTOR were significantly associated with susceptibility: rs11653499 (OR: 1.79, 95%CI: 1.24–2.60), rs7211818 (OR: 2.13, 95%CI: 1.35–3.36), and rs7212142 (OR: 1.57, 95%CI: 1.19–2.07). Two haplotypes constructed from these 3 SNPs were also associated with bladder cancer risk. In combined analysis, a significant trend was observed for increased risk with an increase in the number of unfavorable genotypes (P for trend<0.001). Classification and regression tree analysis identified potential gene-environment interactions between RPS6KA5 rs11653499 and smoking. In superficial bladder cancer, we found that PTEN rs1234219 and rs11202600, TSC1 rs7040593, RAPTOR rs901065, and PIK3R1 rs251404 were significantly associated with recurrence in patients receiving BCG. In muscle invasive and metastatic bladder cancer, AKT2 rs3730050, PIK3R1 rs10515074, and RAPTOR rs9906827 were associated with survival. Survival tree analysis revealed potential gene-gene interactions: patients carrying the unfavorable genotypes of PTEN rs1234219 and TSC1 rs704059 exhibited a 5.24-fold (95% CI: 2.44–11.24) increased risk of recurrence. In combined analysis, with the increasing number of unfavorable genotypes, there was a significant trend of higher risk of recurrence and death (P for trend<0.001) in Cox proportional hazard regression analysis, and shorter event (recurrence and death) free survival in Kaplan-Meier estimates (P log rank<0.001). This study strongly suggests that genetic variations in PI3K-AKT-mTOR pathway play an important role in bladder cancer development. The identified SNPs, if validated in further studies, may become valuable biomarkers in assessing an individual's cancer risk, predicting prognosis and treatment response, and facilitating physicians to make individualized treatment decisions. ^

DIRECT EFFECTS OF METFORMIN ON PI3K AND RAS SIGNALING IN ENDOMETRIAL CANCER

Metformin has antiproliferative effects through the activation of AMPK and has gained interest as an antineoplastic agent in several cancer types, although studies in endometrial cancer (EC) are limited. The aims of this project were to evaluate pathways targeted by metformin in EC, investigate mechanisms by which metformin exerts its antiproliferative effects, and explore rational combination therapies with other targeted agents. Three EC cell lines were used to evaluate metformin’s effect on cell proliferation, PI3K and Ras-MAPK signaling, and apoptosis. A xenograft mouse model was also used to evaluate the effects of metformin treatment on in vivo tumor growth. These preliminary studies demonstrated that K-Ras mutant cell lines exhibited a decreased proliferative rate, reduced tumor growth, and increased apoptosis in response to metformin compared to K-Ras wild-type cells. To test the hypothesis that mutant K-Ras may predict response to metformin, murine EC cells with loss of PTEN and expressing mutant K-RasG12D were transfected to re-express PTEN or have K-Ras silenced using siRNA. While PTEN expression did not alter response to metformin, cells in which K-Ras was silenced displayed reduced sensitivity to metformin. Mislocalization of K-Ras to the cytoplasm is associated with decreased signaling and induction of apoptosis. Metformin’s effect on K-Ras localization was analyzed by confocal microscopy in cells expressing oncogenic GFP-K-RasG12V. Metformin demonstrated concentration-dependent mislocalization of K-Ras to the cytoplasm. Mislocalization of K-Ras to the cytoplasm was confirmed in K-Ras mutant EC cells (Hec1A) by cell fractionation in response to metformin 1 and 5 mM (p=0.008 and p=0.004). This effect appears to be AMPK-independent as combined treatment with Compound C, an AMPK inhibitor, did not alter K-Ras localization. Furthermore, treatment of EC cells with metformin in combination with PI3K inhibitors resulted in a significant decrease in proliferation than either agent or metformin alone. While metformin exerts antineoplastic effects by activation of AMPK and decreased PI3K signaling, our data suggest that metformin may also disrupt localization of K-Ras and hence its signaling in an AMPK-independent manner. This has important implications in defining patients who may benefit from metformin in combination with other targeted agents, such as mTOR inhibitors.

ROLE OF MIR-19A RELEASED BY INFLAMMATORY BREAST CANCER CELLS IN THE REGULATION OF DENDRITIC CELL FUNCTIONS: IN VITRO MODEL OF CROSSTALK IN THE TUMOR MICROENVIRONMENT OF INFLAMMATORY BREAST CANCER

Inflammatory breast cancer (IBC) is a rare but very aggressive form of locally advanced breast cancer (1-6% of total breast cancer patients in United States), with a 5-year overall survival rate of only 40.5%, compared with 85% of the non-IBC patients. So far, a unique molecular signature for IBC able to explain the dramatic differences in the tumor biology between IBC and non-IBC has not been identified. As immune cells in the tumor microenvironment plays an important role in regulating tumor progression, we hypothesized that tumor-associated dendritic cells (TADC) may be responsible for regulating the development of the aggressive characteristics of IBC. MiRNAs can be released into the extracellular space and mediate the intercellular communication by regulating target gene expression beyond their cells of origin. We hypothesized that miRNAs released by IBC cells can induce an increased activation status, secretion of pro-inflammatory cytokines and migration ability of TADC. In an in vitro model of IBC tumor microenvironment, we found that the co-cultured of the IBC cell line SUM-149 with immature dendritic cells (iDCSUM-149) induced a higher degree of activation and maturation of iDCSUM-149 upon stimulation with lipopolysaccharide (LPS) compared with iDCs co-cultured with the non-IBC cell line SUM-159 (iDCSUM-159), resulting in: increased expression of the costimulatory and activation markers; higher production of pro-inflammatory cytokines (TNF-a, IL-6); and 3) higher migratory ability. These differences were due to the exosome-mediated transfer of miR-19a and miR-146a from SUM-149 and SUM-159, respectively, to iDCs, causing the downregulation of the miR-19a target genes PTEN, SOCS-1 and the miR-146a target genes IRAK1, TRAF6. PTEN, SOCS-1 and IRAK1, TRAF6 are important negative and positive regulator of cytokine- and TLR-mediated activation/maturation signaling pathway in DCs. Increased levels of IL-6 induced the upregulation of miR-19a synthesis in SUM-149 cells that was associated with the induction of CD44+CD24-ALDH1+ cancer stem cells (CSCs) with epithelial-to-mesenchymal transition (EMT) characteristics. In conclusion, in IBC tumor microenvironment IL-6/miR-19a axis can represent a self-sustaining loop able to maintain a pro-inflammatory status of DCs, leading to the development of tumor cells with high metastatic potential (EMT CSCs) responsible of the poor prognosis in IBC patients.

Microarray analysis of autoimmune diseases by machine learning procedures

—Microarray-based global gene expression profiling, with the use of sophisticated statistical algorithms is providing new insights into the pathogenesis of autoimmune diseases. We have applied a novel statistical technique for gene selection based on machine learning approaches to analyze microarray expression data gathered from patients with systemic lupus erythematosus (SLE) and primary antiphospholipid syndrome (PAPS), two autoimmune diseases of unknown genetic origin that share many common features. The methodology included a combination of three data discretization policies, a consensus gene selection method, and a multivariate correlation measurement. A set of 150 genes was found to discriminate SLE and PAPS patients from healthy individuals. Statistical validations demonstrate the relevance of this gene set from an univariate and multivariate perspective. Moreover, functional characterization of these genes identified an interferon-regulated gene signature, consistent with previous reports. It also revealed the existence of other regulatory pathways, including those regulated by PTEN, TNF, and BCL-2, which are altered in SLE and PAPS. Remarkably, a significant number of these genes carry E2F binding motifs in their promoters, projecting a role for E2F in the regulation of autoimmunity.

Phosphatidylinositol 3-kinase signaling mediates angiogenesis and expression of vascular endothelial growth factor in endothelial cells

Phosphatidylinositol 3-kinase (PI 3-kinase) is a signaling molecule that controls numerous cellular properties and activities. The oncogene v-p3k is a homolog of the gene coding for the catalytic subunit of PI 3-kinase, p110α. P3k induces transformation of cells in culture, formation of hemangiosarcomas in young chickens, and myogenic differentiation in myoblasts. Here, we describe a role of PI 3-kinase in angiogenesis. Overexpression of the v-P3k protein or of cellular PI 3-kinase equipped with a myristylation signal, Myr-P3k, can induce angiogenesis in the chorioallantoic membrane (CAM) of the chicken embryo. This process is characterized by extensive sprouting of new blood vessels and enlargement of preexisting vessels. Overexpression of the myristylated form of the PI 3-kinase target Akt, Myr-Akt, also induces angiogenesis. Overexpression of the tumor suppressor PTEN or of dominant-negative constructs of PI 3-kinase inhibits angiogenesis in the yolk sac of chicken embryos, suggesting that PI 3-kinase and Akt signaling is required for normal embryonal angiogenesis. The levels of mRNA for vascular endothelial growth factor (VEGF) are elevated in cells expressing activated PI 3-kinase or Myr-Akt. VEGF mRNA levels are also increased by insulin treatment through the PI 3-kinase-dependent pathway. VEGF mRNA levels are decreased in cells treated with the PI 3-kinase inhibitor LY294002 and restored by overexpression of v-P3k or Myr-Akt. Overexpression of VEGF by the RCAS vector induces angiogenesis in chicken embryos. These results suggest that PI 3-kinase plays an important role in angiogenesis and regulates VEGF expression.

Protein-tyrosine phosphatase activity regulates osteoclast formation and function: inhibition by alendronate.

Alendronate (ALN), an aminobisphosphonate used in the treatment of osteoporosis, is a potent inhibitor of bone resorption. Its molecular target is still unknown. This study examines the effects of ALN on the activity of osteoclast protein-tyrosine phosphatase (PTP; protein-tyrosine-phosphate phosphohydrolase, EC 3.1.3.48), called PTPepsilon. Using osteoclast-like cells generated by coculturing mouse bone marrow cells with mouse calvaria osteoblasts, we found by molecular cloning and RNA blot hybridization that PTPepsilon is highly expressed in osteoclastic cells. A purified fusion protein of PTPepsilon expressed in bacteria was inhibited by ALN with an IC50 of 2 microM. Other PTP inhibitors--orthovanadate and phenylarsine oxide (PAO)-inhibited PTPepsilon with IC50 values of 0.3 microM and 18 microM, respectively. ALN and another bisphosphonate, etidronate, also inhibited the activities of other bacterially expressed PTPs such as PTPsigma and CD45 (also called leukocyte common antigen). The PTP inhibitors ALN, orthovanadate, and PAO suppressed in vitro formation of multinucleated osteoclasts from osteoclast precursors and in vitro bone resorption by isolated rat osteoclasts (pit formation) with estimated IC50 values of 10 microM, 3 microM, and 0.05 microM, respectively. These findings suggest that tyrosine phosphatase activity plays an important role in osteoclast formation and function and is a putative molecular target of bisphosphonate action.

Crystallographic evidence for the action of potassium, thallium, and lithium ions on fructose-1,6-bisphosphatase.

Fructose-1,6-bisphosphatase (Fru-1,6-Pase; D-fructose-1,6-bisphosphate 1-phosphohydrolase, EC 3.1.3.11) requires two divalent metal ions to hydrolyze alpha-D-fructose 1,6-bisphosphate. Although not required for catalysis, monovalent cations modify the enzyme activity; K+ and Tl+ ions are activators, whereas Li+ ions are inhibitors. Their mechanisms of action are still unknown. We report here crystallographic structures of pig kidney Fru-1,6-Pase complexed with K+, Tl+, or both Tl+ and Li+. In the T form Fru-1,6-Pase complexed with the substrate analogue 2,5-anhydro-D-glucitol 1,6-bisphosphate (AhG-1,6-P2) and Tl+ or K+ ions, three Tl+ or K+ binding sites are found. Site 1 is defined by Glu-97, Asp-118, Asp-121, Glu-280, and a 1-phosphate oxygen of AhG-1,6-P2; site 2 is defined by Glu-97, Glu-98, Asp-118, and Leu-120. Finally, site 3 is defined by Arg-276, Glu-280, and the 1-phosphate group of AhG-1,6-P2. The Tl+ or K+ ions at sites 1 and 2 are very close to the positions previously identified for the divalent metal ions. Site 3 is specific to K+ or Tl+. In the divalent metal ion complexes, site 3 is occupied by the guanidinium group of Arg-276. These observations suggest that Tl+ or K+ ions can substitute for Arg-276 in the active site and polarize the 1-phosphate group, thus facilitating nucleophilic attack on the phosphorus center. In the T form complexed with both Tl+ and Li+ ions, Li+ replaces Tl+ at metal site 1. Inhibition by lithium very likely occurs as it binds to this site, thus retarding turnover or phosphate release. The present study provides a structural basis for a similar mechanism of inhibition for inositol monophosphatase, one of the potential targets of lithium ions in the treatment of manic depression.

Remodelamento da matriz extracelular da medula óssea em desnutrição protéica: possível relação da via de AKT com a expressão de fibronectina e metaloproteinases de matriz

A desnutrição proteica (DP) pode ocasionar alterações na matriz extracelular (MEC) de diferentes órgãos e tecidos, inclusive o hematopoético, com comprometimento funcional. Estudos do nosso laboratório demonstraram, em modelo murino de DP, aumento da expressão proteica de fibronectina (FN) no estroma medular ósseo in vivo, principalmente na região subendosteal (local de fixação da célula tronco progenitora hemopoética). Já in vitro, no estroma medular ósseo, observou-se tanto o aumento quanto a diminuição de FN e a presença de suas isoformas. Essas alterações de FN parecem estar envolvidas com a hipoplasia da medula óssea (MO) em camundongos desnutridos. As modificações quantitativas de FN podem ser devidas: (i) à ação das metaloproteinases de matriz (MMP) responsáveis pela degradação das proteínas da MEC; (ii) aos inibidores de metaloproteinases (TIMP) que regulam a degradação da MEC; (iii) às alterações transcricionais, reguladas pela via de AKT/mTOR, que controla os splicing alternativos na FN, resultando em isoformas dessa proteína; (iv) a processos pós-transcricionais modulados por LC3, que aumenta a tradução do RNAm de FN. Assim, o objetivo deste estudo foi elucidar os mecanismos que alteram o turnover de FN no estroma medular ósseo em modelo murino de DP. Utilizamos camundongos, C57BL/6J machos, adultos, separados em dois grupos: controle e desnutrido, alimentados, ad libitum, com ração contendo 12% e 2% de proteína, respectivamente. Após cinco semanas de indução à desnutrição os camundongos foram eutanasiados, e coletado o material biológico. Avaliamos: o estado nutricional, o hematológico, a histologia da MO femoral bem como a determinação imunohistoquímica da FN, MMP-2 e MMP-9, determinação da expressão de FN e suas isoformas em células totais da MO, o estabelecimento do estroma medular ósseo in vitro, por 28 e 35 dias de cultivo. A partir das culturas foram avaliadas a expressão de RNAm de FN e suas isoformas, MMP-2, MMP-9, TIMP-1, TIMP-2, AKT, mTOR e LC3α e β, quantificação de MMP-2, MMP-9, TIMP-1, TIMP-2,TNFα, TGFβ e IL-1β e determinação de LC3β e proteínas da via de AKT/mTOR. Não observamos alterações na expressão do RNAm de FN e suas isoformas ex vivo e in vitro, mas um aumento da deposição de FN na MO.Também não observamos modificações na imunolocalização de MMP-2 e MMP-9 na MO e na atividade dessas proteínas no sobrenadante de culturas de células estromais in vitro, mas houve aumento da expressão do RNAm de MMP-9 em 28 dias de cultivo. Não detectamos alterações na expressão de RNAm e na concentração de TIMP-1 e TIMP-2 no sobrenadante das culturas. Houve redução significativa de TNFα e TGFβ no sobrenadante das culturas de 28 dias. Observamos aumento da expressão do RNAm de mTOR em culturas de 28 dias e LC3α e LC3β em 35 dias de células estromais. Encontramos menor fosforilação de PI3K, AKT, PTEN, mTOR e mTOR total e aumento de LC3β em culturas de 28 dias, mas redução de LC3β em 35 dias. Em função dos dados inferimos que a DP conduz a alterações da FN que não estão relacionadas à ação de MMPs e TIMPs e sim a modificações de LC3β e da via de AKT/mTOR.

Loss of Akt activity increases circulating soluble endoglin release in preeclampsia:identification of inter-dependency between Akt-1 and heme oxygenase-1

Aims - Endothelial dysfunction is a hallmark of preeclampsia. Desensitization of the phosphoinositide 3-kinase (PI3K)/Akt pathway underlies endothelial dysfunction and haeme oxygenase-1 (HO-1) is decreased in preeclampsia. To identify therapeutic targets, we sought to assess whether these two regulators act to suppress soluble endoglin (sEng), an antagonist of transforming growth factor-ß (TGF-ß) signalling, which is known to be elevated in preeclampsia. Methods and results - Vascular endothelial growth factor-A (VEGF-A), fibroblast growth factor (FGF-2), angiopoietin-1 (Ang-1), and insulin, which all activate the PI3K/Akt pathway, inhibited the release of sEng from endothelial cells. Inhibition of the PI3K/Akt pathway, by overexpression of phosphatase and tensin homolog (PTEN) or a dominant-negative isoform of Akt (Aktdn) induced sEng release from endothelial cells and prevented the inhibitory effect of VEGF-A. Conversely, overexpression of a constitutively active Akt (Aktmyr) inhibited PTEN and cytokine-induced sEng release. Systemic delivery of Aktmyr to mice significantly reduced circulating sEng, whereas Aktdn promoted sEng release. Phosphorylation of Akt was reduced in preeclamptic placenta and this correlated with the elevated level of circulating sEng. Knock-down of Akt using siRNA prevented HO-1-mediated inhibition of sEng release and reduced HO-1 expression. Furthermore, HO-1 null mice have reduced phosphorylated Akt in their organs and overexpression of Aktmyr failed to suppress the elevated levels of sEng detected in HO-1 null mice, indicating that HO-1 is required for the Akt-mediated inhibition of sEng. Conclusion - The loss of PI3K/Akt and/or HO-1 activity promotes sEng release and positive manipulation of these pathways offers a strategy to circumvent endothelial dysfunction.

VEGF induces Tie2 shedding via a phosphoinositide 3-kinase/Akt dependent pathway to modulate Tie2 signaling

Objective— Tie2 and its ligands, the angiopoietins (Ang), are required for embryonic and postnatal angiogenesis. Previous studies have demonstrated that Tie2 is proteolytically cleaved, resulting in the production of a 75-kDa soluble receptor fragment (sTie2). We investigated mechanisms responsible for Tie2 shedding and its effects on Tie2 signaling and endothelial cellular responses. Methods and Results— sTie2 bound both Ang1 and Ang2 and inhibited angiopoietin-mediated Tie2 phosphorylation and antiapoptosis. In human umbilical vein endothelial cells, Tie2 shedding was both constitutive and induced by treatment with PMA or vascular endothelial growth factor (VEGF). Constitutive and VEGF-inducible Tie2 shedding were mediated by PI3K/Akt and p38 MAPK. Tie2 shedding was blocked by pharmacological inhibitors of either PI3K or Akt as well as by overexpression of the lipid phosphatase PTEN. In contrast, sTie2 shedding was enhanced by overexpression of either dominant negative PTEN, which increased Akt phosphorylation, or constitutively active, myristoylated Akt. Conclusions— These findings demonstrate that VEGF regulates angiopoietin-Tie2 signaling by inducing proteolytic cleavage and shedding of Tie2 via a novel PI3K/Akt-dependent pathway. These results suggest a previously unrecognized mechanism by which VEGF may inhibit vascular stabilization to promote angiogenesis and vascular remodeling.

Activation of vascular endothelial growth factor receptor-1 sustains angiogenesis and Bcl-2 expression via the phosphatidylinositol 3-kinase pathway in endothelial cells

Vascular insufficiency and retinal ischemia precede many proliferative retinopathies and stimulate secretion of various vasoactive growth factors, including vascular endothelial growth factor (VEGF) and placenta growth factor (PlGF). It is unclear, however, how PlGF, which is elevated in proliferative diabetic retinopathy and is a VEGF homolog that binds only to VEGF receptor (VEGFR)-1, promotes pathological angiogenesis. When primary microvascular endothelial cells were grown on collagen gels, PlGF-containing ligands upregulated Bcl-2 expression and stimulated the formation of capillary-like tube networks that were retained for up to 14 days in culture. The inhibition of VEGFR-1 results in a dramatic decrease in the number of capillary connections, indicating that VEGFR-1 ligands promote branching angiogenesis. In contrast, VEGF-induced tube formations and Bcl-2 expression were significantly decreased at the end of this period. Flow cytometry analysis of annexin-V/propidium iodide-stained cells revealed that PlGF and PlGF/VEGF heterodimer inhibited apoptosis in serum-deprived endothelial cells. These two growth factors stimulated a survival signaling pathway phosphatidylinositol 3-kinase (PI3K), as identified by increased Akt phosphorylation and because blocking PI3K signalling by adenovirus-mediated overexpression of wild-type phosphatase and tensin homolog on chromosome 10 (PTEN) disrupted angiogenesis and decreased Bcl-2 expression by PlGF and PlGF/VEGF heterodimer, whereas a dominant-negative PTEN mutant enhanced endothelial sprout formation and Bcl-2 expression. Together, these findings indicate that PlGF-containing ligands contribute to pathological angiogenesis by prolonging cell survival signals and maintaining vascular networks.

Glycogen Synthase Kinase 3 influences cell motility and chemotaxis by regulating phosphatidylinositol 3 kinase localization in Dictyostelium discoideum

Glycogen Synthase Kinase 3 (GSK3), a serine/threonine kinase initially characterized in the context of glycogen metabolism, has been repeatedly realized as a multitasking protein that can regulate numerous cellular events in both metazoa and protozoa. I recently found GSK3 plays a role in regulating chemotaxis, a guided cell movement in response to an external chemical gradient, in one of the best studied model systems for chemotaxis - Dictyostelium discoideum. ^ It was initially found that comparing to wild type cells, gsk3 - cells showed aberrant chemotaxis with a significant decrease in both speed and chemotactic indices. In Dictyostelium, phosphatidylinositol 3,4,5-triphosphate (PIP3) signaling is one of the best characterized pathways that regulate chemotaxis. Molecular analysis uncovered that gsk3- cells suffer from high basal level of PIP3, the product of PI3K. Upon chemoattractant cAMP stimulation, wild type cells displayed a transient increase in the level of PIP3. In contrast, gsk3- cells exhibited neither significant increase nor adaptation. On the other hand, no aberrant dynamic of phosphatase and tensin homolog (PTEN), which antagonizes PI3K function, was observed. Upon membrane localization of PI3K, PI3K become activated by Ras, which will in turn further facilitate membrane localization of PI3K in an F-Actin dependent manner. The gsk3- cells treated with F-Actin inhibitor Latrunculin-A showed no significant difference in the PIP3 level. ^ I also showed GSK3 affected the phosphorylation level of the localization domain of PI3K1 (PI3K1-LD). PI3K1-LD proteins from gsk3- cells displayed less phosphorylation on serine residues compared to that from wild type cells. When the potential GSK3 phosphorylation sites of PI3K1-LD were substituted with aspartic acids (Phosphomimetic substitution), its membrane localization was suppressed in gsk3- cells. When these serine residues of PI3K1-LD were substituted with alanine, aberrantly high level of membrane localization of the PI3K1-LD was monitored in wild type cells. Wild type, phosphomimetic, and alanine substitution of PI3K1-LD fused with GFP proteins also displayed identical localization behavior as suggested by the cell fraction studies. Lastly, I identified that all three potential GSK3 phosphorylation sites on PI3K1-LD could be phosphorylated in vitro by GSK3.^

Toward an effective strategy in glioblastoma treatment. Part I: resistance mechanisms and strategies to overcome resistance of glioblastoma to temozolomide.

International audience

Dermatofibrosarcoma protuberans en pacientes pediátricos

Antecedentes y Objetivos. Presentamos 3 casos de dermatofibrosarcomaprotuberans (DFSP) en pacientes pediátricos para documentar la presentación clínica poco frecuente de esta patología. Pacientes y Método. Realizamos un análisis descriptivo retrospectivo de los 3 últimos casos de DFSP en nuestro centro durante los años 2010-2013. Resultados. Una niña de 12 años remitida desde otra institución por DFSP en parte distal del muslo, en la que ampliamos bordes quirúrgicos de resección en 3 cm y practicamos cobertura con dermis artificial e injerto autólogo; tras 1 año de observación sin recidiva, realizamos reconstrucción del defecto mediante injertos autólogos de grasa. Otra niña de 12 años diagnosticada de Síndrome de Hamartomatosis Múltiple asociado al gen PTEN, que presentó DFSP en labio mayor derecho y en mama derecha, recidivante en esta última localización. Por último, un DFSP congénito en una paciente remitida a los 3 meses de vida con tumoración gigante de pared abdominal. El diagnóstico orientativo inicial con resonancia magnética con gadolino, solo se confirmó finalmente por los hallazgos histopatológicos de la pieza de resección; ni la punción aspiración ni la biopsia cutánea lograron confirmar el diagnóstico. Conclusiones. El DFSP es un tipo de sarcoma raro de la piel del niño y del adulto, localmente agresivo y con una alta tasa de recidiva. La escisión local amplia puede provocar mutilaciones y desfigurar al paciente; por ello la cirugía micrográfica de Mohs permite reducir los márgenes quirúrgicos.

Implicación de LKB1 en la patogénesis y progresión del cáncer de próstata.

303 p.