Metformin Restrains Pancreatic Duodenal Homeobox-1 (PDX-1) Function by Inhibiting ERK Signaling in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most potent and perilous diseases known, with a median survival rate of 3-5 months due to the combination of only advanced stage diagnosis and ineffective therapeutic options. Metformin (1,1-Dimethylbiguanide hydrochloride), the leading drug used for type 2 diabetes mellitus, emerges as a potential therapy for PDAC and other human cancers. Metformin exerts its anticancer action via a variety of adenosine monophosphate (AMP)-activated protein kinase (AMPK)- dependent and/or AMPK-independent mechanisms. We present data here showing that metformin downregulated pancreatic transcription factor pancreatic duodenal homeobox-1 (PDX-1), suggesting a potential novel mechanism by which metformin exerts its anticancer action. Metformin inhibited PDX-1 expression at both protein and mRNA levels and PDX-1 transactivity as well in PDAC cells. Extracellular signal-regulated kinase (ERK) was identified as a PDX-1-interacting protein by antibody array screening in GFP-PDX-1 stable HEK293 cells. Co-transfection of ERK1 with PDX-1 resulted in an enhanced PDX-1 expression in HEK293 cells in a dose-dependent manner. Immunoprecipitation/Western blotting analysis confirmed the ERK-PDX-1 interaction in PANC-1 cells stimulated by epidermal growth factor (EGF). EGF induced an enhanced PDX-1 expression in PANC-1 cells and this stimulation was inhibited by MEK inhibitor PD0325901. Metformin inhibited EGF-stimulated PDX-1 expression with an accompanied inhibition of ERK kinase activation in PANC- 1 cells. Taken together, our studies show that PDX-1 is a potential novel target for metformin in PDAC cells and that metformin may exert its anticancer action in PDAC by down-regulating PDX-1 via a mechanism involving inhibition of ERK signaling.

77 USE OF SEMINAL PLASMA TO IMPROVE REPRODUCTIVE PERFORMANCE IN ALPACAS (VICUGNA PACOS) FOLLOWING NATURAL MOUNTING

Alpacas are classified as induced ovulators, and an external stimulus is required for the occurrence of ovulation. The seminal plasma (SP) of camelids contains a protein identified as β nerve growth factor with the capacity to induce ovulation and corpus luteum formation. Alpacas have a poor reproductive efficiency and high embryo mortality rate. A study was designed to evaluate the use of SP to improve reproductive performance post natural mating (Exp. 1) and with different mounting time (MT; Exp. 2). Experiment 1: Nonpregnant alpacas (n = 117) exhibiting a dominant follicle = 7 mm, detected by transrectal ultrasonography, were bred by natural mating and then assigned randomly to 1 of 3 treatments: T1 (n = 40), 1 mL of SP IM; T2 (n = 39), 1 mL of GnRH analogue (0.0042 mg of buserelin acetate), IM; and T3 (n = 38), control. Experiment 2: Nonpregnant alpacas (n = 180) exhibiting a follicle = 7 mm were assigned randomly to the following treatments: T1 (n = 30): MT 5 min; T2 (n = 30): MT 5 min + 1 mL of SP; T3 (n = 30): MT 10 min; T4 (n = 30): MT 10 min + 1 mL of SP; T5 (n = 30): MT > 15 min; T6 (n = 30): MT > 15 min + 1 mL of SP. The same male was used for mating females in T1 and T2, T3 and T4, and T5 and T6, respectively. Animals were evaluated by ultrasound with an Aloka SSD 500 (Aloka, Tokyo, Japan) and 5.0-MHz linear transducer on Day 25 for pregnancy diagnosis. In Exp. 1 the conception rate was 67.5, 51.3, and 55.3% for T1, T2, and T3, respectively (P > 0.05). In Exp. 2 the conception rate was 46.2, 67.9, 57.1, 73.3, 61.8, and 72.7% for T1, T2, T3, T4, T5, and T6 (P < 0.05) and was significantly different between T1 v. T2 and T3 v. T4. The results suggest that the use of SP could be one method to improve reproductive performance in alpacas. Research was supported by Project N° 405-PNICP-PIAP-UNMSM.

320 EFFECTS OF DIFFERENT ACTIVATION REGIMENS ON PRONUCLEAR FORMATION AND PRE-IMPLANTATION DEVELOPMENTAL COMPETENCE OF IN VITRO-MATURED BOVINE OOCYTES AFTER INTRACYTOPLASMIC SPERM INJECTION

Intracytoplasmic sperm injection (ICSI) is an assisted reproductive technique that has been used with considerable success in humans; however, in the bovine species the efficiency of this technique is far from optimal. The objective of the present study was to evaluate the effect of 4 chemical activation treatments, 6-dimethylaminopurine (DMAP), cycloheximide (CHX), anisomycin (ANY), and ethanol (EtOH) on the pronuclear formation and embryo development of bovine embryos generated by ICSI. Cumulus-oocyte complexes were aspirated from abattoir ovaries, selected, and matured in 400-µL drops of standard TCM-199 maturation medium for 22 h at 38.5°C and 5% CO2. The ICSI was performed by a standard procedure. Injected oocytes were randomly distributed and activated by 5 µM ionomycin for 5 min (Io) followed by i) 5 µg mL–1 CHX for 5 h (Io/CHX), ii) 3 h window followed by a second Io treatment plus 1.9 mM DMAP for 4 h (2Io/DMAP), iii) 1 µg mL–1 ANY for 5 h (Io/ANY), and iv) 3 h window followed by 7% ethanol (Io/EtoH). Embryos were cultured in 50-µL drops of KSOM medium under mineral oil at 38.5°C and 5% CO2, 5% O2, and 90% N2. Cleavage was recorded at 72 h and blastocyst rate at 192 h. Pronuclear formation analysis was carried out at 18 hpa with Hoechst staining. An oocyte was considered fertilized when 2 polar bodies and 1 female and 1 male pronucleus (or a decondensed sperm head) could be observed. The data were transformed to arcsine, analysed by ANOVA, and means were compared using Tukey's test with Statgraphics Plus 2 Software. Results with a total of 431 injected oocytes (114, 104, 101, and 112 for DMAP, CHX, ANY, and EtOH, respectively) showed differences in cleavage (P < 0.01) in DMAP, CHX, and ANY treatments (86, 72, and 78%, respectively), relative to EtOH (12%). Similarly, the rate of blastocysts/injected oocyte at 192 h was higher with DMAP, CHX, and ANY (41, 20, and 32%, respectively), relative to EtOH (4%). Sham-injected oocytes showed cleavage and blastocyst rates of 67, 43, 68, and 12% and 32, 11, 19, and 5%, for DMAP, CHX, ANY, and EtOH, respectively. Despite the higher developmental rate observed with DMAP, pronuclear formation assessment revealed that fertilization rate was higher in CHX (87%) and ANY (75%) treatments relative to DMAP (35%). In conclusion, the results of the present study show that activation of bovine oocytes after ICSI is more efficient with DMAP and ANY, compared with CHX and EtOH.Provision of ovaries by our local slaughterhouse (Frigorifico Temuco, Chile) and funding support from FONDECYT 1120241 CONICYT, Chile, are gratefully acknowledged.

Proton-neutron pairing correlations in the self-conjugate nucleus (38)K probed via a direct measurement of the isomer shift

A marked difference in the nuclear charge radius was observed between the I^{π}=3^{+} ground state and the I^{π}=0^{+} isomer of ^{38}K and is qualitatively explained using an intuitive picture of proton-neutron pairing. In a high-precision measurement of the isomer shift using bunched-beam collinear laser spectroscopy at CERN-ISOLDE, a change in the mean-square charge radius of ⟨r_{c}^{2}⟩(^{38}K^{m})-⟨r_{c}^{2}⟩(^{38}K^{g})=0.100(6)  fm^{2} was obtained. This is an order of magnitude more accurate than the result of a previous indirect measurement from which it was concluded that both long-lived states in ^{38}K have similar charge radii. Our observation leads to a substantially different understanding since the difference in charge radius is, moreover, opposite in sign to previously reported theoretical predictions. It is demonstrated that the observed isomer shift can be reproduced by large-scale shell-model calculations including proton and neutron excitations across the N,Z=20 shell gaps, confirming the significance of cross-shell correlations in the region of ^{40}Ca.

Involvement of PI3K/Akt and p38 MAPK in the induction of COX-2 expression by bacterial lipopolysaccharide in murine adrenocortical cells

Previous studies from our laboratory demonstrated the involvement of COX-2 in the stimulation of steroid production by LPS in murine adrenocortical Y1 cells, as well as in the adrenal cortex of male Wistar rats. In this paper we analyzed signaling pathways involved in the induction of this key regulatory enzyme in adrenocortical cells and demonstrated that LPS triggers an increase in COX-2 mRNA levels by mechanisms involving the stimulation of reactive oxygen species (ROS) generation and the activation of p38 MAPK and Akt, in addition to the previously demonstrated increase in NFκB activity. In this sense we showed that: (1) inhibition of p38 MAPK or PI3K/Akt (pharmacological or molecular) prevented the increase in COX-2 protein levels by LPS, (2) LPS induced p38 MAPK and Akt phosphorylation, (3) antioxidant treatment blocked the effect of LPS on p38 MAPK phosphorylation and in COX-2 protein levels, (4) PI3K inhibition with LY294002 prevented p38 MAPK phosphorylation and, (5) the activity of an NFκB reporter was decreased by p38 MAPK or PI3K inhibition. These results suggest that activation of both p38 MAPK and PI3K/Akt pathways promote the stimulation of NFκB activity and that PI3K/Akt activity might regulate both p38 MAPK and NFκB signaling pathways. In summary, in this study we showed that in adrenal cells, LPS induces COX-2 expression by activating p38 MAPK and PI3K/Akt signaling pathways and that both pathways converge in the modulation of NFκB transcriptional activity.

Vertically integrated translational studies of PDX1 as a therapeutic target for pancreatic cancer via a novel bifunctional RNAi platform

RNA interference (RNAi) represents a powerful, new tool for scientific investigation as well as a promising new form of targeted gene therapy, with applications currently in clinical trials. Bifunctional short hairpin RNA (shRNA) are synthetic RNAi molecules, engineered to utilize multiple endogenous RNAi pathways to specifically silence target genes. Pancreatic and duodenal homeobox 1 (PDX1) is a key regulator of pancreatic development, β-cell differentiation, normal β-cell function and pancreatic cancer. Our aim is to review the process of identifying PDX1 as a specific, potential RNAi target in pancreatic cancer, as well as the underlying mechanisms and various forms of RNAi, with subsequent testing and development of PDX1-targeted bifunctional shRNA therapy.

134 EFFECT OF REPLACING FETAL BOVINE SERUM BY DIFFERENT GROWTH FACTORS IN THE PRE-IMPLANTATION DEVELOPMENT OF BOVINE EMBRYOS GENERATED BY IN VITRO FERTILIZATION

Different culture systems have been studied that support pre-implantation development of bovine embryos up to the blastocyst stage. However, the use of chemically defined culture systems has been less studied. The objective of the present study was to evaluate the effect, in the developmental potential of in vitro-produced bovine embryos, of replacing fetal bovine serum (FBS) by different growth factors in the maturation and embryo culture media. In experiment 1, oocytes collected by aspiration of ovaries from a local slaughterhouse were matured in standard TCM-199 culture medium at 38.5°C, 5% CO2, and saturation humidity. The effect of insulin-like growth factor 1 (100 ng mL–1), epidermal growth factor (10 ng mL–1), and fibroblast growth factor 2 (500 ng mL–1) was evaluated at 24 h by the presence of a polar body after removal of cumulus-oocyte complexes. In experiment 2, oocytes matured in vitro in the presence of FBS were fertilized by co-incubation with commercial sperm (mL) for 18 h in standard fertilization medium (Fert-TALP). The presumptive zygotes were denuded and randomly allocated in a chemically defined culture medium based on KSOM supplemented with polyvinyl alcohol (PVA), fructose, and each of the growth factors listed previously. Undefined cultured medium was based on KSOM supplemented with 5% FBS. Embryos were cultured at 38.5°C in a mixture of gases and saturation humidity. Cleavage and blastocyst rates were recorded on Days 3 and 7, respectively. Analysis of variance was used to test for statistically significant differences between groups (P < 0.05) using Stat Graphics Plus 2 Software. In cases where statistically significant differences were observed, a multiple comparison test was run using Tukey's test. In experiment 1, a similar maturation rate was observed in all treatments relative to the undefined maturation medium (range = 88–91%). In experiment 2, no differences were observed in the cleavage (79, 87, 85, and 85%) and the blastocyst rates (24, 25, 26, and 30%) for the epidermal growth factor, insulin-like growth factor 1, fibroblast growth factor 2, and FBS treatments, respectively. In conclusion, we demonstrated that maturation of bovine oocytes can be achieved in chemically defined conditions by replacing FBS by each of the growth factors evaluated herein. Furthermore, chemically defined KSOM medium supplemented by any of these growth factors can generate a similar rate of blastocyst than the undefined medium containing FBS. Analyses are under way to evaluate the effect of completely defined culture conditions (maturation and embryo culture) on the pre-implantation development of embryos produced in the presence of these growth factors.