P3-18-03: In Vitro Potency of mTOR Kinase (TOR1/TOR2) Inhibitor, INK128 in ER+ and HER2 Overexpressing Breast Cancer Cells

Background

Persistent activation of the PI3K-AKT-mTOR1/2 signaling pathway drives aberrant cell growth and proliferation in a variety of tumor types including breast tumors. Recent works have demonstrated a strong association between mutational activation of PIK3CA or loss of function of PTEN and resistance to therapies targeted against the ER or HER2 pathway.

Purpose: Since PI3K-AKT-mTOR is one of the major signaling pathways responsible for the progression of breast cancer, as well as appears to be upregulated during development of the resistance to the endocrine and trastuzumab treatment, suppression of this pathway by administration of INK128 (mTOR1/2 kinase inhibitor) may therefore be efficacious in ER+ and HER2+ breast cancer models.

Experimental Design: To examine this possibility, INK128 was treated in ER+ (MCF7, BT483, T47D and MDA-MB-415), trastuzumab-sensitive HER2+ (BT474), trastuzumab-resistant (BT474HR), and PIK3CA mutated/HER2+ breast cancer cells (HCC1954 and UACC893). We have tested the effects of INK128 on the, (a) cell survival/proliferation, (b) integrin-directed cell migration, and small GTP-ase activation, (c) downstream signaling pathways for proliferation and apoptosis, and (d) 3D ON-TOP-colony formation.

Results: Treatment of ER+ and HER2+ cell lines with INK128 in vitro showed that 1) cell lines were sensitive to single agent INK128 with 50% inhibitory concentration ranging from 15 nM-10 μM in ER+ cell lines and 20 nM −50 nM in HER2+ cell lines, 2) 70–80% anti-proliferative activities were observed on 3D-ON TOP colony formation assay in both ER+ and HER2+ cells, 3) INK128 dose- and time-dependently blocked downstream effectors of mTOR1/2 pathway i.e. p-AKT (at Ser473), p-P70S6K, p-S6 ribosomal protein, p-4EBP1(interestingly, potent inhibition was also observed in cell line resistant to trastuzumab), 4) INK128 also blocked AKT phosphorylation at Thr308 (although in lesser extent than at Ser473), 5) rapalog-mediated AKT activation was blocked when cells were treated with INK128, 6) in ER+ cell lines INK128 more efficiently blocked p-4EBP1 than rapalog, 7) HER3 expression was significantly upregulated following treatment of trastuzumab-resistant cells (BT474HR) with INK128, and 8) integrin-dependent cell migration was significantly abrogated with INK128 in association with inhibition of RAC1-GTP.

Conclusion: Our preclinical in vitro data demonstrate that concurrent inhibition of mTOR1and mTOR2 is likely to be a more effective in both ER+ and HER2+ breast cancer cells than the inhibition of mTOR1 alone. We are currently studying the effect of INK128 on downstream apoptotic signals in ER+ and HER2+ cell lines, the results of which will be presented in the meeting.

INK128 was generously supplied by Inkellikine, San Diego, CA.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-18-03.

Differential Wnt pathway activation in triple negative breast cancers comparative to HER2 and hormone positive breast cancers identified from formalin-fixed, paraffin-embedded tissues

Abstract #43

Background: Patients afflicted with triple negative (TN) breast cancer (BC) are typically younger and have the worst prognosis of any BC subtype as a result of its aggressive and invasive phenotype. TN BC has been well studied with respect to the associative and prognostic values of its mRNA expression profiles. We have used the Illumina DASL (cDNA mediated, Annealing, Selection, Extension, and Ligation) platform to characterize 502 genes from 96 BC patients sourced from formalin-fixed, paraffin-embedded (FFPE) tissues. RNA extracted from FFPE tissues is highly fragmented and typically unsuited for expression platforms, but recent advances have allowed for accurate expression profiling of RNA from FFPE tissues. This 96 patient cohort included 21 TN BC patients identified by immunohistochemistry (IHC); differential analysis of TN expression was integrated with known pathway mechanisms and identified activation of the Wnt pathway in TN tumors.
 Material and Methods: The Illumina DASL assay was used to measure mRNA expression levels from BC patients obtained from St. Mary's Hospital, Montreal, Quebec. RNA was extracted from three 5µm tissue sections from FFPE blocks using the RNA High Pure Kit (Roche). Differential mRNA regulation was identified by Significance Analysis of Microarrays (SAM) software using a false discover rate (FDR, q-value < 0.01) or a Bonferroni corrected two-tailed student's t-test (p-value < 0.05). IHC concordance was measured by mRNA expression fold-change for positive versus negative IHC categories.
 Results: 165 samples from 96 patients were characterized for mRNA expression on 1,488 probes across 502 genes in the DASL assay. Quality control limited the analysis to 150 samples from 91 patients over 500 genes. Comparison of the TN subtype relative to HER2 positive and hormone positive breast carcinomas identified up-regulation [fold-change] of MMP7 [2.9], MMP9 [2.0], MMP1 [1.8], NOTCH1 [1.5], FZD7 [1.5], PPARD [1.3], CCND2 [1.2], MET [1.3], MYC [1.5], and MYCN [2.0] in the TN subtype. Most of these genes are either a component or downstream target of the Wnt signaling pathway. Down-regulated relevant genes included ESR1 [-8.4], PGR [-3.9], ERBB2 [-3.4] as expected, as well as ERRB3, ERBB4, GLI3, TFF1, LAF4/AFF3, and AR.
 Discussion: Down-regulation of TFF1 suggests inhibition of the ERK/MAPK pathways which have complex effects on cell-cell adhesion. In combination with over-expression of MMPs 1, 7, and 9, these changes may contribute to the invasive nature of TN BCs. GLI3 down-regulation may attenuate Hedgehog signaling potentially contributing to Wnt activation, further leading to cell migration, invasion, and decrease in cell adhesion to cognate integrin-matrix interaction Up-regulation of both the FZD7 receptor as well as the Wnt targets MMP7, MYC, MYCN, PPARD, and CCND2 strongly suggest Wnt pathway activation in the TN subtype.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 43.

Invited review: cGMP-dependent protein kinase signaling mechanisms in smooth muscle: from the regulation of tone to gene expression

cGMP is a second messenger that produces its effects by interacting with intracellular receptor proteins. In smooth muscle cells, one of the major receptors for cGMP is the serine/threonine protein kinase, cGMP-dependent protein kinase (PKG). PKG has been shown to catalyze the phosphorylation of a number of physiologically relevant proteins whose function it is to regulate the contractile activity of the smooth muscle cell. These include proteins that regulate free intracellular calcium levels, the cytoskeleton, and the phosphorylation state of the regulatory light chain of smooth muscle myosin. Other studies have shown that vascular smooth muscle cells (VSMCs) that are cultured in vitro may cease to express PKG and will, coincidentally, acquire a noncontractile, synthetic phenotype. The restoration of PKG expression to the synthetic phenotype VSMC results in the cells acquiring a more contractile phenotype. These more recent studies suggest that PKG controls VSMC gene expression that, in turn, regulates phenotypic modulation of the cells. Therefore, the regulation of PKG gene expression appears to be linked to phenotypic modulation of VSMC. Because several vascular disorders are related to the accumulation of synthetic, fibroproliferative VSMC in the vessel wall, it is likely that changes in the activity of the nitric oxide/cGMP/PKG pathway is involved the development of these diseases.

A simultaneous ex vivo model of embryogenesis: I. Organogenesis

In vivo culture of chick embryo was carried out to develop an experimental interphase between in vitro and in vivo study of embryonic physiology. In the process, a simultaneous model of vasculogenesis and organogenesis has been worked out, which is impossible to achieve in mammalian system. Both early (40 hours of incubation) and late (64 & 88 hours of incubation) hours of cultures were conducted for morphological and morphometric studies. A new combination of stains was used in place of conventional haematoxylin and eosin in 40 hours old whole-mount of embryos. Semithin plastic sections were etched for haematoxylin/pyronin stain in addition to paraffin (both normal and enblock) sections. Specific stains (histological, enzyme histochemical or immunohistochemical) were chosen according to the specific organs/areas studied. Immunohistochemistry and NADPH-diaphorase activity were standardized in whole-mount of embryos. Morphometry was done using camera lucida and quantitative image analysis system. A parallel preparation of extra embryonic whole-mounts, paraffin and semithin plastic sections with different types of stainings provides evidence for the scope of the simultaneous study of vasculogenesis. Thus the morphological and morphometric data presented in this and the succeeding article describe the scope and avenues for the use of ex vivo model in various aspects of embryonic physiology, preliminary drug trials/metabolism, radiology, teratology and toxicology.

Structure and promoter/leader deletion analysis of mirabilis mosaic virus (MMV) full-length transcript promoter in transgenic plants

A full-length transcript (FLt) promoter fragment was isolated from a genomic clone of mirabilis mosaic virus (MMV), a double-stranded DNA plant pararetrovirus belonging to the caulimovirus family. The boundaries required for maximal promoter expression were defined by 5' and 3' deletion analysis of the MMV promoter fragments coupled to a GUS reporter gene. The expression patterns of these chimeric gene constructs were evaluated both in transgenic Nicotiana tabacum cv. Samsun NN plants and in protoplast transient expression experiments. A 360 bp FLt promoter fragment (sequence -297 to +63 from the transcription start site) was found sufficient for strong promoter activity. The transcription start site (TSS) of the MMV FLt promoter was determined by primer extension analysis using total RNA isolated from transgenic plants containing a MMV promoter:uidA fusion gene. Analysis of the 5' and 3' deletion constructs showed that an upstream region (sequence -248 to -193 from the transcription start site) is required for the MMV FLt promoter activity along with the as-1, TATA box regions. In addition, a 31 bp sequence (+33 to +63 from the transcription start site) located downstream of a TATA box is also essential for the maximum expression of the MMV FLt promoter. Analysis of transcripts (mRNA) from these chimeric constructs also indicated that the MMV FLt promoter fragment (-297 to +63 from the transcription start site) has the highest promoter activity. In a comparative analysis the MMV FLt promoter showed much greater activity than the CaMV 35S promoter.

A simultaneous ex vivo model of embryogenesis: II. Vasculogenesis

Vasculogenesis was simultaneously studied with embryogenesis in in ovo chick embryo culture, which was harvested at 40 hours. Endodermal cells and vascular endothelial cells were studied using a new combination of stains, immunohistochemistry (for nuclei and basement membrane) and NADPH-diaphorase activity in whole-mounts, paraffin sections and etched semithin sections. The model can be used for the study of developmental process of blood vessels as well as embryonic physiology of blood vessels vis-a-vis organogenesis in response to different angiogenic agents, drug trials, cancer therapy by angiostatic chemicals/radiations and toxins. Considering that vasculogenesis/angiogenesis as one of the fundamental phenomena in physiology, pathophysiology, toxicology and pharmacology of developmental sciences, the model in developing embryo is presented.

The posttranslational modification of phosphoglucomutase is regulated by galactose induction and glucose repression in Saccharomyces cerevisiae

The enzyme phosphoglucomutase functions at a key point in carbohydrate metabolism. In this paper, we show that the synthesis of the major isoform of yeast phosphoglucomutase, encoded by the GAL5 (PGM2) gene, is regulated in a manner that is distinct from that previously described for other enzymes involved in galactose metabolism in the yeast Saccharomyces cerevisiae. Accumulation of this isoform increased four- to sixfold when the culture experienced either glucose depletion or heat shock. However, heat shock induction did not occur unless the cells were under glucose repression. This nonadditive increase in expression suggests that the regulatory mechanisms controlling the heat shock induction and glucose repression of the GAL5 gene are functionally related. We previously demonstrated that phosphoglucomutase is modified by a posttranslational Glc-phosphorylation reaction. We now show that this posttranslational modification, like phosphoglucomutase expression itself, is also regulated by galactose induction and glucose repression. Finally, no evidence was found to indicate that the Glc-phosphorylation of phosphoglucomutase alters its enzymatic activity under the conditions examined.

Characterisation of 2S albumin with nutritionally balanced aminoacid composition from the seeds of Chenopodium album and its antigenic homology with seed proteins of some Chenopodiaceae and Amaranthaceae species

The low molecular weight 2S albumin protein of Chenopodium album seeds has been isolated and characterized with respect to its subunit structure by SDS-PAGE and antigenic homology with low molecular weight seed storage proteins of several other phylogenetically related species by immunoprecipitation and Western blotting. These studies revealed the existence of antigenically homologous proteins of similar molecular weights in seeds of some other members of Chenopodiaceae and Amaranthaceae. However, Chenopodium 2S albumin is antigenically unrelated to low mol.wt. albumins of dicots belonging to other families. It has a nutritionally balanced aminoacid composition in respect of essential aminoacids.

Phosphoglucomutase in Saccharomyces cerevisiae is a cytoplasmic glycoprotein and the acceptor for a Glc-phosphotransferase

UDP-glucose:glycoprotein glucose-1-phosphotransferase (Glc-phosphotransferase) catalyzes the transfer of Glc-1-P from UDP-Glc to mannose residues on acceptor glycoproteins. The predominant acceptor in vertebrates and Paramecium tetraurelia is a cytoplasmic 62-kDa glycoprotein. To determine if the yeast Saccharomyces cerevisiae also possesses Glc-phosphotransferase activity, a crude cellular lysate was incubated with [beta-32P]UDP-Glc and analyzed. A phosphoglycoprotein having an apparent molecular mass of 62 kDa (pgp62) was found to be the predominant labeled macromolecule. Reconstitution experiments determined that both a soluble and membrane fraction were required for labeling, and suggested that the Glc-phosphotransferase is membrane-associated while pgp62 is cytoplasmic. The reaction is evolutionarily conserved to the extent that rat liver Glc-phosphotransferase was capable of recognizing the yeast acceptor and vice versa. The yeast 62-kDa acceptor was purified, and partial amino acid sequences showed a high level of identity with rabbit muscle phosphoglucomutase. Subsequently, both yeast and rabbit muscle phosphoglucomutase were found to be acceptors in the Glc-phosphotransferase reaction. The label was found on a tryptic peptide distinct from that containing the enzyme's active site serine. When phosphoglucomutase was overexpressed, an increase was seen in Glc-phosphotransferase acceptor activity and in specific metabolic labeling of the acceptor by glucose and mannose.

Maturation-dependent goat epididymal sperm autoagglutination and its inhibition by a glycoprotein factor

The maturing goat epididymal spermatozoa were isolated from different segments of epididymis and these cells dispersed in a modified Ringer's solution, were incubated at 37 degrees C for 60 min to evaluate their autoagglutination efficacy. Distal corpus-epididymal spermatozoa specifically showed high order of head-to-head autoagglutination property whereas all other sperm cells did not show any detectable aggregation. The goat epididymal plasma has been shown to possess an anti-agglutinin that markedly inhibits sperm agglutination phenomenon and also dissociates the cells from the sperm clusters. Epididymal plasma is the most potent source of the anti-agglutinin which is a heat-stable specific glycoprotein. Like the autoagglutination phenomenon, the initiation of sperm forward progression also starts in the distal-corpus epididymis. The temporal correlation of these two events suggests that sperm autoagglutination may be a prerequisite for the induction of flagellar motility during the epididymal maturity of male gametes.

A study of caesarean section cases with special reference to maternal and neonatal outcome

Two hundred cases of lower uterine segment caesarean section were studied in SSKM Hospital and IPGME&R, Calcutta (a referral hospital) during the period 1986-1987. All were unselected cases of which 192 were booked and 8 were unbooked. The maximum number of caesarean sections were done in the age group of 21-30 years ie, in 154 cases (77.00%). Of total number of cases 53.5% were primigravida, and rest were multipara. Postoperative complications were noted in 42 cases (21%). Complications were more in unbooked and emergency cases ie, 7 (87.5%) and also in cases of antepartum haemorrhage (3 out of 8 cases) and where foetal distress (12 out of 51 cases) ie, prolonged labour, difficult labour was present. Neonatal mortality and morbidity (8 and 26 out of 154 total births respectively) were high in the age group of 21-30 years. Neonatal complications following caesarean section were found in 21.8% patients in emergency caesarean section and 15.5% in elective caesarean section. Neonatal morbidity was 15% and perinatal mortality was 4% in this study. Asphyxia (11 cases) and respiratory distress syndrome (10 cases) were more dangerous complications in caesarean section. There was no maternal mortality in this series.

Heparin binding domain of antithrombin III: characterization using a synthetic peptide directed polyclonal antibody

Antithrombin III (ATIII) is a plasma-borne serine protease inhibitor that apparently forms covalent complexes with thrombin. The interaction between ATIII and thrombin is enhanced several thousandfold by the glycosaminoglycan, heparin. We have previously proposed that the heparin binding site of ATIII resides within a region extending from amino acid residues 114-156 [Smith, J. W., & Knauer, D. J. (1987) J. Biol. Chem. 262, 11964-11972]. Computer-assisted analysis of this region revealed the presence of a 22 amino acid domain (residues 124-145), part of which shows a strong potential for the formation of an amphipathic helix: hydrophobic on one face and highly positively charged on the other. In the presence studies, polyclonal antisera were generated against a synthetic peptide corresponding to residues 124-145 in native human ATIII. Affinity-purified IgG from these antisera, as well as monovalent Fab's derived from them, specifically blocked the binding of heparin to ATIII. Additionally, occupancy of the heparin binding site by these same monovalent and bivalent IgG's at least partially substituted for heparin, accelerating linkage formation between ATIII and thrombin. These results provide the first immunological evidence that region 124-145 is directly involved in the binding of heparin to ATIII and that an antibody-induced conformational change within this region can mediate ATIII activation.

Treatment of captive giant Canada geese affected by avian cholera

In the spring of 1975, an epornitic of avian cholera in Nebraska affected wild waterfowl, common crows (Corvus brachyrhynchos), and a captive flock of guant Canada geese (Branta canadensis maxima). Measures taken to control the disease in the captive geese included flushing the water of their pen with fresh well water, parenteral (50mg oxytetracycline intramuscularly) and feed (tetracycline 500 g/ton) antibiotic treatment, and removing dead waterfowl and crows from the pen, and keeping wild waterfowl and crows out of the pen. Other measures taken to prevent a recurrence of the outbreak included monitoring the area with susceptible sentinel birds and culturing nasal swabs for Pasteurella multocida. Young Canada geese and wood ducks (Aix sponsa) raised in the area also were cultured before release to assure that carriers would not be released into the wild. Presently, ponds in the pen have been dried up so that the area is less attractive to wild waterfowl. Swine feeders and waterers that have been modified to discourage their use by crows are being used to feed and water the geese.

An epornitic of avian cholera in waterfowl and common crows in Phelps County, Nebraska, in the spring, 1975

In the spring of 1975, many species of waterfowl and common crows (Corvus brachyrhynchos) were found dead in Phelps County, Nebraska. About 25,000 water fowl and at least 3,000 crows died in the epornitic. Few waterfowl were seen dying, but the crows experienced a chronic illness during which they became debilitated and were lethargic and dyspneic. Gross and microscopic lesions in the waterfowl were typical for acute avian cholera. The crows had dark, firm areas within the lungs, loosely adhered yellow fibrous material in the pericardial sac and air sacs and, occasionally, liver abscesses. Microscopically, focal purulent pneumonia was present and a fibrinopurulent exudate overlaid a granulomatous reaction on the heart and lung surfaces. Isolation of Pasteurella multocida serotype 1 confirmed the diagnosis of acute and chronic avian cholera in the waterfowl and crows, respectively.