Effect of age, ethnicity, sex, cognitive status and APOE genotype on amyloid load and the threshold for amyloid positivity

The threshold for amyloid positivity by visual assessment on PET has been validated by comparison to amyloid load measured histopathologically and biochemically at post mortem. As such, it is now feasible to use qualitative visual assessment of amyloid positivity as an in-vivo gold standard to determine those factors which can modify the quantitative threshold for amyloid positivity. We calculated quantitative amyloid load, measured as Standardized Uptake Value Ratios (SUVRs) using [18-F]florbetaben PET scans, for 159 Hispanic and non-Hispanic participants, who had been classified clinically as Cognitively Normal (CN), Mild Cognitive Impairment (MCI) or Dementia (DEM). PET scans were visually rated as amyloid positive (A+) or negative (A-), and these judgments were used as the gold standard with which to determine (using ROC analyses) the SUVR threshold for amyloid positivity considering factors such as age, ethnicity (Hispanic versus non-Hispanic), gender, cognitive status, and apolipoprotein E ε4 carrier status. Visually rated scans were A+ for 11% of CN, 39.0% of MCI and 70% of DEM participants. The optimal SUVR threshold for A+ among all participants was 1.42 (sensitivity = 94%; specificity = 92.5%), but this quantitative threshold was higher among E4 carriers (SUVR = 1.52) than non-carriers (SUVR = 1.31). While mean SUVRs did not differ between Hispanic and non-Hispanic participants;, a statistically significant interaction term indicated that the effect of E4 carrier status on amyloid load was greater among non-Hispanics than Hispanics. Visual assessment, as the gold standard for A+, facilitates determination of the effects of various factors on quantitative thresholds for amyloid positivity. A continuous relationship was found between amyloid load and global cognitive scores, suggesting that any calculated threshold for the whole group, or a subgroup, is artefactual and that the lowest calculated threshold may be optimal for the purposes of early diagnosis and intervention.

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Demographic factors did not affect the threshold for amyloid positivity.

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Cognitive status did not affect this threshold for amyloid positivity.

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APOE4 carriers had a higher threshold for amyloid positivity than non-carriers.

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Among APOE4 carriers, non-Hispanics had higher amyloid load than non- Hispanics.

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There was a continuous relationship between amyloid load and cognitive status.

Abstract P6-22-01: Repurposing sulindac sulfide as a notch inhibitor to target cancer stem-like cells in triple negative breast cancer

Triple negative breast cancer (TNBC) is a heterogeneous group of clinically aggressive breast cancers. TNBC patients have a high risk of recurrence and metastasis, and current treatment options remain limited. There is strong evidence supporting the involvement of Notch signaling in TNBC progression. Expression of Notch1 and its ligand Jagged1 correlate with poor prognosis. Emerging evidence suggests that cancer stem-like cells (CSCs) that escape chemo or radiation therapy in TNBC are often Notch-dependent. At the same time, there is evidence that active tumor immunity predicts good response to neo-adjuvant chemotherapy in TNBC. Notch inhibitors, including Gamma Secretase Inhibitors (GSIs) are quite effective in preclinical models of TNBC, where they eliminate CSCs resistant to chemotherapy. However, the success of GSIs in clinical trials is limited by their intestinal toxicity and adverse immunological effects. CD4 and CD8 T-cells, necessary to adaptive tumor immunity, require Notch1 for activation. Our overarching goal is to replace GSIs with agents that lack their systemic toxicity and adverse immunological effects. We identified Sulindac Sulfide (SS), the active metabolite of FDA-approved NSAID Sulindac, as a potential candidate to replace GSI. SS has Gamma Secretase Modifier (GSM) activity. We confirmed that SS inhibits Notch1 cleavage in TNBC cells. SS significantly inhibited mammosphere growth in all human and murine TNBC models we tested: 1) human MDA-MB-231 cells; 2) murine TNBC model C0321, from targeted conditional knockout of Lunatic Fringe (LFng-/-); and 3) Two TNBC patient-derived xenograft models, 2K1 and 4IC. In contrast, SS did not inhibit Notch expression or cleavage in murine T cells. In C0321 tumors, which recapitulate human mesenchymal TNBC, we found that SS had remarkable single-agent anti-tumor activity and virtually eliminated Notch1 expression in tumors. SS caused an increase in intra-tumoral CD11c+ dendritic cells, but decreased CD4 cells, which in this model are largely PD-1 positive (exhausted). CD8 cells were modestly increased. SS did not affect the number of tumor infiltrating macrophages or myeloid-derived suppressor cells (MDSC). However, SS blocked the immunosuppressive function of bone marrow-derived MDSC. We are currently investigating the mechanisms of this anti-tumor activity. Our data support further investigation of SS for the treatment of TNBC, with standard of care or with immunotherapy agents. Repurposing an FDA-approved, safe agent for the treatment of TNBC would be significantly easier and more cost-effective than developing unproven investigational agents.

Citation Format: Hossain F, Ucar D, Majumder S, Xu K, Ran Y, Minter L, Xi Y, Burow M, Golde T, Osborne B, Miele L. Repurposing sulindac sulfide as a notch inhibitor to target cancer stem-like cells in triple negative breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-22-01.

Abstract P6-07-06: Targeting cancer stem-like cells metabolism via non-canonical notch signaling pathways in triple negative breast cancer

Triple negative breast cancer (TNBC) is a heterogeneous group of clinically aggressive diseases. TNBC patients have high risk of recurrence and metastasis, and current treatment options remain limited. Cancer stem-like cells (CSCs) have been linked to cancer initiation, progression and chemotherapy resistance. Therefore CSC-targeted therapies are keenly sought. There is strong evidence for the involvement of Notch signaling in TNBC. Notch1 is highly expressed in Basal-like 1 (BL1) and especially Mesenchymal-Stem-Like (MSL) TNBCs. Expression of Notch1 and its ligand Jagged1 correlate with poor prognosis. Moreover, strong evidence supports key roles of different Notch paralogs in breast CSCs. Here, we demonstrate that Notch activation by Jagged1-expressing stromal cells enhances transcription of the anti-apoptotic gene cIAP-2 (BIRC3), a known NF-κB target. This event is dependent on recruitment to the cIAP-2 promoter of NF-κB subunits, IKKα and Notch1. Short term exposure of MDA-MB-231 cells (MSL, PTEN wild-type), but not MDA-MB-468 cells (BL1, PTEN-null) to recombinant Jagged1 leads to AKT phosphorylation. This is suppressed by AKT inhibitors, IKK inhibitors, and dual mTORC1/2 inhibitors but not an mTORC1-selective inhibitor. These observations support a model where canonical and non-canonical mechanisms downstream of Notch1 trigger AKT phosphorylation and NF-κB activation in PTEN wild type TNBC cells. Rapid AKT phosphorylation downstream of Notch1 requires mTORC2, PI3K and IKKα, and contributes to NF-κB activation. This suggests a bidirectional crosstalk between the IKKα and AKT arms of this Jagged1-activated pathway. Importantly, we find co-localization of Notch1 with Mitochondria in MDA-MB-231 cells by confocal microscopy and Western blot of isolated mitochondrial fractions. We demonstrate that recombinant Jagged1 increases metabolism of TNBC cells. Knockdown of Notch1 or IKKα by siRNA decreases mitochondrial respiration and glycolysis. CSCs derived from MDA-MB-231 cells have increased Notch1, p-AKT, and oxidative metabolism compared to non-stem cells. AKT inhibition or IKK inhibition decreases both mitochondrial respiration and glycolysis of TNBC derived CSCs. Pharmacological inhibition of Notch cleavage by gamma secretase inhibitor (PF-03084014) in combination with AKT inhibitor (MK-2206) or IKK inhibitor (Bay11-7082) blocks CD90hi or CD44+CD24low sorted secondary mammospheres formation. Notably, we find similar results in TNBC patient derived xenograft (PDX) models. These data suggest that combination treatments affecting the intersection of Notch, NF-kB and AKT pathways have potential therapeutic importance in targeting CSCs in TNBC cases with high Notch1 expression.

Citation Format: Hossain F, Sorrentino C, Ucar Bilyeu AD, Matossian M, Crabtree J, Pannuti A, Burow M, Golde T, Osborne B, Miele L. Targeting cancer stem-like cells metabolism via non-canonical notch signaling pathways in triple negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-07-06.

Abstract P5-07-06: A novel non-canonical Notch1-IKKα-mTORC2-AKT pathway maintains survival in triple negative breast cancer cells and cancer stem-like cells

Triple negative breast cancer (TNBC) is a heterogeneous group of clinically aggressive breast cancers. TNBC patients have high risk of recurrence and metastasis, and current treatment options remain limited. There is strong evidence for the involvement of Notch signaling in TNBC and in breast cancer stem-like cells (CSCs). Notch1 is highly expressed in Basal-like 1 (BL1) and especially Mesenchymal-Stem-Like (MSL) TNBCs. Expression of Notch1 and its ligand Jagged1 correlate with poor prognosis. Treatment of TNBC with dual mTORC1/2 inhibitors leads to resistance through activation of Notch1. Expression of Notch1 protein correlates with pAKT and nuclear NF-κB in TNBC. Here, we demonstrate that Notch1 promotes cell survival in MDA-MB-231 cells, representative of MSL TNBC, in part by activating NF-κB. Notch activation by Jagged1-expressing stromal cells enhances transcription of the anti-apoptotic gene cIAP-2 (BIRC3), a known NF-κB target. This event is dependent on recruitment to the cIAP-2 promoter of NF-κB subunits, IKKα and Notch1. Short term exposure of MDA-MB-231 cells (MSL, PTEN wild-type), but not MDA-MB-468 cells (BL1, PTEN-null) to recombinant Jagged1 leads to rapid AKT phosphorylation. This is suppressed by dual mTORC1/2 inhibitors, AKT inhibitors and IKKα inhibitors but not Everolimus (mTORC1-selective inhibitor). Rapid AKT phosphorylation downstream of Notch1 requires mTORC2, PI3K and IKKα, and contributes to NF-κB activation. These observations support a model where canonical and non-canonical mechanisms downstream of Notch1 trigger rapid AKT phosphorylation and NF-κB activation in PTEN wild-type TNBC cells. Both arms of this pathway require IKKα. CSCs derived from MDA-MB-231 cells have increased Notch1, pAKT and pIKKα expression. Combined pharmacological inhibition of Notch and AKT or Notch and IKKα completely blocks secondary mammosphere formation. These data and published literature suggest that: 1) IKKα connects the Notch and mTORC2/AKT pathways in some TNBC subtypes; 2) IKKα is also required for nuclear Notch1-mediated NF-kB activation and may be a critical node in the Notch signaling network; 3) A feedback mechanism may exist in some TNBC cells between mTORC2/AKT and Notch1; 4) The non-canonical Notch-IKKα-AKT pathway has a potential therapeutic role in targeting CSCs of selected TNBC subtypes.

Citation Format: Hossain F, Peng Y, Pannuti A, Backus K, Golde T, Osborne B, Miele L. A novel non-canonical Notch1-IKKα-mTORC2-AKT pathway maintains survival in triple negative breast cancer cells and cancer stem-like cells [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-07-06.

Rational targeting of Notch signaling in cancer

Accumulating preclinical and clinical evidence supports a pro-oncogenic function for Notch signaling in several solid tumors, particularly but not exclusively in breast cancer. Notch inhibitory agents, such as gamma-secretase inhibitors, are being investigated as candidate cancer therapeutic agents. Interest in therapeutic modulation of the Notch pathway has been increased by recent reports, indicating that its role is important in controlling the fate of putative 'breast cancer stem cells'. However, as is the case for most targeted therapies, successful targeting of Notch signaling in cancer will require a considerable refinement of our understanding of the regulation of this pathway and its effects in both normal and cancer cells. Notch signaling has bidirectional 'cross talk' interaction with multiple other pathways that include candidate therapeutic targets. Understanding these interactions will greatly increase our ability to design rational combination regimens. To determine which patients are most likely to benefit from treatment with Notch inhibitors, it will be necessary to develop molecular tests to accurately measure pathway activity in specific tumors. Finally, mechanism-based toxicities will have to be addressed by a careful choice of therapeutic agents, combinations and regimens. This article summarizes the current state of the field, and briefly describes opportunities and challenges for Notch-targeted therapies in oncology.

Familial frontotemporal dementia associated with a novel presenilin-1 mutation

We report a kindred with three cases of dementia. The proband presented with forgetfulness and personality changes at age 56, followed shortly thereafter by behavioral dyscontrol, hyperphagia, hypersexuality, delusions, illusions, disinhibition and double incontinence. Neuroimaging studies were consistent with frontotemporal dementia (FTD). In one allele, an arginine insertion at codon 352 in the presenilin 1 (PSEN1) gene was identified; no mutation was identified in the amyloid precursor protein or tau genes. We conclude that the clinical features of the Kluver-Bucy syndrome and FTD can be associated with PSEN1 mutations. Furthermore, presenilin analyses may be helpful to characterize kindreds with familial dementing illnesses regardless of the phenotype, particularly if no tau mutation is present.

beta-Secretase cleavage of the amyloid precursor protein mediates neuronal apoptosis caused by familial Alzheimer's disease mutations

The amyloid precursor protein (APP) is cleaved by two enzymes, beta-secretase and gamma-secretase, to generate the pathological amyloid beta (Abeta) peptide. Expression of familial Alzheimer's disease (FAD) mutants of APP in primary neurons causes both intracellular accumulation of the C-terminal beta-secretase cleavage product of APP and increased secretion of Abeta, and eventually results in apoptotic death of the cells. To determine whether either of these two processing products of APP is involved in this apoptotic pathway, we first modeled experimentally the accumulation of the beta-secretase cleavage product in neurons. The C-terminal 100 amino acids (C100) of APP, with and without a signal peptide, was expressed in cells via recombinant herpes simplex virus (HSV) vectors. Both transgene products were targeted to the membrane, and both caused apoptosis in the neurons, implicating the beta-secretase cleavage product of APP in apoptosis caused by FAD APPs. Expression in neurons of a mutant of FAD APP that inhibited beta-secretase cleavage inhibited its ability to cause apoptosis. However, expression in neurons of a mutant of FAD APP that inhibited gamma-secretase cleavage did not inhibit the ability of this mutant to cause apoptosis. These data suggested that the C-terminal beta-secretase cleavage product of APP, but not Abeta, mediates the apoptosis caused by FAD mutants of APP. Consistent with this hypothesis, C31, which is generated from the beta-secretase cleavage product, itself caused neuronal apoptosis. Inhibitors of caspases 3, 6 and 8, but not of caspase 9, inhibited the apoptosis caused by FAD mutants of APP. It may be inferred from these data that beta-secretase cleavage of FAD mutants of APP allows the appropriate caspase access to its site of action to produce C31, which directly causes neuronal apoptosis.

A novel gamma -secretase assay based on detection of the putative C-terminal fragment-gamma of amyloid beta protein precursor

Alzheimer's disease is characterized by the deposits of the 4-kDa amyloid beta peptide (A beta). The A beta protein precursor (APP) is cleaved by beta-secretase to generate a C-terminal fragment, CTF beta, which in turn is cleaved by gamma-secretase to generate A beta. Alternative cleavage of the APP by alpha-secretase at A beta 16/17 generates the C-terminal fragment, CTFalpha. In addition to A beta, endoproteolytic cleavage of CTF alpha and CTF beta by gamma-secretase should yield a C-terminal fragment of 57-59 residues (CTF gamma). However, CTF gamma has not yet been reported in either brain or cell lysates, presumably due to its instability in vivo. We detected the in vitro generation of A beta as well as an approximately 6-kDa fragment from guinea pig brain membranes. We have provided biochemical and pharmacological evidence that this 6-kDa fragment is the elusive CTF gamma, and we describe an in vitro assay for gamma-secretase activity. The fragment migrates with a synthetic peptide corresponding to the 57-residue CTF gamma fragment. Three compounds previously identified as gamma-secretase inhibitors, pepstatin-A, MG132, and a substrate-based difluoroketone (t-butoxycarbonyl-Val-Ile-(S)-4-amino-3-oxo-2, 2-difluoropentanoyl-Val-Ile-OMe), reduced the yield of CTF gamma, providing additional evidence that the fragment arises from gamma-secretase cleavage. Consistent with reports that presenilins are the elusive gamma-secretases, subcellular fractionation studies showed that presenilin-1, CTF alpha, and CTF beta are enriched in the CTF gamma-generating fractions. The in vitro gamma-secretase assay described here will be useful for the detailed characterization of the enzyme and to screen for gamma-secretase inhibitors.

Variant Alzheimer's disease with spastic paraparesis and cotton wool plaques is caused by PS-1 mutations that lead to exceptionally high amyloid-beta concentrations

We describe 3 new families affected by Alzheimer's disease with spastic paraparesis. In affected individuals, including the earliest known patient with this clinical syndrome, neuropathological examination revealed large "cotton wool" plaques similar to those we have previously described in a Finnish family. In the families in which DNA was available, presenilin-1 mutations were observed. Transfection of cells with these mutant genes caused exceptionally large increases in secreted Abeta42 levels. Furthermore, brain tissue from individuals with this syndrome had very high amyloid-beta concentrations. These findings define the molecular pathogenesis of an important subgroup of Alzheimer's disease and have implications for the pathogenesis of the disease in general.

A novel, non-nested reverse-transcriptase polymerase chain reaction (RT-PCR) test for the detection of the t(15;17) translocation: a comparative study of RT-PCR cytogenetics, and fluorescence In situ hybridization

BACKGROUND

The development of a rapid and simple reverse-transcription polymerase chain reaction (RT-PCR) assay is described that identifies the promyelocytic leukemia- retinoic acid receptor alpha (PML-RARa) hybrid messenger RNA (mRNA), a characteristic feature of acute promyelocytic leukemia (APL).

METHODS AND RESULTS

Randomly primed complementary (cDNA) is synthesized from leukocyte RNA and amplified in the presence of Taq Gold in 2 separate reaction tubes containing primer pairs specific for intron 3 (bcr 3, long [L] form mRNA transcript) and intron 6 (bcr 1, short [S] form)/exon 6 (bcr 2, variant [V] form) breakpoints in PML, respectively. The different sized products generated from each RNA transcript (S, L, or V forms) are readily and unambiguously distinguishable after agarose gel electrophoresis without the need for either nested PCR or hybridization. The sensitivity of the assay is 1 in 10,000 to 1 in 100,000. The separate amplification of a b2-microglobulin transcript controls for adequate RNA and cDNA preparation. The newly developed assay was used clinically for the evaluation of 78 patients with APL. It was rapid and more sensitive than cytogenetic karyotyping, both for the diagnosis of APL and the assessment of minimal residual disease (MRD) after therapy. RT-PCR detected PML-RARa mRNA in all cases positive for the t(15;17) translocation by cytogenetics. However, as many as 50% and 80% of the diagnostic specimens and the specimens for MRD assessment, respectively, that were positive by RT-PCR were negative by cytogenetics. The ratio of cases with L-form to S-form PML-RARa fusion transcript was 2:1, whereas 3 cases (10%) had fusion sites in exon 6 of the PML gene (V forms). In addition, approximately 50% of the patients were diagnosed morphologically with microgranular M3V-type leukemia, but no significant correlation with PML breakpoints was found.

CONCLUSION

The current assay is rapid, sensitive, and specific without using nested PCR or hybridization.

Serine protease inhibitor antithrombin III and its messenger RNA in the pathogenesis of Alzheimer's disease

The classical plasma protein antithrombin III (ATIII), an inhibitor of the blood coagulation cascade, is a member of the serpins that are gaining import in the nervous system. In this study, we examined the presence of ATIII in the pathological lesions of Alzheimer's disease (AD). Antibodies to ATIII consistently detected approximately 58-kd protein(s) on immunoblots of cerebral cortex and brain microvessels. Immunocytochemical studies showed ATIII reactivity within amyloid deposits, neurites associated with plaques, and neurofibrillary tangles in neocortex and hippocampus of virtually all the AD cases examined. In some cases, astrocytes were also stained, suggesting ATIII in these cells. ATIII immunoreactivity in neurofibrillary tangles was further defined by electron microscopy, which showed it to be associated with paired helical filaments. Using the polymerase chain reaction technique to amplify ATIII complementary DNA, we found low levels of messenger RNA expression, relative to liver, in control human brain samples, and these were increased in AD samples, particularly in the white matter. Our results suggest the increased presence of ATIII commensurate with astrogliosis and association with the neurofibrillary pathology of AD. We conclude that in concert with other amyloid-associated serine protease inhibitors, ATIII may play a role in the pathogenesis of cerebral amyloidosis.