Combinations with Allosteric SHP2 Inhibitor TNO155 to Block Receptor Tyrosine Kinase Signaling

PURPOSE

SHP2 inhibitors offer an appealing and novel approach to inhibit receptor tyrosine kinase (RTK) signaling, which is the oncogenic driver in many tumors or is frequently feedback activated in response to targeted therapies including RTK inhibitors and MAPK inhibitors. We seek to evaluate the efficacy and synergistic mechanisms of combinations with a novel SHP2 inhibitor, TNO155, to inform their clinical development.

EXPERIMENTAL DESIGN

The combinations of TNO155 with EGFR inhibitors (EGFRi), BRAFi, KRAS^G12Ci, CDK4/6i, and anti-programmed cell death-1 (PD-1) antibody were tested in appropriate cancer models in vitro and in vivo, and their effects on downstream signaling were examined.

RESULTS

In EGFR-mutant lung cancer models, combination benefit of TNO155 and the EGFRi nazartinib was observed, coincident with sustained ERK inhibition. In BRAF^V600E colorectal cancer models, TNO155 synergized with BRAF plus MEK inhibitors by blocking ERK feedback activation by different RTKs. In KRAS^G12C cancer cells, TNO155 effectively blocked the feedback activation of wild-type KRAS or other RAS isoforms induced by KRAS^G12Ci and greatly enhanced efficacy. In addition, TNO155 and the CDK4/6 inhibitor ribociclib showed combination benefit in a large panel of lung and colorectal cancer patient-derived xenografts, including those with KRAS mutations. Finally, TNO155 effectively inhibited RAS activation by colony-stimulating factor 1 receptor, which is critical for the maturation of immunosuppressive tumor-associated macrophages, and showed combination activity with anti-PD-1 antibody.

CONCLUSIONS

Our findings suggest TNO155 is an effective agent for blocking both tumor-promoting and immune-suppressive RTK signaling in RTK- and MAPK-driven cancers and their tumor microenvironment. Our data provide the rationale for evaluating these combinations clinically.

A Proof of Concept for Biomarker-Guided Targeted Therapy against Ovarian Cancer Based on Patient-Derived Tumor Xenografts

Advanced ovarian cancers are a leading cause of cancer-related death in women and are currently treated with surgery and chemotherapy. This standard of care is often temporarily successful but exhibits a high rate of relapse, after which, treatment options are few. Here we investigate whether biomarker-guided use of multiple targeted therapies, including small molecules and antibody-drug conjugates, is a viable alternative. A panel of patient-derived ovarian cancer xenografts (PDX), similar in genetics and chemotherapy responsiveness to human tumors, was exposed to 21 monotherapies and combination therapies. Three monotherapies and one combination were found to be active in different subsets of PDX. Analysis of gene expression data identified biomarkers associated with responsiveness to each of the three targeted therapies, none of which directly inhibits an oncogenic driver. While no single treatment had as high a response rate as chemotherapy, nearly 90% of PDXs were eligible for and responded to at least one biomarker-guided treatment, including tumors resistant to standard chemotherapy. The distribution of biomarker positivity in The Cancer Genome Atlas data suggests the potential for a similar precision approach in human patients. SIGNIFICANCE: This study exploits a panel of patient-derived xenografts to demonstrate that most ovarian tumors can be matched to effective biomarker-guided treatments.

Increased lysosomal biomass is responsible for the resistance of triple-negative breast cancers to CDK4/6 inhibition

Inhibitors of cyclin-dependent kinases CDK4 and CDK6 have been approved for treatment of hormone receptor-positive breast cancers. In contrast, triple-negative breast cancers (TNBCs) are resistant to CDK4/6 inhibition. Here, we demonstrate that a subset of TNBC critically requires CDK4/6 for proliferation, and yet, these TNBC are resistant to CDK4/6 inhibition due to sequestration of CDK4/6 inhibitors into tumor cell lysosomes. This sequestration is caused by enhanced lysosomal biogenesis and increased lysosomal numbers in TNBC cells. We developed new CDK4/6 inhibitor compounds that evade the lysosomal sequestration and are efficacious against resistant TNBC. We also show that coadministration of lysosomotropic or lysosome-destabilizing compounds (an antibiotic azithromycin, an antidepressant siramesine, an antimalaria compound chloroquine) renders resistant tumor cells sensitive to currently used CDK4/6 inhibitors. Lastly, coinhibition of CDK2 arrested proliferation of CDK4/6 inhibitor-resistant cells. These observations may extend the use of CDK4/6 inhibitors to TNBCs that are refractory to current anti-CDK4/6 therapies.

Correction: The potent and selective cyclin-dependent kinases 4 and 6 inhibitor ribociclib (LEE011) is a versatile combination partner in preclinical cancer models

[This corrects the article DOI: 10.18632/oncotarget.26215.].

Patient-derived glioblastoma cultures as a tool for small-molecule drug discovery

There is a compelling need for new therapeutic strategies for glioblastoma multiforme (GBM). Preclinical target and therapeutic discovery for GBMs is primarily conducted using cell lines grown in serum-containing media, such as U-87 MG, which do not reflect the gene expression profiles of tumors found in GBM patients. To address this lack of representative models, we sought to develop a panel of patient-derived GBM models and characterize their genomic features, using RNA sequencing (RNA-seq) and growth characteristics, both when grown as neurospheres in culture, and grown orthotopically as xenografts in mice. When we compared these with commonly used GBM cell lines in the Cancer Cell Line Encyclopedia (CCLE), we found these patient-derived models to have greater diversity in gene expression and to better correspond to GBMs directly sequenced from patient tumor samples. We also evaluated the potential of these models for targeted therapy, by using the genomic characterization to identify small molecules that inhibit the growth of distinct subsets of GBMs, paving the way for precision medicines for GBM.

Abstract 922: Preclinical anticancer activity of LSZ102, a novel oral selective estrogen receptor degrader targeting wild-type and mutant ER

Estrogen receptor (ER) blockade is a well-established therapeutic approach in ER+ breast cancer. A novel oral selective estrogen receptor degrader (SERD), LSZ102, is in development. LSZ102 induces proteasome-mediated degradation of both wild type and mutant ERα in MCF-7 cells. LSZ102 also inhibits transcription of ERα target genes and results in a decrease in cell proliferation in a dose dependent manner. Expression of ERα Y537S results in a shift in inhibition of cell proliferation upon incubation with either LSZ102 or fulvestrant; however, the shift with LSZ102 was less severe. Similarly, LSZ102 induced a more pronounced level of ERα degradation than fulvestrant in the Y537S mutant MCF7 cells. Overall, LSZ102 is effective in the wild type and Y537S ERα mutant setting in vitro. In vivo, LSZ102 treatment of ER+ breast cancer xenografts resulted in inhibition of ERα regulated transcripts and a decrease in ERα protein levels. In the MCF7 xenograft model, expression of ERα Y537S resulted in reduced activity by fulvestrant, but not by LSZ102. In vivo, LSZ102 exhibited single agent and combination efficacy upon co-administration with the CDK4/6 inhibitor ribociclib and the alpha-specific PI3K inhibitor alpelisib. LSZ102 is currently in a Phase I clinical trial in patients with ER+ breast cancer in which it is tested as a single agent, and in combination with either ribociclib or alpelisib.

Citation Format: L. Alex Gaither, Choi Lai Tiong Yip, Chunrong Wang, Weiyi Toy, Qing Sheng, Jinyun Chen, Yuji Mishina, Rita Das, Stefan Peukert, Alice Loo, Sarat Chandarlapaty, Adam Crystal, Tinya J. Abrams. Preclinical anticancer activity of LSZ102, a novel oral selective estrogen receptor degrader targeting wild-type and mutant ER [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 922.

Development and field testing of low-cost, quantal microbial assays with volunteer reporting as scalable means of drinking water safety estimation

AIMS

To evaluate a low-cost water quality test for at-scale drinking water safety estimation in rural India.

METHODS AND RESULTS

Within a longitudinal study to characterize variability in household drinking water safety in rural Maharashtra, we piloted a low-cost presence-absence (LCPA) microbial test designed to be used by volunteer residents in rural areas. In comparing the LCPA results with standard laboratory methods for enumeration of Escherichia coli, we found that LCPA tests using modified mTec media were highly sensitive in detecting drinking water of moderate risk (88% of tests were positive at E. coli counts of 11-100 CFU per 100 ml) and high risk (96% of tests were positive at E. coli counts of 101 + CFU per 100 ml). The LCPA tests demonstrated low specificity for E. coli specifically, due to concurrent detection of Klebsiella: 38% of LCPA tests were positive even when E. coli was not detected in a 100 ml sample by membrane filtration, suggesting the test would be conservative in risk estimation. We also found that 47% of participants in rural villages in India were willing to conduct tests and return results after a brief training, with 45% of active participants sending their water testing results via short message service.

CONCLUSIONS

Given their low cost (~US$0.50 as piloted) and open-source format, such tests may provide a compelling alternative to standard methods for rapid water quality assessments, especially in resource-limited settings.

SIGNIFICANCE AND IMPACT OF THE STUDY

The lack of availability of water quality data constrains efforts to monitor, evaluate and improve the safety of water and sanitation infrastructure in underserved settings. Current water testing methods are not scalable because of laboratory and cost constraints. Our findings indicate the LCPA or similar low-cost microbial tests could be useful in rapid water safety estimation, including via crowdsourcing.

The potent and selective cyclin-dependent kinases 4 and 6 inhibitor ribociclib (LEE011) is a versatile combination partner in preclinical cancer models

Inhibition of cyclin-dependent kinases 4 and 6 (CDK4/6) is associated with robust antitumor activity. Ribociclib (LEE011) is an orally bioavailable CDK4/6 inhibitor that is approved for the treatment of hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer, in combination with an aromatase inhibitor, and is currently being evaluated in several additional trials. Here, we report the preclinical profile of ribociclib. When tested across a large panel of kinase active site binding assays, ribociclib and palbociclib were highly selective for CDK4, while abemaciclib showed affinity to several other kinases. Both ribociclib and abemaciclib showed slightly higher potency in CDK4-dependent cells than in CDK6-dependent cells, while palbociclib did not show such a difference. Profiling CDK4/6 inhibitors in large-scale cancer cell line screens in vitro confirmed that RB1 loss of function is a negative predictor of sensitivity. We also found that routinely used cellular viability assays measuring adenosine triphosphate levels as a proxy for cell numbers underestimated the effects of CDK4/6 inhibition, which contrasts with assays that assess cell number more directly. Robust antitumor efficacy and combination benefit was detected when ribociclib was added to encorafenib, nazartinib, or endocrine therapies in patient-derived xenografts.

Abstract 682: Identification of HSP90 inhibitor sensitizers through pooled RNA interference screen

Key words: HSF1, cancer cells, HSP90 inhibitor, Melanoma, HCC, DEDD2.

The molecular chaperone heat shock protein 90 (HSP90) facilitates the appropriate folding of various oncogenic proteins and is necessary for the survival of some cancer cells. HSP90 is therefore an attractive drug target, but the efficacy of HSP90 inhibitor may be limited by HSP90 inhibition induced feedback mechanisms. To identify genes that modulate the efficacy of HSP90 inhibition on tumor cell growth, we performed a large-scale RNA interference (RNAi) genetic screen with a collection of short hairpin RNA (shRNA) vectors targeting 1,000 human genes in A375. A barcoding technique was used to identify genes whose suppression caused resistance or sensitivity to two separate concentrations of NVP-AUY922. 163 and 360 shRNA constructs were significantly depleted form either low- or high-dose NVP-AUY922 treated samples (FDR<=0.15). Among those shRNA hits, 84 hits (including 81 genes) were common shRNA hits as shown in Venn diagram and sensitizing genes or rescuing genes were also shown. Among of these shRNA hits, HSF1 and heat shock protein 90 alpha, class B member 1(HSP90AB1) knockdown scored as the most top sensitizers to HSP90 inhibition in A375 cells, and are known to regulate the cell response to heat shock conditions, which may reflect the potential feedback mechanism of HSP90 inhibition. Taking together, HSF1 is identified as a sensitizer of HSP90 inhibitor through pooled shRNA screening. A striking combinational effect was observed when HSF1 knockdown plus with HSP90 inhibitors treatment in various cancer cell lines: A375, A2058 and HCT116 and tumor mouse models. Interestingly, HSF1 is highly expressed in hepatocellular carcinoma (HCC) patient samples and HCC is sensitive to combinational treatment, indicating a potential indication for the combinational treatment. To understand the mechanism of the combinational effect, we identified that a HSF1-target gene DEDD2 is involved in attenuating the effect of HSP90 inhibitors. Thus, the transcriptional activities of HSF1 induced by HSP90 inhibitors provide a feedback mechanism of limiting the HSP90 inhibitor's activity, and targeting HSF1 may provide a new avenue to enhance HSP90 inhibitors activity in human cancers.

Citation Format: Yaoyu Chen, Jinyun Chen, Alice Loo, Margaret Mclaughlin, Raymond Pagliarini, Wenlai Zhou. Identification of HSP90 inhibitor sensitizers through pooled RNA interference screen. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 682. doi:10.1158/1538-7445.AM2014-682

Antiproliferative effects of CDK4/6 inhibition in CDK4-amplified human liposarcoma in vitro and in vivo

Well-differentiated/dedifferentiated liposarcomas (WD/DDLPS) are among the most common subtypes of soft tissue sarcomas. Conventional systemic chemotherapy has limited efficacy and novel therapeutic strategies are needed to achieve better outcomes for patients. The cyclin-dependent kinase 4 (CDK4) gene is highly amplified in more than 95% of WD/DDLPS. In this study, we explored the role of CDK4 and the effects of NVP-LEE011 (LEE011), a novel selective inhibitor of CDK4/CDK6, on a panel of human liposarcoma cell lines and primary tumor xenografts. We found that both CDK4 knockdown by siRNA and inhibition by LEE011 diminished retinoblastoma (RB) phosphorylation and dramatically decreased liposarcoma cell growth. Cell-cycle analysis demonstrated arrest at G0-G1. siRNA-mediated knockdown of RB rescued the inhibitory effects of LEE011, demonstrating that LEE011 decreased proliferation through RB. Oral administration of LEE011 to mice bearing human liposarcoma xenografts resulted in approximately 50% reduction in tumor (18)F-fluorodeoxyglucose uptake with decreased tumor biomarkers, including RB phosphorylation and bromodeoxyuridine incorporation in vivo. Continued treatment inhibited tumor growth or induced regression without detrimental effects on mouse weight. After prolonged continuous dosing, reestablishment of RB phosphorylation and cell-cycle progression was noted. These findings validate the critical role of CDK4 in maintaining liposarcoma proliferation through its ability to inactivate RB function, and suggest its potential function in the regulation of survival and metabolism of liposarcoma, supporting the rationale for clinical development of LEE011 for the treatment of WD/DDLPS.

Targeting HSF1 sensitizes cancer cells to HSP90 inhibition

The molecular chaperone heat shock protein 90 (HSP90) facilitates the appropriate folding of various oncogenic proteins and is necessary for the survival of some cancer cells. HSP90 is therefore an attractive drug target, but the efficacy of HSP90 inhibitor may be limited by HSP90 inhibition induced feedback mechanisms. Through pooled RNA interference screens, we identified that heat shock factor 1(HSF1) is a sensitizer of HSP90 inhibitor. A striking combinational effect was observed when HSF1 knockdown plus with HSP90 inhibitors treatment in various cancer cell lines and tumor mouse models. Interestingly, HSF1 is highly expressed in hepatocellular carcinoma (HCC) patient samples and HCC is sensitive to combinational treatment, indicating a potential indication for the combinational treatment. To understand the mechanism of the combinational effect, we identified that a HSF1-target gene DEDD2 is involved in attenuating the effect of HSP90 inhibitors. Thus, the transcriptional activities of HSF1 induced by HSP90 inhibitors provide a feedback mechanism of limiting the HSP90 inhibitor's activity, and targeting HSF1 may provide a new avenue to enhance HSP90 inhibitors activity in human cancers.

2-(N-Benzyl-N-phenylsulfonamido)alkyl amide derivatives as γ-secretase inhibitors

A series of (N-benzyl-N-phenylsulfonamido)alkyl amides were developed from classic and parallel synthesis strategies. Compounds with good in vitro and in vivo γ-secretase activity were identified and described.

Fragment-Based Discovery of 7-Azabenzimidazoles as Potent, Highly Selective, and Orally Active CDK4/6 Inhibitors

Herein, we describe the discovery of potent and highly selective inhibitors of both CDK4 and CDK6 via structure-guided optimization of a fragment-based screening hit. CDK6 X-ray crystallography and pharmacokinetic data steered efforts in identifying compound 6, which showed >1000-fold selectivity for CDK4 over CDKs 1 and 2 in an enzymatic assay. Furthermore, 6 demonstrated in vivo inhibition of pRb-phosphorylation and oral efficacy in a Jeko-1 mouse xenograft model.

Protein kinase C inhibitor sotrastaurin selectively inhibits the growth of CD79 mutant diffuse large B-cell lymphomas

The activated B-cell-like (ABC) subtype of diffuse large B-cell lymphoma (DLBCL) correlates with poor prognosis. The ABC subtype of DLBCL is associated with constitutive activation of the NF-κB pathway, and oncogenic lesions have been identified in its regulators, including CARD11/CARMA1 (caspase recruitment domain-containing protein 11), A20/TNFAIP3, and CD79A/B. In this study, we offer evidence of therapeutic potential for the selective PKC (protein kinase C) inhibitor sotrastaurin (STN) in preclinical models of DLBCL. A significant fraction of ABC DLBCL cell lines exhibited strong sensitivity to STN, and we found that the molecular nature of NF-κB pathway lesions predicted responsiveness. CD79A/B mutations correlated with STN sensitivity, whereas CARD11 mutations rendered ABC DLBCL cell lines insensitive. Growth inhibitory effects of PKC inhibition correlated with NF-κB pathway inhibition and were mediated by induction of G₁-phase cell-cycle arrest and/or cell death. We found that STN produced significant antitumor effects in a mouse xenograft model of CD79A/B-mutated DLBCL. Collectively, our findings offer a strong rationale for the clinical evaluation of STN in ABC DLBCL patients who harbor CD79 mutations also illustrating the necessity to stratify DLBCL patients according to their genetic abnormalities.

The Polycomb group protein Bmi-1 is essential for the growth of multiple myeloma cells

Bmi-1 is a member of the Polycomb group family of proteins that function in the epigenetic silencing of genes governing self-renewal, differentiation, and proliferation. Bmi-1 was first identified through its ability to accelerate c-Myc-induced lymphomagenesis. Subsequent studies have further supported an oncogenic role for Bmi-1 in several cancers including those of the breast, lung, prostate, and brain. Using a stable and inducible shRNA system to silence Bmi-1 gene expression, we show a novel role for Bmi-1 in regulating the growth and clonogenic capacity of multiple myeloma cells both in vitro and in vivo. Moreover, to elucidate novel gene targets controlled by Bmi-1, global transcriptional profiling studies were performed in the setting of induced loss of Bmi-1 function. We found that the expression of the proapoptotic gene Bim is negatively regulated by Bmi-1 and that Bim knockdown functionally rescues the apoptotic phenotype induced upon loss of Bmi-1. Therefore, these studies not only highlight Bmi-1 as a cancer-dependent factor in multiple myeloma, but also elucidate a novel antiapoptotic mechanism for Bmi-1 function involving the suppression of Bim.

The landscape of somatic copy-number alteration across human cancers

A powerful way to discover key genes playing causal roles in oncogenesis is to identify genomic regions that undergo frequent alteration in human cancers. Here, we report high-resolution analyses of somatic copy-number alterations (SCNAs) from 3131 cancer specimens, belonging largely to 26 histological types. We identify 158 regions of focal SCNA that are altered at significant frequency across multiple cancer types, of which 122 cannot be explained by the presence of a known cancer target gene located within these regions. Several gene families are enriched among these regions of focal SCNA, including the BCL2 family of apoptosis regulators and the NF-κB pathway. We show that cancer cells harboring amplifications surrounding the MCL1 and BCL2L1 anti-apoptotic genes depend upon expression of these genes for survival. Finally, we demonstrate that a large majority of SCNAs identified in individual cancer types are present in multiple cancer types.

Abstract B22: Dynamics of cancer cell survival dependency on Bcl-2 family members

Apoptosis is regulated through the interactions of the Bcl-2 family of proteins. Overexpression of anti-apoptotic Bcl-2 family members plays a key role in promoting survival for cells undergoing various insults that would normally trigger cell death. Consequently, these proteins are believed to serve as contributing factors to the processes of tumor initiation, tumor progression and the development of resistance to therapeutics. ABT-263, an antagonist of Bcl-2, Bcl-xL, and Bcl-w, is currently being tested in clinical trials. Some cancer cells express high amounts of Mcl-1, another Bcl-2 family anti-apoptotic protein that shares pro-survival function with Bcl-2 but is not targeted by ABT-263. Preclinical data indicates Mcl-1 overexpressing cells are not sensitive to ABT-263. To understand this mechanism of Mcl-1 dependence, A2058 melanoma cells were infected with a lentivirus encoding inducible shRNA against Mcl-1. Upon induction of MCL1 knockdown, massive cell death occurred. Interestingly, a small subset of the cell population managed to survive. Subsequent western blot analysis confirmed a sustained depletion of Mcl-1. Further study indicated A2058 cells deficient in Mcl-1 survived by upregulating expression of Bcl-2, a process we term “switching dependency”. In addition, these cells became sensitized to ABT-263 treatment. An A2058 xenograft model indicates that combined knockdown of both Mcl-1 and Bcl-2 significantly inhibited tumor growth when compared to tumors treated with ABT-263 lacking either protein individually. Real-time kinetic studies reveal a rapid sensitization of A2058 cells to ABT-263 upon sh-RNA induction. To understand whether de novo protein synthesis of Bcl-2 plays a mechanistic role in dependency switching, A2058 sh-Mcl-1 cells were treated with the protein synthesis inhibitor cycloheximide. Kinetic analysis indicates that de novo protein synthesis is not required for dependency switching. Real-time quantitative PCR was then employed to determine if a relationship exists between the decrease in Mcl-1 mRNA, and subsequent sensitivity to ABT-263, is a consequence of a change in Bcl-2 mRNA levels. Surprisingly, the results indicate as the loss of Mcl-1 message occurs, there is no concurrent change in Bcl-2 mRNA. Taken together these data indicate that dependency switching, and therefore survival, occurs without de novo Bcl-2 protein synthesis or alterations in protein turnover. Furthermore, dependency switching is a possible mechanism cancer cells employ to develop resistance toward various anti-cancer therapies with novel implications for both the concept of oncogene addiction and development of targeted cancer therapeutics. Therefore there is an immediate need for elucidation of this novel cancer resistance mechanism.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):B22.

PI3K pathway activation mediates resistance to MEK inhibitors in KRAS mutant cancers

The RAS pathway is one of the most frequently deregulated pathways in cancer. RAS signals through multiple effector pathways, including the RAF/mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) kinase (MEK)/ERK MAPK and phosphatidylinositol 3-kinase (PI3K)-AKT signaling cascades. The oncogenic potential of these effector pathways is illustrated by the frequent occurrence of activating mutations in BRAF and PIK3CA as well as loss-of-function mutations in the tumor suppressor PTEN, a negative regulator of PI3K. Previous studies have found that whereas BRAF mutant cancers are highly sensitive to MEK inhibition, RAS mutant cancers exhibit a more variable response. The molecular mechanisms responsible for this heterogeneous response remain unclear. In this study, we show that PI3K pathway activation strongly influences the sensitivity of RAS mutant cells to MEK inhibitors. Activating mutations in PIK3CA reduce the sensitivity to MEK inhibition, whereas PTEN mutations seem to cause complete resistance. We further show that down-regulation of PIK3CA resensitizes cells with co-occurring KRAS and PIK3CA mutations to MEK inhibition. At the molecular level, the dual inhibition of both pathways seems to be required for complete inhibition of the downstream mammalian target of rapamycin effector pathway and results in the induction of cell death. Finally, we show that whereas inactivation of either the MEK or PI3K pathway leads to partial tumor growth inhibition, targeted inhibition of both pathways is required to achieve tumor stasis. Our study provides molecular insights that help explain the heterogeneous response of KRAS mutant cancers to MEK pathway inhibition and presents a strong rationale for the clinical testing of combination MEK and PI3K targeted therapies.

Single-vector inducible lentiviral RNAi system for oncology target validation

The use of RNA interference (RNAi) has enabled loss-of-function studies in mammalian cancer cells and has hence become critical for identifying and validating cancer drug targets. Current transient siRNA and stable shRNA systems, however, have limited utility in accurately assessing the cancer dependency due to their short-lived effects and limited in vivo utility, respectively. In this study, a single-vector lentiviral, Tet-inducible shRNA system (pLKO-Tet-On) was generated to allow for the rapid generation of multiple stable cell lines with regulatable shRNA expression. We demonstrate the advantages and versatility of this system by targeting two polycomb group proteins, Bmi-1 and Mel-18, in a number of cancer cell lines. Our data show that pLKO-Tet-On-mediated knockdown is tightly regulated by the inducer tetracycline and its derivative, doxycycline, in a concentration- and time-dependent manner. Furthermore, target gene expression is fully restored upon withdrawal of the inducing agent. An additional, 17 distinct gene products have been targeted by inducible shRNAs with robust regulation in all cases. Importantly, we functionally validate the ability of the pLKO-Tet-On vector to reversibly silence targeted transcripts in vivo. The versatile and robust inducible lentiviral RNAi system reported herein can therefore serve as a powerful tool to rapidly reveal tumor cell dependence.

Amino-caprolactam derivatives as gamma-secretase inhibitors

A series of amino-caprolactam sulfonamides were developed from a screening hit. Compounds with good in vitro and in vivo gamma-secretase activity are reported.

Discovery of (S)-2-((S)-2-(3,5-difluorophenyl)-2-hydroxyacetamido)-N-((S,Z)-3-methyl-4-oxo-4,5-dihydro-3H-benzo[d][1,2]diazepin-5-yl)propanamide (BMS-433796): a gamma-secretase inhibitor with Abeta lowering activity in a transgenic mouse model of Alzheimer's disease

We report on the design of benzodiazepinones as peptidomimetics at the carboxy terminus of hydroxyamides. Structure-activity relationships of diazepinones were investigated and orally active gamma-secretase inhibitors were synthesized. Active metabolites contributing to Abeta reduction were identified by analysis of plasma samples from Tg2576 mice. In particular, (S)-2-((S)-2-(3,5-difluorophenyl)-2-hydroxyacetamido)-N-((S,Z)-3-methyl-4-oxo-4,5-dihydro-3H-benzo[d][1,2]diazepin-5-yl)propanamide (BMS-433796) was identified with an acceptable pharmacodynamic and pharmacokinetic profile. Chronic dosing of BMS-433796 in Tg2576 mice suggested a narrow therapeutic window and Notch-mediated toxicity at higher doses.

2,3-Benzodiazepin-1,4-diones as peptidomimetic inhibitors of gamma-secretase

2,3-Benzodiazepin-1,4-diones were designed as peptidomimetics at the carboxy terminus of hydroxyamides. Inhibition of brain Abeta production was improved by one of the compounds containing constrained modification.

Dynamics of {beta}-amyloid reductions in brain, cerebrospinal fluid, and plasma of {beta}-amyloid precursor protein transgenic mice treated with a {gamma}-secretase inhibitor

gamma-Secretase inhibitors are one promising approach to the development of a therapeutic for Alzheimer's disease (AD). gamma-Secretase inhibitors reduce brain beta-amyloid peptide (Abeta), which is believed to be a major contributor in the etiology of AD. Transgenic mice overexpressing the human beta-amyloid precursor protein (APP) are valuable models to examine the dynamics of Abeta changes with gamma-secretase inhibitors in plaque-free and plaque-bearing animals. BMS-299897 2-[(1R)-1-[[(4-chlorophenyl)sulfony](2,5-difluorophenyl)amino]ethyl]-5-fluorobenzenepropanoic acid, a gamma-secretase inhibitor, showed dose- and time dependent reductions of Abeta in brain, cerebrospinal fluid (CSF), and plasma in young transgenic mice, with a significant correlation between brain and CSF Abeta levels. Because CSF and brain interstitial fluid are distinct compartments in composition and location, this correlation could not be assumed. In contrast, aged transgenic mice with large accumulations of Abeta in plaques showed reductions in CSF Abeta in the absence of measurable changes in plaque Abeta in the brain after up to 2 weeks of treatment. Hence, CSF Abeta levels were a valuable measure of gamma-secretase activity in the central nervous system in either the presence or absence of plaques. Transgenic mice were also used to examine potential side effects due to Notch inhibition. BMS-299897 was 15-fold more effective at preventing the cleavage of APP than of Notch in vitro. No changes in the maturation of CD8(+) thymocytes or of intestinal goblet cells were observed in mice treated with BMS-299897, showing that it is possible for gamma-secretase inhibitors to reduce brain Abeta without causing Notch-mediated toxicity.

Longitudinal change in quality of life and impact on survival after left ventricular assist device implantation

BACKGROUND

The HeartMate vented electric left ventricular assist device has been approved for use as destination therapy. Thus, the study of quality-of-life outcomes, as well as morbidity and mortality, is imperative. The purpose of our study was to describe change with time (from 1 month to 1 year) in patients who received a HeartMate vented electric left ventricular assist device as a bridge to heart transplantation and to identify quality-of-life predictors of survival after left ventricular assist device implantation.

METHODS

A nonrandom sample of 78 patients who received a HeartMate vented electric left ventricular assist device (primarily middle-aged, white married males) who had quality-of-life data at 1, 2, 3, 6, 9, or 12 months after implant was the subject of this report. The sample size decreased with time primarily because of heart transplantation. Patients completed the following booklets of questionnaires: Quality of Life Index, Rating Question Form, Heart Failure Symptom Checklist, and Sickness Impact Profile. Analyses included both descriptive analyses and modeling procedures (mixed-effects models and Cox proportional hazards models).

RESULTS

Quality-of-life outcomes were fairly good and stable from 1 month to 1 year after HeartMate vented electric left ventricular assist device implantation. Both positive and negative changes were detected in all quality-of-life domains (physical and occupational function, social interaction, somatic sensation, and psychological state) after left ventricular assist device insertion. Items from the physical domain of quality of life, specifically walking and dressing oneself, were significantly associated with the risk of dying after left ventricular assist device implantation.

CONCLUSIONS

Identifying poor quality-of-life outcomes within 1 year after left ventricular assist device implantation provides direction to develop strategies to improve outcomes. Physical and occupational rehabilitation, psychosocial intervention, and monitoring symptom distress and physical disability may contribute to improved quality-of-life outcomes and survival after left ventricular assist device implantation.

Change in quality of life from after left ventricular assist device implantation to after heart transplantation

BACKGROUND

No studies have analyzed quality of life (QOL) from before to after heart transplantation in patients with a left ventricular assist device (LVAD). Therefore, the purpose of this longitudinal, multi-site study was to compare QOL outcomes of patients listed for heart transplantation who required a left ventricular assist device (LVAD) at 3 months after implantation of an LVAD vs 3 months after heart transplantation.

METHODS

A non-random sample of 40 patients (predominantly middle-aged, married, white men), who had paired data at both 3 months after LVAD implantation and 3 months after heart transplantation, were investigated. Patients completed self-report questionnaires (with acceptable reliability and validity) at both time periods, including the Quality of Life Index, Rating Question Form, Heart Failure Symptom Checklist, Sickness Impact Profile, LVAD Stressor Scale (completed only after LVAD implant), Heart Transplant Stressor Scale (completed only after heart transplant) and Jalowiec Coping Scale. Descriptive analyses and comparative analyses using paired t-tests were performed with statistical significance set at 0.01.

RESULTS

Patients were significantly more satisfied with their lives overall and with their health and functioning at 3 months after heart transplantation as compared with 3 months after LVAD implantation. Mobility, self-care ability, physical ability and overall functional ability improved from 3 months after LVAD implant to 3 months after heart transplant. There was significantly less symptom distress after LVAD implant as compared with after heart transplant for the neurologic, dermatologic and physical sub-scales. Work/school/financial stress was significantly lower after heart transplant vs after LVAD implant. In contrast, 2 other areas of stress were significantly lower after LVAD implant vs after heart transplant: self-care stress and hospital/clinic-related stress.

CONCLUSIONS

Differences were found in QOL outcomes at 3 months after LVAD implant as compared with 3 months after heart transplant. Our findings point out specific areas of concern with respect to QOL after LVAD implant and post-transplant, some of which are amenable to health-care provider interventions.

Change in quality of life from before to after discharge following left ventricular assist device implantation

BACKGROUND

Quality of life (QOL) outcomes after left ventricular assist device (LVAD) implantation from before to after hospital discharge have been examined only in a very small sample of patients. The purposes of this study are to describe change in QOL from before to after hospital discharge in LVAD patients and to determine whether being discharged with an LVAD predicts better QOL than being hospitalized with an LVAD.

METHODS

A non-random sample of 62 LVAD patients (approximately 50 years old, male, white, married, fairly well-educated) completed self-report questionnaires at >or=2 timepoints post-implant. The questionnaires (Quality of Life Index, Rating Question Form, Heart Failure Symptom Checklist, Sickness Impact Profile, LVAD Stressor Scale, Jalowiec Coping Scale), which were collated into booklets, had acceptable reliability and validity. Longitudinal analyses were performed in 2 steps using 1-sample t-tests and linear mixed effects modeling.

RESULTS

Perception of QOL and health status were fairly good both before and after discharge of LVAD patients. Discharge predicted increased satisfaction with socioeconomic areas of life; decreased overall and psychologic stress and stress related to family and friends, self-care and work/school/finances; and decreased physical and self-care disability.

CONCLUSIONS

QOL outcomes improved from before to after hospital discharge in LVAD patients awaiting heart transplantation. As LVADs potentially become available as destination therapy, in addition to being successful bridges to heart transplantation, QOL outcomes will become more important to study.

Predictors of Quality of Life at 1 Month After Implantation of a Left Ventricular Assist Device

• Objectives To describe quality-of-life outcomes; determine relationships between quality of life and demographic, physical, psychosocial, and clinical variables; and identify predictors of quality of life at 1 month after implantation of a left ventricular assist device.

• Methods Patients who received either an implantable pneumatic (n = 38) or a vented electric (n = 54) left ventricular assist device as a bridge to heart transplantation between August 1, 1994, and August 31, 1999, completed 6 instruments used to measure quality of life and factors related to quality of life. Data were analyzed by using descriptive statistics, Pearson correlations, Mann-Whitney U tests, and forward, stepwise multiple regression.

• Results Overall satisfaction with quality of life was quite high as determined from the total score on the Quality of Life Index (mean = 0.69). Patients were very satisfied with the implantation and thought that they would do well after future heart transplant surgery. Patients had a moderate level of stress. Significant predictors of overall quality of life were psychological symptoms, stress, and race; these accounted for 46% of variance in quality of life.

• Conclusions Patients were satisfied with their quality of life at 1 month after implantation of a left ventricular assist device. However, they were least satisfied with their health and functioning and yet were optimistic about how well they thought they would do after heart transplantation. Psychological factors were the strongest predictors of satisfaction with overall quality of life.

Predictors of quality of life at 1 month after implantation of a left ventricular assist device

OBJECTIVES

To describe quality-of-life outcomes; determine relationships between quality of life and demographic, physical, psychosocial, and clinical variables; and identify predictors of quality of life at 1 month after implantation of a left ventricular assist device.

METHODS

Patients who received either an implantable pneumatic (n = 38) or a vented electric (n = 54) left ventricular assist device as a bridge to heart transplantation between August 1, 1994, and August 31, 1999, completed 6 instruments used to measure quality of life andfactors related to quality of life. Data were analyzed by using descriptive statistics, Pearson correlations, Mann-Whitney U tests, and forward, stepwise multiple regression.

RESULTS

Overall satisfaction with quality of life was quite high as determined from the total score on the Quality of Life Index (mean = 0.69). Patients were very satisfied with the implantation and thought that they would do well after future heart transplant surgery. Patients had a moderate level of stress. Significant predictors of overall quality of life were psychological symptoms, stress, and race; these accounted for 46% of variance in quality of life.

CONCLUSIONS

Patients were satisfied with their quality of life at 1 month after implantation of a left ventricular assist device. However, they were least satisfied with their health and functioning and yet were optimistic about how well they thought they would do after heart transplantation. Psychological factors were the strongest predictors of satisfaction with overall quality of life.

Preoperative latanoprost to prevent ocular hypertension after phacoemulsification and intraocular lens implantation

PURPOSE

To evaluate the efficacy of latanoprost given 2 hours preoperatively to prevent ocular hypertension in the early period after phacoemulsification and posterior chamber intraocular lens (PC IOL) implantation.

SETTING

Departments of Ophthalmology, United Christian Hospital and Prince of Wales Hospital, Hong Kong, China.

METHODS

Sixty-four eyes of 64 patients with uncomplicated cataract having phacoemulsification with PC IOL implantation were included in this prospective randomized double-masked clinical trial. The eyes were randomly assigned to 1 of 2 groups: application of latanoprost 0.005% 2 hours before surgery or no latanoprost (control). Intraocular pressure (IOP) was measured 3 and 24 hours postoperatively. The anterior chamber was examined for the level of cells and flare using a slitlamp biomicroscope. The level of significance was 5%.

RESULTS

The decrease in the mean IOP was not statistically significantly different between eyes receiving latanoprost 2 hours preoperatively and control eyes 3 hours (P =.843) and 24 hours (P =.721) postoperatively.

CONCLUSION

A single application of latanoprost given 2 hours before phacoemulsification and PC IOL implantation did not produce a statistically significant IOP-lowering effect when compared with a control group in the first 24 hours after surgery.

Pars plana vitrectomy with silicone oil in the management of combined rhegmatogenous retinal and choroidal detachment

PURPOSE

Rhegmatogenous retinal detachment combined with spontaneous pre-operative choroidal detachment (RDCD) represents a rare but specific entity, which has in the past been associated with a poor prognosis. This study was designed to determine the efficacy of pars plana vitrectomy with silicone oil injection in the management of this very difficult vitreoretinal problem.

METHODS

A retrospective analysis was carried out of 13 eyes of 13 consecutive patients who underwent vitrectomy and silicone oil exchange.

RESULTS

In a total of 10 eyes (77%) the first procedure produced anatomical success. Two eyes required a further procedure to achieve retinal reattachment, producing a final anatomical success rate of 92%.

CONCLUSION

Pars plana vitrectomy with silicone oil exchange is an effective technique for managing RDCD.

Effect of intracameral acetylcholine on latanoprost in preventing ocular hypertension after phacoemulsification and intraocular lens implantation

PURPOSE

To evaluate the effect of intracameral acetylcholine on latanoprost in preventing ocular hypertension in the early period after phacoemulsification with posterior chamber intraocular lens (PC IOL) implantation.

SETTING

Department of Ophthalmology and Visual Sciences, Prince of Wales Hospital, Shatin, Hong Kong, China.

METHODS

Patients with uncomplicated cataract having phacoemulsification with PC IOL implantation were included in this prospective randomized double-masked clinical trial. The eyes were randomly assigned to 1 of 4 groups based on postoperative application of latanoprost 0.005% alone (Group 1), latanoprost 0.005% with intracameral acetylcholine (Group 2), intracameral acetylcholine alone (Group 3), and no medication (controls (Group 4). Intraocular pressure (IOP) was measured 3 and 24 hours postoperatively. The anterior chamber was examined for the level of cells and flare using slitlamp biomicroscopy.

RESULTS

Three and 24 hours after surgery, the decrease in mean IOP in eyes receiving latanoprost alone was not statistically significantly different from that in control eyes (P >.05). Eyes receiving intracameral acetylcholine alone had a significant decrease in the mean IOP at 3 hours (P <.05) but not at 24 hours compared to control eyes (P >.05). There were no significant differences in the mean postoperative IOP decrease between eyes receiving latanoprost with intracameral acetylcholine and those receiving intracameral acetylcholine alone (P >.05).

CONCLUSIONS

A single application of latanoprost did not significantly lower IOP in the first 24 hours after phacoemulsification with PC IOL implantation. Eyes receiving intracameral acetylcholine alone had a significantly greater decrease in IOP than control eyes at 3 hours but not at 24 hours. The addition of intracameral acetylcholine to latanoprost did not enhance or reduce latanoprost's IOP-lowering effect.

Dietary nucleotides augment dextran sulfate sodium-induced distal colitis in rats

We have previously shown that enteral and parenteral supplementation of nucleotides (NT) accelerates healing of small-bowel ulcers in rats with indomethacin-induced ileitis. The purpose of this study was to evaluate whether dietary NT supplementation would similarly affect ulcer healing in dextran sulfate sodium (DSS)-induced colitis in rats. Male Sprague-Dawley rats were randomly assigned to receive either nucleotide-free (NF) or NT-supplemented diets. After 2 d of prefeeding, colitis was induced by including 40 g/L of DSS in drinking water for 3 d, followed thereafter by tap water. Rats from each group were killed at 7 and 12 d after induction of colitis. Additional rats were also used for both the groups as controls (untreated groups). The length of colon was measured and evaluated by histological score. Colonic myeloperoxidase (MPO) activity was assessed. In a separate series of experiments, rats were studied at 0, 4, 7, and 12 d for interleukin-1beta (IL-1beta) in rectal dialysate and plasma. Ulceration predominated in the distal colon in DSS-treated rats. There was no significant difference between the histological scores of the NF and NT-supplemented groups either at 7 or 12 d. MPO activity at 7 and 12 d was significantly higher in the NT-supplemented compared to NF group (7 d: 1013 +/- 172 vs. 409.9 +/- 103.2; 12 d: 471.9 +/- 112.4 vs. 223.6 +/- 21.6 units. min-1. g colon-1). IL-1beta concentration in rectal dialysate was significantly higher at 7 d in both groups compared to 0 and 4 d. At 12 d it continued to be significantly elevated in the NT-supplemented group and was greater than in the NT-free group. Our data on the proinflammatory cytokine, in conjunction with MPO activity, strongly suggest that NT supplementation aggravates the severity of DSS-induced colitis in rats.

Expression and characterization of protein kinase C in isolated rabbit parietal cells

We investigated the expression, characterization and distribution of protein kinase C (PKC) isozymes in isolated rabbit parietal cells (PC). Cellular extracts of PC were analyzed by Western blot using isozyme-specific antibodies. The Ca2+-independent PKC-epsilon was detected in cytosolic, membrane and cytoskeletal fractions of basal and histamine-stimulated PC, whereas the Ca2+-dependent PKC-alpha was confined to the cytosolic and membrane fractions. Cytosolic and membrane fractions were partially purified by DEAE cellulose column chromatography with elution of increasing NaCl concentration. Eluates of 0.15 M and 0.3 M NaCl PC fractions were identified as PKC-alpha and -epsilon isoforms, respectively. Phorbol 12-myristate 13-acetate (TPA) treatment of PC for 15, 30 and 60 sec decreased significantly cytosolic PKC-alpha and increased membrane-associated PKC-alpha. In contrast to the distribution of PKC-alpha, TPA did not alter membrane or cytosolic level of PKC-epsilon. Comparison of the dose-response curves between TPA-induced hydrogen (H+) secretion, as measured by aminopyrine (AP) uptake, and the membrane-associated PKC-alpha suggests that translocation of PKC-alpha is not involved in the H+ secretory process in PC. Furthermore, a PKC inhibitor, staurosporine, produced a concentration-dependent enhancement of histamine-stimulated H+ secretion. These findings suggest that PKC-alpha plays a negative modulatory role, rather than an obligatory role, in H+ secretion. The localization and distribution of PKC-epsilon into the cytoskeletal fraction of PC also suggests that this isozyme may be involved in the cellular regulation of reversible morphological transformation during stimulation.

Dietary supplementation of nucleotides and arginine promotes healing of small bowel ulcers in experimental ulcerative ileitis

We previously showed that intravenous total parenteral nutrition supplemented with nucleosides and nucleotides (NS/NT) promoted ulcer healing in rats with indomethacin-induced ileitis. The present study evaluated whether dietary NT supplementation would similarly affect ulcer healing in this model. Female Lewis rats were randomized into either control or experimental groups receiving yeast RNA containing NT or arginine, glutamine, fish oil, guar gum, or a combination of yeast RNA+arginine diets. Ileitis was induced by two doses of indomethacin (7.5 mg/kg) administered subcutaneously 24 hr apart. Ulcer number and length were determined at 4, 8, and 14 days after induction of ileitis. Ileal villous and crypt length, crypt-villous ratio, and bromodeoxyuridine (BrdU) labeling were studied in the control and yeast RNA-supplemented diet groups. Ileal ulceration was present in all groups at 4 and 8 days and was almost healed by 14 days. Rats receiving yeast RNA, arginine, and yeast RNA + arginine diets showed a significant decrease in ulcer number (56%, 28%, and 34%, respectively) and length (67%, 41%, and 48%, respectively) compared to controls at 8 but not at 4 days. Glutamine, fish oil, and guar gum had no effect on ulcer healing at 4, 8, or 14 days. Among the histological parameters, a significant decrease in crypt length in the yeast RNA-supplemented group at 8 days suggested an acceleration of the healing process and restoration to a near-normal crypt-villous architecture. We conclude that the yeast RNA, arginine, and yeast RNA + arginine diets accelerated ulcer healing, as indicated by decreased ulcer number and length. We postulate that the underlying mechanism(s) contributing to ulcer healing may be related, in part, to increased cell proliferation.

Anomalous serum thyroxin measurements with the Abbott TDx procedure

We describe a patient whose serum gave consistently low results for thyroxin as measured with the Abbott TDx but normal results by radioimmunoassay. Further clinical and laboratory studies did not support the low TDx results. Anti-thyroxin antibodies did not explain the discordant results, and we found no evidence of heterophilic antibodies in the patient's serum. We were unable to identify the cause of the problem.

Anomalous serum thyroxin measurements with the Abbott TDx procedure

We describe a patient whose serum gave consistently low results for thyroxin as measured with the Abbott TDx but normal results by radioimmunoassay. Further clinical and laboratory studies did not support the low TDx results. Anti-thyroxin antibodies did not explain the discordant results, and we found no evidence of heterophilic antibodies in the patient's serum. We were unable to identify the cause of the problem.