The Sin3A/MAD1 Complex, through Its PAH2 Domain, Acts as a Second Repressor of Retinoic Acid Receptor Beta Expression in Breast Cancer Cells

Retinoids are essential in balancing proliferation, differentiation and apoptosis, and they exert their effects through retinoic acid receptors (RARs) and retinoid X receptors (RXRs). RARβ is a tumor-suppressor gene silenced by epigenetic mechanisms such as DNA methylation in breast, cervical and non-small cell lung cancers. An increased expression of RARβ has been associated with improved breast cancer-specific survival. The PAH2 domain of the scaffold protein SIN3A interacts with the specific Sin3 Interaction Domain (SID) of several transcription factors, such as MAD1, bringing chromatin-modifying proteins such as histone deacetylases, and it targets chromatin for specific modifications. Previously, we have established that blocking the PAH2-mediated Sin3A interaction with SID-containing proteins using SID peptides or small molecule inhibitors (SMI) increased RARβ expression and induced retinoic acid metabolism in breast cancer cells, both in in vitro and in vivo models. Here, we report studies designed to understand the mechanistic basis of RARβ induction and function. Using human breast cancer cells transfected with MAD1 SID or treated with the MAD SID peptide, we observed a dissociation of MAD1, RARα and RARβ from Sin3A in a coimmunoprecipitation assay. This was associated with increased RARα and RARβ expression and function by a luciferase assay, which was enhanced by the addition of AM580, a specific RARα agonist; EMSA showed that MAD1 binds to E-Box, similar to MYC, on the RARβ promoter, which showed a reduced enrichment of Sin3A and HDAC1 by ChIP and was required for the AM580-enhanced RARβ activation in MAD1/SID cells. These data suggest that the Sin3A/HDAC1/2 complex co-operates with the classical repressors in regulating RARβ expression. These data suggest that SIN3A/MAD1 acts as a second RARβ repressor and may be involved in fine-tuning retinoid sensitivity.

Invasive phenotype in triple negative breast cancer is inhibited by blocking SIN3A-PF1 interaction through KLF9 mediated repression of ITGA6 and ITGB1

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We show that the PAH2 domain of SIN3A is a target when it is inhibited from binding to PF1 results in inhibition of invasive phenotype in TNBC.

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Epigenetic repression of integrins expression and downstream pathways results from enhanced binding of KLF9 /SIN3A repressor complex to their promoters.

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Genome wide transcriptomic analysis showed downregulation of multiple invasion related genes. Tumor growth and lung metastasis were markedly decreased in vivo.

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Our studies highlight that PF1 might serve as a gatekeeper for trafficking SID protein binding to PAH2 of SIN3A and has functional role in presentation of different regulatory complexes.

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Blocking the function of PAH2 offers a promising targeted therapy approach for inhibiting the invasive phenotype in TNBC.

SIN3A, a scaffold protein has regulatory functions in tumor biology. Through its Paired amphipathic helix (PAH2) domain, SIN3A interacts with PHF12 (PF1), a protein with SIN3 interaction domain (SID) that forms a complex with MRG15 and KDM5A/B. These components are often overexpressed in cancer. In the present study, we evaluated the role of SIN3A and its interacting partner PF1 in mediating inhibition of tumor growth and invasion in triple negative breast cancer (TNBC). We found profound inhibition of invasion, migration, and induction of cellular senescence by specific disruption of the PF1/SIN3A PAH2 domain interaction in TNBC cells expressing PF1-SID transcript or peptide treatment. Genome-wide transcriptomic analysis by RNA-seq revealed that PF1-SID downregulates several gene sets and pathways linked to invasion and migration. Integrin α6 (ITGA6) and integrin ß1 (ITGB1) and their downstream target proteins were downregulated in PF1-SID cells. We further determined increased presence of SIN3A and transcriptional repressor, KLF9, on promoters of ITGA6 and ITGB1 in PF1-SID cells. Knockdown of KLF9 leads to re-expression of ITGA6 and ITGB1 and restoration of the invasive phenotype, functionally linking KLF9 to this process. Overall, these data demonstrate that specific disruption of PF1/SIN3A, inhibits tumor growth, migration, and invasion. Also, PF1-SID not only inhibits tumor growth by senescence induction and reduced proliferation, but it also targets cancer stem cell gene expression and blocks mammosphere formation. Overall, these data demonstrate a mechanism whereby invasion and metastasis of TNBC can be suppressed by inhibiting SIN3A-PF1 interaction and enhancing KLF9 mediated suppression of ITGA6 and ITGB1.

Clinical outcomes in COVID-19 patients with in-hospital cardiac arrest – an insight from multi-centre data

Background

In general, rates of in-hospital cardiac arrest are reportedly 9 to 10 arrests per 1000 admissions, with survival rates of approximately 20–25%. Data regarding clinical characteristics and outcomes in patients with COVID-19 who received in-hospital CPR (cardiopulmonary resuscitation) are limited. This information can help guide end-of-life care conversations between families and health care workers based on real-world experience.

Purpose

To observe the outcomes (survival to discharged alive from the hospital) in critically sick COVID-19 patients who experienced in-hospital cardiac arrest.

Methods

This is a multi-centre institutional review board (IRB) approved retrospective study. The RT-PCR confirmed adult COVID-19 patients consecutively admitted from March 1st to April 30, 2020, were included. Data were extracted manually using the hospital's electronic medical record. The final date of follow-up to monitor clinical outcomes was January 2021.

Results

A total of 721 patients were admitted to the hospital. Of these, only 64 (8.87%) patients had “no CPR” orders.Cardiac arrest occurred in 141 (19.5%) patients. The mean duration of beginning of resuscitation was less than a minute and the mean duration of CPR was 19 minutes. The median age was 65 years; 62.4% were male. The most common co-morbidities were hypertension (66%) and diabetes mellitus (56%). The initial rhythm was non-shockable in 93.7% of patients [asystole in 48.4% and Pulseless Electrical Activity (PEA) in 45.3% of patients]. Only six (4.2%) patients had pulseless ventricular tachycardia and three (2.1%) patients had ventricular fibrillation. A total of eight patients (5.6%) survived and were discharged from the hospital; six (4.25%) had non-shockable and two (0.82%) had shockable initial rhythms. The median age of those who survived was 60 years (Figure 1).

Conclusions

Our study showed that critically sick patients with COVID-19 have a high rate of cardiac arrest and poor outcomes in those who received CPR. A non-shockable initial rhythm indicates that non-cardiac reasons might be playing a major role. These include acute respiratory insufficiency, severe sepsis, or multiorgan failure. These data should inform end-of-life care discussions between providers and patients' families.

Funding Acknowledgement

Type of funding sources: None.

Cancer mortality in the elderly in 11 countries worldwide, 1970-2015

BACKGROUND

Population ageing results in an increasing cancer burden in the elderly. We aimed to evaluate time-trends in cancer mortality for adults aged 65 and over for 17 major cancer types and all cancers combined in 11 countries worldwide over the period 1970-2015.

MATERIALS AND METHODS

We obtained cancer death certification and population figures from the WHO and PAHO databases. We computed age-standardised (world standard population) rates for individuals aged 65 and over, and applied joinpoint regression models.

RESULTS

Age-standardised mortality rates for all cancers combined showed a heterogeneous, but widespread decline. Lung cancer mortality rates have been decreasing among men, and increasing among women. Pancreatic cancer had unfavourable trends in all countries for both sexes. Despite variability across countries, other tobacco-related cancers (except kidney) showed overall favourable trends, except in Poland and Russia. Age-standardised mortality rates from stomach cancer have been declining in all countries for both sexes. Colorectal mortality has been declining, except in Poland and Russia. Liver cancer mortality increased in all countries, except in Japan, France and Italy, which had the highest rates in the past. Breast cancer mortality decreased for most countries, except for Japan, Poland and Russia. Trends for age-standardised uterine cancer rates in the USA, Canada and the UK were increasing over the last decade. Ovarian cancer rates showed declines in most countries. With the exception of Russia, prostate cancer rates showed overall declines. Lymphoid neoplasms rates have been declining in both sexes, except in Poland and Russia.

CONCLUSION

Over the last decades, age-standardised cancer mortality in the elderly has been decreasing in major countries worldwide and for major cancer sites, with the major exception of lung and uterine cancer in women and liver, pancreatic and kidney cancers in both sexes. Cancer mortality for the elderly in central and eastern Europe remains comparatively high.

Abstract 31: Targeted dissociation of PF1 from SIN3A chromatin regulator complex inhibits tumor growth and metastasis in triple-negative breast cancer

Triple negative breast cancer (TNBC) is characterized by an aggressive, poorly differentiated phenotype associated with early recurrence. Chemotherapy is the only treatment option due to the lack of an effective molecular target. Targeting reversible epigenetic alterations in TNBC to reprogram the TNBC phenotype may increase chemosensitivity and identify effective targeted therapies. The SIN3 chromatin modifier complex is a multidomain scaffold protein which plays a key role in multiple cellular functions including epigenetic gene expression regulation, making SIN3 a potential therapeutic target. The PAH-2 domain of SIN3 binds with different affinities to a group of proteins that contain variations of an amino acid sequence known as the SIN3 interaction domain (SID). We previously reported the effects of blocking PAH-2 interaction with MAD-1, a SID sequence containing protein by using SID peptides and small molecule inhibitors (SMI) as decoys. We now report the effects of blocking the PAH-2 binding of PF1 and TGIF1, two other Sin3 interacting proteins with different amino acid sequence and PAH-2 binding affinities. Treatment with MAD-1 SID peptide and SMI revert the epithelial to mesenchymal transition (EMT) process, inhibit cancer stem cells expansion, cell invasion, tumor growth and metastasis development in human and mouse models of TNBC. TGIF1 interaction with SIN3 is associated with the invasive phenotype and EMT regulation by modulating wnt signaling and inhibiting beta catenin nuclear localization which is reverted by TGIF1 knockdown. PF1, which binds MRG15 and KDM5A/B, an epigenetic modifier, is involved in the regulation of cancer stem cell compartment expansion, DNA damage control, senescence, apoptosis and the expression of genes involved in metastatic progression. Interestingly, decrease in H3K4me3 is found in stem cell and EMT genes following 72 hour SID peptide treatment. PF1 dissociation from Sin3 by transfecting MDA-MB-231 and 4T1 cells with a PF1-SID expressing vector grown in 3D morphogenesis cultures display the formation of small organoids in the MDA-MB-231PF1-SID and tubular morphogenesis in the 4T1PF1-SID cells. There is increased activated caspase-3 and γH2AX, reduced Ki67, tenascin-C and marked cortical actin reorganization. This is accompanied by small organized colonies with loss of invasive and proliferative phenotype. In vivo, 4T1PF1-SID barely form tumors and have a 95% decrease in lung metastasis. These results show that decoys can be designed to block specific proteins that bind to the PAH-2 domain resulting in different outcomes which contribute to a common effect on inhibition of tumor progression and metastasis dissemination. Therefore, this strategy opens a potential therapeutic alternative for TNBC patients for whom there are no other therapeutic options besides chemotherapy.

Citation Format: Rama Kadamb, Nidhi Bansal, Boris A Leibovitch, Yeon-Jin Kwon, Ming-Ming Zhou, Eduardo Farias, Samuel Waxman. Targeted dissociation of PF1 from SIN3A chromatin regulator complex inhibits tumor growth and metastasis in triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 31.

Arsenic Trioxide and Sorafenib Induce Synthetic Lethality of FLT3-ITD Acute Myeloid Leukemia Cells

Acute myeloid leukemia (AML) with Fms-related tyrosine kinase 3 internal tandem duplication (FLT3-ITD) mutation is notoriously hard to treat. We identified two drugs that together form an effective combination therapy against FLT3-ITD AML. One of the drugs, Sorafenib, an inhibitor of FLT3-ITD and other kinase activity, produces an impressive but short-lived remission in FLT3-ITD AML patients. The second, arsenic trioxide (ATO), at therapeutically achievable concentrations, reduces the level of FLT3-ITD and Mcl-1 proteins, and induces apoptosis in leukemic cell lines and in primary cells expressing FLT3-ITD. We linked this relative sensitivity to ATO to low levels of reduced glutathione. While producing proapoptotic effects, ATO treatment also has an unwanted effect whereby it causes the accumulation of the phosphorylated (inactive) form of glycogen synthase kinase 3β (GSK3β), a kinase necessary for apoptosis. When ATO is combined with Sorafenib, GSK3β is activated, Mcl-1 is further reduced, and proapoptotic proteins Bak and Bax are activated. Mice xenografted with FLT3-ITD MOLM13 cell line treated with the Sorafenib/ATO combination have significantly improved survival. This combination has potential to improve the therapeutic outcome of FLT3-ITD-targeted therapy of AML patients. Mol Cancer Ther; 17(9); 1871-80. ©2018 AACR.

Blocking the PAH2 domain of Sin3A inhibits tumorigenesis and confers retinoid sensitivity in triple negative breast cancer

Triple negative breast cancer (TNBC) frequently relapses locally, regionally or as systemic metastases. Development of targeted therapy that offers significant survival benefit in TNBC is an unmet clinical need. We have previously reported that blocking interactions between PAH2 domain of chromatin regulator Sin3A and the Sin3 interaction domain (SID) containing proteins by SID decoys result in EMT reversal, and re-expression of genes associated with differentiation. Here we report a novel and therapeutically relevant combinatorial use of SID decoys. SID decoys activate RARα/β pathways that are enhanced in combination with RARα-selective agonist AM80 to induce morphogenesis and inhibit tumorsphere formation. These findings correlate with inhibition of mammary hyperplasia and a significant increase in tumor-free survival in MMTV-Myc oncomice treated with a small molecule mimetic of SID (C16). Further, in two well-established mouse TNBC models we show that treatment with C16-AM80 combination has marked anti-tumor effects, prevents lung metastases and seeding of tumor cells to bone marrow. This correlated to a remarkable 100% increase in disease-free survival with a possibility of "cure" in mice bearing a TNBC-like tumor. Targeting Sin3A by C16 alone or in combination with AM80 may thus be a promising adjuvant therapy for treating or preventing metastatic TNBC.

Identification of an Immune-specific Class of Hepatocellular Carcinoma, Based on Molecular Features

BACKGROUND & AIMS

Agents that induce an immune response against tumors by altering T-cell regulation have increased survival times of patients with advanced-stage tumors, such as melanoma or lung cancer. We aimed to characterize molecular features of immune cells that infiltrate hepatocellular carcinomas (HCCs) to determine whether these types of agents might be effective against liver tumors.

METHODS

We analyzed HCC samples from 956 patients. We separated gene expression profiles from tumor, stromal, and immune cells using a non-negative matrix factorization algorithm. We then analyzed the gene expression pattern of inflammatory cells in HCC tumor samples. We correlated expression patterns with the presence of immune cell infiltrates and immune regulatory molecules, determined by pathology and immunohistochemical analyses, in a training set of 228 HCC samples. We validated the correlation in a validation set of 728 tumor samples. Using data from 190 tumors in the Cancer Genome Atlas, we correlated immune cell gene expression profiles with numbers of chromosomal aberrations (based on single-nucleotide polymorphism array) and mutations (exome sequence data).

RESULTS

We found approximately 25% of HCCs to have markers of an inflammatory response, with high expression levels of the CD274 molecule (programmed death-ligand 1) and programmed cell death 1, markers of cytolytic activity, and fewer chromosomal aberrations. We called this group of tumors the Immune class. It contained 2 subtypes, characterized by markers of an adaptive T-cell response or exhausted immune response. The exhausted immune response subclass expressed many genes regulated by transforming growth factor beta 1 that mediate immunosuppression. We did not observe any differences in numbers of mutations or expression of tumor antigens between the immune-specific class and other HCCs.

CONCLUSIONS

In an analysis of HCC samples from 956 patients, we found almost 25% to express markers of an inflammatory response. We identified 2 subclasses, characterized by adaptive or exhausted immune responses. These findings indicate that some HCCs might be susceptible to therapeutic agents designed to block the regulatory pathways in T cells, such as programmed death-ligand 1, programmed cell death 1, or transforming growth factor beta 1 inhibitors.

Abstract 2083: Development of novel targeted adjuvant therapy for triple negative breast cancer

There is an unmet clinical need for targeted adjuvant therapy in Triple Negative Breast Cancer (TNBC) to overcome its poor prognosis, short disease-free interval and metastatic dissemination. We previously reported that blocking interactions between the PAH2 domain of chromatin regulator Sin3 and Sin3 interaction domain (SID) containing proteins like PF1 and TGIF1 by SID decoys (peptides and small molecule, C16) decreased the cancer stem cell population, invasion, EMT, and metastases. This, programmed upregulation of retinoid signaling that sensitized TNBC cells to AM80, a novel clinically available RARα-specific agonist. Here we report preclinical investigations on effects of SID decoys and AM80 treatments on cellular heterogeneity, primary tumors, metastatic dissemination, minimum residual disease (MRD) and host microenvironment. Using CyTOF2, we made single cell measurements of markers of differentiation, proliferation and stemness in CSC-enriched 4T1 tumorspheres. Treatment with SID peptide decreased cell populations expressing nanog, sox2, vimentin and β-catenin with increase in γH2AX. Addition of AM80 in combination with C16, resulted in populations with increased expression of differentiation marker CD24 with decrease in vimentin, β-catenin and Ki-67. To interrogate the neo-adjuvant effects of C16-AM80 treatments, primary 4T1 tumors in Balb/c mice were treated with C16 and AM80 alone or in combination. Compared to DMSO, ~40 % decrease in tumor weight, 60% decrease in ALDH activity and 60% decrease in lung metastasis was seen in mice treated with C16-AM80 combination. In post-surgical adjuvant settings, in both 4T1 and MMTV-myc xenografts, we observed 100% disease-free survival and absence of macrometastasis in mice receiving minimally toxic adjuvant therapy with the C16-AM80 combination for 90 days. However, MRD was found consisting of a small number of single CK8+ cells which failed to form colonies when recovered from the bone marrow and selectively cultured in vitro. Upon stopping the treatments, 20-40% animals developed macrometastases within the first three months. To test the influence of C16-AM80 to condition the host microenvironment to prevent macrometastases mice received only pretreatment with C16 and AM80 followed by 4T1 cells injected in the tail vein. The percentage of parenchyma occupied by metastatic nodules were: DMSO = 50%; AM80 = 25%; C16 >10% and C16-AM = <<10%; the mitotic features were greatly reduce from 0-5 in DMSO to 0-1 per 400x/field in the C16-AM80 combination. The predominant effects were observed with C16 treatment, which was enhanced to a small degree in combination with AM80. These results suggest that C16 can potentially induce changes in the host microenvironment to prevent the colonization and metastatic growth of cancer cells in TNBC. Altogether, our preclinical studies merit expansion of a pre-clinical program for development of C16-AM80 combination as a targeted adjuvant therapy to treat TNBC.

Citation Format: Nidhi Bansal, Eduardo Farias, Veronica Gonzalez, Garry Nolan, Samuel Waxman. Development of novel targeted adjuvant therapy for triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2083. doi:10.1158/1538-7445.AM2017-2083

Abstract 2936: Molecular characterization of the immune subclass of hepatocellualr carcinoma

Background: Immune checkpoint inhibitors have emerged as a promising therapeutic approach in different solid tumors, including hepatocellular carcinoma (HCC). Nonetheless, little is known about the immune-component of HCC or potential biomarkers of response to these therapies.

Aims: To perform comprehensive characterization of the HCC immunological profile and to identify biomarkers to select immunotherapy candidates.

Methods: We performed gene expression array deconvolution through non-negative matrix factorization in 228 resected HCCs. Characterization of the transcriptional landscape was conducted using >1,000 signatures representing distinct immune cells by gene set enrichment and nearest template prediction analyses. Presence of immune infiltration, tertiary lymphoid structure (TLS), PD-1 and PD-L1 immunostainings was investigated using immunohistochemistry. DNA methylation profile of 450K CpG sites was analyzed to identify those with significant differences for each group. Extensive validation of the immune classifier was performed in 728 independent HCC samples.

Results: Overall, an immune-related subclass of HCC was identified in ~27% of patients. The immune subclass was characterized by gene signatures identifying immune cells (i.e. T cells, TLS, cytotox, p<0.001), signatures of response to immune checkpoint therapy (p<0.001), presence of high immune infiltration (p=0.01), TLS (≥5 foci, 19/51 vs 33/168, p=0.01) and PD-1 and PD-L1 protein expression (p<0.05). The methylation levels of 363 CpG sites in 192 immune response gene promoters were able to capture the Immune class (ANOVA, p<0.05, Δβ>0.2 Tukey test). Integration with HCC molecular classifications revealed significant enrichment of the Immune subclass with IFN and S1 (p<0.001) and exclusion of the CTNNB1 and S2 (p<0.001) subclasses. The immune class contains two distinct microenvironment-based types: A) Exhausted immune response type (~35%) characterized by stromal activation, T cell exhaustion signatures, and presence of immunosuppressive components such as TGFB, LGALS1, M2 macrophages and pathways able to recruit myeloid-derived-suppressor cells (FDR<0.01); and B) Active immune response type (~65%) characterized by overexpression of adaptive immune response genes and IFN signaling (p<0.001). Tumors within the active immune response type showed a trend towards better survival vs rest (p=0.07).

Conclusions: Around 27% of HCC patients belong to the Immune class, characterized by activation of immune cells and signatures of response to immunotherapies. Within this subclass, two distinct types have been characterized by presenting active or exhausted immune responses, a feature that provides the rationale for precision medicine-based therapies.

Note: This abstract was not presented at the meeting.

Citation Format: Daniela Sia, Yang Jiao, Iris Martinez, Olga Kuchuk, Carlos Villacorta Martin, Manuel Castro de Moura, Juan Putra, Genis Camprecios, Swan Thung, Samuel Waxman, Vincenzo Mazzaferro, Manel Esteller, Augusto Villanueva, Josep Maria Llovet. Molecular characterization of the immune subclass of hepatocellualr carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2936. doi:10.1158/1538-7445.AM2017-2936

Targeting the SIN3A-PF1 interaction inhibits epithelial to mesenchymal transition and maintenance of a stem cell phenotype in triple negative breast cancer

Triple negative breast cancer (TNBC) is characterized by a poorly differentiated phenotype and limited treatment options. Aberrant epigenetics in this subtype represent a potential therapeutic opportunity, but a better understanding of the mechanisms contributing to the TNBC pathogenesis is required. The SIN3 molecular scaffold performs a critical role in multiple cellular processes, including epigenetic regulation, and has been identified as a potential therapeutic target. Using a competitive peptide corresponding to the SIN3 interaction domain of MAD (Tat-SID), we investigated the functional consequences of selectively blocking the paired amphipathic α-helix (PAH2) domain of SIN3. Here, we report the identification of the SID-containing adaptor PF1 as a factor required for maintenance of the TNBC stem cell phenotype and epithelial-to-mesenchymal transition (EMT). Tat-SID peptide blocked the interaction between SIN3A and PF1, leading to epigenetic modulation and transcriptional downregulation of TNBC stem cell and EMT markers. Importantly, Tat-SID treatment also led to a reduction in primary tumor growth and disseminated metastatic disease in vivo. In support of these findings, knockdown of PF1 expression phenocopied treatment with Tat-SID both in vitro and in vivo. These results demonstrate a critical role for a complex containing SIN3A and PF1 in TNBC and provide a rational for its therapeutic targeting.

Targeted interference of SIN3A-TGIF1 function by SID decoy treatment inhibits Wnt signaling and invasion in triple negative breast cancer cells

Cancer cell invasion is an obligatory step for metastatic dissemination that contributes to rapid relapse and a poorer survival in triple negative breast cancer (TNBC) patients. Development of novel therapeutic strategies to block tumor invasion is an unmet need in the treatment of cancer. We reported that the selective inhibition of the PAH2 domain of SIN3A protein function markedly suppressed metastatic dissemination to the lungs in TNBC xenograft bearing mice. Here, we show that TNBC cell lines treated with Sin3 interaction domain (SID) decoy peptides that bind to PAH2 display a strong in vitro inhibition of transwell invasion. This is accompanied by actin cytoskeleton reorganization with increased cortical actin deposition and downregulation of known Wnt target genes that are associated with epithelial to mesenchymal transition (EMT) and cancer cell invasion. Wnt pathway inhibition by SID decoy peptide was confirmed by decreased Wnt reporter activity and altered cytoplasmic localization of nuclear β-catenin. TGIF1, a transcription factor that modulates Wnt signaling and known to interact with the PAH2 domain of SIN3A, can be dissociated from the SIN3A complex by SID decoys. TGIF1 knockdown inhibits WNT target genes and in vitro cell invasion suggesting that TGIF1 might be a key target of the SID decoys to block tumor invasion. Taken together, targeting SIN3 function using SID decoys is a novel strategy to reverse invasion and the EMT program in TNBC translating into the inhibition of metastasis dissemination and eradication of residual disease.

Abstract 4115: Inhibition of triple negative breast cancer cell invasion by the targeted interference of Sin3A function affecting Wnt and TGFβ signaling

Cancer cell invasion is an obligatory step for metastatic dissemination that contributes to rapid relapse and a poor survival in TNBC patients. Development of novel therapeutic strategies to block tumor invasion is an unmet need for TNBC treatment and for other tumor types. We reported that decoys with the SID sequence designed to bind and inhibit the function of PAH-2 domain of Sin3A protein markedly prolong survival in the adjuvant setting due to inhibition of metastatic dissemination to the lungs and bone marrow in TNBC mouse models. Here, we show that TNBC cell lines treated with SID decoys (peptides) display a strong in vitro inhibition of migration and invasion. This is accompanied by actin cytoskeleton reorganization with increased cortical actin, and inhibition of proteolytic enzymes (MMP9; MT-MMP1 and uPA) involved in extracellular matrix degradation. DNA microarray and Ingenuity pathway analysis (IPA) showed that the SID decoys inhibit Wnt and TGFβ signaling that is associated with epithelial to mesenchymal transition (EMT). Treatment with SID decoy peptide downregulated WNT/β-catenin-driven transactivation as measured by decreased promoter H3K4me3 and decreased expression of Wnt target genes like LEF1 and TCF7L2. We also show that SID decoys induce translocation of nuclear β-catenin to the cytoplasm in TNBC at 24 hours. Wnt/β-catenin is critical for EMT, cancer stem cell self-renewal, and early invasion in TNBC. TGIF1, a transcription factor that modulates TGFβ and Wnt signaling pathways and known to to interact with the PAH2 domain of Sin3A, can be dissociated from Sin3A complex by SID decoy treatment as measured by co-immunoprecipitation (Co-IP) and proximity linked assay. DNA microarray of SID peptide treated TNBC cells shows inhibition of TGFβ signaling evidenced by downregulation of MMP9, MT1-MMP and PLAU, known target genes of this pathway. This is in line with inhibition of the EMT program predicted by the IPA analysis in SID peptide treated TNBC. Taken together, the results indicate that SID decoys have potential value as therapeutic agents to revert the EMT program in TNBC that should translate into the inhibition of metastasis dissemination and eradication of residual disease in TNBC. To test this in clinic future investigations will involve the use of our previously identified small molecule mimetic of SID peptide, selamectin that is also a FDA approved drug. Use of a recently constructed cyclic stapled peptide that inhibits PAH-2 binding and invasion at <10nM is also anticipated.

Citation Format: Yeon-Jin Kwon, Boris A. Leibovitch, Nidhi Bansal, Lutecia Pereira, Edgardo V. Ariztia, Kevin Petrie, Arthur Zelent, Ming-Ming Zhou, Eduardo F. Farias, Samuel Waxman. Inhibition of triple negative breast cancer cell invasion by the targeted interference of Sin3A function affecting Wnt and TGFβ signaling. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4115.

Emerging Roles of Epigenetic Regulator Sin3 in Cancer

Revolutionizing treatment strategies is an urgent clinical need in the fight against cancer. Recently the scientific community has recognized chromatin-associated proteins as promising therapeutic candidates. However, there is a need to develop more targeted epigenetic inhibitors with less toxicity. Sin3 family is one such target which consists of evolutionary conserved proteins with two paralogues Sin3A and Sin3B. Sin3A/B are global transcription regulators that provide a versatile platform for diverse chromatin-modifying activities. Sin3 proteins regulate key cellular functions that include cell cycle, proliferation, and differentiation, and have recently been implicated in cancer pathogenesis. In this chapter, we summarize the key concepts of Sin3 biology and elaborate the recent advancements in the role of Sin3 proteins in cancer with specific examples in multiple endocrine neoplasia type 2, pancreatic ductal adenocarcinoma, and triple negative breast cancer. Finally, a program to create an integrative approach for screening antitumor agents that target chromatin-associated factors like Sin3 is presented.

Sorafenib Inhibition of Mcl-1 Accelerates ATRA-Induced Apoptosis in Differentiation-Responsive AML Cells

PURPOSE

All trans-retinoic acid (ATRA) is successful in treating acute promyelocytic leukemia (APL) by inducing terminal differentiation-mediated cell death, but it has limited activity in non-APL acute myeloid leukemia (AML). We aim to improve ATRA therapy of AML by enhancing apoptosis through repression of the antiapoptotic proteins Bcl-2 and Mcl-1.

EXPERIMENTAL DESIGN

APL and AML cell lines, as well as primary AML samples, were used to explore the mechanisms regulating differentiation and apoptosis during ATRA treatment. Stable transfection and gene silencing with siRNA were used to identify the key factors that inhibit apoptosis during induction of differentiation and drugs that accelerate apoptosis.

RESULTS

In differentiation-responsive AML cells, ATRA treatment induces long-lasting repression of Bcl-2 while first upmodulating and then reducing the Mcl-1 level. The Mcl-1 level appears to serve as a gatekeeper between differentiation and apoptosis. During differentiation induction, activation of MEK/ERK and PI3K/Akt pathways by ATRA leads to activation of p90RSK and inactivation of glycogen synthase kinase 3β (GSK3β), which increase Mcl-1 levels by increasing its translation and stability. Sorafenib blocks ATRA-induced Mcl-1 increase by reversing p90RSK activation and GSK3β inactivation, maintains the repressed Bcl-2 level, and enhances ATRA induced apoptosis in non-APL AML cell lines and in primary AML cells.

CONCLUSIONS

Inhibition of Mcl-1 is required for apoptosis induction in ATRA differentiation-responsive AML cells. ATRA and sorafenib can be developed as a novel drug combination therapy for AML patients because this drug combination augments apoptosis by inhibiting Bcl-2 and Mcl-1.

Abstract CN05-03: Cooperation between a rexinoid and EGFR-TKI for lung cancer prevention via Cyclin D1 destabilization

We previously reported that both nuclear retinoic acid receptor (RAR, retinoid) and retinoid X receptor (RXR, rexinoid) agonists can trigger proteasomal degradation of cyclins. This confers check point arrest and repair of carcinogenic DNA damage in bronchial epithelial cells. Mechanisms responsible for this induced degradation were discovered. These included ubiquitin-dependent as well as ISG15-dependent programs that independently destabilized expression of cyclin D1 and other G1 cyclin proteins. The critical receptor that confers this cyclin destabilization was RARβ. Yet, silencing of RARβ; and specifically of the previously unrecognized isoform that we cloned and designated as RARβ1 likely accounts for clinical resistance to classical retinoids (like 13-cis-retinoic acid and all-trans-retinoic acid) in lung carcinogenesis. We sought to learn whether RXR/RAR heterodimer complex activation with a rexinoid was able to trigger cyclin destabilization. This was found to be the case in in vitro studies. This finding implied that the same pathway would be engaged in the in vivo setting. To establish if this occurs, we engineered transgenic mice independently with human surfactant C-driven wild-type cyclin E or a proteasome-degradation resistant cyclin E species. This mouse model was developed because human pre-malignant and malignant lung lesions frequently deregulate cyclin expression. Intriguingly, these mice recapitulated many features of lung carcinogenesis found in patients. Neoplastic changes were enhanced by transgenic expression of the degradation-resistant cyclin E species. We built on this finding by showing that a rexinoid and an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) each chemoprevented lung cancers in vinyl carbamate-induced lung tumors within strain A/J mice. Notably, the rexinoid was more potent that the EGFR-TKI in conferring this chemoprevention. Both agents also reduced cyclin expression, but did so through distinct mechanisms. We sought to learn if a rexinoid (bexarotene) cooperated with an EGFR-TKI (erlotinib) in exerting anti-tumorigenic effects in lung cancer. Cooperation between these agents was found in both murine and human lung cancer cells and even in those cells that exhibited KRAS/p53 mutations. Over the past decade, we translated this work into the cancer clinic through a series of five clinical trials that moved this work through successive phase 0, phase I, and phase II trials of lung and aerodigestive tract cancers. In window of opportunity trials, pharmacodynamic responses (cyclin repression and induced necrosis and inflammatory responses) were seen when intratumoral levels of these drugs were comparable to those necessary to trigger in vitro effects. A phase II trial in heavily pre-treated stage IV non-small cell lung cancer (NSCLC) cases was performed. EGFR and cyclin expression profiles as well as KRAS mutations were searched for in these NSCLC cases. Findings revealed substantial cyclin repression and reduction of lung cancer growth by combined therapy with a rexinoid (bexarotene) and EGFR-TKI (erlotinib). Cyclins were repressed while necrosis and inflammation were induced in post-treatment versus pre-treatment lung tumor biopsies obtained in this window of opportunity trial. Objective anti-tumor responses occurred whether or not KRAS or activating EGFR mutations were detected. This refractory NSCLC trial had 3 major clinical responses (2 had KRAS or EGFR mutations) with prolonged survival (583, 665, and 1460+ days, respectively). Median survival was 22 weeks (16 weeks for controls). Hypertriglyceridemia or rash significantly increased median overall survival to 24 weeks. Thus, this combination regimen revealed substantial clinical anti-tumor activity against NSCLCs. Taken together, these findings indicate that cooperation between a rexinoid and EGFR-TKI can chemoprevent and treat lung cancers by causing cyclin destabilization. These agents are also useful tools to identify other antineoplastics that repress lung cancers by destabilizing cyclin expression or by inhibiting their associated kinases. Evidence for this will be presented in this session.

Citation Format: Konstantin H. Dragnev, Vincent Memoli, Sarah J. Freemantle, Samuel Waxman, Ethan Dmitrovsky. Cooperation between a rexinoid and EGFR-TKI for lung cancer prevention via Cyclin D1 destabilization. [abstract]. In: Proceedings of the Thirteenth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2014 Sep 27-Oct 1; New Orleans, LA. Philadelphia (PA): AACR; Can Prev Res 2015;8(10 Suppl): Abstract nr CN05-03.

Selective Inhibition of SIN3 Corepressor with Avermectins as a Novel Therapeutic Strategy in Triple-Negative Breast Cancer

Triple-negative breast cancers (TNBC) lacking estrogen, progesterone, and HER2 receptors account for 10% to 20% of breast cancer and are indicative of poor prognosis. The development of effective treatment strategies therefore represents a pressing unmet clinical need. We previously identified a molecularly targeted approach to target aberrant epigenetics of TNBC using a peptide corresponding to the SIN3 interaction domain (SID) of MAD. SID peptide selectively blocked binding of SID-containing proteins to the paired α-helix (PAH2) domain of SIN3, resulting in epigenetic and transcriptional modulation of genes associated with epithelial-mesenchymal transition (EMT). To find small molecule inhibitor (SMI) mimetics of SID peptide, we performed an in silico screen for PAH2 domain-binding compounds. This led to the identification of the avermectin macrocyclic lactone derivatives selamectin and ivermectin (Mectizan) as candidate compounds. Both selamectin and ivermectin phenocopied the effects of SID peptide to block SIN3-PAH2 interaction with MAD, induce expression of CDH1 and ESR1, and restore tamoxifen sensitivity in MDA-MB-231 human and MMTV-Myc mouse TNBC cells in vitro. Treatment with selamectin or ivermectin led to transcriptional modulation of genes associated with EMT and maintenance of a cancer stem cell phenotype in TNBC cells. This resulted in impairment of clonogenic self-renewal in vitro and inhibition of tumor growth and metastasis in vivo. Underlining the potential of avermectins in TNBC, pathway analysis revealed that selamectin also modulated the expression of therapeutically targetable genes. Consistent with this, an unbiased drug screen in TNBC cells identified selamectin-induced sensitization to a number of drugs, including those targeting modulated genes.

Abstract 3511: Targeted epigenetic reprogramming reverts tumor progression in triple-negative breast cancer models by the activation of retinoic acid receptor alpha

INTRODUCTION: Triple negative breast cancer (TNBC) is associated with aggressiveness, early recurrence and poor prognosis and no other therapeutic alternative besides chemotherapy. The silencing of genes associated with cell differentiation in cancer is required for tumor progression. In this process the epigenetic modifications induced by aberrant control of the chromatin remodeling machinery in transformed cells plays a key role. Therefore, finding a mechanism to restore the expression of these genes by reverting the abnormal epigenetic modifications is an important task in the fight against cancer. We showed previously that the selective interference of the Sin3's PAH2 domain with Sin3 interaction domain (SID) mimicking peptides restored expression of E-cadherin, estrogen receptor and RARa target genes such as RARb and CRBP1 leading to cell differentiation and anti-tumor effect in TNBC cells. Here we studied whether the re-expression of retinoic acid receptors (RARs) induced by the small molecule C16 (SID decoy) can make TNBC cells sensitive to selective retinoid therapies.

EXPERIMENTAL APPROACH: Human and mouse cell models of TNBC as well as MMTV-Myc oncomice were used to test the effects of the SID decoys on the induction of RAR signaling, cell proliferation, induction of differentiation in 3D cultures, expansion of the cancer stem cell compartment, atypical ductal hyperplasia (ADH), ductal carcinola in situ (DCIS), tumor development and metastatic dissemination.

RESULTS: Our data show that C16 induced a differential expression of RARs, ∼10 fold upregulation of RARa2, RARbeta1/2, ∼10 fold downregulation of RARg1 and ∼30% increased production of retinoic acid (RA). The combination of C16 plus RARa agonists, AM80 (tamibarotene) or AM580 induced 75% inhibition of cell proliferation in 2D cultures, induced immature acini in 3D and impaired cancer stem cell proliferation inhibiting tumorsphere formation (∼65%) in vitro. In vivo, the combination of C16 and AM580 reduced 90% tumor growth and metastasis. Interestingly, the treatment of MMTV-Myc oncomice with C16 alone or in combination with AM80 prevented mammary gland hyperplasia, DCIS and delayed tumor development (80% tumor free survival, Kaplan-Meier analysis).

CONCLUSION: As a whole, the epigenetic reprogramming of the TNBC cells is promising for design of therapies based on the use of RARa agonists to induce differentiation of the tumor cells; giving these patients a chance of an alternative or complementary therapy to chemotherapy regimens.

Citation Format: Nidhi Bansal, Almudena Bosch, Boris A. Leibovitch, Keely Pierzchalski, Zhou Ming-Ming, Maureen Kane, Samuel Waxman, Eduardo Farias. Targeted epigenetic reprogramming reverts tumor progression in triple-negative breast cancer models by the activation of retinoic acid receptor alpha. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3511. doi:10.1158/1538-7445.AM2015-3511

Abstract 1989: Targeting Sin3-Pf1 complex: Novel site-specific epigenetic therapy for triple negative breast cancer

Introduction: Dearth of clinically validated drug targets is a major challenge in Triple Negative Breast Cancer (TNBC) that limits the treatment options to chemotherapy with intense cytotoxic consequences. We previously identified PAH2 domain of Sin3 protein as potential therapeutic target in TNBC and shown that protein-protein interactions of Sin3 via its PAH-2 domain can be disrupted by decoys (Mad1-SID peptide/small molecule inhibitors) designed based on the Sin3 interaction domain (SID) of transcription factor Mad1. Chromatin regulator Pf1 shown to be overexpressed in breast cancer and interacting with PAH2 domain of Sin3 can also be dissociated from Sin3 complex by Mad1-SID. In this study we identify Pf1 to be a significant contributor to the oncogenic phenotype associated with TNBC.

Methods: Pf1 knockdown lines were generated by stably transfecting MDA-MB-231 cells with Pf1-shRNA or scr-shRNA. Cells were cultured in 2D and assayed for cancer stem cell (CSC) markers and ALDH activity by flow cytometry. For colony morphogenesis cells were cultured in 3D Matrigel. qRT-PCR were performed to assay expression of Nanog, Sox2 and Oct4. Fluorescence anisotropy and co-immunoprecipitation assays were used to test Sin3-Mad1 and Sin3-Pf1 interaction in the presence or absence of Mad1-SID and/or Pf1-SID.

Results: MDA-MB-231 cells transfected with Pf1-shRNA had over two fold reduced ability to form colonies in 3D Matrigel cultures, with ∼95% of colonies non-invasive in contrast to the invasive star-like colonies formed by cells transfected with Scr-shRNA. Additionally reduction in Pf1 level was accompanied by a ∼1.5-fold reduction (p<0.05) in the tumorsphere forming ability of MDA-MB-231 cells. Pf1 depletion also significantly reduced RNA and protein of Nanog, Oct4 and Sox2. Confocal imaging revealed reduced levels and nuclear accumulation of Nanog, Sox2 and Oct4 in cells transfected with Pf1-shRNA compared to Scr-shRNA. Pf1 knockdown resulted in a 2.5-fold decrease in ALDH1 positive cells (6.55% in Scr-shRNA vs 2.59% in Pf1-shRNA). The CD44low/CD24low/neg population was enriched 3 fold over cells transfected with Scr-shRNA. From a therapeutic perspective we have designed a linear peptide corresponding to the Sin3 interaction domain of Pf1 (Pf1-SID). By fluorescence anisotropy we show that in comparison to Mad1-SID (IC50 = 1.4±0.3 μM), several hundred times higher concentration of Pf1-peptide (IC50 = 826±162 μM) is required to dissociate Sin3-Mad1 interaction. Co-immunoprecipitation assays show that Pf1-SID can specifically dissociate Pf1 from Sin3 without affecting the binding of Mad1 with PAH2 domain of Sin3. Pf1-SID treated MDA-MB-231 cells also have reduced invasive capacity and CSC traits.

Conclusion: PAH2 domain of Sin3 and its interaction with Pf1 is potential drug target and Pf-1SID-mediated disruption of Sin3-Pf1 complex as translation relevance for first site-specific epigenetic therapy for TNBC.

Citation Format: Nidhi Bansal, Joanna Wexler, Yeon-jin Kwon, Elena C. Gil, Boris Leibovitch, Rajal Sharma, Arthur Zelent, Ming-Ming Zhou, Eduardo Farias, Samuel Waxman. Targeting Sin3-Pf1 complex: Novel site-specific epigenetic therapy for triple negative breast cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1989. doi:10.1158/1538-7445.AM2015-1989

Abstract P1-12-08: Bortezomib enhances the efficacy of fulvestrant by promoting the aggregation of the ER in the cytoplasm

Background: Aromatase inhibitors (AIs) are standard treatment for Estrogen Receptor (ER)+ breast cancers in post-menopausal women where the main source of estradiol comes from adipose tissue when the aromatase enzyme converts androgens to estrogens. However, in premenopausal women, functioning ovaries flood the body with estrogens, and aromatase inhibitors used alone offer no therapeutic benefit. In addition to tamoxifen and aromatase inhibitors, estrogen receptor down-regulators, are a third type of anti-estrogen. The first of this class to be FDA approved is Fulvestrant, which acts by promoting the proteosomal degradation of the ER. Like tamoxifen, fulvestrant binds directly to the ER but while tamoxifen has both antagonist and agonist effects on the ER, fulvestrant is a pure antagonist. Other important advantages of fulvestrant over tamoxifen are that 1) fulvestrant prevents the ER from binding DNA, 2) fulvestrant is not linked to increased risk of endometrial cancer, 3) fulvestrant promotes permanent degradation of the ER.

The molecular machinery leading to the degradation of the ER in the nucleus following fulvestrant treatment is well described and correlates with its ubiquitination in the nucleus. A less well-recognized mechanism, is fulvestrant’s ability to promote the aggregation of the newly synthesized ER in the cytoplasm. Understanding that protein aggregates are toxic when not eliminated by the proteasome, we took advantage of this effect of fulvestrant to ask whether combining fulvestrant with the proteasome inhibitor Bortezomib could enhance the efficacy of Fulvestrant.

Results: We found that bortezomib enhances the aggregation of the ER in the cytoplasm following treatment with fulvestrant. Further, these aggregates were found to be insoluble and to activate the unfolded protein response (UPR), a stress response that leads to cell death. Further, bortezomib is able to prevent the activation of cytoprotective responses linked to the acquisition of fulvestrant resistance. Furthermore, in a breast cancer mouse model of tamoxifen resistance, the combination induced tumor regression. We currently are testing new generation proteasome inhibitors and the results will be presented at the meeting.

Conclusion: We conclude that adding bortezomib to fulvestrant enhances its efficacy by taking advantage of a previously poorly recognized mechanism–fulvestrant’s induction of ER aggregation in the cytoplasm. Further, our data suggest that this strategy will block the ability of cells to acquired resistance to fulvestrant. Our group has developed a clinical trial that has tested this combination and the results of this trial presented at the meeting.

Citation Format: Doris Germain, Kerin Adelson, George Raptis, Samuel Waxman. Bortezomib enhances the efficacy of fulvestrant by promoting the aggregation of the ER in the cytoplasm [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-12-08.

Abstract S6-03: Randomized phase II trial of fulvestrant alone or in combination with bortezomib in hormone receptor-positive metastatic breast cancer resistant to aromatase inhibitors: A New York cancer consortium trial

Purpose: Fulvestrant (F) is a selective estrogen receptor downregulator (SERD) with activity in aromatase-inhibitor (AI) resistant estrogen receptor (ER)-positive metastatic breast cancer (MBC). In preclinical studies, the proteasome inhibitor bortezomib (B) enhances the antineoplastic effects of F, in part by promoting accumulation of large ER-aggregates that lead to cell death (Ishii et al. Clin Cancer Res 2011 17:2292). The objective of this study was to determine if the combination of F+B was more efficacious than F alone in MBC after AI progression.

Patients and Methods: Postmenopausal women with ER-positive MBC who had progressive disease after prior AI therapy were eligible. They were randomized to F alone (500 mg IM days -15, 1, 15 in cycle 1, and day 1 of each subsequent cycle) or in combination with B (1.6 mg/m2 IV on days 1, 8, 15). The primary endpoint was progression free survival (PFS), measured from cycle 1, day 1 of starting F. A sample size of 118 was pre-specified in order to provide sufficient power to detect an improvement in median PFS from 5.4 to 9.0 months, and compare PFS rates after 6 and 12 months (1-sided alpha=0.10, beta=0.10). Patients with progression on F could cross over to the F+B combination.

Results: Of 118 patients enrolled, 59 received F alone (arm A), 57 received F+B (arm B), and 2 assigned to arm B never initiated protocol therapy. There were no significant differences in patient characteristics between arms with regard to median age (57 vs. 59 years), ECOG performance status (0 and 1, 64% and 36%, respectively), prior chemotherapy for metastasis (25%), or liver metastases (37%), although patients in arm A had longer median interval between diagnosis and metastasis (49 vs. 28 months) and were more likely to present with metastasis (32% vs. 26%). Patients in arm B had more adverse events (all grades), including nausea (63% vs. 29%), diarrhea (47% vs. 8%), sensory neuropathy (46% vs. 29%), and limb edema (37% vs. 19%), although grade 3-4 events were uncommon, and only 11% discontinued B due to toxicity. At 12 months, the PFS proportion in Arm A and Arm B was 13.6% vs. 28.1%, respectively (P=0.03, 1-sided chi-square test) (95% CI for difference [14.5%] = -0.06%, 29.1%). Although median PFS was similar in the two arms (2.69 vs. 2.73 months, respectively), the hazard ratio for Arm B vs. Arm A (referent) was 0.73 (95% CI = 0.49, 1.09, P=0.06, 1-sided log rank test). Both results were significant at the pre-specified 1-sided 0.10 alpha level. Of 27 patients on arm A who crossed over to F+B at progression, 4 (15%) were progression-free for at least 24 weeks and had periods of disease control that were longer than when treated with F alone.

Conclusion: Adding bortezomib to fulvestrant in AI-resistant ER-positive MBC enhances its effectiveness by delaying acquired fulvestrant resistance. These results support additional evaluation of proteasome inhibitors in combination with SERDs.

Acknowledgement: Supported by contract N01-CM-62204 to the New York Cancer Consortium (P.I. J. Sparano) and grant P30 CA013330 (P.I. D. Goldman) from the National Institutes of Health, and by a grant from Millennium, Inc.

Citation Format: Kerin B Adelson, Bhuvaneswari Ramaswamy, Joseph A Sparano, Paul J Christos, John J Wright, George Raptis, Miguel C Villalona, Cynthia X Ma, Dawn Hershman, Joseph Baar, Paula Klein, Tessa Cigler, G Thomas Budd, Yelena Novik, Antoinette R Tan, Susan Tannenbaum, Anupama Goel, Ellis Levine, Charles L Shapiro, Eleni Andreopoulou, Michael Naughton, Kevin Kalinsky, Samuel Waxman, Doris Germain. Randomized phase II trial of fulvestrant alone or in combination with bortezomib in hormone receptor-positive metastatic breast cancer resistant to aromatase inhibitors: A New York cancer consortium trial [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr S6-03.

Unique genomic profile of fibrolamellar hepatocellular carcinoma

BACKGROUND & AIMS

Fibrolamellar hepatocellular carcinoma (FLC) is a rare primary hepatic cancer that develops in children and young adults without cirrhosis. Little is known about its pathogenesis, and it can be treated only with surgery. We performed an integrative genomic analysis of a large series of patients with FLC to identify associated genetic factors.

METHODS

By using 78 clinically annotated FLC samples, we performed whole-transcriptome (n = 58), single-nucleotide polymorphism array (n = 41), and next-generation sequencing (n = 48) analyses; we also assessed the prevalence of the DNAJB1-PRKACA fusion transcript associated with this cancer (n = 73). We performed class discovery using non-negative matrix factorization, and functional annotation using gene-set enrichment analyses, nearest template prediction, ingenuity pathway analyses, and immunohistochemistry. The genomic identification of significant targets in a cancer algorithm was used to identify chromosomal aberrations, MuTect and VarScan2 were used to identify somatic mutations, and the random survival forest was used to determine patient prognoses. Findings were validated in an independent cohort.

RESULTS

Unsupervised gene expression clustering showed 3 robust molecular classes of tumors: the proliferation class (51% of samples) had altered expression of genes that regulate proliferation and mammalian target of rapamycin signaling activation; the inflammation class (26% of samples) had altered expression of genes that regulate inflammation and cytokine enriched production; and the unannotated class (23% of samples) had a gene expression signature that was not associated previously with liver tumors. Expression of genes that regulate neuroendocrine function, as well as histologic markers of cholangiocytes and hepatocytes, were detected in all 3 classes. FLCs had few copy number variations; the most frequent were focal amplification at 8q24.3 (in 12.5% of samples), and deletions at 19p13 (in 28% of samples) and 22q13.32 (in 25% of samples). The DNAJB1-PRKACA fusion transcript was detected in 79% of samples. FLC samples also contained mutations in cancer-related genes such as BRCA2 (in 4.2% of samples), which are uncommon in liver neoplasms. However, FLCs did not contain mutations most commonly detected in liver cancers. We identified an 8-gene signature that predicted survival of patients with FLC.

CONCLUSIONS

In a genomic analysis of 78 FLC samples, we identified 3 classes based on gene expression profiles. FLCs contain mutations and chromosomal aberrations not previously associated with liver cancer, and almost 80% contain the DNAJB1-PRKACA fusion transcript. By using this information, we identified a gene signature that is associated with patient survival time.

Abstract 807: Selamectin and ivermectin are small molecule inhibitors that interfere with Sin3A-PAH2 function and exert anti-tumor activity in triple-negative breast cancer

INTRODUCTION: Sin3 is a complex scaffolding protein that participates in epigenetic regulation involved in a variety of biological processes, including chromatin remodeling, development, differentiation, cell cycle and survival. Paired Amphipathic domain 2 (PAH2) domain of Sin3 was shown to interact with Sin3 interacting domain (SID)-containing transcription factors, such as Mxd1, KLF10/11, and REST. Previously, we reported that SID transcripts and decoy peptides disrupt the interactions between Sin3-PAH2 domain and SID-containing transcription factors and induce epigenetic reprogramming in TNBC.

RESULTS AND CONCLUSION: Here we show that fourteen SMIs mimicking SID decoys were identified by in silico computation from a chemical library composed of 115,000 compounds. We confirmed that selamectin and ivermectin are SID decoys using duo-link assays. Our NMR 15N-HSQC spectroscopy binding results further demonstrated ivermectin, which shares the same binding site as selamectin, directly interacted with PAH2. Moreover, selamectin inhibited Sin3 repression activity as measured by mammalian two-hybrid and in vitro GST pull-down assays. Notably, ivermectin was approved by Food and Drug Administration (FDA) to treat small animals and human. However, the anti-tumorigenic roles for these SMIs had not been investigated in TNBC in vitro and in vivo. Remarkably, these SMIs did not affect growth in 2-dimensional (2D) clonogenecity assay, but significantly suppressed growth in 3D matrigel and tumorsphere cultures. Moreover, selamectin significantly suppressed Myc mammary tumor growth in vivo more than 50 percent without any cytotoxicity. Selamectin and ivermectin induced re-expression of CDH1 and ESR1, restoring tamoxifen sensitivity. Treatment with these compounds inhibited in vitro invasion as measured by Boyden chamber in MCF7/ADR and MDA-MB-231 cells. Selamectin and ivermectin were shown to alleviate multidrug resistance and enhance doxorubicin and paclitaxel cytotoxicity in MCF7/ADR cells, which is unrelated to disruption of Sin3-PAH2. Based on further studies of the Sin3A complexes using selamectin and ivermectin, we seek to identify novel SMIs with better efficiency for targeting Sin3 complex and treating TNBCs in the future.

Citation Format: Yeon-Jin Kwon, Boris A. Leibovitch, Lei Zeng, Mihaly Mezei, Rossitza Christova, Shuai Yang, Rajal Sharma, Edgardo Aritzia, nidhi bansal, Ming-Ming Zhou, Authur Zelent, Eduardo Farias, Samuel Waxman. Selamectin and ivermectin are small molecule inhibitors that interfere with Sin3A-PAH2 function and exert anti-tumor activity in triple-negative breast cancer. [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 807. doi:10.1158/1538-7445.AM2014-807

Abstract 411: Targeted PF1, JARID1B inhibition induces epigenetic reprogramming in triple negative breast cancer

Triple Negative Breast cancer (TNBC) is an aggressive subtype of breast cancer associated with early recurrence and poor prognosis. The treatment options are limited due to lack of expression of common drug targets: estrogen receptor (ER), Progesterone receptor (PR) and Epidermal growth factor receptor 2 (Her2). Epigenetic programs can generate aberrant transcription contributing to TNBC progression; however the dynamic and reversible nature of epigenetic changes offers the possibility to reprogram cancer cells to re-express targets that can render TNBC sensitive to targeted therapies like tamoxifen. Envisioning such ‘epidrugs’, we previously published that targeting PAH2 domain of the master transcriptional scaffold Sin3 by stable expression of 13-mer peptide corresponding to a specific motif called SID (mSin3A interaction domain) disrupts its interaction with a small group of SID-containing transcription factors. This interference reverts the expression of important breast cancer-associated genes and impairs tumor growth in vivo. We have now extended our study towards the evaluation of a cell penetrating SID peptide (pSID) in in vitro and in vivo models to establish parameters for the design of targeted epigenetic therapy for TNBC. pSID co-localizes with Sin3A and interference with PAH2-mediated Sin3A functions by pSID is shown by disruption of Sin3A-MAD1 interactions in Co-IP and Duo-Link assays. pSID treatment in MDA-MB 231 cells results in functional re-expression of CDH1 and ER along with increased H3K4 and decreased H3K27 methylation on their promoters. We also show reduction in the tumorsphere formation by pSID-pretreated MDA-MB-231 cells indicating possible epigenetic reprogramming of tumor initiating stem cells towards a differentiated phenotype. Support to this hypothesis is added by the 50% reduction in tumor growth and re-expression of CDH1 observed in FVB mice injected with pSID-pretreated MMTV-myc cells. Moreover, microarray expression analysis indicates pSID-induced EMT reversal, increased cell adhesion and reduced cell migration. Intriguingly, upon further dissection of the mechanism of epigenetic regulation by pSID we show dissociation of two important chromatin readers/modifiers from the Sin3 complex: histone H3K4Me3/2 demethylase JARID1B and H3K4Me0 binding PHD-like domain containing protein PF1; both with significantly correlated overexpression in invasive breast carcinoma. We also observe loss of recruitment of JARID1B but not Sin3A from the CDH1 promoter. Currently studies are underway to understand the cooperative role between JARID1B and PF1 in potentiating the aberrant transcription regulation by Sin3 at important breast cancer-associated promoters that can be selectively reprogrammed by SID decoys. We believe this selectivity can limit the otherwise adverse affects that may be observed by the use of generic HDAC inhibitors and demethylating agents.

Citation Format: Rossitza Christova, Kevin Petrie, Nidhi Bansal, Boris Leibovitch, Louise Howell, Veronica Gil, Ming-Ming Zhou, Edgardo Ariztia, Eduardo Farias, Arthur Zelent, Samuel Waxman. Targeted PF1, JARID1B inhibition induces epigenetic reprogramming in triple negative breast cancer. [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 411. doi:10.1158/1538-7445.AM2014-411

Ethacrynic acid and a derivative enhance apoptosis in arsenic trioxide-treated myeloid leukemia and lymphoma cells: the role of glutathione S-transferase p1-1

PURPOSE

Arsenic trioxide (ATO) as a single agent is used for treatment of acute promyelocytic leukemia (APL) with minimal toxicity, but therapeutic effect of ATO in other types of malignancies has not been achieved. We tested whether a combination with ethacrynic acid (EA), a glutathione S-transferase P1-1 (GSTP1-1) inhibitor, and a reactive oxygen species (ROS) inducer will extend the therapeutic effect of ATO beyond APL.

EXPERIMENTAL DESIGN

The combined apoptotic effects of ATO plus ethacrynic acid were tested in non-APL leukemia and lymphoma cell lines. The role of ROS, GSTP1-1, glutathione (GSH), and Mcl-1 in apoptosis was determined. The selective response to this combination of cells with and without GSTP1-1 expression was compared.

RESULTS

ATO/EA combination synergistically induced apoptosis in myeloid leukemia and lymphoma cells. This treatment produced high ROS levels, activated c-jun-NH(2)-kinase (JNK), and reduced Mcl-1 protein. This led to the decrease of mitochondrial transmembrane potential, release of cytochrome c, and subsequently, to activation of caspase-3 and -9. Induction of apoptosis in leukemia and lymphoma cells expressing GSTP1-1 required high ethacrynic acid concentrations to be combined with ATO. Silencing of GSTP1 in leukemia cells sensitized them to ATO/EA-induced apoptosis. In a subgroup of B-cell lymphoma, which does not express GSTP1-1, lower concentrations of ethacrynic acid and its more potent derivative, ethacrynic acid butyl-ester (EABE), decreased intracellular GSH levels and synergistically induced apoptosis when combined with ATO.

CONCLUSION

B-cell lymphoma cells lacking GSTP1-1 are more sensitive than myeloid leukemia cells to ATO/EA-induced apoptosis.

CD44 ligation with A3D8 antibody induces apoptosis in acute myeloid leukemia cells through binding to CD44s and clustering lipid rafts

CD44 is a cell surface antigen expressed on acute myeloid leukemia cells and is used as a marker to isolate leukemia stem cells. CD44 ligation with the antibody A3D8 has been found to induce apoptosis in human acute promyelocytic leukemia (APL) cells via activation of caspase-8. The mechanism of A3D8-induced caspase-8 activation was studied in APL NB4 cells. A3D8 induces lipid raft clustering which causes Fas aggregation as determined with a confocal microscope. A3D8-induced apoptosis is abrogated by the lipid raft disrupting agent methyl-β-cyclodextrin and the caspase-8 inhibitor Z-IETD-fmk. Western blot analysis reveals that A3D8 binds to the standard form of CD44 (CD44s). HL-60 cells without detectable CD44s protein are not responsive to A3D8-induced apoptosis. SKNO-1 cells containing higher level of CD44s protein are more sensitive to A3D8-induced apoptosis than NB4 cells. These results indicate that A3D8 induces apoptosis in leukemia cells through caspase-8 activation by binding to CD44s protein and inducing lipid raft clustering.

Downregulation of Mcl-1 through GSK-3β activation contributes to arsenic trioxide-induced apoptosis in acute myeloid leukemia cells

Arsenic trioxide (ATO) induces disease remission in acute promyelocytic leukemia (APL) patients, but not in non-APL acute myeloid leukemia (AML) patients. ATO at therapeutic concentrations (1-2 μM) induce APL NB4, but not non-APL HL-60, cells to undergo apoptosis through the mitochondrial pathway. The role of antiapoptotic protein Mcl-1 in ATO-induced apoptosis was determined. The levels of Mcl-1 were decreased in NB4, but not in HL-60, cells after ATO treatment through proteasomal degradation. Both GSK3β inhibitor SB216763 and siRNA blocked ATO-induced Mcl-1 reduction as well as attenuated ATO-induced apoptosis in NB4 cells. Silencing Mcl-1 sensitized HL-60 cells to ATO-induced apoptosis. Both ERK and AKT inhibitors decreased Mcl-1 levels and enhanced ATO-induced apoptosis in HL-60 cells. Sorafenib, a Raf inhibitor, activated GSK3β by inhibiting its phosphorylation, decreased Mcl-1 levels, and decreased intracellular glutathione levels in HL-60 cells. Sorafenib plus ATO augmented ROS production and apoptosis induction in HL-60 cells and in primary AML cells. These results indicate that ATO induces Mcl-1 degradation through activation of GSK3β in APL cells and provide a rationale for utilizing ATO in combination with sorafenib for the treatment of non-APL AML patients.

Abstract 1826: Anti-tumorigenic effects by targeted functional disruption of the Sin3 PAH-2 domain

The Sin3 A/B adapter proteins function as structural scaffolds for repressor/activator complexes that regulate transcription through the specific association with histone modifying enzymes and a number of transcription factors. Sin3 contains four paired amphipathic α-helices (PAH domains). We have reported earlier that targeted disruption of the PAH2 domain with a SID (Sin3 Interaction Domain) peptide decoy in triple negative (TN) breast cancer cells leads to cytoskeletal reorganization, loss of anchorage independent growth and 3D invasive morphology and decreased cell adhesion and invasion. There is epigenetic reprogramming of silenced genes such as CDH1, ESR1 and RARA which are re-expressed and together contribute to a SID decoy induced switch from basal to a more differentiated luminal phenotype (Farias, et. al., PNAS, 2010, 107:11811-6). Computerized screening coupled with such assays as Duolink, GST pull downs and mammalian two hybrid identified small molecule inhibitors (SMI) that mimic the effects of the SID decoy peptide. SMI inhibit cellular invasion at nanomolar range and in in vivo mouse myc TN breast cancer prolong latency, decrease local invasion and metastasis. Tumors recovered showed evidence of re-expression of E-cadherin and estrogen receptor. Early effects of SID decoy in TN breast cancer cells include inhibition of invasion that is associated with a significant decrease in Src phosphorylation within 2-4hr of treatment. Recovery of phosphorylation after SID decoy washout is coupled with recovered invasion at 24hr. These effects occurred prior to measurable increase in E-cadherin expression, suggesting a non-transcriptional effect. In Drosophila larval breast cancer models with activated Src/Ras, overexpression of SID inhibited (60%) tumor growth in the eye imaginal disc, and was eradicated by the addition of a MEK inhibitor (AZD-6244), indicating a strong synergy between SID and AZD-6244. In the adult fly SID expression greatly inhibited RetMEN2B induced eye tumors (90%). These data demonstrate that SID decoys have a potential to be effective agents in the treatment of TN breast cancer by promoting basal phenotype reversal, inhibiting invasion and metastasis, and could be synergistic with specific inhibitors of signal transduction targets. Moreover, SID decoys can overcome profound oncogenic stimulus such as Ras, Src and Ret suggesting that they have a potential greater role than just in the treatment of TN breast cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1826. doi:1538-7445.AM2012-1826

Bexarotene plus erlotinib suppress lung carcinogenesis independent of KRAS mutations in two clinical trials and transgenic models

The rexinoid bexarotene represses cyclin D1 by causing its proteasomal degradation. The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) erlotinib represses cyclin D1 via different mechanisms. We conducted a preclinical study and 2 clinical/translational trials (a window-of-opportunity and phase II) of bexarotene plus erlotinib. The combination repressed growth and cyclin D1 expression in cyclin-E- and KRAS/p53-driven transgenic lung cancer cells. The window-of-opportunity trial in early-stage non-small-cell lung cancer (NSCLC) patients (10 evaluable), including cases with KRAS mutations, repressed cyclin D1 (in tumor biopsies and buccal swabs) and induced necrosis and inflammatory responses. The phase II trial in heavily pretreated, advanced NSCLC patients (40 evaluable; a median of two prior relapses per patient (range, 0-5); 21% with prior EGFR-inhibitor therapy) produced three major clinical responses in patients with prolonged progression-free survival (583-, 665-, and 1,460-plus days). Median overall survival was 22 weeks. Hypertriglyceridemia was associated with an increased median overall survival (P = 0.001). Early PET (positron emission tomographic) response did not reliably predict clinical response. The combination was generally well tolerated, with toxicities similar to those of the single agents. In conclusion, bexarotene plus erlotinib was active in KRAS-driven lung cancer cells, was biologically active in early-stage mutant KRAS NSCLC, and was clinically active in advanced, chemotherapy-refractory mutant KRAS tumors in this study and previous trials. Additional lung cancer therapy or prevention trials with this oral regimen are warranted.

Abstract 5479: Mcl-1 is differentially regulated in acute myeloid leukemia cells treated with all trans retinoic acid and arsenic trioxide

Both all trans retinoic acid (ATRA) and arsenic trioxide (ATO) induce complete remission in acute promyelocytic leukemia (APL) patients. Using the APL derived NB4 cell line containing the PML-RARα fusion protein it has been found that ATRA induced differentiation while ATO mainly induced apoptosis. Previously it has been reported that the antiapoptotic proteins Bcl-2 and Bfl-1/A1 were regulated during ATRA-induced differentiation process in APL cells. However, the regulation of Mcl-1, a major antiapoptotic protein required during myeloid granulocyte differentiation, has not been determined. Recently it has been shown that ERK phosphorylates Mcl-1 and regulates its stability. The regulation of Mcl-1 and p-ERK by ATRA and ATO were investigated in NB4 and its subclone R4 cells, HL-60 and its subclone HL-60/Res cells. Both NB4 and R4 cells contain PML-RARα while HL-60 and HL-60/Res cells contain RARα. However, the ATRA binding domain in PML-RARα and RARα is mutant in R4 and HL-60/Res cells, respectively. The levels of Mcl-1 were induced by ATRA in both NB4 and HL-60 cells, but not in R4 cells nor HL-60/Res cells. The induction of Mcl-1 in NB4 and HL-60 cells correlated with the induction of differentiation and the increased level of p-ERK. Unlike ATRA treatment, ATO treatment decreased the levels of Mcl-1 in both NB4 and R4 cells, but not in HL-60 nor in HL-60/Res cells, which correlated with the induction of apoptosis and down-regulation of p-ERK. Both NB4 and R4 cells contain PML-RARα which is degraded by ATO, suggesting that PML-RARα plays a role in ATO-mediated down-regulation of Mcl-1. To test the effect of PML-RARα on the regulation of Mcl-1 after ATO treatment, U937/PR9 cells with the inducible expression of PML-RARα were used. Expression of PML-RARα increased the levels of Mcl-1 and p-ERK. ATO treatment decreased the levels of both Mcl-1 and p-ERK. These data suggest that ATRA increases the level of Mcl-1 through activating ERK due to overcoming PML-RARα transcriptional repression and activating RARα while ATO decreases the level of Mcl-1 through inactivation of ERK due to inducing degradation of PML-RARα. The increased level of Mcl-1 after ATRA treatment protects against cell death and promotes differentiation while the decreased level of Mcl-1 after ATO-treatment sensitizes apoptosis induction.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5479. doi:10.1158/1538-7445.AM2011-5479

Abstract LB-412: Combining bexarotene with erlotinib in window of opportunity and phase II trials causes lung cancer responses independent of KRAS mutations

Lung cancer is the leading cause of cancer-related mortality in the United States. Improved ways to treat and prevent lung cancer are needed. Increased epidermal growth factor receptor (EGFR) expression frequently occurs in lung carcinogenesis. Treatment with the EGFR-tyrosine kinase inhibitor (EGFR-TKI) erlotinib prolongs survival, especially in patients whose lung cancers harbor activating EGFR mutations. However, patients with non-small cell lung cancers (NSCLCs) that harbor KRAS mutations can be less responsive. Therefore, there is a need for improved NSCLC treatments irrespective of KRAS or EGFR mutation status. Previous studies showed that the rexinoid bexarotene causes cyclin D1 proteasomal degradation. The EGFR-TKI erlotinib also represses cyclin D1, but via different mechanisms. The combination of bexarotene with erlotinib was explored. Initial effects of this combination on tumor growth and cyclin D1 expression were examined in murine transgenic lung cancer cell models with or without KRAS/p53 mutations. Findings were translated into both early stage window of opportunity (14 patients enrolled) and advanced stage (42 patients enrolled) phase II NSCLC trials. In the window of opportunity trial, cyclin D1 was measured in pre-versus post-treatment NSCLC biopsies and in buccal swabs. EGFR and phospho-EGFR immunohistochemical expression was assessed in the paired tumor biopsies. KRAS and EGFR mutations were also examined. A phase II trial in heavily pre-treated stage IV NSCLC cases was performed with early PET responses evaluated. Findings reveal significant repression of cyclin D1 expression and lung cancer cell growth. Intriguingly, cyclin D1, EGFR and phospho-EGFR immunohistochemical expression profiles were reduced while necrosis and inflammatory cellular responses were induced in the window of opportunity trial independent of the presence of KRAS or EGFR mutations. Cyclin D1 was repressed in post-treatment buccal swabs. The refractory NSCLC trial (2 median relapses, 21% with prior EGFR-inhibitor therapies) had 3 major clinical responses (2 had KRAS or EGFR mutations) with prolonged survival (583, 665, and 1460+ days). Median survival was 22 weeks (16 weeks for controls). Hypertriglyceridemia or rash significantly increased median overall survival to 24 weeks. Early PET response did not reliably predict clinical response.

In summary, combining bexarotene with erlotinib can repress cyclin D1 and confer in vitro and clinical anti-tumor responses (including induced tumor necrosis and inflammatory changes) independent of EGFR or KRAS mutations present in the lung cancers. Notably, survival increased in the treated stage IV NSCLC patients when hypertriglyceridemia or rash developed. Clinical activity of this regimen is encouraging and warrants further study for lung cancer therapy or chemoprevention.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-412. doi:10.1158/1538-7445.AM2011-LB-412

Abstract 2826: Reversal of the basal phenotype in triple negative (TN) breast cancer using a SID decoy

We have previously reported that site-specific disruption of the Sin3 complex results in targeted epigenetic reprogramming and differentiation in TN breast cancer (Farias et al., PNAS 2010, 107:11811-6). The Sin3 A/B are multidomain adapter proteins part of a multisubunit corepressor scaffold that regulates transcription via the recruitement of HDAC and BP2/JARID1 A. Sin3 (A/B) contain four paired amphipathic α-helices known as PAH domains, a central HID (HDAC interaction domain) also serves as docking platform for a variety of corepressors, a C-terminal domain is a highly conserved region. We have targeted the disruption of the PAH2 domain binding to SID (mSin3A interaction domain) containing transcription factors such as MAD1, REST, KLF-9, -10, -11, -13 and -16, using a peptide decoy containing the SID motif. These studies have been carried out in several breast cancer cell lines including 5 TN, 2 estrogen receptor positive (ER+) and a non-transformed mammary cell line.

Transfection with a plasmid expressing minimal SID or treatment with a 13 amino-acid peptide (SID peptide) disrupts transcription factor binding to the PAH2 domain resulting in extreme changes in morphology, cytoskeletal organization, adhesion, decreased extracellular proteolytic activity (MMP-9 and uPA), loss of invasive capacity and anchorage independent growth. There was re-expression of functional E-cadherin, estrogen and retinoic acid receptors. Effects in vivo xenograft also included inhibition of tumor growth and metastasis in FVB mice. 3D cultures in Matrigel have revealed a SID decoy dependent switch from a basal to a more luminal phenotype. These effects of SID decoy occurred in TN but not in ER+ or non-transformed breast cancer cell lines. Taken together, these results support the hypothesis in which SID decoy interference with PAH2 domain binding can revert Epithelial/Mesenchymal Transition in TN breast cancer cells and results in a less malignant phenotype. Fourteen candidate small molecule inhibitors, from a computerized screen of 115,000 compounds, were tested in a mammalian two hybrid assay and some of them have been tested in cellular invasion, proliferation and morphogenesis assays. One of them, compound 14 (C14) has shown no toxicity, induces E-cadherin expression and is effective in inhibiting Matrigel invasion of MDA-MB-231 at 100 nM.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2826. doi:10.1158/1538-7445.AM2011-2826

Bortezomib enhances the efficacy of fulvestrant by amplifying the aggregation of the estrogen receptor, which leads to a proapoptotic unfolded protein response

PURPOSE

Fulvestrant is known to promote the degradation of the estrogen receptor (ER) in the nucleus. However, fulvestrant also promotes the aggregation of the newly synthesized ER in the cytoplasm. Accumulation of protein aggregates leads to cell death but this effect is limited as a result of their elimination by the proteasome. We tested whether combining fulvestrant with the proteasome inhibitor, bortezomib, could enhance the accumulation of ER aggregates and cause apoptotic cell death.

EXPERIMENTAL DESIGN

The rate of aggregation of the ER was monitored in ER(+) breast cancer cells lines, T47D, ZR-75.1, BT474, MDA-MB-361, MCF-7, fulvestrant resistance MCF-7, and tamoxifen-resistant T47D-cyclin D1 cells. Activation of the unfolded protein response, apoptosis, and metabolic rate were also monitored in these cell lines following treatment with fulvestrant, bortezomib, or bortezomib in combination with fulvestrant.

RESULTS

We found that bortezomib enhances the fulvestrant-mediated aggregation of the ER in the cytoplasm without blocking the degradation of the ER in the nucleus. Further, these aggregates activate a sustained unfolded protein response leading to apoptotic cell death. Further, we show that the combination induced tumor regression in a breast cancer mouse model of tamoxifen resistance.

CONCLUSIONS

Adding bortezomib to fulvestrant enhances its efficacy by taking advantage of the unique ability of fulvestrant to promote cytoplasmic aggregates of the ER. As this effect of fulvestrant is independent of the transcriptional activity of the ER, these results suggest that this novel combination may be effective in breast cancers that are ER(+) but estrogen independent.

Fibrolamellar carcinoma: a review with focus on genetics and comparison to other malignant primary liver tumors

Fibrolamellar carcinoma is a rare primary malignant liver neoplasm that usually affects adolescents and young adults with no underlying liver disease. Morphologically, the tumor cells resemble oncocytic hepatocytes arranged in cords with a stroma of lamellated collagen fibers. Immunohistochemical studies have found that fibrolamellar carcinomas express markers associated with both biliary (CK7 and epithelial membrane antigen) and hepatocytic (heppar-1and glypican-3) differentiation, as well as markers associated with hepatic progenitor cells (CK19 and EpCAM) and stem cells (CD133 and CD44). Genetic studies show fewer alterations compared with classic hepatocellular carcinoma. Pooled data from comparative genomic hybridization studies show that fibrolamellar carcinomas have fewer and less frequent genomic alterations when compared with classic hepatocellular carcinoma, cholangiocarcinoma, and hepatoblastoma. Of the alterations seen in fibrolamellar carcinoma, the most frequent are gains in 1q and 8q (also frequently seen in other hepatic tumors) and loss of 18q. Fibrolamellar carcinoma also has less frequent methylation of tumor suppressor promoters compared with hepatocellular carcinoma and minimal alterations in mitochondrial DNA. Fibrolamellar carcinoma is associated with better survival than hepatocellular carcinoma and cholangiocarcinoma, presumably due to the young age of the patients and the lack of cirrhosis. These features make more aggressive surgical therapy possible. There is currently very little information on the effectiveness of chemotherapy for fibrolamellar carcinoma.

Abstract 2996: Overexpression of potential oncogenic microRNAs defines a new molecular subclass of hepatocellular carcinoma

Background: Hepatocellular carcinoma (HCC) is the most common form of liver cancer and the third cause of cancer-related death worldwide. Its incidence is increasing mainly due to hepatitis C virus (HCV) infection. A molecular classification of HCC is still lacking. microRNAs (miRNAs) are small non-coding RNA involved in HCC pathogenesis. Their expression profiling represents a powerful tool to classify cancers.

Objectives: (1) To provide a miRNA-based molecular classification of HCC and, (2) To investigate the function of potential oncogenic miRNAs in HCC models.

Methods: Expression of 358 miRNAs was analyzed in 89 HCV-related HCCs using a bead-based miRNA expression profiling method. Integrative analysis including miRNA profiling, gene expression (Affymetrix U133 2.0®), DNA changes (Affymetrix STY Mapping Array®), IHC (p-Akt, p-IGF-IR, p-S6, p-EGFR, β-catenin) and mutation analysis (β-catenin) was performed. Expression of selected miRNA was validated in a validation set (n=167) by qRT-PCR. Methylation-specific PCR, FISH and SNP-array analyses were performed to identify mechanisms of miRNA deregulation. The function of miRNAs of interest was investigated in vitro by analyzing cell proliferation (thymidine incorporation), migration and invasion (trans-well migration and invasion assays, wound healing assay). Tumor development and growth following direct injection of luciferase-expressing cells stably transfected with specific miRNAs into the liver of nude mice were monitored to investigate their function in vivo. The bioluminescent signal emitted by luciferase-expressing cells was used as indicator of tumor growth.

Results: Three classes of HCC patients were identified and defined by activation of different pathways: Wnt signalling (32/89, 36%), IFN-related genes (29/89, 33%) and proliferative cascades (IGF, Akt/mTOR) (28/89, 31%). A subgroup within the proliferative class (8/89, 9% overexpressed a cluster of miRNAs on 19q13.42 (median fold change: 8.8). Hypomethylation of CpG island upstream the miRNA cluster (2/8, 25%) and copy number gains (1/8, 12.5%) were detected. Their overexpression was confirmed in a validation set (17/167, 10.2%). Members of the cluster family significantly increased proliferation (p<0.05), migration (p<0.02) and invasive capability (p<0.05) in vitro and promoted tumor development in vivo (detectable liver tumor in 4/6 mice compared with 0/6 of the controls after 4 weeks following injection). One mouse of the active arm was sacrificed at week 5 showing large invasive HCC at pathological study, while the others are still alive.

Conclusions: Overexpression of 19q miRNA family and activation of proliferative pathways defined a subclass of HCC. Members of 19q miRNA family increased cell proliferation, migration and invasion in vitro and promoted tumor development in vivo suggesting their role as novel potential oncogenic drivers in HCC.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2996.

Abstract 572: Interference with Sin3 PAH-2 domain function induces epigenetic reprogramming, differentiation and growth inhibition in breast cancer cells

Our recent work in understanding silenced retinoic acid response genes in breast cancer led us to explore the role of transcription repressor complexes in gene silencing in breast cancer. To this end we constructed a set of tagged vectors that contain a specific MAD1 motif called SID (mSin3A interaction domain), which binds with high affinity to block the function of the Sin3. Sin3A/B serve as multisubunit co-repressor scaffold protein that regulate gene transcription by recruiting histone deacetylase and histone demethylase activities to sequence-specific transcriptional repressors which are aberrant in breast cancer. The PAH2 domain of Sin3A/B binds with high affinity to a small number of transcription factors, and offers a more specific epigenetic target which contributes to the development of breast cancer. PAH-2 domain a specific component of a transcriptional repressor complex that plays an important role in modulating a small number of transcription factors containing the Sin3 PAH-2 interaction domain (SID). Here we demonstrated that in both human and mouse breast cancer cells, the targeted disruption of Sin3 function by introduction with their partners by the expression of SID transcript or peptide decoy interfered with PAH2 binding to SID-containing partner proteins as measured by co-immunoprecipitation and mammalian two-hybrid assays, reverteds the silencing of several genes involved in cell growth and differentiation. We observed that the SID decoy induced clear signs of differentiation in both human and mouse breast cancer cellsIn particular, the which include theSID decoys led to acinar morphogenesis in 3D cultures, increased adherence to collagen type-IV and laminin, reduced invasive phenotype and impaired tumor growth in vivo (>75%). This was associated with epigenetic reprogramming characterized by a marked increase in H3K4 2/3 methylation and a modest increase in H3 acetylation in the promoter region, promoter DNA demethylation and re-expression of the important breast cancer-associated silenced genes encoding E-cadherin, and, estrogen receptor α (ERα) and retinoic acid receptor β (RARβ)and impairment in tumor growth in vivo. There was increased expression of E-cadherin, CRBP1 and p27 known RAR response genes. The re-expression of ERα and RARβ in the “triple negative” MDA-MB-231 breast cancer cell line is functional since there was significant growth inhibition by tamoxifen after stimulation with 17b-estradiol and RAR activation by atRA and AM580. Therefore, the development of small molecules that mimic the 13 amino acid SID peptide and block interactions between PAH2 and SID-containing proteins This offers a new novel approach for treating this type of breast cancer and may also provide wider therapeutic implicationstriple negative breast cancer cells.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 572.

Abstract 1030: Arsenic trioxide plus ethacrynic acid-butyl ester is synergistic to induce apoptosis in myeloid leukemia cells through upregulation of NOXA

Arsenic trioxide (As2O3) induces complete remission in acute promyelocytic leukemia (APL) patients. However, other types of myeloid leukemia patients are less responsive to As2O3 treatment. APL t(15;17) NB4 cells are more sensitive to As2O3 apoptosis induction than other types of myeloid leukemia cells such as HL-60 and K562 cells. Previously we reported that As2O3 induces apoptosis in NB4 cells through a reactive oxygen species (ROS)-mediated pathway which is attenuated by the expression of glutathione-s-transferase π (GSTπ). NB4 cells contain lower levels of GSTπ than other types of myeloid leukemia cells. Therefore, inhibition of GSTπ should enhance As2O3 induction of apoptosis in other types of myeloid leukemia cells. We investigated the combined effect of As2O3 with ethacrynic acid (EA) and a more potent non-diuretic EA analogue ethacrynic acid-butyl ester (EABE), known GSTπ inhibitors, to induce apoptosis in HL-60 and K562 cells. As2O3 at clinical achievable concentrations (1-2 µM) did not induce apoptosis in HL-60 cells nor in K562 cells. EA at a concentration lower than 60 μM did not induce apoptosis in both cell lines either. As2O3 at 2 μM plus EA at 60 μM are synergistic to induce apoptosis in both HL-60 and K562 cells as measured by Annexin V staining, PARP cleavage and caspase activation. More intriguing, EABE at 1 μM (60 fold lower than EA), which inhibits GSTπ activity, exhibited synergistic induction with As2O3 in K562 cells. Combined index of As2O3 with EABE to induce apoptosis in K562 cells calculated by CompuSyn software was less than 1.0 which indicated synergism. Apoptosis induction by the combination treatment of As2O3 with EABE correlated with the upregulation of the Bcl-2 homology 3 (BH3)-only pro-apoptotic protein NOXA. Knock-down of NOXA using siRNA blocked apoptosis induction of As2O3 plus EABE, while, knock-down of Mcl-1 enhanced the apoptosis induction of As2O3 plus EABE. Immunoprecipiation with Mcl-1 antibody revealed that NOXA bond to Mcl-1 in the K562 cells treated with As2O3 plus EABE. Inhibition of ROS production did not inhibit the upregulation of NOXA nor the apoptosis induction of As2O3 plus EABE treatment. Our data suggest that As2O3 plus EABE induce apoptosis through a novel mechanism which induces NOXA and sequesters Mcl-1 leading to the activation the intrinsic apoptotic pathway.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1030.

Bortezomib Enhances the Efficacy of Fulvestrant by Promoting the Aggregation of the Estrogen Receptor in the Cytoplasm

Background: Aromatase inhibitors (AIs) are standard treatment for Estrogen Receptor (ER)+ breast cancers in post-menopausal women where the main source of estradiol comes from adipose tissue when the aromatase enzyme converts androgens to estrogens. However, in premenopausal women, functioning ovaries flood the body with estrogens, and aromatase inhibitors used alone offer no therapeutic benefit. In addition to tamoxifen and aromatase inhibitors, estrogen receptor down-regulators, are a third type of anti-estrogen. The first of this class to be FDA approved is Fulvestrant, which acts by promoting the proteosomal degradation of the ER. Like tamoxifen, fulvestrant binds directly to the ER but while tamoxifen has both antagonist and agonist effects on the ER, fulvestrant is a pure antagonist. Other important advantages of fulvestrant over tamoxifen are that 1) fulvestrant prevents the ER from binding DNA, 2) fulvestrant is not linked to increased risk of endometrial cancer, 3) fulvestrant promotes permanent degradation of the ER.The molecular machinery leading to the degradation of the ER in the nucleus following fulvestrant treatment is well described and correlates with its ubiquitination in the nucleus. A less well-recognized mechanism, is fulvestrant’s ability to promote the aggregation of the newly synthesized ER in the cytoplasm. Understanding that protein aggregates are toxic when not eliminated by the proteasome, we took advantage of this effect of fulvestrant to ask whether combining fulvestrant with the proteasome inhibitor Bortezomib could enhance the efficacy of Fulvestrant.Results: We found that bortezomib enhances the aggregation of the ER in the cytoplasm following treatment with fulvestrant. Further, these aggregates were found to be insoluble and to activate the unfolded protein response (UPR), a stress response that leads to cell death. Further, bortezomib is able to prevent the activation of cytoprotective responses linked to the acquisition of fulvestrant resistance. Furthermore, in a breast cancer mouse model of tamoxifen resistance, the combination induced tumor regression.Conclusion: We conclude that adding bortezomib to fulvestrant enhances its efficacy by taking advantage of a previously poorly recognized mechanism–fulvestrant’s induction of ER aggregation in the cytoplasm. Further, our data suggest that this strategy will block the ability of cells to acquired resistance to fulvestrant. Our group has developed a clinical trial that will test this combination.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5142.

Chronobiological Study of the Pharmacological Response of Rats to Combination Ketamine–Midazolam

Ketamine is commonly administered in combination with benzodiazepines to achieve surgical anaesthesia in rats. The aim of the present study was to analyze the pharmacological response of the combination ketamine-midazolam injected intraperitoneally at different times of day to rats. The study was conducted in July 2003, during the winter in the Southern hemisphere. Female prepuberal Sprague-Dawley rats synchronized to a 12h light:12h dark cycle (light, 07:00-19:00h) were used as experimental animals. A combination treatment of ketamine (40 mg/kg) and midazolam (2 mg/kg) was administered to five different clock-time groups of rats (n=7/group). Duration of the latency period, ataxia, loss-of-righting reflex (LRR), post-LRR ataxia, and total pharmacological response were assessed by visual assessment. Significant treatment-time differences were detected in the duration of LRR, post-LRR ataxia, and total pharmacological response duration. The longest pharmacological response occurred in rats injected during the light (rest) phase, and the shortest pharmacological response occurred in rats injected during the dark (activity) phase. Cosinor analysis documented circadian rhythmicity in the duration of post-LRR ataxia. The findings of the study indicate the duration of CNS-depression of the ketamine-midazolam combination exhibits treatment-time-dependent variation in the rat.

Astrocyte elevated gene-1 regulates hepatocellular carcinoma development and progression

Hepatocellular carcinoma (HCC) is a highly aggressive vascular cancer characterized by diverse etiology, activation of multiple signal transduction pathways, and various gene mutations. Here, we have determined a specific role for astrocyte elevated gene-1 (AEG1) in HCC pathogenesis. Expression of AEG1 was extremely low in human hepatocytes, but its levels were significantly increased in human HCC. Stable overexpression of AEG1 converted nontumorigenic human HCC cells into highly aggressive vascular tumors, and inhibition of AEG1 abrogated tumorigenesis by aggressive HCC cells in a xenograft model of nude mice. In human HCC, AEG1 overexpression was associated with elevated copy numbers. Microarray analysis revealed that AEG1 modulated the expression of genes associated with invasion, metastasis, chemoresistance, angiogenesis, and senescence. AEG1 also was found to activate Wnt/beta-catenin signaling via ERK42/44 activation and upregulated lymphoid-enhancing factor 1/T cell factor 1 (LEF1/TCF1), the ultimate executor of the Wnt pathway, important for HCC progression. Inhibition studies further demonstrated that activation of Wnt signaling played a key role in mediating AEG1 function. AEG1 also activated the NF-kappaB pathway, which may play a role in the chronic inflammatory changes preceding HCC development. These data indicate that AEG1 plays a central role in regulating diverse aspects of HCC pathogenesis. Targeted inhibition of AEG1 might lead to the shutdown of key elemental characteristics of HCC and could lead to an effective therapeutic strategy for HCC.

Pivotal role of mTOR signaling in hepatocellular carcinoma

BACKGROUND & AIMS

The advent of targeted therapies in hepatocellular carcinoma (HCC) has underscored the importance of pathway characterization to identify novel molecular targets for treatment. We evaluated mTOR signaling in human HCC, as well as the antitumoral effect of a dual-level blockade of the mTOR pathway.

METHODS

The mTOR pathway was assessed using integrated data from mutation analysis (direct sequencing), DNA copy number changes (SNP-array), messenger RNA levels (quantitative reverse-transcription polymerase chain reaction and gene expression microarray), and protein activation (immunostaining) in 351 human samples [HCC (n = 314) and nontumoral tissue (n = 37)]. Effects of dual blockade of mTOR signaling using a rapamycin analogue (everolimus) and an epidermal/vascular endothelial growth factor receptor inhibitor (AEE788) were evaluated in liver cancer cell lines and in a xenograft model.

RESULTS

Aberrant mTOR signaling (p-RPS6) was present in half of the cases, associated with insulin-like growth factor pathway activation, epidermal growth factor up-regulation, and PTEN dysregulation. PTEN and PI3KCA-B mutations were rare events. Chromosomal gains in RICTOR (25% of patients) and positive p-RPS6 staining correlated with recurrence. RICTOR-specific siRNA down-regulation reduced tumor cell viability in vitro. Blockage of mTOR signaling with everolimus in vitro and in a xenograft model decelerated tumor growth and increased survival. This effect was enhanced in vivo after epidermal growth factor blockade.

CONCLUSIONS

MTOR signaling has a critical role in the pathogenesis of HCC, with evidence for the role of RICTOR in hepato-oncogenesis. MTOR blockade with everolimus is effective in vivo. These findings establish a rationale for targeting the mTOR pathway in clinical trials in HCC.

Penetrating trauma to the external genitalia in Operation Iraqi Freedom

This report details the incidence and description of trauma to the external genitalia experienced during Operation Iraqi Freedom at a United States Army Combat Support Hospital, and demonstrates that acceptable rates of testicular salvage are possible in the combat setting. The operating room logs and the Joint Theater Trauma Registry were used to conduct a retrospective review of the patients who sustained genitourinary (GU) injuries at an US Army Combat Support Hospital (CSH) in Iraq from 27 February 2007 to 14 August 2007. Of the 3595 battle trauma injuries seen at the CSH during the time period, 168 (4.7%) had one or more GU injuries for a total of 172 GU injuries. Of these patients, 115 (68%) with GU injuries had one or more injuries to the external genitalia for a total of 119 external GU injuries. Penetrating trauma to the penis and scrotum accounted for 59 of the injuries. In total, 43 testicles were injured in 34 patients (9 had bilateral injuries). In total, 32 testes were repaired primarily and 11 were removed. Injuries to the external genitalia continue to account for the vast majority of GU trauma in a combat setting. Of patients who presented with penetrating testicular trauma, there was a 74.4% salvage rate, which is higher than previous reports of combat external genitalia injuries. Treatment of penetrating trauma to the external genitalia in a combat setting requires attention to tissue preservation while coordinating associated surgical procedures.

Focal gains of VEGFA and molecular classification of hepatocellular carcinoma

Hepatocellular carcinomas represent the third leading cause of cancer-related deaths worldwide. The vast majority of cases arise in the context of chronic liver injury due to hepatitis B virus or hepatitis C virus infection. To identify genetic mechanisms of hepatocarcinogenesis, we characterized copy number alterations and gene expression profiles from the same set of tumors associated with hepatitis C virus. Most tumors harbored 1q gain, 8q gain, or 8p loss, with occasional alterations in 13 additional chromosome arms. In addition to amplifications at 11q13 in 6 of 103 tumors, 4 tumors harbored focal gains at 6p21 incorporating vascular endothelial growth factor A (VEGFA). Fluorescence in situ hybridization on an independent validation set of 210 tumors found 6p21 high-level gains in 14 tumors, as well as 2 tumors with 6p21 amplifications. Strikingly, this locus overlapped with copy gains in 4 of 371 lung adenocarcinomas. Overexpression of VEGFA via 6p21 gain in hepatocellular carcinomas suggested a novel, non-cell-autonomous mechanism of oncogene activation. Hierarchical clustering of gene expression among 91 of these tumors identified five classes, including "CTNNB1", "proliferation", "IFN-related", a novel class defined by polysomy of chromosome 7, and an unannotated class. These class labels were further supported by molecular data; mutations in CTNNB1 were enriched in the "CTNNB1" class, whereas insulin-like growth factor I receptor and RPS6 phosphorylation were enriched in the "proliferation" class. The enrichment of signaling pathway alterations in gene expression classes provides insights on hepatocellular carcinoma pathogenesis. Furthermore, the prevalence of VEGFA high-level gains in multiple tumor types suggests indications for clinical trials of antiangiogenic therapies.