In vitro activity of isoimperatorin, alone and in combination, against Mycobacterium tuberculosis

Previous studies have shown that isoimperatorin (IO), a furanocoumarin isolated from several medicinal plants, has antimycobacterial activity against Mycobacterium tuberculosis strain H37Rv (ATCC 27294). This study demonstrated that IO has antimycobacterial activity against 2 drug-sensitive and 6 drug-resistant isolates, with minimum inhibitory concentrations (MICs) of 50-100 μg ml(-1) and 100-200 μg ml(-1), respectively. IO exhibited synergistic antimycobacterial effects with rifampin (RMP), isoniazid (INH) and ethambutol (EMB) against 6 drug-resistant strains, with fractional inhibitory concentration index (FICI) values of 0·133-0·472, 0·123-0·475 and 0·124-0·25, respectively. The IO/RMP, IO/INH and IO/EMB combination treatments had synergistic effects or no interaction in the 2 drug-sensitive strains and the standard strain ATCC 27294. The synergism of combined drugs against drug-resistant strains was better than drug-sensitive strains. No antagonism was observed in with the aforementioned combinations against all strains tested. IO exhibited relatively low cytotoxicity to Vero cells. Our results indicate that IO may serve as promising a template for future antimycobacterial drug development.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report on the in vitro synergistic antimycobacterial effects of isoimperatorin (IO) in combination with three first-line drugs: rifampin (RMP), isoniazid (INH) and ethambutol (EMB). The results indicated that the antimycobacterial activity of IO was modest; however, IO was a useful and effective agent against Myco. tuberculosis when it was combined with first-line antimycobacterial drugs and is worthy of further development as a lead compound for the development of novel antimycobacterial therapeutic agents.

Abstract P2-09-01: Reactivation of epigenetically silenced retinoic acid receptor-beta for therapy of breast cancer- from molecular mechanism to potential clinical applications

Background: Triple negative breast cancer (TNBC) is a subgroup of breast cancer that is characterized by a lack of expression of targets for validated targeted therapies. Although responses to chemotherapy are observed, resistance develops rapidly. Genomic and molecular profiling of TNBC has identified multiple contributors to their uncontrolled growth including epigenetic dysregulation of genes important for normal cell growth and differentiation. Recent studies have shown that histone deacetylase (HDAC) inhibitors reverse the epigenetic profile of tumors, resulting in the re-expression of silenced genes encoding proteins such as ERα, EGFR, and RARβ. Entinostat is an oral, class 1 isoform selective HDACi recently shown in a phase 2 study to be active in ER+ breast cancer. Clinical trials with entinostat in HER2+ and TNBC are also in progress. We hypothesized that combining epigenetic therapy using entinostat, with differentiation therapy using a retinoic acid receptor agonist- All Trans Retinoic Acid (ATRA) will provide an effective strategy for impeding the growth of TNBC and potentially sensitize tumors to commonly used chemotherapies (doxorubicin, carboplatin, paclitaxel).

Methods: Combination studies of entinostat combined with ATRA with and without non-toxic doses (half clinical) of chemotherapy were carried out in vitro and in xenograft models of TNBC. Expression of RARb and downstream effectors were measured in cell lines and tumors from xenograft studies.

Results: Nontoxic (half clinical) doses of doxorubicin when combined with entinostat and ATRA in vitro and in vivo exerted the best response when compared with combinations using paclitaxel and carboplatin. Re-expression of the silenced RARβ and downstream effectors was observed in the cell lines treated in vitro and in tumor xenografts of MDA-MB-231 and SUM159 cells in vivo. To gain insight into mechanism of action for the entinostat – doxorubicin combinations we examined the expression of enzyme targets of doxorubicin and determined that entinostat treatment reduced the expression of topoisomerase (Topo) II enzymes. Besides its conventional role in cell replication and division, Topo II has an important function in regulating transcription, especially in the nuclear receptor pathways such as ER and RAR. Our results demonstrated that Topo IIβ has a dual role in regulating the expression of RARβ. Inhibition of Topo IIβ in a time- and dose dependent manner up-regulated the expression of RARβ and its downstream genes. However, completely eliminating Topo IIβ decreased expression of RARβ.

Conclusions: Our detailed study provides a new approach to treating TNBC using combinations of nontoxic doses of chemotherapeutic drugs with epigenetic therapy, and a deeper understanding of the molecular pathways involved in this response. These results suggest that combination of entinostat and a retinoic acid receptor agonist with low dose doxorubicin will provide an effective strategy for treatment of TNBC.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-09-01.

Abstract P4-06-08: Clinical utility of functional analysis of FGFR kinase family for selecting patients who may benefit from FGFR inhibitors

Background: Fibroblast growth factor receptor (FGFR) family of receptor tyrosine kinases (RTKs) are currently under investigation as therapeutic targets for the treatment of breast cancer. Members of this kinase family have been associated with breast cancer progression and resistance to current therapeutics. FGFR1 amplifications range from 7.5–17% in breast cancers and are associated with a shorter overall survival. FGFR1 amplified cell lines drive activation of AKT, ERK, and RSK and are highly sensitive to FGFR1 inhibition, suggesting an oncogenic addiction to FGFR1. FGFR2 is activated in lapatinib-resistant, HER2-positive cells. Likewise, FGFR3 expression levels are elevated in tamoxifen-resistant, ER positive patients. FGFR 4 overexpression correlated with poor response to chemotherapy due to activation of MAPK and increase in B-cell lymphoma extra large (BCL-XL) levels. Using an immuno-microarray system, this study seeks to determine FGFR signal transduction pathway modulation post FGFR inhibitor treatment in breast cancer cell lines expressing varying levels of FGFR1, 2, 3 or 4.

Method: FGFR 1, 2, 3, and 4 amplified cell lines (MDA-MB-134VI (KRAS), SNU16, RT112, and MDA-MB-453) were treated with varying dosages (1, 10, 100, and 1000nM) of several FGFR inhibitors (AZD4547 (pan FGFR), PD173074 (FGFR1,3) and Ponatinib-AP24534 (FGFR1)) either in presence or absence of corresponding FGF (FGF1, FGF7, FGF9, and FGF19) stimulation. Expression and activation of FGFR 1, 2, 3, and 4 and downstream signaling proteins FRS2, AKT, ERK, MEK, and RSK were measured utilizing a proximity based immuno-microarray.

Results: FGFR1, 2, 3, 4 protein expression was detected in each of the corresponding four FGFR1, 2, 3, 4 amplified cell lines. Total protein levels remained unchanged with or without FGFs stimulation. Levels of FGFR1 phosphorylation increased 5 folds in MDA-MB-134VI stimulated with FGF1. FGFR2 and FGFR3 activation increased by 2–3 folds in SNU16 and RT112 stimulated with FGF7, and FGF9 respectively. FGFR4 activation levels in MDA-MB-453 remained unchanged due to Y367C mutation. ERK was activated in both FGF1 stimulated and unstimulated group in MDA-MB134 due to the KRAS mutation. RSK activation increased in both SNU16 and RT112 when stimulated with FGF7, and FGF9 respectively. FGFR inhibitors treated data analysis is currently in progress and will be presented.

Conclusion: We have demonstrated utility of specific FGFR analysis using well defined model systems. FGFR- profiling should be considered during the clinical work-up in order to select patients who may benefit from regimen containing specific FGFR inhibitors.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-06-08.

FP3: a novel VEGF blocker with antiangiogenic effects in vitro and antitumour effects in vivo

BACKGROUND Vascular endothelial growth factor (VEGF) is a critical promoter of blood vessel growth during embryonic development and neovascularisation in tumours. VEGF serves as a logical target for antiangiogenic cancer therapy because of its fundamental role in tumour angiogenesis. This study is to investigate the inhibitory effects of FP3, a novel VEGF blocker, on angiogenesis in vitro and tumour growth in vivo. METHODS The inhibitory effects of FP3 on angiogenesis in vitro were evaluated by using human umbilical vein endothelial cells (HUVECs) and rat aortic ring. The inhibitory effects of FP3 on tumour growth and angiogenesis in vivo were evaluated in a human non-small-cell lung cancer (NSCLC) cell line A549 tumour xenograft model with the methods of tumour growth regression assay and immunohistochemical staining, respectively. RESULTS In experiments with HUVECs, FP3 inhibited cell proliferation and migration. In rat aortic ring assay, FP3 suppressed VEGF-induced vessel sprouting. In tumour growth regression assay, FP3 significantly blocked the growth of A549 tumour in the subcutaneous tumour xenograft model and dramatically decreased the vessel density of tumour. CONCLUSIONS FP3 has excellent inhibitory effects on tumour angiogenesis both in vitro and in vivo, therefore it could be used as an effective antiangiogenic agent.

Voxel-based morphometric MRI post-processing in MRI-negative focal cortical dysplasia followed by simultaneously recorded MEG and stereo-EEG

We aim to report on the usefulness of a voxel-based morphometric MRI post-processing technique in detecting subtle epileptogenic structural lesions. The MRI post-processing technique was implemented in a morphometric analysis program (MAP), in a 30-year-old male with pharmacoresistant focal epilepsy and negative MRI. MAP gray-white matter junction file facilitated the identification of a suspicious structural lesion in the right frontal opercular area. The electrophysiological data by simultaneously recorded stereo-EEG and MEG confirmed the epileptogenicity of the underlying subtle structural abnormality. The patient underwent a limited right frontal opercular resection, which completely included the area detected by MAP. Surgical pathology revealed focal cortical dysplasia (FCD) type IIb. Postoperatively the patient has been seizure-free for 2 years. This study demonstrates that MAP has promise in increasing the diagnostic yield of MRI reading in challenging patients with "non-lesional" MRIs. The clinical relevance and epileptogenicity of MAP abnormalities in patients with epilepsy have not been investigated systematically; therefore it is important to confirm their pertinence by performing electrophysiological recordings. When confirmed to be epileptogenic, such MAP abnormalities may reflect an underlying subtle cortical dysplasia whose complete resection can lead to seizure-free outcome.

XRCC1 Arg399Gln and Arg194Trp polymorphisms in prostate cancer risk: a meta-analysis

Epidemiological studies have evaluated the association between X-ray repair cross-complementing group 1 gene (XRCC1) Arg399Gln and Arg194Trp polymorphisms and risk of prostate cancer (PCa). However, the results from the published studies on the association between these two XRCC1 polymorphisms and PCa risk are conflicting. To derive a more precise estimation of association between the XRCC1 polymorphisms and risk of PCa, we performed a meta-analysis. A comprehensive search was conducted to identify all case-control studies of XRCC1 polymorphisms and PCa risk. We used odds ratios (ORs) with 95% confidence intervals (CIs) to assess the strength of the association. Overall, we found that both Arg399Gln and Arg194Trp polymorphisms were not significantly associated with PCa risk. However, in stratified analysis by ethnicity, we found that the Arg399Gln polymorphism was significantly associated with PCa risk in Asian population (Gln/Gln vs Arg/Arg: OR=1.46, 95% CI: 1.05-2.03, P=0.03; Gln/Gln vs Arg/Gln+Arg/Arg: OR=1.48, 95% CI: 1.12-1.95, P=0.01). In this meta-analysis, we found that both Arg399Gln and Arg194Trp polymorphisms were not related to overall PCa risk. However, in subgroup analysis we found a suggestion that XRCC1 399Gln allele might be a low-penetrent risk factor for PCa only in Asian men.

Abstract PD05-10: HOXB7 as a Key Regulator in the Development of Tamoxifen Resistance

Multiple factors including long term treatment with tamoxifen are involved in the development of selective estrogen receptor modulator resistance of ERα positive breast cancer. It is well known in the endocrinology field that increased levels of ErbB/HER family members can also directly alter the cellular response to tamoxifen, but the mechanisms underlying increased expression of ErbB/HERs are not clear. In this report we show that HOXB7 is an ERα responsive gene and the downregulation of HOXB7 expression by estradiol is abrogated by tamoxifen in MCF7 cells. HOXB7 overexpression renders MCF-7 cells resistant to tamoxifen via cross-talk between receptor tyrosine kinases and ERα signaling. EGFR and HER2 expression is upregulated by overexpression of HOXB7, while knockdown of HOXB7 with siRNA in tamoxifen-resistant cell lines causes decrease of EGFR and HER2 expression and loss of tamoxifen resistance. In addition, our work demonstrates that to mediate upregulation of EGFR and HER2, HOXB7 binds to ER-alpha and promotes HER2 transcription activity through direct binding to the HER2 enhancer region by competing with other cofactors. Also, HOXB7 enhances EGFR transcription activity via binding to EGFR promoter region. However, depletion of HOXB7 affects the binding affinity of HOXB7 and the cofactors to the HER2 enhancer element. Higher expression levels of HOXB7 significantly correlated with poorer disease free survival in ERα positive breast cancer patients on adjuvant tamoxifen monotherapy. These findings implicate overexpression of HOXB7 as a key event in the initiation and maintenance of tamoxifen resistance. These studies suggest that HOXB7 acts as a key regulator orchestrating two major groups of target molecules in the oncogene heirarchy. Functional antagonism of HOXB7 could circumvent tamoxifen resistance.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr PD05-10.

Transcriptome analysis of the central nervous system of the mollusc Lymnaea stagnalis

Background

The freshwater snail Lymnaea stagnalis (L. stagnalis) has served as a successful model for studies in the field of Neuroscience. However, a serious drawback in the molecular analysis of the nervous system of L. stagnalis has been the lack of large-scale genomic or neuronal transcriptome information, thereby limiting the use of this unique model.

Results

In this study, we report 7,712 distinct EST sequences (median length: 847 nucleotides) of a normalized L. stagnalis central nervous system (CNS) cDNA library, resulting in the largest collection of L. stagnalis neuronal transcriptome data currently available. Approximately 42% of the cDNAs can be translated into more than 100 consecutive amino acids, indicating the high quality of the library. The annotated sequences contribute 12% of the predicted transcriptome size of 20,000. Surprisingly, approximately 37% of the L. stagnalis sequences only have a tBLASTx hit in the EST library of another snail species Aplysia californica (A. californica) even using a low stringency e-value cutoff at 0.01. Using the same cutoff, approximately 67% of the cDNAs have a BLAST hit in the NCBI non-redundant protein and nucleotide sequence databases (nr and nt), suggesting that one third of the sequences may be unique to L. stagnalis. Finally, using the same cutoff (0.01), more than half of the cDNA sequences (54%) do not have a hit in nematode, fruitfly or human genome data, suggesting that the L. stagnalis transcriptome is significantly different from these species as well. The cDNA sequences are enriched in the following gene ontology functional categories: protein binding, hydrolase, transferase, and catalytic enzymes.

Conclusion

This study provides novel molecular insights into the transcriptome of an important molluscan model organism. Our findings will contribute to functional analyses in neurobiology, and comparative evolutionary biology. The L. stagnalis CNS EST database is available at .

A phase II study of bevacizumab (B) and erlotinib (E) in combination for Asian patients (pts) with advanced/metastatic hepatocellular carcinoma (HCC): An interim safety report

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Background: Asian pts with advanced HCC have a poor prognosis, and a median survival of 2–4 months with best supportive care (ph III). As HCCs are highly vascular tumors, dual inhibition of VEGF and EGFR with B plus E is an attractive combination strategy. B has demonstrated promising phase II results in 34 HCC patients, with 75% non-progression at 16 weeks (wks) (65% in Caucasians) (Thomas et al., 2007). However, 6–11% of pts had variceal bleeding, some cases of which were fatal. This study was initiated to investigate the safety and efficacy of B+E in Asian HCC pts. Methods: Screening esophagogastroduodenoscopy (EGD) was used to exclude pts with high risk of variceal bleeding. Asian pts with advanced/metastatic, measurable HCC who were unsuitable for surgery or other loco-regional therapies received B 5mg/kg q2w i.v. and E 150mg/day orally. The primary endpoint was PFS at 16 wks. Responses were evaluated using RECIST. Tumor tissue samples were collected for biomarker analysis. Results: Baseline characteristics of the 51 pts enrolled between March and October 2008 were median age: 58 years (range 26–84); male/female: 44/7; ECOG PS 0/1/2: 30/20/1; Child-Pugh A/B: 50/1; BCLC stage C n=44 (88%); hepatitis B/C/B+C/nonB+nonC: 42/4/3/2; grade I/II varices n=16 (none with red sign). Pts received a median 8 wks of study treatment. No variceal bleeding was observed; 3 pts had upper GI bleeding (grade 1/2; 2 peptic ulcer, 1 gastritis). See table for most common toxicities. 7/10 deaths were due to disease progression, none were due to study treatment. At the time of analysis, 2 pts had a confirmed partial response (PR; duration 24+ and 8+ wks). 1 pt with an unconfirmed PR continued on treatment. Data for the primary analysis were immature. Conclusions: Bevacizumab plus erlotinib was well tolerated. Screening EGD was feasible and reduced the risk of variceal bleeding. Follow-up is ongoing.

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