Marcie J. Grimes

Predicting gene promoter methylation in non-small-cell lung cancer by evaluating sputum and serum

The use of 5-methylcytosine demethylating agents in conjunction with inhibitors of histone deacetylation may offer a new therapeutic strategy for lung cancer. Monitoring the efficacy of gene demethylating treatment directly within the tumour may be difficult due to tumour location. This study determined the positive and negative predictive values of sputum and serum for detecting gene methylation in primary lung cancer. A panel of eight genes was evaluated by comparing methylation detected in the primary tumour biopsy to serum and sputum obtained from 72 patients with Stage III lung cancer. The prevalence for methylation of the eight genes in sputum (21–43%) approximated to that seen in tumours, but was 0.7–4.3-fold greater than detected in serum. Sputum was superior to serum in classifying the methylation status of genes in the tumour biopsy. The positive predictive value of the top four genes (p16, DAPK, PAX5 β, and GATA5) was 44–72% with a negative predictive value for these genes ⩾70%. The highest specificity was seen for the p16 gene, and this was associated with a odds ratio of six for methylation in the tumour when this gene was methylated in sputum. In contrast, for serum, the individual sensitivity for all genes was 6–27%. Evaluating the combined effect of methylation of at least one of the four most significant genes in sputum increased the positive predictive value to 86%. These studies demonstrate that sputum can be used effectively as a surrogate for tumour tissue to predict the methylation status of advanced lung cancer where biopsy is not feasible.

Combination Therapy with Vidaza and Entinostat Suppresses Tumor Growth and Reprograms the Epigenome in an Orthotopic Lung Cancer Model

Epigenetic therapy for solid tumors could benefit from an in vivo model that defines tumor characteristics of responsiveness and resistance to facilitate patient selection. Here we report that combining the histone deacetylase inhibitor entinostat with the demethylating agent vidaza profoundly affected growth of K-ras/p53 mutant lung adenocarcinomas engrafted orthotopically in immunocompromised nude rats by targeting and ablating pleomorphic cells that occupied up to 75% of the tumor masses. A similar reduction in tumor burden was seen with epigenetic therapy in K-ras or EGFR mutant tumors growing orthotopically. Increased expression of proapoptotic genes and the cyclin-dependent kinase inhibitor p21 was seen. Hundreds of genes were demethylated highlighted by the reexpression of polycomb-regulated genes coding for transcription factor binding proteins and the p16 gene, a key regulator of the cell cycle. Highly significant gene expression changes were seen in key regulatory pathways involved in cell cycle, DNA damage, apoptosis, and tissue remodeling. These findings show the promise for epigenetic therapy in cancer management and provide an orthotopic lung cancer model that can assess therapeutic efficacy and reprogramming of the epigenome in tumors harboring different genetic and epigenetic profiles to guide use of these drugs.

SGI-110 and entinostat therapy reduces lung tumor burden and reprograms the epigenome

The DNA methyltransferase (DNMT) inhibitor vidaza (5‐Azacytidine) in combination with the histone deacetylase inhibitor entinostat has shown promise in treating lung cancer and this has been replicated in our orthotopic lung cancer model. However, the effectiveness of DNMT inhibitors against solid tumors is likely impacted by their limited stability and rapid inactivation by cytidine deaminase (CDA) in the liver. These studies were initiated to test the efficacy of SGI‐110, a dinucleotide containing decitabine that is resistant to deamination by CDA, as a single agent and in combination with entinostat. Evaluation of in vivo plasma concentrations and pharmacokinetic properties of SGI‐110 showed rapid conversion to decitabine and a plasma half‐life of 4 hr. SGI‐110 alone or in combination with entinostat reduced tumor burden of a K‐ras/p53 mutant lung adenocarcinoma cell line (Calu6) engrafted orthotopically in nude rats by 35% and 56%, respectively. SGI‐110 caused widespread demethylation of more than 300 gene promoters and microarray analysis revealed expression changes for 212 and 592 genes with SGI‐110 alone or in combination with entinostat. Epigenetic therapy also induced demethylation and expression of cancer testis antigen genes that could sensitize tumor cells to subsequent immunotherapy. In the orthotopically growing tumors, highly significant gene expression changes were seen in key cancer regulatory pathways including induction of p21 and the apoptotic gene BIK. Moreover, SGI‐110 in combination with entinostat caused widespread epigenetic reprogramming of EZH2‐target genes. These preclinical in vivo findings demonstrate the clinical potential of SGI‐110 for reducing lung tumor burden through reprogramming the epigenome.

Rosiglitazone prevents the progression of preinvasive lung cancer in a murine model

There is a critical need to identify efficacious chemopreventive agents for lung cancer that can be taken chronically with no side effects and whose mechanisms of action do not involve genotoxicity that could drive, rather than impede, cancer progression. We evaluated the ability of a chemopreventive cocktail that included selenium (antioxidant), rosiglitazone (peroxisome proliferator-activated receptor gamma agonist), sodium phenylbutyrate or valproic acid (histone deacetylase inhibitors) and hydralazine (cytosine-demethylating agent) to prevent the progression of lung cancer in A/J mice treated with NNK. Agents were administered alone or in various combinations. Effects of the chemopreventive agents were quantified based on the proportion of hyperplasias and adenomas within the mouse lung. Significant effects on tumor progression were seen in all treatment groups that included rosiglitazone as reflected by a 47-57% increase in number of hyperplasias and a 10-30% decrease in adenomas. Cell proliferation was also reduced in these treatment groups by approximately 40%. Interestingly, while treatment with rosiglitazone alone did not significantly affect lesion size, striking effects were seen in the combination therapy group that included sodium phenylbutyrate, with the volume of hyperplasias and adenomas decreasing by 40 and 77%, respectively. These studies demonstrate for the first time that chronic in vivo administration of rosiglitazone, used in the management of diabetes mellitus, can significantly block the progression of premalignant lung cancer in the A/J mouse model.

Differential Epigenetic Regulation of TOX Subfamily High Mobility Group Box Genes in Lung and Breast Cancers

Aberrant cytosine methylation affects regulation of hundreds of genes during cancer development. In this study, a novel aberrantly hypermethylated CpG island in cancer was discovered within the TOX2 promoter. TOX2 was unmethylated in normal cells but 28% lung (n = 190) and 23% breast (n = 80) tumors were methylated. Expression of two novel TOX2 transcripts identified was significantly reduced in primary lung tumors than distant normal lung (p<0.05). These transcripts were silenced in methylated lung and breast cancer cells and 5-Aza-2-deoxycytidine treatment re-expressed both. Extension of these assays to TOX, TOX3, and TOX4 genes that share similar genomic structure and protein homology with TOX2 revealed distinct methylation profiles by smoking status, histology, and cancer type. TOX was almost exclusively methylated in breast (43%) than lung (5%) cancer, whereas TOX3 was frequently methylated in lung (58%) than breast (30%) tumors. TOX4 was unmethylated in all samples and showed the highest expression in normal lung. Compared to TOX4, expression of TOX, TOX2 and TOX3 in normal lung was 25, 44, and 88% lower, respectively, supporting the premise that reduced promoter activity confers increased susceptibility to methylation during lung carcinogenesis. Genome-wide assays revealed that siRNA-mediated TOX2 knockdown modulated multiple pathways while TOX3 inactivation targeted neuronal development and function. Although these knockdowns did not result in further phenotypic changes of lung cancer cells in vitro, the impact on tissue remodeling, inflammatory response, and cell differentiation pathways suggest a potential role for TOX2 in modulating tumor microenvironment.

Aerosolised 5-azacytidine suppresses tumour growth and reprogrammes the epigenome in an orthotopic lung cancer model

Background:Epigenetic silencing by promoter methylation and chromatin remodelling affects hundreds of genes and is a causal event for lung cancer. Treatment of patients with low doses of the demethylating agent 5-azacytidine in combination with the histone deacetylase inhibitor entinostat has yielded clinical responses. The subcutaneous dosing route for consecutive days and reduced bioavailability of 5-azacytidine because of inactivation by cytidine deaminase may limit the expansion of epigenetic therapy into Phase III trials. To mitigate these barriers, an aerosol of 5-azacytidine was generated and characterised.Methods:The effect of aerosol vs systemic delivery of 5-azacytidine on tumour burden and molecular response of engrafted lung tumours in the nude rat was compared.Results:Pharmacokinetics revealed major improvement in the half-life of 5-azacytidine in lung tissue with aerosol delivery. Aerosolised 5-azacytidine significantly reduced lung tumour burden and induced global demethylation of the epigenome at one-third of the comparable effective systemic dose. High commonality for demethylation of genes was seen in tumours sampled throughout lung lobes and across treated animals receiving the aerosolised drug.Conclusion:Collectively, these findings show that aerosolised 5-azacytidine targets the lung, effectively reprogrammes the epigenome of tumours, and is a promising approach to combine with other drugs for treating lung cancer.

Inhalation delivery of topotecan is superior to intravenous exposure for suppressing lung cancer in a preclinical model

Abstract Intravenous (IV) topotecan is approved for the treatment of various malignancies including lung cancer but its clinical use is greatly undermined by severe hematopoietic toxicity. We hypothesized that inhalation delivery of topotecan would increase local exposure and efficacy against lung cancer while reducing systemic exposure and toxicity. These hypotheses were tested in a preclinical setting using a novel inhalable formulation of topotecan against the standard IV dose. Respirable dry-powder of topotecan was manufactured through spray-drying technology and the pharmacokinetics of 0.14 and 0.79 mg/kg inhalation doses were compared with 0.7 mg/kg IV dose. The efficacy of four weekly treatments with 1 mg/kg inhaled vs. 2 mg/kg IV topotecan were compared to untreated control using an established orthotopic lung cancer model for a fast (H1975) and moderately growing (A549) human lung tumors in the nude rat. Inhalation delivery increased topotecan exposure of lung tissue by approximately 30-fold, lung and plasma half-life by 5- and 4-folds, respectively, and reduced the maximum plasma concentration by 2-fold than the comparable IV dose. Inhaled topotecan improved the survival of rats with the fast-growing lung tumors from 7 to 80% and reduced the tumor burden of the moderately-growing lung tumors over 5- and 10-folds, respectively, than the 2-times higher IV topotecan and untreated control (p < .00001). These results indicate that inhalation delivery increases topotecan exposure of lung tissue and improves its efficacy against lung cancer while also lowering the effective dose and maximum systemic concentration that is responsible for its dose-limiting toxicity.

Abstract 679: SGI-110 and entinostat therapy reduces lung tumor burden and reprograms the epigenome .

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC The DNA methyltransferase inhibitors (DNMTi) Vidaza (5-azacytidine) and Dacogen (5-aza-2′-deoxycytidine, decitabine) are approved by the FDA for chemotherapy against myelodysplastic syndrome, a heterogeneous bone marrow disorder. Vidaza in combination with the HDAC inhibitor entinostat has shown some promise in treating lung cancer and this has been replicated in our orthotopic lung cancer model. However, the effectiveness of these DNMTi against solid tumors is likely impacted in part, by their stability and rapid inactivation by cytidine deaminase in the liver. These studies were initiated to test the efficacy of SGI-110, a prodrug for decitabine. SGI-110, a dinucleotide consisting of 5-aza-2′-deoxycytidine followed by a deoxyguanosine, has been shown to be effective in vitro as a DNA methylation inhibitor and less prone to deamination by cytidine deaminase. In this study, we used our in vivo lung cancer model to explore the potential therapeutic effect of SGI-110 alone and in combination with entinostat. In vivo plasma concentrations and pharmacokinetic properties of SGI-110 and its metabolite decitabine were evaluated in nude rats after a single SC dose of SGI-110. Upon SC administration, SGI-110 is rapidly converted to decitabine. Dose proportional pharmacokinetics showed no significant difference in accumulation of SGI-110 or decitabine, while the half life of decitabine was increased to 4hrs. SGI-110 alone or in combination with entinostat significantly reduced tumor burden by 56% of Calu-6, a K-ras/p53 mutant lung adenocarcinoma cell line engrafted orthotopically in nude rats. On a molecular level, global changes in gene profiles were associated with a reduction in tumor burden. Microarray analysis revealed that a 212 and 592 genes were differentially expressed in SGI-110 alone or with combination therapy. Highly significant gene expression changes were seen in key cancer regulatory pathways. In addition, SGI-110 treatment activated p21 and apoptotic genes BIK and BAK in these tumors. SGI-110 caused widespread epigenetic reprogramming that induced demethylation of an average of 291 genes; in particular 208 genes were polycomb target genes. The polycomb targets were enriched for transcription factors. These preclinical in vivo findings demonstrate that SGI-110 alone shows strong demethylating activity and when combined with entinostat more effectively retards tumor growth. (Supported by Astex Pharmaceutical and SU2C) Citation Format: Carmen S. Tellez, Marcie J. Grimes, Maria A. Picchi, Yushi Liu, Tom H. March, Aram Oganesian, Pietro Taverna, Steven A. Belinsky. SGI-110 and entinostat therapy reduces lung tumor burden and reprograms the epigenome . [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 679. doi:10.1158/1538-7445.AM2013-679