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.

Re-expression of CXCL14, a common target for epigenetic silencing in lung cancer, induces tumor necrosis

Chemokines are important regulators of directional cell migration and tumor metastasis. A genome-wide transcriptome array designed to uncover novel genes silenced by methylation in lung cancer identified the CXC-subfamily of chemokines. Expression of eleven of the sixteen known human CXC-chemokines was increased in lung adenocarcinoma cell lines after treatment with 5-aza-2deoxycytidine (DAC). Tumor-specific methylation leading to silencing of CXCL5, 12 and 14 was found in over 75% of primary lung adenocarcinomas and DAC treatment restored expression of each silenced gene. Forced expression of CXCL14 in H23 cells where this gene is silenced by methylation increased cell death in vitro and dramatically reduced in vivo growth of lung tumor xenografts through necrosis of up to 90% of the tumor mass. CXCL14 re-expression had a profound effect on the genome altering the transcription of over 1,000 genes, including increased expression of 30 cell cycle inhibitor and pro-apoptosis genes. In addition, CXCL14 methylation in sputum from asymptomatic early stage lung cancer cases was associated with a 2.9-fold elevated risk for this disease compared to controls, substantiating its potential as a biomarker for early detection of lung cancer. Together these findings identify CXCL14 as an important tumor suppressor gene epigenetically silenced during lung carcinogenesis.

Aberrant methylation and impaired expression of the p15(INK4b) cell cycle regulatory gene in chronic myelomonocytic leukemia (CMML)

The important cell cycle regulatory gene p15(INK4b) has been shown to be inactivated in acute myeloid leukemia and myelodysplastic syndrome. Little is known about the expression and epigenetic modification of this gene in chronic myelomonocytic leukemia (CMML) that belongs to the myelodysplastic/myeloproliferative disorders (MDS/MPD) with a high proportion of blastic transformation. Analysis of bone marrow trephines in a series of 33 CMML cases showed an aberrant p15(INK4b) gene methylation in up to 58% of cases. Methylation was analyzed employing different methylation-specific PCR and genomic sequencing protocols. It turned out to be spread over a broad area of the 5' region and exhibited substantial heterogeneity between cases and even in individual patients. The degree of aberrant methylation was correlated with a reduced mRNA as well as reduced protein expression, and was associated with a higher expression of DNA methyltransferase DNMT 3A. We conclude that aberrant gene methylation is a frequent event in CMML that might contribute to the pathogenesis of this MDS/MPD.