Abstract 1948: Shared and distinct microRNA-expression alterations in lung adenocarcinoma from smokers vs. nonsmokers.
Authors: Wang Teresa , Campbell Joshua , Kusko Rebecca , Luo Lingqi , Tellez Carmen , Liu Gang , Xiao Ji , Lenburg Marc , Belinsky Steven , Spira Avrum 
Published: August 2014

Rationale: While lung adenocarcinoma (ADC) is predominantly associated with the exposure to tobacco smoke, 10-15% of cases arise in never smokers. Small non-coding RNAs such as microRNAs (miRNAs) often act as oncogenes or tumor suppressors to regulate gene expression during disease, and may provide the critical insight needed to address the clinical and molecular disparities consistently observed in ADC of smokers and never smokers. We therefore sought to characterize the similarities and differences in the tumor-associated miRNA transcriptome between lung tumors from active, former, and never smokers.

Methods: Total RNA was isolated from paired lung adenocarcinomas (purity ≥ 70%) and adjacent-normal lung tissues resected from 32 subjects with varied smoking statuses (n=8 active; n=11 former; n=13 never). Subjects were matched for gender and age. Small RNA libraries were generated and multiplexed 7-8 per lane for sequencing on the Illumina HiSeq 2000. Through a custom miRNA sequencing analysis pipeline, reads were trimmed, size-selected, and mapped to hg19 using Bowtie. Counts per mature miRNA from aligned reads were computed using Bedtools and a list of genomic features retrieved from miRBase v17. Differential expression analysis was conducted using a likelihood ratio test between two linear models: one adjusting for tumor and smoking status, another with an additional interaction term.

Results: Small RNA sequencing generated an average of 10 million high quality miRNA reads per sample. Among the 1906 mature miRNAs examined, 554 miRNAs had at least an average of 20 counts across all samples. We identified 97 miRNAs (q&lt;0.0001) were differentially expressed between tumor and the adjacent-normal tissue, independent of smoking status. Importantly, we also identified 30 miRNAs (p&lt;0.05) whose expression levels between tumor and the adjacent-normal tissue varied with smoking status. This included miR-1246, miR-1307 and miR-320b, which were up-regulated in the tumor versus adjacent-normal of current and former smokers, but relatively unchanged in never smokers, suggesting that these microRNAs are involved in smoking-specific cancer pathogenesis.

Conclusions: Using small RNA sequencing, we have identified miRNAs that are markedly dysregulated in primary lung ADC tissues as compared to their histologically normal, adjacent counterparts. Subsets of these profiles are both shared and distinct between lung cancer cases that arise in smokers and nonsmokers. The ongoing integration of miRNA and large RNA sequencing data generated from these samples will inform our understanding of mechanisms that are specific to carcinogenesis in the presence or absence of tobacco smoke exposure. These results may yield novel targeted therapies for smoking or nonsmoking-specific ADC subtypes.

Citation Format: Teresa Wang, Joshua Campbell, Rebecca Kusko, Lingqi Luo, Carmen Tellez, Gang Liu, Ji Xiao, Marc Lenburg, Steven Belinsky, Avrum Spira. Shared and distinct microRNA-expression alterations in lung adenocarcinoma from smokers vs. nonsmokers. [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 1948. doi:10.1158/1538-7445.AM2013-1948