Abstract B32: Longitudinal changes in plasma miRNA in patients with benign and malignant colorectal neoplasia
Authors: Carter Jane , States Vanessa , Netz Uri , Pan Jianmin , Rai Shesh , Galandiuk Susan 
Published: May 2016

Introduction: The adenoma-carcinoma sequence is well-recognized as a stepwise pattern of mutational activation of oncogenes and inactivation of tumor suppressor genes resulting in sporadic colorectal cancer (CRC) development from colorectal adenomas (CRA) within the chromosomal instability pathway. MicroRNAs (miRNA) play an important role in oncogenesis by regulating gene expression and are known to be actively released from cells. They are found in body fluids such as plasma, saliva, feces and urine. We have previously demonstrated differential expression of plasma miRNAs in patients with CRC as compared to that of controls.

Methods: Plasma was isolated from 10 patients: 5 patients with advanced colorectal adenoma (&gt;0.6cm diameter) and 5 patients with stage II or III colorectal cancer prior to treatment and 4-6 weeks following endoscopic removal or surgical resection, respectively. RNA was extracted from plasma (Qiagen® miRNeasy), RT-PCR performed and 768 miRNAs were screened using microfluidic array technology (Applied BioSystems®) in pre- and post-treatment samples for each patient. Data were analyzed using paired t-tests after normalizing raw cycle threshold data to endogenous RNU6 for pre- and post-treatment samples. In addition, miRNA expression data from both pre- and post-treatment CRA and CRC samples were compared to that of plasma from 10 individuals without neoplasia (controls) (ANOVA).

Results: Significant differential expression of plasma miRNAs was observed between pre- and post-treatment samples in both CRA and CRC groups. Interestingly, there was generalized miRNA upregulation in CRA when comparing pre-treatment samples to post-treatment samples. Conversely there was miRNA down-regulation in pre-treatment CRC plasma as compared to post-resection samples. Utilizing significantly dysregulated miRNAs, as well as p-values, AUC, fold-change and biological significance, miRNA panels were selected to facilitate detection of CRA recurrence (following complex polypectomy for large polyps) or for detection of recurrent CRC following resection. The resulting panel was able to differentiate between pre- and post-treatment samples for CRA (miR-186 and miR-623) with AUC 0.94 (95% CI 0.76 – 1.00) and for CRC (miR-324-5p, miR-30d and miR-766) with AUC 0.88 (95% CI 0.63 – 1.00). In addition, while miRNA expression of pre-treatment CRA and CRC samples differed significantly from controls, post-treatment CRA and CRC samples did not.

Conclusion: Comparison of pre- and post-treatment plasma samples reveals differing patterns of changes in miRNA expression in benign colorectal neoplasms (CRA) as opposed to invasive neoplasia (CRC). The observed miRNA down-regulation prior to surgical resection of CRC might indicate decreased expression of miRNAs inhibiting oncogenes prior to cancer treatment, while the miRNA upregulation seen in pre-treatment CRA plasma could indicate inhibition of tumor suppressors. Such observations will perhaps elucidate the role of miRNA in carcinogenesis and may provide for a relatively non-invasive method of detecting such lesions. Further validation is needed to develop a miRNA panel that will allow monitoring for evidence of recurrent disease.

Citation Format: Jane Carter, Vanessa States, Uri Netz, Jianmin Pan, Shesh Rai, Susan Galandiuk. Longitudinal changes in plasma miRNA in patients with benign and malignant colorectal neoplasia. [abstract]. In: Proceedings of the AACR Special Conference on Noncoding RNAs and Cancer: Mechanisms to Medicines ; 2015 Dec 4-7; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2016;76(6 Suppl):Abstract nr B32.