Abstract B39: A pilot study to establish procedures for DNA and RNA isolation from African esophageal tumor specimens
Authors: Mushi Beatrice Paul , Greer John , Cahalane Charles William , Selekwa Msiba , Mwanga Ali , Akoko Larry , Mmbaga Elia , Collisson Eric , Loon Katherine Van 
Published: December 2017

Objective: We propose to utilize tumor biospecimens from patients with esophageal squamous cell carcinoma (ESCC) to identify possible genetic, molecular, and infectious determinants of this high-incidence disease in East Africa. However, laboratory technologies in East Africa are not available to support DNA and RNA extraction and genome and transcriptome sequencing from patient specimens. In preparation for establishment of a biorepository for African ESCC specimens, we compared different fixation and preservation media for transportability over long distances and success in preserving the genetic integrity and expression profiles of ESCC.

Methods: Patients with a suspected diagnosis of ESCC at Muhimbili National Hospital in Dar es Salaam, Tanzania were identified and consented prior to endoscopic evaluations. For patients with endoscopic findings consistent with ESCC, tumor biopsies were obtained and stored using two different fixation and preservation media: PAXgene® Tissue Container (n=2) and RNAlater® (n=2). All specimens were shipped at room temperature from Dar es Salaam to San Francisco. DNA and RNA quantity was measured by nanodrop method and DNA was further confirmed by picogreen method, yielding measures of total DNA and RNA acquired (ug). DNA quality was measured as percent of total DNA degradation to between 200-1000 bp. RNA quality measure was determined by bioanalyzer output measure RNA Integrity Number (RIN).

Results: Specimens for our first 10 patients were analyzed. Average transit time of biopsy specimens in preservative at room temperature was 6.2 days (range 3.5-9.0). Tumor specimens preserved with PAXgene® yielded a mean of 7.7 ug total DNA and 8.6 ug total RNA. Tumor specimens preserved with RNAlater® yielded a mean 1.4 ug of DNA and 8.2 ug of RNA. DNA degradation products were 0% of total with PAXgene® versus 6% of total with RNAlater®. Specimens preserved with PAXgene® yielded a mean RIN of 4, while RNAlater® yielded a mean RIN of 9. DNA and RNA quality were not associated with length of time at room temperature, up to a maximum of 9 days.

Conclusion: Tissue preserved using the PAXgene® Tissue Container yielded higher DNA quantity and quality than tissue preserved in RNAlater®. RNA quantity was comparable for both mediums, but RNAlater® resulted in superior RNA quality versus PAXgene®. Both mediums allowed for flexible transport of specimens at room temperature and merit further inquiry into their potential as cost-effective methods to facilitate molecular analyses for geographically isolated diseases in Africa. Based upon our pilot data, each medium offers unique advantages. Our expanded study will continue to utilize both mediums to optimize isolation of both DNA and RNA. We will plan to present data for an enriched sample size.

Funding source: National Institutes of Health, National Cancer Institute Cancer Center Administrative Supplement to Promote Cancer Prevention and Control Research in Low and Middle Income Countries, A119617, [CA-0082629].

Citation Format: Beatrice Paul Mushi, John Greer, Charles William Cahalane, II, Msiba Selekwa, Ali Mwanga, Larry Akoko, Elia Mmbaga, Eric Collisson, Katherine Van Loon. A pilot study to establish procedures for DNA and RNA isolation from African esophageal tumor specimens [abstract]. In: Proceedings of the AACR International Conference: New Frontiers in Cancer Research; 2017 Jan 18-22; Cape Town, South Africa. Philadelphia (PA): AACR; Cancer Res 2017;77(22 Suppl):Abstract nr B39.