Introduction: Gastric cancer (GC) is the second leading cause of cancer-related death in the world and the most common cancer in southeast of Caspian Sea (Golestan province) and northwest of Iran (Ardabil). Based on cancer stem cell (CSC) hypothesis, there are similarities between process of somatic cell reprogramming, embryogenesis and tumorigenesis. Malfunction of signaling pathways that are essential for normal development also involved in the tumor initiation and CSC formation. In recent years long noncoding RNAs (lncRNAs), more than 200 nt in length, have been highly regarded as promising biomarkers for early diagnosis and prognosis of cancers. Reprogramming-Related Long Intergenic Noncoding RNA (lincRNA-ROR) plays as modulator in the reprogramming of human induced pluripotent stem cells (iPSCs) and also maintenance of embryonic stem cells (ESCs). On the other hand, lincRNA-P21 induced by P53 and prevents the somatic cell reprogramming by silencing of pluripotency gene promoters. In this project, motivate to CSCs, we evaluated the expression level of lincRNA-ROR and linc-P21 in samples of patients with gastric cancer and also in human gastric cancer cell lines (AGS and MKN45) and human embryonal carcinoma cell line (NT2).

Methods: Thirty pairs of gastric samples, including gastric adenocarcinoma and their matched non-tumor tissue samples, were collected from the Iran National Tumor Bank (INTB). Cell lines were cultured in the RPMI1640. Total RNA of samples and cell lines was extracted using TRIZOL reagent (invitrogene). cDNA synthesis was performed by PrimeScript™ 1st strand cDNA Synthesis Kit (TAKARA) and real time PCR was performed by using TaqMan master mix (TAKARA) on Step one Plus™ instrument (ABI). Gene expression analysis performed by GenEx software program.

Results: Despite of reports indicating the high expression of linc-ROR in some cancers, our results showed no expression for linc-ROR in gastric samples (both tumor and non tumor) and also gastric cancer cell lines. But NT2 embryonal carcinoma cell line revealed high expression of linc-ROR compared to AGS and MKN45cell lines. According to our expectation, linc-P21 represents a significant decrease in tumor versus non tumor samples (p<0.01) in different grads of malignancy and also in AGS and MKN45 versus to NT2 cell line.

Conclusion: Dysfunction of linc-ROR and lincRNA-P21 has reported in some cancers. According to our results, it seems that the expression of linc-ROR is limited to embryonic stem cells and hasn’t remarkable expression in gastric samples and cell lines. Based on the low expression of linc-P21 in tumor samples, it seems that linc-P21 functions as a tumor suppressor.

Citation Format: Mitra Khalili, Pourandokht Farhangiyan, Somayeh Jahandoost, Fatemeh Kamali. The expression of two key long non coding RNAs involved in reprogramming, linc-ROR and lin-P21, in gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3505. doi:10.1158/1538-7445.AM2017-3505