Abstract A04: LINC00467 regulates the autophagy signaling pathway STK11/AMPK

Abstract

Abstract Mounting evidence has established a fundamental role of autophagy (a self-digestion process) in tumor initiation and progression. Hence, targeting autophagy is a promising strategy for developing effective therapies to treat cancer. In our previous genome-wide RNA interference screen, we identified a set of genes that regulate autophagy in human chronic myeloid leukemia K562 cells. One of the candidates is LINC00467 (long intergenic noncoding RNA 00467), a long non-coding RNA (LncRNA) known for apoptosis regulation in neuroblastoma. LncRNA is a new RNA species with important role in gene expression regulation. Although the role of LncRNAs in apoptosis has been extensively studied. Whether or how LncRNA regulate autophagy has not yet been explored. Our previous work has established that LINC00467 regulates autophagy in different types of cancers. However, how LINC00467 regulates autophagy is largely unknown. To address this question, we first determined the stage of autophagy LINC00467 targets using a combination treatment of LINC00467 depletion and chloroquine and measuring the protein level of p62. We then monitored the activity of STK11/AMPK and MTOR, two autophagy signaling pathways, in K562 cells upon inhibition of LINC00467. We found that shRNA knockdown of LINC00467 in conjunction with chloroquine treatment significantly induced the formation of autophagic compartments manifested by the increase of Cyto-ID fluorescence. Moreover, LINC00467 knockdown substantially decreased the protein level of P62. These results indicate that Linc00467 suppresses the initiation of autophagy. To further probe the mechanism, we measured the activity of autophagy-promoting kinases STK11/AMPK, and autophagy-inhibiting kinase MTOR. Our results showed that Linc00467 knockdown substantially enhanced the activity/expression of STK11/AMPK while inhibiting that of MTOR, consistent with the inhibition of BCR-ABL using imatinib. Furthermore, We showed that LINC00467 inhibition led to a delayed degradation of STK11 mRNA. Taken together, our data demonstrates that LINC00467 suppresses autophagy through blocking STK11/AMPK. These results not only reveal a new LINC00467/STK11/AMPK pathway in autophagy regulation but also provide a basis for future therapeutic development. Citation Format: Sujuan Guo, Kevin Pridham, Zhi Sheng. LINC00467 regulates the autophagy signaling pathway STK11/AMPK. [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 A04.