Semester

Summer

Date of Graduation

2020

Document Type

Dissertation

Degree Type

PhD

College

School of Medicine

Committee Chair

Elena Pugacheva

Committee Member

Scott Weed

Committee Member

Linda Vona-Davis

Committee Member

Erik Bey

Committee Member

Heath Damron

Abstract

Non-small cell lung cancer (NSCLC) is the number one cause of cancer related mortality in the United States and worldwide. Advanced and therapeutically resistant lung tumors contribute to the high rate of mortality from NSCLC, therefore there is a need for new methods of diagnosing and treating this disease. Long non-coding RNAs (lncRNAs) have been shown to be a crucial component of human molecular biology, regulating nearly every cellular pathway from chromatin condensation to transcription and translation. Furthermore, many lncRNAs have been classified as oncogenes or tumor suppressors, highlighting the various molecular mechanisms they are involved in regarding the formation and progression of cancer and their use as prognostic and diagnostic biomarkers has been proposed in numerous cancers, including NSCLC.

Our group has discovered, for the first time, a three member family of Y chromosome lncRNAs (linc-SPRY3-2, lin-SPRY3-3, and linc-SPRY3-4) which regulate NSCLC cell response to ionizing radiation (IR). Briefly, the linc-SPRY3 family demonstrated a dose dependent induction of expression following exposure to IR in male radiosensitive NSCLC cell lines, but not in male radioresistant cell lines. This difference was revealed to be due to loss of the Y chromosome in the radioresistant cell lines. Using gain-of-function and loss-of-function experiments, we demonstrated statistically significant changes in cell viability and apoptosis in vitro. Furthermore, in vivo tumor growth delay assays showed a more radioresistant phenotype in tumors with knockdown of the linc-SPRY3 RNAs versus control tumors. We hypothesize linc-SPRY3-2/3/4 mediate their tumor suppressive effect via sequestration of the RNA binding protein IGF2BP3 demonstrated by CLIP and RNA degradation assays. Moreover, DNA FISH and bioinformatic analysis revealed a trending negative correlation in patient survival between loss of the Y chromosome and linc-SPRY3-2/3/4. These findings suggest that the linc-SPRY3 RNAs function as tumor suppressors by promoting cell death following IR through interactions with IGF2BP3, and could have potential as biomarkers in male NSCLC.

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