ROLES OF 15-LIPOXYGENASE-2 (ALOX15B) IN SUPPRESSION OF TUMOR FORMATION, METASTASIS, AND SENSITIVITY TO CHEMOTHERAPY

Author

Rana Alfardan, Southern Illinois University CarbondaleFollow

Date of Award

5-1-2018

Degree Name

Doctor of Philosophy

Department

Molecular Biology, Microbiology and Biochemistry

First Advisor

Nie, Daotai

Abstract

15-LOX-2 is a member of the lipoxygenase family with anti-tumorigenic activity. Like other lipoxygenase families, the main substrate for 15-LOX-2 in the Arachidonic acid. The main product of this enzyme is 15(S)-HETE. 15(S)-HETE control the proliferation in prostate cells. The expression of 15-LOX-2 lost in the metastatic stage of prostate tumor compared to the primary and benign tumor. To investigate the role of 15-LOX-2 in a highly metastatic prostate tumor, we overexpressed 15-LOX-2 in PC3MM cell line using Lenti-X Tet-on advanced inducible expression system. Exposure to 75ng/ml of doxycycline for 24h produced prompt 15-LOX-2 at the protein level. In addition, removing the inducible molecule for 72h halted the 15-LOX-2 expression. After induction of 15-LOX-2 for 96h, the cells started to have more epithelial-like phenotypes compared to the untreated or vector control cells. The cells with 15-LOX-2 induction have a bigger and flattened shape with less cytoplasmic extension compared to the untreated and vector control cells. Overexpression of 15-LOX-2 led to reverse the epithelial to mesenchymal process. 15-LOX-2 overexpression led to increasing the expression of junctional complex structural proteins. However, 15-LOX-2 overexpression led to decrease the expression of the mesenchymal markers and matrix metalloproteases. In addition, we proved the ability of 15-LOX-2 to inhibit the tumor growth in vivo and increase the chemotherapy sensitivity in vitro. To investigate the biological role of 15-LOX-2 in vivo, we used mice with a deletion in the ALOX8 (15-LOX-2 orthologue in mice). Mice with a deletion in ALOX8 showed increased in the formation of mass like a tumor in the lung, and chronic inflammation compared to the wildtype. In addition, the infection of these mice with X31 virus indicated an important role for ALOX8 in the recovery process after infection with influenza virus.