Abstract 1437: De novo fatty acid synthesis-driven sphingolipid metabolism promotes metastatic potential of colorectal cancer
Authors: Jafari Naser , Drury James , Morris Andrew J. , Onono Fredrick O. , Stevens Payton D. , Gao Tianyan , Lee Eun Y. , Weiss Heidi L. , Evers B Mark , Zaytseva Yekaterina 
Published: August 2018

Colorectal cancer (CRC) is the second leading cause of cancer-related deaths in the USA. Development of metastasis is the most common cause of death in these patients. Fatty acid synthase (FASN) and Sphingosine Kinases 1 and 2 (SPHK1 and 2) are overexpressed in many cancers, including CRC. However, the contribution of FASN-mediated upregulation of sphingolipid metabolism to CRC metastasis and potential of these pathways as targets for therapeutic intervention remains unknown. The purpose of this study was to determine (i) expression of FASN, SPHK1 and SPHK2 in human CRC tissues, (ii) the effect of upregulation of FASN on sphingolipid metabolism and (iii) functional significance of the FASN/SPHK axis in advanced CRC.

Methods: Expression of FASN, SPHK1 and SPHK2 was assessed in a CRC tumor microarray (matched normal colon and tumor; 56 cases) by immunohistochemistry. Sphingolipids were measured by mass spectrometry. Primary CRC cells were established from CRC patient-derived xenograft (PDX) tumors and treated with TVB-3664, a novel FASN inhibitor, or FTY-720, an S1P mimetic that inhibits SPHKs and S1P receptors. Cellular proliferation was measured using a cell counter. Migration capabilities of cells were assessed by live cell imaging using Nikon BioStation. Invadopodia and focal adhesions were assessed by total internal reflection fluorescence microscopy. Tumor tissues were implanted into 6 to 8-week-old NOD scid gamma mice to establish PDX models. Expression of proteins involved in adhesion, migration and invasion were assessed by western blot.

Results: SPHK1 and SPHK2 were overexpressed in CRC as compared to normal mucosa and expression of FASN correlates with expression of SPHK2 (Spearman's r=0.27894, p=0.0374). Furthermore, FASN and SPHKs co-localized within invadopodia of primary CRC cells. Moreover, FASN inhibition decreased expression of SPHK2 and the level of Sphingosine-1-phosphate (S1P) in primary and established CRC cells. Inhibition of de novo lipogenesis using TVB-3664 or FTY-720 significantly inhibited proliferation, migration, focal adhesion formation and gelatin degradation ability of primary CRC cells. Inhibition of the FASN/SPHK/S1P axis was accompanied by a decrease in activation of p-MET, p-FAK, and p-Paxilin in vitro and in vivo. S1P treatment rescued FASN-mediated inhibition of these proteins suggesting that FASN promotes metastatic properties of CRC cells, in part, through an increase in sphingolipid metabolism.

Conclusion: Upregulation of the FASN/SPHK/S1P axis promotes CRC progression by enhancing cellular proliferation, adhesion and migration. Therefore, this study provides a strong rationale for further investigation of the interconnection of de novo lipogenesis and sphingolipid metabolism that would potentially lead to identification of new therapeutic targets and strategies for CRC.

Citation Format: Naser Jafari, James Drury, Andrew J. Morris, Fredrick O. Onono, Payton D. Stevens, Tianyan Gao, Eun Y. Lee, Heidi L. Weiss, B Mark Evers, Yekaterina Zaytseva. De novo fatty acid synthesis-driven sphingolipid metabolism promotes metastatic potential of colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1437.