R01CA266223

ALOX15 Regulation of Colon Cancer Invasiveness via PI3P-Linoleic Acid Metabolism

Colorectal cancer (CRC) is the third leading cause of cancer deaths in the United States. The long-term goal of our research is to develop novel interventions to prevent colorectal carcinogenesis (CRC). CRC invasiveness, a critical adverse step during CRC progression, requires a combination of certain genetic mutations (e.g. APC, KRAS, and TRP53 mutations), which are the key events to drive CRC. However, CRC progression also requires additional factors which increase aberrant beta-catenin (B-catenin) activation above levels induced by APC/B-catenin mutations.

Linoleic acid (LA), the most commonly consumed omega-6 polyunsaturated fatty acid in humans, increases both chemically (AOM)- and APC mutation-induced CRC tumorigenesis in mice. Nonetheless, human studies have been inconclusive regarding the impact of dietary LA on CRC. Determination of LA's role in CRC is important because American diets are enriched with LA while expression of the main metabolizing enzyme for LA, 15-lipoxygenase-1 (ALOX15), is lost in human CRC.

Recently, we found that:
1) High dietary levels of LA promoted CRC by increasing phosphatidylinositol 3-phosphate (PI3P) containing LA (PI3P_LA), which increases LRP5 membranous recycling and subsequently B-catenin activation.
2) ALOX15-induced conversion of PI3P_LA to PI3P_13-HODE suppresses LRP5 membranous recycling, B-catenin activation, CRC stemness, and LA promotion of CRC, especially formation of large tumors associated with CRC invasiveness.
3) ALOX15 loss of function (LOF) promotes large CRC tumor formation by azoxymethane in 12/15LOX-KO-12LOX (ALOX15-LOF) mice.

Whether loss of ALOX15 expression promotes CRC invasiveness remains unknown. Our preliminary data show that ALOX15-LOF mice increased CRC invasiveness and targeted APC mutation into LGR5+ colorectal stem cells induced CRC in the mice, which was blocked by transgenic ALOX15 expression. We therefore hypothesize that ALOX15 loss of function promotes CRC invasiveness by increasing PI3P_LA levels, which enhances LRP5 membranous recycling, thus potentiating Wnt/B-catenin signaling and subsequently stemness.

Aim 1 will determine the effects of ALOX15 gain of function and ALOX15 LOF on LRP5, B-catenin activation, CRC stemness, and invasiveness using CRC mouse models in which CRC invasiveness is promoted by either a combination of APC, KRASG12D, and TRP53R172H mutations or TRP53R172H mutation with AOM-induced B-catenin and KRAS mutations.

Aim 2 will determine the effects of ALOX15 LOF on PI3P-LA, LRP5, B-catenin activation, stemness, and invasiveness in human CRCs and examine the effects of ALOX15 re-expression via lentivirus Tet-On inducible system in human CRC-derived organoids on invasiveness in vitro and in vivo studies.

The proposed studies are expected to provide important mechanistic insights into whether colonic ALOX15 expression as a host factor affects CRC invasiveness risk, especially with high dietary LA intake. This gained knowledge could inform subjects with colorectal ALOX15 LOF to avoid high LA intake and spur development of interventions to target ALOX15 for re-expression to prevent invasive CRC.

Regents Of The University Of Michigan

NOT APPLICABLE

93.393 - Cancer Cause and Prevention Research

National Cancer Institute (NCI) [HHS - NIH]

Ann Arbor, Michigan 481091276 United States

Single Zip Code

NIH Research Project Grant (Parent R01 Clinical Trial Not Allowed) (PA-20-185)

Amendment Since initial award the End Date has been extended from 12/31/26 to 04/30/27 and the total obligations have increased 385% from $665,973 to $3,227,957.