The synthetic flavagline FL3 suppresses intestinal tumorigenesis in APC Min/+ mice

Flavaglines are natural plant products shown to have anti‐inflammatory and anti‐cancer effects. FL3 is a synthetic derivative of the flavagline Silvestrol, lacking its structural components linked to causing multidrug resistance and suboptimal absorption and metabolism. Ongoing studies in our lab have shown that FL3 inhibits the Wnt/β‐catenin pathway in colon cancer cell lines. This is especially important since in most colorectal cancer cases aberrant activation of the carcinogenic Wnt pathway occurs via inactivation of the adenomatous polyposis coli ( APC) tumor suppressor gene or activating mutations in CTNNB1 encoding b‐catenin. To assess in vivo action of FL3, we used the APC Min/+ mouse model of spontaneous intestinal tumorigenesis driven by enhanced β‐catenin activation via the loss of heterozygosity mutation in the APC gene. Methods Male and female APC Min/+ mice were administered FL3 (0.1 mg/kg) or vehicle by intraperitoneal injection twice weekly from ages 15 to 20 weeks of age. To assess whether FL3 affected the normal intestine, wild‐type (WT) littermates were injected with FL3 alongside APC Min/+ mice. The entire small intestine and colon were excised and adenoma distribution, size, and number were quantitated using a dissecting microscope. Swiss‐rolled intestines and colons were used for histology and severity of dysplasia or villus/crypt measurements in WT mice. Proliferation was measured by PCNA expression and Ki67 immunostaining in adenomas. Apoptosis was measured by Cleaved Caspase 3 expression and TUNEL immunostaining in adenomas. Results FL3‐treated WT mice exhibited normal intestinal and colon histology, villus/crypt measurements, and no dysplasia. FL3 injection decreased the number and size of adenomas in APC Min/+ mice. TUNEL staining and Cleaved Caspase‐3 expression were increased in adenomas in APC Min/+ mice treated with FL3. FL3 did not alter cell proliferation.. Adenomas in APC Min/+ mice treated with FL3 exhibited increased TUNEL staining and Cleaved Caspase‐3 expression and had no changes in cell proliferation compared to APC Min/+ mice not treated with FL3.. Conclusions FL3 protects against in vivo tumorigenesis driven by aberrant activation of the Wnt/b‐catenin pathway in APC Min/+ mice. FL3 suppressed tumorigenesis by increasing rates of apoptosis without affecting rates of proliferation in neoplasias. This proof‐of‐principle study suggests that FL3 is effective in combating tumorigenesis in a pre‐clinical animal model of aberrant Wnt/b‐catenin pathway activation. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .