Compounds for treatment of cancer

1. A method for treating cancer characterized by expression of an R-spondin fusion in a subject that has been diagnosed as having an R-spondin fusion and has been diagnosed with the cancer being treated, comprising:

administering to the subject a pharmaceutical composition comprising a therapeutically effective amount of a WNT signaling inhibitor, wherein the WNT signaling inhibitor is a small organic molecule, and wherein the WNT signaling inhibitor inhibits porcupine (PORCN).

2. The method of claim 1 , wherein the pharmaceutical composition is for topical application and is an aqueous solution, an ointment, a cream or a gel.

3. The method of claim 1 , wherein the therapeutically effective amount of the WNT signaling inhibitor is about 0.03 to 2.5 mg/kg of body weight at daily dosages.

4. The method of claim 3 , wherein the therapeutically effective amount of the WNT signaling inhibitor is about 0.5 mg to about 100 mg for human.

5. The method of claim 1 , wherein the pharmaceutical composition is administered enterally, orally, parenterally, topically or in a nasal or suppository form.

6. The method of claim 5 , wherein the pharmaceutical composition is a tablet or a gelatin capsule when administered orally.

7. The method of claim 5 , wherein the pharmaceutical composition comprises at least one pharmaceutically acceptable carrier or diluent.

8. The method of claim 1 , wherein the R-spondin fusion comprises a gene fusion between PTPRK and Rspo3 genes.

9. The method of claim 8 , wherein the R-spondin fusion results in expression of R-spondin gene driven by a promoter of the PTPRK gene.

10. The method of claim 8 , wherein the R-spondin fusion comprises a gene fusion between PTPRK exon 1 and Rspo3 exon 2, or between PTPRK exon7 and Rspo3 exon 2.

11. The method of claim 1 , wherein the R-spondin fusion comprises a gene fusion between EIF3E and Rspo2 genes.

12. The method of claim 11 , wherein the R-spondin fusion results in expression of R-spondin gene driven by a promoter of the EIF3E gene.

13. The method of claim 11 , wherein the R-spondin fusion comprises a gene fusion between EIF3E exon 1 and Rspo2 exon 2 or between EIF3E exon 1 and Rspo2 exon 3.

14. The method of claim 1 , wherein the cancer is colorectal cancer, gastric cancer, liver cancer, or esophageal cancer.

15. The method of claim 1 , wherein the R-spondin fusion is detected by an immunoassay using a R-spondin fusion-specific reagent.

16. The method of claim 1 , wherein the R-spondin fusion is detected by sequencing.

17. The method of claim 1 , wherein the R-spondin fusion is detected using a circulating tumor cell.