JAK1 and Familial prostate cancer: To test whether VVD-118313 inhibits JAK1 through engagement of C817, we recombinantly expressed wild-type (WT)-JAK1 and a C817A-JAK1 mutant in the 22Rv1 human prostate cancer cell line, which lacks endogenous JAK1 expression owing to a frameshift mutation in the JAK1 gene25.