ISG15 and ovarian cancer: Since ISG15 modifies proteins through a process called ISGylation [17], which involves three cascade enzymes: An E1 enzyme (UBE1L), an E2 enzyme (UbcH8), and one of several E3 ligases to catalyze ISG15 conjugation of a specific protein, we hypothesized that increased ISGylation of proteins targeted by ISG15 in cells may mediate the suppressor effect of ISG15 in ovarian cancer progression.