Provided herein, inter alia, are methods and compositions directed to suppressing tumor cell growth in a subject as well as methods for sensitizing a proliferating cell for treatment with a cytotoxic agent via inhibiting expression of HE4 and one or more immune checkpoint inhibitors (ICIs). Also provided herein are methods for determining whether a subject who has been diagnosed with cancer would benefit from immunotherapy as well as methods for determining whether a subject with cancer is responding to immunotherapy via assessment of levels of HE4 gene and/or protein expression.