AXL and neoplasm: To test whether R428, a well-characterized Axl-specific small molecule inhibitor, can exhibit the tumor-suppressing activity in the progressing ID8 tumor in vivo, we treated C57BL/6 mice bearing 10-day-established ID8 tumors with escalating doses of R428 and evaluated antitumor effects defined as the overall survival of tumor-bearing animals as previously described [23].