In order to provide a screening method for a compound capable of suppressing a mechanism of ROR1 by targeting ROR1 and to provide a drug comprising as an active ingredient a compound capable of suppressing the mechanism, it has been found out that suppressing a function of ROR1 makes it possible to suppress receptor tyrosine kinase-mediated pro-survival signaling in a cancer cell. Further, it has been found out that suppressing a function of ROR1 also effectively suppresses growth of cancer cell lines having acquired resistance to inhibitors of receptor tyrosine kinases such as EGFR and MET.
