The present invention provides methods compositions and methods for treating a hyperproliferative disease comprising disrupting Cripto/GRP78 complex formation in a hyperproliferative cell. In certain embodiments, an antibody and/or siRNA may be used to inhibit Cripto/GRP78 binding, optionally coupled with other cancer therapies. Also provided are methods for identifying therapeutic compounds which can selectively inhibit Cripto/GRP78 binding.