For example, the phosphatase domain of RPTP?? or RPTP?? may be deleted resulting in a truncated molecule that is still able to interact with IR. [0054] Expression vectors derived from viruses such as retroviruses, vaccinia virus, adeno-associated virus, herpes viruses, or bovine papilloma virus, may be used for delivery of recombinant RPTP?? or RPTP?? into the targeted cell population.