SEMA3F and cancer: The reduction in the concentration of tumor associated blood vessels was not correlated with the types of semaphorin receptors expressed by the cancer cells since expression of the np2 agonists sema3F and sema3G also reduced the concentration of blood vessels in tumors derived from MDA-MB-231 cells by about 40% (Fig. 6C) even though sema3G did not inhibit the development of tumors from these cells (Fig. 3, G–H).