The present invention determined that EGFL6 functions as a tumor vascular regulator of ovarian cancer stem cells (CSC). In addition, the present invention determined that a novel EGFL6 blocking antibody was able to restrict cancer cell growth and delay disease recurrence. As such, the present invention provides compositions and methods for inhibiting cancer cell growth, proliferation and/or metastasis. In particular, the present invention provides methods for inhibiting cancer cell growth, proliferation and/or metastasis through administration of a composition comprising an agent capable of inhibiting the function of EGFL6 (e.g., thereby inhibiting related cancer cell growth). In some embodiments, the agent capable of inhibiting the function of EGFL6 is an EGFL6 blocking antibody. The agents and related compositions additionally find use in diagnostic and research settings.