S1PR4 and breast carcinoma: Pyne and colleagues demonstrated S1PR5 localization in the centrosomes in the nucleus associated with cell division [150], S1PR2 localized to the nucleus preventing cell proliferation [151], and S1P catalyzed by SphK2 bound to S1PR4 to prevent trans-sub-nuclear cellular location of S1PR2 and promoting cell proliferation in estrogen receptor negative MDA-MB-231 breast cancer cells [151].