SIX1 and breast carcinoma: Aberrant expression of SIX1 was found not only in about half of primary breast cancer, but also even in the majority of metastatic lesions.[56] SIX1 was found to potently promote the metastatic spread of breast cancer MCF-7 cells.[19] Several molecular studies on SIX1 could explain why SIX1 has unfavorable impact on breast cancer patient metastasis.