SPAG5: SPAG5 is a newly amplified gene on Ch17q11.2 in breast cancer and the transcript and protein product of SPAG5 are independent prognostic and predictive biomarkers that may have clinical utility as biomarkers of sensitivity to combination cytotoxic chemotherapy, particularly in estrogen receptor-negative breast cancers [43]. The gene discussed is ESR1; the disease is breast carcinoma.