Stanniocalcin-1: A novel molecular blood and bone marrow marker for human breast cancer

Purpose: Very few tumor molecular markers have been identified that are highly specific for breast cancer cells when applied to blood and bone marrow (BM). Stanniocalcin (STC)-1 is a recently discovered human gene that has been implicated in cellular calcium homeostasis and resistance to hypoxia and is located on chromosome 8p in a region associated with amplification in breast cancer. We investigated STC-1 mRNA as a potential molecular marker for detection of breast cancer metastasis in the blood and BM. Experimental Design: Using the reverse transcriptase-PCR and electrochemiluminescence detection assay to assess for STC-1 mRNA expression, we evaluated 7 breast cancer cell lines, 34 primary breast cancer tumors, and the BM of 71 patients and the blood of 58 patients with American Joint Committee on Cancer stage 0-IV breast cancer. Results: In this cohort of primarily early-stage breast cancer patients, the detection of STC-1 mRNA in the BM and blood significantly correlated with multiple histopathological prognostic factors, including primary tumor size, number of positive lymph nodes, T stage, M stage, N stage, and overall American Joint Committee on Cancer stage. STC-1 mRNA was not detected in the blood or BM of volunteers without cancer. In situ hybridization studies with a STC-1 antisense RNA probe also confirmed STC-1 mRNA expression in breast cancer cell lines and primary breast tumors. Conclusions: STC-1 is proposed as a novel, specific, and clinically useful molecular marker for detecting occult breast cancer cells in the BM and blood.