DKK1 and breast cancer: On the other hand, DKK1 has also been identified as a potential prognostic and diagnostic marker for cohorts of breast cancer patients with poor prognosis [23] and increased circulating levels of DKK1 has been associated with the presence of bone metastases in patients with breast cancer [25] We note that 13 out of the 22 analysed PETs prominently expressed DKK1.