Clinical significance of cytokeratin 19 and OCT4 as survival markers in non-metastatic and metastatic breast cancer patients

Introduction
Cytokeratin 19 (CK19) is highly expressed in epithelial tumours such as breast cancer (BC). Octamer-binding transcription factor 4 (OCT4), a transcription factor of the POU (Pit-Oct-UNC) family, plays a criti­cal role in the self-renewal and maintenance of pluripotency of embryonic stem cells; therefore, it has been used as a promising CSC marker.

Material and methods
CK19 was assessed in peripheral blood using flow-cytometric analysis while OCT4 was evaluated in breast tissue samples by immunohistochemistry from 70 patients (non-metastatic BC, meta­static BC, and non-malignant breast tumours).

Results
CK19 and OCT4 were significantly associated with BC patients compared to control (p < 0.001). CK19 was detected in 38 patients with BC (62.2%); meanwhile, OCT4 was positive in 37 BC patients (60.6%). CK19 was positively associated with grade (p = 0.002), HER2 (p = 0.009), metastasis (p = 0.026), molecular subtypes and LN (p < 0.001), and stage (p = 0.001) while OCT4 expression was positively associated with BMI (p < 0.023), aggressive molecular subtype (p < 0.019), ER expression (p = 0.025), presence of LN metastases (p < 0.017), and distant metastasis (p < 0.018). A non-significant relation was found between the expression of CK19 and OCT (p = 0.291). The positive expression of CK19 and OCT4 was significantly and inversely associated with both 3-year OS and 3-year PFS.

Conclusions
CK19 and OCT4 are associated with BC, so they can be considered as prognostic and predictive markers for poor OS and PFS in non-metastatic as well as metastatic BC patients.