Introduction: Downstream of tyrosine kinase 7 (DOK-7) is a member of the DOK family, which ha s been associated with the development and progression of various humancancers. Previously, identification of CpG hypermethylation in DOK-7 promoter was identified in breast cancer. Method: DOK-7 mRNA extraction and reverse transcription were performed on fresh frozen breast cancer tissue samples and normal background breast tissue. Transcript levels of expression were analyzed against TNM stage, tumour grade and clinical outcome over a 10-year follow-up period. Results: Levels of DOK-7 expression decreased significantly with increasing TNM stage. Higher DOK-7 expression was correlated with longer disease free and overall survival times. Conclusion: To our knowledge, this is the first study to investigate DOK-7 expression in human breast cancer. We identify a potential DOK-7 tumour suppressor role. DOK-7 as a prognostic biomarker in human breast cancer should be included in future validation studies.
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