BRK/PTK6 in breast cancer: prognostic and therapeutic significance

Breast Tumour Kinase (BRK/PTK6) is a non-receptor tyrosine kinase that has attracted growing interest in breast cancer research due to its association with tumour progression, aggressive disease behaviour, therapy resistance, and prognosis. Although BRK is often discussed in relation to its expression in malignant breast tissues, its significance extends beyond expression level alone. Its activation, subcellular localisation, kinase-dependent signalling, and non-catalytic interactions all contribute to its influence on tumour behaviour. Across breast cancer models, BRK has been associated with disease progression, resistance-related signalling, and reduced treatment response, supporting its relevance as both a prognostic marker and a therapeutic target. Its role in breast cancer is not confined to a single pathway or mechanism, but reflects the combined contribution of kinase activity, functional interactions, activation status, localisation, and tumour subtype. This review examines the prognostic and therapeutic significance of BRK/PTK6 in breast cancer, with an emphasis on its roles in disease progression and therapy resistance, its potential as a biomarker, and emerging BRK-directed treatment strategies. Summary: This review explores the role of BRK/PTK6 in driving breast cancer progression and treatment resistance, emphasising its potential as a prognostic biomarker and discussing challenges in targeting BRK to improve breast cancer therapies.